Preparation method of refractory metal boride nano-powder
Through solution combustion synthesis method and magnesium thermal reduction method of molten salt medium, refractory metal boride nanopowders were prepared, which solved the problems of high cost, difficult control and low quality in the prior art, and achieved high performance and low cost nanopowder preparation.
Patent Information
- Application Number
- CN202510057909.9
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-01-14
- Publication Date
- 2025-05-02
AI Technical Summary
The existing synthesis methods of refractory metal boride powders cannot take into account the low cost, easy process control and high product quality, which limits the development and application of materials.
The solution combustion synthesis method and the magnesium thermal reduction method of the molten salt medium are used to mix the metal salt, boric acid, ammonium nitrate and fuel in a set proportion, and heat-combustion synthesis is carried out to obtain a metal oxide/boron oxide composite precursor, and a refractory metal boronide nanopowder is prepared by reacting with the molten salt and magnesium powder.
It has achieved high purity, uniform particle size, small particles, simple process and strong controllability of refractory metal boronide nanopowders, suitable for large-scale industrial production.
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Figure CN119911919A_ABST
Abstract
Description
Technical Field
[0001] The invention relates to the field of refractory boride preparation, and in particular to a method for preparing refractory metal boride nanopowder. Background Art
[0002] Most metal elements can be combined with elemental boron to form metal borides. Among the many refractory metal borides, borides of metals or rare earth elements have attracted widespread attention due to their extremely high melting point, high hardness, good conductivity, stable chemical properties and special electron emission characteristics. Refractory metal borides have already had commercial products in the fields of ultra-high temperature thermal protection materials, special refractory materials, ceramic armor, nuclear ceramics, high temperature electric heating elements and high temperature electrodes, and are in the stage of large-scale promotion and application. Metal borides are used in many electron beam devices as high-brightness electron emission sources. In addition, the application of refractory metal borides in the fields of photothermal conversion, energy storage, catalysis, etc. is also a current research hotspot.
[0003] The processing of refractory metal boride materials is often achieved through sintering, impregnation, coating and other processes, which makes powder the key raw material for processing such materials. The use of high-purity, ultra-fine refractory boride powder will be conducive to obtaining high-performance boride materials. At present, the synthesis method of refractory metal boride powder often cannot take into account low cost, easy process control and high product quality, which seriously limits the development and application of such materials.
[0004] Refractory metal boride powders can be prepared by mixing metal oxides with boron oxide and performing carbon thermal reduction or magnesium thermal reduction. However, carbon thermal reduction has certain limitations because the reaction temperature is greater than 1400 °C, which will cause boron oxide to volatilize and lead to boron source loss, and will pollute and damage the reaction equipment. The temperature of magnesium thermal reduction is lower, which is more suitable for the preparation of refractory metal boride powders. In addition, the molten salt method not only reduces the synthesis temperature of magnesium thermal reduction, but also can utilize the faster diffusion rate of reactants in the liquid medium of molten salt. At the same time, during the reaction process, the molten salt prevents the interconnection between particles and limits the growth of crystals, so that the prepared powder has the advantages of smaller particle size and good powder dispersibility.
[0005] In recent years, solution combustion synthesis technology has attracted wide attention as a new chemical process for the preparation of nano-particle powders, including simple binary, ternary and complex multi-atom mixed nanopowders. Soluble metal salts (mainly nitrates) and organic fuels (such as urea, citric acid, glycine, etc.) are mainly used as reactants, with metal nitrates as oxidants and organic fuels as reductants. The reaction system is heated to a certain temperature to form a gel, which then spontaneously ignites, triggering a violent redox reaction. Once the gel is ignited, the reaction is maintained by the heat released by the redox reaction. The entire combustion process can be completed within a few minutes, with a large amount of gas overflowing. The product is loose in texture, has no agglomerates, and is easily crushed into ultrafine powders. This process can synthesize a variety of nano-scale materials.
[0006] The grain size of the mixture of metal oxide and boron oxide will also affect the grain size and reaction temperature of the final refractory metal boride powder. Therefore, using the mixture of nano metal oxide and boron oxide obtained by solution combustion synthesis, it is easier to synthesize refractory metal boride nanopowder by magnesium thermal reduction in a molten salt medium. Summary of the invention
[0007] The purpose of the present invention is to overcome the shortcomings of the prior art and provide a method for preparing refractory metal boride nanopowders. The prepared refractory metal boride nanopowders have the characteristics of fine particles and uniform particle size distribution. At the same time, the method is simple and easy to implement, has strong controllability, a short preparation process and is easy to implement.
