A method for preparing high-temperature resistant pigments based on molybdenum trioxide flux volatilization

Abstract

This invention discloses a method for preparing high-temperature resistant pigments based on the volatilization of molybdenum trioxide as a flux in the field of inorganic high-temperature resistant pigment and functional powder preparation. The method uses aluminum hydroxide, aluminum oxide, etc., as aluminum sources, and chromium oxide, iron oxide, titanium oxide, etc., as coloring components. Molybdenum trioxide is introduced as a flux and catalyst. Through mixing, calcination / vaporization, and fine grinding, a high-temperature resistant pigment is obtained, and the catalyst is recovered. During the heating process, molybdenum trioxide forms an intermediate phase with the system components and generates a transient liquid phase, promoting the diffusion, dispersion, and solid solution of metal ions. During calcination, molybdenum trioxide is volatilized and recovered for reuse through forced draft or exhaust ventilation. The prepared solid pigment has a single corundum phase, fine particle size, concentrated particle size distribution, and complete solid solution of the coloring metal, exhibiting good thermal stability. This invention has the advantages of simple operation, strong scalability, and high product quality, making it suitable for industrial applications.

Description

Technical Field

[0001] This invention relates to the field of inorganic high-temperature resistant pigments and functional powders, specifically to a method for preparing high-temperature resistant pigments based on the volatilization of molybdenum trioxide flux. Background Technology

[0002] With the rapid development of precision ceramics, aerospace, new energy, and high-end equipment manufacturing, the performance requirements for high-temperature resistant pigments in industrial systems have upgraded from basic temperature resistance to a comprehensive demand for temperature resistance rating, environmental friendliness, functionalization, and long-term stability. While traditional inorganic high-temperature resistant pigments possess high-temperature resistance (300-1200℃), they suffer from problems such as limited color gamut, heavy metal residues, color shift at high temperatures, and poor interfacial compatibility with substrates, making it difficult to meet the stringent standards of color accuracy and environmental safety in high-end manufacturing. For example, iron oxide black begins to change color above 80℃, and after coating treatment, its temperature resistance only increases to 150℃, gradually turning reddish above that temperature; lead-containing pigments reduce the heat resistance of the coating. Furthermore, cadmium-based, lead-based, and chromium-based pigments may release toxic substances in high-temperature or acidic environments, failing to meet industry standards and safety regulations, and will be gradually phased out.

[0003] While nanoparticle modification can improve pigment dispersibility, it requires complex process control, leading to a surge in production costs. Surface coating can enhance oxidation resistance, but the coating layer is prone to detachment or chemical reaction at high temperatures. Composite pigments improve temperature resistance by introducing other metal ions (such as titanium, manganese, and copper), but may sacrifice tinting strength or environmental friendliness. Currently, the core issue in the field of inorganic high-temperature resistant pigments is the incompatibility between temperature resistance, environmental friendliness, and long-lasting effects. How to prepare a new type of high-temperature resistant, stable, and non-toxic pigment has become an important requirement in high-end manufacturing. Summary of the Invention

[0004] This invention provides a method for preparing high-temperature resistant pigments based on the volatilization of molybdenum trioxide flux. This method can achieve efficient solid solution of coloring metal ions at a relatively low firing temperature, and prepare high-temperature resistant corundum phase solid solution pigments with stable crystal phase, stable color, and appropriate particle size distribution.

[0005] The present invention achieves the above objectives through the following technical solutions: S1. Batching and fine grinding: Weigh the aluminum components, colored metal oxides and molybdenum trioxide flux according to the proportion, mix and fine grind to obtain a mixture. Platinum crucible or silicon carbide crucible is preferred for loading to ensure good chemical stability and corrosion resistance under high temperature conditions. S2. Calcination and solid solution: The mixture is heated to 950-1150°C and calcined for 10-90 min, so that the aluminum component and the colored metal oxide undergo a solid solution reaction in the transient liquid phase environment formed by molybdenum trioxide to form a corundum phase solid solution. S3. Flux volatilization and separation: During the calcination process, a certain negative pressure condition is formed by blowing or exhausting air. Under this condition, the volatilization rate of molybdenum trioxide is accelerated, which is also conducive to inhibiting grain growth and refining the product particle size, so that molybdenum trioxide volatilizes faster and is separated from the solid product. S4. Post-processing: Cool the calcined solid product and then grind it finely to obtain inorganic pigments.

