Method for preparing foamed ceramic by foam impregnation process

Abstract

The invention provides a method for preparing foamed ceramic by a foam impregnation process. The preparation method comprises the following steps: uniformly coating a foam matrix with raw material micro powder, and then carrying out slurry hanging and subsequent drying and sintering processes. According to the method, alkali liquor corrosion or complex surface treatment does not need to be carried out on the sponge base body, the mechanical property of the foam base body can be kept, the shape maintaining property after slurry hanging is good, and deformation is not likely to happen. The foam matrix is coated with the raw material micro powder, so that the surface roughness of the foam matrix is increased, and the slurry hanging effect can be remarkably improved. And moreover, the application range to ceramic slurry is wide, and the slurry hanging effect can be improved without adding excessive organic matters into the slurry. In the dynamic process, the foam matrix is subjected to powder coating, and the ceramic micro powder is uniformly distributed on the surface of the foam matrix, so that the slurry coating uniformity and the aperture ratio of the foamed ceramic are ensured.

Description

Technical Field

[0001] The invention belongs to the field of ceramic materials, and in particular relates to a method for preparing foam ceramics by a foam impregnation process. Background Art

[0002] Foam ceramic is a kind of porous material. It is a porous ceramic material with a three-dimensional network structure and high porosity. Due to the special structure of foam ceramic, it has the characteristics of low density, high porosity, large specific surface area, thermal shock resistance, chemical corrosion resistance, strong self-disturbance to fluids and good filtration and adsorption. Therefore, foam ceramic is widely used in molten metal, gas and liquid filtration, chemical catalytic carrier, sound absorption and vibration reduction, biomaterials, and sensors.

[0003] Since the foam matrix has poor hydrophilicity, how to improve the slurry hanging effect of the foam matrix becomes the key to preparing foam ceramics. The existing technology usually improves the slurry hanging effect of the foam matrix through alkaline washing and hydrophilic treatment; for example, in patent CN109231995A, sodium hydroxide solution is used to hydrolyze the polyurethane foam to remove the diaphragm and increase the roughness, thereby achieving a better slurry hanging effect; patent CN105948804A first impregnates the activators separately, and then mixes the activators and then impregnates the method, which can effectively improve the slurry hanging quality of the foam carrier; however, the alkali solution used in the above patents is corrosive to a certain extent, and the activator polyethyleneimine is highly toxic, which will impose many restrictions on actual operations. Summary of the invention

[0004] The object of the present invention is to provide a method for preparing foam ceramics by a foam impregnation process, which method can effectively increase the slurry hanging amount of the foam matrix and further prepare foam ceramics without alkali solution corrosion or complicated surface treatment of the sponge matrix.

[0005] The present invention adopts the following technical solutions to achieve the above-mentioned purpose: A method for preparing foam ceramics by a foam impregnation process, specifically comprising the following steps: 1) Dissolve the binder in a solvent to prepare a solution with adhesive properties; 2) Immerse the foam substrate completely in the above solution, remove it and remove the excess solution; 3) Place the impregnated foam matrix and ceramic powder together in a closed container, and tumble or roll the container to drive the foam matrix to roll and make the ceramic powder adhere to the foam matrix, forming a foam matrix covered with ceramic powder, making the surface of the foam matrix rough; 4) Prepare ceramic slurry, carry out slurry treatment on the foam substrate coated with ceramic powder, and then remove excess slurry to obtain a foam ceramic body; 5) The foam ceramic body is dried and sintered at high temperature to obtain a foam ceramic product.

[0006] The binder described in step 1 is water-soluble or alcohol-soluble. The water-soluble binder is a polyvinyl alcohol solution or a cellulose solution, and the alcohol-soluble binder is polyvinyl butyral.

[0007] The mass fraction of the polyvinyl alcohol solution is 1-5%.

[0008] The cellulose solution is selected from a carboxymethyl cellulose solution with a mass fraction of 1 to 3% or a polyvinyl butyral solution with a mass fraction of 1 to 8%.

