阅读说明：本技术 陶瓷泡沫、其制造方法及其用途 (Ceramic foam, method for the production thereof and use thereof ) 是由 任申强 杨睿哲 柴秉伯 胡峰 于 2020-01-13 设计创作，主要内容包括：提供陶瓷泡沫。陶瓷泡沫可具有分级孔梯度。陶瓷泡沫可以是氧化硅气凝胶。可通过一种或多种前体在由成孔气体形成添加剂产生的惰性气体存在下进行反应来制备陶瓷泡沫。陶瓷泡沫可以用作隔绝材料。(A ceramic foam is provided. The ceramic foam may have a graded pore gradient. The ceramic foam may be a silica aerogel. Ceramic foams may be prepared by reacting one or more precursors in the presence of an inert gas generated by a pore-forming gas-forming additive. Ceramic foams may be used as insulation.)

1. A method for forming a ceramic foam, the method comprising:

contacting in a sealed environment:

one or more ceramic precursors;

one or more pore-forming gas-forming additives;

one or more catalysts; and

optionally, one or more additives,

wherein the contacting results in the formation of an inert gas and the formation of a ceramic foam.

2. The method of claim 1, wherein the contacting is performed at an initial pressure of 1-100psi before substantial reaction of the one or more ceramic precursors and/or the one or more pore forming gas forming additives and/or the one or more additives, if present.

3. The method of claim 1, wherein the one or more ceramic precursors are selected from the group consisting of silicon oxide precursors, aluminum oxide precursors, transition metal oxide precursors, and combinations thereof.

4. The method of claim 3, wherein the silicon oxide precursor is selected from the group consisting of: tetraalkoxysilanes, alkyltrialkoxysilanes, sodium metasilicate, alkyls, and combinations thereof.

5. The method of claim 3, wherein the alumina precursor is selected from the group consisting of: aluminum alkoxides, tris (beta-hydroxy) ethylamine condensed aluminum hydroxide, or tris (aluminum triazoxide tricyclooxyisopropyl) amine, and combinations thereof.

6. The method of claim 3, wherein the transition metal oxide precursor is selected from transition metal alkoxides.

7. The method of claim 1, wherein the one or more catalysts is a basic catalyst.

8. The process of claim 7, wherein the basic catalyst is selected from the group consisting of: ammonia, ammonium fluoride, ammonium hydroxide, urea, cetyltrimethylammonium bromide, and combinations thereof.

9. The method of claim 1, wherein the one or more catalysts are acidic catalysts.

10. The process of claim 9 wherein the acidic catalyst is selected from the group consisting of: protic acids, hydrohalic acids, and combinations thereof.

11. The method of claim 1, wherein the one or more pore-forming gas-forming additives are selected from the group consisting of: sodium bicarbonate, urea, and combinations thereof.

12. The method of claim 1, wherein the one or more additives are selected from the group consisting of: cetyl trimethylammonium bromide (CTAB)), urea, and combinations thereof.

13. The method of claim 1, wherein one or more ceramic precursors, one or more pore forming gas forming additives, and optionally one or more additives are contacted, and then one or more catalysts are contacted with the one or more ceramic precursors, the one or more pore forming gas forming additives, and optionally one or more additives.

14. The method of claim 1, wherein contacting comprises mixing:

one or more ceramic precursors, which may be disposed in water, a solvent, or a combination thereof;

one or more pore-forming gas-forming additives, which may be disposed in water;

one or more catalysts, which may be disposed in water.

15. The method of claim 1, wherein the one or more ceramic precursors are each present in an amount of 2 to 10 wt%, based on the total weight of the ceramic precursors, catalysts, pore-forming gas forming additives, and additives (if present).

16. The method of claim 1, wherein the one or more pore-forming gas-forming additives are present in an amount of 0.4 to 2 wt.%, based on the total weight of the ceramic precursor, catalyst, pore-forming gas-forming additive, and additive (if present).

17. The method of claim 1, wherein the one or more catalysts are present in an amount of 1 to 2 wt%, based on the total weight of the ceramic precursor, catalyst, pore-forming gas former, and additives (if present).

18. The method of claim 1, wherein the one or more additives are present in an amount of 200 to 1000 wt.%, based on the total weight of the ceramic precursor, catalyst, pore-forming gas forming additive.

19. The method of claim 1, wherein the ratio of ceramic precursor to pore forming gas forming additive to catalyst to additive is 5:1:1: 50.