[0008] The present invention adopts the following technical solution:
[0009] In one aspect, the present invention provides a method for preparing refractory metal boride nanopowders, comprising:
[0010] S1. Mix a metal salt (any one of zirconium salt, hafnium salt, molybdenum salt, lanthanum salt and titanium salt), boric acid, ammonium nitrate, fuel and deionized water in a set ratio to prepare a corresponding aqueous solution, heat and stir to evaporate the aqueous solution until the solution becomes a viscous gel state, and continue to heat to perform a combustion synthesis reaction to obtain a metal oxide / boron oxide composite precursor;
[0011] S2, fully grinding and crushing the composite precursor prepared in step S1, mixing it with a reducing medium (molten salt) and a reducing agent (magnesium powder), and putting it into a crucible with a cover, and performing a synthesis reaction in a flowing inert atmosphere for a period of time;
[0012] S3. The product synthesized in step S2 is first washed three times with deionized water, then soaked in a certain amount of acidic solution for a certain period of time, centrifuged and filtered, and vacuum dried to obtain refractory metal boride powder.
[0013] Any possible implementation as described above further provides an implementation, in step S1, in the metal oxide composite precursor, the metal oxide includes B2O3, and any one of ZrO2, HfO2, MoO3, La2O3 and TiO2.
[0014] Any possible implementation as described above, further provides an implementation, in which in step S1, the molar ratio of the metal salt (any one of zirconium salt, hafnium salt, molybdenum salt, lanthanum salt and titanium salt), boric acid, ammonium nitrate and fuel is 1: (2-12): (5-30): (5-30).
[0015] Any possible implementation as described above further provides an implementation, in step S1, the zirconium salt is any one of zirconium nitrate, zirconium chloride, zirconium sulfate and zirconium oxychloride.
[0016] As any possible implementation described above, further provided is an implementation, in step S1, the hafnium salt is any one of hafnium nitrate, hafnium chloride, hafnium sulfate and hafnium oxychloride.
[0017] Any possible implementation as described above further provides an implementation, in which in step S1, the molybdenum salt is any one of molybdenum acid, molybdenum sulfate and molybdenum chloride.
[0018] Any possible implementation as described above further provides an implementation, in step S1, the lanthanum salt is any one of lanthanum nitrate, lanthanum chloride and lanthanum sulfate.
[0019] Any possible implementation as described above further provides an implementation, in which in step S1, the titanium salt is any one of titanic acid, titanium chloride, titanium sulfate and ammonium hexafluorotitanate.
[0020] Any possible implementation as described above further provides an implementation, in which in step S1, the fuel is one or more of glycine, citric acid, and urea.
[0021] Any possible implementation as described above further provides an implementation, in step S1, the conditions of the combustion synthesis reaction are: heating temperature 300-550° C., heating time 20-60 min.
[0022] Any possible implementation as described above, further provides an implementation, in step S2, the reducing medium molten salt is one of NaCl and KCl or a mixture of NaCl and KCl in a molar ratio of 1:1; the total mass ratio of the metal oxide / boron oxide composite precursor obtained in step S1 to the molten salt is 1:(1.5-3); the molar ratio of the metal oxide / boron oxide composite precursor obtained in step S1 to the magnesium powder is 1:(4-20).
[0023] Any possible implementation as described above, further provides an implementation, in step S2, a reduction reaction is carried out in an inert atmosphere in a tube furnace, and the reaction conditions are: a heating rate of 2 to 10 ° C / min, a reaction temperature of 700 to 1000 ° C, a holding time of 1 to 5 h, an inert gas flow rate of 500 to 1000 mL / min, and the inert atmosphere is argon or helium.
[0024] Any possible implementation as described above, further provides an implementation, in step S3, the acidic solution is any one of sulfuric acid, hydrochloric acid, nitric acid and hydrofluoric acid, with a concentration of 0.5 to 2 mol / L; the immersion time is 3 to 10 h.
[0025] On the other hand, the present invention also provides a refractory metal boride nanopowder, which is prepared by the above method, and the refractory metal boride nanopowder is characterized by uniform particle size, an average particle size of 50 to 200 nm, and a specific surface area of 2 to 8 m 2 / g, purity>98%.
