A method for preparing hierarchical porous ceramics based on heat-sensitive emulsion combined with direct-write printing forming

Abstract

The application discloses a method for preparing a hierarchical porous ceramic based on a heat-sensitive emulsion combined with direct writing printing forming, and belongs to the technical field of porous ceramic materials. The method comprises the following steps: after ceramic powder and / or ceramic powder oxide sol nanoparticles are mixed with epoxy resin and a diluent through ball milling to obtain a uniform ceramic suspension, a surfactant, deionized water and a curing agent are added, and the stable heat-sensitive emulsion is prepared through sufficient mechanical stirring. The heat-sensitive emulsion is used as a paste for direct writing printing forming to form a component with a complex shape, and then the hierarchical porous ceramic is obtained through the steps of heat curing, degreasing and sintering. The method utilizes the heat curing characteristics of the epoxy resin, combines the simple and convenient characteristics of the emulsion method and the adjustable characteristics of the pore structure, realizes rapid curing forming, provides a new paste source for the direct writing printing forming technology, and prepares the hierarchical porous ceramic with the complex shape.

Description

TECHNICAL FIELD

[0001] The application relates to a method for preparing a hierarchical porous ceramic based on a heat-sensitive emulsion combined with direct ink writing (DIW) printing, and belongs to the technical field of porous ceramic materials. BACKGROUND

[0002] Porous ceramics combine the porous structure and ceramic materials to form a material with excellent properties such as high temperature resistance, corrosion resistance, high specific surface area, high porosity, small dielectric loss, good electrical insulation, high specific strength, etc., and is widely used in thermal insulation, catalyst carrier, fluid filtration, biological scaffold, etc. However, due to the limitation of pore size, the application of porous materials has certain limitations.

[0003] Traditional methods for preparing porous ceramics include direct foaming method, freeze-drying method, organic impregnation method, emulsion method, etc., most of which cannot accurately control the pore morphology and porosity. Although the emulsion droplets can adjust the pore morphology and porosity in a relatively easy way, there are still problems such as long production cycle, difficulty in forming complex structures, and excessive waste of raw materials. Direct ink writing (DIW) is an economical and time-saving additive manufacturing technology based on extrusion molding, which can accurately control the printed structure according to computer-aided design. By combining DIW with the emulsion method, the micron-scale or even nanometer-scale pore structure generated by the emulsion slurry itself can be combined with the millimeter-scale large pores formed by the printing filament column path framework, forming a hierarchical pore structure, breaking the limitations of single pore size materials, and obtaining complex shape structural parts that meet the needs of various scenes.

[0004] At present, the paste of DIW is usually composed of ceramic powder, deionized water and organic binder, and its solidification process mainly relies on the drying and volatilization of solvents at room temperature or under heating. The emulsion mentioned in the literature for DIW molding of paste is also limited to relying on subsequent drying at room temperature for solidification. The uneven volatilization speed of solvents during drying and solidification can easily lead to internal stress and cracks in the green body; and the drying and solidification process requires a long time, affecting the production efficiency; the drying process relies on environmental humidity and temperature, which is difficult to control accurately. Therefore, it is necessary to further design a simple and efficient controllable ceramic slurry that can be used for DIW printing and realize the rapid solidification and molding of complex shape green bodies, greatly improving the production rate while achieving customized production.

[0005] After molding by the emulsion method, the green body usually needs to go through a long drying and solidification process, and during this process, the green body is only supported by the van der Waals force between the raw material powders, and the strength is relatively low. In order to accelerate the solidification speed of the emulsion, methods such as photocuring, microwave curing, ultrasonic-assisted curing, and thermal curing are commonly used in existing research. Compared with other solidification methods, thermal solidification is suitable for a variety of emulsion systems, has relatively simple equipment requirements, is easy to control temperature and reaction conditions, has high uniformity, and the reaction is controllable, which can realize large-scale production.

[0006] Among the existing patents related to the thermal curing of emulsions, Chinese patent CN105153353A prepares an acrylate emulsion for the surface of stretched polyester film. The emulsion preparation cycle is relatively long, and the resource consumption is relatively large. The emulsion state introduces a three-dimensional network structure through different types of acrylic monomers, and the system does not contain a curing agent. Only when the coating liquid is prepared can the hydroxyl group in the acrylate emulsion react with the curing agent to further increase the spatial network structure. At the same time, the emulsifier used to stabilize the resin and water phase also participates in the curing cross-linking reaction, affecting too many parameters of the emulsion curing. The emulsion preparation process does not involve the addition of ceramic particles, and the resin is part of the final product, participating in the surface coating application of the polyester film.

[0007] Chinese patent CN104877302A prepares a water-based epoxy-modified phenolic resin emulsion for preparing adhesives. The main body of the emulsion is still phenolic resin, and the main role of the epoxy resin is to modify the phenolic resin to increase the adhesion of the emulsion. It is not used as a continuous phase to regulate the pore structure. The co-solvent is used to improve the solubility and compatibility of different resins in the system, and does not volatilize, remaining in the emulsion and affecting further processing of the emulsion. Like Chinese patent CN105153353A, the emulsion system does not contain a curing agent, and the curing depends on the addition of a subsequent curing agent. The hydroxyl group in the pentaerythritol triacrylate reacts with the curing agent to form a three-dimensional network structure. The emulsion preparation process does not involve the addition of ceramic particles, and the resin is part of the final product, participating in the preparation of adhesives. In summary, the thermal curing of the emulsion has not yet involved the addition of ceramic particles, and the final product has not been applied to the preparation of ceramic materials.

