阅读说明：本技术 脱木质素的木材、其制造方法及用途 (Delignified wood, method for the production thereof and use thereof ) 是由 胡良兵 T·李 S·何 C·陈 宋建伟 于 2018-09-14 设计创作，主要内容包括：通过从天然木材中去除基本上所有的木质素形成了一种脱木质素的木材。所得的脱木质素的木材保留了所述天然木材的基于纤维素的腔,其中所述纤维素微纤维的纳米纤维基本上沿着同一方向取向。所述脱木质素的木材的独特的微结构和组成可以提供有利的热隔离和机械性质,以及本文所述的其他优点。可以通过对所述脱木质素的木材进行压制或致密化来调整所述脱木质素的木材的热性质和机械性质,其中增强的致密化产生了改善的强度和热导率。所述脱木质素的木材的化学组成还提供了独特的光学性质,所述独特的光学性质可在太阳照射下实现被动冷却。(A delignified wood is formed by removing substantially all of the lignin from the natural wood. The resulting delignified wood retains the cellulose-based cavities of the natural wood, wherein the nanofibers of the cellulose microfibers are oriented substantially in the same direction. The unique microstructure and composition of the delignified wood can provide advantageous thermal insulation and mechanical properties, as well as other advantages described herein. The thermal and mechanical properties of the delignified wood can be adjusted by pressing or densifying the delignified wood, wherein the enhanced densification results in improved strength and thermal conductivity. The chemical composition of the delignified wood also provides unique optical properties that allow passive cooling under solar irradiation.)

1. A structure, the structure comprising:

a first natural wood piece that has been chemically treated to remove lignin from the natural wood while substantially preserving the structure of the cellulose-based cavities of the natural wood,

wherein at least 90% of the lignin in the natural wood has been removed by the chemical treatment.

2. The structure of claim 1, wherein the lignin in the first piece is less than 5 wt%.

3. The structure of claim 2, wherein the lignin in the first piece is less than or equal to 1 wt%.

4. The structure of claim 1, wherein the first and second electrodes are arranged in a single plane,

wherein the first piece has an axial thermal conductivity in the direction of extension of the cavity and a transverse thermal conductivity in a direction perpendicular to the direction of extension of the cavity, and

the axial thermal conductivity is greater than the transverse thermal conductivity.

5. The structure of claim 4, wherein the axial thermal conductivity is at least two times greater than the lateral thermal conductivity.

6. The structure of claim 5, wherein the axial thermal conductivity is at least five times greater than the lateral thermal conductivity.

7. The structure of claim 6, wherein the axial thermal conductivity is at least ten times greater than the lateral thermal conductivity.

8. The structure of claim 4, wherein the lateral thermal conductivity is less than 0.2W/m-K.

9. The structure of claim 8, wherein the lateral thermal conductivity is less than 0.1W/m-K.

10. The structure of claim 9, wherein the lateral thermal conductivity is less than 0.05W/m-K.

11. The structure of claim 1, wherein the first member has an emissivity of at least 0.8 over a wavelength range of 8 μ ι η to 13 μ ι η.

12. The structure of claim 11, wherein the emissivity is at least 0.9 over a wavelength range of 8 μ ι η to 13 μ ι η.

13. The structure of claim 1, wherein the first piece has an absorbance of less than or equal to 10% over a wavelength range of 400nm to 1100 nm.

14. The structure of claim 13, wherein the absorbance is less than or equal to 8%.

15. The structure of claim 1 wherein a first emissivity of said first member in the wavelength range of 400-1100nm is less than a second emissivity of said first member in the wavelength range of 8-13 μm.

16. The structure of claim 15, wherein the second emissivity is at least 10 times the first emissivity.

17. The structure of claim 15, wherein the second emissivity is at least 0.8 and the first emissivity is less than or equal to 0.1.

18. The structure according to claim 1, wherein the cellulose nanofibres in the first piece are oriented substantially along the extension direction of the cavity.

19. The structure of claim 18, wherein the first piece has nanopores between the oriented cellulose nanofibers.

20. The structure of claim 1, wherein the interior volume of the cellulose-based cavity of the first piece is open or unobstructed.

21. The structure according to claim 1, wherein the first piece has increased flexibility compared to the natural wood before the chemical treatment.

22. The structure according to claim 1, wherein the bending radius of the first piece is at least two times smaller than the bending radius of the natural wood before the chemical treatment.

23. The structure of claim 1, wherein the cavity extends in a direction perpendicular to a thickness of the first piece.

24. The structure of claim 1, wherein the cavity extends in a thickness direction of the first piece.

25. A structure according to claim 23 or claim 24, wherein the first piece has a dimension in a direction perpendicular to the thickness direction that is greater than the thickness of the first piece in the thickness direction.

26. The structure of claim 1, wherein the thickness of the first piece is less than or equal to 1 mm.

27. A structure according to claim 1, wherein the chemically treated wood of the first piece has been pressed in a first direction crosswise to the direction of extension of the cavities, such that the cavities are at least partially collapsed.

28. A structure according to claim 27, wherein the thickness of the first piece in the first direction is reduced by no more than 40% compared to the thickness of the natural wood.

29. The structure of claim 28, wherein the thickness of the first piece is reduced by no more than 20% compared to the thickness of the natural wood.

30. A structure according to claim 27, wherein the thickness of the first piece in the first direction is reduced by at least 40% compared to the thickness of the natural wood.

31. The structure of claim 30, wherein the thickness of the first piece is reduced by at least 80% compared to the thickness of the natural wood.

32. The structure according to claim 29, wherein said first piece has an increased density compared to said natural wood prior to said chemical treatment.

33. The structure according to claim 32, wherein the density of the first piece is at least two times greater than the density of the natural wood prior to the chemical treatment.

34. The structure of claim 29, wherein the first piece has a surface roughness of 10nm or less.

35. The structure according to claim 1, wherein the mechanical properties of the first piece are improved compared to the mechanical properties of the natural wood before the chemical treatment.

36. The structure of claim 35, wherein the first piece has a specific tensile strength of at least 200MPa-cm³/g。

37. The structure of claim 36, wherein the first piece has a specific tensile strength of at least 300MPa-cm³/g。

38. The structure of claim 37, wherein the first piece has a specific tensile strength of at least 330MPa-cm³/g。

39. The structure of claim 1, further comprising:

a second natural wood piece that has been chemically treated to remove lignin from the natural wood while substantially preserving the structure of the cellulose-based cavities of the natural wood, at least 90% of the lignin in the natural wood having been removed by the chemical treatment,

wherein the first and second pieces are coupled to each other along opposing surfaces, and

the direction of extension of the cavity of the first part intersects the direction of extension of the cavity of the second part.

40. A structure according to claim 39, wherein the direction of extension of the cavity of the first piece is orthogonal to the direction of extension of the cavity of the second piece.

41. The structure of claim 39, wherein the first piece and the second piece are coupled to each other by at least one of hydrogen bonding, glue, and epoxy.

42. The structure of claim 39, wherein each of the first and second pieces is formed as a plate, a block, a bar, a hollow shape, a film having a thickness of less than 200 μm, a wood chip, or a wood shaving.

43. A structure according to claim 39, wherein the chemically treated natural wood of the first and second pieces has been pressed in a direction crosswise to the respective direction of extension of the cavities therein, such that the cavities are at least partially collapsed.

44. The structure of claim 1, wherein the first piece consists essentially of the chemically-treated natural wood.

45. The structure of claim 1, wherein the first member is hydrophobic.

46. The structure according to claim 45, wherein the first piece exhibits a static contact angle of at least 90 °, or a dynamic contact angle of less than 10 °.

47. The structure of claim 45, wherein the first piece has been chemically treated to be hydrophobic, and the chemical treatment comprises at least one of: epoxy resin, silicone oil, polyurethane, paraffin emulsion, acetic anhydride, Octadecyltrichlorosilane (OTS), 1H,2H, 2H-perfluorodecyltriethoxysilane, fluororesin, Polydimethylsiloxane (PDMS), Methacryloxymethyltrimethylsilane (MSi), polyhedral oligomeric silsesquioxane (POSS), Potassium Methylsiliconate (PMS), dodecyl (trimethoxy) silane (DTMS), hexamethyldisiloxane, dimethyldiethoxysilane, tetraethoxysilane, methyltrichlorosilane, ethyltrimethoxysilane, methyltriethoxysilane, trimethylchlorosilane, phenyltrimethoxysilane, phenyltriethoxysilane, propyltrimethoxysilane, polymethyl methacrylate, polydiallyldimethylammonium chloride (polyDADMAC), 3- (trimethoxysilyl) propyl Methacrylate (MPS), Hydrophobic stearic acid, amphiphilic fluorinated triblock azide copolymer, polyvinylidene fluoride and fluorosilane, n-dodecyl trimethoxysilane, and sodium dodecyl sulfate.

48. The structure of claim 1, wherein the first piece has been chemically treated to be weather resistant or salt water resistant.

49. The structure of claim 48, wherein the chemical treatment for weathering or salt water resistance comprises at least one of: copper dimethyldithiocarbamate (CDDC), ammoniated quaternary Ammonium Copper (ACQ), Copper Chromide Arsenate (CCA), Ammoniated Copper Zinc Arsenate (ACZA), copper naphthenate, copper acid chromate, copper citrate, copper azole, copper 8-hydroxyquinoline, pentachlorophenol, zinc naphthenate, copper naphthenate, creosote, titanium dioxide, propiconazole, tebuconazole, cyproconazole, boric acid, borax, organic Iodide (IPBC), and Na₂B₈O₁₃·4H₂O。

50. The structure of claim 1, further comprising a coating on one or more outer surfaces of the first piece.

51. The structure of claim 50, wherein the coating comprises an oil-based coating, a hydrophobic coating, a polymeric coating, or a fire resistant coating.

52. The structure of claim 51, wherein the refractory coating comprises at least one of: boron nitride, montmorillonite, hydrotalcite, silicon dioxide (SiO)₂) Sodium silicate, calcium carbonate (CaCO)₃) Aluminum hydroxide (Al (OH)₃) Magnesium hydroxide (Mg (OH)₂) Magnesium carbonate (MgCO)₃) Aluminum sulfate, ferric sulfate, zinc borate, boric acid, borax, triphenyl phosphate (TPP), melamine, polyurethane, ammonium polyphosphate, phosphate ester, phosphorousAcid esters, ammonium phosphate, ammonium sulfate, phosphonate esters, diammonium phosphate (DAP), monoammonium phosphate (MAP), guanylurea phosphate (GUP), guanidine dihydrogen phosphate, and antimony pentoxide.

53. The structure of claim 1, wherein the first piece is white.

54. The structure of claim 1, wherein the first piece has been dyed a color other than white.

55. The structure of claim 1, further comprising a heat source in thermal communication with the first piece, wherein the first piece is exposed to radiate heat from the heat source to the sky.

56. The structure of claim 55, wherein an exposed surface of the first piece is substantially parallel to a direction of extension of the cavity.

57. The structure of claim 1, further comprising an electrical component formed over a surface of the first piece.

58. The structure of claim 57 wherein the electrical component comprises at least one of a transistor, a capacitor, a resistor, and an inductor.

59. A structure formed by removing at least 90% of lignin from a natural wood piece while substantially retaining a cellulose-based cavity.

60. A structure formed by removing at least 90% of lignin from a natural wood piece while substantially retaining a cellulose-based cavity, and then pressing to at least partially collapse the cavity.

61. A structure according to claim 60, wherein the thickness of the piece after pressing is reduced by at least 40% compared to the thickness of the natural wood, or by at least 80% compared to the thickness of the natural wood.

62. The structure of claim 60, wherein the thickness of the piece after pressing is reduced by no more than 40% compared to the thickness of the natural wood, or by no more than 20% compared to the thickness of the natural wood.

63. The structure of any one of claims 59-62, wherein the piece has less than or equal to 5 wt% lignin therein, or less than or equal to 1 wt% lignin therein.

64. The structure of any one of claims 59-63, wherein the piece has anisotropic thermal conductivity.

65. The structure of any one of claims 59-64, wherein the piece absorbs less than or equal to 10% of solar radiation and has an emission greater than or equal to 90% in the atmospheric transmission window.

66. The structure of any one of claims 59-65, wherein the piece is hydrophobic.

67. The structure of any one of claims 59 to 66, wherein the piece is joined together with another natural wood piece from which at least 90% of the lignin has been removed to form a laminate.

68. The structure of any one of claims 59-67, wherein the pieces are substantially white.

69. A method comprising removing at least 90% of lignin from a natural wood piece while substantially preserving a cellulose-based cavity of the natural wood, thereby producing a delignified wood piece.

70. The method of claim 69, wherein the delignified wood is substantially white.

71. The method according to claim 69, wherein the removing comprises immersing the natural wood piece in a chemical solution containing at least one of: NaOH and Na₂S、NaHSO₃、SO₂,、H₂O、Na₂SO₃Anthraquinone (AQ), Na₂S_n(wherein n is an integer), CH₃OH、C₂H₅OH、C₄H₉OH、HCOOH、NH₃、p-TsOH、NH₃-H₂O、H₂O₂、NaClO、NaClO₂、CH₃COOH (acetic acid), ClO₂And Cl₂。

72. The method according to claim 69, wherein the removing includes immersing the natural wood piece in a first chemical solution and then in a second chemical solution.

73. The method of claim 72, wherein the first chemical solution comprises NaOH and Na₂SO₃And the second chemical solution comprises H₂O₂。

74. The method of claim 69, further comprising drying the delignified wood piece by freeze drying or critical point drying after the removing such that the cellulose-based cavity remains open or unobstructed in a cross-sectional view.

75. The method of claim 69, further comprising, after said removing, rinsing said delignified wood to remove residual chemicals from said removing.

76. The method of claim 75, wherein the solution for the rinsing comprises at least one of ethanol and Deionized (DI) water.

77. The method of claim 75, further comprising drying the delignified piece of wood after the rinsing.

78. The method of claim 75, further comprising exposing the delignified wood to a relative humidity of 90% for a first period of time after the rinsing.

79. The method of claim 69, further comprising pressing the delignified wood.

80. The method according to claim 79, wherein the pressing reduces the thickness of the wood by between 0% and 40%, or between 0% and 20%, inclusive.

81. The method according to claim 79, wherein the pressing reduces the thickness of the wood by at least 40%.

82. The method according to claim 79, wherein the pressing reduces the thickness of the wood by at least 80%.

83. The method of claim 79, wherein said pressing is performed at a temperature of 20-120 ℃ and a pressure of 0.5-10 MPa.

