Tape casting silicon dioxide reinforced yttrium oxide ceramic and preparation method thereof

Abstract

The method comprises the following steps: firstly, preparing silicon dioxide-yttrium oxide mixed powder by adopting a spray granulation method, then preparing high-solid-content slurry, carrying out tape casting, and carrying out drying and sintering to obtain the silicon dioxide-reinforced yttrium oxide ceramic. The silicon dioxide-yttrium oxide mixed powder is prepared by adopting an improved spray granulation method, the prepared powder is uniform, the mechanical property of yttrium oxide ceramic is improved by silicon dioxide in the powder, and the adopted tape casting technology is environment-friendly, high in production efficiency, good in green body quality and lower in cost; the prepared silicon dioxide reinforced yttrium oxide ceramic is good in wear resistance, good in toughness 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 tape-casting silicon dioxide reinforced yttria ceramic and a preparation method thereof. Background Art

[0002] Yttria (Y2O3) ceramics are an important functional ceramic material. Due to its excellent physical and chemical properties, such as high melting point (about 2430°C), high hardness, good oxidation resistance and low thermal expansion coefficient, it is widely used in aerospace, nuclear industry, high-temperature structural materials, optical components and other fields. However, pure yttria ceramics have obvious defects in practical applications, such as high brittleness, low bending strength and insufficient fracture toughness. These defects limit the further application of yttria ceramics in extreme environments.

[0003] In order to solve the brittleness problem of pure yttria ceramics, researchers have tried to introduce reinforcing phases into yttria ceramics to improve their mechanical and thermal properties. Common reinforcing materials include carbides (such as SiC), oxides (such as ZrO2, Al2O3) and silicides. Among them, nano-silicon dioxide (SiO2) has become an ideal reinforcing phase due to its excellent interface bonding properties, low density and stability at high temperatures. However, the existing technology still has problems in practical applications, such as uneven distribution of reinforcing phases, insufficient sintering density, and poor process adaptability.

[0004] Chinese patent application CN105110793A: "A method for preparing yttrium oxide ceramics with high thermal shock resistance", this patent proposes a method for preparing yttrium oxide ceramics with silicon dioxide as a reinforcing phase, and improves the thermal shock resistance of ceramics by combining spray granulation with cold isostatic pressing process. However, the main defect of this technology is that the cold isostatic pressing of granulated powder is prone to uneven powder distribution, which leads to increased interfacial stress during sintering and easily induces microcracks. In addition, this technology does not improve the forming process of complex-shaped blanks, which limits its promotion in practical applications. Chinese patent application CN106830962A: "A silica-modified porous zirconia ceramic and its preparation method", this patent significantly improves the toughness and thermal shock resistance of ceramics by uniformly doping silicon dioxide particles into the ceramic matrix. However, in its preparation method, the reinforcing phase and matrix powder are mixed by ordinary physical mixing, which fails to fully solve the problem of uneven distribution of the reinforcing phase. In addition, it adopts the traditional atmospheric pressure sintering method, which cannot meet the preparation requirements of high-density ceramics. Summary of the invention

[0005] The purpose of the present invention is to provide a tape-casting silica-reinforced yttria ceramic and a preparation method thereof. The present invention adopts a spray granulation method to prepare a silica-yttria mixed powder, then prepares a high-solid content slurry, performs tape-casting, and obtains silica-reinforced yttria ceramics through drying and sintering. 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 have the advantages of high strength, good toughness, good wear resistance, etc.

[0006] The technical solution adopted by the present invention is as follows:

[0007] A tape-casting silicon dioxide reinforced yttria ceramic and a preparation method thereof, comprising the following steps:

[0008] Step 1, powder preparation: high-purity yttrium oxide and nano-silicon dioxide are mixed in proportion, ethanol solvent and dispersant are added, and ultrasonic dispersion treatment is performed; uniform composite powder is obtained by spray drying; the composite powder is placed at 900-1100°C for high-temperature pre-sintering treatment, so that the nano-silicon dioxide and yttrium oxide partially react to form a composite phase with a tight interface bonding;

[0009] Step 2, tape casting: mixing a dispersant, a pH regulator and water into a premixed solution, adding the prepared composite powder into the premixed solution, adjusting the solid content to 40%-50%, and preparing a ceramic green body by tape casting; after drying, cutting into a ceramic body of a predetermined size;

[0010] Step 3, hot isostatic pressing: Place the cut ceramic body in a hot isostatic pressing device for hot isostatic pressing at a pressure of 50-200 MPa, a temperature of 1200-1500° C., and a time of 2-4 hours to improve the density of the body.

