A composite yttrium oxide ceramic and its preparation method

Abstract

The present invention discloses a composite yttrium oxide ceramic and a preparation method thereof, and relates to the technical field of yttrium oxide ceramics. A composite yttrium oxide ceramic is made of the following raw materials in parts by mass: 100 parts of yttrium oxide powder, 5-30 parts of reinforcing phase, 10-50 parts of low-temperature binder, 20-80 parts of dispersion medium, and 1-5 parts of stabilizer. By introducing a stabilizer and a nanoscale reinforcing phase with a specific structure, the hardness and fracture toughness of the ceramic show an enhanced trend, and the overall mechanical properties of the material are optimized. The molecular design of the stabilizer provides a steric hindrance and electrostatic repulsion mechanism, which significantly reduces particle agglomeration and microcrack formation, and the thermal shock resistance and interface bonding strength of the ceramic show an improved trend. The optimized preparation process reduces the defect incidence, and the uniformity and density of the slurry and the green body show an improved trend.

Description

Technical Field

[0001] The present invention relates to the technical field of yttrium oxide ceramics, and in particular to a composite yttrium oxide ceramic and a preparation method thereof. Background Art

[0002] Ceramic materials are widely used in numerous fields due to their outstanding properties, including high-temperature resistance, corrosion resistance, and high hardness. As an important ceramic material, yttria ceramics possess excellent optical, electrical, and thermal properties, showing great potential for application in high-temperature structural materials, electronic ceramics, optical windows, and other fields. However, traditional single yttria ceramics still have some deficiencies in mechanical properties, particularly in thermal shock resistance and fracture toughness, which limits their application in more demanding environments.

[0003] To improve the overall performance of yttria ceramics, researchers have begun exploring methods for introducing reinforcing phases into yttria ceramics. By adding reinforcing phases such as zirconium oxide and silicon carbide to the yttria matrix to form a composite material, the fracture toughness and thermal shock resistance of the ceramic can be effectively enhanced. However, the bonding strength between the reinforcing phase and the matrix is ​​often low, making it difficult for some reinforcing phases to fully function. This can lead to problems such as shedding of the reinforcing phase or interface defects during preparation and use.

[0004] Furthermore, the preparation process for yttrium oxide ceramics also faces numerous challenges. Traditional preparation methods are prone to problems such as agglomeration, uneven distribution, and porosity during powder preparation, molding, and sintering, compromising the density and performance stability of the ceramics. For example, poor powder dispersion during the ball milling stage can lead to uneven density during subsequent molding. During the drying and sintering processes, uneven stress within the green body can cause cracking or deformation.

[0005] To address these issues, the industry has attempted to improve the rheological properties and stability of ceramic slurries by adding low-temperature binders and stabilizers, while also optimizing process parameters such as ball milling time, molding pressure, and drying conditions to enhance the density and mechanical properties of the ceramics. However, the selection and use of existing stabilizers have limitations, and some have poor compatibility with the ceramic system, failing to effectively improve slurry stability and green body strength.

[0006] Therefore, developing a composite yttrium oxide ceramic and its preparation method that can significantly improve the comprehensive performance of yttrium oxide ceramics and at the same time have good preparation process stability has become a technical problem that needs to be solved urgently. Summary of the Invention

[0007] The purpose of the present invention is to overcome the problems of insufficient mechanical properties, weak reinforcing bonding strength, and preparation process defects of yttrium oxide ceramics in the prior art, and to provide a composite yttrium oxide ceramic with high fracture toughness, thermal shock resistance and stable preparation and a preparation method thereof.

[0008] To achieve the above object, the technical solution adopted by the present invention is: a composite yttrium oxide ceramic is made from the following raw materials in parts by mass: 100 parts of yttrium oxide powder, 5-30 parts of reinforcing phase, 10-50 parts of low-temperature binder, 20-80 parts of dispersion medium, and 1-5 parts of stabilizer;

[0009] The stabilizer has a structure shown in Formula 1: Formula 1;

[0010] The R1 is selected from the group consisting of: methyl, ethyl, tert-butyl, and methoxy.

[0011] Furthermore, the reinforcing phase is at least one of zirconium oxide and silicon carbide, and has a particle size of 50-500 nm.

[0012] Furthermore, the low-temperature binder is at least one of silica sol, aluminum sol or aluminum dihydrogen phosphate colloid, with a solid content of 20-40wt%.

[0013] Furthermore, the dispersion medium is at least one of deionized water, anhydrous ethanol or acetone.

