Ceramic-polymer composite material obtained by cold sintering process
阅读说明：本技术 通过冷烧结方法获得的陶瓷-聚合物复合材料 (Ceramic-polymer composite material obtained by cold sintering process ) 是由 安妮·博尔瓦里 特奥多鲁斯·霍克斯 兰詹·达舍 托马斯·L·埃文斯 尼尔·普费芬伯格 乔纳 于 2017-08-25 设计创作，主要内容包括：本文描述了冷烧结的陶瓷聚合物复合材料和由无机化合物起始材料和聚合物制备它们的方法。冷烧结工艺和多种聚合物允许将各种聚合物材料掺入陶瓷中。(Cold-sintered ceramic polymer composites and methods for making them from inorganic compound starting materials and polymers are described herein. The cold sintering process and the multiple polymers allow for the incorporation of a variety of polymeric materials into the ceramic.)
1. A cold-sintered ceramic-polymer composite prepared by a process comprising:
a. mixing at least one inorganic compound in the form of particles having a number average particle size of less than about 30 [ mu ] m with at least one polymer (P)1) And a solvent in which the inorganic compound is at least partially soluble to obtain a mixture; and
b. subjecting the mixture to a pressure of not more than about 5000MPa and a temperature (T) not more than 200 ℃ above the boiling point of the solvent (measured at 1 bar)1) To obtain a cold-sintered ceramic polymer composite,
wherein if the polymer is crystalline or semi-crystalline, the polymer has a melting point (T)m) And, if the polymer is amorphous, the polymer has a glass transition temperature (T)g) Said melting point (T)m) Or the glass transition temperature (T)g) Below T1。
2. The cold-sintered ceramic-polymer composite material of claim 1, wherein the polymer is not polycarbonate, polyetheretherketone, polyetherimide, polyethersulfone, polyethylene, polypropylene, polystyrene, polytetrafluoroethylene, polyurethane, polyvinyl chloride, polyvinylidene fluoride, and sulfonated tetrafluoroethylene (Nafion).
3. A cold-sintered ceramic-polymer composite prepared by a process comprising:
a. mixing at least one inorganic compound in the form of particles having a number average particle size of less than about 30 [ mu ] m with at least one polymer (P)1) And a solvent in which the inorganic compound is at least partially soluble to obtain a mixture; and
b. subjecting the mixture to a pressure of not more than about 5000MPa and a temperature (T) not more than 200 ℃ above the boiling point of the solvent (measured at 1 bar)1) To obtain a cold-sintered ceramic polymer composite,
wherein if the polymer is crystalline or semi-crystalline, the polymer has a melting point (T)m) If the polymer is amorphous, the polymer is thenThe polymer has a glass transition temperature (T)g) Said melting point (T)m) Or the glass transition temperature (T)g) Below T1(ii) a And is
Wherein the polymer is a branched polymer.
4. The cold-sintered ceramic-polymer composite of any of claims 1 to 3, wherein T1No more than 100 ℃ above the boiling point of the solvent.
5. The cold-sintered ceramic-polymer composite according to any of claims 1 to 4, wherein the mixture further comprises at least one polymer (P)2) If the polymer is crystalline or semi-crystalline, the polymer has TmIf the polymer is amorphous, the polymer has TgSaid T ismOr said TgGreater than T1。
6. The cold-sintered ceramic-polymer composite of any of claims 1-5, wherein the method further comprises:
c. subjecting the cold-sintered ceramic polymer composite to a temperature greater than TmOr TgTemperature T of2。
7. Cold sintered ceramic polymer composite according to any of the claims 1-6, wherein said at least one polymer (P)1) Selected from the group consisting of: polyacetylene, polypyrrole, polyaniline, poly (p-phenylene vinylene), poly (3-alkylthiophene), polyacrylonitrile, poly (vinylidene fluoride), polyester, polyacrylamide, polytetrafluoroethylene, polychlorotrifluoroethylene, perfluoroalkoxyalkane, polyaryletherketone, polyarylene sulfone, polyarylethersulfone, polyarylene sulfide, polyimide, polyamideimide, polyesterimide, polyhydantoin, polycycloolefin, liquid crystal polymer, polyarylene sulfide, polyoxadiazole benzimidazole, polyimidazopyrrolone, polypyrone,Polyorganosiloxanes, polyamides, acrylics, copolymers thereof, and blends thereof.
8. The cold-sintered ceramic polymer composite of any one of claims 1-6, wherein the weight percentage of the inorganic compound in the mixture is about 50 to about 99% (w/w) based on the total weight of the mixture.
9. The cold-sintered ceramic-polymer composite of any of claims 1 to 8, wherein the weight percentage of the at least one polymer in the mixture is about 1 to about 50% (w/w) based on the total weight of the mixture.
10. The cold-sintered ceramic polymer composite of any of claims 1-9, wherein the solvent comprises water, an alcohol, an ester, a ketone, a dipolar aprotic solvent, or a combination thereof.
11. The cold-sintered ceramic-polymer composite of any of claims 1 to 10, wherein the solvent comprises at least 50% water by weight, based on the total weight of the solvent.
12. The cold-sintered ceramic-polymer composite of any of claims 1-11, wherein the solvent further comprises an inorganic acid, an organic acid, an inorganic base, a metal salt, or an organic base.
13. The cold-sintered ceramic-polymer composite of any of claims 1 to 12, wherein the method further comprises subjecting the cold-sintered ceramic-polymer composite to a post-curing or finishing step.
14. The cold-sintered ceramic-polymer composite material of claim 13, wherein the post-curing or finishing step is annealing or machining the cold-sintered ceramic-polymer composite material.
15. The cold-sintered ceramic-polymer composite according to any one of claims 1 to 14, wherein the method further comprises one or more steps selected from injection molding, compression molding, autoclaving, and calendering.
16. The cold-sintered ceramic-polymer composite of any of claims 1 to 15, wherein step (b) is conducted at a temperature (T) between about 50 ℃ and about 300 ℃1) The process is carried out as follows.
17. The cold-sintered ceramic-polymer composite of claim 16, wherein the temperature (T ™)1) Between about 70 ℃ and about 250 ℃.
18. The cold-sintered ceramic-polymer composite of claim 17, wherein the temperature (T ™)1) Between about 100 ℃ and about 200 ℃.
19. The cold-sintered ceramic polymer composite of any one of claims 1-18, wherein the mixture further comprises at least one of a carbon-based material and an elemental metal.
