High-temperature-resistant black pigment for advanced ceramics, preparation method and application thereof

Abstract

The present application relates to the field of ceramics, and particularly to a high-temperature-resistant black colorant suitable for advanced ceramics, a preparation method and applications thereof, wherein the components of the high-temperature-resistant black colorant include, by mass ratio, 15-25% of Co3O4, 8-15% of Cr2O3, 2-5% of MnO2, 3-8% of SiO2, and 40-60% of Al2O3. The present application realizes the thermal expansion coefficient coordination of the colorant and the alumina matrix by introducing a combination of transition metal oxides matching the alumina lattice, thereby inhibiting cracking or peeling caused by interface stress. A composite doping strategy is adopted to make coloring ions (such as Co 2+ , Cr 3+ ) enter the interstitial space of the alumina lattice to form a stable solid solution structure, thereby significantly improving the color stability at high temperatures. Wet ball milling combined with surface modification is used to ensure uniform dispersion of the colorant particles in the alumina slurry and avoid color spot defects caused by agglomeration.

Description

Technical Field

[0001] This invention relates to the field of ceramic materials technology, and in particular to a high-temperature resistant black pigment suitable for advanced ceramics, its preparation method, and its application. Background Technology

[0002] Alumina ceramics are widely used in high-precision fields such as electronic devices, aerospace components, and medical implants due to their excellent mechanical strength, insulation, and corrosion resistance. However, traditional alumina ceramics are mostly white or off-white, which limits their aesthetic design and functional applications in certain scenarios.

[0003] Patent CN117264440A discloses a process for manufacturing a black pigment for high-temperature resistant alumina and zirconia ceramics. The raw materials include iron oxide (20-30 parts), cobalt oxide (20-25 parts), and manganese oxide (20-40 parts), with an alumina-silicon oxide-titanium oxide flux (mass ratio 6:15:5). Firing is performed in an oxidizing atmosphere (maximum 1280℃, held for 4 hours). This technology does not consider the lattice compatibility between the pigment and the alumina matrix, and the difference in thermal expansion coefficients is not controlled, leading to interface cracking in the ceramic after high-temperature sintering. Furthermore, the solid-phase mixing-high-temperature calcination process causes pigment particles to easily agglomerate in the alumina slurry, resulting in color spot defects in the final product. Patent CN113800905A discloses a method for preparing a black pigment for nano-zirconia ceramics, using co-precipitation of metal salts such as cobalt, chromium, aluminum, and iron to prepare a precursor, followed by calcination at 600-800℃ to obtain a spinel-structured pigment. This technology is specifically designed for zirconia ceramics. However, the lattice compatibility between the colorant and the alumina matrix is ​​poor (zirconia is cubic / monoclinic, while alumina is hexagonal). When applied to alumina ceramics, it easily causes interfacial reactions, resulting in a flexural strength loss rate >15%. Furthermore, without surface modification, the colorant has poor dispersion in the alumina slurry, and at temperatures above 1300℃, coloring ions (such as Fe) are difficult to disperse. 3+ It is easy to precipitate, resulting in a "black with a reddish tinge" phenomenon;

[0004] Existing technologies either neglect the lattice compatibility between the pigment and the alumina matrix, fail to address the issues of color stability and particle dispersion at high temperatures, or cannot simultaneously achieve biocompatibility and mechanical properties. Therefore, developing a high-temperature resistant black pigment specifically designed for alumina ceramics, possessing high-temperature stability, matrix compatibility, and uniform coloring, has become a pressing technical challenge in this field. Summary of the Invention

[0005] In view of this, the purpose of this invention is to propose a high-temperature resistant black pigment suitable for advanced ceramics, its preparation method and its application, so as to solve the problems of existing ceramic colorants that are prone to fading, crystallization or failure due to reaction with alumina matrix during high-temperature sintering, as well as particle agglomeration, interface cracking and poor functional compatibility.

[0006] One aspect of the present invention provides a high-temperature resistant black pigment suitable for advanced ceramics, wherein the components, by mass ratio, comprise 15-25% Co3O4, 8-15% Cr2O3, 2-5% MnO2, 3-8% SiO2, and 40-60% Al2O3, and the difference in the coefficient of thermal expansion between the pigment and the alumina matrix in the range of 25-1400℃ is ≤5×10⁻⁶. -6 At / ℃, it forms a stable solid solution structure.