[0014] Furthermore, the stabilizer is any one of the compounds shown in the following structures:

[0015] .

[0016] A method for preparing a composite yttrium oxide ceramic comprises the following steps:

[0017] S1. The yttrium oxide powder, reinforcing phase, dispersion medium, and stabilizer are added to a ball mill and milled at ≤50°C for 2-8 hours;

[0018] S2. Add a low-temperature binder and stir the reaction in a 60-90 ° C water bath for 1-3 hours to form a slurry;

[0019] S3. The slurry is injected into the mold and pressed under a pressure of 0.5-5MPa;

[0020] S4. The formed body is aged for 12-24 hours at a humidity of 60-80%;

[0021] S5. Gradient drying at 80-150° C. for 12-48 hours to obtain a composite yttrium oxide ceramic.

[0022] Furthermore, the S2 stirring reaction is carried out in a closed container under a nitrogen atmosphere, and the pH value of the solution is controlled to be 4-6.

[0023] Furthermore, the S3 compression molding adopts isostatic pressing or molding, and the holding time is 10-30 minutes.

[0024] Furthermore, the S5 gradient drying is divided into three stages: constant temperature drying at 80°C±5°C for 4-8 hours; constant temperature drying at 100°C±5°C for 4-8 hours; and constant temperature drying at 120-150°C to constant weight.

[0025] Furthermore, the S1 ball mill uses zirconia grinding balls with a ball-to-material ratio of (2-5):1 and a rotation speed of 200-400 rpm.

[0026] The silanol groups in the stabilizer molecules described herein can bind to the surface of yttrium oxide powder or the reinforcing phase, firmly anchoring the stabilizer to the particle surface. Silane groups hydrolyze into new silanol groups in the slurry's aqueous environment, forming a network structure that wraps around the particles and bridges adjacent particles, providing steric hindrance and preventing nanoparticle aggregation. The large conjugated heteroaromatic rings in the stabilizer molecules have a planar, rigid structure, stretching around the particles like a "molecular brush." ​​This physical barrier significantly increases the energy barrier for particle proximity. Heteroatoms in the heteroaromatic rings can undergo protonation / deprotonation at a slurry pH of 4-6, imparting a charge to the particle surface and enhancing electrostatic repulsion. Combined with steric hindrance, this creates an "electrostatic steric stabilization" mechanism. The cross-linked network formed between the stabilizer particles improves slurry rheology and ensures uniform filling during molding. During the aging (S4) and gradient drying (S5) stages, the stabilizer network acts as a "molecular spring" to buffer shrinkage stresses caused by water evaporation and reduce microcracks. A nitrogen atmosphere prevents oxidation of the silanol groups, ensuring network integrity.

[0027] The reinforcing phase described in this invention has a particle size of 50-500nm. Too small will cause agglomeration, while too large will reduce the reinforcing effect. The stabilizer ensures uniform dispersion, fully utilizing the nano-size effect. Silicon carbide and zirconium oxide complement each other, improving fracture toughness. The solid content of the low-temperature binder is 20-40wt%. Too low a solid content will result in insufficient bonding strength, while too high a solid content will increase the slurry viscosity. The binder cross-links with the stabilizer network, forming a temporary skeleton at temperatures below 150°C, maintaining the green body shape and preventing deformation before sintering.

[0028] Compared with the prior art, the present invention has the following beneficial effects:

[0029] 1. Improved mechanical properties: By introducing stabilizers with specific structures and nano-scale reinforcement phases, the hardness and fracture toughness of ceramics show an enhanced trend, optimizing the overall mechanical properties of the material.

[0030] 2. Improved structural stability: The molecular design of the stabilizer provides steric hindrance and electrostatic repulsion mechanisms, significantly reducing particle agglomeration and microcrack formation, and the thermal shock resistance and interface bonding strength of the ceramic show an improving trend.