[0009] In step 2, the foam matrix is ​​immersed for 2 to 5 minutes, and the excess solution flows out by itself or is removed by squeezing.

[0010] In step 3, the impregnated foam matrix and ceramic powder are placed in a V-type mixer. In the process, the mixer is turned over for coating; or, the impregnated foam matrix and ceramic powder are placed in a ball mill and rolled on a drum mill to complete the coating; the particle size of the coated ceramic powder is adjusted according to the pore size of the foam matrix; the quality of the coated powder is related to the powder density.

[0011] The particle size of the ceramic powder is 1 to 30 μm.

[0012] In step 4, the main raw materials of the ceramic slurry should be consistent with the composition of the ceramic powder in step 3 to prevent the coated powder from becoming an impurity phase; in this step, the excess slurry can be removed by blowing or centrifugation.

[0013] The preparation method of foam ceramics of the present invention does not require surface corrosion of the foam matrix, can maintain the resilience and mechanical properties of the foam matrix, has good shape retention after slurry coating, and is not easy to deform; the foam matrix is ​​coated with raw material micropowder to increase the surface roughness, which can significantly improve the slurry coating effect; the adaptability to ceramic slurry is large, and there is no need to add too much organic matter to the slurry to improve the slurry coating effect; the foam matrix is ​​coated in a dynamic process, and the ceramic micropowder is evenly distributed on the surface of the foam matrix, which ensures the uniformity of the slurry coating and the open porosity of the foam ceramics. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1 This is a picture of the foam matrix of Example 2.

[0015] Figure 2 This is a picture of the foam matrix coated with zirconium oxide powder in Example 2. DETAILED DESCRIPTION

[0016] For a better understanding of the present invention, the present invention is further described below with reference to examples. However, the protection scope of the present invention is not limited to the description scope of the embodiments. Embodiment 1:

[0017] This embodiment is a preparation process of silicon carbide foam ceramics, which is specifically as follows: 1. Dissolve the binder PVA (polyvinyl alcohol) in water to prepare a 5% PVA solution; 2. Completely immerse the 30PPi foam matrix into the above PVA solution, soak for 3 minutes, then take it out and squeeze out the excess solution; 3. Place the impregnated foam matrix and silicon carbide powder (3μm) in a ball mill jar and roll them on a drum ball mill at a drum speed of 120rpm for 3 to 10 minutes. Take out the foam matrix coated with powder and dry it at 80 to 120℃ for later use. The mass of the coated silicon carbide powder is 4 to 5 times that of the foam matrix. 4. Prepare SiC ceramic slurry: mix SiC powder (5μm), magnesium-stabilized zirconium oxide powder (1μm), water and dispersant (tetramethylammonium hydroxide) in a ball mill for 2 to 4 hours at a speed of 200 to 300 rpm. SiC powder accounts for 95% to 98% of the total mass of the powder, and the solid content of the slurry volume is 45 to 50%. The foam substrate prepared in step 3 is immersed in the slurry for 30 to 60 seconds, and the excess slurry is removed by centrifugation to obtain a foam ceramic body; 5. The foam ceramic body is dried at 80-120° C. for 2-6 hours. After drying, it is sintered at 1800-1900° C. for 2-4 hours under Ar gas protection to obtain a SiC foam ceramic product.