84. The method of claim 79, wherein a microfiltration membrane or filter paper is disposed on the surface of the delignified wood prior to or during the pressing.

85. The method of claim 79, further comprising subjecting the wood to a hydrophobic treatment before or after the pressing.

86. The method of claim 85, wherein the hydrophobic treatment comprises at least one of: epoxy resin, silicone oil, polyurethane, paraffin emulsion, acetic anhydride, Octadecyltrichlorosilane (OTS), 1H,2H, 2H-perfluorodecyltriethoxysilane, fluororesin, Polydimethylsiloxane (PDMS), Methacryloxymethyltrimethylsilane (MSi), polyhedral oligomeric silsesquioxane (POSS), Potassium Methylsiliconate (PMS), dodecyl (trimethoxy) silane (DTMS), hexamethyldisiloxane, dimethyldiethoxysilane, tetraethoxysilane, methyltrichlorosilane, ethyltrimethoxysilane, methyltriethoxysilane, trimethylchlorosilane, phenyltrimethoxysilane, phenyltriethoxysilane, propyltrimethoxysilane, polymethyl methacrylate, polydiallyldimethylammonium chloride (polyDADMAC), 3- (trimethoxysilyl) propyl Methacrylate (MPS), Hydrophobic stearic acid, amphiphilic fluorinated triblock azide copolymer, polyvinylidene fluoride and fluorosilane, n-dodecyl trimethoxysilane, and sodium dodecyl sulfate.

87. The method of claim 86, wherein said hydrophobic treatment is performed prior to said compressing and comprises 1H,1H,2H, 2H-perfluorodecyltriethoxysilane.

88. The method of claim 79, wherein the pressing is performed in a direction that intersects the direction of extension of the cellulose-based cavities.

89. The method of claim 79, wherein after the pressing, the surface roughness of the delignified wood is 10nm or less.

90. The method of claim 69, further comprising at least one of:

dyeing the delignified wood to a color other than white;

chemically treating the delignified wood to render it weather resistant or salt water resistant; and

coating the surface of the delignified wood.

91. The method of claim 90, wherein the chemical treatment for weathering or salt water resistance comprises at least one of: copper dimethyldithiocarbamate (CDDC), ammoniated quaternary Ammonium Copper (ACQ), Copper Chromide Arsenate (CCA), Ammoniated Copper Zinc Arsenate (ACZA), copper naphthenate, copper acid chromate, copper citrate, copper azole, copper 8-hydroxyquinoline, pentachlorophenol, zinc naphthenate, copper naphthenate, creosote, titanium dioxide, propiconazole, tebuconazole, cyproconazole, boric acid, borax, organic Iodide (IPBC), and Na₂B₈O₁₃·4H₂O。

92. The method of claim 90, wherein the coating comprises an oil-based coating, a hydrophobic coating, a polymeric coating, or a fire-resistant coating, and

the refractory coating comprises at least one of the following: boron nitride, montmorillonite, hydrotalcite, silicon dioxide (SiO)₂) Sodium silicate, calcium carbonate (CaCO)₃) Aluminum hydroxide (Al (OH)₃) Magnesium hydroxide (Mg (OH)₂) Magnesium carbonate (MgCO)₃) Aluminum sulfate, ferric sulfate, zinc borate, boric acid, borax, triphenyl phosphate (TPP), melamine, polyurethane, ammonium polyphosphate, phosphate ester, phosphite, ammonium phosphate, ammonium sulfate, phosphonate, diammonium phosphate (DAP), monoammonium phosphate (MAP), guanylurea phosphate (GUP), guanidine dihydrogen phosphate, and antimony pentoxide.

93. The method of claim 69, further comprising positioning the delignified wood piece so that a surface thereof radiates heat skyward.

94. The method of claim 93, wherein the surface is substantially parallel to a direction of extension of the cavity.

95. The method of claim 69, further comprising forming the delignified wood piece into a building material, a packaging material, or other structural material.

96. The method of claim 69, further comprising forming one or more electrical components on a surface of the delignified wood piece.

97. The method of claim 69, further comprising using the delignified wood piece to radiate energy to cool a structure or environment.

98. The method of claim 97, wherein the cooling is passive cooling.

99. The method as claimed in claim 97 wherein the delignified wood piece has a first emissivity in the wavelength range of 400-1100nm and a second emissivity in the wavelength range of 8-13 μm, and the first emissivity is less than the second emissivity.

100. The method of claim 99, wherein the second emissivity is at least 10 times the first emissivity.

101. The method of claim 100, wherein the second emissivity is at least 0.8 and the first emissivity is less than or equal to 0.1.

102. The method of claim 97, wherein the delignified wood piece radiates more energy than it absorbs.

103. The method of claim 69, wherein the thermal conductivity of the delignified piece of wood is anisotropic.

104. The method of claim 103, wherein the thermal conductivity of the delignified piece of wood in a direction parallel to the exposed surface of the delignified wood is greater than the thermal conductivity of the delignified piece of wood in a direction perpendicular to the exposed surface.

105. The method of claim 69, further comprising:

removing at least 90% of the lignin from another piece of natural wood while substantially retaining the cellulose-based cavities of the natural wood, thereby producing another delignified piece of wood, and

coupling a surface of the delignified wood piece with a surface of the other delignified wood piece.

106. The method of claim 105, wherein the direction of extension of the cavity of the delignified wood piece intersects the direction of extension of the cavity of the other delignified wood piece.

107. The method of claim 105, wherein the delignified wood piece and the other delignified wood piece are coupled to each other by at least one of hydrogen bonding, glue and epoxy.

108. The method of claim 105, further comprising pressing the delignified wood piece and the further delignified wood piece in a direction across the respective directions of extension of the cavities therein, before or after the coupling, such that the cavities are at least partially collapsed.

109. The structure of any one of claims 1-24 and 26-62, or the method of any one of claims 69-108, wherein the natural wood comprises hardwood, softwood, or bamboo.

110. The structure of any one of claims 1-24 and 26-62, or the method of any one of claims 69-108, wherein the natural wood comprises basswood, oak, aspen, ash, alder, aspen, balsa, beech, birch, cherry, white walnut, chestnut, sandalwood, elm, hickory, maple, oak, rosewood, plum, walnut, willow, yellow poplar, larch, fir, cedar, douglas fir, hemlock, larch, pine, redwood, spruce, larch, juniper, or yew.

111. An active or passive cooling device comprising a structure according to any of claims 1-24 and 26-62 or a structure formed by a method according to any of claims 69-108.

112. An isolation material comprising a structure according to any of claims 1-24 and 26-62 or a structure formed by a method according to any of claims 69-108.

113. An electronic device, the electronic device comprising:

the structure of any one of claims 1-24 and 26-62 or the structure formed by the method of any one of claims 69-108, and

at least one electrical component formed over a surface of the structure.

114. The electronic device of claim 113, wherein the electronic device is configured as a display panel.

115. A packaging material comprising a structure according to any one of claims 1-24 and 26-62 or a structure formed by a method according to any one of claims 69-108.

116. A building material comprising a structure according to any one of claims 1-24 and 26-62 or a structure formed by a method according to any one of claims 69-108.

117. The building material of claim 116, wherein the building material is configured as an exterior surface of a building.

118. The building material of claim 117, wherein the exterior surface is at least one of a roof and a wall panel of the building.

119. A material, the material comprising:

the structure of any one of claims 1 to 24;

the structure of any one of claims 26 to 62; or

A structure formed by the method of any one of claims 69-108.

120. The material of claim 119, wherein the material is formed as an interior or exterior component of an automobile, train, truck, airplane, boat, ship, or any other vehicle, or vehicle.

121. The material of claim 119, wherein the material is formed as part of a container, box, or shipping crate.

122. The material of claim 119, wherein the material is formed as an interior or exterior component of a warehouse, a factory, an office building, a barn, a house, or any other building or structure.

123. The material of claim 119, wherein the material is formed as part of a display, an ornament, a window frame, a picture frame, a door or door frame, a table, a desk, a chair, a cabinet, a wardrobe, a bed, or any other piece of furniture or home furnishing.

124. The material of claim 119, wherein the material forms a portion of a bridge, dock, deck, or platform.

125. The material of claim 119, wherein the material forms part of a musical instrument.

126. The material of claim 119, wherein the material forms part of a protective enclosure, blast shield, or other protective device.

127. The material of claim 119, wherein the material forms a portion of a tool, athletic device, or athletic article.

Technical Field

The present disclosure relates generally to materials formed from natural wood, and more particularly to wood from which substantially all lignin has been removed (i.e., delignified), as well as structures and devices comprising such delignified wood.

Disclosure of Invention

Embodiments of the disclosed subject matter provide a wood formed by removing substantially all lignin from natural wood. The resulting delignified wood retains the cellulose-based cavities of the natural wood, wherein the nanofibers of the cellulose microfibers are oriented in substantially the same direction. The unique microstructure and composition of delignified wood can provide advantageous thermal and mechanical properties, as well as other advantages described herein.

Delignified wood can be further processed to tailor the properties of the wood to a particular application. For example, in thermal insulation applications, delignified wood may be subjected to freeze drying or critical point drying to maintain the substantially porous nature of the cellulose microstructure, which may further enhance the insulation properties of the delignified wood.

In other applications, such as where heat transfer is desirable, delignified wood may be pressed such that the cavities collapse (i.e., densify). Thus, the cell walls forming the lumen become entangled and hydrogen bonds are formed between adjacent nanofibers. In addition to higher thermal conductivity, the resulting densified delignified wood may also have increased strength and toughness, and exhibit improvements in other mechanical properties.

In some embodiments, it may be desirable to partially compress the delignified wood such that the cavities are only partially collapsed in order to tailor the resulting thermal and mechanical properties to a particular application, for example to provide a balance with improved thermal insulation and improved strength.

By further modifying, manipulating or machining the resulting wood (delignified, densified and delignified, or partially densified and delignified), the resulting wood can be adapted to various applications. Such applications include, but are not limited to, electronic devices; isolating; radiation cooling; and construction, packaging or construction materials.

In one or more embodiments, a structure includes a first natural wood piece that has been chemically treated to remove lignin therein while substantially retaining the structure of the cellulose-based cavities of the natural wood. At least 90% of the lignin in natural wood has been removed by chemical treatment.

In one or more embodiments, the structure is formed by removing at least 90% of the lignin from the natural wood piece while substantially retaining the cellulose-based cavities.

In one or more embodiments, the structure is formed by removing at least 90% of the lignin from the natural wood piece while substantially retaining the cellulose-based cavities, and then pressing to at least partially collapse the cavities.

In one or more embodiments, a method includes removing at least 90% of lignin from a natural wood piece while substantially retaining cellulose-based cavities of the natural wood, thereby producing a delignified wood piece.

Objects and advantages of embodiments of the disclosed subject matter will become apparent from the following description when considered in conjunction with the accompanying drawings.

Drawings

Embodiments will hereinafter be described with reference to the accompanying drawings, which are not necessarily drawn to scale. Where applicable, some elements may be simplified or otherwise not shown to help illustrate and describe the underlying features. Like reference symbols in the various drawings indicate like elements.

Fig. 1 is an exemplary process flow diagram for making and using delignified wood in accordance with one or more embodiments of the disclosed subject matter.

Fig. 2A is a simplified illustration of a natural wood piece prior to any lignin removal.

Fig. 2B is a simplified schematic representation of cellulose fibrils in natural wood prior to any lignin removal.

Fig. 2C is a Scanning Electron Microscope (SEM) image of the top surface of the natural wood in a direction perpendicular to the direction of tree growth, prior to any lignin removal.

Fig. 2D is an SEM image of a longitudinal section of natural wood in a direction parallel to the direction of tree growth, prior to any lignin removal.

Figure 2E is a close-up SEM image of cellulose fibrils in natural wood prior to any lignin removal.

Fig. 3A is a simplified illustration of a wood piece after delignification according to one or more embodiments of the disclosed subject matter.

Fig. 3B is a simplified schematic representation of cellulose fibrils in wood after delignification according to one or more embodiments of the disclosed subject matter.

Fig. 3C is an SEM image of a top surface of a wood after delignification in a direction perpendicular to a direction of tree growth, according to one or more embodiments of the disclosed subject matter.

Fig. 3D is an SEM image of a longitudinal section of wood in a direction parallel to the direction of tree growth after delignification according to one or more embodiments of the disclosed subject matter.

Fig. 3E is an enlarged SEM image of region 310 of fig. 3D, according to one or more embodiments of the disclosed subject matter.

Fig. 3F-3G are magnified SEM images and further magnified SEM images, respectively, of cellulose fibrils of wood after delignification according to one or more embodiments of the disclosed subject matter.

Fig. 3H is an SEM image of oriented channels in a cross-section of wood after delignification according to one or more embodiments of the disclosed subject matter.

Fig. 3I is an enlarged SEM image of region 312 in fig. 3H.

Fig. 4A is a simplified illustration of delignified wood having anisotropic thermal conductivity according to one or more embodiments of the disclosed subject matter.

Fig. 4B is a simplified illustration of delignified wood in a flexed state according to one or more embodiments of the disclosed subject matter.

Fig. 4C is a simplified illustration of delignified wood bent to form a conduit according to one or more embodiments of the disclosed subject matter.

Fig. 5A is a simplified schematic representation of densified delignified wood according to one or more embodiments of the disclosed subject matter.

Fig. 5B is a simplified schematic representation of densified delignified wood according to one or more embodiments of the disclosed subject matter.

Fig. 5C is an isometric view of densified delignified wood according to one or more embodiments of the disclosed subject matter, wherein the inset shows a close-up view of the wood and the chemical composition of the wood surface.

Fig. 5D is an SEM image of densified delignified wood taken in the R-L plane according to one or more embodiments of the disclosed subject matter.

Fig. 5E is an enlarged SEM image of region 504 in fig. 5D.

Fig. 5F is an enlarged SEM image of region 506 in fig. 5E.

Fig. 6A is a simplified schematic diagram of an exemplary method for forming densified delignified wood according to one or more embodiments of the disclosed subject matter.

Fig. 6B is a simplified schematic diagram of an exemplary method for forming densified delignified wood using rotary cutting according to one or more embodiments of the disclosed subject matter.

Fig. 6C is a simplified schematic illustration of an exemplary method for forming densified delignified wood from a hollow cylinder of natural wood, according to one or more embodiments of the disclosed subject matter.