[0008] Among the existing thermal curing methods for preparing ceramic organic solvent-based slurries, Chinese patent CN108285320A and Chinese patent CN108285321A mention that the curing time of the alkali-activated self-heating curing is usually controlled by the speed of the alkali-activated reaction, making it difficult to flexibly control the curing time and temperature. The microwave heating method proposed by Chinese patent CN110713387A has high equipment cost and complexity, and the penetration depth is limited. The above methods do not contain emulsion droplet templates in the slurry, and cannot achieve the preparation of porous ceramics. Moreover, the curing agent is a metal salt or ester pH adjuster that can release high-valent counterions. SUMMARY

[0009] The present application aims at the problem of difficult preparation of complex shape multi-level porous ceramics, and provides a method for preparing multi-level porous ceramics based on heat-sensitive emulsion combined with direct writing printing forming.

[0010] In the emulsion preparation process, amphiphilic particles with suitable contact angle modified by surfactants are irreversibly adsorbed at the oil-water interface, and due to the finiteness of polymerization, emulsion with controllable droplet size can be formed. Since the emulsion contains epoxy resin and curing agent, when heated, the epoxy groups in the epoxy resin react with the active hydrogen, amine group and anhydride functional groups in the curing agent to form a three-dimensional network structure, thereby realizing controllable heat curing. The second phase (aqueous phase) added in the emulsion evaporates during the curing process, forming the pore structure of the green body in situ. In addition, in the subsequent debinding and sintering process, the organic matter such as epoxy resin is removed to leave pores, and the millimeter-level macroporous structure is constructed by the DIW forming filament column path, and finally the multi-level porous structure ceramic is formed.

[0011] The specific technical solutions are as follows:

[0012] The present application provides a heat-sensitive emulsion for direct writing printing, which comprises a ceramic suspension, deionized water, a surfactant and a curing agent.

[0013] The ceramic suspension comprises ceramic powder and / or ceramic powder oxide sol nanoparticles, epoxy resin and diluent.

[0014] The diluent comprises active diluent and inert diluent.

[0015] Optionally, the epoxy resin accounts for 5-55 wt.% of the ceramic suspension; the diluent accounts for 5-50 wt.% of the ceramic suspension, wherein the mass ratio of active diluent to inert diluent is 1:(0.1-10); the ceramic suspension is supplemented to 100 wt.% by ceramic powder and / or ceramic powder oxide sol nanoparticles in addition to epoxy resin and diluent, and the solid content of the ceramic suspension is 5-85 wt.%.

[0016] The surfactant accounts for 0.2-20.0 wt.% of the mass of the ceramic powder and / or ceramic powder oxide sol nanoparticles.

[0017] The deionized water accounts for 5-200 wt.% of the total mass of the epoxy resin and the diluent.

[0018] The curing agent in the emulsion accounts for 1-50 wt.% of the mass of the epoxy resin.

[0019] Optionally, the ceramic powder is one or a mixture of two or more of alumina, silica, zirconia, ceria, titania, hydroxyapatite, β-tricalcium phosphate, silicon nitride, silicon carbide, fly ash, secondary aluminum ash, coal gangue, kaolin, tailings, metallurgical slag.

[0020] The ceramic powder oxide sol nanoparticles are one or a mixture of two or more of aluminum sol, silicon sol, zirconium sol, titanium sol, cerium sol.

[0021] Optionally, the epoxy resin is glycidyl ether epoxy resin, glycidyl amine epoxy resin or alicyclic epoxy resin.

[0022] Optionally, the active diluent is one or a mixture of two or more of methyl methacrylate, ethylene glycol acrylate, ethylene glycol, butanediol, ethylene glycol methyl ether, ethylene glycol ethyl ether, 1,4-cyclohexane dimethanol diglycidyl ether, 1,6-hexanediol diglycidyl ether.

[0023] The inert diluent is one or a mixture of two or more of xylene, trimethylbenzene, ethylbenzene, propylene glycol butyl ether, n-butanol, acetone, butyl butyrate, butyl propionate.

[0024] Optionally, the surfactant is one or a mixture of two or more of super dispersant 41000, triethanolamine lauryl sulfate, sodium lauryl sulfate, sodium α-alkenyl sulfonate, cocamide propyl betaine, cetyltrimethylammonium chloride, ethylene glycol, glycerol, Tween series, polyglycerol.

[0025] Optionally, the curing agent is one or a mixture of two or more of water-based polyamide curing agent, triethylenetetramine, water-based isocyanate curing agent, epoxy propane carboxylate, diethylenediamine, diisopropylamine, polyetheramine, 4,4'-diamine diphenyl ether, 3,3'-diamine dimethylbenzene, polyethyleneimine, 3,3'-diaminodipropylamine, dipropylamine triamine.