[0011] Step 4, sintering: under vacuum, place the hot isostatic pressing body in a sintering furnace, heat it to 800°C at a rate of 1-5°C / min, keep it warm for 1-2h, heat it to 1780-1850°C at a rate of 1-3°C / min, and keep it warm for 2-5h; during the sintering process, the densification and grain refinement are promoted by regulating the heating rate and the atmosphere changes in the insulation stage, so as to obtain the final ceramic material.

[0012] Preferably, in step 1, the content of yttrium oxide in the composite powder is 85-95%, and the content of nano-silicon dioxide is 5-15%.

[0013] Preferably, in step 1, the dispersant is one of polyvinyl pyrrolidone and PVP, and the added amount is 0.5-2% of the powder; the ultrasonic dispersion time of the powder is 30-60min, the feed temperature of the spray drying is 150-200°C, and the outlet temperature is 80-120°C.

[0014] Preferably, in step 2, the dispersant is one or more of ammonium citrate, sodium polyacrylate, and acrylic acid, and the added amount is 1-3% of the powder; the pH of the premixed solution is 8-11.

[0015] Compared with the prior art, the present invention has the following beneficial effects:

[0016] (1) The present invention greatly improves the flexural strength and fracture toughness of ceramics through the reinforcement effect of nano-silicon dioxide, significantly improving the brittleness problem of traditional yttrium oxide ceramics.

[0017] (2) The present invention adopts a new powder preparation technology and tape casting combined with hot isostatic pressing treatment to make the microstructure of the ceramic body denser and the particle distribution more uniform, thereby improving the overall performance of the ceramic.

[0018] (3) The present invention optimizes the sintering process to obtain a refined grain structure and a tight interface bonding, thereby improving the thermal shock resistance of the ceramic in a high temperature environment.

[0019] (4) The present invention adopts an innovative preparation method combined with tape casting and hot isostatic pressing technology, the process is highly controllable, suitable for the production of ceramic products with complex shapes, and has high industrial promotion value. DETAILED DESCRIPTION

[0020] The present invention is further described in detail below with reference to specific embodiments.

[0021] Example 1

[0022] A method for preparing tape-cast silicon dioxide reinforced yttria ceramics comprises the following steps:

[0023] Step 1, powder preparation: 85g high-purity yttrium oxide (purity ≥99.9%) and 15g nano-silicon dioxide are mixed, 100g ethanol solvent and 1g dispersant polyvinyl pyrrolidone are added, and ultrasonic dispersion treatment is performed for 30min; uniform composite powder is obtained by spray drying, the feed temperature of the spray drying is 150°C, and the outlet temperature is 80°C; then the powder is subjected to high-temperature pre-sintering treatment at a temperature of 900°C to allow the nano-silicon dioxide and yttrium oxide to partially react to form a composite phase with a tight interface bond.

[0024] Step 2, tape casting: 0.34 g of dispersant ammonium citrate and 50 g of deionized water are mixed, and the pH value is adjusted to 8 with lactic acid and tetramethylammonium hydroxide to obtain a premixed solution; 33.34 g of the prepared composite powder is added to the premixed solution, and a ceramic green body is prepared by a tape casting process; after drying, the ceramic green body is cut into a predetermined size.

[0025] Step 3, hot isostatic pressing: Place the green body in a hot isostatic pressing device for hot isostatic pressing at a pressure of 50 MPa, a temperature of 1200° C., and a time of 2 h to improve the density of the body.

[0026] Step 4, sintering process: under vacuum, the green body after hot isostatic pressing is placed in a sintering furnace. The specific process of the sintering process is: heating to 800°C at a rate of 1°C / min, keeping warm for 2h, heating to 1780°C at a rate of 1°C / min, keeping warm for 5h, so as to obtain the final ceramic material.

[0027] Example 2

[0028] A method for preparing tape-cast silicon dioxide reinforced yttria ceramics comprises the following steps:

[0029] Step 1, powder preparation: 88g high-purity yttrium oxide (purity ≥99.9%) and 12g nano-silicon dioxide are mixed, 100g ethanol solvent and 1g dispersant polyvinyl pyrrolidone are added, and ultrasonic dispersion treatment is performed for 40min; uniform composite powder is obtained by spray drying, the feed temperature of the spray drying is 165°C, and the outlet temperature is 100°C; then the powder is subjected to high-temperature pre-sintering treatment at a temperature of 1000°C to allow the nano-silicon dioxide and yttrium oxide to partially react to form a composite phase with a tight interface bond.

[0030] Step 2, tape casting: 0.57 g of dispersant ammonium citrate and 50 g of deionized water are mixed, and the pH value is adjusted to 9 with lactic acid and tetramethylammonium hydroxide to obtain a premixed solution; 37.72 g of the prepared composite powder is added to the premixed solution, and a ceramic green body is prepared by a tape casting process; after drying, the ceramic green body is cut into a predetermined size.

