Method for preparing silicon dioxide doped yttrium oxide ceramic by adopting green gel casting

Abstract

The invention discloses a method for preparing silicon dioxide doped yttrium oxide ceramic by adopting green gel casting, which comprises the following steps: firstly modifying yttrium oxide powder, then doping silicon dioxide in the yttrium oxide powder, finally carrying out green gel casting by adopting an Isobam gelling agent, and sintering to obtain the yttrium oxide doped silicon dioxide ceramic. According to the preparation method, the modified yttrium oxide powder is prepared by adopting the surfactant, hydrolysis of the yttrium oxide powder is effectively prevented through modification, silicon dioxide is doped in the yttrium oxide powder, the sintering activity of yttrium oxide is improved, and an adopted Isobam gel system is environmentally friendly, high in production efficiency, good in blank quality and lower in cost; the prepared yttrium oxide doped silicon dioxide ceramic is good in wear resistance, high in density and high in strength.

Description

Technical Field

[0001] The invention relates to the technical field of inorganic ceramic material preparation, and in particular to a method for preparing silicon dioxide-doped yttria ceramics by adopting green gel injection molding. Background Art

[0002] At present, ceramic materials have become an indispensable key in alloy smelting and casting, especially in titanium-aluminum alloy smelting and casting. Due to the high chemical reactivity of molten titanium alloy, it can interact with almost all refractory materials. Commonly used oxide refractory materials have good thermodynamic stability in reaction with titanium-aluminum alloys. Y2O3 and SiO2 are the most promising ceramic shell materials for titanium-aluminum alloy casting.

[0003] Studies have shown that the reaction between silica and titanium liquid is relatively weak, however, there are challenges in the practical application of silica as a shell material. The silica shell has a certain degree of hygroscopicity, which can easily lead to volume expansion and cracking after contact with high temperatures. Therefore, strict humidity requirements must be met, which increases the complexity of the practical application of silica as a shell material. Although yttrium oxide is recognized as the most stable oxide refractory material, its limitations in thermal shock resistance and high sintering temperature have hindered its widespread adoption.

[0004] Traditional methods for preparing silica composite ceramics include injection molding and slip casting, but it is difficult to prepare high-performance silica. At present, green gel injection molding is mostly used, which forms a macromolecular network structure or a ceramic network structure through chemical reactions inside the slurry, so that the ceramic slurry poured into the non-porous mold can quickly solidify into a ceramic body. The structure and density of the molded product are uniform, the gel injection molding cycle is short, the performance is reliable, and it is conducive to industrial application production. Summary of the invention

[0005] The purpose of the present invention is to provide a method for preparing silica-doped yttrium oxide ceramics by green gel casting. The present invention adopts gel casting to prepare oxide refractory materials. This molding method realizes the multifunctional production of yttrium oxide refractory products of various complex shapes. We have successfully obtained a concentrated suspension containing yttrium oxide and silica through a powder pretreatment process, which also solves the dual problems of yttrium oxide sintering characteristic challenges and thermal shock brittleness. The preparation process of the present invention is simple, the gel system used is non-toxic and harmless, environmentally friendly, and has high production efficiency. The prepared ceramics can have the advantages of high strength, high density, good wear resistance, etc.

[0006] The technical solution adopted by the present invention is as follows: A method for preparing silicon dioxide-doped yttrium oxide ceramics by green gel casting comprises the following steps:

[0007] Step 1: firstly, yttrium oxide is dispersed in anhydrous ethanol, and the mass fraction of yttrium oxide is 30wt%-40wt%; sulfuric acid is added under stirring conditions, ball milled in a ball mill, and modified yttrium oxide powder is obtained after drying and sieving;

[0008] Step 2: ball-milling and mixing deionized water, a dispersant, modified yttrium oxide powder and tetraethylchlorosilicate, drying and sieving to obtain yttrium oxide-doped silica powder;

[0009] Step 3: Isobam solution, tetramethylammonium hydroxide and ultrapure water are mixed in a certain proportion to prepare a premixed solution, and the premixed solution, sintering aid, yttrium oxide-doped silica powder and grinding balls obtained in step 2 are put into a ball mill to obtain a mixed slurry;

[0010] Step 4: inject the yttrium oxide doped silica slurry into a mold after vacuum degassing, solidify and shape it under microwave heating conditions, and dry it after demolding to obtain a yttrium oxide doped silica ceramic body; finally, sinter the ceramic body in a sintering furnace to obtain a yttrium oxide doped silica ceramic.