[0026] The ceramic powder, ceramic powder oxide sol nanoparticles, epoxy resin, active diluent, inert diluent, surfactant and curing agent described above can be in any ratio if they are a mixture of two or more of the specific substances listed above.

[0027] The application also provides a preparation method of a heat-sensitive emulsion for direct writing printing, which comprises the following steps:

[0028] Step 1, ceramic powder and / or ceramic powder oxide sol nanoparticles are added to a solution composed of epoxy resin and diluent, and a uniform ceramic suspension is obtained by ball milling;

[0029] Step 2, deionized water, surfactant and curing agent are added to the ceramic suspension obtained in step 1, and a uniform and stable emulsion is obtained by sufficient mechanical stirring. The function of this step is to activate the ceramic powder and / or ceramic powder oxide sol nanoparticles described in step 1 using surfactant, and to add a curing agent for curing the epoxy resin to the system.

[0030] The ball milling time in step 1 is 5 min - 48 h; the mechanical stirring conditions in step 2 are 300 - 3000 rpm, 5 min - 12 h.

[0031] A method for forming a hierarchical porous ceramic using the heat-sensitive emulsion described above, comprising the following steps:

[0032] Step 1, the heat-sensitive emulsion is used as a direct writing printing paste to directly write and print a hierarchical porous ceramic green body;

[0033] Step 2, the green body obtained in step 1 is subjected to heat curing, debinding and sintering steps to obtain a hierarchical porous ceramic.

[0034] Optionally, the process parameters for direct writing printing in step 1 are: printing speed 0.01 - 600 mm / s, nozzle inner diameter 0.1 - 3.6 mm, layer height 0.05 - 3.6 mm;

[0035] The heat curing temperature in step 2 is 25-150 ℃, and the processing time is 5 min - 15 h; the heating rate during debinding is 0.02 - 20 ℃ / min, the debinding temperature is 150 - 1300 ℃, and the holding time is 5 min - 12 h; the heating rate during sintering is 0.1 - 20 ℃ / min, the sintering temperature is 600 - 2000 ℃, and the holding time is 30 min - 12 h.

[0036] Compared with the prior art, the technical solution provided by the present application has the following beneficial effects:

[0037] The present application provides a new type of paste for DIW which can be quickly heat-cured after forming, and the paste contains milk drops as a scaffold derived pore template, through optimizing the DIW curing method to realize the rapid and controllable in-situ curing forming of the green body, obtain a multi-level pore structure ceramic with micron / nanometer and millimeter pore structure assembly, reduce the generation of green body crack, deformation and other defects, and greatly shorten the curing and drying time after forming, effectively control the stress distribution in the curing process, and improve the quality and production rate of the multi-level pore ceramic. And the pore structure, porosity and other parameters can be easily adjusted by adjusting the solid content, oil-water ratio, particle surface hydrophobicity, organic additive content and other factors.

[0038] The heat-sensitive emulsion combined with the method of direct writing printing forming multi-level pore ceramic has the advantages of simple process, low cost, and can prepare complex shape multi-level pore ceramic without mold, integrates the performance advantages of different pore structures, and makes the sample have the advantages of good transmittance, high specific strength, large specific surface area and the like, and has wide application prospect in the fields of heat insulation filtration, catalyst carrier, biomedical materials and the like. BRIEF DESCRIPTION OF DRAWINGS

[0039] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the drawings needed in the embodiment description will be briefly introduced. Obviously, the drawings in the following description are only some embodiments of the present application, and other drawings can be obtained by those skilled in the art without creative labor.

[0040] Figure 1 SEM image of the multi-level pore alumina green body scaffold prepared in Example 1.

[0041] Figure 2 SEM image of the multi-level pore alumina ceramic scaffold prepared in Example 1.

[0042] Figure 3 SEM image of the alumina green body scaffold prepared in Comparative Example 1.

[0043] Figure 4 SEM image of the alumina green body scaffold prepared in Comparative Example 2.

[0044] Figure 5 Comparison photos of the emulsions prepared in Comparative Example 3 and Example 1 and SEM images of the alumina green body scaffold: (a) photo of the emulsion prepared in Example 1; (b) photo of the emulsion prepared in Comparative Example 3; (c) SEM image of the green body scaffold.

[0045] Figure 6 SEM image of the alumina green body scaffold prepared in Comparative Example 4. DETAILED DESCRIPTION

[0046] In order to make the invention purposes, technical solutions and beneficial technical effects of the present application clearer, the present application will be described in detail below in conjunction with specific embodiments. It should be understood that the embodiments described in the specification are only for the purpose of explaining the present application, and are not intended to limit the present application.

[0047] A heat-sensitive emulsion for direct writing printing, the direct writing printing heat-sensitive emulsion comprising a ceramic suspension, deionized water, a surfactant and a curing agent;

[0048] The ceramic suspension comprises ceramic powder and / or ceramic powder oxide sol nanoparticles, an epoxy resin and a diluent.

[0049] The diluent comprises an active diluent and an inert diluent.