[0031] Step 3, hot isostatic pressing: Place the green body in a hot isostatic pressing device for hot isostatic pressing at a pressure of 100 MPa, a temperature of 1300° C., and a time of 3 h to improve the density of the body.

[0032] Step 4, sintering process: under vacuum, the hot isostatic pressing body is placed in a sintering furnace. The specific process of the sintering process is: heating to 800°C at a rate of 1.5°C / min, keeping warm for 2h, heating to 1800°C at a rate of 1.5°C / min, keeping warm for 4h, so as to obtain the final ceramic material.

[0033] Example 3

[0034] A method for preparing tape-cast silicon dioxide reinforced yttria ceramics comprises the following steps:

[0035] Step 1, powder preparation: 90g high-purity yttrium oxide (purity ≥99.9%) and 10g nano-silicon dioxide are mixed, 100g ethanol solvent and 1.5g dispersant polyvinyl pyrrolidone are added, and ultrasonic dispersion treatment is performed for 50min; uniform composite powder is obtained by spray drying, the feed temperature of the spray drying is 180°C, and the outlet temperature is 110°C; then the powder is subjected to high-temperature pre-sintering treatment at a temperature of 1000°C to allow the nano-silicon dioxide and yttrium oxide to partially react to form a composite phase with a tight interface bond.

[0036] Step 2, tape casting: 0.92 g of dispersant sodium polyacrylate and 50 g of deionized water are mixed, and the pH value is adjusted to 10 with lactic acid and tetramethylammonium hydroxide to obtain a premixed solution; 46.15 g of the prepared composite powder is added to the premixed solution, and a ceramic green body is prepared by tape casting; after drying, the ceramic green body is cut into a predetermined size.

[0037] Step 3, hot isostatic pressing: Place the green body in a hot isostatic pressing device for hot isostatic pressing at a pressure of 150 MPa, a temperature of 1400° C., and a time of 3 h to improve the density of the body.

[0038] Step 4, sintering process: under vacuum, the hot isostatic pressing body is placed in a sintering furnace. The specific process of the sintering process is: heating to 800°C at a rate of 3°C / min, keeping warm for 2h, heating to 1825°C at a rate of 2°C / min, keeping warm for 3.5h, so as to obtain the final ceramic material.

[0039] Example 4

[0040] A method for preparing tape-cast silicon dioxide reinforced yttria ceramics comprises the following steps:

[0041] Step 1, powder preparation: 95g high-purity yttrium oxide (purity ≥99.9%) and 5g nano-silicon dioxide are mixed, 100g ethanol solvent and 2g dispersant polyvinyl pyrrolidone are added, and ultrasonic dispersion treatment is performed for 60min; uniform composite powder is obtained by spray drying, the feed temperature of the spray drying is 200°C, and the outlet temperature is 120°C; then the powder is subjected to high-temperature pre-sintering treatment at a temperature of 1100°C to make the nano-silicon dioxide and yttrium oxide partially react to generate a composite phase with a tight interface bonding.

[0042] Step 2, tape casting: 1.5 g of dispersant acrylic acid and 50 g of deionized water are mixed, and the pH value is adjusted to 11 with lactic acid and tetramethylammonium hydroxide to obtain a premixed solution; 50 g of the prepared composite powder is added to the premixed solution, and a ceramic green body is prepared by tape casting; after drying, the green body is cut into a ceramic body of a predetermined size.

[0043] Step 3, hot isostatic pressing: Place the green body in a hot isostatic pressing device for hot isostatic pressing at a pressure of 200 MPa, a temperature of 1500° C., and a time of 2 h to improve the density of the body.

[0044] Step 4, sintering process: under vacuum, the hot isostatic pressing body is placed in a sintering furnace. The specific process of the sintering process is: heating to 800°C at a rate of 5°C / min, keeping warm for 2h, heating to 1850°C at a rate of 3°C / min, keeping warm for 2h, so as to obtain the final ceramic material.

[0045] Comparative Example

[0046] A method for preparing tape-cast silicon dioxide reinforced yttria ceramics comprises the following steps:

[0047] Step 1, powder preparation: 95g of high-purity yttrium oxide (purity ≥99.9%) is added to 100g of ethanol solvent and 2g of dispersant polyvinyl pyrrolidone, and ultrasonic dispersion treatment is performed for 60min; uniform yttrium oxide powder is obtained by spray drying, the feed temperature of the spray drying is 200°C, and the outlet temperature is 120°C; then the powder is subjected to high-temperature pre-sintering treatment at a temperature of 1100°C.