[0007] Optionally, the Al2O3 has an α-phase crystal structure and a specific surface area ≥15m² / g.

[0008] Optionally, each component is a powder, and the surface of the particles in the powder is coated with a Y2O3 nano-layer, with the coating amount accounting for 0.5-2% of the total mass of the pigment.

[0009] Another aspect of the present invention provides a method for preparing a high-temperature resistant black pigment suitable for advanced ceramics, comprising the following steps:

[0010] Step 1: The raw materials of each component are nano-sized by wet ball milling to achieve a particle size distribution of D. 50 ≤100nm;

[0011] Step 2: Coat the surface of the raw materials by rare earth salt precipitation to obtain a suspension. Adjust the pH of the ball-milled mixture to 8-10, stir at 300-500 rpm, slowly add rare earth salt solution, and age for 24 hours.

[0012] Step 3: After spray drying, the suspension is used to obtain spherical agglomerates. Pressure spray drying is adopted with an inlet air temperature of 280℃, an outlet air temperature of 160℃, and an atomization pressure of 0.3-0.5MPa.

[0013] Step four: The spherical agglomerates undergo two-stage sintering: first, the binder is removed in air at 750-820℃ for 2 hours, and then the main sintering is carried out in an inert gas atmosphere at 1400-1450℃ for 3 hours. After cooling in the furnace, the agglomerates are passed through a 500-mesh sieve to obtain the finished colorant.

[0014] Furthermore, the rare earth salt used in step three is a yttrium nitrate or yttrium sulfate solution with a concentration of 0.05-0.2 mol / L.

[0015] Furthermore, during ball milling in step one, the raw materials, balls, and ethanol are mixed in a ratio of 1:3:5, the ball milling speed is 300 rpm, the ball milling time is 12 h, and ammonium polyacrylate is added as a dispersant.

[0016] Another aspect of the present invention proposes an application of a high-temperature resistant black pigment suitable for advanced ceramics, wherein the high-temperature resistant black pigment is applied to alumina ceramic products and the addition amount is 5-15% of the mass of the alumina ceramic product body.

[0017] Furthermore, alumina ceramic products are used for electron tube housings, medical joints, or precision bearing components.

[0018] The beneficial effects of this invention are as follows: By introducing a combination of transition metal oxides that match the alumina lattice, this invention achieves synergy between the thermal expansion coefficients of the colorant and the alumina matrix, suppressing cracking or peeling caused by interfacial stress; and by employing a composite doping strategy, it enables coloring ions (such as Co) to... 2+ Cr 3+ It enters the interstitial spaces of the alumina lattice, forming a stable solid solution structure, which significantly improves the color stability at high temperatures; through wet ball milling combined with surface modification, it ensures that the pigment particles are uniformly dispersed in the alumina slurry, avoiding color spot defects caused by agglomeration;

[0019] By optimizing the doping ratio of Co3O4 (15-25%) and Cr2O3 (8-15%), and combining the high specific surface area of ​​α-Al2O3, a good compatibility with the alumina matrix is ​​achieved while ensuring a deep black coloring effect (color L*≤15.5 at 1300℃).

[0020] After the finished pigment is kept at 1400℃ for 20 hours, the ΔE color difference is ≤2.5, the flexural strength loss rate is <9%, and the dielectric constant fluctuation is ≤±2.0%, which is far superior to ordinary pigments in the industry (ΔE color difference >8 and flexural strength loss rate >15% at 1400℃). Detailed Implementation

[0021] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to specific embodiments.

[0022] Example 1 Raw material preparation

[0023] Prepare 67 parts of α-Al2O3 with a purity of 99.7% and a particle size of 0.5μm as the main substrate; 15 parts of Co3O4 with an analytical purity to provide the basic black color; 10 parts of nano-sized Cr2O3 for auxiliary coloring, enhancing red light absorption and deepening the black; 3 parts of chemically pure MnO2 for adjusting the hue and eliminating yellow edges; and 5 parts of SiO2 as a glass phase promoter to improve sintering performance.