20. The method of claim 1, wherein contacting is performed at a temperature of room temperature to 70 ℃, and/or for 1 minute to 96 hours.

21. The method of claim 1, the method comprising: exchanging material from the ceramic foam.

22. The method of claim 1, further comprising: the ceramic foam is washed.

23. The method of claim 22, wherein washing comprises: the ceramic foam is contacted with an aqueous solution.

24. The method of claim 1, further comprising: the ceramic foam is washed with alcohol and/or dried.

25. The method of claim 1, further comprising: forming a hydrophobic carbon-containing material layer disposed on at least a portion or all of a surface of the ceramic foam.

26. The method of claim 1, the method comprising: the film is formed from a ceramic foam.

27. The method of claim 26, wherein the thin film is formed on a substrate.

28. The method of claim 26, wherein forming is a continuous process.

29. The method of claim 26, wherein forming is performed by doctor blading, drop die casting, or additive manufacturing.

30. The method of claim 26, wherein the film is formed by spray coating of a gelled form of a reaction mixture comprising one or more ceramic precursors, one or more pore-forming gas forming additives, one or more catalysts, and optionally one or more additives.

31. The method of claim 1, further comprising: the substrate is impregnated with a ceramic foam.

32. The method of claim 1, further comprising: at least a portion of the surface of the ceramic foam is painted or coated.

33. The method of claim 32, wherein the ceramic foam is painted or coated with a material.

34. The method of claim 33, wherein the material is one or more nanoparticles.

35. The method of claim 34, wherein the nanoparticles are formed by impregnating a ceramic foam with a nanoparticle precursor and forming a nanocomposite.

36. A ceramic foam comprising pores and a graded pore gradient, wherein at least some or all of the pores are interconnectable.

37. The ceramic foam of claim 36, wherein the pore size decreases or increases generally along a dimension moving from a first surface of the ceramic foam to a second surface opposite the first surface.

38. The ceramic foam of claim 36, wherein the ceramic foam comprises a ceramic matrix.

39. The ceramic foam of claim 36, wherein the pore size is 500 microns to 1 micron.

40. The ceramic foam of claim 36, wherein the ceramic foam is of the silica aerogel type and is transparent.

41. The ceramic foam of claim 36, wherein 90-99% of the ceramic foam is air.

42. The ceramic foam of claim 36, wherein the porosity of the ceramic foam is less than 100 nm.

43. The ceramic foam of claim 36,the density of the ceramic foam is about 0.003g/cm³。

44. The ceramic foam of claim 36, wherein the ceramic foam has a thermal conductivity of about 0.017W/mK.

45. The ceramic foam of claim 36, wherein the ceramic foam comprises a layer of carbonaceous material disposed on at least a portion or all of a surface of the ceramic foam.

46. The ceramic foam of claim 36, wherein the ceramic foam further comprises nanoparticles disposed on at least a portion of a surface of the ceramic foam.

47. The ceramic foam of claim 36, wherein the ceramic foam is a monolith, a free-standing film, or a film disposed on at least a portion of a substrate or all of a substrate.

48. The ceramic foam of claim 47, wherein the membrane has a thickness of 1/4 inches to 2 inches.

49. The ceramic foam of claim 47 wherein the film is disposed on at least a portion of a surface of the substrate.

50. The ceramic foam of claim 36, wherein the ceramic foam exhibits a thermal stability of at least up to 2000 ℃.

51. The ceramic foam of claim 36, wherein the ceramic foam exhibits a mechanical strength of at least 100 Mpa.

52. The ceramic foam of claim 36, wherein the ceramic foam exhibits sound insulating/sound isolating properties.

53. A ceramic foam impregnated substrate wherein the porosity of the impregnated substrate is greater than 100 nm.

54. A ceramic foam impregnated substrate wherein the impregnated substrate has an electrical conductivity of 0.017W/mK or less.

Background

The search for lightweight and mechanically strong superinsulation (thermal and acoustic insulation) is key to energy efficient construction and many other industries, and low cost manufacturing with scalability is indispensable for large scale, practical and energy efficient applications.