[0011] Preferably, the concentration of sulfuric acid is not less than 98%, and the amount added is 2-5wt% of yttrium oxide; the ball-to-material ratio is (1-3):1; the ball milling time is 16-24h; dried at 60-80°C and passed through a 120-mesh sieve.

[0012] Preferably, the dispersant is one of ammonium citrate, sodium polyacrylate and polyethylene glycol, and the amount of the dispersant added is 0.05%-0.8% of the modified yttrium oxide powder; the amount of tetraethylchlorosilicate added is 2-5% of the modified yttrium oxide powder; and deionized water accounts for 26-40% of the total mass of the slurry.

[0013] Preferably, the Isobam solution is a solution in which one or more powders of Isobam104 and Isobam600 are fully dissolved in ultrapure water at a concentration of 10-25%; the Isobam solution, tetramethylammonium hydroxide and ultrapure water are mixed in a ratio of 1:(2-3):(140-160); the amount of yttrium oxide doped silica powder added is 60-75% of the total mass of the slurry; the sintering aid is MgO-TiO2, and the added amount is 0.5-1wt% of the yttrium oxide doped silica powder.

[0014] Preferably, the vacuum degassing pressure is -0.5 to -1 MPa, and the vacuum degassing time is 40-60 min; the microwave heating temperature is 30-40°C, and the curing time is 5-10 min; the specific drying process is: drying in a constant temperature and humidity box with a humidity of 70-85% and a temperature of 35-50°C for 15-20 h.

[0015] 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 1780-1850°C at a rate of 1-3°C / min, and keeping warm for 2-5h.

[0016] Compared with the prior art, the present invention has the following beneficial effects:

[0017] (1) The present invention adopts a new modification technology to obtain silicon dioxide-doped yttrium oxide powder through a powder pretreatment process, which solves the dual problems of yttrium oxide's easy shrinkage during sintering and easy brittleness due to thermal shock. In addition, the densification temperature is significantly reduced during ceramic sintering, and dense ceramics can be obtained.

[0018] (2) The present invention uses sulfuric acid to treat the powder, which, on the one hand, effectively prevents the hydrolysis of yttrium oxide. On the other hand, after sulfuric acid corrosion and ball milling mixing, the particle size of the yttrium oxide powder is further reduced, the surface activity is increased, and it is denser during sintering.

[0019] (3) The green gelcasting technology adopted by the present invention has a simple process, can obtain a slurry with good dispersibility, can form yttria ceramics with complex shapes, and has high strength of the ceramic body. The most important thing is that the drying shrinkage and sintering shrinkage of the samples prepared by this gel system are uniform and calculable, the processing allowance is small, and the subsequent processing is greatly reduced, which is lower in cost. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 This is a process roadmap for the green gel injection molding technology used in Examples 1-4 of the present invention. DETAILED DESCRIPTION

[0021] The present invention is further described in detail below with reference to the accompanying drawings and specific embodiments.

[0022] Example 1

[0023] A method for preparing silicon dioxide-doped yttrium oxide ceramics by green gelcasting, the process route is as follows Figure 1 As shown, the following steps are included:

[0024] Step 1: First, 300 g of yttrium oxide was dispersed in 1 L of anhydrous ethanol, 6 g of sulfuric acid was added under stirring, and the mixture was ball-milled in a ball mill for 16 h with a ball-to-material ratio of 1:1. The mixture was dried at 60 ° C and passed through a 120-mesh sieve to obtain modified yttrium oxide powder;

[0025] Step 2: Add 72g of deionized water, 0.1g of dispersant ammonium citrate, 200g of modified yttrium oxide powder, and 4g of tetraethyl chlorosilicate into a ball mill, mix and disperse, dry and sieve to obtain yttrium oxide-doped silica powder;

[0026] Step 3: 5.56 g of Isobam104 gelling agent is mixed with 50 g of ultrapure water to obtain an Isobam aqueous solution, and then 1 g of the Isobam aqueous solution is mixed with 2 g of tetramethylammonium hydroxide and 140 g of ultrapure water to obtain a premixed solution, and finally 220 g of yttrium oxide-doped silica powder and 1.1 g of MgO-TiO2, a sintering aid, are added to the premixed solution, and the yttrium oxide-doped silica slurry is obtained by ball milling and mixing;