[0026] The beneficial effects of the present invention are:
[0027] 1. The present invention provides a method for preparing a refractory metal boride nanopowder, which can be selectively prepared by controlling parameters such as the type and ratio of the raw materials, heating rate, reaction temperature and time, thereby controlling the synthesis of a refractory metal boride nanopowder to achieve multi-field application.
[0028] 2. The large amount of gas released during the liquid combustion synthesis reaction in the preparation method provided by the present invention can effectively prevent the agglomeration of nanoparticles, which is conducive to the final formation of refractory metal boride nanopowders with uniform loading and high dispersion of each metal component particle.
[0029] 3. The refractory metal boride nanopowder prepared by the method of solution combustion synthesis + magnesium thermal reduction in a molten salt medium of the present invention has high purity and uniform particle size, laying a foundation for the preparation of high-performance refractory metal boride materials.
[0030] 4. The raw materials of the present invention are cheap and easily available, the equipment is simple, the process is fast, the controllability is strong, it is suitable for large-scale industrial production, and has broad application prospects. BRIEF DESCRIPTION OF THE DRAWINGS
[0031] Figure 1 Shown is a schematic flow chart of a method for preparing refractory metal boride nanopowder according to an embodiment of the present invention. DETAILED DESCRIPTION
[0032] The specific embodiments of the present invention will be described in detail below in conjunction with specific drawings. It should be noted that the technical features or combinations of technical features described in the following embodiments should not be considered isolated, and they can be combined with each other to achieve better technical effects.
[0033] like Figure 1 As shown, a method for preparing a refractory metal boride nanopowder according to an embodiment of the present invention comprises:
[0034] S1. Mix a metal salt (any one of zirconium salt, hafnium salt, molybdenum salt, lanthanum salt and titanium salt), boric acid, ammonium nitrate, fuel and deionized water in a set ratio to prepare a corresponding aqueous solution, heat and stir to evaporate the aqueous solution until the solution becomes a viscous gel state, and continue to heat to perform a combustion synthesis reaction to obtain a metal oxide / boron oxide composite precursor;
[0035] S2, fully grinding and crushing the composite precursor prepared in step S1, mixing it with a reducing medium (molten salt) and a reducing agent (magnesium powder), and putting it into a crucible with a cover, and performing a synthesis reaction in a flowing inert atmosphere for a period of time;
[0036] S3. The product synthesized in step S2 is first washed three times with deionized water, then soaked in a certain amount of acidic solution for a certain period of time, centrifuged and filtered, and vacuum dried to obtain refractory metal boride powder.
[0037] In a specific embodiment, in step S1, in the metal oxide composite precursor, the metal oxide must include B2O3, and any one of ZrO2, HfO2, MoO3, La2O3 and TiO2.
[0038] In a specific embodiment, in step S1, the molar ratio of the metal salt (any one of zirconium salt, hafnium salt, molybdenum salt, lanthanum salt and titanium salt), boric acid, ammonium nitrate and fuel is 1: (2-12): (5-30): (5-30).
[0039] In a specific embodiment, in step S1, the zirconium salt is any one of zirconium nitrate, zirconium chloride, zirconium sulfate and zirconium oxychloride.
[0040] In a specific embodiment, in step S1, the hafnium salt is any one of hafnium nitrate, hafnium chloride, hafnium sulfate and hafnium oxychloride.
[0041] In a specific embodiment, in step S1, the molybdenum salt is any one of molybdenum acid, molybdenum sulfate and molybdenum chloride.
[0042] In a specific embodiment, in step S1, the lanthanum salt is any one of lanthanum nitrate, lanthanum chloride and lanthanum sulfate.
[0043] In a specific embodiment, in step S1, the titanium salt is any one of titanic acid, titanium chloride, titanium sulfate and ammonium hexafluorotitanate.
[0044] In a specific embodiment, in step S1, the fuel is one or more of glycine, citric acid, and urea.
[0045] In a specific embodiment, in step S1, the conditions of the combustion synthesis reaction are: heating temperature 300-550° C., heating time 20-60 min.
[0046] In a specific embodiment, in step S2, the reducing medium molten salt is one of NaCl and KCl or a mixture of NaCl and KCl in a molar ratio of 1:1; the total mass ratio of the metal oxide / boron oxide composite precursor obtained in step S1 to the molten salt is 1:(1.5-3); the molar ratio of the metal oxide / boron oxide composite precursor obtained in step S1 to the magnesium powder is 1:(4-20).
