A tape casting method for mullite porous ceramic material

Abstract

The invention discloses a tape-casting method for a porous mullite ceramic material, and relates to the technical field of porous ceramic forming methods. The tape-casting method for a porous mullite ceramic material comprises the following steps: mixing SiO2-Al2O3 hollow microspheres and a sintering aid, then adding a dispersant, a plasticizer, a binder, and water thereto and stirring evenly to obtain a slurry; after tape-casting the slurry, a ceramic green body is obtained; the ceramic green body is subjected to binder removal and sintering to obtain a porous mullite ceramic material; the slurry is composed of the following components by mass fraction: SiO2-Al2O3 hollow microspheres 40-50wt%, a sintering aid 9.5-20%, a dispersant 0.5-2.5wt%, a binder 1-3wt%, a plasticizer 1-3wt%, and a water balance. The tape casting method of the present invention has a simple process and high efficiency. During the operation of the method, SiO2-Al2O3 hollow microspheres are used for self-foaming to form pores, without the need for an external foaming agent and using an inorganic pore-forming agent, which can reduce pollution, save costs and make the operation process of the method more environmentally friendly.

Description

Technical Field

[0001] The invention relates to the technical field of porous ceramic forming methods, in particular to a tape casting forming method for a mullite porous ceramic material. Background Art

[0002] Porous ceramics are an inorganic non-metallic material containing a large number of pores. They have excellent properties such as high porosity, high permeability, large specific surface area, low volume density and low thermal conductivity. They are widely used in chemical, metallurgical, energy and thermal engineering fields.

[0003] Gel casting is one of the most commonly used processes for preparing porous ceramics. Using simple equipment, it can produce porous ceramics with complex shapes. The "Method for Preparing Porous Ceramic Composite Materials by Protein Foaming" (Chinese invention patent application CN101967064A) uses egg white as a foaming agent and polysaccharides as a gelling agent to prepare porous ceramics such as mullite, silica, and alumina through gel casting. The ceramic bodies prepared by this method require a temperature of 75-85°C to solidify, and the amount of organic matter used is relatively high. Although the foaming and gelling agents used are non-toxic, the combustion of large amounts of organic matter during the sintering process can cause serious environmental pollution.

[0004] Chinese invention patent CN201410694716.6 discloses a mullite porous ceramic material and a preparation method thereof, which uses a foaming agent and mullite to foam in a specific ratio to prepare the mullite porous ceramic material. The curing time is long, and the subsequent calcination temperature is high, the cost is high, and it is not environmentally friendly.

[0005] Therefore, it is necessary to study a tape casting method for mullite porous ceramic materials, which can tape cast the mullite porous ceramic materials without or with little foaming agent, while reducing production costs and making the process more environmentally friendly. Summary of the Invention

[0006] The purpose of the present invention is to overcome the above-mentioned technical deficiencies and solve the problems that a foaming agent needs to be added or too much foaming agent is added during the operation of the existing mullite porous ceramic material method, resulting in environmental pollution and the problem that the operation process of the method is too costly; the present invention proposes a tape casting method for mullite porous ceramic material, which has a simple process and high efficiency. During the operation of the method, SiO2-Al2O3 hollow microspheres are used for self-foaming to form pores, without the need for an external foaming agent and using an inorganic pore-forming agent, which can reduce pollution, save costs, make the operation process of the method more environmentally friendly, and at the same time increase the through-porosity of the product.

[0007] The present invention also provides a mullite porous ceramic material prepared by the tape casting method of the above-mentioned mullite porous ceramic material. The product has high through-porosity, good consistency, high yield rate and smooth surface, which is conducive to subsequent thick film or thin film printing.

[0008] Specifically, the present invention discloses a tape casting method for a mullite porous ceramic material, comprising the following steps:

[0009] SiO2-Al2O3 hollow microspheres and a sintering aid are mixed, and then a dispersant, a plasticizer, a binder and water are added thereto and stirred evenly to obtain a slurry; the slurry is tape-cast to obtain a ceramic green body; the ceramic green body is subjected to binder removal and sintering to obtain a mullite porous ceramic material;

[0010] The slurry is composed of the following components by mass fraction: 40-50wt% SiO2-Al2O3 hollow microspheres, 9.5-20% sintering aid, 0.5-2.5wt% dispersant, 1-3wt% binder, 1-3wt% plasticizer, and the balance water.