Fig. 6D is a simplified schematic illustration of an exemplary method for forming densified delignified wood from a solid cylinder of natural wood according to one or more embodiments of the disclosed subject matter.

Fig. 6E is a simplified schematic of another exemplary method for forming densified delignified wood from a solid cylinder of natural wood according to one or more embodiments of the disclosed subject matter.

Fig. 7A is a graph of stress versus strain for natural wood and densified delignified wood according to one or more embodiments of the disclosed subject matter.

Fig. 7B is a graph of strength versus toughness for natural wood and densified delignified wood according to one or more embodiments of the disclosed subject matter.

Fig. 7C is a graph of scratch hardness of natural wood and densified delignified wood according to one or more embodiments of the disclosed subject matter.

Fig. 8A is a simplified illustration of an exemplary delignified wood block for insulation according to one or more embodiments of the disclosed subject matter.

Fig. 8B-8C are graphs of axial and transverse (radial) thermal conductivity of delignified wood and natural wood, respectively, according to one or more embodiments of the disclosed subject matter.

Fig. 8D-8E are graphs of axial and transverse (radial) thermal conductivities, respectively, of natural wood and densified delignified wood according to one or more embodiments of the disclosed subject matter.

Fig. 9A is a graph of reflectance versus wavelength for natural wood and delignified wood according to one or more embodiments of the disclosed subject matter.

Fig. 9B is a temperature profile of natural wood and delignified wood when subjected to point irradiation with a laser according to one or more embodiments of the disclosed subject matter.

Fig. 9C is a graph of reflectance versus wavelength for natural wood and densified delignified wood according to one or more embodiments of the disclosed subject matter.

Fig. 9D is a graph of absorbance versus wavelength for natural wood and densified delignified wood according to one or more embodiments of the disclosed subject matter.

Fig. 10A is a simplified illustration of a building including delignified wood as a structural component according to one or more embodiments of the disclosed subject matter.

Fig. 10B is a simplified illustration of a cross-section of a structural material comprising one or more pieces of delignified wood according to one or more embodiments of the disclosed subject matter.

Fig. 11 is a simplified illustration of a cooling arrangement using delignified wood according to one or more embodiments of the disclosed subject matter.

Fig. 12A is a graph of infrared emissivity of densified delignified wood according to one or more embodiments of the disclosed subject matter.

Fig. 12B is a graph of a polar distribution of average emissivity of densified delignified wood across an atmospheric transmission window according to one or more embodiments of the disclosed subject matter.

Fig. 13A is a simplified illustration of a test setup for a passive cooling experiment employing natural wood and densified delignified wood, according to one or more embodiments of the disclosed subject matter.

Fig. 13B-13C are temperature profiles of natural wood and densified delignified wood during nighttime and daytime, respectively, in the setup of fig. 13A.

Fig. 14 is a simplified illustration of an electronic device comprising delignified wood according to one or more embodiments of the disclosed subject matter.

Fig. 15 is a simplified illustration of delignified wood having anisotropic thermal conductivity and a different cavity orientation than the delignified wood of fig. 4A, according to one or more embodiments of the disclosed subject matter.

Fig. 16 is a simplified illustration of delignified wood subjected to densification and having a different cavity and/or pressing orientation than the delignified wood of fig. 5A, according to one or more embodiments of the disclosed subject matter.

Fig. 17A is a simplified schematic illustration of an arrangement of pieces of delignified wood for forming a laminate structure, according to one or more embodiments of the disclosed subject matter.

Fig. 17B is a simplified schematic illustration of a laminated structure formed from the wood piece of fig. 17A, according to one or more embodiments of the disclosed subject matter.

Fig. 17C is a simplified schematic diagram of a multilayer laminate structure formed from the structure of fig. 17B, according to one or more embodiments of the disclosed subject matter.

Detailed Description

Natural wood is a composite of cellulose nanofibers (20-35 wt%) and hemicellulose (20-30 wt%) embedded in a lignin matrix. Cellulose is the major component in wood (40-50 wt%), with higher specific modulus and specific strength than most metals, composites and many ceramics. Natural wood also has a unique three-dimensional porous structure with a plurality of channels, including ducts and fibril lumens extending in the direction of wood growth (e.g., tubular channels with cross-sectional dimensions of 20-80 μm). The cell wall in natural wood is mainly composed of cellulose, hemicellulose and lignin, wherein these three components intertwine with each other to form a strong and stiff wall structure.

In embodiments of the disclosed subject matter, substantially all of the lignin in the natural wood is removed to form a delignified piece of wood. As used herein, "delignified" or "delignification" refers to the removal of substantially all lignin from natural wood, and "removing substantially all lignin" refers to at least 90% of the lignin naturally present in the wood having been removed. For example, the weight percent (wt%) of lignin can be reduced from more than 20 wt% (e.g., 23.4 wt%) in natural wood to less than 5 wt%, and preferably less than 1 wt% (e.g., ≦ 0.6 wt%) in delignified wood. At the same time as lignin is removed, some or substantially all of the hemicellulose may also be removed. Table 1 below provides illustrative values for the chemical composition and density of natural wood (e.g., linden in the united states) and delignified wood.

TABLE 1: composition comparison of Natural Wood and delignified Wood

	Cellulose, process for producing the same, and process for producing the same	Hemicellulose	Lignin	Density of
					Natural wood	41.3% by weight	16.9% by weight	21.8% by weight	0.47g/cm3
Delignified wood	33.4% by weight	6.5% by weight	0.6% by weight	0.13g/cm3

The resulting delignified wood is more porous and less rigid than the original natural wood. Delignified wood also exhibits unique thermal properties, particularly very low thermal conductivity and anisotropic thermal conductivity, which enable delignified wood to be used as an excellent thermal insulator. Conventional thermal isolators are generally isotropic, which may hinder effective thermal management. Conversely, anisotropy of thermal conductivity in delignified wood can provide effective heat dissipation in the axial direction, thereby preventing local overheating on the irradiated side of the delignified wood, while improving thermal insulation along the backside.

In addition, delignified wood exhibits unique optical properties. Specifically, the removal of lignin changes the color of the wood to substantially white. Delignified wood has low emissivity (e.g., < 5%) over the solar spectrum and has the ability to effectively reflect solar thermal energy. Due to its unique composition, which is mainly cellulosic, delignified wood may also exhibit high emissivity in the infrared range, particularly within the atmospheric transmission window (i.e. between 8 μm and 13 μm, inclusive) where electromagnetic radiation may propagate without distortion or absorption. Thus, delignified wood can radiate thermal energy to the space via the atmospheric window to provide passive cooling (or active cooling when coupled with additional components to achieve heat transfer).

The resulting delignified wood is light but strong due to the efficient bonding between the oriented cellulose nano-fibrils. However, in some applications, it may be desirable to have substantially greater strength and/or improved thermal conductivity. For example, in passive cooling applications, it may be desirable to have more heat transfer through the wood. Thus, in embodiments, delignified wood may be densified to improve mechanical properties and thermal conductivity. As used herein, "densification" refers to the process of pressing delignified wood in a direction that intersects the direction of extension of the wood's cavities (i.e., the direction of wood growth) such that the cavities largely or completely collapse (e.g., such that the thickness of the wood is reduced by about 80%).

As described above, the delignification process removes substantially all lignin and at least some hemicellulose from the cell walls of the natural wood, resulting in a holocellulose microstructure having many oriented cellulose nanofibers. Densification then collapses the majority of the microchannels in the delignified wood, thereby achieving a dense laminate structure with compactly stacked and intertwined layers of oriented cellulose nanofibers. The graded orientation with hydrogen bonding between nanofibers and the laminated microstructure significantly improves the tensile strength and toughness of the resulting densified delignified wood. Despite having a compact laminate structure, the higher thermal conductivity than the original delignified wood, the nanopores and ultra-high whiteness imparted by the delignification process provide excellent thermal insulation properties. Table 2 below provides illustrative values for different properties provided by natural wood (e.g., american basswood), delignified wood, and densified delignified wood.

TABLE 2: value of different properties provided by wood products

In some applications, it may be desirable to have a balance of strength and insulation properties. For example, to provide insulation in structural or construction applications, it may be desirable to have improved strength from the densification process while maintaining a lower thermal conductivity of the structure immediately after delignification. Thus, in embodiments, delignified wood may be partially densified to improve mechanical properties and thermal conductivity. As used herein, "partial densification" refers to the process of pressing delignified wood in a direction that intersects the direction of extension of the wood's cavities (i.e., the direction of wood growth) such that the cavities are only partially collapsed (e.g., such that the thickness of the wood is reduced by 50% or less). Thus, partially densified delignified wood can provide a mixture of insulation characteristics and mechanical strength characteristics.

Thus, in embodiments, the thermal and mechanical properties of the resulting delignified wood can be adjusted to suit a particular application by changing the amount of pressing during densification from no pressing at all (0% reduction in thickness, and thus higher porosity) to full pressing (where all channels have completely collapsed, and thus lower porosity, approximately ≧ 80% reduction in thickness). For example, uncompressed delignified wood may be suitable for high insulation applications with minimal strength requirements, such as where the wood is supported between other higher strength components. For example, densified delignified wood may be suitable for passive cooling applications, where the wood forms part of a building structure, such as a roof, wall, or siding. For example, partially densified delignified wood may be suitable for insulation applications with higher strength requirements, such as where the wood is to be formed directly as part of a building structure (such as a roof, wall, or siding).

Furthermore, additional material may be added to the delignified wood before or after pressing to form a mixed structure. The added material may increase functionality not otherwise available with natural wood, such as providing hydrophobicity or fire resistance, while enjoying the improved thermal and/or mechanical properties provided by delignified wood, densified delignified wood or partially densified delignified wood. Thus, embodiments of the disclosed subject matter can be adapted for a variety of applications.

Referring initially to fig. 1, a general method 100 for forming and using delignified wood is shown. The method 100 may begin at 102 where a particular application of delignified wood is selected. As mentioned above, the thermal and mechanical properties of the final wood can be adjusted based on the desired application, and thus the manufacturing process will depend on the end use of the wood.

Method 100 may proceed to 104 where a piece of natural wood is supplied, for example, by cutting from an existing tree (or other plant) or piece of natural wood. For example, fig. 2A shows a natural wood piece 200 that has been cut into a rectangular shape, but other starting shapes are possible, such as, but not limited to, a cylindrical shape or a hollow cylindrical shape. The natural lumber 200 exhibits a unique three-dimensional structure in which the cavities 202 extend along the tree growth direction 206. The cavity 202 is defined by a cell wall 204.

As shown in fig. 2B, within the wood cell wall 204, the three major components, namely, paracrystalline cellulose microfibril aggregates or bundles 208, amorphous heteropolysaccharide hemicellulose 210, and polyphenol propane based branched lignin 212, intertwine to form a powerful functional vascular structure to transport water, ions, and nutrients from the roots to the leaves during photosynthesis. Fig. 2C to 2E are Scanning Electron Microscope (SEM) images showing the morphology and microstructure of the natural wood 200.

The natural wood may be any type of hardwood or softwood, such as, but not limited to, basswood, oak, poplar, ash, alder, aspen, balsa, beech, birch, cherry, white walnut (butternut), chestnut, sandalwood, elm, hickory (hickory), maple, oak, rosewood, plum, walnut (walnut), willow, yellow poplar, larch (bald cypress), cedar (cedar), cypress, douglas fir (douglas fir), fir (fir), hemlock, larch (larch), pine, redwood, spruce, larch (tamarack), juniper (juniper), and yew. In some embodiments, the natural wood may be a naturally occurring fibrous plant other than a tree, such as bamboo.

After cutting 104, the method 100 proceeds to 106 where the piece of natural wood 200 may be treated with a chemical solution to remove substantially all of the lignin therefrom. The chemical solution may comprise chemicals used in pulping or pulp bleaching, and may comprise at least one of the following: NaOH, NaOH/Na₂S、NaHSO₃+SO₂+H₂O、NaHSO₃、NaHSO₃+Na₂SO₃、NaOH+Na₂SO₃、Na₂SO₃、NaOH+AQ、NaOH/Na₂S+AQ、NaHSO₃+SO₂+H₂O+AQ、NaOH+Na₂SO₃+AQ、NaHSO₃+AQ、NaHSO₃+Na₂SO₃+AQ、Na₂SO₃+AQ、NaOH+Na₂S+Na₂S_n、Na₂SO₃+NaOH+CH₃OH+AQ、CH₃OH、C₂H₅OH、C₂H₅OH+NaOH、C₄H₉OH、HCOOH、CH₃COOH、CH₃OH+HCOOH、C₄H₈O₂、NH₃.H₂O、p-TsOH、H₂O₂、NaClO、NaClO₂+ acetic acid, ClO₂And Cl₂Wherein n is an integer and AQ is anthraquinone.

The treatment 106 may be performed under vacuum to promote the chemical solution to fully penetrate the cell walls and cavities of the natural wood. In some embodiments, the treatment 106 may be a single-step chemical treatment, such as a single exposure to a single chemical or mixture of chemicals (e.g., with H)₂O₂Bath (c). Alternatively, the process 106 may be a multi-step chemical process, such as a first exposure to a first chemical or mixture (e.g., with NaOH and Na)₂SO₃A bath) and then exposed to a second chemical or mixture (e.g., with H) for a second time₂O₂Bath (c).

As a result of delignification 106, the yellow natural wood becomes completely white and exhibits a weight percentage change, for example, from 100% to 57%. In particular, the treatment may result in at least 90% (weight percent) of the previous lignin in the original natural wood being removed, while otherwise substantially retaining the cellulose-based microstructure of the natural wood. For example, the treated wood may have less than 5 wt%, preferably less than 1 wt%, for example 0.6 wt% lignin. As schematically shown in fig. 3A-3B, the resulting delignified wood has an increased porosity of the cell wall microstructure 304 and better nano-fibril orientation due to the removal of unoriented and/or self-oriented lignin in the wet-treated state.

Once sufficient lignin has been removed by the treatment of 106, the method 100 can proceed to optionally rinsing the piece of treated wood. Rinsing may include immersing the piece of treated wood in a solvent, such as, but not limited to, ethanol and/or Deionized (DI) water. In some embodiments, the solvent may be at an elevated temperature, such as boiling. The rinsing is effective to remove any chemical solution residue within the piece of treated wood and/or any wood components dislodged by the treatment.

