Magnesium oxide stabilized zirconia foam ceramic filter and preparation method thereof

Abstract

The application relates to the technical field of zirconia foam ceramics, in particular to a magnesium oxide stabilized zirconia foam ceramic filter screen and a preparation method thereof; the magnesium oxide stabilized zirconia foam ceramic prepared by adopting a magnesium oxide stabilized zirconia ceramic slurry has the advantages of low shrinkage, low skeleton surface roughness, high strength, uniform microstructure, strong high-temperature deformation resistance, fast slurry coating speed of the foam ceramic green body, difficulty in slurry dropping and saved production time. The volume density of the magnesium oxide stabilized foam ceramic filter screen prepared by the magnesium oxide stabilized foam ceramic filter screen preparation method can reach 0.75-0.9 g / cm 3 , the porosity reaches 80% and above, the bending strength reaches 4.95 MPa and above, the sintering shrinkage is between 7% and 8%, and the requirements of the market for high-standard zirconia foam ceramic filter screens are met.

Description

TECHNICAL FIELD

[0001] The application relates to the technical field of zirconia foam ceramics, in particular to a magnesium oxide stabilized zirconia foam ceramic filter screen and a preparation method thereof. BACKGROUND

[0002] In the production of castings, the foam ceramic filter screen liquid metal filtration technology is adopted, three filtration and purification mechanisms of mechanical interception, flow regulation of dross and deep adsorption can effectively reduce or eliminate non-metallic inclusions in the liquid metal, purify the liquid alloy, thereby improving the yield of the alloy and improving the internal quality, working performance and machining performance of the castings.

[0003] For alloys with low smelting temperature, such as copper, aluminum and magnesium, since the high-temperature performance requirement of the filter material is not high, the foam ceramic filter screen made of alumina and silicon carbide can meet the requirement. However, for the molten steel or high-temperature alloy melt with a pouring temperature of 1600 DEG C or above, the foam ceramic material for filtration and purification must have higher high-temperature strength, softening temperature and thermal shock resistance. The high-temperature performance of the foregoing several ceramic foam filter screen materials cannot meet the requirement, but a large number of high-end cast steel and high-temperature alloy castings with high added value need to adopt the foam ceramic filtration technology to improve the product quality. In order to achieve this purpose, a large amount of research has been carried out at home and abroad in the past twenty years.

[0004] There are two difficulties in the preparation technology of zirconia-based foam ceramics: first, during the sintering process of zirconia products, due to the martensite phase transformation and the particularity of the foam ceramic structure, the green body method is to adopt ceramic slurry to be coated and formed on the three-dimensional foam plastic, the powder bulk density is low compared with the zirconia ceramic formed by pressing, the sintering mass transfer process and solid solution reaction have other characteristics, the sintering shrinkage is larger, so the strength of part of the stabilized zirconia foam ceramic product is lower, and it is easy to crack. SUMMARY

[0005] The technical problem to be solved by the application is to provide a magnesium oxide stabilized zirconia foam ceramic filter screen and a preparation method thereof, which effectively reduces the cracking phenomenon of the foam ceramic filter screen product by reducing the sintering shrinkage.

[0006] To solve the above technical problems, the technical scheme adopted by the application is:

[0007] The magnesium oxide stabilized zirconia foam ceramic filter screen comprises the following ceramic raw materials: 700-800 parts by mass of magnesium oxide stabilized fused zirconia with an average particle size of 1.5 microns, 600-800 parts by mass of magnesium oxide stabilized fused zirconia with an average particle size of 15 microns, 600 parts by mass of magnesium oxide fused zirconia with an average particle size of 20 microns, solvent water, a high molecular binder, a dispersing agent and xanthan gum.

[0008] Further, in the magnesium oxide stabilized zirconia foam ceramic filter screen, the high polymer binder is polyvinyl alcohol.

[0009] Further, in the magnesium oxide stabilized zirconia foam ceramic filter screen, the dispersant is a styrene maleic anhydride copolymer.

[0010] Further, in the magnesium oxide stabilized zirconia foam ceramic filter screen, the amount of xanthan gum is 0.18-0.5wt%.