[0011] Preferably, the sintering aid includes B2O3, CaCO3, AlF3 and glass powder; the content of AlF3 in the slurry is 3-6wt%.

[0012] Preferably, in the slurry, the content of B2O3 is 1-3wt%, the content of CaCO3 is 1.5-4wt%, and the content of glass powder is 4-7wt%.

[0013] Preferably, the SiO2-Al2O3 hollow microspheres have a diameter of 100-200 μm and an impurity content of less than 1%.

[0014] Preferably, the dispersant is selected from at least one of ammonium polyacrylate and polyethylene glycol octylphenyl ether.

[0015] Preferably, the binder is selected from a mixture of one or more of water glass, sodium carboxymethyl cellulose, polyvinyl alcohol, and thermoplastic polyvinyl butyral resin.

[0016] Preferably, the plasticizer is selected from at least one of dibutyl phthalate and polyethylene glycol.

[0017] Preferably, the debinding process is to heat the material to 400-500° C. at a heating rate of 0.5-1.5° C. / min and keep the temperature for 2-4 hours.

[0018] Preferably, the sintering is to heat the material to 1150-1250° C. at a heating rate of 5-8° C. / min and keep the temperature for 2-3 hours.

[0019] The present invention also discloses a mullite porous ceramic material, which is prepared by the tape casting method of the mullite porous ceramic material. The porosity of the mullite porous ceramic material is 60-85%, the through-hole diameter is 40-110 μm, and the strength is 10-30 MPa.

[0020] Compared with the prior art, the present invention has the following beneficial effects:

[0021] (1) The tape-casting method of the mullite porous ceramic material of the present invention has a simple process and high efficiency. During the operation of the method, SiO2-Al2O3 hollow microspheres are used for self-foaming to form pores, no external foaming agent is required, and an inorganic pore-forming agent is selected. This can reduce pollution, save costs, make the operation process of the method more environmentally friendly, and at the same time increase the through-porosity of the product. At the same time, the temperature of the debinding and sintering methods used in the method is low, which is convenient for operation and reduces costs, and is suitable for large-scale production.

[0022] (2) The mullite porous ceramic material of the present invention is prepared by the tape casting method of the mullite porous ceramic material. The product has a high through-porosity, good consistency, high yield rate, and a smooth surface, which is conducive to subsequent thick film or thin film printing; at the same time, the product has a porosity of 60-85%, a through-hole diameter of 40-110um, and a strength of 10-30MPa. It has good performance characteristics and is suitable for the preparation of atomization cores and other purposes. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] In order to more clearly illustrate the technical solution of the present invention, the following is a brief introduction to the drawings required for use in the description of the embodiments. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0024] Figure 1 Schematic diagram of the mullite porous ceramic material prepared in Example 2 of the present invention;

[0025] Figure 2 Schematic diagram of the porous ceramic material prepared in Comparative Example 5. DETAILED DESCRIPTION

[0026] The following will be combined with the accompanying drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the embodiments described are only part of the embodiments of the present invention, not all of the embodiments, and are only used to explain the present invention and are not intended to limit the scope of protection of the present invention.

[0027] Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making any creative work shall fall within the scope of protection of the present invention.

[0028] It will be understood that when used in this specification and the appended claims, the terms “comprises” and “comprising” indicate the presence of described features, integers, steps, operations, elements and / or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components and / or groups thereof.

[0029] It should also be understood that the terminology used in this specification is for the purpose of describing particular embodiments only and is not intended to limit the present invention. As used in the specification and appended claims, the singular forms "a," "an," and "the" are intended to include the plural forms unless the context clearly indicates otherwise.

[0030] It should be further understood that the term "and / or" used in the present description and the appended claims refers to and includes any and all possible combinations of one or more of the associated listed items.

[0031] A tape casting method for a mullite porous ceramic material,

[0032] The following steps are involved:

[0033] SiO2-Al2O3 hollow microspheres and a sintering aid are mixed, and then a dispersant, a plasticizer, a binder and water are added thereto and stirred evenly to obtain a slurry; the slurry is tape-cast to obtain a ceramic green body; the ceramic green body is subjected to binder removal and sintering to obtain a mullite porous ceramic material;

[0034] The slurry is composed of the following components by mass fraction: 40-50wt% SiO2-Al2O3 hollow microspheres, 9.5-20% sintering aid, 0.5-2.5wt% dispersant, 1-3wt% binder, 1-3wt% plasticizer, and the balance water.