[0027] Step 4: After vacuum degassing, the yttrium oxide doped silica slurry is injected into the mold, the vacuum degassing pressure is -0.5MPa, the vacuum degassing time is 40min, and the curing is carried out under 30℃ microwave heating conditions, and the curing time is 5min; after demolding, it is dried in a constant temperature and humidity box with a humidity of 70% and a temperature of 35℃ for 15h. The yttrium oxide doped silica ceramic body is obtained; finally, the ceramic body is sintered in a sintering furnace, and the specific sintering process is: heating to 800℃ at a rate of 1℃ / min, keeping warm for 1h, heating to 1780℃ at a rate of 1℃ / min, keeping warm for 5h, and obtaining yttrium oxide doped silica ceramics.

[0028] Example 2

[0029] A method for preparing silicon dioxide-doped yttrium oxide ceramics by green gelcasting, the process route is as follows Figure 1 As shown, the following steps are included:

[0030] Step 1: First, 330 g of yttrium oxide was dispersed in 1 L of anhydrous ethanol, 9.9 g of sulfuric acid was added under stirring, and the mixture was ball-milled in a ball mill for 18 h with a ball-to-material ratio of 1.5:1. The mixture was dried at 70 ° C and passed through a 120-mesh sieve to obtain modified yttrium oxide powder;

[0031] Step 2: Add 88g of deionized water, 0.5g of dispersant ammonium citrate, 200g of modified yttrium oxide powder, and 6g of tetraethyl chlorosilicate into a ball mill, mix and disperse, dry and sieve to obtain yttrium oxide-doped silica powder;

[0032] Step 3: 7.47 g of Isobam104 gelling agent was mixed with 50 g of ultrapure water to obtain an Isobam aqueous solution, and then 1 g of the Isobam aqueous solution was mixed with 2.2 g of tetramethylammonium hydroxide and 145 g of ultrapure water to obtain a premixed solution, and finally 270 g of yttrium oxide-doped silica powder and 1.62 g of MgO-TiO2, a sintering aid, were added to the premixed solution, and yttrium oxide-doped silica slurry was obtained by ball milling.

[0033] Step 4: Inject the yttrium oxide doped silica slurry into the mold after vacuum degassing, the vacuum degassing pressure is -0.6MPa, the vacuum degassing time is 45min, and solidify it under 35℃ microwave heating conditions, the curing time is 7min; after demolding, dry it in a constant temperature and humidity chamber with a humidity of 80% and a temperature of 40℃ for 16h to obtain a yttrium oxide doped silica ceramic body; finally, sinter the ceramic body in a sintering furnace, and the specific sintering process is: heat up to 800℃ at a rate of 2℃ / min, keep warm for 2h, heat up to 1785℃ at a rate of 1.5℃ / min, keep warm for 4h, and obtain yttrium oxide doped silica ceramics.

[0034] Example 3

[0035] A method for preparing silicon dioxide-doped yttrium oxide ceramics by green gelcasting, the process route is as follows Figure 1 As shown, the following steps are included:

[0036] Step 1: First, 350 g of yttrium oxide was dispersed in 1 L of anhydrous ethanol, 14 g of sulfuric acid was added under stirring, and the mixture was ball-milled in a ball mill for 20 h with a ball-to-material ratio of 2:1. The mixture was dried at 75 ° C and passed through a 120-mesh sieve to obtain modified yttrium oxide powder.

[0037] Step 2: Add 110 g of deionized water, 1 g of dispersant ammonium citrate, 200 g of modified yttrium oxide powder, and 8 g of tetraethyl chlorosilicate into a ball mill, mix and disperse, dry and sieve to obtain yttrium oxide-doped silica powder;

[0038] Step 3: 8.82 g of Isobam110 gelling agent was mixed with 50 g of ultrapure water to obtain an Isobam aqueous solution, and then 1 g of the Isobam aqueous solution was mixed with 2.5 g of tetramethylammonium hydroxide and 150 g of ultrapure water to obtain a premixed solution, and finally 340 g of yttrium oxide-doped silica powder and 2.04 g of MgO-TiO2, a sintering aid, were added to the premixed solution, and yttrium oxide-doped silica slurry was obtained by ball milling.