[0047] In a specific embodiment, in step S2, a reduction reaction is carried out in an inert atmosphere in a tube furnace, and the reaction conditions are: a heating rate of 2 to 10 °C / min, a reaction temperature of 700 to 1000 °C, a holding time of 1 to 5 h, an inert gas flow rate of 500 to 1000 mL / min, and the inert atmosphere is argon or helium.
[0048] In a specific embodiment, in step S3, the acidic solution is any one of sulfuric acid, hydrochloric acid, nitric acid and hydrofluoric acid, with a concentration of 0.5 to 2 mol / L; and the soaking time is 3 to 10 h.
[0049] The present invention provides a refractory metal boride nanopowder prepared by the above method. The refractory metal boride nanopowder is characterized by having uniform particle size, an average particle size of 50 to 200 nm, and a specific surface area of 2 to 8 m 2 / g, purity>98%.
[0050] Example 1
[0051] Zirconium nitrate, boric acid, ammonium nitrate and glycine were weighed in a molar ratio of 1:2:5:6, dissolved in a small amount of deionized water, and stirred thoroughly with a glass rod until completely dissolved into an aqueous solution. The mixed solution was placed on a temperature-controlled resistance furnace and heated to gradually evaporate the water until the solution turned into a brown gel state. It was then kept at 450 °C for 35 min to undergo a violent combustion synthesis reaction. The product after the reaction was fully ground to obtain a metal oxide / boron oxide composite precursor powder. The prepared precursor powder was mixed with NaCl (the mass ratio of the metal oxide / boron oxide composite precursor to NaCl was 1:1.5) and magnesium powder (the molar ratio of the metal oxide / boron oxide composite precursor to magnesium powder was 1:4) and placed in a crucible with a lid. The synthesis reaction was carried out in a flowing argon atmosphere. The temperature was raised to 900 °C at a rate of 3 °C / min, kept for 2 h, and then cooled with the furnace. The argon flow rate was 500 mL / min. The synthesized product was first washed with deionized water for three times, then soaked in 0.5 mol / L hydrochloric acid solution for 10 h, and then centrifuged, filtered, and vacuum dried to obtain refractory metal boride powder.
[0052] The average particle size of the prepared refractory metal boride nanopowder is 62 nm, the particle size is uniform, and the specific surface area is 7.19 m 2 / g, purity 98.5%.
[0053] Example 2
[0054] Hafnium chloride, boric acid, ammonium nitrate and glycine + citric acid were weighed in a molar ratio of 1:2.5:25:20+5, dissolved in a small amount of deionized water, and stirred thoroughly with a glass rod until completely dissolved into an aqueous solution. The mixed solution was placed on a temperature-controlled resistance furnace and heated to gradually evaporate the water until the solution turned into a brown gel state. It was kept at 400 °C for 45 minutes to undergo a violent combustion synthesis reaction. The product after the reaction was fully ground to obtain a metal oxide / boron oxide composite precursor powder. The prepared precursor powder was mixed with KCl (the mass ratio of the metal oxide / boron oxide composite precursor to NaCl was 1:2.5) and magnesium powder (the molar ratio of the metal oxide / boron oxide composite precursor to magnesium powder was 1:5) and placed in a crucible with a lid. The synthesis reaction was carried out in a flowing argon atmosphere, and the temperature was raised to 1000 °C at a rate of 5 °C / min. After keeping the temperature for 1 h, it was cooled with the furnace. The helium flow rate was 1000 mL / min. The synthesized product was first washed with deionized water for three times, then soaked in 1 mol / L hydrofluoric acid solution for 3 h, and then centrifuged, filtered, and vacuum dried to obtain refractory metal boride powder.
[0055] The average particle size of the prepared refractory metal boride nanopowder is 110 nm, the particle size is uniform, and the specific surface area is 3.95 m2 / g, purity 98.9%.
