Preparation method of gel-casting alumina fiber and yttrium oxide co-reinforced zirconia ceramic

Abstract

The invention discloses a preparation method of gel casting alumina fiber and yttrium oxide co-reinforced zirconia ceramic, which comprises the following steps: firstly, modifying zirconia powder, then doping yttrium oxide and alumina fiber in the zirconia powder, and finally, carrying out green gel casting by adopting an Isobam gelling agent, thereby obtaining the alumina fiber and yttrium oxide co-reinforced zirconia ceramic. And sintering to obtain the alumina fiber and yttrium oxide co-reinforced zirconia ceramic. The modified zirconium oxide powder is prepared, yttrium oxide is doped in the modified zirconium oxide powder, the sintering activity of zirconium oxide is improved, the mechanical performance of the composite material is improved through doped aluminum oxide fibers, and an adopted Isobam gel system is environmentally friendly, high in production efficiency, good in blank quality and lower in cost.

Description

Technical Field

[0001] The invention relates to the technical field of inorganic ceramic material preparation, and in particular to a method for preparing a gel injection molded alumina fiber and yttria co-reinforced zirconia ceramics. Background Art

[0002] Zirconia (ZrO2) ceramics have been widely used in aerospace, automotive, electronics and medical equipment due to their excellent high temperature performance, wear resistance, corrosion resistance and thermal stability. However, the brittleness of zirconia ceramics limits its application in certain high stress environments. To solve this problem, researchers have proposed to improve the mechanical properties of zirconia ceramics, especially toughness and thermal shock resistance, by adding reinforcing phase materials. Typical reinforcing materials include Al2O3 fiber, yttrium oxide (Y2O3), etc.

[0003] As a common reinforcing material, Al2O3 fiber plays a significant role in strengthening zirconia ceramics due to its good high temperature strength and heat resistance. Al2O3 fiber can effectively disperse stress, improve the crack resistance of zirconia ceramics, and reduce the thermal expansion coefficient of ceramics, thereby improving its thermal shock stability.

[0004] Yttria (Y2O3) is another widely used reinforcing material for zirconia ceramics. It can effectively improve the stability of zirconia, especially at high temperatures. Yttria can not only prevent zirconia from undergoing adverse phase changes at high temperatures, but also improve its corrosion resistance and increase its high temperature resistance. Therefore, zirconia-yttria ceramic composites show strong performance advantages under high temperature and high pressure environments.

[0005] The existing methods for preparing zirconia composite ceramics mainly use hot pressing, injection molding and traditional sintering processes. Although these methods can produce composite materials with good mechanical properties, their complex processes, high equipment requirements, high costs, and uneven distribution of fibers or powders during the molding process limit their application in large-scale production.

[0006] This patent proposes a new preparation method, which uses spray granulation to prepare Al2O3 fiber, yttrium oxide and zirconium oxide powder, and combines it with a new gel injection molding technology, which can effectively improve the comprehensive performance of the material. Through vacuum sintering technology, high-density and high-strength zirconium oxide ceramics are finally obtained, providing a new technical path for improving the performance of ceramic materials. Summary of the invention

[0007] The purpose of the present invention is to provide a method for preparing alumina fiber and yttria co-reinforced zirconia ceramics by gel injection molding. The present invention adopts a new modification technology to obtain modified zirconia powder with better surface activity. The green gel injection molding technology adopted has a simple process, can obtain a slurry with good dispersibility, can mold zirconia ceramics of complex shapes, has a small processing allowance, reduces subsequent processing, and has lower costs. The mechanical properties of the composite material are increased by doping with alumina fibers, so that the toughness of the ceramic is improved, and the high temperature resistance of the composite material is improved, so that precision devices under high temperature conditions can be made.