HVAC (heating, ventilation and air conditioning) of a building accounts for 40% of the global energy consumption. HVAC for existing and future buildings can be improved by installing improved insulation to reduce CO₂And (5) discharging. An economical way to reduce the heat consumption of a building is to install a thicker layer of insulating material. However, it takes up more space and thus living space is reduced. The silica aerogel only needs half the thickness of the insulating material conventionally installed to achieve the same insulating properties. Silica aerogel exhibits the lowest thermal conductivity of known solids at ambient temperature, pressure and relative humidity, about 0.015W/m-K. This low thermal conductivity results from a combination of its low density and porosity created during manufacture. In the construction industry, space saving is one of the most important reasons for the use of high performance insulation for building renovation and thin facade insulation, side box and roof balcony construction. The major disadvantage of using silica aerogel on a large scale as a standard insulation in construction is its production cost.

Superinsulation requires strict regulation of heat transfer. Silica aerogel is one of the most effective thermal insulation materials in this case, and can even reach ultra low thermal conductivity below that of still air. Superinsulation of ceramic aerogels results from the geometry of the porous material, including high pore volume, optimized void size and porous solid walls with boundaries and defects, where the low solid fraction heat transfer dissipation path under the limited heat conduction and phonon scattering of the gas voids contributes to their good thermal insulation performance. Despite the superior insulating properties, large-scale silica aerogel applications have been limited because they are manufactured by supercritical drying (which avoids capillary-induced structural degradation during the drying process), which is costly and time consuming. In addition, the mechanical stability of aerogels is poor, hindering their monolithic applications. While additives (such as carbon nanowires and polymer fibers) are used to blend with aerogels to improve mechanical stability, achieving mechanical strength without affecting the barrier properties remains quite challenging.

Inspired by the skin structure of human body, aerogel foam materials with pore size gradient have recently attracted people's interest due to their asymmetric structure, which not only can provide excellent insulating properties, but also provides a foundation for developing new functions. In addition, the aerogel foam material with the pore gradient structure has good prospect in the aspect of optimizing the mechanical property of a compact material or a porous material with uniform pore diameter. The sound absorption capacity of the gradient pore polylactic acid foam with the same porosity is improved by about 20 percent compared with that of the uniform foam. Silica foams with controlled hollow nanostructures/microstructures of tunable void fraction, pore size and mass density play a role in the development of superinsulation materials.

Lightweight aerogel materials are ideal for thermal insulation. However, its low mechanical integrity and high manufacturing cost have hindered its development for large-scale adoption in energy-saving building insulation. Furthermore, it may be important to obtain better sound and heat resistance characteristics for thermal management.

Since silica aerogel has a very large surface-to-volume ratio (about 2X 10)⁹m^-1) And specific surface area (about 900 m)²/g), the internal surface chemistry plays an important role in its thermal and chemical properties. The surface generated by the traditional supercritical drying is only covered by hydroxyl (-OH) (5-OH/nm)²) And has strong hydrogen binding ability (hydrophilicity). Therefore, it absorbs moisture from the humid air, thereby increasing its mass by 20%. In addition, the condensation of water within the nanopores exerts a sufficiently strong capillary force to break the silica framework and collapse the aerogel as a whole. Furthermore, at relatively high temperatures, the radiative component of the thermal conductivity of the silica aerogel is significant.

Silica aerogels are typically prepared by a sol-gel process in combination with supercritical extraction to maintain structural integrity and high porosity. Conventional aerogel preparation by supercritical extraction suffers from a number of limitations, including high energy consumption, large environmental footprint, long processing time, and high material cost. However, the complex processing and high pressures involved in supercritical drying limit the scalability of its mass production for building insulation. The most common aerogel synthesis methods include the use of low surface tension supercritical fluids (e.g., CO)₂Or CH₄) The liquid is extracted from the gel by critical point drying. However, supercritical extraction requires expensive high pressure equipment and is a dangerous and time consuming process. Alternative methods include organic solvent sublimation, which is difficult to scale up because of the energy intensive requirements of high vacuum required for solvent sublimation and relatively low temperatures required for freeze drying. The conventional atmospheric drying process, as an alternative with less energy consumption, replaces the original solvent used for gel formation with low surface tension organic solvents (e.g., hexane, heptane, octane, etc.). In addition, it often results in the production of hydrochloric acid, which further requires the removal of organic solvents. Thus, the current APD process remains a time consuming and expensive process due to the large amount of organic solvents used. All of these limit the use of large-scale aerogel production for building insulation. According to the Allied market research report 2014, the rapid growth of the aerogel market indicates that people are dealing with silica aerogel insulation ($ 18.5/ft)²-inches) interest: aerogel insulation was sold in 2004 at about $ 2500 million, but by 2013 has increased to $ 5 million (U.S. $), (a)Expected to reach $ 19.27 billion in 2021). However, a major disadvantage of using silica aerogel on a large scale as a standard insulation in construction is its high production cost. Therefore, aerogel production is currently used primarily for industrial applications, such as pipe insulation.