[0006] A further improvement is that the aluminum component is selected from at least one of aluminum hydroxide and aluminum oxide; The coloring metal oxide is selected from at least one of oxides, hydrated oxides, hydroxides, carbonates, or sulfates of chromium, iron, titanium, zirconium, manganese, and cobalt. The purity of the aluminum component, the colored metal oxide, and the molybdenum trioxide is all greater than 99%.

[0007] A further improvement is that the amount of molybdenum trioxide added is 5 wt.% to 60 wt.% of the total mass of the mixture, preferably 50 to 60 wt.%. The molybdenum volatilization rate during the roasting process is not less than 99%; after the roasting flue gas is cooled, solid molybdenum trioxide is precipitated and returned to the S1 cycle for use as a feed ingredient through bag dust collection.

[0008] A further improvement is that, in S3, the blowing speed is 1.5m / min to 7.5m / min, and the blowing time is 20min to 50min, or the exhaust creates a negative pressure of 0.03MPa to 0.09MPa, and the exhaust time is 20min to 30min.

[0009] A further improvement is that the particle size of the finely ground material in S1 meets the following requirement: the proportion of particles with a diameter less than 74 μm is not less than 90%. The heating rate in S2 does not exceed 25°C / min, and the heating and roasting process uses an air atmosphere.

[0010] A further improvement is that the fine grinding in S1 and S4 is carried out by dry ball milling or wet ball milling, with a rotation speed of 150 rpm to 200 rpm and a grinding time of 25 to 35 min; the average particle size of the inorganic pigment obtained after fine grinding is less than 10 μm.

[0011] The present invention also provides a high-temperature resistant corundum solid solution pigment, which is prepared by the above method; the average particle size of the pigment is less than 10 μm, and it does not undergo phase change and maintains color stability in air atmosphere and below 1350℃.

[0012] A further improvement is that the pigment is a corundum solid solution powder; The pigment comprises at least one of the following coloring elements: 0.3–11.0 wt.% Cr, 0.3–7.0 wt.% Fe, 0.05–1.5 wt.% Ti, 0.05–1.5 wt.% Zr, 0.05–3.5 wt.% Mn, and 0.05–3.5 wt.% Co.

[0013] The present invention also provides an application of the above-mentioned high-temperature resistant corundum solid solution pigment in high-temperature coatings, ceramic glazes or refractory materials.

[0014] Compared with the prior art, the present invention has the following advantages: (1) In the traditional solid-phase synthesis of high-temperature resistant pigments, borates, phosphates and other fluxes are often used. However, they will remain in the product at high temperatures, affecting thermal stability or introducing impurities. This invention utilizes the characteristics of MoO3 to flux in the medium temperature range and volatilize and separate in the high temperature range, thereby improving the solid solution efficiency of coloring metal ions and avoiding the problem of pigment high-temperature stability reduction caused by catalyst residue.

[0015] (2) In the traditional scheme, it is usually necessary to obtain a high temperature of >1300°C to obtain a corundum phase with complete solid solution of coloring ions. However, the corundum phase formation temperature of the present invention is reduced to 950-1100°C, which has a significant energy-saving effect. While reducing the reaction temperature by more than 300°C, the solid solution efficiency and phase purity are improved by the liquid phase environment.

[0016] (3) It can achieve multiple hue control of high temperature resistant pigments in the range of light yellow to dark purple.

