Preparation method of modified molybdenum disilicide infrared radiation powder

Abstract

The invention discloses a preparation method of a modified molybdenum disilicide infrared radiation powder: putting molybdenum disilicide powder into a tubular furnace for high-temperature oxidation under vacuum, and realizing uniform oxidation by controlling the flow rate of air introduced into the tubular furnace; subjecting the oxidized molybdenum disilicide powder to high-temperature treatment in an argon atmosphere to remove volatile oxide MoO3; performing wet chemical coating of silicon dioxide on the powder treated in argon to form a dense glassy oxygen diffusion inhibition layer. By the method of the invention, through vacuum pre-oxidation pretreatment of molybdenum disilicide powder and removal of volatile oxide MoO3 in a high-temperature inert atmosphere, a uniform oxide layer is formed on the surface of molybdenum disilicide particles, which is beneficial to the uniform coating of silicon dioxide, significantly improves the oxidation resistance of molybdenum disilicide, and simultaneously has a high emissivity.

Description

Technical Field

[0001] The present invention relates to a preparation method of modified molybdenum disilicide high-infrared radiation powder, which can significantly improve the infrared emissivity and antioxidant performance of molybdenum disilicide, and belongs to the technical field of high-infrared radiation application of molybdenum disilicide. Background Art

[0002] Molybdenum disilicide is an intermediate phase with the highest silicon content in the Mo-Si binary alloy system. It is a Dalton-type intermetallic compound with a fixed composition, having the dual characteristics of metal and ceramic, and is an excellent high-temperature infrared radiation material. Molybdenum disilicide has a high melting point (2030 °C), a moderate density (6.24 g / cm 3 ), a low coefficient of thermal expansion (8.1×10 -6 K -1), good electrothermal conductivity, a relatively high brittle-ductile transition temperature (1000 °C), and metallic-like soft plasticity above 1000 °C. Molybdenum disilicide is mainly used as heating elements, integrated circuits, high-temperature and high-emissivity materials, and high-temperature structural materials. However, molybdenum disilicide is prone to oxidation reactions in air at 400–700 °C, generating molybdenum trioxide and silicon dioxide, resulting in volume expansion and catastrophic pulverization oxidation (also known as the pesting oxidation phenomenon), which limits its application at high temperatures. To improve the radiation performance and oxidation resistance of molybdenum disilicide bulk, Literature 1 "Lu Q, Chen X, Fan J L. Effect of Nb–Al–SiC elements combined with pre-oxidation treatment on the pesting resistance of MoSi2. Ceramics International, 2019, 45(13):15807-15814." reported that by introducing Nb, Al, SiC, etc. into the matrix to form a composite material, the pesting oxidation phenomenon was improved. Further, by exposing it to air at 1200 °C for oxidation treatment, the pesting oxidation phenomenon was alleviated. The oxide layer formed by the oxidation treatment adhered to the surface of the molybdenum disilicide composite bulk, inhibiting the diffusion of oxygen into the molybdenum disilicide composite, thus playing an antioxidant role. However, this method cannot completely avoid the oxidation pulverization phenomenon of molybdenum disilicide, and it also reduces the flexural strength of the composite material. Literature 2 "Volders C, Reinke P. Reaction pathways in the oxidation and pesting of molybdenum disilicide MoSi2 studied with scanning tunneling microscopy and spectroscopy. Surface Science, 2019, 681:134-142." analyzed the mechanism of "pesting" oxidation of molybdenum disilicide, pointing out that the volume expansion during the oxidation of molybdenum disilicide is due to the presence of pores and grain boundaries in molybdenum disilicide and the further volatilization of MoO3 formed by oxidation to form secondary pores, which is conducive to oxygen diffusion and causes further oxidation.Reference 3 "Feng P, Wang X, He Y, et al. Effect of high-temperature preoxidation treatment on the low-temperature oxidation behavior of a MoSi2-based composite at 500℃[J]. Journal of Alloys & Compounds, 2009, 473(1-2): 185-189." reported that the high-temperature oxidation treatment of MoSi2-based composites at 1400℃ for 1 h can form a SiO2 glass film on the surface of MoSi2 materials. This glass film can prevent the diffusion of oxygen in the air to MoSi2 during the low-temperature oxidation of MoSi2, effectively inhibiting the "pesting" oxidation phenomenon of MoSi2 at 500℃ and significantly improving the low-temperature oxidation resistance of MoSi2. However, this antioxidant method is mainly aimed at dense MoSi2, rather than MoSi2 powder. Reference 4 "A Preparation Method of High-Emissivity Silicon Dioxide-Coated Molybdenum Disilicide Powder with Wide Temperature Range Antioxidation" (ZL 2022 1 0902938.7) discloses a method for coating silicon dioxide on the surface of molybdenum disilicide particles, significantly inhibiting the oxidation plague phenomenon of molybdenum disilicide. However, this method is not very thorough for oxidation protection under high-temperature conditions, and there is still a weight loss phenomenon caused by the volatilization of MoO3 at high temperatures (above 800℃), indicating that the oxidation of molybdenum disilicide still occurs above 800℃. The master's thesis "Preparation and Performance Study of MoSi2-based High-Emissivity Coatings" (Zheng Tian, Shanghai Institute of Technology, March 2023) prepared molybdenum disilicide powder with excellent infrared radiation performance and good antioxidant performance below 800℃ through low-temperature preoxidation (320 - 340℃), high-temperature inert atmosphere treatment (treatment at 1200℃ for 1 h in argon atmosphere), and silica wet chemical coating. However, oxidation still occurs above 800℃. Therefore, developing a modified molybdenum disilicide powder with good high-temperature antioxidant performance (above 800℃) and good infrared radiation performance is of great significance for the application of molybdenum disilicide as a high-infrared radiation component used at high temperatures in air atmosphere. Summary of the Invention