[0056] Example 3
[0057] Molybdenum acid, boric acid, ammonium nitrate and glycine + urea were weighed in a molar ratio of 1:3.5:20:10+6, dissolved in a small amount of deionized water, and stirred thoroughly with a glass rod until completely dissolved into an aqueous solution. The mixed solution was placed on a temperature-controlled resistance furnace and heated to gradually evaporate the water until the solution turned into a brown gel state. It was kept at 500 °C for 20 min, and a violent combustion synthesis reaction occurred. The product after the reaction was fully ground to obtain a metal oxide / boron oxide composite precursor powder. The prepared precursor powder was mixed with a NaCl+KCl mixed salt with a molar ratio of 1:1 (the mass ratio of the metal oxide / boron oxide composite precursor to NaCl was 1:3) and magnesium powder (the molar ratio of the metal oxide / boron oxide composite precursor to magnesium powder was 1:5.5) and placed in a crucible with a lid. The synthesis reaction was carried out in a flowing argon atmosphere, and the temperature was raised to 750 °C at a rate of 10 °C / min. After keeping the temperature for 5 h, it was cooled with the furnace. The argon flow rate was 500 mL / min. The synthesized product was first washed three times with deionized water, then soaked in 2 mol / L nitric acid solution for 10 h, and then centrifuged, filtered, and vacuum dried to obtain refractory metal boride powder.
[0058] The average particle size of the prepared refractory metal boride nanopowder is 55 nm, the particle size is uniform, and the specific surface area is 7.92 m 2 / g, purity 99.7%.
[0059] Example 4
[0060] Lanthanum sulfate, boric acid, ammonium nitrate and citric acid + urea were weighed in a molar ratio of 1:12:30:9+7, dissolved in a small amount of deionized water, and stirred thoroughly with a glass rod until completely dissolved into an aqueous solution. The mixed solution was placed on a temperature-controlled resistance furnace and heated to gradually evaporate the water until the solution turned into a brown gel state. It was kept at 300 °C for 60 min, and a violent combustion synthesis reaction occurred. The product after the reaction was fully ground to obtain a metal oxide / boron oxide composite precursor powder. The prepared precursor powder was mixed with NaCl (the mass ratio of the metal oxide / boron oxide composite precursor to NaCl was 1:2) and magnesium powder (the molar ratio of the metal oxide / boron oxide composite precursor to magnesium powder was 1:20) and placed in a crucible with a lid. The synthesis reaction was carried out in a flowing argon atmosphere, and the temperature was raised to 1000 °C at a rate of 10 °C / min. After keeping the temperature for 5 h, it was cooled with the furnace. The helium flow rate was 800 mL / min. The synthesized product was first washed with deionized water for three times, then soaked in 1.5 mol / L sulfuric acid solution for 7 h, and then centrifuged, filtered, and vacuum dried to obtain refractory metal boride powder.
[0061] The average particle size of the prepared refractory metal boride nanopowder is 190 nm, the particle size is uniform, and the specific surface area is 2.29 m 2 / g, purity 99.2%.
[0062] Example 5
[0063] Titanium chloride, boric acid, ammonium nitrate and glycine were weighed in a molar ratio of 1:2.2:9:10, dissolved in a small amount of deionized water, and stirred thoroughly with a glass rod until they were completely dissolved into an aqueous solution. The mixed solution was placed on a temperature-controlled resistance furnace and heated to gradually evaporate the water until the solution turned into a brown gel state. It was then kept at 450 °C for 40 min to undergo a violent combustion synthesis reaction. The product after the reaction was fully ground to obtain a metal oxide / boron oxide composite precursor powder. The prepared precursor powder was mixed with NaCl (the mass ratio of the metal oxide / boron oxide composite precursor to NaCl was 1:2) and magnesium powder (the molar ratio of the metal oxide / boron oxide composite precursor to magnesium powder was 1:4.5) and placed in a crucible with a lid. The synthesis reaction was carried out in a flowing argon atmosphere. The temperature was raised to 800 °C at a rate of 2 °C / min, kept for 4 h, and then cooled with the furnace. The argon flow rate was 500 mL / min. The synthesized product was first washed with deionized water for three times, then soaked in 0.5 mol / L hydrochloric acid solution for 10 h, and then centrifuged, filtered, and vacuum dried to obtain refractory metal boride powder.
[0064] The average particle size of the prepared refractory metal boride nanopowder is 92 nm, the particle size is uniform, and the specific surface area is 4.81 m2 / g, purity 99.1%.
[0065] The present invention utilizes a solution combustion synthesis (SCS) method to prepare a refractory metal boride nanopowder. Compared with a mechanical alloying method and a spray drying method, the SCS method has some unprecedented advantages. It can utilize the exothermic reaction between ammonium nitrate and metal salts (acting as oxidants in the reaction system) such as nitrates, sulfates, carbonates, chlorides, etc. and fuels (acting as reducing agents in the reaction system) such as glycine, citric acid, urea, etc. The heat generated enables the entire reaction system to continuously maintain an oxidation-reduction reaction. The gas generated by the reaction can obtain a sufficiently fluffy and fine metal oxide precursor, providing a basis for the subsequent preparation of nanocomposite powders. The method for preparing nanopowders of the present invention is simple, fast, low in energy consumption, and easy to mass produce. In addition, the method can have high purity, fine grain size, and is easy to control the proportion of components, laying a foundation for the preparation of high-performance refractory metal boride nanopowders.