[0017] (4) The obtained pigment has a concentrated particle size distribution with an average particle size of less than 10 μm, and has good high-temperature stability and chemical stability.

[0018] (5) During the high-temperature volatilization separation process, molybdenum trioxide enters the flue gas system and can be recovered and reused through condensation, dust removal and other methods, so as to realize the recycling of flux, reduce raw material consumption, and have good comprehensive resource utilization value. Attached Figure Description

[0019] Figure 1 This is a schematic diagram of XRD analysis in Embodiment 1 of the present invention; Figure 2 This is a schematic diagram of laser particle size analysis in Embodiment 2 of the present invention; Figure 3 This is a schematic diagram of scanning electron microscopy analysis in Embodiment 3 of the present invention. Detailed Implementation

[0020] The present application will now be described in further detail with reference to the accompanying drawings. It should be noted that the following specific embodiments are only used to further illustrate the present application and should not be construed as limiting the scope of protection of the present application. Those skilled in the art can make some non-essential improvements and adjustments to the present application based on the above application content.

[0021] Example 1 The materials were prepared according to the following ratios: 45 wt.% Al(OH)3, 2.5 wt.% Fe2O3, and 52.5 wt.% MoO3, with 45.00 g of Al(OH)3, 2.50 g of Fe2O3, and 52.50 g of MoO3. The mixture was dry-milled in a ball mill at 180 rpm for 30 min to obtain a mixture with 92% particles smaller than 74 μm. The mixture was then placed in a silicon carbide crucible and heated to 1100°C in a muffle furnace at 10°C / min and held for 60 min. After holding for 20 min, air was blown in for 40 min at a flow rate of 4 m / min. The remaining solid product was cooled and then dry-milled in a ball mill at 180 rpm for 30 min to obtain a yellow pigment.

[0022] Scanning electron microscopy (SEM) analysis showed that the particles had uniform morphology and fine particle size. XRD analysis showed that the diffraction peaks of the synthesized product were completely consistent with the corundum standard card, and no free Fe2O3 was detected, indicating that the product was a single corundum solid solution phase. Figure 1 By calculating the mass difference of molybdenum in the system before and after the reaction, the molybdenum volatilization rate during the calcination process was found to be 99.85%. Laser particle size analysis showed that the pigment particle size was concentrated in the range of 2~9 μm, with an average particle size of about 5.2 μm. Colorimeter analysis showed that the colorimetric values ​​of the synthesized pigment were L* = 93.5, a* = -10.0, and b* = 72.3. After continuous calcination at 1300°C for 6 hours, the colorimetric values ​​changed to L* = 94.1, a* = -10.0, and b* = 72.3, with a color difference ΔE of about 0.6, indicating that it has excellent high-temperature color stability.

[0023] Example 2 A mixture containing 41.5 wt.% Al(OH)3, 3.5 wt.% Cr2O3 and 55 wt.% MoO3 was prepared and dry-milled in a ball mill at 180 rpm for 25 min to obtain a mixture with 91% particles smaller than 74 μm. The mixture was then placed in a silicon carbide crucible and heated to 1050°C in a muffle furnace at 10°C / min and held for 80 min. After holding for 30 min, air was blown in for 50 min at a flow rate of 4.5 m / min. The remaining solid product was cooled and then dry-milled in a ball mill at 180 rpm for 25 min to obtain a purple pigment.

[0024] Scanning electron microscopy analysis showed that the pigment particles were approximately equiaxed, well-dispersed, and without obvious agglomeration. Phase analysis showed that only α-Al₂O₃ corundum phase diffraction peaks were present, and no Cr₂O₃ or other impurity phase peaks were detected. By calculating the mass difference of molybdenum in the system before and after the reaction, the molybdenum volatilization rate during the calcination process was found to be 99.82%. Laser particle size analysis showed that the average particle size of the purple pigment was 5.4 μm. Figure 2 Colorimeter analysis showed that the colorimetric values ​​of the synthetic pigment were L* = 64.9, a* = 26.02, and b* = -27.01. After continuous calcination at 1300°C for 6 hours, the colorimetric values ​​changed to L* = 64.9, a* = 26.0, and b* = -27.0, with a color difference ΔE < 0.1, indicating almost no color change.

