Combustion synthesis method of multi-component transition metal boride ceramic powder

Abstract

The invention discloses a combustion synthesis method of multi-component transition metal boride ceramic powder, relates to the field of ultrahigh-temperature ceramic materials, and aims to solve the problems of low purity and low production efficiency of the index multi-component transition metal boride ceramic powder in the conventional method. The method comprises the following steps: 1, preparing transition metal oxide solid solution powder from transition metal powder and transition metal oxide powder through combustion synthesis; 2, adding boron oxide and magnesium powder into the transition metal oxide solid solution powder, and uniformly mixing; 3, putting the mixed material into a closed reaction container, igniting, and carrying out a self-propagating magnesiothermic reduction reaction; and 4, cooling, taking out a reaction product, and carrying out acid pickling, suction filtration, washing and drying to obtain the multi-component transition metal boride ceramic powder. According to the method, the production time is greatly shortened, and the production efficiency can be improved. The prepared multi-component transition metal boride ceramic powder has high purity and high solid solution degree. The method is used for preparing the multi-component transition metal boride ceramic powder.

Description

Technical Field

[0001] The invention relates to the field of ultra-high temperature ceramic materials, and in particular to a combustion synthesis method for multi-component transition metal boride ceramic powder. Background Art

[0002] The melting point of ultra-high temperature ceramics is usually higher than 3000℃. They have high strength, thermal shock resistance and excellent oxidation and ablation resistance. They can maintain non-ablative properties and structural integrity in an oxidizing environment above 1800℃. Therefore, ultra-high temperature ceramics have extremely broad application prospects in extreme environments, such as the next generation of hypersonic aircraft, nuclear reactors, leading edges and nose cones of aircraft wings, and nozzles of rockets, air-breathing enhanced propulsion systems and engines. However, with the increasing requirements for material properties, traditional single-component ultra-high temperature ceramics are gradually unable to meet the demand. Compared with single-component ceramics, multi-component ceramics have excellent mechanical properties and oxidation resistance, and are expected to become high-performance ultra-high temperature ceramic materials. According to the size of the mixing entropy, multi-component ceramics can be divided into high-entropy ceramics, medium-entropy ceramics and low-entropy ceramics. The solid solution formed by four or more ceramic components is called high-entropy ceramics. When the components in the high-entropy ceramics are equimolar, the mixing entropy is the largest and the Gibbs free energy is the lowest.

[0003] At present, the methods for synthesizing multi-component transition metal boride ceramic powders and the problems that exist are as follows:

[0004] (1) Reduction method: including boron thermal reduction method and boron / carbon thermal reduction method, etc., using transition metal oxides, B or B4C as raw materials, and preparing multi-component transition metal boride ceramic powder by keeping warm at high temperature. However, this method requires the external environment to provide a higher reaction temperature and a longer reaction time, so it has the disadvantages of high energy consumption and long production cycle.

[0005] (2) Elemental method: Using transition metal elements and B powder as raw materials, multi-component transition metal boride ceramic powder is prepared by self-propagating high-temperature synthesis. This method not only has the problem of high cost, but also a small amount of other diborides and trace transition metal oxides are detected in the reaction products, that is, the purity of the product is low.

[0006] (3) Mechanical alloying method: This method uses single-component transition metal borides as raw materials and prepares multi-component transition metal boride powders by mechanical alloying. The products prepared by this method usually contain a second phase solid solution and need to be sintered to obtain a single multi-component transition metal boride phase. In addition, the method is costly and impurities are easily mixed into the product. Summary of the invention

[0007] The present invention aims to solve the problems of low purity and low production efficiency of multi-component transition metal boride ceramic powder in existing methods, and provides a combustion synthesis method for multi-component transition metal boride ceramic powder.

[0008] The combustion synthesis method of the multi-component transition metal boride ceramic powder of the present invention comprises the following steps:

[0009] Step 1, drying the transition metal powder, transition metal oxide powder, boron oxide and magnesium powder;

[0010] Step 2, mixing the dried transition metal powder and transition metal oxide powder evenly to obtain a mixed powder;

[0011] Step 3, the mixed powder is loaded into a high-pressure reaction vessel, and O2 or O2 mixed gas is filled into the high-pressure reaction vessel. A nozzle is provided at the lower end of the high-pressure reaction vessel, and the nozzle orifice diameter of the nozzle is 1-6 mm. The mixed powder is ignited to cause a self-propagating high-temperature synthesis reaction. The reaction temperature is 3100-4500K to form a high-temperature melt, which is kept warm for 5-30 seconds. Then the nozzle is opened and the melt is sprayed into water under pressure. After cooling, a suspension of transition metal oxide solid solution powder is obtained. After suction filtration and drying, a transition metal oxide solid solution powder is obtained.