[0039] Step 4: Inject the yttrium oxide doped silica slurry into the mold after vacuum degassing, the vacuum degassing pressure is -0.8MPa, the vacuum degassing time is 50min, and solidify under 38℃ microwave heating conditions, the curing time is 9min; after demolding, dry in a constant temperature and humidity chamber with a humidity of 80% and a temperature of 50℃ for 18h to obtain a yttrium oxide doped silica ceramic body; finally, sinter the ceramic body in a sintering furnace, and the specific sintering process is: heat up to 800℃ at a rate of 5℃ / min, keep warm for 1h, heat up to 1800℃ at a rate of 2℃ / min, keep warm for 3h, and obtain yttrium oxide doped silica ceramics.

[0040] Example 4

[0041] A method for preparing silicon dioxide-doped yttrium oxide ceramics by green gelcasting, the process route is as follows Figure 1 As shown, the following steps are included:

[0042] Step 1: First, 400 g of yttrium oxide was dispersed in 1 L of anhydrous ethanol, 20 g of sulfuric acid was added under stirring, and the mixture was ball-milled in a ball mill for 24 h with a ball-to-material ratio of 3:1. The mixture was dried at 80 ° C and passed through a 120-mesh sieve to obtain modified yttrium oxide powder.

[0043] Step 2: Add 136 g of deionized water, 1.6 g of dispersant ammonium citrate, 200 g of modified yttrium oxide powder, and 10 g of tetraethyl chlorosilicate into a ball mill, mix and disperse, dry and sieve to obtain yttrium oxide-doped silica powder;

[0044] Step 3: 12.5 g of Isobam304 gelling agent is mixed with 50 g of ultrapure water to obtain an Isobam aqueous solution, and then 1 g of the Isobam aqueous solution is mixed with 3 g of tetramethylammonium hydroxide and 160 g of ultrapure water to obtain a premixed solution, and finally 430 g of yttrium oxide-doped silica powder and 2.58 g of MgO-TiO2, a sintering aid, are added to the premixed solution, and the yttrium oxide-doped silica slurry is obtained by ball milling and mixing;

[0045] Step 4: Inject the yttrium oxide doped silica slurry into the mold after vacuum degassing, the vacuum degassing pressure is -1MPa, the vacuum degassing time is 60min, and solidify it under 40℃ microwave heating conditions, and the curing time is 10min; after demolding, dry it in a constant temperature and humidity chamber with a humidity of 85% and a temperature of 45℃ for 20h to obtain a yttrium oxide doped silica ceramic body; finally, sinter the ceramic body in a sintering furnace, and the specific sintering process is: heat up to 800℃ at a rate of 5℃ / min, keep warm for 1.5h, heat up to 1850℃ at a rate of 3℃ / min, keep warm for 5h, and obtain yttrium oxide doped silica ceramics.

[0046] Comparative Example

[0047] A method for preparing green yttria ceramics by gel injection molding comprises the following steps:

[0048] Step 1: First, 330 g of yttrium oxide was dispersed in 1 L of anhydrous ethanol, 9.9 g of sulfuric acid was added under stirring, and the mixture was ball-milled in a ball mill for 18 h with a ball-to-material ratio of 2:1. The mixture was dried at 70 ° C and passed through a 120-mesh sieve to obtain modified yttrium oxide powder;

[0049] Step 2: Add 88 g of deionized water, 0.5 g of dispersant ammonium citrate, and 200 g of modified yttrium oxide powder into a ball mill, mix and disperse, dry and sieve to obtain yttrium oxide powder;

[0050] Step 3: 7.47 g of Isobam104 gelling agent was mixed with 50 g of ultrapure water to obtain an Isobam aqueous solution, and then 1 g of the Isobam aqueous solution was mixed with 2 g of tetramethylammonium hydroxide and 150 g of ultrapure water to obtain a premixed solution, and finally 390 g of yttrium oxide-doped silica powder and 2.34 g of MgO-TiO2, a sintering aid, were added to the premixed solution, and yttrium oxide-doped silica slurry was obtained by ball milling.

[0051] Step 4: Inject the yttrium oxide doped silica slurry into the mold after vacuum degassing, the vacuum degassing pressure is -0.6MPa, the vacuum degassing time is 45min, and solidify under 35℃ microwave heating conditions, the curing time is 7min; after demolding, dry in a constant temperature and humidity chamber with a humidity of 80% and a temperature of 40℃ for 16h to obtain a yttrium oxide doped silica ceramic body; finally, sinter the ceramic body in a sintering furnace, and the specific sintering process is: heat up to 800℃ at a rate of 2℃ / min, keep warm for 2h, heat up to 1785℃ at a rate of 1.5℃ / min, keep warm for 4h, and obtain yttrium oxide ceramics.