[0008] The technical solution adopted by the present invention is as follows:

[0009] A method for preparing a gel injection molded alumina fiber and yttria co-reinforced zirconia ceramics comprises the following steps:

[0010] Step 1, modification of zirconium oxide powder: the modifier, anhydrous ethanol and dispersant are stirred and mixed evenly in a certain mass ratio, and then added into the zirconium oxide powder and mixed, and then ball milled, the material is dried after discharge, and then ground and sieved to obtain modified zirconium oxide powder;

[0011] Preferably, the amount of zirconium oxide added is 40wt%-50wt% of the slurry mass, the modifier is concentrated sulfuric acid or concentrated nitric acid with a concentration of 68%, and the amount added is 2-5% of the powder mass; the dispersant is one or more of ammonium citrate, acrylic acid, and sodium polyacrylate, and the amount added is 0.5-2% of the powder mass; the ball milling time is 16-24h; dried at 60-80°C and passed through a 120-mesh sieve.

[0012] Step 2, slurry preparation: Isobam gelling agent is mixed with ultrapure water to prepare Isobam aqueous solution, and the pH is adjusted to 9-11 by lactic acid and tetramethylammonium hydroxide to obtain a premixed solution; then modified zirconium oxide powder, alumina fiber and yttrium oxide are added to the premixed solution, and mixed by ball milling to obtain a mixed slurry;

[0013] Preferably, the Isobam gelling agent is one or more of Isobam104, Isobam110, and Isobam304, and the added amount is 0.5-1.5wt% of ultrapure water; the modified zirconia powder accounts for 75-90% of the total mass of the powder, the alumina fiber accounts for 5-10% of the total mass of the powder, the yttrium oxide accounts for 5-15% of the total mass of the powder, and the powder accounts for 65-75% of the total mass of the slurry.

[0014] Step 3: Curing and forming: inject the mixed slurry into the mold after vacuum degassing, and cure it in a water bath;

[0015] Preferably, the vacuum degassing pressure is -0.7 to -1 MPa, the vacuum degassing time is 10-30 min, the water bath heating temperature is 50-70° C., and the curing time is 30-50 min.

[0016] Step 4: Sintering: After demoulding, the ceramic body is dried to obtain a ceramic body, and finally the ceramic body is sintered in a sintering furnace to obtain alumina fiber and yttria co-reinforced zirconia ceramics.

[0017] Preferably, the specific drying process is: drying in a constant temperature and humidity chamber at a humidity of 70-85% and a temperature of 35-50° C. for 15-20 hours.

[0018] Preferably, the specific sintering process is: heating to 800°C at a rate of 1-5°C / min, keeping warm for 1-2h, heating to 1750-1850°C at a rate of 1-3°C / min, and keeping warm for 2-5h.

[0019] Compared with the prior art, the present invention has the following beneficial effects:

[0020] (1) The present invention adopts a new modification technology and uses concentrated sulfuric acid to treat the powder to obtain modified zirconia powder, so that the particle size of the zirconia powder is further reduced and the surface activity is increased. This solves the problem of easy shrinkage of zirconia during sintering, and the densification temperature is significantly reduced during ceramic sintering, so that dense ceramics can be obtained.

[0021] (2) The doped alumina fibers increase the mechanical properties of the composite material, and the high temperature resistance of the composite material is improved, so that precision devices can be made under high temperature conditions.

[0022] (3) The green gel injection molding technology adopted in the present invention has a simple process and can obtain a slurry with good dispersibility. It can form zirconia ceramics with complex shapes, has a small processing allowance, reduces subsequent processing, and has lower costs. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 The process route diagram used in Examples 1-4. DETAILED DESCRIPTION

[0024] The present invention is further described in detail below with reference to the accompanying drawings and specific embodiments.

[0025] The raw materials and reagents used in the following examples are all commercially available products.