20. The cold-sintered ceramic-polymer composite of claim 19, wherein the carbon-based material is at least one selected from the group consisting of: graphite, nanotubes, graphene, carbon black, fullerenes, amorphous carbon, pitch, and tar.
21. The cold-sintered ceramic-polymer composite of any one of claims 1 to 20, wherein the cold-sintered ceramic-polymer composite has a relative density of at least 90%.
22. The cold-sintered ceramic-polymer composite of any one of claims 1 to 21, wherein the cold-sintered ceramic-polymer composite has a relative density of at least 95%.
23. A method for preparing a cold-sintered ceramic-polymer composite, comprising:
a. mixing at least one inorganic compound in the form of particles having a number average particle size of less than about 30 [ mu ] m with at least one polymer (P)1) And a solvent in which the inorganic compound is at least partially soluble to obtain a mixture; and
b. subjecting the mixture to a pressure of not more than about 5000MPa and a temperature (T) not more than 200 ℃ above the boiling point of the solvent (measured at 1 bar)1) To obtain a cold-sintered ceramic polymer composite,
wherein if the polymer is crystalline or semi-crystalline, the polymer has a melting point (T)m) And, if the polymer is amorphous, the polymer has a glass transition temperature (T)g) Said melting point (T)m) Or the glass transition temperature (T)g) Below T1。
24. The method of claim 23, wherein the polymer is not polycarbonate, polyetheretherketone, polyetherimide, polyethersulfone, polyethylene, polypropylene, polystyrene, polytetrafluoroethylene, polyurethane, polyvinyl chloride, polyvinylidene fluoride, and sulfonated tetrafluoroethylene (Nafion).
25. A method for preparing a cold-sintered ceramic-polymer composite, comprising:
a. mixing at least one inorganic compound in the form of particles having a number average particle size of less than about 30 [ mu ] m with at least one polymer (P)1) And a solvent in which the inorganic compound is at least partially soluble to obtain a mixture; and
b. subjecting the mixture to a pressure of not more than about 5000MPa and a temperature (T) not more than 200 ℃ above the boiling point of the solvent (measured at 1 bar)1) To obtain cold sinteredA ceramic-polymer composite material comprising a ceramic-polymer matrix,
wherein if the polymer is crystalline or semi-crystalline, the polymer has a melting point (T)m) And, if the polymer is amorphous, the polymer has a glass transition temperature (T)g) Said melting point (T)m) Or the glass transition temperature (T)g) Below T1(ii) a And is
Wherein the polymer is a branched polymer.
26. The method of any one of claims 23-25, wherein T is1No more than 100 ℃ above the boiling point of the solvent.
27. The method according to any one of claims 23-26, wherein the mixture further comprises at least one polymer (P)2) If the polymer is crystalline or semi-crystalline, the polymer has TmIf the polymer is amorphous, the polymer has TgSaid T ismOr said TgGreater than T1。
28. The method according to any one of claims 23-27, wherein the method further comprises:
(c) subjecting the cold-sintered ceramic polymer composite to a temperature greater than TmOr TgTemperature T of2。
29. The method according to any one of claims 23-28, wherein the at least one polymer (P)1) Selected from the group consisting of: polyacetylene, polypyrrole, polyaniline, poly (p-phenylene vinylene), poly (3-alkylthiophene), polyacrylonitrile, poly (vinylidene fluoride), polyester, polyacrylamide, polytetrafluoroethylene, polychlorotrifluoroethylene, perfluoroalkoxyalkane, polyaryletherketone, polyarylene sulfone, polyarylethersulfone, polyarylene sulfide, polyimide, polyamideimide, polyesterimide, polyhydantoin, polycycloolefin, liquid crystalPolymers, polyarylene sulfides, polyoxadiazole benzimidazoles, polyimidazopyrrolones, polypyrones, polyorganosiloxanes, polyamides, acrylics, copolymers thereof, and blends thereof.
30. The method of any of claims 23-29, wherein the weight percentage of the inorganic compound in the mixture is about 50 to about 99% (w/w) based on the total weight of the mixture.
31. The method of any of claims 23-30, wherein the weight percentage of the at least one polymer in the mixture is about 1 to about 50% (w/w) based on the total weight of the mixture.
32. The method of any one of claims 23-31, wherein the solvent comprises water, an alcohol, an ester, a ketone, a dipolar aprotic solvent, or a combination thereof.
33. The method of any of claims 23-32, wherein the solvent comprises at least 50% water by weight, based on the total weight of the solvent.
34. The method of any one of claims 23-33, wherein the solvent further comprises an inorganic acid, an organic acid, an inorganic base, or an organic base.
35. The method of any of claims 23-34, wherein the method further comprises subjecting the cold-sintered ceramic-polymer composite to a post-curing or finishing step.
36. The method of claim 35, wherein the post-curing or finishing step is annealing or machining the cold-sintered ceramic-polymer composite.
37. The method of any one of claims 23-36, wherein the method further comprises one or more steps selected from injection molding, autoclaving, and calendering.
38. The method of any one of claims 23-37, wherein step (b) is conducted at a temperature (T) between about 50 ℃ and about 300 ℃1) The process is carried out as follows.
39. Method according to claim 38, wherein said temperature (T)1) Between about 70 ℃ and about 250 ℃.
40. Method according to claim 39, wherein said temperature (T)1) Between about 100 ℃ and about 200 ℃.
41. The method of any of claims 23-40, wherein the mixture further comprises at least one of a carbon-based material and an elemental metal.
42. The method of claim 41, wherein the carbon-based material is at least one selected from the group consisting of: graphite, nanotubes, graphene, carbon black, fullerenes, amorphous carbon, pitch, and tar.
43. The method of any of claims 23-42, wherein the cold-sintered ceramic-polymer composite has a relative density of at least 90%.
44. The method of any of claims 23-43, wherein the cold-sintered ceramic-polymer composite has a relative density of at least 95%.
Background
Many ceramics and composites are sintered to reduce porosity and enhance material properties such as strength, electrical conductivity, translucency and thermal conductivity. The sintering process involves the application of high temperatures, typically above 1,000 ℃, to densify and improve the properties of the material. However, the use of high sintering temperatures precludes the manufacture of certain types of materials and increases the cost of manufacturing the materials.
Conventional ceramic component manufacture requires hot pressing of the ceramic material at elevated temperatures, typically 0.6 to 0.7 times the melting temperature. Since many non-ceramic materials have a lower melting temperature than the ceramic, the high temperature requirements of conventional sintering processes do not allow for the incorporation of the non-ceramic material into the ceramic matrix during the sintering process. In addition, non-ceramic materials may degrade when exposed to high temperatures or other conditions currently used in conventional sintering processes.