[0003] The technical problem to be solved by the present invention is: how to improve the high-temperature (800 - 1400℃) oxidation resistance of existing molybdenum disilicide.

[0004] To solve the above problems, the present invention provides a preparation method of modified molybdenum disilicide infrared radiation powder, comprising the following steps:

[0005] Step 1): Put molybdenum disilicide powder into a tube furnace. After evacuating the air, heat it up to 1200 °C and keep it warm, and introduce air during the heating and heat preservation processes;

[0006] Step 2): After the heat preservation is completed, introduce argon into the tube furnace until the pressure reaches 1 atmosphere. Under the condition of keeping argon introduced, keep it warm at 1200 °C, and then naturally cool it to room temperature under argon protection;

[0007] Step 3): Mix anhydrous ethanol, ammonia water, and tetrapropylammonium bromide aqueous solution, add the molybdenum disilicide powder obtained in Step 2), first stir magnetically, and then perform ultrasonic treatment to obtain a uniform dispersion A;

[0008] Step 4): Mix tetraethyl orthosilicate and anhydrous ethanol, and stir evenly to obtain solution B;

[0009] Step 5): Put the dispersion A obtained in Step 3) into a 50 ± 5 °C electrothermal constant temperature water bath, stir magnetically, and at the same time drip the solution B obtained in Step 4) into the dispersion A. After the dripping is completed, stop stirring; Centrifuge the obtained dispersion, wash it with deionized water and anhydrous ethanol for multiple times, and then dry it at 105 ± 5 °C;

[0010] Step 6): Heat-treat the sample obtained in Step 5) in air at 1200 ± 5 °C to obtain molybdenum disilicide powder coated with silica.

[0011] Preferably, in Step 1), the pressure in the tube furnace is 500 - 1500 Pa; the heating rate of the tube furnace is 8 °C / min, and the heat preservation time at 1200 °C is 45 - 120 min; the air inlet flow rate is 450 - 850 mL / h.

[0012] Preferably, in Step 2), the inlet flow rate of argon is 600 - 900 mL / h, and the heat preservation time at 1200 °C is 60 - 180 min.

[0013] Preferably, in Step 3), the mass concentration of ammonia water is 25 - 28%, and the mass concentration of tetrapropylammonium bromide aqueous solution is 30%; the ratio of molybdenum disilicide powder, anhydrous ethanol, ammonia water, and tetrapropylammonium bromide aqueous solution is 5 - 15 g: 100 - 300 mL: 6 - 12 mL: 10 - 30 mL.