[0012] Step 4: Weigh transition metal oxide solid solution powder, add boron oxide and magnesium powder and mix evenly to obtain a mixed material;

[0013] Step 5: Place the mixed material into a sealed reaction vessel, remove all O2 in the sealed reaction vessel, fill in protective gas, ignite the mixed material, and cause a self-propagating magnesium thermal reduction reaction at a reaction temperature of 2200-3098K. After the mixed material is ignited, start circulating water for cooling;

[0014] Step 6: After cooling, the reaction product is taken out, and the product is washed with acid to remove magnesium oxide, and then filtered, washed, and dried to obtain a multi-component transition metal boride ceramic powder.

[0015] Furthermore, in step 1, the transition metal powder is a mixture of one or more of Ti, Zr, Hf, Nb, Ta, Cr, Mo, and W.

[0016] Furthermore, in step one, the transition metal oxide powder is a mixture of two or more of TiO2, ZrO2, HfO2, Nb2O5, Ta2O5, Cr2O5, MoO2, and WO3.

[0017] Furthermore, when there are two or more transition metal elements in the transition metal oxide solid solution powder obtained in step three, the molar ratio of each transition metal element can be any ratio.

[0018] Preferably, when there are four or more transition metal elements in the transition metal oxide solid solution powder obtained in step three, the molar ratio of each transition metal element is (0.9 to 1.1): (0.9 to 1.1).

[0019] Furthermore, the magnesium powder in step 1 is dried in vacuum, inert gas or reducing gas.

[0020] Furthermore, in step 1, the drying temperature is 50-80° C. and the drying time is 24 hours.

[0021] Furthermore, the O2 mixed gas in step three is a mixed gas of oxygen and inert gas.

[0022] Furthermore, in the mixed material described in step 4, the mass fraction of magnesium powder is 35%-50%, the mass fraction of boron oxide is 15%-30%, and the remainder is transition metal oxide solid solution powder.

[0023] Furthermore, in step five, the pressure of the protective gas is 0.1-2 MPa.

[0024] Principle of the present invention:

[0025] The invention prepares multi-component transition metal boride powder by self-propagating magnesium thermal reduction reaction, wherein the transition metal element can be selected from elements such as Ti, Zr, Hf, Nb, Ta, Cr, Mo and W, and the high entropy (Ti 0.2 Zr 0.2 Hf 0.2 Nb 0.2 Ta 0.2 )B2 powder is used as an example to introduce the principle of this method, but the present invention is not limited to the high entropy transition metal boride ceramic powder of this composition, but also includes multi-component transition metal boride powders prepared by different combinations of the above transition metal elements.

[0026] The present invention uses transition metal and transition metal oxide powder as raw materials. First, the transition metal powder reacts with oxygen to release heat to melt the transition metal oxide added as a diluent to form a uniform high-quality high-temperature melt. After keeping the temperature for a period of time, the melt is sprayed into water under pressure to quickly cool, and a transition metal oxide solid solution powder with a micron size and uniformly distributed components is obtained. Although the transition metal oxide solid solution prepared by this method is not a single-phase solid solution, but a mixture of multiple oxide solid solutions, as a raw material for self-propagating magnesium thermal reduction, it is not necessary to obtain a single-phase solid solution, but only the transition metal elements need to be uniformly distributed, so that short-range diffusion is carried out during the magnesium thermal reduction process. Since the melt is evenly mixed at high temperature, the transition metal elements are evenly distributed in the powder, and the prepared transition metal oxide solid solution powder is (TiZrHfNbTa)O 11The chemical reaction equation is as follows:

[0027]

[0028] In the formula, x and y are the contents of transition metal elements added as reactants. By changing the values ​​of x and y, the adiabatic temperature of the reaction can be changed within the temperature range of 3100-4500K, and the corresponding required oxygen pressure range is 15-17MPa. Because the five transition metal elements must be equimolar or nearly equimolar in the final product, the values ​​of x and y are between 0 and 1. In addition to Ti and Nb powders, other transition metal powders can also be selected as reducing agents to react with oxygen.