It is difficult to manufacture ceramic components of complex or near finished shapes using conventional sintering processes. Furthermore, it is difficult to manufacture ceramic components with high dimensional tolerances using conventional sintering processes. The high temperature of the conventional sintering process causes a volume change of the ceramic material, thereby making it difficult to control the size of the sintered part.
The use of high temperatures in conventional sintering processes may also produce by-products that require material handling systems for effective capture and safe disposal.
Using conventional techniques, it is difficult to manufacture ceramic components having a large number of grain boundaries. Furthermore, the high temperatures of conventional sintering processes result in the formation of large grains and thus reduce the number of grain boundaries.
For example, ultra-low temperature co-fired ceramics (U L TCC) can be fired between 450 ℃ and 750 ℃2MoO4/Ni0.5Zn0.5Fe2O4Magneto-dielectric composite material (L ow-Temperature Sintering L i)2MoO4/Ni0.5Zn0.5Fe2O4magnetic-Dielectric compositions for High-Frequency Application) ", J.Am.Ceram.Soc.2014:97 (8: 1-5. in addition, L i2MoO4Can be made by wetting the water-soluble L i2MoO4Powder, compressing it and working up the resulting sample at 120 ℃ see Kahari et al, J.Am.Ceram.Soc.2015:98(3):687-689, even though L i2MoO4The particle size of the powder is less than 180 microns, but Kahari teaches that smaller particle sizes complicate uniform wetting of the powder, leading to clay-like clustering, density non-uniformity, warping and cracking, and finally concludes that large particle sizes are advantageous.
Disclosure of Invention
The present invention addresses these and other challenges by providing a cold-sintered ceramic-polymer composite and a method of making the same. The method enables the production of a variety of ceramic polymer composites through a sintering step that occurs at low temperatures and moderate pressures.
Accordingly, in one embodiment, the present invention provides a cold-sintered ceramic-polymer composite prepared by a method comprising the steps of:
a. mixing at least one inorganic compound in the form of particles having a number average particle size of less than about 30 [ mu ] m with at least one polymer (P)1) And a solvent in which the inorganic compound is at least partially soluble to obtain a mixture; and
b. subjecting the mixture to a pressure of not more than about 5000MPa and a temperature (T) not more than 200 ℃ above the boiling point of the solvent (measured at 1 bar)1) To obtain a cold-sintered ceramic polymer composite.
If the polymer is crystalline or semi-crystalline, the polymer has a melting point (T)m) If the polymer is amorphous, the polymer has a glass transition temperature (T)g) Melting Point (T)m) Or glass transition temperature (T)g) Below T1. In some embodiments, despite these features, the polymer is not polycarbonate, polyetheretherketone, polyetherimide, polyethersulfone, polyethylene, polypropylene, polystyrene, polytetrafluoroethylene, polyurethane, polyvinyl chloride, polyvinylidene fluoride, and sulfonated tetrafluoroethylene (Nafion).
In another embodiment, the present invention provides a cold-sintered ceramic polymer composite prepared by a method comprising the steps of:
a. mixing at least one inorganic compound in the form of particles having a number average particle size of less than about 30 [ mu ] m with at least one polymer (P)1) And a solvent in which the inorganic compound is at least partially soluble to obtain a mixture; and
b. subjecting the mixture to a pressure of not more than about 5000MPa and not more than the boiling point of the solvent (measured at 1 bar)A temperature (T) of over 200 ℃1) To obtain a cold-sintered ceramic polymer composite.
In this embodiment, if the polymer is crystalline or semi-crystalline, the polymer has a melting point (T)m) If the polymer is amorphous, the polymer has a glass transition temperature (T)g) Melting Point (T)m) Or glass transition temperature (T)g) Below T1. Furthermore, the polymer is a branched polymer.
Another embodiment is a method for preparing a cold-sintered ceramic-polymer composite, comprising:
a. mixing at least one inorganic compound in the form of particles having a number average particle size of less than about 30 [ mu ] m with at least one polymer (P)1) And a solvent in which the inorganic compound is at least partially soluble to obtain a mixture; and
b. subjecting the mixture to a pressure of not more than about 5000MPa and a temperature (T) not more than 200 ℃ above the boiling point of the solvent (measured at 1 bar)1) To obtain a cold-sintered ceramic polymer composite.
In the process of the invention, the polymer has a melting point (T) if it is crystalline or semi-crystallinem) If the polymer is amorphous, the polymer has a glass transition temperature (T)g) Melting Point (T)m) Or glass transition temperature (T)g) Below T1. In some embodiments, the polymer is not polycarbonate, polyetheretherketone, polyetherimide, polyethersulfone, polyethylene, polypropylene, polystyrene, polytetrafluoroethylene, polyurethane, polyvinyl chloride, polyvinylidene fluoride, and sulfonated tetrafluoroethylene (Nafion).
Alternatively, according to another embodiment, the present invention provides a method for preparing a cold-sintered ceramic-polymer composite, comprising:
a. mixing at least one inorganic compound in the form of particles having a number average particle size of less than about 30 [ mu ] m with at least one polymer (P)1) And a solvent in which the inorganic compound is at least partially soluble to obtain a mixture; and
b. make the mixtureThe compound is subjected to a pressure of not more than about 5000MPa and a temperature (T) not more than 200 ℃ above the boiling point of the solvent (measured at 1 bar)1) To obtain a cold-sintered ceramic polymer composite.
In this embodiment, if the polymer is crystalline or semi-crystalline, the polymer has a melting point (T)m) If the polymer is amorphous, the polymer has a glass transition temperature (T)g) Melting Point (T)m) Or glass transition temperature (T)g) Below T1. Furthermore, the polymer is a branched polymer.
Cold-sintered ceramic polymer composites, prepared by any of the methods described herein, are also contemplated in various embodiments. The cold sintering step of the process may result in densification of the inorganic compound. Thus, according to some embodiments, the cold-sintered ceramic polymer composite or cold-sintered ceramic exhibits a relative density of at least 70% as determined by mass/geometry ratio, archimedes' method, or equivalent method. The relative density may be at least 75%, 80%, 85%, 90% or 95%.