[0014] More preferably, in Step 3), the ratio of molybdenum disilicide powder, anhydrous ethanol, ammonia water, and tetrapropylammonium bromide aqueous solution is 5 g: 150 mL: 8 mL: 15 mL.

[0015] Preferably, in Step 4), the ratio of tetraethyl orthosilicate to anhydrous ethanol is 10 - 25 g: 30 - 40 mL. [[ID= thirty-two ]]

[0016] More preferably, in the step 4), the ratio of tetraethyl orthosilicate to absolute ethanol is 15 g: 35 mL.

[0017] Preferably, in the step 5), the weight ratio of molybdenum disilicide to tetraethyl orthosilicate is 1:3 - 1:5; the magnetic stirring speed is 650 revolutions per minute; the dropping rate of solution B is 1 mL per 1 - 5 min.

[0018] More preferably, in the step 5), the weight ratio of molybdenum disilicide to tetraethyl orthosilicate is 1:3; the dropping rate of solution B is 1 mL per 3 min.

[0019] Preferably, in the step 5), during washing, the ratio of deionized water or absolute ethanol to molybdenum disilicide powder is 10 mL: 1 g, and the washing time for each time is 30 min.

[0020] Compared with the prior art, the present invention has the following beneficial effects:

[0021] 1) The present invention controls the oxidation rate by controlling the oxidation pressure and the flow rate of the introduced air, which is beneficial to realizing the uniform oxidation of molybdenum disilicide. Through the high-temperature inert atmosphere treatment at 1200 °C, MoO3 generated by oxidation is volatilized and removed, and a uniform silica layer is formed on the surface of molybdenum disilicide. Although the thickness of the formed uniform silica protective layer is not enough to prevent the high-temperature diffusion of oxygen, this uniform silica layer is beneficial to the subsequent uniform thickening of the silica protective layer by the wet chemical method. For the molybdenum disilicide powder treated by low-pressure oxidation and high-temperature treatment, using tetraethyl orthosilicate as the precursor and tetrapropylammonium bromide as the electrostatic adsorbent, the thickness and uniformity of the silica coating layer on the surface of molybdenum disilicide particles are increased by self-assembly through electrostatic interaction. Finally, through heat treatment in air at a high temperature (1200 °C), the silica coating layer is softened to form a glassy dense protective layer, which inhibits the diffusion of oxygen to molybdenum disilicide, and completely avoids the pesting oxidation of molybdenum disilicide in air at 400 - 700 °C and the high-temperature oxidation at 800 - 1400 °C.

[0022] 2) Through the low-pressure oxidation treatment of the present invention, before coating molybdenum disilicide with silica, a uniform oxide layer is pre-formed on the surface of molybdenum disilicide particles. After the negatively charged surface formed by the oxide layer in an alkaline condition adsorbs tetrapropylammonium bromide with double positive charges, it becomes a positively charged surface, and adsorbs the silica nanoparticles generated by the hydrolysis of tetraethyl orthosilicate with negative charges after alkalization, so that the silica nanoparticles are deposited on the surface of molybdenum disilicide particles. The low-pressure oxidation treatment avoids the surface charge inhomogeneity during silica coating, improves the coating uniformity, and further improves the antioxidant performance of molybdenum disilicide.

[0023] 3) Through the heat treatment under a high-temperature inert atmosphere in step 2) of the present invention, MoO3 formed in step 1) volatilizes, and the subsequent silica coating fills the pores formed by the volatilization of MoO3, further preventing oxygen from diffusing through the pores and reacting with molybdenum disilicide.

[0024] Compared with untreated molybdenum disilicide powder, the modified molybdenum disilicide powder prepared by the present invention has excellent infrared radiation performance and completely inhibits the oxidation of molybdenum disilicide in the entire temperature range from room temperature to 1400 °C. Detailed implementation mode

[0025] To make the present invention more obvious and understandable, the following is a detailed description with preferred embodiments.