[0011] Further, in the magnesium oxide stabilized zirconia foam ceramic filter screen, the amount of dispersant is 0.045-0.1wt%.

[0012] The application also protects the preparation method of the magnesium oxide stabilized zirconia foam ceramic filter screen, comprising the following steps:

[0013] S1: Dissolve the high polymer binder in water to form a solution, then add 700-800 parts by mass of magnesium oxide stabilized fused zirconia with an average particle size of 1.5 μm, 600-800 parts by mass of magnesium oxide stabilized fused zirconia with an average particle size of 15 μm, and 600 parts by mass of magnesium oxide stabilized fused zirconia with an average particle size of 20 μm, and simultaneously add xanthan gum and dispersant, and then blend by ball milling to obtain ceramic slurry;

[0014] S2: Soak the polyurethane foam sponge in a 10-20% mass concentration sodium hydroxide aqueous solution at a temperature of 40-60℃ for 2-4 hours, take it out, repeatedly rinse with clean water, dry, dip in the above ceramic slurry, then remove the excess ceramic slurry in the polyurethane foam by the first-time extrusion method of passing through a pulp squeezing machine, then naturally dry the polyurethane foam green body; the second time, also use the extrusion method to remove the excess ceramic slurry in the polyurethane foam by passing through a pulp squeezing machine; obtain the polyurethane foam green body with ceramic slurry fully attached to the ribs and bones; then dry the polyurethane foam green body; finally, add water to the original ceramic slurry and spray the green body for the third time; then sinter the dried polyurethane foam in an air atmosphere at 1550-1750℃ for 25-30 hours, and cool to obtain the finished product of the magnesium oxide stabilized zirconia foam ceramic filter screen.

[0015] Further, in the preparation method of the magnesium oxide stabilized zirconia foam ceramic filter screen, the method for drying the polyurethane foam green body is natural drying at room temperature.

[0016] Further, in the preparation method of the magnesium oxide stabilized zirconia foam ceramic filter screen, in S1, the high polymer binder is dissolved in water, and the mass ratio of the high polymer binder to water is 1:9.

[0017] Furthermore, in the preparation method of the above-mentioned magnesium oxide stabilized zirconia foam ceramic filter screen, water is added to the original ceramic slurry and then the green body is sizing for the third time by spraying, wherein the amount of water added is 3-5wt%.

[0018] Furthermore, in the above-mentioned method for preparing the magnesium oxide stabilized zirconia foam ceramic filter screen, in said S1, the amount of the polymer binder in the ceramic slurry is 13-24 wt%.

[0019] The beneficial effects of the present invention are as follows: compared with the zirconia ceramic slurry partially stabilized by magnesium oxide, the magnesium oxide stabilized zirconia foam ceramic prepared by the magnesium oxide stabilized zirconia ceramic slurry has a lower shrinkage rate, lower skeleton surface roughness, high strength, uniform microstructure, and strong resistance to high-temperature deformation. In addition, the foam ceramic green body has a fast sizing speed and is not easy to fall off, thus saving production time. The magnesium oxide stabilized foam ceramic filter prepared by the preparation method of the magnesium oxide stabilized foam ceramic filter can have a volume density of 0.75 to 0.9 g / cm 3 At the same time, the porosity reaches 80% and above, the flexural strength reaches 4.95MPa and above, and the sintering shrinkage rate is between 7% and 8%, which meets the market requirements for high-standard zirconia foam ceramic filters. DETAILED DESCRIPTION

[0020] In order to explain the technical content, achieved objectives and effects of the present invention in detail, the following description is given in conjunction with the implementation methods.

[0021] Example 1

[0022] The preparation method of the magnesium oxide stabilized foam ceramic filter comprises the following steps:

[0023] S1: Dissolve 140g of polymer binder in 200g of pure water, then add 800g of magnesium oxide-stabilized fused zirconia with an average particle size of 1.5μm, 600g of magnesium oxide-stabilized fused zirconia with an average particle size of 15μm, 600g of magnesium oxide-stabilized fused zirconia with an average particle size of 20μm, 4g of dispersant, and 6g of xanthan gum in a ball mill and mix into a slurry.