[0029] The transition metal oxide solid solution prepared above is used as a raw material, and after being uniformly mixed with boron oxide and magnesium powder, a self-propagating magnesium thermal reduction reaction occurs, and the reaction products are high entropy transition metal boride and magnesium oxide. The reaction is shown in the following chemical equation:

[0030] (TiZrHfNbTa)O 11 +5B2O3+26Mg→5(Ti 0.2 Zr 0.2 Hf 0.2 Nb 0.2 Ta 0.2 )B2+26MgO

[0031] The reaction is carried out under a protective atmosphere, and the pressure range of the protective gas is 0.1-2MPa. In addition, an appropriate amount of magnesium oxide can be added as a diluent in the reaction to adjust the adiabatic temperature of the reaction, thereby controlling the size of the prepared multi-component transition metal boride powder. The higher the content of the diluent magnesium oxide, the lower the adiabatic temperature of the reaction, and thus the smaller the particle size of the powder. Self-propagating combustion synthesis reaction can occur when the diluent magnesium oxide content accounts for 0-37wt% of the entire raw material. When the diluent magnesium oxide content is 0-6.19wt%, the adiabatic temperature of the reaction is 3098K, which is exactly the melting point of magnesium oxide. Therefore, during the reaction, magnesium oxide will partially melt, and the diffusion rate of transition metal elements in the liquid phase is higher than that in the solid phase, which is conducive to the preparation of single-phase multi-component transition metal boride powder with high purity and uniform composition. Since the transition metal elements have already been uniformly distributed in the transition metal oxide solid solution powder in advance, only short-range diffusion is required during the self-propagating magnesium thermal reduction reaction, which can avoid the formation of other transition metal boride phases. This is further conducive to obtaining high-purity, high-solubility single-phase multi-component transition metal boride ceramic powder.

[0032] Beneficial effects of the present invention:

[0033] The present invention adopts a method of self-propagating magnesium thermal combustion synthesis to prepare micron-level multi-component transition metal boride powder with high purity and high solid solubility. The advantages of this method are low energy consumption, short reaction time, low cost and high production efficiency. Compared with the existing synthesis method, self-propagating magnesium thermal combustion synthesis relies on the energy released by chemical reaction, and no external energy is required except for the ignition process; the self-propagating reaction is completed in a very short time, which greatly shortens the production time and can improve production efficiency.

[0034] The method of the present invention uses transition metal oxide as raw material, which can reduce the cost of raw materials. The method prepares transition metal oxide solid solution powder by combustion synthesis water mist method, so that transition metal elements are evenly distributed in advance, which is beneficial to improve the purity and solid solubility of multi-component transition metal boride and obtain high-purity single-phase solid solution.

[0035] To sum up, the advantage of this invention is that it can prepare micron-sized multi-component transition metal boride ceramic powder with high purity and high solid solubility through combustion synthesis. This method has the advantages of low energy consumption, high production efficiency and low cost. The product has excellent performance and has broad application prospects. The use of this method will have obvious social and economic benefits. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] Figure 1 The composition distribution of the transition metal oxide solid solution powder prepared in Example 1;

[0037] Figure 2 The XRD pattern of the reaction product prepared in Example 2;

[0038] Figure 3 (Ti prepared in Example 2 0.2 Zr 0.2 Hf 0.2 Nb 0.2 Ta 0.2 ) Microstructure of B2 ceramic powder;

[0039] Figure 4 (Ti prepared in Example 2 0.2 Zr 0.2 Hf 0.2 Nb 0.2 Ta 0.2 )B2 composition distribution of ceramic powder;

[0040] Figure 5 XRD pattern of the reaction product prepared in comparative example;

[0041] Figure 6 Element distribution of the reaction product prepared as a comparative example. DETAILED DESCRIPTION

[0042] The technical solution of the present invention is not limited to the specific implementation modes listed below, but also includes any combination of the specific implementation modes.

[0043] Specific implementation method 1: The combustion synthesis method of multi-component transition metal boride ceramic powder in this implementation method includes the following steps:

[0044] Step 1, drying the transition metal powder, transition metal oxide powder, boron oxide and magnesium powder;

[0045] Step 2, mixing the dried transition metal powder and transition metal oxide powder evenly to obtain a mixed powder;

[0046] Step 3, the mixed powder is loaded into a high-pressure reaction vessel, and O2 or O2 mixed gas is filled into the high-pressure reaction vessel. A nozzle is provided at the lower end of the high-pressure reaction vessel, and the nozzle orifice diameter of the nozzle is 1-6 mm. The mixed powder is ignited to cause a self-propagating high-temperature synthesis reaction. The reaction temperature is 3100-4500K to form a high-temperature melt, which is kept warm for 5-30 seconds. Then the nozzle is opened and the melt is sprayed into water under pressure. After cooling, a suspension of transition metal oxide solid solution powder is obtained. After suction filtration and drying, a transition metal oxide solid solution powder is obtained.