[0026] Measurement of emissivity: After pressing the pure powder of the sample into a tablet, the change pattern of reflectivity with wavelength in the wavelength range of 200 - 2500 nm is measured on a Japan - Shimadzu - UV - 3600pLus in diffuse reflection mode. Since the sample has no transmission, emissivity = (1 - reflectivity) / 100.

[0027] Evaluation of antioxidant performance: Accurately weigh about 10 mg of the sample, and on a NETZSCH STA 449F3 thermal analyzer, in an air atmosphere, heat from 27 °C to 1400 °C at a heating rate of 10 °C / min to obtain a thermogravimetric curve, that is, the curve of the sample weight change with temperature. Read the weight change of the sample in different temperature ranges from the curve to judge its antioxidant performance.

[0028] Example 1

[0029] A preparation method of a modified molybdenum disilicide high-infrared radiation powder:

[0030] ① Put 10 g of molybdenum disilicide powder with an average particle size of 1 μm into a tubular furnace, evacuate to a pressure of 500 Pa in the tubular furnace, heat up to 1200 °C at a heating rate of 8 °C / min and hold for 60 min. During the heating and holding process, introduce air at a flow rate of 450 mL / h. After oxidation, the weight increases by 9.6 g, and the weight gain rate is 9.6%.

[0031] ② After the holding time in step ① ends, introduce argon to 1 atmosphere, hold at 1200 °C for 60 min under an argon flow rate of 600 mL / h, and then naturally cool to room temperature under argon protection;

[0032] ③ Place anhydrous ethanol (140 mL), ammonia water (8 mL), and tetrapropylammonium bromide aqueous solution (15 mL) into a conical flask and mix them into a solution. Add 5 g of the molybdenum disilicide powder obtained in step ②, first stir magnetically for 1 h, and then perform ultrasonic treatment for 0.5 h to obtain a uniform dispersion A;

[0033] ④ Mix tetraethyl orthosilicate (15 g) and absolute ethanol (30 mL), and stir evenly to obtain solution B;

[0034] ⑤ Put the dispersion A obtained in step ③ into an electrothermal constant temperature water bath at 50°C ± 5°C, carry out magnetic stirring, and at the same time drop the solution B obtained in step ④ into the dispersion A, dropping 1 mL every 3 min. After the dropping is completed, stop stirring;

[0035] ⑥ Use a centrifuge to centrifuge the dispersion obtained in step ⑤, wash it 3 times with deionized water and absolute ethanol respectively, and then dry it at 105°C for 24 h;

[0036] ⑦ Heat-treat the sample obtained in step ⑥ in air at 1200°C ± 5°C for 1 h to obtain molybdenum disilicide powder coated with silica.

[0037] Example 2

[0038] A preparation method of modified molybdenum disilicide high-infrared radiation powder:

[0039] ① Put 10 g of molybdenum disilicide powder with an average particle size of 1 micron into a tubular furnace, evacuate to a pressure of 1000 Pa in the tubular furnace, heat it at a heating rate of 8°C / min to 1200°C and hold for 60 min. During the heating and holding process, introduce air at a flow rate of 590 mL / h, and the weight gain after oxidation is 12.6 g, and the weight gain rate is 12.6%;

[0040] ② After the holding time in step ① ends, introduce argon to 1 atmospheric pressure, hold at 1200°C for 90 min under an argon flow rate of 700 mL / h, and then naturally cool to room temperature under argon protection;

[0041] ③ Put absolute ethanol (150 mL), ammonia water (8 mL), and tetrapropylammonium bromide aqueous solution (15 mL) into a conical flask and mix them into a solution. Add 5 g of the molybdenum disilicide powder obtained in step ②, first stir magnetically for 1 h, and then perform ultrasonic treatment for 0.5 h to obtain a uniform dispersion A;

[0042] ④ Mix tetraethyl orthosilicate (15 g) and absolute ethanol (35 mL), and stir evenly to obtain solution B;

[0043] ⑤ Put the dispersion A obtained in step ③ into an electrothermal constant temperature water bath at 50°C ± 5°C, carry out magnetic stirring, and at the same time drop the solution B obtained in step ④ into the dispersion A, dropping 1 mL every 3 min. After the dropping is completed, stop stirring;

[0044] ⑥ Use a centrifuge to centrifuge the dispersion obtained in step ⑤, wash it 3 times with deionized water and absolute ethanol respectively, and then dry it at 105°C for 24 h;

[0045] ⑦ Heat-treat the sample obtained in step ⑥ in air at 1200 ± 5 °C for 1 h to obtain molybdenum disilicide powder coated with silica.