[0024] S2: Cut the The polyurethane foam with a pore size of 10 PPI is immersed in a 20% by mass sodium hydroxide aqueous solution at 40°C for 2 hours, then removed, repeatedly washed with clean water, and dried in an oven at 80°C for 24 hours. The dried polyurethane foam is dipped in a certain amount of the magnesium oxide-stabilized zirconia slurry, then the excess slurry is squeezed off on a slurry squeezing machine, and the polyurethane foam is naturally dried in air. Thereafter, the polyurethane foam with the dried ceramic layer on the surface is secondarily immersed in the magnesium oxide-stabilized zirconia slurry, then the excess slurry is squeezed off on the slurry squeezing machine, and dried in air. Then, the green body coated twice with the slurry is sprayed three times with a slurry having a specific gravity adjusted to 2.8-2.9 g / cm 3 at 200 g of pure water at a spray gun. Sintering at 1550°C in air for 30 hours gives a magnesium oxide-stabilized zirconia foam ceramic filter.

[0025] Example 2

[0026] A method for preparing a magnesium oxide-stabilized foam ceramic filter includes the following steps:

[0027] S1: 140 g of a polymer binder is dissolved in 200 g of pure water, then 700 g of magnesium oxide-stabilized fused zirconia with an average particle size of 1.5 μm, 700 g of magnesium oxide-stabilized fused zirconia with an average particle size of 15 μm, 600 g of magnesium oxide-stabilized fused zirconia with an average particle size of 20 μm, 3 g of a dispersant, and 7 g of xanthan gum are mixed into a slurry in a ball mill.

[0028] S2: The polyurethane foam with a pore size of 10 PPI is cut into a size of 100 mm x 100 mm x 100 mm. The polyurethane foam with a pore size of 10 PPI is immersed in a 20% by mass sodium hydroxide aqueous solution at 40°C for 2 hours, then removed, repeatedly washed with clean water, and dried in an oven at 80°C for 24 hours. The dried polyurethane foam is dipped in a certain amount of the magnesium oxide-stabilized zirconia slurry, then the excess slurry is squeezed off on a slurry squeezing machine, and the polyurethane foam is naturally dried in air. Thereafter, the polyurethane foam with the dried ceramic layer on the surface is secondarily immersed in the magnesium oxide-stabilized zirconia slurry, then the excess slurry is squeezed off on the slurry squeezing machine, and dried in air. Then, the green body coated twice with the slurry is sprayed three times with a slurry having a specific gravity adjusted to 2.8-2.9 g / cm 3 at 200 g of pure water at a spray gun. Sintering at 1550°C in air for 30 hours gives a magnesium oxide-stabilized zirconia foam ceramic filter.

[0029] Example 3

[0030] A method for preparing a magnesium oxide stabilized zirconia foam ceramic filter screen includes the following steps:

[0031] S1: Dissolve 140 g of a polymer binder in 200 g of pure water, then add 800 g of magnesium oxide stabilized fused zirconia with an average particle size of 1.5 μm, 800 g of magnesium oxide stabilized fused zirconia with an average particle size of 15 μm, 600 g of magnesium oxide stabilized fused zirconia with an average particle size of 20 μm, 5 g of a dispersant, and 8 g of xanthan gum in a ball mill to form a slurry.

[0032] S2: Cut the polyurethane foam with a pore size of 10 PPI into pieces with a size of 20 mm x 20 mm x 20 mm. The polyurethane foam with a pore size of 10 PPI is immersed in a 20% by mass sodium hydroxide aqueous solution at 40°C for 2 hours, then the polyurethane foam is taken out, repeatedly washed with clean water, and then placed in an oven at 80°C for drying for 24 hours. The dried polyurethane foam is immersed in a certain amount of the magnesium oxide stabilized zirconia slurry, then the polyurethane foam is squeezed on a squeezing machine to remove the excess slurry, and then the polyurethane foam is naturally dried in the air. Subsequently, the polyurethane foam with a dried ceramic layer on the surface is immersed in the magnesium oxide stabilized zirconia ethanol slurry for the second time, then the excess slurry is squeezed on the squeezing machine, and then the polyurethane foam is dried in the air. Then the green body after the second dipping is sprayed three times on a spray gun with the slurry with a specific gravity of 2.8-3.0 g / cm 3 after adding 200 g of pure water. The sintering is performed at 1750°C in air for 30 hours to obtain the magnesium oxide stabilized zirconia foam ceramic filter screen.