[0050] Optionally, the epoxy resin accounts for 5 – 55 wt.% of the ceramic suspension; the diluent accounts for 5 – 50 wt.% of the ceramic suspension, wherein the mass ratio of the active diluent to the inert diluent is 1: (0.1 – 10); the ceramic suspension is supplemented to 100 wt.% by the ceramic powder and / or ceramic powder oxide sol nanoparticles in addition to the epoxy resin and the diluent, and the solid content of the ceramic suspension is 5 – 85 wt.%.

[0051] If the total content of the diluent is not within the above process parameter range, the emulsion viscosity will be unsuitable, and a uniform and regular pore structure cannot be formed.

[0052] If the solid content of the ceramic suspension is not within the above process parameter range, the required pore structure cannot be formed.

[0053] The surfactant accounts for 0.2 – 20.0 wt.% of the mass of the ceramic powder and / or ceramic powder oxide sol nanoparticles. If the content of the surfactant is not within the above process parameter range, the emulsion will be unstable, and the water phase will separate out, and a pore structure cannot be formed.

[0054] The deionized water accounts for 5 – 200 wt.% of the total mass of the epoxy resin and the diluent. If the amount of the deionized water is not within the above process parameter range, the second phase ratio cannot reach the required conditions for the technical effects of the present application, and a pore structure cannot be formed.

[0055] The curing agent in the emulsion accounts for 1 – 50 wt.% of the mass of the epoxy resin.

[0056] Optionally, the ceramic powder is one or a mixture of two or more of alumina, silica, zirconia, ceria, titanium dioxide, hydroxyapatite, β-tricalcium phosphate, silicon nitride, silicon carbide, fly ash, secondary aluminum ash, coal gangue, kaolin, tailings and metallurgical slag.

[0057] The ceramic powder oxide sol nanoparticles are one of alumina sol, silica sol, zirconia sol, titania sol, ceria sol or a mixture of two or more thereof.

[0058] Optionally, the epoxy resin is glycidyl ether epoxy resin, glycidyl amine epoxy resin or alicyclic epoxy resin.

[0059] Optionally, the reactive diluent is one of methyl methacrylate, ethylene glycol acrylate, ethylene glycol, butanediol, ethylene glycol methyl ether, ethylene glycol ethyl ether, 1,4-cyclohexane dimethanol diglycidyl ether, 1,6-hexanediol diglycidyl ether or a mixture of two or more thereof.

[0060] The inert diluent is one of xylene, trimethylbenzene, ethylbenzene, propylene glycol butyl ether, n-butanol, acetone, butyl butyrate, butyl propionate or a mixture of two or more thereof.

[0061] Optionally, the surfactant is one of super dispersant 41000, triethanolamine lauryl sulfate, sodium dodecyl sulfate, sodium alpha-alkenyl sulfonate, cocamide propyl betaine, cetyltrimethylammonium chloride, ethylene glycol, glycerol, Tween series, polyglycerol.

[0062] Optionally, the curing agent is one of water-based polyamide curing agent, triethylenetetramine, water-based isocyanate curing agent, epoxy propane carboxylate, diethylenediamine, diisopropylamine, polyetheramine, 4,4'-diamine diphenyl ether, 3,3'-diamine dimethylbenzene, polyethyleneimine, 3,3'-diaminodipropylamine, dipropylamine triamine or a mixture of two or more thereof.

[0063] The application also provides a preparation method of a heat-sensitive emulsion for direct writing printing, which comprises the following steps:

[0064] Step 1: adding ceramic powder and / or ceramic powder oxide sol nanoparticles into a solution composed of epoxy resin and diluent, and mixing by ball milling to obtain a uniform ceramic suspension;

[0065] Step 2: adding surfactant, deionized water and curing agent into the ceramic suspension obtained in step 1, and fully mechanically stirring to obtain a uniform and stable emulsion.

[0066] In step 1, the ball milling time is 5 min – 48 h; in step 2, the mechanical stirring condition is 300 – 3000 rpm, 5 min – 12 h.

[0067] A method for directly writing and printing a multi-level hole ceramic using the heat-sensitive emulsion described above, which comprises the following steps:

[0068] Step 1, heat-sensitive emulsion as direct writing printing paste, direct writing printing multi-level hole ceramic green body;

[0069] Step 2, the green body obtained in step 1 is subjected to heat curing, debinding and sintering steps to obtain a multi-level hole ceramic.

[0070] Optionally, the process parameters of the direct writing printing in step 1 are: printing speed 0.01 - 600 mm / s, nozzle inner diameter 0.1 - 3.6 mm, layer height 0.05 - 3.6 mm;

[0071] The heat curing temperature in step 2 is 25-150 ℃, and the processing time is 5 min - 15 h; the heating rate during the debinding process is 0.02 - 20 ℃ / min, the debinding temperature is 150 - 1300 ℃, and the holding time is 5 min - 12 h; the heating rate during the sintering process is 0.1 - 20 ℃ / min, the sintering temperature is 600 - 2000 ℃, and the holding time is 30 min - 12 h.