[0024] Nano-sizing treatment: The raw materials were fed into a planetary ball mill for wet ball milling at a ratio of material:balls:ethanol = 1:3:5, with ammonium polyacrylate dispersant added simultaneously. The milling was carried out at 300 rpm for 12 hours to obtain a submicron-sized mixed slurry. The particle size distribution of each raw material was D. 50 =85nm;

[0025] Precipitation coating: The surface coating treatment is carried out by rare earth salt precipitation. The pH value of the mixed slurry is adjusted to 9, and the mixture is stirred at 400 rpm. A Y2(SO4)3 solution with a concentration of 0.1 mol / L is slowly added dropwise. The mixture is aged for 24 hours under stirring conditions to allow the Y2O3 nanolayer to be uniformly deposited on the surface of the raw material particles in the mixed slurry. The nanolayer thickness is 5-8 nm, resulting in a suspension.

[0026] Spray granulation: The suspension is subjected to pressure spray drying (inlet air 280℃, outlet air 160℃, atomization pressure 0.4MPa) to obtain spherical agglomerates with good flowability;

[0027] Gradient sintering: First, remove the binder in a debinding furnace at 800℃ for 2 hours, then transfer it to a muffle furnace and hold it at 1450℃ for 3 hours, and then cool it with the furnace.

[0028] Grading and screening: passing through a 500-mesh sieve to obtain particle size distribution D. 10 =1.2μm, D 90 Finished colorant with a particle size of 4.8μm.

[0029] Example 2 Raw material preparation

[0030] Prepare 54 portions of α-Al₂O₃ with a purity of 99.7% and a particle size of 0.5 μm (specific surface area 15 m²). 2 / g); 25 parts of analytical grade Co3O4; 8 parts of nano-sized Cr2O3; 5 parts of chemically pure MnO2; 8 parts of SiO2;

[0031] Nano-sizing treatment: The raw materials were fed into a planetary ball mill for wet ball milling at a ratio of material:balls:ethanol = 1:3:5, with ammonium polyacrylate dispersant added simultaneously. The milling was carried out at 300 rpm for 12 hours to obtain a submicron-sized mixed slurry. The particle size distribution of each raw material was D. 50 =92nm;

[0032] Precipitation coating: The surface coating treatment is carried out by rare earth salt precipitation. The pH value of the mixed slurry is adjusted to 8, and the mixture is stirred at 350 rpm. A Y(NO3)3 solution with a concentration of 0.2 mol / L is slowly added dropwise. The mixture is aged for 24 hours under stirring conditions to allow the Y2O3 nanolayer to be uniformly deposited on the surface of the raw material particles in the mixed slurry. The nanolayer thickness is 7-10 nm, and a suspension is obtained.

[0033] Spray granulation: The suspension is subjected to pressure spray drying (inlet air 280℃, outlet air 160℃, atomization pressure 0.3MPa) to obtain spherical agglomerates with good flowability;

[0034] Gradient sintering: First, remove the binder in a debinding furnace at 800℃ for 2 hours, then transfer it to a muffle furnace and hold it at 1450℃ for 3 hours, and then cool it with the furnace.

[0035] Grading and screening: passing through a 500-mesh sieve to obtain particle size distribution D. 10 =1.2μm, D 90 Finished colorant with a particle size of 4.8μm.

[0036] Example 3 Raw Material Preparation

[0037] Prepare 65 parts of α-Al₂O₃ powder with a purity of 99.7% and a specific surface area ≥18 m² / g, 20 parts of analytical grade Co₃O₄, 8 parts of nano-Cr₂O₃, 4 parts of chemically pure MnO₂, and 3 parts of SiO₂. Nano-sizing treatment: Same as the wet ball milling process in Example 1, to obtain D… 50 =78nm mixed slurry. Precipitation coating: Adjust the pH of the mixed slurry to 10, stir at 500 rpm, and add 0.05 mol / L Y(NO3)3 solution dropwise, controlling the Y2O3 nanolayer coating amount to 0.5% of the total mass of the pigment, with a nanolayer thickness of 5 nm, to obtain a suspension. Spray granulation: Under the same conditions as in Example 1, spherical agglomerates are obtained. Gradient sintering: The two-stage sintering process of Example 1 is used (800℃ debinding, 1450℃ main sintering). Grading and screening: Pass through a 500-mesh sieve to obtain the finished pigment.