Detailed Description
Briefly, the density of the samples was determined using the Archimedes method using a KERN ABS-N/ABJ-NM balance equipped with an ACS-A03 densitometer. First, a dried sample (e.g., pellet) (W) is weighedDry matter) And boiled in 2-propanol for a period of 1 hour. The sample was then suspended in 2-propanol at a known temperature to determine the apparent mass (W) in the liquidSuspension) The excess liquid was removed and wiped from the sample surface using tissue wetted with 2-propanol. The saturated sample (W) was then immediately weighed in airSaturation of). Then, the density was determined by the following formula:
density of WDry matter/(WSaturation of-WSuspension) Density of solvent
Wherein the density of 2-propanol is considered to be 0.786g/cm at 20 deg.C30.785g/cm at 21 DEG C3And 0.784g/cm at 22 DEG C3。
Geometric method for determining density, also known as "geometryVolume) method ", involves measuring the diameter (D) and thickness (t) of a cylindrical sample using, for example, a digital caliper. Can be according to the formula V ═ pi (D/2)2x t the volume of the cylinder is calculated. The mass of the cylindrical sample was measured with an analytical balance. The relative density is determined by dividing the mass by the volume.
For simple geometries, such as cubes, cuboids and cylinders, the volume method is comparable to the archimedes method, where it is relatively easy to measure the volume. For samples with highly irregular geometries, it can be difficult to accurately measure the volume, in which case the archimedes method may be more suitable for measuring density.
Values expressed in a range format should be interpreted in a flexible manner throughout the document to include not only the numerical values explicitly recited as the limits of the range, but also to include all the individual numerical values or sub-ranges encompassed within that range as if each numerical value and sub-range is explicitly recited. For example, a range of "about 0.1% to about 5%" or "about 0.1% to 5%" should be interpreted as including not only about 0.1% to about 5%, but also the various values (e.g., 1%, 2%, 3%, and 4%) and sub-ranges (e.g., 0.1% to 0.5%, 1.1% to 2.2%, 3.3% to 4.4%) within the indicated range. Unless otherwise indicated, a statement of "about X to Y" has the same meaning as "about X to about Y". Likewise, unless otherwise specified, a statement of "about X, Y or about Z" has the same meaning as "about X, about Y, or about Z".
As used herein, the terms "a", "an" or "the" are intended to include one or more than one, unless the context clearly dictates otherwise. The term "or" is used to mean a non-exclusive "or" unless otherwise stated. The statement "at least one of a and B" has the same meaning as "A, B or a and B". Also, it is to be understood that the phraseology or terminology employed herein, and not otherwise defined, is for the purpose of description only and not of limitation. The use of any chapter title is intended to aid in reading the document and should not be construed as limiting; information related to the section header may appear inside or outside of that particular section.
In the methods described herein, acts may be performed in any order, except where time or sequence of operations is explicitly recited, without departing from the principles of the invention. Further, unless explicitly recited in a claim language as being performed separately, specified actions may be performed concurrently. For example, the claimed act of doing X and the claimed act of doing Y may be performed simultaneously in a single operation, and the resulting process would fall within the literal scope of the claimed process.
As used herein, the term "about" may allow for a degree of variability in the value or range, for example, within 10%, 5%, or 1% of the stated value or stated range limit, and includes the exact stated value or range. The term "substantially" as used herein means that the majority or majority is at least about 50%, 60%, 70%, 80%, 90%, 95%, 96%, 97%, 98%, 99%, 99.5%, 99.9%, 99.99%, or at least about 99.999% or more, or 100%.
The present invention provides a cold-sintered ceramic-polymer composite obtained by any of the methods described herein, any of which is referred to as a cold-sintering process (CSP). The sintering process described herein involves thermochemical treatment of mixtures of ceramic and non-ceramic components at low temperatures in acidic, basic or neutral chemical environments, as compared to those required for conventional ceramic sintering. The CSP includes the presence of one or more solvents that have a degree of reactivity with or are capable of at least partially dissolving one or more inorganic compounds that are preformed ceramic materials. The low sintering temperature of the CSP enables the incorporation of non-ceramic materials prior to the sintering process, which incorporation is not possible or difficult to achieve in conventional high temperature sintering processes. The incorporation of non-ceramic components in sintered ceramic matrices provides several characteristics not typical of ceramics, including electrical conductivity, thermal conductivity, flexibility, crack propagation resistance, different wear resistance properties, different dielectric constants, improved electrical breakdown strength, and/or improved mechanical toughness.
In the process of the invention, one or more inorganic compounds in the form of particles are mixed with at least one solvent andone polymer (P) less1) And (4) mixing. Without wishing to be bound by any particular theory of operation, the inventors believe that the inorganic compound reacts with or partially dissolves in the solvent to form a solid solution on the surface of the inorganic compound particles. In one exemplary embodiment, a mixture of inorganic compound, solvent, and polymer is placed in a mold and subjected to pressure and elevated temperature, typically not greater than about 5000MPa, temperature (T.sub.1) Not more than 200 ℃ above the boiling point of the solvent (measured at 1 bar). The presence of a solid solution and the applied pressure and temperature allow the inorganic compound to sinter.
It is likely that dissolution of the sharp edges of the solid particles reduces the interfacial area and that some capillary forces contribute to the rearrangement of the initial stages of sintering. Under the action of external and capillary pressure, the liquid phase redistributes itself and fills the pores between the particles. Due to the pressure-assisted flow of the liquid, the solid particles can rapidly rearrange, which together leads to densification. The subsequent stage, commonly referred to as "solution-precipitation", is produced by liquid evaporation, which places the liquid phase in a supersaturated state at low temperatures, triggering a large chemical driving force of the solid and liquid phases to reach an equilibrium state.
The contact area between the particles has a higher chemical potential under the externally applied pressure and capillary pressure, so at this stage the ionic species and/or atomic clusters diffuse through the liquid and precipitate on the particles at a location remote from the contact area. Mass transfer during this process minimizes the excess free energy of the surface region and removes porosity when the material forms a dense solid. Due to the fixed shape of the hot press mold, the particles will shrink and flatten out mainly in the direction of the external pressure.
In the final stage of sintering, as most of the water evaporates, the solid-solid contact area increases, resulting in the formation of a rigid skeletal network of solid particles, which reduces the densification rate. Meanwhile, a nano-thick amorphous phase may be generated in some grain boundary regions, thereby suppressing grain boundary diffusion activity. However, particle shape adjustment will slowly eliminate porosity, facilitating further densification at this stage. During the CSP, such as polymer (P)1) Remain in the ceramic matrix, thereby producing a cold-sintered ceramic polymer composite. Thus, well dispersed polymer (P) within the ceramic1) Improved interaction between the ceramic and the polymer results in enhanced fracture toughness, improved tribological properties, better scratch performance, better thermal conductivity, and better electrical properties compared to sintered ceramics without the polymer.