[0025] Example 3 A mixture containing 43 wt.% Al(OH)3, 0.5 wt.% Fe2O3, 0.09 wt.% TiO2, and 56.41 wt.% MoO3 was prepared and dry-milled in a ball mill at 180 rpm for 35 min to obtain a mixture with 93% particles smaller than 74 μm. The mixture was then placed in a silicon carbide crucible and heated to 1100°C in a muffle furnace at 10°C / min and held for 50 min. After calcination for 30 min, the mixture was evacuated for 20 min to create a negative pressure environment of 0.07 MPa to separate molybdenum trioxide. The remaining solid product was cooled and dry-milled in a ball mill at 180 rpm for 35 min to obtain a blue pigment.

[0026] Scanning electron microscopy analysis showed that the particles were small and uniformly distributed, with the particle size mainly concentrated in the range of 2–6 μm. Figure 3 Phase analysis showed that the sample was a single α-Al₂O₃ corundum phase; by calculating the mass difference of molybdenum before and after the reaction, the molybdenum volatilization rate during the calcination process was found to be 99.89%; colorimetric analysis showed that the colorimetric values ​​of the synthesized pigment were L* = 50.0, a* = 32.1, and b* = -78.6; after continuous calcination at 1200°C for 5 hours, the colorimetric values ​​changed to L* = 49.79, a* = 32.47, and b* = -78.52, with ΔE approximately 0.23.

[0027] Example 4 A mixture containing 41 wt.% Al(OH)3, 0.8 wt.% CoSO4, 0.2 wt.% TiO2 and 58 wt.% MoO3 was prepared, and the remaining operations were the same as in Example 1. The material was dry-milled in a ball mill at 180 rpm for 30 min to obtain a mixture with 92% particles smaller than 74 μm. The mixture was then placed in a silicon carbide crucible and heated to 1100°C in a muffle furnace at 10°C / min and held for 30 min. Air was then blown in for 50 min at a flow rate of 3.5 m / min. After cooling, the remaining solid product was dry-milled in a ball mill at 180 rpm for 30 min to obtain a pink pigment.

[0028] Scanning electron microscopy analysis showed that the particles were small and uniformly distributed, with the particle size mainly concentrated in the range of 1~8 μm and the average particle size of about 5.1 μm. Phase analysis showed that the sample was a single α-Al2O3 corundum phase. By calculating the mass difference of molybdenum in the system before and after the reaction, the molybdenum volatilization rate during the calcination process was measured to be 99.85%. Colorimetric analysis showed that the colorimetric values ​​of the synthesized pigment were L* = 83.4, a* = 23.9, and b* = 4.2. After continuous calcination at 1200°C for 5 hours, the colorimetric values ​​changed to L* = 82.4, a* = 26.5, and b* = 3.7, with ΔE of about 2.6.

[0029] Example 5 A mixture containing 42 wt.% Al(OH)3, 0.8 wt.% MnO2, 0.2 wt.% TiO2 and 59 wt.% MoO3 was prepared, and the remaining operations were the same as in Example 1, to obtain a blue pigment.

[0030] Scanning electron microscopy analysis showed that the particles were small and uniformly distributed, with the particle size mainly concentrated in the range of 1~9 μm and the average particle size of about 5.2 μm. Phase analysis showed that the sample was a single α-Al2O3 corundum phase. By calculating the mass difference of molybdenum in the system before and after the reaction, the molybdenum volatilization rate during the calcination process was measured to be 99.81%. Colorimetric analysis showed that the colorimetric values ​​of the synthesized pigment were L* = 75.93, a* = -27.69, and b* = -31.92. After continuous calcination at 1250°C for 6 hours, the colorimetric values ​​changed to L* = 75.83, a* = -27.69, and b* = -31.92, with ΔE of about 0.1.