[0038] Example 4 Raw material preparation

[0039] Prepare 50 parts of α-Al₂O₃ powder with a purity of 99.7% and a specific surface area ≥20 m² / g, 25 parts of analytical grade Co₃O₄, 15 parts of nano-Cr₂O₃, 2 parts of chemically pure MnO₂, and 8 parts of SiO₂. Nano-sizing treatment: Same as the wet ball milling process in Example 1, to obtain D… 50 =95nm mixed slurry. Precipitation coating: 0.2mol / LY2(SO4)3 solution was added dropwise, and the Y2O3 nanolayer coating amount was controlled to be 2.0% of the total mass of the pigment to obtain a suspension. Spray granulation: under the same conditions as in Example 1, spherical agglomerates were obtained. Gradient sintering: the two-stage sintering process of Example 1 was used (750℃ debinding, 1400℃ main sintering). Grading and screening: the pigment was passed through a 500-mesh sieve to obtain the finished pigment.

[0040] Example 5 Raw material preparation

[0041] Prepare 57 parts of α-Al₂O₃ powder with a purity of 99.7% and a specific surface area ≥16 m² / g, 18 parts of analytical grade Co₃O₄, 12 parts of nano-Cr₂O₃, 5 parts of chemically pure MnO₂, and 8 parts of SiO₂. Nano-sizing treatment: Same as the wet ball milling process in Example 1, to obtain D… 50 =88nm mixed slurry. Precipitation coating: Adjust the pH of the mixed slurry to 8.5, stir at 380 rpm, and add 0.15 mol / L Y(NO3)3 solution dropwise, controlling the Y2O3 nanolayer coating amount to 1.2% of the total mass of the pigment, with a nanolayer thickness of 8 nm, to obtain a suspension. Spray granulation: Under the same conditions as in Example 1, spherical agglomerates are obtained. Gradient sintering: The two-stage sintering process of Example 1 is used (820℃ debinding, 1425℃ main sintering). Grading and screening: Pass through a 500-mesh sieve to obtain the finished pigment.

[0042] Example 6 Raw material preparation

[0043] Prepare 59.5 parts of α-Al₂O₃ powder with a purity of 99.7% and a specific surface area ≥16 m² / g, 20 parts of analytical grade Co₃O₄, 11.5 parts of nano-Cr₂O₃, 3.5 parts of chemically pure MnO₂, and 5.5 parts of SiO₂. Nano-sizing treatment: Same as the wet ball milling process in Example 1, to obtain D… 50 =82nm mixed slurry. Precipitation coating: Adjust the pH of the mixed slurry to 9, stir at 420 rpm, and add 0.15 mol / L Y(NO3)3 solution dropwise, controlling the Y2O3 nanolayer coating amount to 1.2% of the total mass of the pigment, with a nanolayer thickness of 7 nm, to obtain a suspension. Spray granulation: Under the same conditions as in Example 1, spherical agglomerates are obtained. Gradient sintering: The two-stage sintering process of Example 1 is used (820℃ debinding, 1425℃ main sintering). Grading and screening: Pass through a 500-mesh sieve to obtain the finished pigment.

[0044] Performance testing

[0045] The finished pigments obtained in Examples 1-6 and common industry pigments were tested according to the following standards:

[0046] Colorimetric L* and ΔE color difference were tested using a spectrophotometer according to GB / T11942-2022 "Method for Measurement of Color Difference in Colored Building Materials"; flexural strength loss rate was tested according to GB / T6569-2006 "Test Method for Bending Strength of Fine Ceramics"; dielectric properties were tested using a dielectric spectrometer at 1MHz and 1400℃ for dielectric constant and dielectric loss; thermal expansion coefficient was tested using a thermal expansion meter within the range of 25-1400℃; long-term high-temperature stability was tested by measuring ΔE color difference after holding at 1400℃ for 20 hours. The test results are shown in Table 1.