After the washing 108 (or after the treatment 106 ends when there is no washing), the method 100 may proceed to 110, where the delignified wood is subjected to a drying step. Drying may depend on the end use of the wood. For example, where delignified wood is not pressed for a particular insulation application, the wood may be subjected to a drying process that retains the nanopore and open cell structures, such as by freeze drying or critical point drying. Alternatively, in the case where delignified wood is to be used after pressing, the wood may be allowed to air dry.

After drying 110, method 100 may proceed to 112, where it is determined whether pressing is required to achieve densification or partial densification. If compression is not required, the process may proceed to optional further modification 114 (described below), or may be prepared for a particular application 116. The final delignified wood 300 may thus have a porous structure with the cellulose nanofibres oriented along the extension direction 206 of the cavity 202, as shown in fig. 3A to 3B.

Fig. 3C-3I show various SEM images of exemplary delignified wood 300 after freeze-drying. The wood cell walls in natural wood 200 are initially composed of primary cell walls and secondary cell walls, wherein the secondary cell walls are further divided into three layers. As shown in fig. 2E, the cells were bound to each other via the intercellular layer. In the cell wall layer, the middle layer in the secondary cell wall is thickest and consists of parallel cellulose nano-fibril aggregates oriented within a small angular difference along the length axis 206. The Fibril Angle (FA) of this intermediate layer varies by about 10-15 ° and can help define the orientation of the cell wall. Due to the natural orientation of fibrils in wood, the individual cellulose nano-fibrils constituting the cell wall 304 are stacked and oriented parallel to each other, resulting in a graded orientation in delignified wood. Each fibril aggregate consists of oriented crystalline cellulose nano-fibrils with high aspect ratio (i.e. diameter of about 30nm and length > about 1 μm) filled with dextran chains in crystalline order and held together by intermolecular hydrogen bonds and van der waals forces.

After delignification, cellulose nanofibrillar aggregates in the cell wall layer can be observed directly in the fibril cross-section as shown in fig. 3E to 3G. The fibril walls 304 are separated from each other due to the removal of the main part of the lignin-rich intercellular layer and the lignin in the primary and secondary cell walls. The removal of lignin and hemicellulose not only separates fibril aggregates from each other, but also increases the porosity of the fibril wall structure 304, provided that delignified fibrils are carefully dried to avoid fibril wall collapse. Thus, the three-dimensional (3D) microporous structure of the natural lumber may be well maintained, but has more porous cell walls due to the removal of lignin and hemicellulose components, as shown in fig. 3H to 3I.

Returning to fig. 1, if pressing at 112 is desired, the method 100 may optionally proceed to 118, where the delignified wood is moisturized prior to pressing. Humidification may prevent delignified wood from cracking during pressing. For example, humidifying may include subjecting the delignified wood to an elevated relative humidity (e.g., 90% relative humidity) for an extended period of time (e.g., 0.5-24 hours, such as 12 hours). In some embodiments, the humidifying step may be omitted, for example, where only minimal pressing is required or the delignified wood otherwise retains sufficient moisture after the drying process 110.

After humidification 118, the method 100 may optionally proceed to 120, where delignification is performedAnd performing pre-pressing modification on the wood. For example, the optional modification 120 may include the formation or deposition of non-natural particles on the surface of delignified wood. Such surfaces may include internal surfaces, such as cell walls lining cavities, and the external surfaces of delignified wood. The non-natural particles incorporated onto the surface of delignified wood can impart certain advantageous properties to the final densified wood, such as hydrophobicity, weatherability, corrosion resistance (e.g., salt water resistance), and/or flame resistance, among other properties. For example, in one embodiment, hydrophobic nanoparticles (e.g., SiO) may be formed on the surface of delignified wood₂Nanoparticles).

Alternatively or additionally, the optional modification 120 may include adding a polymer to the delignified wood or performing a further chemical treatment that modifies the surface of the chemically treated wood to obtain advantageous properties. For example, the further chemical treatment 120 to provide hydrophobic properties may include at least one of the following: epoxy resin, silicone oil, polyurethane, paraffin emulsion, acetic anhydride, Octadecyltrichlorosilane (OTS), 1H,2H, 2H-perfluorodecyltriethoxysilane, fluororesin, Polydimethylsiloxane (PDMS), Methacryloxymethyltrimethylsilane (MSi), polyhedral oligomeric silsesquioxane (POSS), Potassium Methylsiliconate (PMS), dodecyl (trimethoxy) silane (DTMS), hexamethyldisiloxane, dimethyldiethoxysilane, tetraethoxysilane, methyltrichlorosilane, ethyltrimethoxysilane, methyltriethoxysilane, trimethylchlorosilane, phenyltrimethoxysilane, phenyltriethoxysilane, propyltrimethoxysilane, polymethyl methacrylate, polydiallyldimethylammonium chloride (polyDADMAC), 3- (trimethoxysilyl) propyl Methacrylate (MPS), Hydrophobic stearic acid, amphiphilic fluorinated triblock azide copolymer, polyvinylidene fluoride and fluorosilane, n-dodecyl trimethoxysilane, and sodium dodecyl sulfate.

In an exemplary embodiment, the pre-press modification 120 includes applying a hydrophobic coating to delignified wood. For example, delignified wood may be immersed in a 2% 1H, 2H-perfluorooctyltriethoxysilane/ethanol solution for 24 hours prior to pressing. The fluorosilane groups are chemically bonded to the wood channels, thereby providing a stable surface modification and limiting the effect of moisture and water on the wood. Unlike the coating process, the solution penetrates the mesoporous wood structure and converts the hydrophilic-OH groups of the cellulose into hydrophobic functional groups (i.e., perfluorinated hydrocarbon chains). The fluorosilane treatment can introduce hydrophobicity such that the final densified delignified wood exhibits a static contact angle of at least 90 ° or a dynamic contact angle of less than 10 °. In some embodiments, the final wood may exhibit superhydrophobicity (i.e., having a static water contact angle of 150 ° or greater) as a result of the fluorosilane treatment.

Alternatively or additionally, the pre-press modification 120 may include at least one of the following to provide weather or corrosion resistance: copper dimethyldithiocarbamate (CDDC), ammoniated quaternary Ammonium Copper (ACQ), Copper Chromite Arsenate (CCA), ammoniated zinc arsenate (ACZA), copper naphthenate, copper acid chromate, copper citrate, copper azole, copper 8-hydroxyquinoline, pentachlorophenol, zinc naphthenate, copper naphthenate, creosote, titanium dioxide, propiconazole, tebuconazole (tebuconazole), cyproconazole, boric acid, borax, organic Iodide (IPBC), and Na₂B₈O₁₃·4H₂O。

Although modification 120 is shown as occurring after humidification 118, modification 120 may also occur before or simultaneously with humidification 118, according to one or more contemplated embodiments. Method 100 may then proceed to 122 where the delignified wood is pressed in a direction that intersects the direction in which the cavities extend. For example, the pressing 122 may be performed in a direction substantially perpendicular to the direction in which the cavity extends, or the pressing 122 may be at another angle, but with a force component perpendicular to the direction in which the cavity extends. The pressing 122 may reduce the thickness of the wood, thereby increasing its density, and remove any voids or gaps within the cross-section of the wood. For example, the press 122 may be at a pressure between 0.5MPa and 10MPa, such as 5 MPa. In some embodiments, pressing may be performed at room temperature (i.e., cold pressing), while in other embodiments, pressing may be performed at elevated temperature (i.e., hot pressing). For example, the pressing may be performed at a temperature between 20 ℃ and 120 ℃, e.g. 60-80 ℃.

During pressing 122, hydrogen bonds may form between the remaining cellulose-based nanofibers of the cell walls of the delignified wood, thereby improving the mechanical properties of the wood. Furthermore, any particles or material formed on the surface of the wood or within the wood during modification 120 may remain after pressing, with the particles/material on the inner surface embedded within the collapsed cavities and entangled cell walls. The pressing 122 may be performed for a period of time that allows the desired hydrogen bonds to form. For example, delignified wood may be held under pressure for a period of at least 5 minutes, although other times are possible depending on factors such as temperature, relative humidity, and wood type. For example, the delignified wood may be held under pressure for at least 1 hour, at least 12 hours, at least 24 hours, or at least 48 hours. Pressing may result in a relatively low surface roughness, for example 10nm or less (arithmetic average surface roughness).

Fig. 5A shows a delignified wood block 300 having a cavity 202 extending along direction 206 and a wall 304 composed of cellulose-based nanofibers oriented along direction 206. The block 300 may be pressed 502 in a direction crosswise to the extension direction 206, resulting in the densified delignified wood structure 310 of fig. 5B-5C. As a result of the compaction, the cavity 302 may completely collapse and the cell walls 304 may become intertwined, as shown at 312. The pressing may be such that W of the block 300₁In contrast, the thickness W of the block 310 after pressing₂The reduction is between 0% and 100%. E.g. W of block 300₁In contrast, the thickness W₂Can be reduced by more than 50%, 75% or 80%.

It is apparent from fig. 5D to 5E that the spaces between the channels of the natural wood completely disappear upon densification, while closely stacked laminate layers can be found along the tree growth direction (i.e., 206 or L). at the higher magnification of fig. 5F, highly oriented cellulose nanofibers can be observed, indicating that densification does not destroy the cellulose nanofiber orientation.

As noted above, the compaction may be designed to only partially collapse (i.e., partially densify) the cavity to provide the desired mix of thermal and mechanical properties. Thus, at 124 in FIG. 1, it is determined whether sufficient throttling has been performed based on the application selected in 102. If a smaller thickness is desired, the process may return to 122 to continue pressing until the desired thickness (and corresponding densification) is achieved. Once the desired thickness has been achieved, the process may proceed to optional modification 114 via 124.

Delignification 106 and/or densification 122 may be accomplished in various manufacturing settings. Referring now to fig. 6A, an exemplary manufacturing process for forming densified delignified wood from natural wood 602 is shown. The natural lumber 602 may be a sheet-like, rod-like, tape-like, strip-like, block-like, film-like, or any other shape of lumber. The cavities in the natural wood 602 may extend along the wood growth direction 606. The first step 600 in the manufacturing process may be to immerse the natural wood 602 in a chemical solution 604, for example as described above for step 106 of the process 100, to remove substantially all of the lignin from the wood 602. The chemical solution 604 and the wood 602 immersed therein may be contained within a housing 608. In some embodiments, the housing 608 may be a vacuum housing, and the solution 604 and wood 602 may be maintained under vacuum during immersion. Alternatively or additionally, the housing 608 or another component therein may heat the solution 604 to a temperature above room temperature. For example, the solution 604 may be heated to boiling during the chemical treatment 600.

After the process 600, the delignified wood 616 may be transferred from the hull 608 to a compression station 610 for pressing in a direction substantially perpendicular to the direction of extension 606 or at least crosswise to the direction of extension 606, for example as described above with respect to 122 of the method 100. For example, the compression station 610 may include an upper platen 614 and a lower platen 618. The relative motion between platens 614, 618 results in the desired compression of delignified wood 616 to produce densified delignified wood. For example, upper platen 614 may be moved toward lower platen 618, with lower platen 618 remaining stationary and supporting logs 616 thereon to apply compressive force 612 to logs 616. Alternatively, the two platens 614 and 618 may be moved toward each other to apply the compressive force 612.

In some embodiments, during compression, one or both of the platens 614, 618 may be heated to raise the temperature of the wood 616 above room temperature. Alternatively or additionally, the platens 614, 618 may not be heated, but a separate heating mechanism may be provided, or the environment containing the compression station may be heated, in order to raise the temperature of the wood 616.

Referring to fig. 6B, another exemplary manufacturing process for forming densified delignified wood from natural wood 632 is shown. The natural lumber 632 may be in the form of logs or cylindrical strands with cavities extending in a direction perpendicular to the page. The first step 620 may be to cut the natural wood 632 using, for example, a rotary cutter 634 to separate a thin continuous layer 636 of natural wood for subsequent processing. The natural wood layer 636 may be conveyed to the housing 638 for a next step 630 in the manufacturing method, e.g., as described above with respect to 106 of the method 100, e.g., immersing the wood 636 in the chemical solution 604 to remove substantially all of the lignin from the wood layer 636.

Similar to the housing 608, the housing 638 may be configured to apply vacuum and/or heat during immersion. In some embodiments, the size of the housing 638 and the speed of transport of the layer 636 from the natural wood 632 through the housing 638 may correspond to a desired immersion time for the chemical treatment. Thus, the time from when a portion of the layer 636 enters the housing 638 to when it exits the housing 638 to enter the compression station 640 will correspond to the immersion time required for substantially complete lignin removal.

After the process 630, the delignified wood 648 may be transferred from the shell 638 to a compression station 640 to be compressed in a direction substantially perpendicular to, or at least crosswise to, the direction of elongation, e.g., as described above with respect to 122 of the method 100. For example, the compression station 640 may include an upper roller 644 and a lower roller 646, which may be maintained at a fixed distance from each other. The fixed distance may be less than the thickness of the chemically treated wood 648 so as to apply the compaction force 642 that results in densified wood.

In some embodiments, one or both of the rollers 644, 646 may be heated during compression to raise the temperature of the wood 648 above room temperature. Alternatively or additionally, the rollers 644, 646 may not be heated, but a separate heating mechanism may be provided, or the environment containing the compression station 640 may be heated in order to raise the temperature of the wood 648.

Although only two rollers 644, 646 are shown in fig. 6B, multiple rollers may be arranged in series along the conveyance direction of the sheet 648. The sheet 648 may be maintained under pressure as the sheet 648 is conveyed between adjacent rollers to provide a desired cumulative compression time (e.g., on the order of minutes or hours). Alternatively or additionally, the size of the rollers 644, 646 and the conveyance speed of the sheet 648 may correspond to a desired compression time. Thus, the time from when the sheet 648 is first compressed to when the sheet 648 exits the compression station 640 as densified delignified wood 650 will correspond to the desired pressing time. Of course, the compression station 640 may also be disengaged from the chemical treatment 638, for example, by cutting the sheet 636 before or after the chemical treatment 638. In such a configuration, the compression station may take the form of a roller as shown in fig. 6B or as a flat plate as shown in fig. 6A.