[0033] Comparative Example 1

[0034] A method for preparing a partially magnesium stabilized zirconia foam ceramic filter screen, which is different from Example 1 in that the ceramic slurry has a composition of 800 g of monoclinic zirconia powder with an average particle size of 1.5 μm, 500 g of magnesium oxide stabilized fused zirconia with an average particle size of 15 μm, 500 g of magnesium oxide stabilized fused zirconia with an average particle size of 20 μm, and 80 g of magnesium oxide powder.

[0035] Comparative Example 2

[0036] A method for preparing a partially magnesium stabilized zirconia foam ceramic filter screen, which is different from Example 1 in that the ceramic slurry has a composition of 800 g of magnesium oxide stabilized fused zirconia with an average particle size of 1.5 μm, 500 g of monoclinic zirconia powder with an average particle size of 15 μm, 500 g of monoclinic zirconia powder with an average particle size of 20 μm, and 80 g of magnesium oxide powder.

[0037] Comparative Example 3

[0038] The preparation method of the magnesium oxide stabilized zirconia foam ceramic filter screen described in Example 1 is different in that the ceramic slurry is replaced by 2000 g of magnesium oxide stabilized fused zirconia with an average particle size of 1.5 μm.

[0039] Comparative Example 4

[0040] The preparation method of the magnesium oxide stabilized zirconia foam ceramic filter screen described in Example 1 is different in that the ceramic slurry is replaced by 2000 g of magnesium oxide stabilized fused zirconia with an average particle size of 15 μm.

[0041] Comparative Example 5

[0042] The preparation method of the magnesium oxide stabilized zirconia foam ceramic filter screen described in Example 1 is different in that the ceramic slurry is replaced by 2000 g of magnesium oxide stabilized fused zirconia with an average particle size of 20 μm.

[0043] The magnesium oxide stabilized fused zirconia involved in the above examples and comparative examples is a finished product provided by Sanxiang New Material Co., Ltd., with a brand name of SZM. The monoclinic zirconia powder involved is a finished product provided by Sanxiang New Material Co., Ltd. In Comparative Example 1 and Comparative Example 2, part of the particle size of the magnesium oxide stabilized fused zirconia is replaced by monoclinic zirconia powder, and a certain amount of magnesium oxide powder is added. These monoclinic zirconia powder and magnesium oxide powder will partially react with the magnesium oxide stabilized fused zirconia, but cannot form magnesium oxide completely stabilized zirconia.

[0044] Experimental Example

[0045] The magnesium oxide stabilized zirconia foam ceramic prepared in Examples 1-3 and Comparative Examples 1 and 2 is detected for physical properties and mechanical properties, and the detection results are shown in Table 1.

[0046] Table 1

[0047] Item Specification Pore density Bulk density g / cm 3 ]] Porosity % Bending strength Mpa Sintering shrinkage Example 1 Φ75*25 10 ppi 0.75～0.85 ≥81 ≥5.3 7.2％ Example 2 Φ75*25 10 ppi 0.8～0.86 ≥80 ≥4.95 8.1％ Example 3 Φ75*25 10 ppi 0.82～0.9 ≥80 ≥5.57 7.5％ Comparative Example 1 Φ75*25 10 ppi 0.70～0.75 ≥80 ≥3.21 15％ Comparative Example 2 Φ75*25 10 ppi 0.65～0.69 ≥80 ≥2.38 13％ Comparative Example 3 Φ75*25 10 ppi 0.66～0.70 ≥80 ≥2.54 11％ Comparative Example 4 Φ75*25 10 ppi 0.73～0.75 ≥80 ≥3.33 14％ Comparative Example 5 Φ75*25 10 ppi 0.72～0.75 ≥80 ≥3.15 15％

[0048] As can be seen from Table 1, the magnesium oxide stabilized foam ceramic filter screen prepared in Examples 1-3 has a bulk density of 0.75-0.9 g / cm 3 , high porosity and high bending strength, uniform pore size distribution, good permeability, sintering shrinkage of 7%-8%, and less cracking of the finished product.