[0072] Example 1

[0073] (1) Alumina powder was added as an initial raw material to a solution composed of bisphenol A type epoxy resin E-51, butanediol, and xylene, and a uniform ceramic suspension was prepared by ball milling for 12 h. The solid content of the ceramic suspension was 60 wt.%, the epoxy resin accounted for 35 wt.% of the ceramic suspension, the butanediol accounted for 1 wt.% of the ceramic suspension, and the xylene accounted for 4 wt.% of the ceramic suspension.

[0074] (2) A certain amount of triethanolamine lauryl sulfate, deionized water, and triethylene tetramine was added to the above obtained ceramic suspension, and a stable particle stabilized emulsion was prepared by mechanical stirring at 2500 rpm for 1 h. The surfactant triethanolamine lauryl sulfate in the emulsion accounted for 20 wt.% of the mass of the powder, deionized water as the second phase accounted for 50 wt.% of the total mass of the epoxy resin and diluent, and the curing agent triethylene tetramine accounted for 20 wt.% of the epoxy resin.

[0075] (3) The above obtained emulsion was used as a paste for direct writing printing, and a green body with a complex structure was printed under the conditions of a printing speed of 5 mm / s, a nozzle inner diameter of 2.1 mm, and a layer height of 2.1 mm. After heat curing at 80 ℃ for 2 h, debinding at a heating rate of 0.5 ℃ / min to 700 ℃ for 1 h, and sintering at a heating rate of 1 ℃ / min to 1500 ℃ for 3 h, a multi-level hole alumina ceramic was obtained.

[0076] Example 2

[0077] (1) The aluminum sol powder was added as the initial raw material to a solution composed of epoxy sorbitol glycidyl ether, 1,4-cyclohexane dimethanol diglycidyl ether, and acetone, and a uniform ceramic suspension was prepared by ball milling for 12 h. The solid content of the ceramic suspension was 34 wt.%, the epoxy resin accounted for 55 wt.% of the ceramic suspension, 1,4-cyclohexane dimethanol diglycidyl ether accounted for 10 wt.% of the ceramic suspension, and acetone accounted for 1 wt.% of the ceramic suspension.

[0078] (2) A certain amount of super dispersant 41000, deionized water, and polyether amine were added to the ceramic suspension obtained above, and a stable particle-stabilized emulsion was prepared by fully mechanical stirring at 2000 rpm for 40 min. The super dispersant 41000 in the emulsion accounted for 0.2 wt.% of the powder, deionized water accounted for 5 wt.% of the total mass of the epoxy resin and diluent as the second phase, and the curing agent polyether amine accounted for 50 wt.% of the epoxy resin.

[0079] (3) The emulsion obtained above was used as the paste for direct writing printing, and a green body with a complex structure was printed under the conditions of a printing speed of 6 mm / s, a nozzle inner diameter of 2 mm, and a layer height of 2 mm. After heat curing at 25 °C for 15 h, the green body was debound by heating at a rate of 0.02 °C / min to 150 °C for 12 h and then sintered by heating at a rate of 0.1 °C / min to 1300 °C for 30 min to obtain a hierarchical porous aluminum oxide ceramic.

[0080] Example 3

[0081] (1) The hydroxyapatite and β-tricalcium phosphate powders were added as the initial raw material to a solution composed of epoxy ethylene glycol diglycidyl ether, ethylene glycol ethyl ether, and ethylbenzene, and a uniform ceramic suspension was prepared by ball milling for 8 h. The solid content of the ceramic suspension was 39 wt.%, the epoxy resin accounted for 50 wt.% of the ceramic suspension, ethylene glycol ethyl ether accounted for 1 wt.% of the ceramic suspension, and ethylbenzene accounted for 10 wt.% of the ceramic suspension.

[0082] (2) A certain amount of sodium dodecyl sulfate, super dispersant 41000, deionized water, and polyethyleneimine were added to the ceramic suspension obtained above, and a stable particle-stabilized emulsion was prepared by fully mechanical stirring at 1200 rpm for 40 min. The sodium dodecyl sulfate and super dispersant 41000 in the emulsion were used for hydrophobic modification of the mixed powders, and the total amount of the two surfactants added was 10 wt.% of the total mass of the powders, the mass ratio of the two surfactants was sodium dodecyl sulfate: super dispersant 41000 = 2:1, deionized water accounted for 200 wt.% of the total mass of the epoxy resin and diluent as the second phase, and the curing agent polyethyleneimine accounted for 12.5 wt.% of the epoxy resin.

[0083] (3) The obtained emulsion was used as a paste for direct writing printing, and a green body with a complex structure was printed at a printing speed of 100 mm / s, a nozzle inner diameter of 1.2 mm, and a layer height of 1.2 mm, and then was heat cured at 70 ℃ for 2 h, heated to 1300 ℃ at a heating rate of 1 ℃ / min and kept for 5 min, and then was debound at a heating rate of 2 ℃ / min and sintered at 1500 ℃ for 3 h to obtain a hierarchical porous biphasic calcium phosphate ceramic.