[0048] Step 2, tape casting: 1.5 g of dispersant acrylic acid and 50 g of deionized water are mixed, and the pH value is adjusted to 11 with lactic acid and tetramethylammonium hydroxide to obtain a premixed solution; 50 g of the prepared composite powder is added to the premixed solution, and a ceramic green body is prepared by tape casting; after drying, the green body is cut into a ceramic body of a predetermined size.

[0049] Step 3, hot isostatic pressing: Place the green body in a hot isostatic pressing device for hot isostatic pressing at a pressure of 200 MPa, a temperature of 1500° C., and a time of 2 h to improve the density of the body.

[0050] Step 4, sintering process: under vacuum, the hot isostatic pressing body is placed in a sintering furnace. The specific process of the sintering process is: heating to 800°C at a rate of 5°C / min, keeping warm for 2h, heating to 1850°C at a rate of 3°C / min, keeping warm for 2h, so as to obtain the final ceramic material.

[0051] Effect verification:

[0052] The bending strength, density and wear rate of the ceramic materials obtained in the above-mentioned Examples 1, 2, 3 and 4 and the 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 was used to test sample density.

[0055] Wear test: The test is carried out using a wear tester in accordance with EN ISO 26424-2016.

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

[0057] Example Bending strength(MPa) <![CDATA[Density (g / cm 3 )]]> <![CDATA[Wear rate (mm 3 / N m)]]> Example 1 112 5.01 <![CDATA[6.90×10 -9 ]]> Example 2 125 5.06 <![CDATA[6.82×10 -9 ]]> Example 3 110 4.99 <![CDATA[6.85×10 -9 ]]> Example 4 112 5.02 <![CDATA[6.77×10 -9 ]]> Comparative Example 102 4.92 <![CDATA[9.57×10 -9 ]]>

[0058] As shown in Table 1, the strength, density and wear resistance of the yttria-doped silica ceramics prepared by the present invention are all better than those of the yttria ceramics obtained in the comparative example, indicating that the doping of silica can improve the strength and density of the yttria ceramics to a certain extent, and improve the wear resistance to a certain extent.

[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 tape-cast silica-reinforced yttria ceramics, characterized in that: The following steps are involved: Step 1, powder preparation: high-purity yttrium oxide and nano-silicon dioxide are mixed in proportion, ethanol solvent and dispersant are added, and ultrasonic dispersion treatment is performed; uniform composite powder is obtained by spray drying; the composite powder is placed at 900-1100°C for high-temperature pre-sintering treatment, so that the nano-silicon dioxide and yttrium oxide partially react to form a composite phase with a tight interface bonding; Step 2, tape casting: mixing a dispersant, a pH regulator and water into a premixed solution, adding the prepared composite powder into the premixed solution, adjusting the solid content to 40%-50%, and preparing a ceramic green body by tape casting; after drying, cutting into a ceramic body of a predetermined size; Step 3, hot isostatic pressing: placing the cut ceramic body in a hot isostatic pressing device for hot isostatic pressing at a pressure of 50-200 MPa, a temperature of 1200-1500° C., and a time of 2-4 hours to improve the density of the body; Step 4, sintering: Under vacuum, place the hot isostatic pressing body in a sintering furnace, first heat it to 800°C at a rate of 1-5°C / min, keep it warm for 1-2h, then heat it to 1780-1850°C at a rate of 1-3°C / min, keep it warm for 2-5h; during the sintering process, by regulating the changes in the heating rate and the insulation stage, densification and grain refinement are promoted to obtain the final ceramic material.

2. The method for preparing a tape-cast silica-reinforced yttria ceramic according to claim 1, characterized in that: In step 1, the content of yttrium oxide in the composite powder is 85-95%, and the content of nano-silicon dioxide is 5-15%.

3. The method for preparing a tape-cast silica-reinforced yttria ceramic according to claim 1, characterized in that: The dispersant in step 1 is one of polyvinyl pyrrolidone and PVP, and the amount of the dispersant added is 0.5-2% of the powder; the ultrasonic dispersion time of the powder is 30-60 minutes, the feed temperature of the spray drying is 150-200°C, and the outlet temperature is 80-120°C.

4. The method for preparing a tape-cast silica-reinforced yttria ceramic according to claim 1, characterized in that: The dispersant in step 2 is one or more of ammonium citrate, sodium polyacrylate, and acrylic acid, and the added amount is 1-3% of the powder; the pH of the premixed solution is 8-11.

5. A tape-cast silica-reinforced yttria ceramic, characterized in that: Prepared by the preparation method according to any one of claims 1 to 5.