[0046] Example 3

[0047] A preparation method of modified molybdenum disilicide high-infrared radiation powder:

[0048] ① Put 10 g of molybdenum disilicide powder with an average particle size of 1 μm into a tubular furnace, evacuate to a pressure of 1500 Pa in the tubular furnace, heat up to 1200 °C at a heating rate of 8 °C / min and hold for 90 min, and introduce air at a flow rate of 810 mL / h during heating and holding. The weight increases by 19.7 g after oxidation, and the weight gain rate is 19.7%;

[0049] ② After the holding time in step ① ends, introduce argon to 1 atmosphere, hold at 1200 °C for 120 min under an argon flow rate of 700 mL / h, and then naturally cool to room temperature under argon protection;

[0050] ③ Place anhydrous ethanol (200 mL), ammonia water (10 mL), and tetrapropylammonium bromide aqueous solution (20 mL) in a conical flask and mix them into a solution. Add 10 g of the molybdenum disilicide powder obtained in step ②, stir magnetically for 1 h first, and then perform ultrasonic treatment for 0.5 h to obtain a uniform dispersion A;

[0051] ④ Mix tetraethyl orthosilicate (20 g) and anhydrous ethanol (40 mL), and stir evenly to obtain solution B;

[0052] ⑤ Put the dispersion A obtained in step ③ into an electrothermal constant temperature water bath at 50 °C ± 5 °C, perform magnetic stirring, and at the same time drop the solution B obtained in step ④ into the dispersion A at a rate of 1 mL every 4 min. After the dropping is completed, stop stirring;

[0053] ⑥ Centrifuge and separate the dispersion obtained in step ⑤, wash it 3 times with deionized water and anhydrous ethanol respectively, and then dry it at 105 °C for 24 h;

[0054] ⑦ Heat-treat the sample obtained in step ⑥ in air at 1200 ± 5 °C for 1 h to obtain molybdenum disilicide powder coated with silica.

[0055] Example 4

[0056] A preparation method of modified molybdenum disilicide high-infrared radiation powder:

[0057] ① Put 10 g of molybdenum disilicide powder with an average particle size of 1 micron into a tube furnace, evacuate to a pressure of 1000 Pa in the tube furnace, heat it up to 1200 °C at a heating rate of 8 °C / min and hold for 120 min. During the heating and holding process, introduce air at a flow rate of 850 mL / h. After oxidation, the weight increases by 23.1 g, and the weight gain rate is 23.1%;

[0058] ② After the holding time in step ① ends, introduce argon to 1 atmosphere, hold at 1200 °C for 180 min under an argon flow rate of 900 mL / h, and then naturally cool to room temperature under argon protection;

[0059] ③ Place anhydrous ethanol (300 mL), ammonia water (12 mL), and tetrapropylammonium bromide aqueous solution (30 mL) into a conical flask and mix them into a solution. Add 15 g of the molybdenum disilicide powder obtained in step ②, first stir magnetically for 1 h, and then perform ultrasonic treatment for 0.5 h to obtain a uniform dispersion A;

[0060] ④ Mix tetraethyl orthosilicate (25 g) and anhydrous ethanol (40 mL), and stir evenly to obtain solution B;

[0061] ⑤ Place the dispersion A obtained in step ③ into a 50 °C ± 5 °C electrothermal constant temperature water bath, perform magnetic stirring, and at the same time drop the solution B obtained in step ④ into the dispersion A at a rate of 1 mL every 5 min. After the dropping is completed, stop stirring;

[0062] ⑥ Use a centrifuge to centrifuge the dispersion obtained in step ⑤, wash it 3 times with deionized water and anhydrous ethanol respectively, and then dry it at 105 °C for 24 h;

[0063] ⑦ Heat-treat the sample obtained in step ⑥ in air at 1200 ± 5 °C for 1 h to obtain molybdenum disilicide powder coated with silica.