[0052] Effect verification:

[0053] The bending strength and toughness of the yttria-doped silica ceramic materials obtained in Examples 1, 2, 3 and 4 and the yttria ceramics obtained in the comparative example were tested according to the following standards. The test results are shown in Table 1.

[0054] Bending strength test: follow GB / T 6569-2006.

[0055] 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]

[0059] As shown in Table 1, the strength and toughness of the ceramics prepared by yttria-doped silica are significantly improved, with the strength increasing from 101 MPa to 135 MPa and the toughness increasing from 4.5 MPa·m 1 / 2 Increase to 5MPa·m 1 / 2 The above results show that yttria ceramics prepared by silica doping have higher flexural strength and toughness.

[0060] 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 silicon dioxide-doped yttria ceramics by green gelcasting, characterized in that: The following steps are involved: Step 1: firstly, yttrium oxide is dispersed in anhydrous ethanol, and the mass fraction of yttrium oxide is 30wt%-40wt%; sulfuric acid is added under stirring conditions, ball milled in a ball mill, and modified yttrium oxide powder is obtained after drying and sieving; Step 2: ball-milling and mixing deionized water, a dispersant, modified yttrium oxide powder and tetraethylchlorosilicate, drying and sieving to obtain yttrium oxide-doped silica powder; Step 3: Isobam solution, tetramethylammonium hydroxide and ultrapure water are mixed in a certain proportion to prepare a premixed solution, and the premixed solution, sintering aid, yttrium oxide-doped silica powder and grinding balls obtained in step 2 are put into a ball mill to obtain a mixed slurry; Step 4: inject the yttrium oxide doped silica slurry into a mold after vacuum degassing, solidify and shape it under microwave heating conditions, and dry it after demolding to obtain a yttrium oxide doped silica ceramic body; finally, sinter the ceramic body in a sintering furnace to obtain a yttrium oxide doped silica ceramic.

2. The method for preparing silicon dioxide-doped yttria ceramics by green gelcasting according to claim 1, characterized in that: In step 1, the concentration of sulfuric acid is not less than 98%, and the amount added is 2-5wt% of yttrium oxide; the ball-to-material ratio is (1-3):1; the ball milling time is 16-24h; dried at 60-80°C and passed through a 120-mesh sieve.

3. The method for preparing silicon dioxide-doped yttria ceramics by green gelcasting according to claim 1, characterized in that: In step 2, the dispersant is one of ammonium citrate, sodium polyacrylate, and polyethylene glycol, and the amount of the dispersant added is 0.05%-0.8% of the modified yttrium oxide powder; the amount of tetraethylchlorosilicate added is 2-5% of the modified yttrium oxide powder; and deionized water accounts for 26-40% of the total mass of the slurry.

4. The method for preparing silicon dioxide-doped yttria ceramics by green gelcasting according to claim 1, characterized in that: In step 3, the Isobam solution is a solution in which one or more powders of Isobam104 and Isobam600 are fully dissolved in ultrapure water at a concentration of 10-25%; the Isobam solution, tetramethylammonium hydroxide and ultrapure water are mixed in a ratio of 1:(2-3):(140-160); the amount of yttrium oxide-doped silica powder added is 60-75% of the total mass of the slurry; the sintering aid is MgO-TiO2, and the added amount is 0.5-1wt% of the yttrium oxide-doped silica powder.

5. The method for preparing silicon dioxide-doped yttria ceramics by green gelcasting according to claim 1, characterized in that: In step 4, the vacuum degassing pressure is -0.5 to -1 MPa, and the vacuum degassing time is 40-60 minutes; the microwave heating temperature is 30-40°C, and the curing time is 5-10 minutes; the specific drying process is: drying in a constant temperature and humidity box with a humidity of 70-85% and a temperature of 35-50°C for 15-20 hours.

6. The method for preparing silicon dioxide-doped yttria ceramics by green gelcasting according to claim 1, characterized in that: In step 4, the specific sintering process is: heating to 800°C at a rate of 1-5°C / min, keeping warm for 1-2h, heating to 1780-1850°C at a rate of 1-3°C / min, and keeping warm for 2-5h.

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