[0084] Example 4

[0085] (1) The silicon nitride powder was added to a solution composed of bisphenol A type epoxy resin E-44, ethylene glycol acrylate, and n-butanol as initial raw materials, and a uniform ceramic suspension was prepared by ball milling for 5 min. The solid content of the ceramic suspension was 5 wt.%, the epoxy resin accounted for 45 wt.% of the ceramic suspension, the ethylene glycol acrylate accounted for 30 wt.% of the ceramic suspension, and the n-butanol accounted for 20 wt.% of the ceramic suspension.

[0086] (2) A certain amount of Tween 80, deionized water, and 3,3'-diaminodipropylamine was added to the obtained ceramic suspension, and a stable particle-stabilized emulsion was prepared by mechanical stirring at 300 rpm for 5 min. The Tween 80 in the emulsion accounted for 10 wt.% of the powder mass, the deionized water as the second phase accounted for 50 wt.% of the total mass of the epoxy resin and the diluent, and the curing agent 3,3'-diaminodipropylamine accounted for 1 wt.% of the epoxy resin.

[0087] (3) The obtained emulsion was used as a paste for direct writing printing, and a green body with a complex structure was printed at a printing speed of 600 mm / s, a nozzle inner diameter of 0.1 mm, and a layer height of 0.05 mm, and then was heat cured at 150 ℃ for 5 min, debound at a heating rate of 20 ℃ / min and heated to 700 ℃ for 1 h, and then sintered at a heating rate of 20 ℃ / min and heated to 2000 ℃ for 2 h to obtain a hierarchical porous silicon nitride ceramic.

[0088] Example 5

[0089] (1) The fly ash and secondary aluminum ash powder were added to a solution composed of bisphenol F type epoxy resin DER 354, 1,6-hexanediol diglycidyl ether, and ethylbenzene as initial raw materials, and a uniform ceramic suspension was prepared by ball milling for 48 h. The solid content of the ceramic suspension was 85 wt.%, the epoxy resin accounted for 5 wt.% of the ceramic suspension, the 1,6-hexanediol diglycidyl ether accounted for 6 wt.% of the ceramic suspension, and the ethylbenzene accounted for 4 wt.% of the ceramic suspension.

[0090] (2) A certain amount of glycerol, deionized water and diethylenediamine were added to the above obtained ceramic suspension, and a stable particle-stabilized emulsion was prepared by fully mechanical stirring at 3000 rpm for 12 h. The glycerol in the emulsion accounted for 5 wt.% of the mass of the powder, the deionized water as the second phase accounted for 70 wt.% of the total mass of the epoxy resin and diluent, and the curing agent diethylenediamine accounted for 13.8 wt.% of the epoxy resin.

[0091] (3) The above obtained emulsion was used as a paste for direct writing printing, and a green body with a complex structure was printed under the conditions of a printing speed of 0.01 mm / s, a nozzle inner diameter of 3.6 mm, and a layer height of 3.6 mm. After heat curing at 80 ℃ for 5 h, heating to 300 ℃ at a heating rate of 0.5 ℃ / min and holding for 2 h for debinding, and heating to 600 ℃ at a heating rate of 1 ℃ / min and holding for 12 h for sintering, a hierarchical pore mullite ceramic was obtained.

[0092] Comparative Example 1

[0093] (1) Alumina powder was added to a solution composed of bisphenol A type epoxy resin E-51, butanediol, and dimethylbenzene as an initial raw material, and a uniform ceramic suspension was prepared by ball milling for 12 h. The solid content of the ceramic suspension was 88 wt.%, the epoxy resin accounted for 6 wt.% of the ceramic suspension, the butanediol accounted for 4 wt.% of the ceramic suspension, and the dimethylbenzene accounted for 2 wt.% of the ceramic suspension.

[0094] (2) A certain amount of triethanolamine lauryl sulfate, deionized water and triethylene tetramine were added to the above obtained ceramic suspension, and a stable particle-stabilized emulsion was prepared by fully mechanical stirring at 1000 rpm for 30 min. The surfactant triethanolamine lauryl sulfate in the emulsion accounted for 7 wt.% of the mass of the powder, the deionized water as the second phase accounted for 50 wt.% of the total mass of the epoxy resin and diluent, and the curing agent triethylene tetramine accounted for 20 wt.% of the epoxy resin.

[0095] (3) The above obtained emulsion was used as a paste for direct writing printing, and a green body with a complex structure was printed under the conditions of a printing speed of 10 mm / s, a nozzle inner diameter of 1.5 mm, and a layer height of 1.5 mm. The SEM image of the green body support (attached Figure 3 ) was observed, and when the solid content was outside the parameter range of 5-85 wt.% specified in the present application, there was no pore structure, and the preparation of the hierarchical pore ceramic material described in the present application could not be achieved.

[0096] Comparative Example 2

[0097] (1) Alumina powder as the initial raw material is added to a solution composed of bisphenol A type epoxy resin E-51, butanediol, dimethylbenzene, and a uniform ceramic suspension is prepared by ball milling for 12 h. The solid content of the ceramic suspension is 60 wt.%, the epoxy resin accounts for 37 wt.% of the ceramic suspension, butanediol accounts for 2 wt.% of the ceramic suspension, and dimethylbenzene accounts for 1 wt.% of the ceramic suspension.