[0047] Table 1

[0048]

[0049] According to the test results, the high-temperature resistant black pigment proposed in this invention, suitable for advanced ceramics, can maintain stable color stability, good matrix compatibility, and excellent comprehensive performance at high temperatures.

[0050] The black pigment proposed in this invention can also be used in the production of electron tube shells, medical joints, and precision bearing components. The dielectric constant of the pigment fluctuates by ±0.8% at 1400℃ and 1MHz, without affecting the insulation properties of alumina ceramics. When applied to medical joints, the pigment has a cytotoxicity level ≤1 and a hemolysis rate ≤2%, meeting the biocompatibility requirements for medical implants. When applied to precision bearing components, the pigment results in a wear amount of ≤0.02mm³ / (N·m) and a bending strength loss rate of <3% for ceramic products, ensuring stable mechanical properties.

[0051] Those skilled in the art should understand that the discussion of any of the above embodiments is merely exemplary and is not intended to imply that the scope of the invention (including the claims) is limited to these examples; within the framework of the invention, the technical features of the above embodiments or different embodiments can also be combined, the steps can be implemented in any order, and there are many other variations of the different aspects of the invention as described above, which are not provided in the details for the sake of brevity.

[0052] This invention is intended to cover all such substitutions, modifications, and variations that fall within the broad scope of the appended claims. Therefore, any omissions, modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this invention should be included within the scope of protection of this invention.

Claims

1. A high-temperature resistant black pigment suitable for advanced ceramics, characterized in that, The components, by mass ratio, include 15-25% Co3O4, 8-15% Cr2O3, 2-5% MnO2, 3-8% SiO2, and 40-60% Al2O3. The difference in the coefficient of thermal expansion between the pigment and the alumina matrix within the temperature range of 25-1400℃ is ≤5×10⁻. 6 At / ℃, it forms a stable solid solution structure.

2. The high-temperature resistant black pigment suitable for advanced ceramics according to claim 1, characterized in that, The Al2O3 has an α-phase crystal structure and a specific surface area ≥15m² / g.

3. The high-temperature resistant black pigment suitable for advanced ceramics according to claim 1, characterized in that, All components are powders, and the surface of the particles in the powder is coated with a Y2O3 nanolayer with a thickness of 5-10 nm and the coating amount accounts for 0.5-2% of the total mass of the pigment.

4. A method for preparing a high-temperature resistant black pigment suitable for advanced ceramics as described in any one of claims 1-3, characterized in that, Includes the following steps: Step 1: The raw materials of each component are nano-sized by wet ball milling to achieve a particle size distribution of D. 50 ≤100nm; Step 2: Coating the surface of the raw materials by rare earth salt precipitation. Adjust the pH of the ball-milled slurry to 8-10, stir at 300-500 rpm, slowly add rare earth salt solution, and age for 24 hours to obtain a suspension. Step 3: After spray drying, the suspension is used to obtain spherical agglomerates. Pressure spray drying is adopted with an inlet air temperature of 280℃, an outlet air temperature of 160℃, and an atomization pressure of 0.3-0.5MPa. Step four: The spherical agglomerates undergo two-stage sintering: first, the binder is removed in air at 750-820℃ for 2 hours, and then the main sintering is carried out in an inert gas atmosphere at 1400-1450℃ for 3 hours. After cooling in the furnace, the agglomerates are passed through a 500-mesh sieve to obtain the finished colorant.

5. The preparation method according to claim 4, characterized in that, The rare earth salt used in step two is a yttrium nitrate or yttrium sulfate solution with a concentration of 0.05-0.2 mol / L.

6. The preparation method according to claim 4, characterized in that, In step one, the balls are mixed in a ratio of 1:3:5 (raw material:balls:ethanol), the ball milling speed is 300 rpm, the ball milling time is 12 h, and ammonium polyacrylate is added as a dispersant.

7. The application of a high-temperature resistant black pigment suitable for advanced ceramics as described in any one of claims 1-4, characterized in that, The high-temperature resistant black pigment is applied to alumina ceramic products, and the amount added is 5-15% of the mass of the alumina ceramic product body.

8. The application of the high-temperature resistant black pigment according to claim 7, characterized in that, The alumina ceramic products include electron tube housings, medical joints, or precision bearing components.

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