Inorganic compound
Various embodiments of the methods described herein use at least one inorganic compound in particulate form. Useful inorganic compounds include, but are not limited to, metal oxides, metal carbonates, metal sulfates, metal sulfides, metal selenides, metal tellurides, metal arsenides, metal alkoxides, metal carbides, metal nitrides, metal halides (e.g., fluorides, bromides, chlorides, and iodides), clays, ceramic glasses, metals, and combinations thereof. Specific examples of the inorganic compound include MoO3、WO3、V2O3、V2O5、ZnO、Bi2O3、CsBr、Li2CO3、CsSO4、Li2MoO4、Na2Mo2O7、K2Mo2O7、ZnMoO4、Gd2(MoO4)3、Li2WO4、Na2WO4、LiVO3、BiVO4、AgVO3、Na2ZrO3、LiFePO4And KH2PO4. In other embodiments, the precursor metal salt may be used in the form of a solution to assist or otherwise facilitate the cold sintering process. For example, water soluble zinc (II) salts such as zinc chloride and zinc acetate deposit water insoluble ZnO on existing inorganic surfaces. In this way, the precipitation of ZnO from the precursor solution thermodynamically favors the progress of the cold sintering process.
In some embodiments, the present methods use mixtures of inorganic compounds that react with each other upon sintering to provide sintered ceramic materials (solid state reaction sintering). The method comprisesOne advantage is the reliance on relatively inexpensive inorganic compound starting materials. Other advantages of the Solid State Reaction Sintering (SSRS) method include simplifying the manufacturing process of proton conducting ceramics by integrating phase formation, densification and grain growth into one sintering step. See S.Nikodemski et al, SolidState Ionics 253(2013) 201-210. An example of a reactive inorganic compound relates to Cu2S and in2S3To produce stoichiometric CuInS2See T.Miyauchi et al, Japanese Journal of applied Physics, Vol.27, part 2, No. 7, L1178 Another example is Y-direction during sintering2O3、ZrO2And BaCO3Adding NiO to produce BaY2NiO5. See J.Tong, J.Mater.chem.20(2010) 6333-6341.
The inorganic compound is present in particulate form, for example as a fine powder. Any conventional method for preparing an inorganic compound in particulate form is suitable. For example, the particles may be produced by various milling processes, such as ball milling, sand milling, vibratory milling, and jet milling.
The resulting particle size of the inorganic compound, i.e., the diameter, is about 100 μm or less based on the particle number average. In various embodiments, the average number particle size is less than about 90 μm, less than about 80 μm, less than about 70 μm, less than about 60 μm, less than about 50 μm, less than about 40 μm, less than about 30 μm, less than about 20 μm, or less than about 10 μm. Any suitable method may be used to measure particle size and distribution, such as laser light scattering. In exemplary embodiments, at least 80%, at least 85%, at least 90%, or at least 95% by number of the particles have a size less than the number average particle size.
According to some embodiments of the invention, the inorganic compound is mixed with a solvent to obtain a mixture. In other embodiments, the inorganic compound is mixed with a solvent and at least one monomer, reactive oligomer, or combination thereof to obtain a mixture. In these embodiments, the inorganic compound is present in an amount of about 50 to about 95 weight percent, based on the total weight of the mixture. Exemplary weight percentages of inorganic compounds in the mixture are at least 50%, at least 55%, at least 60%, at least 65%, at least 70%, at least 75%, at least 80%, at least 85%, and at least 90%.
Solvent(s)
The process of the invention uses at least one solvent in which the inorganic compound has at least partial solubility. Useful solvents include water, alcohols such as C1-6Alkyl alcohols, esters, ketones, dipolar aprotic solvents (e.g., dimethyl sulfoxide (DMSO), N-methyl-2-pyrrolidone (NMP), and Dimethylformamide (DMF)), and combinations thereof. In some embodiments, only a single solvent is used. In other embodiments, a mixture of two or more solvents is used.
Other embodiments provide an aqueous solvent system to which one or more additional components are added to adjust the pH. The components include inorganic and organic acids, and organic and inorganic bases.
Examples of the inorganic acid include sulfurous acid, sulfuric acid, dithionous acid, persulfuric acid, pyrosulfuric acid, pyrosulfurous acid, dithionous acid, tetrathiosulfuric acid, bisulfic acid, peroxodisulfuric acid, perchloric acid, hydrochloric acid, hypochlorous acid, chlorous acid, chloric acid, hypodinitric acid, nitrous acid, nitric acid, peroxynitric acid, carbonic acid-containing acid, carbonic acid, hypobicarbonic acid, percarbonic acid, oxalic acid, acetic acid, phosphoric acid, phosphorous acid, hypophosphorous acid, perphosphoric acid, hypophosphorous acid, pyrophosphoric acid, hydrogenophoric acid, hydrobromic acid, bromic acid, hypobromous acid, hypoiodic acid, iodic acid, periodic acid, hydroiodic acid, fluoric acid, hydrofluoric acid, chromic acid, dichromic acid, perchloric acid, selenic acid, hydrazoic acid, boric acid, molybdic acid, xenon acid, silicofluoric acid, telluric acid, selenic acid, tungstic acid, telluric acid, citric acid, formic acid, pyroantimonic acid, permanganic acid, manganic acid, antimonic acid, antimonous acid, silicic acid, titanic acid, arsenic acid, pertechnetic acid, hydrogen arsenic acid, dichromic acid, tetraboric acid, metastannic acid, hypooxalic acid, ferricyanic acid, cyanic acid, silicic acid, hydrocyanic acid, thiocyanic acid, uranic acid and diurenic acid
Examples of organic acids include malonic acid, citric acid, tartaric acid, glutamic acid, phthalic acid, azelaic acid, barbituric acid, benzilic acid, cinnamic acid, fumaric acid, glutaric acid, gluconic acid, caproic acid, lactic acid, malic acid, oleic acid, folic acid, propiolic acid, propionic acid, rosolic acid, stearic acid, tannic acid, trifluoroacetic acid, uric acid, ascorbic acid, gallic acid, acetylsalicylic acid, acetic acid, and sulfonic acids such as p-toluenesulfonic acid.