[0035] The diameter of SiO2-Al2O3 hollow microspheres is 100-200 μm, and the impurity content is less than 1%.

[0036] The sintering aids include B2O3, CaCO3, AlF3 and glass powder; the content of the AlF3 in the slurry is 3-6wt%.

[0037] In the slurry, the content of B2O3 is 1-3wt%, the content of CaCO3 is 1.5-4wt%, and the content of glass powder is 4-7wt%.

[0038] The dispersant is selected from at least one of ammonium polyacrylate and polyethylene glycol octylphenyl ether.

[0039] The binder is selected from a mixture of one or more of water glass, sodium carboxymethyl cellulose, polyvinyl alcohol, and thermoplastic polyvinyl butyral resin.

[0040] The plasticizer is selected from at least one of dibutyl phthalate and polyethylene glycol.

[0041] The water is preferably deionized water.

[0042] The stirring after adding the dispersant, plasticizer, binder and water can be vacuum stirring. Specifically, the vacuum stirring is for 15-30 minutes. The purpose of vacuum stirring is to defoam and mix the solution and powder.

[0043] After the slurry is tape-casted, a ceramic green body is obtained; specifically, the slurry is tape-casted on a tape-casting machine to obtain a ceramic green body with a thickness of 0.2-1.0 mm.

[0044] The debinding process is to increase the temperature to 400-500℃ at a heating rate of 0.5-1.5℃ / min and keep it warm for 2-4h.

[0045] The sintering step is to heat the material to 1150-1250°C at a heating rate of 5-8°C / min and keep the temperature for 2-3 hours.

[0046] A mullite porous ceramic material,

[0047] The porous mullite ceramic material is prepared by the tape casting method. The porous mullite ceramic material has a porosity of 60-85%, a through-hole diameter of 40-110 μm, and a strength of 10-30 MPa.

[0048] Example 1:

[0049] A tape casting method for preparing a porous mullite ceramic material in this embodiment is as follows:

[0050] 1. Slurry pretreatment and tape casting

[0051] 100μm SiO2-Al2O3 hollow microspheres and 50μm B2O3, CaCO3, AlF3, and glass powder are mixed in a three-dimensional mixer to obtain a mixed powder. A dispersant, a plasticizer, a binder, and water are added to the mixed powder, and then the mixed powder is vacuum stirred in a stirring container for 30 minutes. The mixed powder comprises, by mass percentage, 40wt% of SiO2-Al2O3 hollow microspheres, 2wt% of B2O3, 3wt% of CaCO3, 3wt% of AlF3, 7wt% of glass powder, 2wt% of dispersant, 1wt% of binder, 2wt% of plasticizer, and the balance is deionized water. The dispersant is ammonium polyacrylate, the binder is sodium carboxymethyl cellulose, and the plasticizer is dibutyl phthalate.

[0052] The purpose of vacuum stirring is to defoam and mix the solution and powder. After vacuum stirring, a slurry is obtained. The slurry is cast on a casting machine to obtain a ceramic green body with a thickness of 0.5 mm. Six layers of ceramic green bodies are stacked in the thickness direction and pressurized at a pressure of 20 MPa for 10 minutes to obtain a sample with a thickness of 2.5-2.8 mm.

[0053] 2. Debinding and sintering

[0054] The above sample was slowly heated at a heating rate of 1.0°C / min in an oxidizing atmosphere furnace, kept at 430°C for 4 hours for debinding, and after debinding was completed, heated to 1200°C at a rate of 6°C / min and kept at this temperature for 2 hours for sintering, and then cooled to room temperature in the furnace to obtain mullite porous ceramic material.

[0055] Example 2:

[0056] A tape casting method for preparing a porous mullite ceramic material in this embodiment is as follows:

[0057] 1. Slurry pretreatment and tape casting

[0058] 200μm SiO2-Al2O3 hollow microspheres and 50um B2O3, CaCO3, AlF3, and glass powder are mixed in a three-dimensional mixer to obtain a mixed powder. A dispersant, a plasticizer, a binder, and water are added to the mixed powder, and then the mixed powder is vacuum stirred in a stirring container for 25 minutes. The mixed powder comprises, by mass percentage, 50wt% SiO2-Al2O3 hollow microspheres, 1wt% B2O3, 1.5wt% CaCO3, 6wt% AlF3, 4wt% glass powder, 0.5wt% dispersant, 3wt% binder, 3wt% plasticizer, and the balance deionized water. The dispersant is ammonium polyacrylate; the binder is a mixture of polyvinyl alcohol and thermoplastic polyvinyl butyral resin, with a mass ratio of 1:2; and the plasticizer is polyethylene glycol.