[0018] In this embodiment, the foam substrate is coated with 3 μm SiC powder to achieve uniform slurry coating on the foam ceramic, and the slurry coating amount can reach 20 times the mass of the foam substrate. The effect of powder coating can be seen in the attached drawings of the specification. Embodiment 2:

[0019] This embodiment is a preparation process of zirconium oxide foam ceramics, which is specifically as follows: 1. Dissolve the binder PVB (polyvinyl butyral) in anhydrous ethanol to prepare a 3% PVB solution; 2. Completely immerse the 40PPi foam matrix in the above PVB solution, soak for 3 minutes, then take it out and squeeze out the excess solution; 3. Place the impregnated foam matrix and magnesium-stabilized zirconium oxide powder (1 μm) in a V-type mixer, rotate at 60 rpm for 5 min, take out the foam matrix coated with powder, dry it at 60-110°C and set it aside; the mass of the coated zirconium oxide powder is 10-12 times that of the foam matrix; 4. Prepare zirconium oxide ceramic slurry: mix magnesium stabilized zirconium oxide powder (1 μm), water and dispersant (ammonium polyacrylate) in a ball mill for 1 to 2 hours at a ball mill speed of 200 to 300 rpm. The slurry volume solid content is 40 to 45%; The foam substrate prepared in step 3 is immersed in the slurry for 30 to 60 seconds, and the excess slurry is blown out with a strong blower to obtain a foam ceramic body.

[0020] 5. The foam ceramic body is dried at 80-120° C. for 2-6 hours. After drying, it is sintered at 1600-1700° C. for 2-4 hours to obtain a magnesium-stabilized zirconia foam ceramic product.

[0021] In this embodiment, the foam substrate is coated with 1 μm zirconium oxide powder to achieve uniform slurry coating on the foam ceramic, and the slurry coating amount can reach 35 times the mass of the foam substrate.

Claims

1. A method for preparing foam ceramics by foam impregnation process, characterized in that: The specific steps include: 1) Dissolve the binder in a solvent to prepare a solution with adhesive properties; 2) Immerse the foam substrate completely in the above solution, remove it and remove the excess solution; 3) Place the impregnated foam matrix and ceramic powder together in a closed container, and tumble or roll the container to drive the foam matrix to roll and make the ceramic powder adhere to the foam matrix, forming a foam matrix covered with ceramic powder, making the surface of the foam matrix rough; 4) Prepare ceramic slurry, carry out slurry treatment on the foam substrate coated with ceramic powder, and then remove excess slurry to obtain a foam ceramic body; 5) The foam ceramic body is dried and sintered at high temperature to obtain a foam ceramic product.

2. The method for preparing foam ceramics by foam impregnation process according to claim 1, characterized in that: The binder described in step 1 is water-soluble or alcohol-soluble. The water-soluble binder is a polyvinyl alcohol solution or a cellulose solution, and the alcohol-soluble binder is polyvinyl butyral.

3. The method for preparing foam ceramics by foam impregnation process according to claim 2, characterized in that: The mass fraction of the polyvinyl alcohol solution is 1-5%.

4. The method for preparing foam ceramics by foam impregnation process according to claim 2, characterized in that: The cellulose solution is selected from a carboxymethyl cellulose solution with a mass fraction of 1 to 3% or a polyvinyl butyral solution with a mass fraction of 1 to 8%.

5. The method for preparing foam ceramics by foam impregnation process according to claim 1, characterized in that: In step 2, the foam matrix is ​​immersed for 2 to 5 minutes, and the excess solution flows out by itself or is removed by squeezing.

6. The method for preparing foam ceramics by foam impregnation process according to claim 1, characterized in that: In step 3, the impregnated foam matrix and ceramic powder are placed in a V-type mixer, and the mixer is turned over for coating; or, the impregnated foam matrix and ceramic powder are placed in a ball mill, and rolled on a drum mill to complete the coating; the particle size of the coated ceramic powder is adjusted according to the pore size of the foam matrix; the quality of the coated powder is related to the powder density.

7. The method for preparing foam ceramics by foam impregnation process according to claim 6, characterized in that: The particle size of the ceramic powder is 1 to 30 μm.

8. The method for preparing foam ceramics by foam impregnation process according to claim 1, characterized in that: In step 4, the main raw materials of the ceramic slurry should be consistent with the composition of the ceramic powder in step 3 to prevent the coated powder from becoming an impurity phase; in this step, the excess slurry can be removed by blowing or centrifugation.

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