[0031] Example 6 A mixture containing 42 wt.% Al(OH)3, 0.75 wt.% MnO2, 0.15 wt.% ZrO2 and 57.1 wt.% MoO3 was prepared, and the remaining operations were the same as in Example 1, to obtain a blue pigment.

[0032] Scanning electron microscopy analysis showed that the particles were small and uniformly distributed, with the particle size mainly concentrated in the range of 1~9 μm and the average particle size of about 5.2 μm. Phase analysis showed that the sample was a single α-Al2O3 corundum phase. By calculating the mass difference of molybdenum in the system before and after the reaction, the molybdenum volatilization rate during the calcination process was measured to be 99.86%. Colorimetric analysis showed that the colorimetric values ​​of the synthesized pigment were L* = 48.79, a* = 37.47, and b* = -80.52. After continuous calcination at 1250°C for 6 hours, the colorimetric values ​​changed to L* = 47.77, a* = 37.47, and b* = -80.51, with ΔE of about 1.02.

[0033] Comparative Example 1 Molybdenum trioxide was not added during the ingredient preparation process, and the rest of the operation remained the same as in Example 2.

[0034] Phase analysis showed that some θ-Al2O3 was still present and had not been fully converted into α-Al2O3. Laser particle size analysis showed that the particle size distribution range was wide, with obvious coarse particles and an average particle size greater than 20 μm. The particle size uniformity was significantly worse than that of the pigment obtained in the example.

[0035] Comparative Example 2 The roasting temperature was adjusted to 900°C, and the other steps were kept the same as in Example 2.

[0036] Phase analysis showed that some MoO3 remained and did not fully volatilize, making it impossible to obtain a single-phase pigment from this process.

[0037] Comparative Example 3 The amount of Cr2O3 added was 20 wt.%, and the rest of the operation was the same as in Example 2.

[0038] Because of the excessive amount of Cr2O3 incorporated, phase and microscopic analysis showed that some Cr2O3 was still present and locally enriched, making it impossible to obtain a corundum solid solution pigment with a pure phase and stable color.

[0039] Table 1 summarizes the performance data measured for each embodiment and comparative example.

[0040] Table 1: Comprehensive Process Parameters and Performance Data of Examples and Comparative Examples

[0041] Note: The ΔE (color difference) value is calculated by the CIE Lab colorimetric system. ΔE < 2.0 is generally considered to be color change that is difficult for the human eye to perceive.

[0042] Reaction mechanism and process During the heating process of this invention, molybdenum trioxide first reacts with aluminum source and coloring metal oxide to generate molybdate intermediate phase. As the temperature further increases, the molybdate melts and gradually decomposes. The above melting and decomposition process forms a transient liquid phase environment in the system. This liquid phase system greatly reduces the interfacial tension of the system and encapsulates solid particles through wetting, transforming the traditional "solid-solid" diffusion into a highly efficient "solid-liquid-solid" mass transfer mode. This is beneficial for promoting diffusion and mass transfer behavior within the system, enabling the coloring elements to achieve uniform dispersion in the reaction system. During the crystallization process, it works synergistically with the main alumina to form a corundum phase solid solution structure through substitution. At the same time, the aluminum molybdate intermediate phase generated during the reaction can also undergo melting, decomposition, nucleation, and grain growth processes, and recrystallize under high-temperature volatilization conditions to gradually form fine corundum phase alumina powder.