[0059] The purpose of vacuum stirring is to defoam and mix the solution and powder. After vacuum stirring, a slurry is obtained. The slurry is cast on a casting machine to obtain a ceramic green body with a thickness of 1.0 mm. Six layers of ceramic green bodies are stacked in the thickness direction and pressurized at 20 MPa for 10 minutes to obtain a sample with a thickness of 2.5-2.8 mm.

[0060] 2. Debinding and sintering

[0061] The above sample was slowly heated at a heating rate of 0.5°C / min in an oxidizing atmosphere furnace, kept at 400°C for 2 hours for debinding, and after debinding was completed, the temperature was increased to 1150°C at a rate of 5°C / min and kept at this temperature for 2.5 hours for sintering, and then cooled to room temperature in the furnace to obtain mullite porous ceramic material.

[0062] Example 3:

[0063] A tape casting method for preparing a porous mullite ceramic material in this embodiment is as follows:

[0064] 1. Slurry pretreatment and tape casting

[0065] 150μm SiO2-Al2O3 hollow microspheres and 50um B2O3, CaCO3, AlF3 and glass powder are mixed in a three-dimensional mixer to obtain a mixed powder, and a dispersant, a plasticizer, a binder and water are added to the mixed powder, followed by vacuum stirring in a stirring container for 20 minutes; wherein, by mass percentage, SiO2-Al2O3 hollow microspheres 45wt%, B2O3 3wt%, CaCO3 4wt%, AlF3 4wt%, glass powder 5wt%, dispersant 2.5wt%, binder 2wt%, plasticizer 1wt% and deionized water as the balance; the dispersant is polyethylene glycol octylphenyl ether; the binder is a mixture of water glass and sodium carboxymethyl cellulose, with a mass ratio of 1:1; the plasticizer is dibutyl phthalate.

[0066] The purpose of vacuum stirring is to defoam and mix the solution and powder. After vacuum stirring, a slurry is obtained. The slurry is cast on a casting machine to obtain a ceramic green body with a thickness of 0.8 mm. Six layers of ceramic green bodies are stacked in the thickness direction and pressurized at 20 MPa for 10 minutes to obtain a sample with a thickness of 2.5-2.8 mm.

[0067] 2. Debinding and sintering

[0068] The above sample was slowly heated at a heating rate of 1.5°C / min in an oxidizing atmosphere furnace, kept at 500°C for 3.5 hours for debinding, and after debinding, heated to 1250°C at a rate of 8°C / min and kept at this temperature for 3.0 hours for sintering. It was then cooled to room temperature in the furnace to obtain mullite porous ceramic material.

[0069] With respect to the raw material components, the following comparative examples 1-10 were prepared according to Example 1, as shown in Table 1.

[0070] Table 1 Comparative Examples 1-10 and Example 1

[0071]

[0072]

[0073] With respect to the process parameters, the following comparative examples 11-14 were set according to Example 1, as shown in Table 2.

[0074] Table 2 Comparative Examples 11-14 and Example 1

[0075] Differences from Example 1 Comparative Example 11 The only difference is that when debinding, the heating rate is 2.5℃ / min Comparative Example 12 The only difference is that when debinding, the temperature is raised to 580℃ Comparative Example 13 The only difference is that during sintering, the heating rate is 10℃ / min Comparative Example 14 The only difference is that during sintering, the temperature is raised to 1300℃

[0076] The porous ceramic materials prepared in the above examples and comparative examples were subjected to the following tests to obtain performance test results. Specifically, the test results are shown in Tables 3-4.

[0077] Test method:

[0078] (1) Porosity and average through-hole diameter test: Porosity tester (model: MAY-ENTRIS120), average pore diameter tester (GB / T1967-1996 "Test method for pore diameter of porous ceramics")

[0079] (2) Flexural strength test: three-point bending testing machine.

[0080] (3) Yield test: Statistics are made based on the number of good products produced.