[0026] Example 1

[0027] Step 1: Modification of zirconium oxide powder: 8 mL of concentrated sulfuric acid (concentration of 68%) was stirred and mixed with 600 mL of anhydrous ethanol and 4 g of dispersant ammonium citrate, and then 400 g of zirconium oxide powder was added and mixed, and then ball milled for 16 h. After the material was discharged, it was dried at 60 ° C and ground through a 120 mesh sieve to obtain modified zirconium oxide powder;

[0028] Step 2: 0.7 g of Isobam104 gelling agent was mixed with 140 g of ultrapure water, and the pH value was adjusted to 9 by lactic acid and tetramethylammonium hydroxide to obtain a premixed solution, and finally 300 g of modified zirconium oxide powder, 40 g of alumina fiber, and 60 g of yttrium oxide powder were added to the premixed solution, and mixed by ball milling to obtain a mixed slurry;

[0029] Step 3: inject the mixed slurry into the mold after vacuum degassing, the vacuum degassing pressure is -0.7MPa, the vacuum degassing time is 30min, and solidify it under 50℃ water bath wave heating conditions, and the solidification time is 50min; after demolding, dry it in a constant temperature and humidity box with a humidity of 70% and a temperature of 35℃ for 15h to obtain alumina fiber and yttria co-reinforced zirconia ceramic body;

[0030] Step 4: Finally, the ceramic body is sintered in a sintering furnace. The specific sintering process is: heating to 800°C at a rate of 1°C / min, keeping warm for 1 hour, heating to 1750°C at a rate of 1°C / min, keeping warm for 5 hours, to obtain alumina fiber and yttria co-reinforced zirconia ceramics.

[0031] Example 2

[0032] Step 1: Modification of zirconium oxide powder: 10 mL of concentrated sulfuric acid (concentration of 68%) was mixed with 600 mL of anhydrous ethanol and 4 g of dispersant acrylic acid, and then 400 g of zirconium oxide powder was added and mixed, and then ball milled for 18 h. After the material was discharged, it was dried at 70° C. and ground through a 120-mesh sieve to obtain modified zirconium oxide powder;

[0033] Step 2: 1.29 g of Isobam104 gelling agent was mixed with 172 g of ultrapure water to obtain an Isobam aqueous solution, and then the pH value was adjusted to 9 by lactic acid and tetramethylammonium hydroxide to obtain a premixed solution, and finally 320 g of modified zirconium oxide powder, 32 g of alumina fiber, and 48 g of yttrium oxide powder were added to the premixed solution, and mixed by ball milling to obtain a mixed slurry;

[0034] Step 3: inject the mixed slurry into the mold after vacuum degassing, the vacuum degassing pressure is -0.8MPa, the vacuum degassing time is 25min, and the mixed slurry is cured and molded under 55℃ water bath heating conditions, and the curing time is 45min; after demolding, dry it in a constant temperature and humidity box with a humidity of 80% and a temperature of 40℃ for 16h to obtain alumina fiber and yttria co-reinforced zirconia ceramic body;

[0035] Step 4: Finally, the ceramic body is sintered in a sintering furnace. The specific sintering process is: heating to 800°C at a rate of 2°C / min, keeping warm for 2 hours, heating to 1785°C at a rate of 1.5°C / min, keeping warm for 4 hours, to obtain alumina fiber and yttria co-reinforced zirconia ceramics.

[0036] Example 3

[0037] Step 1: Modification of zirconium oxide powder: 12 mL of concentrated nitric acid (concentration of 68%) was mixed with 600 mL of anhydrous ethanol and 6 g of dispersant acrylic acid, and then 400 g of zirconium oxide powder was added and mixed, and then ball milled for 20 h. After the material was discharged, it was dried at 65 ° C and ground through a 120 mesh sieve to obtain modified zirconium oxide powder;

[0038] Step 2: 1.95 g of Isobam110 gelling agent was mixed with 195 g of ultrapure water to obtain an Isobam aqueous solution, and then the pH value was adjusted to 10 by lactic acid and tetramethylammonium hydroxide to obtain a premixed solution, and finally 340 g of modified zirconium oxide powder, 20 g of alumina fiber, and 40 g of yttrium oxide powder were added to the premixed solution, and mixed by ball milling to obtain a mixed slurry;