[0043] Within the characteristic temperature range of 950–1100°C, non-corundum phase aluminum sources (such as θ-Al2O3, γ-Al2O3) dissolve and recrystallize in the liquid medium, inducing them to undergo a low-temperature transformation to the (α−Al2O3 corundum phase). At the same time, coloring elements are uniformly dispersed in the liquid phase at the atomic scale and enter the corundum lattice through isomorphic substitution. With the controlled volatilization of MoO3 at the high temperature stage, new crystal nuclei are rapidly precipitated from the supersaturated liquid phase, effectively suppressing the Ostwald ripening process, thereby obtaining fine-grained pigments with a particle size of less than 10 μm and uniform distribution.

[0044] It should be noted that the aluminum source used in the initial stage of the reaction is usually not corundum phase alumina, but has uneven particle size distribution and relatively coarse particles. After the above melting-decomposition-recrystallization process, the alumina crystal form is reconstructed and the grain size is significantly refined, which is beneficial to obtaining a corundum phase solid solution pigment with a uniform structure.

[0045] Color range and particle size characteristics of the present invention: The color of the high-temperature resistant corundum solid solution pigment obtained by this invention is jointly determined by the type of coloring metal ions and their degree of solid solubility in the α-Al₂O₃ lattice; when chromium oxide is used as the coloring component, Cr 3+ Solid solution enters the corundum lattice, occupying Al 3+ The selective absorption of blue-green wavelengths in visible light by electronic transitions at lattice sites gives the pigment a purple to deep purple hue. The color deepens gradually with increasing Cr₂O₃ molar fraction, and further deepens with increasing Fe₂O₃ molar fraction, exhibiting a yellow to yellowish-brown hue. When iron / manganese / cobalt is introduced in combination with titanium / zirconium components, the Fe₂O₃... 2+ / Mn 2+ / Co 2+ -Ti 4+ / Zr 4+The electronic transition characteristics can further enable the control of light blue, dark blue or pink hues; by selecting and combining the types and mass fractions of coloring metal oxides, the method of the present invention can achieve continuous hue control of high-temperature resistant corundum solid solution pigments in the range of light yellow, yellowish brown, orange brown, pink, light blue, dark blue, purple and dark purple, and the color remains stable under high temperature conditions.

[0046] In terms of particle size, molybdenum trioxide forms a transient liquid phase at the intermediate temperature stage, which is conducive to the uniformity of the solid-phase reaction. It completely volatilizes at the high temperature stage and will not cause abnormal grain growth. After conventional pulverization, the resulting pigment has a concentrated particle size distribution with an average particle size of less than 10 μm, making it suitable for use in ceramic glazes, coatings and refractory materials systems.

[0047] In this invention, MoO3 has a triple mechanism of action: (1) As a low-temperature flux, it forms a transient liquid phase in the intermediate temperature stage, which significantly promotes the dissolution, diffusion and solid solution reaction of Al2O3 and coloring metal ions, and improves the dispersion and solid solution efficiency of components; (2) Liquid molybdenum trioxide evaporates rapidly during the blowing or ventilation process, which promotes the rapid precipitation of newly formed corundum solid solution from the liquid phase. Rapid crystallization is beneficial to the refinement of product particles. (3) The initial dissolution effect of liquid molybdenum trioxide and the later volatilization and crystallization effect promote the transformation of alumina into corundum at a lower temperature and accelerate the corundum formation rate.

[0048] Results Analysis Based on the experimental data from the examples and a series of comparative examples, the following conclusions can be drawn: The XRD patterns of all Examples 1-6 showed a single α-Al2O3 phase, and SEM observation showed uniform particle morphology. This directly proves that with MoO3 flux and specific processes, complete solid solution of coloring ions and formation of pure corundum phase can be achieved at a relatively low temperature of 950 to 1100°C. In contrast, Comparative Example 1 (without MoO3) showed an θ-Al2O3 impurity phase, and Comparative Example 3 (with excess Cr2O3) showed a free Cr2O3 phase. This, in turn, confirms the necessity of the technical solution of this invention (using a specific amount of MoO3 and controlling the content of colorant) for obtaining a high-purity phase.