[0047] Step 4: Weigh transition metal oxide solid solution powder, add boron oxide and magnesium powder and mix evenly to obtain a mixed material;

[0048] Step 5: Place the mixed material into a sealed reaction vessel, remove all O2 in the sealed reaction vessel, fill in protective gas, ignite the mixed material, and cause a self-propagating magnesium thermal reduction reaction at a reaction temperature of 2200-3098K. After the mixed material is ignited, start circulating water for cooling;

[0049] Step 6: After cooling, the reaction product is taken out, and the product is washed with acid to remove magnesium oxide, and then filtered, washed, and dried to obtain a multi-component transition metal boride ceramic powder.

[0050] Specific embodiment 2: In step 1 of this embodiment, the transition metal powder is a mixture of one or more of Ti, Zr, Hf, Nb, Ta, Cr, Mo, and W. Other steps and parameters are the same as those in specific embodiment 1.

[0051] Specific embodiment 3: In step 1 of this embodiment, the transition metal oxide powder is a mixture of two or more of TiO2, ZrO2, HfO2, Nb2O5, Ta2O5, Cr2O5, MoO2, and WO3. Other steps and parameters are the same as those of specific embodiment 1 or 2.

[0052] Specific embodiment 4: When there are two or more transition metal elements in the transition metal oxide solid solution powder obtained in step 3 of this embodiment, the molar ratio of each transition metal element is any ratio. Other steps and parameters are the same as those in specific embodiment 3.

[0053] Specific implementation mode 5: When there are four or more transition metal elements in the transition metal oxide solid solution powder obtained in step 3 of this implementation mode, the molar ratio of each transition metal element is (0.9-1.1): (0.9-1.1). Other steps and parameters are the same as those in specific implementation mode 3.

[0054] A solid solution formed by four or more ceramic components is called a high-entropy ceramic. When the components in a high-entropy ceramic are equimolar, the mixing entropy is the largest, the Gibbs free energy is the lowest, and the ceramic material is more stable.

[0055] Specific implementation method 6: In step 1 of this implementation method, the magnesium powder is dried in vacuum, inert gas or reducing gas. The other steps and parameters are the same as those of specific implementation methods 1 to 5.

[0056] Specific implementation method 7: In step 1 of this implementation method, the drying temperature is 50-80° C. and the drying time is 24 hours. The other steps and parameters are the same as those of specific implementation methods 1 to 6.

[0057] Specific implementation example 8: The O2 mixed gas in step 3 of this implementation example is a mixed gas of oxygen and inert gas. The other steps and parameters are the same as those in specific implementation examples 1 to 7.

[0058] Specific embodiment 9: In the mixed material described in step 4 of this embodiment, the mass fraction of magnesium powder is 35%-50%, the mass fraction of boron oxide is 15%-30%, and the remainder is transition metal oxide solid solution powder. Other steps and parameters are the same as those of specific embodiments 1 to 8.

[0059] Specific implementation method 10: In step 5 of this implementation method, the pressure of the protective gas is 0.1-2 MPa. Other steps and parameters are the same as those of specific implementation methods 1 to 9.

[0060] The embodiments of the present invention are described in detail below. The following embodiments are implemented on the premise of the technical solution of the present invention, and detailed implementation schemes and specific operation processes are given, but the protection scope of the present invention is not limited to the following embodiments.