[0039] Step 3: inject the mixed slurry into the mold after vacuum degassing, the vacuum degassing pressure is -0.9MPa, the vacuum degassing time is 40min, and the mixed slurry is cured and molded under 65℃ water bath heating conditions, and the curing time is 35min; after demolding, dry it in a constant temperature and humidity box with a humidity of 80% and a temperature of 50℃ for 18h to obtain alumina fiber and yttria co-reinforced zirconia ceramic body;

[0040] Step 4: Finally, the ceramic body is sintered in a sintering furnace. The specific sintering process is: heating to 800°C at a rate of 5°C / min, keeping warm for 1 hour, heating to 1800°C at a rate of 2°C / min, keeping warm for 3 hours, to obtain alumina fiber and yttria co-reinforced zirconia ceramics.

[0041] Example 4

[0042] Step 1: Modification of zirconium oxide powder: 14 mL of concentrated nitric acid (concentration of 68%) was mixed with 600 mL of anhydrous ethanol and 8 g of dispersant sodium polyacrylate, and then 400 g of zirconium oxide powder was added and mixed, and then ball milled for 24 h. After the material was discharged, it was dried at 80 ° C and ground through a 120 mesh sieve to obtain modified zirconium oxide powder;

[0043] Step 2: 3.22 g of Isobam304 gelling agent was mixed with 215 g of ultrapure water to obtain an Isobam aqueous solution, and then the pH value was adjusted to 11 by lactic acid and tetramethylammonium hydroxide to obtain a premixed solution, and finally 360 g of modified zirconium oxide powder, 20 g of alumina fiber, and 20 g of yttrium oxide powder were added to the premixed solution, and mixed by ball milling to obtain a mixed slurry;

[0044] Step 3: inject the mixed slurry into the mold after vacuum degassing, the vacuum degassing pressure is -1MPa, the vacuum degassing time is 10min, and solidify it in a 70℃ water bath heating condition, and the solidification time is 30min; after demolding, dry it in a constant temperature and humidity box at a humidity of 85% and a temperature of 45℃ for 20h to obtain alumina fiber and yttria co-reinforced zirconia ceramic body;

[0045] Step 4: Finally, the ceramic body is sintered in a sintering furnace. The specific sintering process is: heating to 800°C at a rate of 5°C / min, keeping warm for 1.5 hours, heating to 1850°C at a rate of 3°C / min, keeping warm for 5 hours, to obtain alumina fiber and yttria co-reinforced zirconia ceramics.

[0046] Figure 1 This is the process flow diagram used in Examples 1-4.

[0047] Comparative Example

[0048] Step 1: 1.29 g of Isobam104 gelling agent was mixed with 172 g of ultrapure water to obtain an Isobam aqueous solution, and then the pH value was adjusted to 11 by lactic acid and tetramethylammonium hydroxide to obtain a premixed solution, and finally 400 g of zirconium oxide powder was added to the premixed solution, and the zirconium oxide slurry was obtained by ball milling;

[0049] Step 2: inject the mixed slurry into the mold after vacuum degassing, the vacuum degassing pressure is -1MPa, the vacuum degassing time is 30min, and solidify it in a 60℃ water bath heating condition, and the solidification time is 40min; after demolding, dry it in a constant temperature and humidity box with a humidity of 80% and a temperature of 40℃ for 16h to obtain a zirconia ceramic body;

[0050] Step 3: Finally, the ceramic body is sintered in a sintering furnace. The specific sintering process is: heating to 800°C at a rate of 2°C / min, keeping warm for 2h, heating to 1785°C at a rate of 1.5°C / min, keeping warm for 4h, to obtain zirconia ceramics.

[0051] Effect verification:

[0052] The bending strength, density and fracture toughness of the alumina fiber and yttria co-reinforced zirconia ceramics obtained in Examples 1, 2, 3 and 4 and the zirconia ceramics obtained in the comparative example were tested according to the following standards. The test results are shown in Table 1.

[0053] Bending strength test: follow GB / T 6569-2006.

[0054] Density test: Archimedes drainage method.

[0055] Fracture toughness test: Single-side notched beam method is adopted, and the testing instrument is an electronic universal testing machine.