[0049] The average particle size of all products in the examples was around 5 μm and the distribution was concentrated. This was due to the transient liquid phase formed by MoO3 promoting mass transfer and uniform nucleation, and the subsequent volatilization process inhibiting abnormal grain growth. In contrast, Comparative Example 1, which had no liquid phase, had an average particle size of over 20 μm, highlighting the key role of MoO3 in refining the particle size of the products.

[0050] In the examples, the volatilization rate of MoO3 was higher than 99.8%, and it was successfully recovered. This verifies the integrated design of "fluxing-solution-volatilization separation-recycling" of the present invention, which realizes the efficient removal and recycling of flux and solves the environmental and performance hazards of traditional flux residues. Comparative Example 2 showed that incomplete volatilization was caused by insufficient temperature, which further proves that suitable temperature is a prerequisite for achieving this effect.

[0051] By selecting different colorants (Fe, Cr, Co, Mn) and their composites with Ti and Zr, pigments in various shades such as yellow, purple, blue, and pink were successfully prepared. After long-term high-temperature (1200 to 1300°C) treatment, the color difference ΔE of all the pigments in the examples remained at a low level (0.1 to 2.6), which proved that the prepared pigments have strong high-temperature color stability and meet the requirements of high-end high-temperature resistant applications.

[0052] This invention achieves the formation of a pure corundum phase at temperatures far below those of traditional solid-state methods (above 1300°C), accompanied by the complete solid solution of color ions (without free oxide impurities). This demonstrates that the transient liquid phase formed by MoO3 significantly promotes the kinetics of Al2O3 crystal form reconstruction (θ / γ→α) and significantly reduces the concentration of coloring ions (such as Cr). 3+ Fe 3+ The energy barrier for diffusion into the α-Al2O3 lattice.

[0053] The average particle size of the product was effectively controlled at about 5 μm and the distribution was concentrated. This was directly attributed to two key steps: First, the reaction in the liquid phase achieved uniform mixing and nucleation at the molecular / ionic scale, avoiding local inhomogeneity and coarse grains caused by poor contact in traditional solid-phase reactions; Second, the rapid volatilization of MoO3 in the subsequent process forced the new crystal nuclei to precipitate rapidly from the supersaturated liquid phase. This non-equilibrium process effectively suppressed the Ostwald ripening process, thereby effectively preventing grain coarsening and abnormal growth.

[0054] The extremely low high-temperature color difference ΔE value (especially ΔE less than 0.1 in Example 2) indicates that the coloring ions have been deeply dissolved in the octahedral positions of the corundum lattice, and its coordination field environment remains highly stable at high temperatures. This structural stability is the essential reason why the pigment color does not shift at high temperatures, which is different from physical modification methods such as surface coating.

[0055] The results of Comparative Example 1 are in stark contrast to those of Example 2, which not only demonstrates the indispensability of MoO3 as a liquid phase forming agent, but also shows that in the absence of a liquid phase medium to promote mass transfer, bulk diffusion becomes the rate-controlling step, resulting in severely insufficient reaction kinetics at 1050°C, making it impossible to complete the phase transformation and solid solution, and easily leading to sintering densification and abnormal grain growth.

[0056] The presence of residual MoO3 and its derivative impurities in the product of Comparative Example 2 demonstrates that 900°C is below the effective temperature threshold of the process of this invention. At this temperature, the volatility of MoO3 or its molybdate intermediate phase is insufficient, and the liquid phase may have high viscosity and poor fluidity, making it impossible to complete effective material transport and subsequent thorough separation within the set time.

[0057] The presence of free Cr2O3 phase in the product of Comparative Example 3 directly demonstrates that there is a solid solubility limit for the added colorant. When the amount of Cr2O3 added (20 wt.%) far exceeds its solid solubility in α-Al2O3 (3.5 wt.% was fully dissolved in Example 2), the excess Cr... 3+ Unable to enter the crystal lattice, it precipitates as a second phase, disrupting the uniformity of the pigment phase and inevitably leading to color instability.