Referring to fig. 6C, an exemplary manufacturing process for forming densified delignified wood from natural wood 662 is shown. The natural lumber 662 may be in the form of a hollow cylinder with a cavity extending along the lumber growth direction 664. The first step 660 in the manufacturing process may be to immerse the native wood 662 in the chemical solution 604, for example as described above for 106 of the method 100, to remove substantially all of the lignin from the wood 662. The chemical solution 604 and wood 662 immersed therein may be contained within a housing 666, which housing 666 may be configured to apply vacuum and/or heat during immersion, similar to housing 608 of fig. 6A.

After the process 660, the delignified wood cylinders 668 can be conveyed from the housing 666 to a compression station 670 to be pressed in a direction substantially perpendicular to the direction of extension 664 or at least crosswise to the direction of extension 664 (perpendicular to the plane of the page at 670 in fig. 6C), for example as described above with respect to 122 of the method 100. For example, the compression station 670 may include an upper roller 672 disposed on the exterior of the cylinder 668 and a lower roller 674 disposed within the interior of the cylinder 668. The rollers 672, 674 may be maintained at a fixed distance from each other as the wall of the cylinder 668 passes therethrough. The fixed distance may be less than the wall thickness of the chemically treated wood 668, thereby applying a pressing force 676 that results in a hollow cylinder of densified wood.

In some embodiments, one or both of the rollers 672, 674 may be heated during compression to raise the temperature of the wood 668 above room temperature. Alternatively or additionally, the rollers 672, 674 may not be heated, but a separate heating mechanism may be provided, or the environment containing the compression station 670 may be heated, in order to raise the temperature of the wood 668.

Although only two rollers 672, 674 are shown in fig. 6C, multiple rollers may be provided in series around the perimeter of cylinder 668. The walls of the cylinder 668 can be maintained under pressure as the walls of the cylinder 668 are conveyed between adjacent rollers to provide a desired cumulative compression time (e.g., on the order of minutes or hours). Alternatively or additionally, the size of the rollers 672, 674 and the rotational speed of the cylinder 668 may correspond to a desired compression time.

Referring to fig. 6D, an exemplary manufacturing process for forming densified delignified wood from natural wood 682 is shown. The natural wood 682 may be in the form of a solid cylinder with a cavity extending along the wood growth direction 684. A first step 680 in the manufacturing process may be to immerse the natural wood 682 in the chemical solution 604, for example as described above for 106 of the process 100, to remove substantially all of the lignin from the wood 682. The chemical solution 604 and wood 682 immersed therein may be contained within a housing 666, which housing 666 may be configured to apply vacuum and/or heat during immersion, similar to housing 608 of fig. 6A.

After the process 680, the delignified wood cylinders 685 may be conveyed from the hull 666 to a compression station 690 to be pressed in a direction substantially perpendicular to the direction of extension 684, or at least crosswise to the direction of extension 684 (which is perpendicular to the plane of the page at 690 in fig. 6D), for example as described above with respect to 122 of the method 100. For example, the compression station 690 may include a single roller 688 disposed on an exterior of the cylinder 685, the single roller 688 being supported and rotatable about a central axis of the cylinder. The rollers 688 may be held at a fixed distance pressed into the walls of the cylinder 685 as they rotate past, thereby applying a pressing force 692 that results in a solid cylinder of densified delignified wood.

In some embodiments, the roller 688 can be heated during compression to raise the temperature of the wood 685 above room temperature. Alternatively or additionally, the rollers 688 may not be heated, but a separate heating mechanism may be provided, or the environment containing the compression station 690 may be heated, in order to raise the temperature of the wood 886.

Although only a single roller 688 is shown in fig. 6D, multiple rollers can be positioned in series around the circumference of the cylinder 685. As the cylinder 685 is conveyed between adjacent rollers, the cylinder 685 may be maintained under pressure in order to provide a desired cumulative compression time (e.g., on the order of minutes or hours). Alternatively or additionally, the size of the rollers 688 and the rotational speed of the cylindrical body 685 may correspond to a desired compression time. In yet another alternative, instead of compression station 690 having rollers 688, cylinders 686 may be pressed by compression belts 694 of compression station 695, as shown in fig. 6E. In such a configuration, cylinder 686 may remain stationary rather than being rotated.

Although fig. 6A-6E illustrate a single chemical treatment step, in some embodiments, multiple chemical treatments are applied to achieve delignification. In embodiments where delignification involves a multi-step chemical process, the solution 604 within the hull 608 may be exchanged for a subsequent treatment solution while the wood 602 is held in the hull, or the wood 602 may be moved in sequence to a different hull (not shown) containing the next treatment solution or to a different portion of the hull 608 containing the next treatment solution.

Although specific wood shapes and fabrication techniques have been illustrated in fig. 6A-6E, other shapes (solid or hollow) and fabrication techniques are possible according to one or more contemplated embodiments. Therefore, the shape and manufacturing technique of the wood are not limited to those specifically illustrated. Further, although the rinse station, the drying station, the humidification station, and the pre-press modification and post-press modification are not specifically shown, the techniques of fig. 6A-6E may be readily adapted to include rinsing, drying, humidifying, pre-press modification, and/or post-press modification in accordance with one or more embodiments of the disclosed subject matter.

Returning to fig. 1, after pressing 122, or when densification is not required at 112, method 100 optionally proceeds to 114 where further modifications may be performed. For example, the optional modification 114 may include forming or depositing a coating (e.g., with non-natural particles) on the exterior surface of the delignified wood. The coating can impart certain advantageous properties to the delignified wood, such as hydrophobicity, weatherability, corrosion resistance (e.g., salt water resistance), color, and/or flame resistance, among others. For example, the coating may include an oil-based coating, a hydrophobic coating, a polymeric coating, or a fire resistant coating.

Alternatively or additionally, the coating of the modification 114 may comprise at least one of the following: boron Nitride (BN), montmorillonite, hydrotalcite, Silica (SiO)₂) Sodium silicate, calcium carbonate (CaCO)₃) Aluminum hydroxide (Al (OH)₃) Magnesium hydroxide (Mg (OH)₂) Magnesium carbonate (MgCO)₃) Aluminum sulfate, ferric sulfate, zinc borate, boric acid, borax, triphenyl phosphate (TPP), melamine, polyurethane, ammonium polyphosphate, phosphate ester, phosphite, ammonium phosphate, ammonium sulfate, phosphonate, diammonium phosphate (DAP), monoammonium phosphate (MAP), guanylurea phosphate (GUP), guanidine dihydrogen phosphate, and antimony pentoxide. In one embodiment, a refractory coating of nanoparticles (e.g., BN nanoparticles) may be formed on the outer surface of the densified wood. Alternatively or additionally, the further modification 114 may include dyeing the otherwise white delignified wood. For example, dyeingThe material may be methylene blue.

After optional modification 114, the method 100 may optionally proceed to 116, where the delignified wood may be prepared for end use, such as by machining or manipulation to alter the structure or shape of the delignified wood. Machining processes may include, but are not limited to, cutting (e.g., sawing), drilling, wood turning, tapping, boring, engraving, routing, grinding, coping, and barreling. The manipulation process may include, but is not limited to, bending, molding, and other forming techniques.

After optional machining or manipulation at 116, the delignified wood may be used in a particular application. Delignified wood can be applied to a variety of structures and uses due to its unique combination of thermal, optical and mechanical properties. For example, delignified wood may be adapted to function as:

exterior parts (e.g., body panels, door panels, roofs, bumpers, floors, roofs, trim, masts, etc.), interior structural parts (e.g., chassis, frame rails, cross members, fuselage frames, wing frames, etc.), or interior parts (e.g., door panels, trim, storage bins, shelves, etc.) of an automobile, truck, motorcycle, train, aircraft, watercraft, spacecraft, boat, or any other vehicle, or vehicle;

an exterior component (e.g., exterior wall, siding, roofing, blinds, etc.), an interior structural component (e.g., frame, column, wall panel, lintel, beam, spandrel, underfloor, etc.), or an interior component (e.g., door frame, window frame, picture frame, wall, floor, paneling, ceiling, trim, stairs, balustrades, etc.) of a residence, office, barn factory, warehouse, tower, or any other building or structure;

structural parts of decks, awnings, docks, decks, bridges, poles, weather stands or platforms;

furniture (e.g., chairs, benches, desks, tables, cabinets, wardrobes, countertops, etc.) or internal structural components thereof (e.g., the frame of a sofa or chair, bed frame, etc.), or home furnishings (home accessories) or upholstery;

instruments (e.g., pianos, guitars, violins, harps, zithers, drums, etc.), sports equipment (e.g., golf clubs, table tennis tables and rackets, basketball stands, basketball goal or goal posts, baseball bats, etc.), tools (e.g., hammer handles, broom handles, sawhorses, etc.); or

Protective components (e.g., computer cases, cell phone cases, explosion proof shields, protective vests, etc.), enclosures, containers, boxes, shipping crates, packaging, or housings.

The above list is not intended to be exhaustive. According to one or more contemplated embodiments, uses of delignified wood other than those specifically listed are also possible. Indeed, one of ordinary skill in the art will readily appreciate that delignified wood may be suitable for other applications based on the teachings of the present disclosure.

As described above, delignified wood may exhibit anisotropic thermal properties that may be advantageously used in insulation applications, for example, fig. 4A illustrates an exemplary delignified wood block 400 in which the wood is cut such that the top surface 402 and bottom surface 404 are substantially parallel to the direction of extension 206 of the wood cavity (i.e., parallel to the tree growth direction L.) compared to natural wood, thermal conductivity 410 in the transverse/radial direction (i.e., perpendicular to the cellulose nano-fibril orientation direction 206) is greatly reduced due to the porous cell walls and open cavities of the delignified wood, for example, delignified wood 400 may have a transverse thermal conductivity 410 of about 0.03W/m-K compared to natural wood, while, due to the presence of nanopores in the cell walls, nano-fibrils act to conduct heat along their axes compared to natural wood, albeit at a reduced rate of conductivity, delignified wood exhibits anisotropic thermal conductivity, wherein the axes (i.e., to heat parallel to the cellulose) are parallel to the radial direction 206, thermal conductivity is greater than that of natural wood 206, which may allow for example, thermal conductivity of the transverse direction of the log 408 to be more than that of the transverse direction of thermal conductivity of the wood, which may cause thermal conductivity of the lignin to be greater than about 0.06.

Delignified wood 400 consists of long oriented fibril aggregates with a large surface-to-volume ratio and a high aspect ratio. As delignification removes substantially all lignin and most hemicellulose, the fibril walls are more porous than natural wood. This results in a lower compressive strength of the delignified wood in the thickness direction of the nano-fibrils compared to natural wood. For example, for delignified wood 400, the maximum compressive stress along the axial direction 206 may be about 13 MPa. However, the delignified samples had significant strength in the thickness direction of the fibrils, and more significant strength in the length direction of the fibrils, due to the orientation of the fibrils in the fibril wall, i.e., the orientation twisted along the fibril axis 206. The tensile and compressive properties are affected differently due to the different failure mechanisms for each loading case.

The nanofiber structure of delignified wood 400 also improves flexibility compared to natural wood. Accordingly, the delignified wood 400a can be bent without damage, as shown in fig. 4B, wherein the extension direction 206 of the cavity is along the curved top surface 402a and bottom surface 404 a. In addition, when the thickness t of the delignified wood 400 is less than about 1mm, the wood block 400 can be rolled or folded into a certain structure. For example, as shown in fig. 4C, delignified wood 400b may be rolled into a tube or conduit, with one surface 402b forming the exterior of the conduit and an opposing surface 404b defining an interior volume 414 of the conduit. A joint 412 may couple opposite ends of delignified wood 400b to seal the interior volume 414 from the exterior of the conduit.

In contrast, densification of delignified wood may result in significantly improved mechanical properties compared to natural wood. In particular, due to the cellulose nano-scale oriented in the growth direction 206 after lignin removalThe larger interaction area between the exposed hydroxyl groups of the fibers, and thus the densified delignified wood is mechanically stronger and tougher than natural wood. The densified delignified wood 700 exhibited tensile strengths as high as 404.3MPa ± 14.8MPa, which is about 9 times that of natural wood 702, as shown in fig. 7A. Mechanical strength per unit weight is an important parameter in structural applications such as buildings. For densified delignified wood 700, the specific tensile strength may exceed 300MPa-cm³In g, e.g. 334.2MPa-cm³/g。

In addition, 3.68MJ/m was observed for the densified delignified wood 700³Which is about 10 times the toughness of the natural lumber 702, as shown in fig. 7B. This can be attributed to the energy dissipation achieved by repeated hydrogen bond formation/cleavage on a molecular scale in the densified delignified wood. It should be noted that in conventional structural materials, strength and toughness are generally mutually exclusive. Thus, for structural material design and other applications, it is desirable to simultaneously enhance the strength and toughness of densified delignified wood.

As shown in fig. 7C, the densified delignified wood 700 also exhibits improved scratch hardness compared to natural wood 702, where direction a represents a direction parallel to the tree growth direction 206, direction B represents a direction perpendicular to the tree growth direction 206, and direction C represents a direction intermediate between a and B. The scratch hardness of the densified delignified wood reached 0.175GPa in direction C as characterized by a linear reciprocating tribometer. The scratch hardness of the densified delignified wood increased 5.7 times, 6.5 times and 8.4 times in directions A, B and C, respectively, compared to natural wood.

As described above, the unique microstructure of delignified wood provides anisotropic thermal properties that can be used in insulation applications. For example, fig. 8A shows an exemplary delignified wood 800 for use as a spacer material. Delignified wood 800 has four key properties required for excellent thermal insulation. First, the delignification process increases the porosity of the wood (e.g., from 60% of basswood to about 91% of delignified wood). The large porosity achieves a thermal conductivity much smaller than that of natural wood. Second, the removal of mixed lignin and hemicellulose greatly reduces the connections between cellulose fibrils and fibril aggregates within the fibril wall 304, thereby achieving much weaker interactions between fibrils and further reducing thermal conductivity in the transverse/radial direction. Third, the aligned high aspect ratio nanofibrils 314 aggregates enable anisotropic heat flow 806 along the direction of nanofibril orientation. Fourth, most of the interstitial channels 202 (fibrils and conduit elements) in the delignified wood 800 have a diameter between 10-100 μm, while the individual cellulose nano-fibrils 314 in the fibril aggregate in the cell wall 304 exhibit a spacing between fibril aggregates in the nanometer range. The spacing between the oriented fibril aggregates is much smaller than the mean free path of air at ambient conditions (about 70nm), which reduces the contribution of air heat conduction.