[0064] Comparative Example 1

[0065] ① Place anhydrous ethanol (150 mL), ammonia water (10 mL), and tetrapropylammonium bromide aqueous solution (20 mL) into a conical flask and mix them into a solution. Add 5 g of the molybdenum disilicide powder obtained in step ②, first stir magnetically for 1 h, and then perform ultrasonic treatment for 0.5 h to obtain a uniform dispersion A;

[0066] ② Mix tetraethyl orthosilicate (20 g) and anhydrous ethanol (35 mL), and stir evenly to obtain solution B;

[0067] ③ Place the dispersion A obtained in step ① into a 50 °C ± 5 °C electrothermal constant temperature water bath, perform magnetic stirring, and at the same time drop the solution B obtained in step ② into the dispersion A at a rate of 1 mL every 3 min. After the dropping is completed, stop stirring;

[0068] ④Centrifuge the dispersion obtained in step ③ using a centrifuge, wash it 3 times with deionized water and anhydrous ethanol respectively, and then dry it at 105 °C for 24 h;

[0069] ⑤Heat-treat the sample obtained in step ④ in air at 1200 ± 5 °C for 1 h to obtain molybdenum disilicide powder coated with silica.

[0070] The emissivity data of Examples 1-4 and Comparative Example 1 are shown in Table 1; the weight gain rate data of Examples 1-4, Comparative Example 1 and untreated molybdenum disilicide in each temperature range are shown in Table 2.

[0071] Table 1 Emissivity of Examples 1-4, Comparative Example 1 and untreated molybdenum disilicide

[0072]

[0073] Table 2 Weight gain rate (%) of Examples 1-4, Comparative Example 1 and untreated molybdenum disilicide in each temperature range

[0074]

[0075] It can be seen from the emissivity comparison in Table 1 that the emissivity of the molybdenum disilicide powder prepared in Examples 2-4 is higher than that of Comparative Example 1 and untreated molybdenum disilicide in all three wavelength ranges, and higher than that of Comparative Example 2 in the visible and near-infrared wavelength ranges; and the emissivity of Examples 2-4 is higher than 0.96 in the visible region and higher than 0.97 in the near-infrared region, indicating that the preparation method for modifying molybdenum disilicide of the present invention can significantly improve the radiation performance.

[0076] Since the radiation performance of Example 2 in the examples is the best. It can be seen from Table 2 that compared with Comparative Example 1 and untreated molybdenum disilicide, the weight gain of the molybdenum disilicide powder prepared in Examples 2-4 is very stable from 27 °C to 1400 °C, indicating that the molybdenum disilicide prepared by the present invention has excellent thermal stability and oxidation resistance.

[0077] Slight weight loss occurred in Example 1 above 800 °C, indicating slight oxidation above 800 °C.

[0078] Although Comparative Example 1 has good oxidation resistance below 800 °C, obvious weight loss occurred above 800 °C, indicating that above this temperature, molybdenum disilicide is oxidized to form MoO3, and its high-temperature volatilization leads to weight loss. Therefore, using low-temperature and normal-pressure pre-oxidation pretreatment and then coating with silica cannot completely inhibit the high-temperature oxidation of molybdenum disilicide above 800 °C.

[0079] Obvious oxidation plague phenomenon occurred in untreated molybdenum disilicide at 400-500 °C, and the weight loss due to the volatilization of MoO3 formed by oxidation at high temperature was more obvious.

[0080] Therefore, the two-step process of molybdenum disilicide vacuum high-temperature oxidation pretreatment and wet chemical coating of silicon dioxide is essential for improving the oxidation resistance of molybdenum disilicide. The former forms a uniform oxide on the surface of molybdenum disilicide, which is beneficial to the latter's uniform coating and thickening of the silicon dioxide protective layer.

