Preparation method of foamed ceramic

Abstract

The invention provides a preparation method of foamed ceramic. The preparation method comprises the following steps: coating a foam matrix with raw material powder after slurry coating, rapidly reducing the flowability of slurry, pressing the coated raw material powder into the slurry under a certain pressure condition to form a compact and smooth surface so as to obtain a foam ceramic green body with uniform slurry distribution and high solid phase content, and further preparing the foam ceramic. According to the method, on one hand, the problem of non-uniform distribution caused by migration of slurry under the influence of gravity after slurry hanging of the foamed ceramic is solved, on the other hand, the solid phase content and the blank strength of the foamed ceramic can be improved, shrinkage in the drying and sintering process is reduced, and the finished product rate of foamed ceramic preparation can be improved.

Description

Technical Field

[0001] The invention belongs to the field of ceramic materials, and in particular relates to a method for preparing foam ceramics. 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] Slurry coating is the key to the preparation process of foam ceramics. Since the foam matrix has poor hydrophilicity, the slurry will still migrate under the action of gravity after the foam matrix is ​​coated with slurry, resulting in uneven slurry distribution or a certain gradient. For ceramic slurries with higher material density, such as zirconium oxide (density about 5.8g / cm 3 ), this migration phenomenon will be more obvious, and the uneven distribution of slurry will also lead to the low quality of the final prepared foam ceramic. Although spraying slurry in the later stage can play a certain effect and make the slurry on the surface relatively uniform, the problems inside the foam matrix cannot be eliminated. Summary of the invention

[0004] The purpose of the present invention is to provide a method for preparing foam ceramics, in which a foam substrate is coated with raw material powder after being coated with slurry to quickly reduce the fluidity of the slurry; then the coated raw material powder is pressed into the slurry under certain pressure conditions to form a dense and smooth surface, thereby obtaining a foam ceramic body with uniform slurry distribution, and further preparing foam ceramics.

[0005] The present invention adopts the following technical solutions to achieve the above-mentioned purpose: A method for preparing foam ceramics, characterized in that the preparation method comprises the following steps: (1) Prepare ceramic slurry, fully immerse the foam matrix in the slurry, take it out, and squeeze out the excess slurry; (2) placing the foam substrate after slurry coating and the ceramic powder in a closed container, and causing the container to tumble or roll, thereby driving the foam substrate to roll and causing the ceramic powder to adhere to the foam substrate after slurry coating, thereby forming a foam substrate coated with the powder; (3) placing the powder-coated foam substrate in a pressure vessel, and pressing the coated powder into an undried slurry under certain pressure conditions to form a foam ceramic body with a dense and smooth surface; (4) The foam ceramic body of step 3 is dried and sintered at high temperature to obtain a foam ceramic product.

[0006] In the above preparation process, the ceramic slurry in step 1 is alumina, zirconia or silicon carbide, the immersion time is 60 to 300 seconds, and the foam matrix can be polyurethane or polyether foam.

[0007] The composition and particle size of the ceramic powder in step 2 should be the same as the raw materials in the ceramic slurry; The foam matrix and powder after slurry coating can be placed in a V-shaped mixer, and the mixer is turned over for coating; or the foam matrix and powder after slurry coating can be placed in a ball mill, and rolled on a drum mill to complete the coating; The surface viscosity of the slurry coated with powder increases rapidly and it has no fluidity and is fixed in situ on the foam matrix. At the same time, the coated powder forms a rough surface.

[0008] Therefore, it is necessary to treat the foam matrix after the powder is coated and before drying. In step 3, the powder can be pressed into the slurry by compressed air, and the pressure is preferably 0.3-4.0Mpa, and the pressure holding time is 5-30min; In step 4, the drying and high-temperature sintering system needs to be determined according to the foam ceramic material, and the details can be seen in the embodiment.

[0009] The present invention coats the foam base with raw material powder after slurry coating to quickly reduce the slurry fluidity; then presses the coated raw material powder into the slurry under a certain pressure condition to form a dense and smooth surface, thereby obtaining a foam ceramic body with uniform slurry distribution, thereby solving the problem of uniformity of foam ceramic slurry coating. This can be achieved by conventional drum ball mills, mixers and air compressors.

[0010] In addition, after the powder is pressed into the slurry, the overall solid content of the slurry increases, which improves the body strength of the foam ceramic, reduces the shrinkage during the drying and sintering process, and can improve the yield of foam ceramic preparation. BRIEF DESCRIPTION OF THE DRAWINGS

[0011] Figure 1 This is a picture of SiC foam ceramic prepared in Example 1 of the present invention.