These features combine to produce anisotropic thermal conductivity for the highly isolated delignified wood 800. The thermal conductivity was 0.032 + -0.002W/m-K at 25.3 deg.C in the radial direction and 0.056 + -0.004W/m-K at 24.3 deg.C in the axial direction, as shown in FIG. 8B. In contrast, at 22.7 ℃, natural wood (linden, usa) exhibited a thermal conductivity of 0.107 ± 0.011W/m-K in the radial direction and a thermal conductivity of 0.347 ± 0.035W/m-K in the axial direction, as shown in fig. 8C. The thermal conductivity in natural wood remains almost constant from room temperature to 80 ℃. However, for delignified wood, at higher operating temperatures, the thermal conductivity in the transverse direction slowly rose from 0.03W/m-K to 0.055W/m-K, while in the axial direction the value slowly changed from 0.056W/m-K to 0.10W/m-K.

Performing densification on delignified wood increases thermal conductivity, which may be useful for certain applications. However, densification maintains the wood cell orientation, so that the densified delignified wood also exhibits strong anisotropy in thermal conductivity. As shown in fig. 8E, the thermal conductivity of the densified delignified wood along (axial) and perpendicular (radial) to the direction of tree growth was measured to be 1.82W/m-K and 0.168W/m-K, respectively. In contrast, the thermal conductivity of natural wood (i.e., basswood, but in a different lot than that of the basswood of fig. 8C) was 0.468W/m-K and 0.156W/m-K in the axial direction and the radial direction, respectively, as shown in fig. 8D.

Thus, the thermal conductivity of the densified delignified wood in the transverse direction is comparable to natural wood, which can be attributed to the complete removal of the bulk phonon scattering interface between lignin and oriented cellulose fibers during the delignification process. Delignified wood may exhibit higher crystalline quality that contributes to higher thermal conductivity in the axial direction when chemically removing amorphous lignin and hemicellulose. Notably, the specific thermal conductivity of densified delignified wood, when normalized by weight, is much lower in both directions than natural wood. For densified delignified wood, a higher anisotropy factor can be obtained. For example, the densified delignified wood may have an anisotropy factor of at least five or at least ten, such as 10.8, which is 3.6 times higher than that of natural wood.

The removal of substantially all lignin from natural wood also produces a unique low emissivity, making delignified wood very effective at blocking solar heat radiation. For example, as shown in fig. 9A, the delignified wood piece 900 exhibits an average of about 95% reflection covering a wavelength range from 400nm to 1100nm, with transmission below the base noise level (< 0.1%). The unique broadband omnidirectional reflectance of delignified wood results from the dense concentration of nanoscale scattering centers on the surface of the delignified wood. The emissivity was calculated to be about 5%, indicating that the thermal energy from the radiant heat source was effectively reflected. In contrast, natural wood 902 absorbs an average of 50% of the light in the visible spectrum.

To further test the reflection characteristics of delignified wood 900, the spot size was 1mm and the input power was 0.95W/mm²Directed at the surface of delignified and natural wood samples by a collimated 820nm laser source. Such asAs shown in fig. 9B, the maximum temperature of delignified wood is 36 ℃, while natural wood 902 exhibits a significantly higher temperature of 99.4 ℃. The large difference in thermal response between delignified wood 900 and natural wood 902 is due to improved heat dissipation due to anisotropic thermal conductivity and lower absorption due to increased reflectance.

The densified delignified wood exhibits similar optical properties with respect to solar radiation. For example, the reflection results of the densified delignified wood piece 910 and natural wood piece 902 in the visible spectrum are shown in fig. 9C. Both woods show negligible transmission (less than 0.1%). Therefore, the absorbance spectrum is obtained by subtracting the reflectance from the whole (unity) (a ═ 1-R-T), as shown in fig. 9D. Despite being compressed, the densified delignified wood still contains some multi-scale pores, as well as cellulose nanofibers oriented substantially along the tree growth direction 206. For strong broadband reflection at all visible wavelengths, the multi-scale holes and channels act as randomizing and chaotic scattering elements, as shown in FIG. 9C. With the use of high refractive index particles (e.g. TiO)₂) To achieve a difference in whiteness (which high refractive index particles would otherwise suffer from high absorption in the ultraviolet range, which may be increased by heating due to solar radiation), cellulose nanofibers exhibit a low refractive index of about 1.48. Thus, the reflectance of the densified delignified wood 910 in the visible range is greater than 90%, thus yielding a low absorption with respect to the solar radiation spectrum 904. When the electric field of the incident light is polarized along the orientation direction of the cellulose nanofibers 206, the reflectance of the densified delignified wood 910 is further increased to about 96% due to the strong scattering of the oriented nanofibers and the low refractive index of the cellulose.

The absorption of the densified delignified wood 910 at visible wavelengths is significantly reduced compared to natural wood 902 due to the complete removal of the lignin and the largely disordered cellulose-based photon scattering centers of the densified delignified wood. Integrated solar absorption of densified delignified wood 910Luminosity is 8% + -0.4%, resulting in a combined power of 1000W/m²(corresponding to the intensity of solar radiation) of about 75W/m under direct light²Is heated by solar energy. In contrast, natural wood 902 exhibited an average solar absorbance of 29% ± 0.3% which was nearly 200W/m higher than densified delignified wood 910²。

The anisotropic and low thermal conductivity properties, coupled with the reflectivity of the radiation, may allow embodiments of delignified wood and densified delignified wood to act as effective thermal barriers. For example, as shown in fig. 8A, the layered structure of oriented cellulose nano-fibrils of delignified wood 800 effectively reflects 804 incident radiant energy 802 while redirecting 806 the absorbed heat in the planar direction, thereby minimizing (or at least reducing) the amount of heat reaching the back surface of the wood 800. The delignified wood produced can redirect incoming thermal energy in the axial direction, resulting in much lower temperatures at the front and back sides of the wood, compared to isotropic insulation.

Due to its chemical composition, delignified wood also preferentially emits radiation in the infrared range, which can be used in combination with low anisotropic thermal conductivity and high solar radiation reflectance to facilitate, for example, passive cooling applications. Specifically, the emissivity spectrum of delignified wood densified in the infrared range from 5 to 25 μm (i.e., covering a black body emission centered at room temperature) is shown in fig. 12A. Densified delignified wood exhibits high emissivity in the infrared range (i.e., close to unity), emits strongly at all angles, and radiates a net heat flux as infrared radiation through an atmospheric transparent window (i.e., 8 to 13 μm) to a cooling radiator in the exterior space. In other words, densified delignified wood can be considered "black" in the infrared range, and appear "white" in the solar spectrum.

As shown in fig. 12A-12B, the infrared emission spectral response shows negligible angular dependence of 0-60 °. The average emissivity of the whole atmospheric window is greater than that of the emission angle between +/-60 DEG0.9, indicating a stable emitted heat flux when the densified delignified wood is at different angles relative to the sky, as in practical applications. The strong emission from 8 μm to 13 μm is mainly due to the emission at 770cm^-1And 1250cm^-1Complex infrared emissions of OH associations, C-H, C-O and C-O-C stretching vibrations. Cellulose in delignified wood appears at about 1050cm^-1(9 μm) the strongest infrared absorbance by OH and C-O centered, which is well within the atmospheric transparent window. High emissivity over the residual infrared spectrum causes radiative heat exchange between the densified delignified wood and the atmosphere, such as in a second atmospheric window between 16-25 μm, which further increases the total radiative cooling flux as the surface temperature approaches ambient temperature.

Thus, delignified wood densified in the infrared range can have simultaneously low solar absorption, high solar radiation reflection and good emission. Applications may take advantage of these simultaneous properties, such as providing cooling via radiant heat transfer. For example, fig. 11 shows a cooling arrangement 1100 employing densified delignified wood 1110. When the densified delignified wood 110 is facing a clear sky 1106 in an open environment, its surface radiates heat 1104 while absorbing solar radiation 1006 and any thermal radiation emitted by the atmosphere. However, due to the optical properties of the surface of wood 1110, most of the solar radiation 1006 is reflected 1020, rather than being absorbed by wood 1110. As a result, the emitted heat flux 1104 of the densified delignified wood 1110 is much greater than any solar radiation 1006 absorbed by the densified delignified wood, thereby producing a continuous net emitted heat flux.

Meanwhile, heat may be transferred from the surrounding environment to the wood 1110 via conduction and convection (non-radiative processes) due to a temperature difference between the wood 1110 and the surrounding environment. In addition, heat 1108 may be transferred from heat source 1102 to wood 1110. Heat is conducted from the back surface to the front surface through the thickness of the wood 1110 via lateral thermal conductivity and can be emitted to the sky 1106 via radiation. Alternatively or additionally, heat source 1102 may be disposed at an end of logs 1110 (as shown in phantom in fig. 11) such that heat 1108 is transferred parallel to tree growth direction 206, thereby taking advantage of the relatively high axial thermal conductivity of logs 1110.

In some embodiments, heat source 1102 may be an internal environment or structure separated from an external environment by the piece of densified delignified wood 1110. In such embodiments, densified delignified wood 1110 may be considered to provide passive cooling because no additional mechanical or external energy is required to provide the cooling effect. Alternatively or additionally, the heat source 1102 may be part of a heat transfer system, such as a heat exchanger or other component of a heating, ventilation, and air conditioning (HVAC) system, where heat 1108 from the system is dumped to densified delignified wood 1110 for radiant cooling. In such embodiments, densified delignified wood 1110 may be considered as part of an active cooling system.

To test the effect of passive cooling using densified delignified wood, a test setup 1300 as shown in fig. 13A was used, specifically, the same size samples (e.g., 60mm × 45mm × 3mm) of densified delignified wood 1306 and natural wood 1310 were placed in respective windows of a polystyrene housing 1304, with the interior volume 1302 of the housing 1304 isolated from the outside environment a surface 1314 of the housing 1304 was covered with a mirror film that was reflective to solar radiation to reduce the heating effect via solar radiation absorption at room temperature (300K), the densified delignified wood showed 37.4W/m during the daytime and nighttime, respectively²And 112.4W/m²The emitted heat flux of (1). It is worth noting that the emitted heat flux increases with the ambient temperature, which is desirable in practical applications.

The bottom surface 1308 of the densified delignified wood 1306 and the bottom surface 1312 of the natural wood 1310 were measured to determine the temperature change of the respective materials over time. Fig. 13B-13C are graphs of the resulting temperatures of natural wood 1356 and densified delignified wood 1354 during the night and day, respectively, and the level of incident solar radiation 1358 during the day. When densified delignified wood 1354 is facing a clear sky, densified delignified wood 1354 exhibits a temperature below ambient temperature 1352 as a result of radiant cooling for both nighttime and daytime operations.

During the night (fig. 13B), the steady state temperature of densified delignified wood 1354 was 4.1 ± 0.2 ℃ lower than ambient temperature 1352. Since natural wood behaves like a black emitter with high emissivity in the mid-infrared region, it has the same temperature curve 1356 as densified delignified wood 1354. However, during the daytime (fig. 13C), densified delignified wood 1354 can maintain its temperature below ambient temperature 1352 despite exposure to solar radiation. Specifically, from 10:54 am to 14:02 pm, at over 800W/m²The back surface of the densified delignified wood 1354 was cooled to 1.4 ℃ ± 0.5 ℃ below ambient temperature 1352 (where the temperature curve drop was due to a brief shade of sunlight by the spreading cloud at 13:46 pm). In contrast, the back surface temperature of natural wood 1356 is 4.7 ℃ ± 1.7 ℃ higher than the ambient air temperature 1352 due to the heating effect of light absorption. A temperature reduction of 6.1 ℃ ± 1.4 ℃ can be obtained via the use of densified delignified wood compared to natural wood. It should be noted that the cooling performance under favorable atmospheric conditions can be further improved.

While densified delignified wood exhibits excellent passive radiation cooling characteristics, practical applications require stable performance under different weather conditions, such as different moisture levels, and resistance to degradation even when exposed to water and other elements. To improve the stability of the densified delignified wood to water, the wood may be rendered hydrophobic prior to use. For example, the densified delignified wood may be subjected to a fluorosilane treatment (e.g., 1H, 2H-perfluorodecyltriethoxysilane as part of the above-described pre-press treatment 120). The fluorosilane treatment is capable of introducing a superhydrophobic surface with a static water contact angle of about 150 °. Furthermore, such treatments can easily penetrate into the mesoporous structure, thereby rendering the densified delignified wood super-hydrophobic (even from the inside) with little change in optical and thermal properties, thereby supporting the radiant cooling performance of the wood.

Although the above discussion focuses on the use of densified delignified wood, delignified wood (i.e. not pressed) or partially densified delignified wood (i.e. not fully pressed) may also be used for cooling applications. However, the reduced thermal conductivity of delignified or partially densified delignified wood compared to densified delignified wood can reduce the heat transfer through the wood and thereby inhibit effectiveness in such cooling applications.

In embodiments, the disclosed wood may be adapted for use in various applications, wherein the mechanical and thermal properties of the material are tailored to suit a particular application. For example, fig. 10A shows a building structure 1000, wherein embodiments of the disclosed lumber may be used as one or more exterior components of the structure 1000. For example, wood may form part of roof 1002, wall panel 1004, or any other component of structure 1000.

When the wood is designed to be self-supporting and provide insulation, the wood for roof 1002, siding 1004, or other components may be partially pressed delignified wood that exhibits a mixture of thermal insulation properties and improved mechanical strength. When the wood is designed to be supported by other structures (e.g., as described below with respect to fig. 10B), the wood used for roof 1002, siding 1004, or other components may be unpressed or minimally pressed (i.e., less than 20% reduction in thickness) delignified wood that exhibits excellent thermal insulation, but at the expense of lower mechanical strength. When the wood is designed to optimize passive cooling, the wood for roof 1002, wall panels 1004, or other components may be partially densified delignified wood or densified delignified wood having improved thermal conductivity compared to non-pressed delignified wood, allowing heat from the back side of the wood in thermal communication with a heat source to be transferred through the wood for emission to the sky. Furthermore, the increased tensile and compressive strength of the densified wood may allow the densified wood to be used as an external component of the structure 1000 without separate mechanical support. Wood in the building structure 1000, whether uncompressed, densified, or partially densified, can have optical properties that act to reflect incident solar radiation 1006 and thereby minimize or at least reduce heating of the structure 1000 due to absorption of the solar radiation 1006.