[0098] (2) A certain amount of triethanolamine lauryl sulfate, deionized water, and triethylene tetramine is added to the obtained ceramic suspension, and a stable particle-stable emulsion is prepared by fully mechanical stirring at 1000 rpm for 30 min. The surfactant triethanolamine lauryl sulfate in the emulsion accounts for 7 wt.% of the powder mass, deionized water as the second phase accounts for 50 wt.% of the total mass of the epoxy resin and diluent, and the curing agent triethylene tetramine accounts for 20 wt.% of the epoxy resin.

[0099] (3) The obtained emulsion is used as a paste for direct writing printing, and a green body with a complex structure is printed under the conditions of a printing speed of 10 mm / s, a nozzle inner diameter of 1.5 mm, and a layer height of 1.5 mm. The SEM image of the green body support (attached Figure 4 ) shows that when the total content of the diluent is less than the parameter range of 5-50 wt.% specified in the present application, the emulsion viscosity is too large, the pore structure is uneven and irregular, and the preparation of the multi-level porous ceramic material with the technical effects described in the present application cannot be achieved.

[0100] Comparative Example 3

[0101] (1) Aluminum sol powder is used as the initial raw material and is added to a solution composed of epoxy sorbitol glycidyl ether, 1,4-cyclohexanedimethanol diglycidyl ether, and acetone, and a uniform ceramic suspension is prepared by ball milling for 12 h. The solid content of the ceramic suspension is 30 wt.%, the epoxy resin accounts for 35 wt.% of the ceramic suspension, 1,4-cyclohexanedimethanol diglycidyl ether accounts for 23.33 wt.% of the ceramic suspension, and acetone accounts for 11.67 wt.% of the ceramic suspension.

[0102] (2) A certain amount of Hyperdispersant 41000, deionized water, and polyether amine is added to the obtained ceramic suspension, and an emulsion is prepared by fully mechanical stirring at 2000 rpm for 40 min. The Hyperdispersant 41000 in the emulsion accounts for 30 wt.% of the powder mass, deionized water as the second phase accounts for 20 wt.% of the total mass of the epoxy resin and diluent, and the curing agent polyether amine accounts for 33.33 wt.% of the epoxy resin.

[0103] (3) The emulsion obtained above is used as a paste for direct writing printing forming, and a green body with a complex structure is printed under the conditions of a printing speed of 6 mm / s, a nozzle inner diameter of 2 mm, and a layer height of 2 mm. When the content of the surfactant is out of the range of 0.2-20.0 wt.% of the powder mass specified in the present application, the emulsion is unstable, and the aqueous phase is precipitated (see FIG. 6). Figure 5 The SEM image of the green body support is observed, and there is no pore structure, and the preparation of the hierarchical porous ceramic material with the technical effects described in the present application cannot be achieved.

[0104] Comparative Example 4

[0105] (1) The aluminum sol powder is added to a solution composed of epoxy sorbitol glycidyl ether, 1,4-cyclohexane dimethanol diglycidyl ether, and acetone, and a uniform ceramic suspension is prepared by ball milling for 12 h. The solid content of the ceramic suspension is 30 wt.%, the epoxy resin accounts for 35 wt.% of the ceramic suspension, the 1,4-cyclohexane dimethanol diglycidyl ether accounts for 23.33 wt.% of the ceramic suspension, and the acetone accounts for 11.67 wt.% of the ceramic suspension.

[0106] (2) A certain amount of Hyperdispersant 41000, deionized water, and polyether amine are added to the ceramic suspension obtained above, and a stable particle-stabilized emulsion is prepared by fully mechanical stirring at 2000 rpm for 40 min. The Hyperdispersant 41000 in the emulsion accounts for 7.5 wt.% of the powder mass, the deionized water as the second phase accounts for 2 wt.% of the total mass of the epoxy resin and the diluent, and the curing agent polyether amine accounts for 33.33 wt.% of the epoxy resin.

[0107] (3) The emulsion obtained above is used as a paste for direct writing printing forming, and a green body with a complex structure is printed under the conditions of a printing speed of 6 mm / s, a nozzle inner diameter of 2 mm, and a layer height of 2 mm. The SEM image of the green body support is observed (see FIG. 6), and when the deionized water is less than the range of 5-200 wt.% of the total mass of the epoxy resin and the diluent specified in the present application, the proportion of the second phase is too low, there is no pore structure, and the preparation of the hierarchical porous ceramic material with the technical effects described in the present application cannot be achieved. Figure 6

[0108] In summary, from the various comparative examples and the attached Figures 3-6 It can be seen that when the key process conditions (solid content, diluent, surfactant, deionized water) are not within the protection scope of the present application, the hierarchical porous ceramic material cannot be successfully prepared.

[0109] ​The above merely illustrates the specific embodiments of the present application, but the protection scope of the present application is not limited thereto. Any skilled person in the art can easily think of various equivalent modifications or replacements within the technical range disclosed by the present application, and these modifications or replacements shall be covered within the protection scope of the present application. Therefore, the protection scope of the present application shall be subject to the protection scope determined by the claims.