[0012] Figure 2 This is a picture of the ZrO2 foam ceramic prepared in Example 2 of the present invention. DETAILED DESCRIPTION

[0013] 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. Example 1

[0014] This embodiment is a preparation process of silicon carbide foam ceramics, which is specifically as follows: 1. Prepare SiC slurry by ball milling SiC powder (5 μm), magnesium-stabilized zirconium oxide powder (1 μm), water and dispersant (tetramethylammonium hydroxide) in a ball mill; the ball milling time is 2 to 4 hours, and the ball milling speed is 200 to 300 rpm; SiC powder accounts for 95% to 98% of the total mass of the powder, and the volume solid content of the slurry is 45 to 50%; Add the binder styrene acrylic emulsion to the SiC slurry and stir evenly. Vacuum and remove bubbles for later use. The amount of styrene acrylic emulsion added is 3-5% of the mass of SiC. Soak the 40PPi foam matrix in the slurry with the binder for 120 seconds, then take it out and squeeze out the excess slurry. At this time, the amount of slurry is about 15 times that of the foam matrix.

[0015] 2. Place the foam matrix after slurry coating and silicon carbide powder (5μm) in a ball mill, roll on a drum ball mill, the drum speed is 120rpm, the time is 3 to 10min, take out the foam matrix coated with powder; after coating with silicon carbide powder, the weight gain is 5 to 8 times that of the foam matrix.

[0016] 3. Place the powder-coated foam substrate in a pressure vessel, fill it with compressed air, maintain the pressure at 2.0 MPa for 10 minutes, then take it out to obtain a foam ceramic body; 4. 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.

[0017] The silicon carbide foam ceramic prepared in this embodiment is shown in the accompanying drawings of the specification, the slurry is evenly distributed, the thickness of the pores is consistent, and the opening rate is high. Example 2

[0018] 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.

[0019] This embodiment is a preparation process of silicon carbide foam ceramics, which is specifically as follows: 1. Magnesium-stabilized zirconium oxide powder (1 μm), water and dispersant (ammonium polyacrylate) are ball-milled in a ball mill to prepare ZrO2 slurry; the ball milling time is 2 to 4 hours, the ball milling speed is 200 to 300 rpm; the slurry volume solid content is 45 to 50%; the amount of dispersant added is 1 to 2% of the powder mass; Add 10% PVA solution of binder to ZrO2 slurry and stir evenly, remove bubbles in vacuum and set aside. The amount of PVA solution added is 4-6% of the mass of ZrO2. Soak 30PPi foam matrix in the slurry with binder for 120s, then take it out and squeeze out the excess slurry. At this time, the amount of slurry is about 25 times that of the foam matrix.

[0020] 2. Place the slurry-coated foam matrix and magnesium-stabilized zirconium oxide powder (1 μm) in a ball mill, and roll them on a drum ball mill at a drum speed of 120 rpm for 3 to 10 minutes. Take out the powder-coated foam matrix, and the weight gain after coating the zirconium oxide powder is 7 to 10 times that of the foam matrix.

[0021] 3. Place the powder-coated foam substrate in a pressure vessel, fill it with compressed air, maintain the pressure at 3.0 MPa for 10 minutes, then take it out to obtain a foam ceramic body; 4. 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 in an air atmosphere to obtain a magnesium-stabilized zirconia foam ceramic product.

Claims

1. A method for preparing foam ceramics, characterized in that: The preparation method comprises the following steps: (1) Prepare ceramic slurry, fully immerse the foam matrix in the slurry, take it out, and squeeze out the excess slurry; (2) placing the foam substrate after slurry coating and the ceramic powder together in a closed container, and causing the container to tumble or roll, thereby driving the foam substrate to roll and causing the ceramic powder to adhere to the foam substrate after slurry coating, thereby forming a foam substrate coated with the powder; (3) placing the powder-coated foam substrate in a pressure vessel, and pressing the coated powder into an undried slurry under certain pressure conditions to form a foam ceramic body with a dense and smooth surface; (4) The foam ceramic body of step 3 is dried and sintered at high temperature to obtain a foam ceramic product.

2. The method for preparing foam ceramics according to claim 1, characterized in that: The ceramic slurry in step (1) is alumina, zirconia or silicon carbide slurry, the immersion time is 60 to 300 seconds, and the foam matrix is ​​polyurethane or polyether foam.

3. The method for preparing foam ceramics according to claim 1, characterized in that: The composition of the ceramic powder in step (2) is the same as the raw material in the ceramic slurry.

4. The method for preparing foam ceramics according to claim 1, characterized in that: The particle size of the ceramic powder in step (2) is 1 to 30 μm.

5. The method for preparing foam ceramics according to claim 1, characterized in that: In step (3), compressed air is introduced into the pressure vessel for pressurization.

6. The method for preparing foam ceramics according to claim 1, characterized in that: The pressure condition in step (3) is 0.3-4.0 MPa and the pressure holding time is 5-30 min.

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