Examples of the inorganic base include aluminum hydroxide, ammonium hydroxide, arsenic hydroxide, barium hydroxide, beryllium hydroxide, bismuth (iii) hydroxide, boron hydroxide, cadmium hydroxide, calcium hydroxide, cerium (iii) hydroxide, cesium hydroxide, chromium (ii) hydroxide, chromium (iii) hydroxide, chromium (v) hydroxide, chromium (vi) hydroxide, cobalt (ii) hydroxide, cobalt (iii) hydroxide, copper (i) hydroxide, copper (ii) hydroxide, gallium (iii) hydroxide, gold (i) hydroxide, gold (iii) hydroxide, indium (i) hydroxide, indium (ii) hydroxide, indium (iii) hydroxide, iridium (iii) hydroxide, iron (ii) hydroxide, iron (iii) hydroxide, lanthanum hydroxide, lead (ii) hydroxide, lead (iv) hydroxide, lithium hydroxide, magnesium hydroxide, manganese (ii) hydroxide, manganese (vii) hydroxide, Mercury (i) hydroxide, mercury (ii) hydroxide, molybdenum (ii) hydroxide, neodymium (ii) hydroxide, nickel oxyhydroxide, nickel (ii) hydroxide, nickel (iii) hydroxide, niobium (ii) hydroxide, osmium (iv) hydroxide, palladium (ii) hydroxide, palladium (iv) hydroxide, platinum (ii) hydroxide, platinum (iv) hydroxide, plutonium (iv) hydroxide, potassium hydroxide, radium hydroxide, rubidium hydroxide, ruthenium (iii) hydroxide, scandium hydroxide, silicon hydroxide, silver hydroxide, sodium hydroxide, strontium hydroxide, tantalum (v) hydroxide, technetium (ii) hydroxide, tetramethylammonium hydroxide, thallium (i) hydroxide, thallium (iii) hydroxide, thorium hydroxide, tin (ii) hydroxide, tin (iv) hydroxide, titanium (ii) hydroxide, titanium (iii) hydroxide, titanium (iv) hydroxide, tungsten (ii) hydroxide, uranyl hydroxide, vanadium (ii) hydroxide, Vanadium (iii) hydroxide, vanadium (v) hydroxide, ytterbium (v) hydroxide, yttrium (v) hydroxide, zinc hydroxide, and zirconium hydroxide.
Organic bases are generally nitrogen-containing because they can accept protons in aqueous media. Exemplary organic bases include primary, secondary and tertiary (C)1-10) Alkylamines, such as methylamine, trimethylamine, etc. A further example is (C)6-10) Aryl amines and (C)1-10) -alkyl- (C)6-10) -aryl-amines. Other organic bases incorporate nitrogen into the cyclic structure, e.g. inMonocyclic and bicyclic heterocyclic and heteroaryl compounds. These include, for example, pyridine, imidazole, benzimidazole, histidine and phosphazenes.
In some of the methods described herein, an inorganic compound is mixed with a solvent to obtain a mixture. According to various embodiments, the solvent is present in an amount of about 40% by weight or less, based on the total weight of the mixture. Alternatively, the weight percent of solvent in the mixture is 35% or less, 30% or less, 25% or less, 20% or less, 15% or less, 10% or less, 5% or less, 3% or less, or 1% or less.
Polymer and method of making same
A variety of polymers are suitable for use in the cold-sintered ceramic polymer composites and methods described herein. Polymers suitable for use in the present invention are those that are temperature and pressure compatible under the reaction conditions of the cold sintering process described herein, such that the polymer is capable of melting, flowing, and/or softening to an extent that allows the polymer to fill inter-particle and intra-particle voids in the sintered ceramic structure within the cold sintered ceramic-polymer composite. Polymers that meet these basic criteria may be generally referred to as non-sinterable polymers.
In contrast, other polymers do not significantly melt, flow and/or soften under the cold sintering conditions described herein. Instead, these polymers can be compressed and densified under external pressure, and they retain or form a granular or fibrous microstructure during sintering. Thus, these polymers may be generally referred to as sinterable polymers.
In some embodiments, if the polymer is crystalline or semi-crystalline, the polymer has a melting point (T)m). Some polymers, even crystalline or semi-crystalline, have a glass transition temperature (T)g). However, in these cases, TmIs the selection of a polymer for a defined feature used in the present invention. Melting Point (T)m) Measured by methods and instruments well known in the polymer art.
Other polymers, e.g. amorphous, not having TmBut may be prepared by methods well known in the polymer artMeasured glass transition temperature T by method and apparatusgTo characterize.
In some embodiments, each polymer in the cold-sintered ceramic-polymer composite is selected such that it has a Tm(if the polymer is crystalline or semi-crystalline) or T thereofg(if the polymer is amorphous) less than the temperature (T)1) Which is 200 ℃ higher than the boiling point (as measured at 1 bar) of the solvent or solvent mixture used in the cold sintering process described herein. Thus, according to one exemplary embodiment, the solvent is water, which has a boiling point of 100 ℃ at one bar, and thus the polymer should have a T of not more than 300 ℃mOr Tg. In other embodiments, T1Between about 70 ℃ to about 250 ℃, or about 100 ℃ to about 200 ℃. Although water may be the solvent in these illustrative embodiments, because of T1Not more than 200 ℃ above the boiling point of water at one bar, various other solvents and solvent mixtures meet these basic requirements.
Despite the above polymer selection criteria, it is understood that for these various embodiments, the polymer is not polycarbonate, polyetheretherketone, polyetherimide, polyethersulfone, polyethylene, polypropylene, polystyrene, polytetrafluoroethylene, polyurethane, polyvinyl chloride, polyvinylidene fluoride, and sulfonated tetrafluoroethylene (Nafion).
However, in other embodiments, the suitable polymer is selected primarily based on the polymer being a branched polymer, and in some embodiments, it may be in accordance with T as described abovemOr TgAnd (4) selecting in addition. As understood in the polymer art, branched polymers are polymers that are not completely linear, i.e., the backbone of the polymer contains at least one branch, and in some embodiments the degree of branching is substantial. Without wishing to be bound by any particular theory, the inventors believe that, according to various embodiments, the branched polymers are purified at the pressures employed during cold sintering such that a given branched polymer is capable of undergoing higher flow than its linear counterpart, such that only the branched polymers are suitable for preparing cold sintered ceramic polymer composites as described herein.
Examples of polymer structures contemplated for use in the method of the present invention include linear and branched polymers, copolymers such as random and block copolymers, and crosslinked polymers. Also contemplated are polymer blends, and blends of crosslinked polymers with non-crosslinked polymers.