Claims

1. A method for preparing modified molybdenum disilicide infrared radiation powder, characterized in that: It includes the following steps: Step 1): Put molybdenum disilicide powder into a tubular furnace, evacuate it, then heat it up to 1200 °C for heat preservation, and introduce air during the heating and heat preservation processes; Step 2): After the heat preservation ends, introduce argon into the tubular furnace until the pressure reaches 1 atmosphere, keep introducing argon, heat it at 1200 °C for heat preservation, and then naturally cool it to room temperature under argon protection; Step 3): Mix absolute ethanol, ammonia water, and tetrapropylammonium bromide aqueous solution, add the molybdenum disilicide powder obtained in Step 2), first stir magnetically, and then perform ultrasonic treatment to obtain a uniform dispersion A; Step 4): Mix tetraethyl orthosilicate and absolute ethanol, and stir evenly to obtain solution B; Step 5): Put the dispersion A obtained in Step 3) into an electrothermal constant temperature water bath at 50 ± 5 °C, perform magnetic stirring, and at the same time drip the solution B obtained in Step 4) into the dispersion A. After the dripping ends, stop stirring; Centrifuge the obtained dispersion, wash it multiple times with deionized water and absolute ethanol respectively, and then dry it at 105 ± 5 °C; Step 6): Heat-treat the sample obtained in Step 5) in air at 1200 ± 5 °C to obtain molybdenum disilicide powder coated with silica.

2. The preparation method of the modified molybdenum disilicide infrared radiation powder as described in claim 1, wherein In the said Step 1), the pressure in the tubular furnace is 500 - 1500 Pa; the heating rate of the tubular furnace is 8 °C / min, and the heat preservation time at 1200 °C is 45 - 120 min; the air inlet flow rate is 450 - 850 mL / h.

3. The method for preparing the modified molybdenum disilicide infrared radiation powder according to claim 1, wherein: In the said Step 2), the inlet flow rate of argon is 600 - 900 mL / h, and the heat preservation time at 1200 °C is 60 - 180 min.

4. The method for preparing the modified molybdenum disilicide infrared radiation powder according to claim 1, wherein: In the said Step 3), the mass concentration of ammonia water is 25 - 28%, and the mass concentration of tetrapropylammonium bromide aqueous solution is 30%; the ratio of molybdenum disilicide powder, absolute ethanol, ammonia water, and tetrapropylammonium bromide aqueous solution is 5 - 15 g: 100 - 300 mL: 6 - 12 mL: 10 - 30 mL.

5. The preparation method of the modified molybdenum disilicide infrared radiation powder as claimed in claim 4, wherein, In the said Step 3), the ratio of molybdenum disilicide powder, absolute ethanol, ammonia water, and tetrapropylammonium bromide aqueous solution is 5 g: 150 mL: 8 mL: 15 mL.

6. The method for preparing the modified molybdenum disilicide infrared radiation powder according to claim 1, wherein: In the said Step 4), the ratio of tetraethyl orthosilicate to absolute ethanol is 10 - 25 g: 30 - 40 mL.

7. The preparation method of the modified molybdenum disilicide infrared radiation powder as described in claim 6, characterized in that, In the said Step 4), the ratio of tetraethyl orthosilicate to absolute ethanol is 15 g: 35 mL.

8. The method for preparing the modified molybdenum disilicide infrared radiation powder according to claim 1, wherein: In the said Step 5), the weight ratio of molybdenum disilicide to tetraethyl orthosilicate is 1:3 - 1:5; the magnetic stirring speed is 650 revolutions per minute; the dripping speed of solution B is 1 mL per 1 - 5 min.

9. The preparation method of the modified molybdenum disilicide infrared radiation powder as claimed in claim 8, characterized in that, In the said Step 5), the weight ratio of molybdenum disilicide to tetraethyl orthosilicate is 1:3; the dripping speed of solution B is 1 mL per 3 min.

10. The method for preparing modified molybdenum disilicide infrared radiation powder according to claim 1, characterized in that: In the said Step 5), during washing, the ratio of deionized water or absolute ethanol to molybdenum disilicide powder is 10 mL: 1 g, and the washing time for each time is 30 min.

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