Claims

1. A heat-sensitive emulsion for direct-write printing, characterized by: The direct writing printing heat-sensitive emulsion comprises a ceramic suspension, a curing agent, deionized water and a surfactant; The ceramic suspension comprises ceramic powder and / or ceramic powder oxide sol nanoparticles, an epoxy resin and a diluent; The diluent comprises an active diluent and an inert diluent; The surfactant is a mixture of one or more than two of super dispersant 41000, triethanolamine lauryl sulfate, sodium lauryl sulfate, sodium alpha-alkenyl sulfonate, cocamide propyl betaine, cetyltrimethylammonium chloride and Tween series; The epoxy resin accounts for 5-55 wt.% of the ceramic suspension; the diluent accounts for 5-50 wt.% of the ceramic suspension, and the mass ratio of the active diluent to the inert diluent is 1:(0.1-10); the ceramic suspension is supplemented to 100 wt.% by the ceramic powder and / or ceramic powder oxide sol nanoparticles in addition to the epoxy resin and the diluent, and the solid content of the ceramic suspension is 5-85 wt.%; The surfactant accounts for 0.2-20.0 wt.% of the mass of the ceramic powder and / or ceramic powder oxide sol nanoparticles; The deionized water accounts for 5-200 wt.% of the total mass of the epoxy resin and the diluent The curing agent accounts for 1-50 wt.% of the mass of the epoxy resin in the emulsion.

2. A heat-sensitive emulsion for direct-write printing according to claim 1, characterized in that: The ceramic powder is one or a mixture of more than two of alumina, silica, zirconia, ceria, titanium dioxide, hydroxyapatite, beta-tricalcium phosphate, silicon nitride, silicon carbide, fly ash, secondary aluminum ash, coal gangue, kaolin, tailings and metallurgical slag; The ceramic powder oxide sol nanoparticles are one or a mixture of more than two of aluminum sol, silicon sol, zirconium sol, titanium sol and cerium sol.

3. A heat-sensitive emulsion for direct-write printing according to claim 2, characterized in that: The epoxy resin is one or a mixture of more than two of glycidyl ether epoxy resin, glycidyl amine epoxy resin and alicyclic epoxy resin.

4. A heat-sensitive emulsion for direct-write printing according to claim 3, characterized in that: The active diluent is one or a mixture of more than two of methyl methacrylate, ethylene glycol acrylate, ethylene glycol, butanediol, ethylene glycol methyl ether, ethylene glycol ethyl ether, 1,4-cyclohexane dimethanol diglycidyl ether and 1,6-hexanediol diglycidyl ether. The inert diluent is one or a mixture of more than two of xylene, trimethylbenzene, ethylbenzene, propylene glycol butyl ether, n-butanol, acetone, butyl butyrate and butyl propionate.

5. A heat-sensitive emulsion for direct-write printing according to claim 4, characterized in that: The curing agent is one or a mixture of more than two of water-based polyamide curing agent, triethylene tetramine, water-based isocyanate curing agent, epoxy propane carboxylate, diethylenediamine, diisopropylamine, polyetheramine, 4,4'-diamine diphenyl ether, 3,3'-diamine xylene, polyethylene imine, 3,3'-diamino dipropylamine and dipropyl triamine.

6. A method for the preparation of a heat-sensitive emulsion for direct-write printing according to any one of claims 1 to 5, characterized in that The method comprises the following steps: Step 1: adding the ceramic powder and / or ceramic powder oxide sol nanoparticles to a solution composed of the epoxy resin and the diluent, and mixing by ball milling to obtain a uniform ceramic suspension; Step 2: adding the surfactant, deionized water and curing agent to the ceramic suspension obtained in step 1, and fully mechanically stirring to obtain a uniform and stable emulsion; Wherein, the ball milling time in step 1 is 5 min – 48 h; the mechanical stirring condition in step 2 is 300 – 3000 rpm, 5 min – 12 h.

7. A method for forming hierarchical porous ceramics by direct writing printing of a heat- sensitive emulsion according to any one of claims 1 to 5, characterized in that, Comprising the following steps: Step 1, printing the heat-sensitive emulsion as a direct writing printing paste, and direct writing printing the multi-level porous ceramic green body; Step 2, obtaining the multi-level porous ceramic through the steps of heat curing, debinding and sintering of the green body obtained in step 1.

8. The method for forming a multi-level porous ceramic by direct writing printing according to claim 7, characterized in that: The process parameters of the direct writing printing in step 1 are: printing speed 0.01 – 600 mm / s, nozzle inner diameter 0.1 – 3.6 mm, layer height 0.05 – 3.6 mm; The heat curing temperature in step 2 is 25-150 ℃, and the processing time is 5 min – 15 h; the heating rate during the debinding process is 0.02 – 20 ℃ / min, the debinding temperature is 150 – 1300 ℃, and the holding time is 5 min – 12 h; the heating rate during the sintering process is 0.1 – 20 ℃ / min, the sintering temperature is 600 – 2000 ℃, and the holding time is 30 min – 12 h.

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