Other classes and specific polymers include Acrylonitrile Butadiene Styrene (ABS) polymers, acrylic polymers, celluloid polymers, cellulose acetate polymers, Cyclic Olefin Copolymers (COC), ethylene-vinyl acetate (EVA) polymers, ethylene-vinyl alcohol (EVOH) polymers, fluoroplastics, acrylic/PVC alloys, liquid crystal polymers (L CP), polyacetal polymers (POM or acetal), polyacrylate polymers, polymethyl methacrylate Polymers (PMMA), polyacrylonitrile polymers (PAN or acrylonitrile), polyamide polymers (PA, e.g. nylon), polyamide-imide Polymers (PAI), polyaryletherketone Polymers (PAEK), polybutadiene Polymers (PBD), polybutylene Polymers (PB), polybutylene terephthalate Polymers (PBT), polycaprolactone polymers (PC L), polychlorotrifluoroethylene Polymers (PCTFE), polytetrafluoroethylene Polymers (PTFE), polyethylene terephthalate Polymers (PET), polycycloethylene terephthalate Polymers (PC), polycyclohexylene terephthalate Polymers (PC), polyethylene terephthalate polymers (PP), polyethylene terephthalate Polymers (PC), polyethylene terephthalate copolymers (PP), polyethylene terephthalate Polymers (PC), polyethylene terephthalate polymers (PP), polyethylene terephthalate Polymers (PC), polyethylene terephthalate polymers (PP), polyethylene terephthalate polymers (PPS) and polyethylene terephthalate polymers (PPS) with very low densities (PPS), polyethylene terephthalate polymers (polypropylene (ppk), polyethylene terephthalate polymers (polypropylene), polyethylene terephthalate polymers (ppk), polyethylene terephthalate polymers (polypropylene), polyethylene terephthalate polymers (polypropylene), polyethylene terephthalate polymers (polypropylene), polyethylene terephthalate polymers (polypropylene), polypropylene (polypropylene), polyethylene terephthalate) with very low densities), polypropylene (polypropylene), polypropylene (polypropylene), polypropylene (polypropylene), polypropylene (polypropylene), polypropylene (polypropylene), polypropylene (polypropylene), polypropylene.
Additional polymers include polyacetylene, polypyrrole, polyaniline, poly (p-phenylenevinylene), poly (3-alkylthiophene), polyacrylonitrile, poly (vinylidene fluoride), polyesters (e.g., polyalkylene terephthalates), polyacrylamides, polytetrafluoroethylene, polychlorotrifluoroethylene, perfluoroalkoxyalkanes, polyaryletherketones, polyarylene sulfones, polyarylene sulfides, polyimides, polyamideimides, polyesterimides, polyhydantoins, polycycloolefins, liquid crystal polymers, polyarylene sulfides, polyoxadiazole, polyimidazopyrrolone, polypyrone, polyorganosiloxane (e.g., polydimethylsiloxane), polyamides (e.g., nylon), acrylics, sulfonated polymers, copolymers thereof, and blends thereof.
Other useful polymers are ionic polymers or oligomers ("ionomers"). One key feature of ionomers is the relatively modest concentration of acid or ionic groups that bind to the oligomer/polymer backbone and impart a substantial change in the physical, mechanical, optical, dielectric, and dynamic properties to the polymer and, therefore, the cold-sintered ceramic-polymer composite. For example, polymers with acid functionality can undergo interchain and physical crosslinking through hydrogen bonding between acid groups. Illustrative oligomers include sulfonated oligomers. Furthermore, fatty acids or tetraalkylammonium salts can be introduced by the method of the invention to facilitate additional ionic interactions.
Additional Components
Various embodiments of the method of the present invention contemplate introducing one or more additional materials into the mixture for cold sintering, or into a cold sintered ceramic polymer composite. Any combination of these materials can readily produce and/or tailor the composition and properties of the cold-sintered ceramic-polymer composite. Typically, any of the additives described herein are present in an amount of about 0.001 wt% to about 50 wt%, about 0.01 wt% to about 30 wt%, about 1 to about 5 wt%, or about 0.001 wt% or less, or about 0.01 wt%, 0.1 wt%, 1 wt%, 2 wt%, 3 wt%, 4 wt%, 5 wt%, 10 wt%, 15 wt%, 20 wt%, 25 wt%, 30 wt%, 35 wt%, 40 wt%, 45 wt%, or about 50 wt% or more, based on the total weight of the cold-sintered ceramic-polymer composite.
Supramolecular structures
For example, some embodiments provide for the addition of supramolecular structures that are generally characterized by a combination of substructures held together by weak interactions, e.g., non-covalent bonds may be used. At the temperatures used for cold sintering, the interaction may be weakened, releasing sub-structural molecules that may flow through or into the newly created pores of the particulate inorganic compound or cold sintered ceramic. Upon cooling, the substructure molecules can reassemble into supramolecular structures embedded in cold-sintered ceramics. Typical compounds suitable for this purpose are hydrogen bonding molecules, which may have, for example, single, double, triple or quadruple hydrogen bonds. Other structures take advantage of host-guest interactions and in this way create supramolecular (polymer) structures.
Examples of supramolecular structures include macrocyclic compounds such as cyclodextrins, calixarenes, cucurbiturils and crown ethers (host-guest interactions based on weak interactions); amide or carboxylic acid dimers, trimers or tetramers, such as 2-ureido-4 [1H ] -pyrimidinone (via hydrogen bonding), bipyridine or tripyridine (via complexation with a metal) and various aromatic molecules (via pi-pi interactions).
Sol-gel
Other embodiments provide for the introduction of sol-gel into a mixture of cold-sintered ceramics. The sol-gel process consists of a series of hydrolysis and condensation reactions of metal alkoxides, and in some cases also alkoxysilanes. Hydrolysis is initiated by adding water to the alkoxide or silane solution under acidic, neutral or basic conditions. Thus, by adding a small amount of water to the metal alkoxide, a polymer nanocomposite can be obtained. Examples of compounds that can be used to prepare the sol-gel include silicon alkoxides such as tetraalkyl orthosilicates (e.g., tetraethyl orthosilicate), silsesquioxanes, and phenyltriethoxysilane.