[0031] 3. Improved stability of the preparation process: The optimized preparation process (such as nitrogen atmosphere, pH control and gradient drying) reduces the incidence of defects, and the uniformity and density of the slurry and green body show an upward trend. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 For the stabilizer 1 of the present invention 1 HNMR spectrum. DETAILED DESCRIPTION

[0033] The following will clearly and completely describe the technical solution of the present invention in conjunction with the accompanying drawings. Obviously, the embodiments described are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0034] Synthesis example 1

[0035] Synthesis of stabilizer 1:

[0036] ;

[0037] The first step: Under a nitrogen atmosphere, 20 g of raw material 1, 19.84 g of raw material 2, 20.30 g of anhydrous potassium carbonate, 2.55 g of tetrakis(triphenylphosphine)palladium and 230 g of a mixture of toluene, ethanol and aqueous solution in a volume ratio of 2:1:1 were added to the reaction system, heated to 95 ° C and refluxed for 10 hours, turned off the heating, cooled to room temperature, allowed to stand and separated, the aqueous phase was extracted twice with ethyl acetate, the organic phases were combined, the organic phases were dried over anhydrous magnesium sulfate, filtered, and dried, and silica gel column chromatography was performed using a mixture of petroleum ether and ethyl acetate as eluent, and dried to obtain 21.33 g of intermediate 1.

[0038] The second step: under a nitrogen atmosphere, 21.33g of intermediate 1, 21.93g of raw material 3, 0.6g of tri-tert-butyl phosphine, 0.2g of palladium carbon, 15.82g of anhydrous potassium carbonate and 220g of toluene were added to the reaction system, and the temperature was raised to 120°C and refluxed for 12 hours; after the reaction was completed, the temperature was slightly lowered, and diatomaceous earth was used for filtration. After the filtrate was cooled to room temperature, it was washed three times with water, the organic phase was retained, and the aqueous phase was then extracted with ethyl acetate. After the organic phases were combined, the organic phase was dried over anhydrous magnesium sulfate, filtered, spin-dried, and subjected to silica gel column chromatography. A mixture of petroleum ether and ethyl acetate was used as eluent, and spin-dried to obtain 27.81g of stabilizer 1.

[0039] Product structure identification:

[0040] MS (m / z) of intermediate 1: [M+H] + =373;

[0041] MS (m / z) of Stabilizer 1: [M+H] + =611;

[0042] 1HNMR-Chloroform D of stabilizer 1: δ8.39 (dd, 1H), 8.21 (dd, 1H), 8.13-8.06 (m, 1H), 7.82-7.73 (m, 3H), 7.57 (t, 2H), 7.42 (dd, 2H), 7.28-7.13 (m, 3H), 7.09 (m, 1H), 6.46 (s, 3H), 5.38 (q, 1H), 2.80 (m, 2H), 2.49 (d, 3H), 1.63 (t, 2H), 1.53 (s, 2H), 1.10-0.85 (m, 15H).

[0043] Synthesis Example 2-Synthesis Example 4

[0044] In Synthesis Examples 2 to 4, stabilizers 2 to 4 were synthesized sequentially, referring to the synthesis method of Synthesis Example 1, except that raw material 2 was replaced, and the rest was the same as in Synthesis Example 1. The specific structures of raw material 2, stabilizers 2 to 4, and MS (m / z) data are shown in Table 1.

[0045] Table 1. Structure of starting material 2, structure of stabilizer 2-stabilizer 4, and MS (m / z) data involved in Synthesis Examples 2-4.

[0046]

[0047] Example 1

[0048] This embodiment provides a composite yttrium oxide ceramic, the raw material composition of which is calculated by mass as follows: 100 parts of yttrium oxide powder (particle size 0.5-1.0 μm), reinforcing phase: 18 parts of silicon carbide (particle size 200 nm), low-temperature binder: 30 parts of silica sol (solid content 30 wt%), dispersion medium: 50 parts of deionized water, and stabilizer: 13 parts of the stabilizer synthesized in Synthesis Example 1.

[0049] The preparation method comprises the following steps:

[0050] S1. Yttrium oxide powder, silicon carbide, deionized water and stabilizer 1 were added to a zirconia ball mill, with a ball-to-material ratio of 3:1, and ball milled at 40 ° C for 5 hours at a speed of 300 rpm under nitrogen to obtain a uniform slurry;

[0051] S2. Add silica sol to the slurry, transfer it to a closed reactor, maintain an inert atmosphere with nitrogen, and react in a 75°C water bath with stirring for 2 hours. Control the pH to 5.0 (adjust with 0.1 M hydrochloric acid) to form a stable slurry.

[0052] S3 slurry was injected into a stainless steel mold and isostatically pressed at a pressure of 3MPa for 20 minutes to obtain a green body size of Φ50mm×10mm;

[0053] S4. Place the green body in a 70% humidity cabinet and age it for 18 hours.

[0054] S5. Gradient drying, divided into three stages: drying at a constant temperature of 80°C for 6 hours; drying at a constant temperature of 100°C for 6 hours; and drying at a constant temperature of 130°C to constant weight to obtain a composite yttrium oxide ceramic.