New methods of insulating materials (e.g., gradient structured insulating materials) with desirable mechanical integrity and low cost are desirable, particularly for scalable manufacturing of insulating materials (e.g., gradient structured insulating materials).

Disclosure of Invention

In various examples, scalable ceramic aerogels (e.g., pore gradient ceramic aerogels, which may be referred to as ceramic foams), monoliths (e.g., PGAeros), are designed and synthesized. In situ bubble formation further facilitates low cost manufacture of PGAeros to support pore gradients. PGAeros may exhibit robust mechanical and thermal stability over a wide temperature range (e.g., 0.040W m, respectively)^-1K^-1And a compressive strength of 100.56 MPa). For example, the monolithic ceramic nature of PGAeros may exhibit robust sound insulation and fire resistance. The ceramic aerogel materials can be scaled to produce exemplary materials useful for thermal insulation applications, e.g., having desirable thermal management, mechanical strength, low mass density, and sound insulation and flame retardant properties.

In one aspect, the present disclosure provides a method of making a ceramic foam. Ceramic foams may be referred to as ceramic aerogels or ceramic aerogel-like foams (e.g., silica aerogel-like foams). The ceramic foam may be a silica aerogel. The silica aerogel may be a silica aerogel film. The method is based on in situ pore-forming gas generation reactions. The reaction may be conducted in a sealed environment (e.g., the reaction may be conducted at a pressure greater than ambient pressure). Ceramic foams may be formed under hydrothermal conditions. In one example, the method does not include the use of any supercritical gas species. Non-limiting examples of the methods are provided herein.

In various examples, a method for forming a ceramic foam: such that the following are brought into contact (e.g., the contact may be made in a sealed environment such as a sealed container): one or more ceramic precursors (e.g., one or more silicon oxide precursors); one or more pore-forming gas forming additives (one or more inert gas generants); one or more catalysts; and optionally, one or more additives, wherein the contacting results in the formation of an inert gas (e.g., carbon dioxide) and the formation of a ceramic foam (e.g., silica aerogel). Ceramic foams (e.g., silica aerogels) can be formed under hydrothermal conditions. The reactants (ceramic precursor, pore-forming gas forming additive, catalyst, and optional additives) may be added/contacted in any order. The reactants may be contacted in a single vessel. The ceramic foam (e.g., silica aerogel) so formed may be subjected to Atmospheric Pressure Drying (APD). In various examples, the method further includes post-ceramic foam formation modification of at least a portion of a surface of the ceramic foam (e.g., silica aerogel). Higher surface modifications (e.g., trimethylchlorosilane treatment and/or carbon coating) can be used to build capillary action and superhydrophobicity. The process can be a continuous (e.g., roll-to-roll) process.

In one aspect, the present disclosure provides a ceramic foam. The ceramic foam may be a ceramic foam film. Ceramic foams may be referred to as ceramic aerogels. The ceramic foam may be a silica aerogel. The silica aerogel may be a silica aerogel film. Non-limiting examples of ceramic foams are provided herein. Ceramic foams (e.g., ceramic foam composites) include ceramic foams. The ceramic foam comprises a matrix of ceramic material. Ceramic foams may be prepared by the methods of the present disclosure. Ceramic foams (e.g., silica aerogels) can have various forms. For example, a ceramic foam (e.g., a silica aerogel) is a monolithic piece. In another example, the ceramic foam (e.g., silica aerogel) is a thin film. The ceramic foam (e.g., silica aerogel) can be a free-standing film or disposed on a substrate. Ceramic foam (e.g., silica aerogel) may penetrate into the substrate. The ceramic foam may be porous and exhibit a graded pore structure. The ceramic matrix of the ceramic foam may be of the mesoporous type. The ceramic foam may be a composite (e.g., a composite ceramic foam, such as a composite silica aerogel). The composite material may include a polymeric material (which may be referred to as a hybrid composite material or a hybrid ceramic foam) in some or all of the pores of the ceramic foam. The ceramic foam may have desirable sound transmission/sound insulation properties. In one example, ceramic foam is used as an insulating material (e.g., building material and/or sound insulation). In various examples, ceramic foams are used as templates or support substrates in catalyst, membrane, separation, etc. applications for coating other functional materials as composites.