Filler material
According to some embodiments, the cold-sintered ceramic polymer composite may include one or more fillers. The filler may be present at about 0.001 wt% to about 50 wt% of the composite, or about 0.01 wt% to about 30 wt%, or about 0.001 wt% or less, or about 0.01 wt%, 0.1, 1, 2, 3, 4, 5, 10, 15, 20, 25, 30, 35, 40, 45 wt%, or about 50 wt% or more. The filler may be uniformly distributed in the composite material. The filler may be fibrous or particulate. The filler can be aluminum silicate (mullite), synthetic calcium silicate, zirconium silicate, fused silica, crystalline silica graphite, natural silica sand, etc.; boron powders such as boron nitride powder, boron silicate powder, and the like; oxides such as TiO2Alumina, magnesia, and the like; calcium sulfate (in its anhydride, anhydrate or trihydrate form); calcium carbonates such as chalk, limestone, marble, synthetic precipitated calcium carbonate, and the like; talc, including fibrous, modular, acicular, lamellar talc, and the like; wollastonite; surface treated wollastonite; glass spheres such as hollow and solid glass spheres, silicate spheres, cenospheres, aluminosilicate (glass beads), and the like; kaolin, including hard kaolin, soft kaolin, calcined kaolin, kaolin comprising various coatings known in the art to facilitate compatibility with the polymeric matrix resin, and the like; single crystal fibers or "whiskers" such as silicon carbide, alumina, boron carbide, iron, nickel, copper, and the like; fibers (including continuous and chopped fibers) such as asbestos, carbon fibers, glass fibers; sulfides such as molybdenum sulfide, zinc sulfide, etc.; barium compounds such as titaniumBarium sulfate, barium ferrite, barium sulfate, barite, etc.; metals and metal oxides (e.g., particulate or fibrous aluminum, bronze, zinc, copper, and nickel, etc.); flaked fillers such as glass flakes, flaked silicon carbide, aluminum diboride, aluminum flakes, steel flakes, and the like; fibrous fillers, such as short inorganic fibers, for example those derived from blends comprising at least one of aluminum silicates, aluminum oxides, magnesium oxides, and calcium sulfate hemihydrate or the like; natural fillers and reinforcements, such as wood flour obtained by pulverizing wood, fibrous products such as kenaf, cellulose, cotton, sisal, jute, flax, starch, corn flour, lignin, ramie, rattan, agave, bamboo, hemp, ground nut shells, corn, coconut (coconut shell), rice grain shells and the like; organic fillers such as polytetrafluoroethylene, reinforcing organic fibrous fillers formed from organic polymers capable of forming fibers such as poly (ether ketone), polyimide, polybenzoxazole, poly (phenylene sulfide), polyesters, polyethylene, aromatic polyamides, aromatic polyimides, polyetherimides, polytetrafluoroethylene, acrylic resins, poly (vinyl alcohol), and the like; and fillers such as mica, clay, feldspar, flue dust, fillite, quartz, quartzite, perlite, diatomaceous earth, carbon black, or the like, or a combination comprising at least one of the foregoing fillers. The filler may be talc, kenaf or a combination thereof. The filler may be coated with a layer of metallic material to promote electrical conductivity, or the surface treated with silane, siloxane, or a combination of silane and siloxane to improve adhesion and dispersion within the composite. The filler may be selected from carbon fibers, mineral fillers, and combinations thereof. The filler may be selected from mica, talc, clay, wollastonite, zinc sulfide, zinc oxide, carbon fiber, glass fiber, ceramic coated graphite, titanium dioxide, or combinations thereof.
Metal and carbon
In various embodiments, the cold-sintered ceramic polymer composite comprises one or more elemental metals. The metal is present in powdered or particulate form, such as nanoparticles, with a number average particle size ranging from about 10nm to about 500 nm. Exemplary metals include, but are not limited to, lithium, beryllium, sodium, magnesium, aluminum, potassium, calcium, scandium, titanium, vanadium, chromium, manganese, iron, cobalt, iron, magnesium, and magnesium,Nickel, copper, zinc, gallium, rubidium, strontium, yttrium, zirconium, niobium, molybdenum, technetium, ruthenium, rhodium, palladium, silver, cadmium, indium, tin, cesium, barium, lanthanum, cerium, praseodymium, neodymium, promethium, samarium, europium, gadolinium, terbium, dysprosium, holmium, erbium, thulium, ytterbium, lutetium, hafnium, tantalum, tungsten, rhenium, osmium, iridium, platinum, gold, mercury, thallium, lead, bismuth, polonium, francium, radium, actinium, thorium, protactinium, uranium, neptunium, plutonium, americium, curium, berkelium, californium, fermi, oburn, lutetium, , niobium, cerium, yttrium,, the seeds of Felis Argus, the root of Chinese Caterpillar fungus, the fruit of Chinese Caterpillar fungus, , the fruit of titanium, the fruit of ladium, and the combination thereof.
In other embodiments, optionally in combination with any other embodiment, the cold-sintered ceramic polymer composite comprises one or more forms of carbon. Carbon may be introduced into the mixture of polymer and one or more inorganic compounds prior to the cold sintering step of the methods described herein. Various forms of carbon are suitable for use in the present invention, including graphite, nanotubes, graphene, carbon black, fullerenes, amorphous carbon, pitch, and tar.
Other process steps
The final physical form and properties of the cold-sintered ceramic polymer composite can be adjusted by performing additional steps that occur before and/or after the cold-sintering step. For example, the present methods in various embodiments include one or more steps including injection molding, autoclaving, calendering, dry compression molding, tape casting, and extrusion. These steps may be performed on the mixture to impart a physical form or geometry that remains after the cold sintering step. In this manner, for example, the calendering step can ultimately result in a sheet form of the cold-sintered ceramic-polymer composite. Alternatively, mechanical parts with complex geometries, features and shapes can be produced by first injection molding the mixture, followed by cold sintering it.
Alternatively, or in addition, various post-curing or finishing steps (finishing steps) are introduced. These include, for example, annealing and machining. In some embodiments, an annealing step is introduced, wherein greater physical strength or resistance to cracking is required in the cold-sintered ceramic polymer composite. Furthermore, for some polymers or combinations of polymers, the cold sintering step, while sufficient to sinter the ceramic, does not provide sufficient heat to ensure complete flow of the polymer or polymers into the ceramic voids. Thus, the annealing step may provide heat for a time sufficient to achieve full flow, thereby ensuring, for example, improved breakdown strength, toughness, and tribological properties as compared to a cold-sintered ceramic-polymer composite that has not been subjected to the annealing step.
Alternatively, the cold-sintered ceramic polymer composite may be subjected to an optionally pre-programmed temperature and/or pressure ramp, hold, or cycle, wherein the temperature or pressure, or both, is increased or decreased, optionally multiple times.
The cold-sintered ceramic polymer composite may also be processed using conventional techniques known in the art. Processing steps may be performed to produce a finished part. For example, a pre-sintering step of injection molding may produce the overall shape of the part, while a post-sintering step of machining may add detail and precise features.
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