[0056] Table 1 Ceramic performance test results obtained in Examples 1-4 and Comparative Examples

[0057]

[0058] As shown in Table 1, the strength and toughness of zirconia ceramics reinforced by alumina fiber and yttria are significantly improved, with the strength increasing from 123MPa to 158MPa and the toughness increasing from 2.8MPa·m 1 / 2 Increased to 3.6MPa·m 1 / 2 The relative density is increased by 1.7%, indicating that the alumina fiber and yttria co-reinforced zirconia ceramic has higher flexural strength and toughness, and higher density.

[0059] The above description is only a specific implementation mode of the present invention, but the protection scope of the present invention is not limited thereto. Any modifications, equivalent substitutions and improvements made by any technician familiar with the technical field within the technical scope disclosed by the present invention and within the spirit and principle of the present invention should be covered by the protection scope of the present invention.

Claims

1. A method for preparing alumina fiber and yttria co-reinforced zirconia ceramics by gel casting, characterized in that: The following steps are involved: Step 1, modification of zirconium oxide powder: the modifier, anhydrous ethanol and dispersant are stirred and mixed evenly in a certain mass ratio, and then added into the zirconium oxide powder and mixed, and then ball milled, the material is dried after discharge, and then ground and sieved to obtain modified zirconium oxide powder; Step 2, slurry preparation: Isobam gelling agent is mixed with ultrapure water to prepare Isobam aqueous solution, and the pH is adjusted to 9-11 by lactic acid and tetramethylammonium hydroxide to obtain a premixed solution; then modified zirconium oxide powder, alumina fiber and yttrium oxide are added to the premixed solution, and mixed by ball milling to obtain a mixed slurry; Step 3: Curing and forming: inject the mixed slurry into the mold after vacuum degassing, and cure it in a water bath; Step 4: Sintering: After demoulding, the ceramic body is dried to obtain a ceramic body, and finally the ceramic body is sintered in a sintering furnace to obtain alumina fiber and yttria co-reinforced zirconia ceramics.

2. The method for preparing a gel-casting alumina fiber and yttria co-reinforced zirconia ceramic according to claim 1, characterized in that: In step 1, the amount of zirconium oxide added is 40wt%-50wt% of the slurry mass, the modifier is concentrated sulfuric acid or concentrated nitric acid, the concentration is 68%, and the amount added is 2-5% of the powder mass; the dispersant is one or more of ammonium citrate, acrylic acid, and sodium polyacrylate, and the amount added is 0.5-2% of the powder mass; the ball milling time is 16-24h; dried at 60-80°C and passed through a 120-mesh sieve.

3. The method for preparing a gel-casting alumina fiber and yttria co-reinforced zirconia ceramic according to claim 1, characterized in that: In step 2, the Isobam gelling agent is one or more of Isobam104, Isobam110, and Isobam304, and the added amount is 0.5-1.5wt% of ultrapure water; the modified zirconia powder accounts for 75-90% of the total mass of the powder, the alumina fiber accounts for 5-10% of the total mass of the powder, the yttrium oxide accounts for 5-15% of the total mass of the powder, and the powder accounts for 65-75% of the total mass of the slurry.

4. The method for preparing a gel-casting alumina fiber and yttria co-reinforced zirconia ceramic according to claim 1, characterized in that: In step three, the vacuum degassing pressure is -0.7 to -1 MPa, and the vacuum degassing time is 10-30 min; the water bath heating temperature is 50-70°C, and the curing time is 30-50 min.

5. The method for preparing a gel-casting alumina fiber and yttria co-reinforced zirconia ceramic according to claim 1, characterized in that: In step 4, the specific process of drying is: drying in a constant temperature and humidity chamber at a humidity of 70-85% and a temperature of 35-50°C for 15-20 hours. The specific process of sintering is: heating to 800°C at a rate of 1-5°C / min, keeping warm for 1-2 hours, heating to 1750-1850°C at a rate of 1-3°C / min, and keeping warm for 2-5 hours.

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