[0058] The embodiments described above are merely examples of several implementations of the present invention, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the present invention. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these modifications and improvements all fall within the scope of protection of the present invention.

Claims

1. A method for preparing high-temperature resistant pigments based on the volatilization of molybdenum trioxide flux, characterized in that the steps include... include: S1. Batching and fine grinding: Weigh the aluminum components, coloring metal oxides and molybdenum trioxide flux according to the proportion, mix them and grind them finely to obtain a mixture. S2. Calcination and solid solution: The mixture is heated to 950-1150°C and calcined for 10-90 min, so that the aluminum component and the colored metal oxide undergo a solid solution reaction in the transient liquid phase environment formed by molybdenum trioxide to form a corundum phase solid solution. S3. Flux volatilization and separation: During the roasting process, molybdenum trioxide is volatilized and separated from the solid product by means of forced air or exhaust. S4. Post-processing: Cool the calcined solid product and then grind it finely to obtain inorganic pigments.

2. The method for preparing a high-temperature resistant pigment based on the volatilization of molybdenum trioxide flux according to claim 1, characterized in that, The aluminum component is selected from at least one of aluminum hydroxide and aluminum oxide; The coloring metal oxide is selected from at least one of oxides, hydrated oxides, hydroxides, carbonates, or sulfates of chromium, iron, titanium, zirconium, manganese, and cobalt. The purity of the aluminum component, the colored metal oxide, and the molybdenum trioxide is all greater than 99%.

3. The method for preparing a high-temperature resistant pigment based on the volatilization of molybdenum trioxide flux according to claim 1, characterized in that, The amount of molybdenum trioxide added is 5 wt.% to 60 wt.% of the total mass of the mixture; The molybdenum volatilization rate during the roasting process is not less than 99%; after the roasting flue gas is cooled, solid molybdenum trioxide is precipitated and returned to the S1 cycle for use as a feed ingredient through bag dust collection.

4. The method for preparing a high-temperature resistant pigment based on the volatilization of molybdenum trioxide flux according to claim 1, characterized in that, In S3, the blower speed is 1.5m / min to 7.5m / min, and the blower duration is 20min to 50min; or the exhaust system forms a negative pressure of 0.03MPa to 0.09MPa, and the exhaust duration is 20min to 30min.

5. The method for preparing a high-temperature resistant pigment based on the volatilization of molybdenum trioxide flux according to claim 1, characterized in that, The particle size of the finely ground material in S1 meets the following requirement: the proportion of particles with a diameter less than 74 μm is not less than 90%. The heating rate in S2 does not exceed 25°C / min, and the heating and roasting process uses an air atmosphere.

6. The method for preparing a high-temperature resistant pigment based on the volatilization of molybdenum trioxide flux according to claim 5, characterized in that, In S1 and S4, fine grinding is carried out using dry ball milling or wet ball milling, with a rotation speed of 150 rpm to 200 rpm and a grinding time of 25 to 35 min; the average particle size of the inorganic pigment obtained after fine grinding is less than 10 μm.

7. A high-temperature resistant corundum solid solution pigment, characterized in that, Prepared according to the method according to any one of claims 1-6.

8. The high-temperature resistant corundum solid solution pigment according to claim 7, characterized in that, The pigment is corundum solid solution powder; The pigment comprises at least one of the following coloring elements: 0.3–11.0 wt.% Cr, 0.3–7.0 wt.% Fe, 0.05–1.5 wt.% Ti, 0.05–1.5 wt.% Zr, 0.05–3.5 wt.% Mn, and 0.05–3.5 wt.% Co.

9. The high-temperature resistant corundum solid solution pigment according to claim 7 or 8, characterized in that, The average particle size of the pigment is less than 10 μm.

10. The application of a high-temperature resistant corundum solid solution pigment as described in claim 7 or 8 in high-temperature coatings, ceramic glazes or refractory materials.

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