[0081] (4) Appearance test: industrial microscope.

[0082] Table 3 Test results of mullite porous ceramic materials in the embodiment

[0083]

[0084]

[0085] Table 4 Test results of porous ceramic materials of comparative example

[0086]

[0087]

[0088] It can be seen from Table 3-4 that B2O3 and glass powder are mainly used to reduce the sintering temperature of SiO2-Al2O3 hollow microspheres. The main function of CaCO3 is to form partial pores by decomposition in the early stage of sintering to increase the overall porosity. The main function of aluminum fluoride is to promote the formation of mullite crystals. If any of these components is missing or the content does not meet the requirements, it will lead to a poor mullite crystal structure in the ceramic material, which will lead to poor performance of the ceramic material. Specifically, the porosity is low, the pore size is small, and the strength is insufficient.

[0089] Among them, the mullite porous ceramic material prepared in Example 2 is as follows Figure 1 , the through-hole diameters include 61.52μm, 79.44μm, 83.33μm, 149.52μm, and the average through-hole diameter is 88.51μm; the mullite porous ceramic material prepared in Comparative Example 5, such as Figure 2 , the average through-hole diameter is 29.21 μm.

[0090] The test results of Examples 1-3 show that the product prepared by the method of the present invention has a porosity of 60-85%, and preferably a porosity of 70-85%, a through-pore diameter of 40-110 μm, and a strength of 10-30 MPa. It has good performance characteristics and is suitable for uses such as atomizer core preparation. In addition, this method has a high yield rate (yield rate greater than 95%), low cost, simple and easy process operation, and is suitable for large-scale production.

[0091] The specific embodiments of the present invention described above do not limit the scope of protection of the present invention. Any other corresponding changes and modifications made based on the technical concept of the present invention should be included in the scope of protection of the claims of the present invention.

Claims

1. A tape casting method for a mullite porous ceramic material, characterized in that: The following steps are involved: SiO2-Al2O3 hollow microspheres and a sintering aid are mixed, and then a dispersant, a plasticizer, a binder and water are added thereto and stirred evenly to obtain a slurry; the slurry is tape-cast to obtain a ceramic green body; the ceramic green body is subjected to binder removal and sintering to obtain a mullite porous ceramic material; The slurry is composed of the following components by mass fraction: 40-50wt% SiO2-Al2O3 hollow microspheres, 9.5-20% sintering aid, 0.5-2.5wt% dispersant, 1-3wt% binder, 1-3wt% plasticizer, and the balance water; The sintering aids include B2O3, CaCO3, AlF3 and glass powder; the content of AlF3 in the slurry is 3-6wt%.

2. The tape casting method of the mullite porous ceramic material according to claim 1, wherein: In the slurry, the content of B2O3 is 1-3wt%, the content of CaCO3 is 1.5-4wt%, and the content of glass powder is 4-7wt%.

3. The tape casting method of the mullite porous ceramic material according to claim 1, wherein: The SiO2-Al2O3 hollow microspheres have a diameter of 100-200 μm and an impurity content of less than 1%.

4. The tape casting method of the mullite porous ceramic material according to claim 1, wherein: The dispersant is selected from at least one of ammonium polyacrylate and polyethylene glycol octylphenyl ether.

5. The tape casting method of the mullite porous ceramic material according to claim 1, wherein: The binder is selected from a mixture of one or more of water glass, sodium carboxymethyl cellulose, polyvinyl alcohol, and thermoplastic polyvinyl butyral resin.

6. The tape casting method of the mullite porous ceramic material according to claim 1, wherein: The plasticizer is selected from at least one of dibutyl phthalate and polyethylene glycol.

7. The tape casting method of the mullite porous ceramic material according to claim 1, wherein: The debinding process comprises heating the material to 400-500° C. at a heating rate of 0.5-1.5° C. / min and keeping the temperature for 2-4 hours.

8. The tape casting method of the mullite porous ceramic material according to claim 1, wherein: The sintering step is to heat the temperature to 1150-1250° C. at a heating rate of 5-8° C. / min and keep the temperature for 2-3 hours.

9. A mullite porous ceramic material prepared by the tape casting method of the mullite porous ceramic material according to any one of claims 1 to 8, characterized in that: The mullite porous ceramic material has a porosity of 60-85%, a through-hole diameter of 40-110 μm, and a strength of 10-30 MPa.

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