In embodiments, for example, the disclosed wood may form a composite structure 1022, as shown in fig. 10B. For example, various disclosed woods with different thermal or mechanical properties may be combined together, or a particular wood may be combined with other types of materials to form a composite structure. As shown in fig. 10B, composite structure 1022 includes a plurality of layers 1010-1014 separating internal environment 1016 from external environment 1018.

For example, the outermost layer 1010 may be formed of densified delignified wood or partially densified delignified wood to provide structural support. The unique optical properties of delignified wood may also allow the outermost layer 1010 to effectively reflect 1020 incident solar radiation 1006, thereby minimizing heating due to solar absorption and potentially providing passive cooling as described above. For example, the innermost layer 1014 may be formed of partially densified delignified wood to provide structural support and insulation, and the middle layer 1012 may be formed of minimally densified (e.g., < 20% of original thickness) delignified wood or uncompressed delignified wood to provide excellent insulation while relying on the outer layer 1010 and the inner layer 1014 for structural support. Thus, any heating caused by solar radiation 1006 may be isolated to the outermost layer 1010, which outermost layer 1010 may cool itself by passive cooling, and the internal environment 1016 may be effectively isolated from the external environment 1018 by the multi-layer isolation provided by the intermediate layer 1012 and the internal layer 1014.

Other configurations and material selections of composite structure 1022, in addition to those explicitly discussed above, are possible according to one or more contemplated embodiments. For example, the orientation of the layers of the composite structure relative to the tree growth direction 206 may be different from one another (e.g., as described below with respect to fig. 17A-17C). Alternatively or additionally, wood may be combined with other types of materials (such as natural wood, processed wood, partially delignified and/or densified wood, drywall, metal, or other building materials) to form composite structures.

Although only three layers are shown in fig. 10B, the disclosed embodiments of the number of layers are not limited to the number of layers shown. Rather, two or more layers are possible according to one or more contemplated embodiments. For example, two or more delignified wood pieces 1702a, 1702b (which may be wood pieces, wood chips, or wood pieces of different sizes/shapes) may be combined together to form a laminated unit 1704, which itself may be combined with other laminated units to form a multilayer laminate 1706, as shown in fig. 17A-17C. The lamination units 1704 may be designed to enhance the anisotropy of the thermal and mechanical properties of the underlying wood, for example by orienting the respective wood directions 206a, 206b, or to reduce the anisotropy, for example by intentionally traversing the wood directions 206a, 206b (as shown in fig. 17A-17C) or providing a random orientation of the wood directions 206a, 206 b.

The wood pieces 1702a, 1702b may be joined together by glue or epoxy or by hydrogen bonding. The wood pieces 1702a, 1702b may be joined together prior to pressing to achieve densification, or as part of pressing for densification when densification is desired, or after delignification when densification is not desired. For example, in those embodiments that use hydrogen bonding, joining may include pressing the oriented pieces 1702a, 1702b together under high pressure, similar to the pressing used to form a densified wood piece. In other embodiments, the joining of the wood pieces may be combined with pressing to densify the wood pieces. Thus, the pressing effectively compresses each wood piece (i.e., produces a densified delignified wood piece) and results in the formation of hydrogen bonds between opposing surfaces of the wood piece.

Although rinsing, drying, pre-press modification, humidifying, and post-press modification are not separately illustrated in fig. 17A-17C, it is to be understood that these embodiments may also include features of the method 100 of fig. 1. Further, although a particular number of densified delignified woods for a laminate structure are shown in fig. 17A-17C, other numbers of densified delignified woods are possible according to one or more contemplated embodiments.

Further, the laminating unit 1704 can be formed from a combination of different woods and the disclosed delignified woods. For example, one component of the laminate may be densified delignified wood, a second component may be uncompressed delignified wood, and a third component may be partially densified delignified wood, such as described above with respect to fig. 10B. In another example, one component of the laminate may be densified delignified wood and the other component may be natural wood, uncompressed partially delignified wood, or partially delignified densified wood. Other configurations are also possible according to one or more contemplated embodiments.

Further, although rectangular shapes are shown in fig. 17A-17C, other shapes are possible according to one or more contemplated embodiments. In practice, the wood chips may have an irregular or different shape/size before being combined into the laminate structure.

In other embodiments, the orientations 206a, 206b of the joined wood pieces 1702a, 1702b may be at non-orthogonal angles relative to each other. Thus, the first piece 1702a can be coupled to the second piece 1702b such that the orientation direction 206a of the first piece intersects only the orientation direction 206b of the second piece in plan view. Additionally, other alignments and orientations besides those shown in fig. 17A-17C are possible according to one or more contemplated embodiments. In some embodiments, the orientation of adjacent sheets may be oriented, for example, to enhance anisotropy.

Although fig. 10A-10B and 17A-17C have been discussed with respect to structural members for a building, embodiments of the disclosed subject matter are not so limited. Rather, the disclosed wood may be adapted for use in a variety of applications other than building structures, such as, but not limited to, packaging, ornamentation (e.g., a unique visual appearance provided by white and underlying wood structures), and electrical devices.

For example, fig. 14 illustrates an electrical device 1400 that employs delignified wood 1402 (whether uncompressed, partially densified, or densified) as a substrate for supporting one or more electronic components 1406. Especially when the delignified wood 1402 has undergone a certain degree of densification, the top surface 1404 may have a low surface roughness, e.g. 10nm or less, which allows the electronic component 1406 to be formed directly on the delignified wood 1402. The wood surface 1404 is also naturally electrically insulating, allowing the electronic component 1406 to be formed directly thereon. Alternatively, an intermediate layer may be formed on the wood surface 1404, and the electronic component 1406 may be formed on the intermediate layer. Thus, the electrical circuit can be considered to be integrated with delignified wood. For example, the display device may be an integral part of delignified wood forming a wall in a building.

The electronic components 1406 may include one or more of transistors, capacitors, resistors, inductors, electrical conductors, electrical insulators, and energy storage components (e.g., batteries), and may form one or more desired circuits. For example, the electronic component 1406 may form a display device. Other electronic devices integrated with the disclosed delignified wood are also possible according to one or more embodiments, including but not limited to integrated sensors and input/output interfaces.

Although the above discussion has focused on wood having an extension direction 206 perpendicular to the thickness direction (where the thickness t is considered to be the smallest dimension of the wood), it is also possible for the wood to have a different extension direction 206. For example, as shown in fig. 15, the extension direction 206 is along (i.e., substantially parallel to) the thickness direction and is substantially perpendicular to the top surface 1502 and the bottom surface 1504. Thus, the axial thermal conductivity 408 between the top surface 1502 and the bottom surface 1504 is higher than the lateral thermal conductivity 410 in a plane parallel to the top surface 1502 and the bottom surface 1504. Such a configuration may be advantageous in certain applications, such as in passive cooling applications, where it is desirable to transfer heat from the back surface 1504 to the front surface 1502 for emission.

Further, the orientation of the extension direction 206 may be at an angle other than 0 ° or 90 ° with respect to the outer surface of the wood. For example, fig. 16 shows an example where a wood 1600 has an extension direction 206 at a non-zero angle with respect to a top surface 1602 and a bottom surface 1604. When the extension direction 206 is angled as shown in fig. 16 or otherwise, the press 502 used to effect densification may also be angled relative to the outer surface (as shown) or relative to the extension direction 206 (not shown) to facilitate reorientation of the orientation of the cellulose nanofibers.

In one or more first embodiments, a structure includes a first natural wood piece that has been chemically treated to remove lignin from the natural wood while substantially preserving the structure of the cellulose-based cavities of the natural wood. At least 90% of the lignin in the natural wood has been removed by the chemical treatment.

In a first embodiment or any other embodiment, the lignin in the first piece is less than 5 wt.%, less than or equal to 1 wt.%, or less than or equal to 0.6 wt.%.

In the first embodiment or any other embodiment, the first piece has an axial thermal conductivity in a direction of extension of the cavity and a lateral thermal conductivity in a direction perpendicular to the direction of extension of the cavity, and the axial thermal conductivity is greater than the lateral thermal conductivity. In the first embodiment or any other embodiment, the axial thermal conductivity is at least two times greater than the lateral thermal conductivity, the axial thermal conductivity is at least five times greater than the lateral thermal conductivity, or the axial thermal conductivity is at least ten times greater than the lateral thermal conductivity. In the first embodiment or any other embodiment, the lateral thermal conductivity is less than 0.2W/m-K, less than 0.1W/m-K, or less than 0.05W/m-K.

In the first embodiment or any other embodiment, the first piece has an emissivity of at least 0.8 in the wavelength range of 8 μm to 13 μm, or at least 0.9 in the wavelength range of 8 μm to 13 μm.

In a first embodiment or any other embodiment, the first part has an absorbance of less than or equal to 10% in the wavelength range of 400nm to 1100nm, or less than or equal to 8% in the wavelength range of 400nm to 1100 nm.

In the first embodiment or any other embodiment, the first emissivity of said first member in the wavelength range of 400-1100nm is less than the second emissivity of said first member in the wavelength range of 8-13 μm. In the first embodiment or any other embodiment, the second emissivity is at least 3 times, at least 5 times, at least 8 times, or at least 10 times the first emissivity. In the first embodiment or any other embodiment, the second emissivity is at least 0.8 and the first emissivity is less than or equal to 0.1.

In the first embodiment or any other embodiment, the cellulose nanofibres in the first piece are oriented substantially along the extension direction of the cavity. In a first embodiment or any other embodiment, the first piece has nanopores between the oriented cellulose nanofibers. In the first embodiment or any other embodiment, the interior volume of the cellulose-based lumen of the first piece is open or unobstructed.

In a first embodiment or any other embodiment, the first piece has increased flexibility compared to the natural wood prior to the chemical treatment. In the first embodiment or any other embodiment, the first piece has a bend radius at least two times smaller than the bend radius of the natural wood before the chemical treatment.

In the first embodiment or any other embodiment, the cavity extends perpendicular to a thickness direction of the first member. In the first embodiment or any other embodiment, the cavity extends in a thickness direction of the first member. In the first embodiment or any other embodiment, a dimension of the first piece in a direction perpendicular to the thickness direction is larger than a thickness of the first piece in the thickness direction.

In the first embodiment or any other embodiment, the thickness of the first piece is less than or equal to 1 mm.

In a first embodiment or any other embodiment, the chemically treated wood of the first piece has been pressed in a first direction crossing the direction of extension of the cavities, such that the cavities are at least partially collapsed. In the first embodiment or any other embodiment, the thickness of the first piece in the first direction is reduced by not more than 40% compared to the thickness of the natural wood, or by not more than 20% compared to the thickness of the natural wood. In a first embodiment or any other embodiment, the thickness of the first piece in the first direction is reduced by at least 40% compared to the thickness of the natural wood, or by at least 80% compared to the thickness of the natural wood.

In a first embodiment or any other embodiment, said first piece has an increased density compared to said natural wood prior to said chemical treatment. In a first embodiment or any other embodiment, the density of said first piece is at least two times greater than the density of said natural wood prior to said chemical treatment.

In the first embodiment or any other embodiment, the surface roughness of the first piece is 10nm or less.

In a first embodiment or any other embodiment, the mechanical properties of the first piece are improved compared to the mechanical properties of the natural wood before the chemical treatment. In a first embodiment or any other embodiment, the specific tensile strength of the first part is at least 200MPa-cm³Per g, at least 300MPa-cm³In g, or at least 330MPa-cm³/g。

In the first embodiment or any other embodiment, the structure further comprises a second natural wood piece that has been chemically treated to remove lignin from the natural wood while substantially preserving the structure of the cellulose-based cavities of the natural wood. At least 90% of the lignin in the natural wood has been removed by the chemical treatment, and the first and second pieces are coupled to each other along facing surfaces. The direction of extension of the cavity of the first part intersects the direction of extension of the cavity of the second part. In the first embodiment or any other embodiment, the direction of extension of the cavity of the first piece is orthogonal to the direction of extension of the cavity of the second piece. In the first embodiment or any other embodiment, the first piece and the second piece are coupled to each other by at least one of hydrogen bonding, glue, and epoxy. In the first embodiment or any other embodiment, each of the first and second pieces is formed as a plate, a block, a bar, a hollow shape, a film having a thickness of less than 200 μm, a wood chip, or a wood shaving. In the first embodiment or any other embodiment, the chemically treated natural wood of the first and second pieces has been pressed in a direction crossing the respective direction of extension of the cavities therein, such that the cavities are at least partially collapsed.

In a first embodiment or any other embodiment, said first piece consists essentially of said chemically-treated natural wood.

In a first embodiment or any other embodiment, the first member is hydrophobic. In the first embodiment or any other embodiment, the first member exhibits a static contact angle of at least 90 °, or a dynamic contact angle of less than 10 °. In a first embodiment or any other embodiment, the first piece has been chemically treated to be hydrophobic, and the chemical treatment comprises at least one of: epoxy resin, silicone oil, polyurethane, paraffin emulsion, acetic anhydride, Octadecyltrichlorosilane (OTS), 1H,2H, 2H-perfluorodecyltriethoxysilane, fluororesin, Polydimethylsiloxane (PDMS), Methacryloxymethyltrimethylsilane (MSi), polyhedral oligomeric silsesquioxane (POSS), Potassium Methylsiliconate (PMS), dodecyl (trimethoxy) silane (DTMS), hexamethyldisiloxane, dimethyldiethoxysilane, tetraethoxysilane, methyltrichlorosilane, ethyltrimethoxysilane, methyltriethoxysilane, trimethylchlorosilane, phenyltrimethoxysilane, phenyltriethoxysilane, propyltrimethoxysilane, polymethyl methacrylate, polydiallyldimethylammonium chloride (polyDADMAC), 3- (trimethoxysilyl) propyl Methacrylate (MPS), Hydrophobic stearic acid, amphiphilic fluorinated triblock azide copolymer, polyvinylidene fluoride and fluorosilane, n-dodecyl trimethoxysilane, and sodium dodecyl sulfate.