[0055] Example 2-Example 4

[0056] A composite yttrium oxide ceramic was prepared by referring to the preparation method of Example 1, except that the stabilizer was replaced with stabilizer 2 to stabilizer 4 prepared in Synthesis Examples 2 to 4, and the rest remained the same as in Example 1.

[0057] Comparative Example 1

[0058] A composite yttrium oxide ceramic was prepared by referring to the preparation method of Example 1, except that the stabilizer was not added, and the rest of the steps were the same as those of Example 1.

[0059] Comparative Example 2

[0060] A composite yttrium oxide ceramic was prepared by referring to the preparation method of Example 1, except that the mass fraction of the reinforcing phase was changed to 0.5 parts, and the rest remained the same as in Example 1.

[0061] Performance testing:

[0062] 1. Rockwell Hardness: Rockwell hardness of the material (a composite yttria ceramic prepared in the Examples and Comparative Examples) was measured in accordance with GB / T 230.1-2009. The data are shown in Table 2.

[0063] 2. Fracture Strength: The fracture strength of the material (a composite yttrium oxide ceramic prepared in the Examples and Comparative Examples) was measured using a universal testing machine. The data is shown in Table 2.

[0064] Table 2. Rockwell hardness and fracture strength data of a composite yttrium oxide ceramic prepared in the embodiment and comparative example.

[0065] Rockwell hardness HRB Breaking strength N Example 1 88 1950 Example 2 87 1880 Example 3 89 1020 Example 4 86 1800 Comparative Example 1 72 1150 Comparative Example 2 68 1250

[0066] Compared with the comparative example, the composite yttrium oxide yttrium ceramics prepared in all examples showed a higher performance trend in Rockwell hardness and fracture strength. The addition of the stabilizer and reinforcing phase of the present invention can effectively improve the mechanical properties of the ceramics. Among them, the differences between the examples show that different stabilizer types have an impact on the performance, but overall the hardness and strength of the examples are better than the comparative example, highlighting the key role of stabilizers in optimizing ceramic structure.

[0067] While embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions, and variations may be made to these embodiments without departing from the principles and spirit of the invention, and that the scope of the invention is defined by the appended claims and their equivalents.

Claims

1. A method for preparing a composite yttrium oxide ceramic, characterized in that: The following steps are involved: S1. Add yttrium oxide powder, reinforcing phase, dispersion medium, and stabilizer to a ball mill and mix at ≤50°C for 2-8 hours; S2. Add a low-temperature binder and stir the reaction in a 60-90 ° C water bath for 1-3 hours to form a slurry; S3. The slurry is injected into the mold and pressed under a pressure of 0.5-5MPa; S4. The formed body is aged for 12-24 hours at a humidity of 60-80%; S5 gradient drying at 80-150 ℃ for 12-48 hours to obtain a composite yttrium oxide ceramic; The composite yttrium oxide ceramic is made of the following raw materials in parts by mass: 100 parts of yttrium oxide powder, 5-30 parts of reinforcing phase, 10-50 parts of low-temperature binder, 20-80 parts of dispersion medium, and 1-5 parts of stabilizer; The stabilizer has a structure shown in Formula 1: Formula 1; The R1 is selected from: methyl, ethyl, tert-butyl, methoxy; The reinforcing phase is at least one of zirconium oxide and silicon carbide, and has a particle size of 50-500 nm; The low-temperature binder is silica sol with a solid content of 30wt%; The S2 stirring reaction is carried out in a closed container under a nitrogen atmosphere, and the pH value of the solution is controlled to be 4-6; The S3 compression molding adopts isostatic pressing or molding, and the holding time is 10-30 minutes.

2. The method for preparing a composite yttrium oxide ceramic according to claim 1, wherein: The dispersion medium is at least one of deionized water, anhydrous ethanol or acetone.

3. The method for preparing a composite yttrium oxide ceramic according to claim 1, wherein: The S5 gradient drying is divided into three stages: constant temperature drying at 80°C ± 5°C for 4-8 hours; constant temperature drying at 100°C ± 5°C for 4-8 hours; and constant temperature drying at 120-150°C until constant weight is reached.

4. The method for preparing a composite yttrium oxide ceramic according to claim 1, wherein: The S1 ball mill uses zirconia grinding balls with a ball-to-material ratio of (2-5):1 and a rotation speed of 200-400 rpm.

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