[0066] Although the embodiments of the present invention have been given herein, those skilled in the art should understand that the embodiments of the present invention may be modified without departing from the spirit of the present invention. The above embodiments are merely exemplary and should not be used as a limitation on the scope of the present invention.
Claims
1. A method for preparing refractory metal boride nanopowder, characterized in that: The method comprises: S1. Mix metal salt, boric acid, ammonium nitrate, fuel and deionized water in a set ratio to prepare a corresponding aqueous solution, heat and stir to evaporate the aqueous solution until the solution becomes a viscous gel state, and continue heating to perform a combustion synthesis reaction to obtain a metal oxide / boron oxide composite precursor; S2, grinding and crushing the composite precursor prepared in step S1, mixing it with the reducing medium molten salt and the reducing agent magnesium powder, putting it into a crucible with a cover, and performing a synthesis reaction in a flowing inert atmosphere for a period of time; S3. The product synthesized in step S2 is first washed three times with deionized water, then soaked in a certain amount of acidic solution for a certain period of time, centrifuged and filtered, and vacuum dried to obtain refractory metal boride powder.
2. The method for preparing refractory metal boride nanopowder according to claim 1, characterized in that: In step S1, in the metal oxide composite precursor, the metal oxide includes B2O3, and any one of ZrO2, HfO2, MoO3, La2O3 and TiO2.
3. The method for preparing refractory metal boride nanopowder according to claim 1, characterized in that: In step S1, the metal salt is any one of zirconium salt, hafnium salt, molybdenum salt, lanthanum salt and titanium salt, and the molar ratio of the metal salt, boric acid, ammonium nitrate and fuel is 1: (2-12): (5-30): (5-30).
4. The method for preparing refractory metal boride nanopowder according to claim 1, characterized in that: In step S1, the zirconium salt is any one of zirconium nitrate, zirconium chloride, zirconium sulfate and zirconium oxychloride, and the hafnium salt is any one of hafnium nitrate, hafnium chloride, hafnium sulfate and hafnium oxychloride; The molybdenum salt is any one of molybdenum acid, molybdenum sulfate and molybdenum chloride; The lanthanum salt is any one of lanthanum nitrate, lanthanum chloride and lanthanum sulfate; The titanium salt is any one of titanic acid, titanium chloride, titanium sulfate and ammonium hexafluorotitanate; The fuel is one or more of glycine, citric acid and urea.
5. The method for preparing refractory metal boride nanopowder according to claim 1, characterized in that: In step S1, the conditions of the combustion synthesis reaction are: heating temperature 300-550°C, heating time 20-60 min.
6. The method for preparing refractory metal boride nanopowder according to claim 1, characterized in that: In step S2, the reducing medium molten salt is one of NaCl and KCl or a mixture of NaCl and KCl in a molar ratio of 1:1; the total mass ratio of the metal oxide / boron oxide composite precursor obtained in step S1 to the molten salt is 1:(1.5-3); the molar ratio of the metal oxide / boron oxide composite precursor obtained in step S1 to the magnesium powder is 1:(4-20).
7. The method for preparing refractory metal boride nanopowder according to claim 1, characterized in that: In step S2, a reduction reaction is carried out in an inert atmosphere in a tubular furnace, and the reaction conditions are: a heating rate of 2 to 10 °C / min, a reaction temperature of 700 to 1000 °C, a holding time of 1 to 5 h, an inert gas flow rate of 500 to 1000 mL / min, and the inert atmosphere is argon or helium.
8. The method for preparing refractory metal boride nanopowder according to claim 1, characterized in that: In step S3, the acidic solution is any one of sulfuric acid, hydrochloric acid, nitric acid and hydrofluoric acid, with a concentration of 0.5 to 2 mol / L; the soaking time is 3 to 10 hours.
9. The method for preparing refractory metal boride nanopowder according to claim 1, characterized in that: The prepared refractory metal boride nanopowder has uniform particle size, an average particle size of 50 to 200 nm, and a specific surface area of 2 to 8 m 2 / g, purity>98%.