[0049] The above only describes the embodiments of the present application, and does not limit the patent scope of the present application. Any equivalent transformation or direct or indirect application in related technical fields based on the content of the present application is also included in the patent protection scope of the present application.

Claims

1. Magnesia stabilized zirconia foam ceramic filter, characterized in that, The ceramic raw materials include: 700-800 parts by mass of magnesia-stabilized fused zirconia with an average particle size of 1.5 μm, 600-800 parts by mass of magnesia-stabilized fused zirconia with an average particle size of 15 μm, 600 parts by mass of magnesia-stabilized fused zirconia with an average particle size of 20 μm, solvent water, polymer binder, dispersant and xanthan gum.

2. The magnesia-stabilized zirconia foam ceramic filter according to claim 1, characterized in that: The polymer binder is polyvinyl alcohol.

3. The magnesia-stabilized zirconia foam ceramic filter screen according to claim 1, characterized in that: The dispersant is styrene maleic anhydride copolymer.

4. The magnesia-stabilized zirconia foam ceramic filter screen according to claim 1, characterized in that: The amount of xanthan gum used is 0.18-0.5 wt %.

5. The magnesia-stabilized zirconia foam ceramic filter screen according to claim 1, characterized in that: The amount of the dispersant is 0.045-0.1 wt %.

6. The method for preparing the magnesia-stabilized zirconia foam ceramic filter according to any one of claims 1 to 5, characterized in that: The following steps are involved: S1: dissolving a polymer binder in water to form a solution, then adding 700-800 parts by mass of magnesia-stabilized fused zirconia with an average particle size of 1.5 μm, 600-800 parts by mass of magnesia-stabilized fused zirconia with an average particle size of 15 μm, and 600 parts by mass of magnesia-stabilized fused zirconia with an average particle size of 20 μm, xanthan gum, and a dispersant, and mixing by ball milling to obtain a ceramic slurry; S2: Soak the polyurethane foam sponge in a sodium hydroxide aqueous solution with a mass concentration of 10-20% and a temperature of 40-60°C for 2-4 hours, then take it out, rinse it repeatedly with clean water, dry it, and then dip it in the above-mentioned ceramic slurry. Then, pass the polyurethane foam sponge through a slurry squeezer for the first time to remove excess ceramic slurry in the polyurethane foam sponge, and then allow the polyurethane foam green body to dry naturally; the second time, the polyurethane foam sponge that has been completely soaked in the ceramic slurry is passed through a slurry squeezer to remove excess ceramic slurry in the polyurethane foam sponge; obtain a polyurethane foam green body with ceramic slurry fully attached to the ribs; then dry the polyurethane foam green body; finally, add water to the original ceramic slurry and then sizing the green body for the third time in the form of spraying; then, the dried polyurethane foam green body is sintered at 1550-1750°C for 25-30 hours in an air atmosphere, and after cooling, a finished magnesium oxide stabilized zirconia foam ceramic filter is obtained.

7. The method for preparing the magnesia-stabilized zirconia foam ceramic filter screen according to claim 6, characterized in that: The method for drying the polyurethane foam green body is to dry it naturally at room temperature.

8. The method for preparing the magnesia-stabilized zirconia foam ceramic filter screen according to claim 6, characterized in that: In the above-mentioned S1, the polymer binder is dissolved in water, and the mass ratio of the polymer binder to water is 1:

9.

9. The method for preparing the magnesia-stabilized zirconia foam ceramic filter screen according to claim 6, characterized in that: Finally, water is added to the original ceramic slurry and then the polyurethane foam green body is sizing for the third time in the form of spraying, wherein the amount of water added is 3-5wt%.

10. The method for preparing the magnesia-stabilized zirconia foam ceramic filter screen according to claim 6, characterized in that: In the above S1, the amount of the polymer binder in the ceramic slurry is 13-24 wt%.