In the first embodiment or any other embodiment, the first piece has been chemically treated to be weather resistant or brine resistant. In a first embodiment or any other embodiment, the chemical treatment for achieving weather or salt water resistance comprises at least one of: copper dimethyldithiocarbamate (CDDC), ammoniated quaternary Ammonium Copper (ACQ), Copper Chromide Arsenate (CCA), Ammoniated Copper Zinc Arsenate (ACZA), copper naphthenate, copper acid chromate, copper citrate, copper azole, copper 8-hydroxyquinoline, pentachlorophenol, zinc naphthenate, copper naphthenate, creosote, titanium dioxide, propiconazole, tebuconazole, cyproconazole, boric acid, borax, organic Iodide (IPBC), and Na₂B₈O₁₃·4H₂O。

In the first embodiment or any other embodiment, the structure further comprises a coating on one or more exterior surfaces of the first piece. In the first embodiment or any other embodiment, the coating comprises an oil-based coating, a hydrophobic coating, a polymeric coating, or a fire resistant coating. In a first embodiment or any other embodiment, the refractory coating comprises at least one of: boron nitride, montmorillonite, hydrotalcite, silicon dioxide (SiO)₂) Sodium silicate, calcium carbonate (CaCO)₃) Aluminum hydroxide (Al (OH)₃) Magnesium hydroxide (Mg (OH)₂) Magnesium carbonate (MgCO)₃) Aluminum sulfate, ferric sulfate, zinc borate, boric acid, borax, triphenyl phosphate (TPP), melamine, polyurethane, ammonium polyphosphate, phosphate ester, phosphite ester, ammonium phosphate, ammonium sulfate, phosphonate esterDiammonium phosphate (DAP), monoammonium phosphate (MAP), guanylurea phosphate (GUP), guanidine dihydrogen phosphate, and antimony pentoxide.

In a first embodiment or any other embodiment, the first piece is white. In a first embodiment or any other embodiment, the first piece has been dyed a color other than white.

In the first embodiment or any other embodiment, the structure further comprises a heat source in thermal communication with the first piece, and the first piece is exposed to radiate heat from the heat source to the sky. In the first embodiment or any other embodiment, the exposed surface of the first piece is substantially parallel to the direction of extension of the cavity.

In the first embodiment or any other embodiment, the structure further comprises an electrical component formed over a surface of the first piece. In the first embodiment or any other embodiment, the electrical component includes at least one of a transistor, a capacitor, a resistor, and an inductor.

In one or more second embodiments, the structure is formed by removing at least 90% of the lignin from the natural wood piece while substantially retaining the cellulose-based cavities.

In one or more third embodiments, the structure is formed by removing at least 90% of the lignin from the natural wood piece while substantially retaining the cellulose-based cavities, and then pressing to at least partially collapse the cavities.

In a third or any other embodiment, the thickness of the piece after pressing is reduced by at least 40% compared to the thickness of the natural wood, or by at least 80% compared to the thickness of the natural wood. In a third or any other embodiment, the thickness of the piece after pressing is reduced by no more than 40% compared to the thickness of the natural wood, or by no more than 20% compared to the thickness of the natural wood.

In the second embodiment, the third embodiment, or any other embodiment, the piece has less than or equal to 5 wt% lignin therein, or less than or equal to 1 wt% lignin therein.

In the second embodiment, the third embodiment, or any other embodiment, the piece has an anisotropic thermal conductivity.

In the second embodiment, the third embodiment, or any other embodiment, the article absorbs less than or equal to 10% of the solar radiation and has an emission greater than or equal to 90% in the atmospheric transmission window.

In the second embodiment, the third embodiment, or any other embodiment, the member is hydrophobic.

In the second, third, or any other embodiment, the piece is joined together with another natural wood piece from which at least 90% of the lignin has been removed to form a laminate.

In the second embodiment, the third embodiment, or any other embodiment, the piece is substantially white.

In one or more fourth embodiments, a method includes removing at least 90% of lignin from a natural wood piece while substantially preserving a cellulose-based cavity of the natural wood, thereby producing a delignified wood piece.

In a fourth embodiment or any other embodiment, the delignified wood is substantially white.

In a fourth or any other embodiment, the removing comprises immersing the natural wood piece in a chemical solution comprising at least one of: NaOH and Na₂S、NaHSO₃、SO₂,、H₂O、Na₂SO₃Anthraquinone (AQ), Na₂S_n(wherein n is an integer), CH₃OH、C₂H₅OH、C₄H₉OH、HCOOH、NH₃、p-TsOH、NH₃-H₂O、H₂O₂、NaClO、NaClO₂、CH₃COOH (acetic acid), ClO₂And Cl₂。

In a fourth or any other embodiment, the removing includes immersing the natural wood piece in a first chemical solution and then in a second chemical solution. In a fourth embodiment or any other embodiment, the first chemical solution comprises NaOH and Na₂SO₃And the second chemical solution comprises H₂O₂。

In a fourth embodiment or any other embodiment, the method further comprises at least one of the following steps: (a) drying the delignified piece of wood by freeze-drying or critical point drying after the removing such that the cellulose-based cavity remains open or unobstructed in a cross-sectional view; (b) after the removing, rinsing the delignified wood to remove residual chemicals from the removing; (c) drying the delignified piece of wood after the rinsing; (d) exposing the delignified wood to a relative humidity of 90% for a first period of time after the rinsing; (e) pressing the delignified wood; (f) subjecting the wood to a hydrophobic treatment before or after said pressing; (g) dyeing the delignified wood to a color other than white; (h) chemically treating the delignified wood to render it weather resistant or salt water resistant; and (i) coating the surface of the delignified wood.

In a fourth embodiment or any other embodiment, the solution used for the rinsing comprises at least one of ethanol and Deionized (DI) water.

In a fourth embodiment or any other embodiment, the pressing reduces the thickness of the wood by between 0% and 40%, or between 0% and 20%, inclusive. In a fourth or any other embodiment, the pressing reduces the thickness of the wood by at least 40%, or at least 80%. In a fourth or any other embodiment, the pressing is performed at a temperature of 20-120 ℃ and a pressure of 0.5-10 MPa. In a fourth or any other embodiment, a microfiltration membrane or filter paper is disposed on the surface of the delignified wood prior to or during the pressing. In a fourth or any other embodiment, the pressing is performed in a direction crossing the direction of extension of the cellulose-based cavities. In a fourth or any other embodiment, the surface roughness of the delignified wood after the pressing is 10nm or less.

In a fourth or any other embodiment, the hydrophobic treatment comprises at least one of: epoxy resin, silicone oil, polyurethane, paraffin emulsion, acetic anhydride, Octadecyltrichlorosilane (OTS), 1H,2H, 2H-perfluorodecyltriethoxysilane, fluororesin, Polydimethylsiloxane (PDMS), Methacryloxymethyltrimethylsilane (MSi), polyhedral oligomeric silsesquioxane (POSS), Potassium Methylsiliconate (PMS), dodecyl (trimethoxy) silane (DTMS), hexamethyldisiloxane, dimethyldiethoxysilane, tetraethoxysilane, methyltrichlorosilane, ethyltrimethoxysilane, methyltriethoxysilane, trimethylchlorosilane, phenyltrimethoxysilane, phenyltriethoxysilane, propyltrimethoxysilane, polymethyl methacrylate, polydiallyldimethylammonium chloride (polyDADMAC), 3- (trimethoxysilyl) propyl Methacrylate (MPS), Hydrophobic stearic acid, amphiphilic fluorinated triblock azide copolymer, polyvinylidene fluoride and fluorosilane, n-dodecyl trimethoxysilane, and sodium dodecyl sulfate.

In a fourth or any other embodiment, the hydrophobic treatment is performed prior to the compressing and comprises 1H, 2H-perfluorodecyltriethoxysilane.

In a fourth or any other embodiment, the chemical treatment for achieving weather or salt water resistance comprises at least one of: copper dimethyldithiocarbamate (CDDC), ammoniated quaternary Ammonium Copper (ACQ), Copper Chromite Arsenate (CCA), Ammoniated Copper Zinc Arsenate (ACZA), copper naphthenate, acidic copper chromate, copper citrate, copper azole, copper 8-hydroxyquinoline, pentachlorophenol, naphtheneZinc, copper naphthenate, creosote, titanium dioxide, propiconazole, tebuconazole, cyproconazole, boric acid, borax, organic Iodide (IPBC), and Na₂B₈O₁₃·4H₂O。

In a fourth embodiment or any other embodiment, the coating comprises an oil-based coating, a hydrophobic coating, a polymeric coating, or a fire resistant coating.

In a fourth or any other embodiment, the refractory coating comprises at least one of: boron nitride, montmorillonite, hydrotalcite, silicon dioxide (SiO)₂) Sodium silicate, calcium carbonate (CaCO)₃) Aluminum hydroxide (Al (OH)₃) Magnesium hydroxide (Mg (OH)₂) Magnesium carbonate (MgCO)₃) Aluminum sulfate, ferric sulfate, zinc borate, boric acid, borax, triphenyl phosphate (TPP), melamine, polyurethane, ammonium polyphosphate, phosphate ester, phosphite, ammonium phosphate, ammonium sulfate, phosphonate, diammonium phosphate (DAP), monoammonium phosphate (MAP), guanylurea phosphate (GUP), guanidine dihydrogen phosphate, and antimony pentoxide.

In a fourth embodiment or any other embodiment, the method further comprises disposing the delignified wood piece such that a surface thereof radiates heat skyward. In a fourth embodiment or any other embodiment, the surface is substantially parallel to the direction of extension of the cavity.

In a fourth or any other embodiment, the method further comprises forming the delignified wood piece into a building material, a packaging material, or other structural material.

In a fourth embodiment or any other embodiment, the method further comprises forming one or more electrical components on a surface of the delignified wood piece.

In a fourth embodiment or any other embodiment, the method further comprises using the delignified wood piece to radiate energy to cool a structure or environment. In a fourth embodiment or any other embodiment, the cooling is passive cooling. In a fourth or any other embodiment, the delignified wood piece has a first emissivity in the wavelength range of 400-. In a fourth embodiment or any other embodiment, the second emissivity is at least 3 times, at least 5 times, at least 8 times, or at least 10 times the first emissivity. In a fourth embodiment or any other embodiment, the second emissivity is at least 0.8 and the first emissivity is less than or equal to 0.1.

In a fourth embodiment or any other embodiment, the delignified wood piece radiates energy in excess of the energy it absorbs. In a fourth embodiment or any other embodiment, the thermal conductivity of the delignified wood piece is anisotropic. In a fourth embodiment or any other embodiment, the thermal conductivity of the delignified piece of wood in a direction parallel to the exposed surface of the delignified wood is greater than the thermal conductivity of the delignified piece of wood in a direction perpendicular to the exposed surface.

In a fourth embodiment or any other embodiment, the method further comprises removing at least 90% of the lignin from another piece of natural wood while substantially preserving the cellulose-based cavities of the natural wood, thereby producing another delignified piece of wood, and coupling a surface of the delignified piece with a surface of the other delignified piece of wood. In the fourth embodiment or any other embodiment, an extending direction of the cavity of the delignified wood piece intersects with an extending direction of the cavity of the other delignified wood piece. In the fourth embodiment or any other embodiment, the delignified wood piece and the other delignified wood piece are coupled to each other by at least one of hydrogen bonding, glue and epoxy.

In a fourth or any other embodiment, the method comprises pressing the delignified wood piece and the further delignified wood piece in a direction crosswise to the respective direction of extension of the cavity therein, such that the cavity is at least partially collapsed, before or after the coupling.

In the first through fourth embodiments or any other embodiment, the natural wood comprises hardwood, softwood, or bamboo. In the first through fourth embodiments or any other embodiment, the natural wood comprises basswood, oak, poplar, ash, alder, aspen, balsa, beech, birch, cherry, white walnut, chestnut, sandalwood, elm, hickory, maple, oak, rosewood, plum, walnut, willow, cottonwood, larch, fir, cypress, douglas fir, hemlock, larch, pine, redwood, spruce, larch, juniper, or yew.

In one or more fifth embodiments, the active or passive cooling device comprises a structure according to any one of the first to fourth embodiments or any other embodiment.

In one or more sixth embodiments, the release material comprises a structure according to any one of the first to fifth embodiments or any other embodiment.

In one or more seventh embodiments, an electronic device includes a structure according to any one of the first to sixth embodiments or any other embodiment. In a seventh embodiment or any other embodiment, at least one electrical component is formed over a surface of the structure. In a seventh embodiment or any other embodiment, the electronic device is configured as a display panel.

In one or more eighth embodiments, the packaging material comprises a structure according to any one of the first to seventh embodiments or any other embodiment.

In one or more ninth embodiments, the building material comprises a structure according to any one of the first to eighth embodiments or any other embodiment. In a ninth embodiment or any other embodiment, the building material is configured as an exterior surface of a building. In a ninth embodiment or any other embodiment, the exterior surface is at least one of a roof and a wall panel of the building.

In one or more tenth embodiments, the material comprises a structure according to any one of the first to ninth embodiments or any other embodiment. In a tenth embodiment or any other embodiment, the material is formed into an interior or exterior component of an automobile, train, truck, airplane, ship, boat or any other means of transportation, vehicle or vehicle, warehouse, factory, office building, barn, home or any other building or structure. In a tenth or any other embodiment, the material is formed as part of: a container, box, or shipping crate; a display, an ornament, a window frame, a picture frame, a door or door frame, a table, a desk, a chair, a cabinet, a wardrobe, a bed, or any other piece of furniture or home furnishing; a bridge, dock, deck or platform; musical instruments; a shield, explosion proof shield, or other protective device; a tool, a sporting equipment, or a sporting good.

In this application, the use of the singular includes the plural and the separate use of "or" and "includes the other, i.e.," and/or, "unless expressly stated otherwise. Furthermore, the use of the terms "including" or "having," as well as other forms (such as "including," "containing," or "having") are intended to have the same effect as "comprising," and therefore should not be construed as limiting.

Any range recited herein is to be understood as including the endpoints and all values between the endpoints. Unless expressly stated otherwise, whenever "substantially," "about," "substantially," "approximately," or similar language is used in combination with a particular value, it is intended to mean up to and including 10% variation of that value.

In some cases, the foregoing description applies to examples generated in the laboratory, but these examples may be extended to production techniques. Thus, where numbers and techniques are applicable to laboratory examples, they are not to be construed as limiting.

Thus, it is apparent that there is provided in accordance with the present disclosure delignified wood, as well as methods of making and using the same. The present disclosure is susceptible to many alternatives, modifications, and variations. While specific examples have been shown and described in detail to illustrate the application of the principles of the invention, it will be understood that the invention may be embodied otherwise without departing from such principles. For example, the disclosed features can be combined, rearranged, omitted, etc., to produce additional embodiments, and some of the disclosed features can sometimes be used to advantage without a corresponding use of the other features. Accordingly, the applicant intends to embrace all such alternatives, modifications, equivalents and variations as fall within the spirit and scope of the present invention.