[0061] Embodiment 1:

[0062] This embodiment (Ti 0.2 Zr 0.2 Hf 0.2 Nb 0.2 Ta0.2 )B2 The combustion synthesis method of ceramic powder is specifically completed by the following steps:

[0063] 1. Dry titanium powder, niobium powder, zirconium dioxide, hafnium dioxide, niobium pentoxide, tantalum pentoxide, boron oxide and magnesium powder. Titanium powder, niobium powder and magnesium powder are vacuum dried at a vacuum degree of 0.06MPa, a drying temperature of 50°C and a drying time of 24h; zirconium dioxide, hafnium dioxide, niobium pentoxide, tantalum pentoxide and boron oxide are directly dried at a drying temperature of 80°C and a drying time of 24h;

[0064] 2. Mix 23.94 g of titanium powder, 41.81 g of niobium powder, 61.61 g of zirconium dioxide, 105.25 g of hafnium dioxide, 6.65 g of niobium pentoxide and 110.45 g of tantalum pentoxide after drying to obtain a mixed powder;

[0065] 3. The mixed material is loaded into a high-pressure reaction vessel, and O2 is filled into the vessel. The pressure of the O2 is 16.07MPa. A nozzle is provided at the lower end of the high-pressure reaction vessel to ignite the mixed powder, and a self-propagating high-temperature synthesis reaction occurs to form a high-temperature melt. The temperature is kept for 7 seconds, and then the nozzle is opened to spray the melt into water under pressure. After cooling, a suspension of transition metal oxide solid solution powder is obtained. After suction filtration and drying, a transition metal oxide solid solution powder is obtained.

[0066] 4. 99.76 g of transition metal oxide solid solution powder, 49.78 g of boron oxide and 106.82 g of magnesium powder were mixed uniformly to obtain a mixed material;

[0067] 5. Place the mixed material into a sealed reaction vessel, flush the sealed reaction vessel with argon gas to remove all O2 in the reaction vessel, and then fill it with argon gas at a pressure of 2MPa as a protective gas. Use a resistance wire to ignite it to cause a self-propagating magnesium thermal reduction reaction, and after ignition, start circulating water for cooling;

[0068] 6. After cooling, take out the reaction product, the product is (Ti 0.2 Zr 0.2 Hf 0.2 Nb 0.2 Ta 0.2 )B2 and magnesium oxide mixture, the product was pickled with 2.5mol / L hydrochloric acid solution to remove magnesium oxide, the remaining (Ti 0.2 Zr 0.2 Hf 0.2 Nb 0.2 Ta 0.2 )B2 powder is filtered, washed and dried to obtain the final product.

[0069] The composition distribution of the transition metal oxide solid solution powder obtained in step 3 of Example 1 was characterized. Figure 1 As shown, it can be seen that in the prepared transition metal oxide solid solution powder, each transition metal element is evenly distributed, which is conducive to obtaining a single-phase solid solution through short-range diffusion in the subsequent process.

[0070] Embodiment 2:

[0071] This embodiment (Ti 0.2 Zr 0.2 Hf 0.2 Nb 0.2 Ta 0.2 )B2 The combustion synthesis method of ceramic powder is specifically completed by the following steps:

[0072] 1. Dry titanium powder, niobium powder, zirconium dioxide, hafnium dioxide, tantalum pentoxide, boron oxide and magnesium powder. Titanium powder, niobium powder and magnesium powder are vacuum dried at a vacuum degree of 0.06MPa, a drying temperature of 50°C and a drying time of 24h; zirconium dioxide, hafnium dioxide, tantalum pentoxide and boron oxide are directly dried at a drying temperature of 80°C and a drying time of 24h;

[0073] 2. Mix 23.94 g of titanium powder, 46.46 g of niobium powder, 61.61 g of zirconium dioxide, 105.25 g of hafnium dioxide and 110.45 g of tantalum pentoxide after drying to obtain a mixed powder;

[0074] 3. The mixed powder is loaded into a high-pressure reaction vessel, and O2 is filled into the vessel. The pressure of the O2 is 16.92MPa. A nozzle is provided at the lower end of the high-pressure reaction vessel, and the mixed powder is ignited to cause a self-propagating high-temperature synthesis reaction to form a high-temperature melt. The temperature is kept for 7 seconds, and then the nozzle is opened to spray the melt into water under pressure. After cooling, a suspension of transition metal oxide solid solution powder is obtained, and the transition metal oxide solid solution powder is obtained after suction filtration and drying;

[0075] 4. 99.76 g of transition metal oxide solid solution powder, 49.78 g of boron oxide and 106.82 g of magnesium powder were mixed uniformly to obtain a mixed material;

[0076] 5. Place the mixed material into a sealed reaction vessel, flush the sealed reaction vessel with argon gas to remove all O2 in the reaction vessel, and then fill it with argon gas at a pressure of 2MPa as a protective gas. Use a resistance wire to ignite it to cause a self-propagating magnesium thermal reduction reaction, and after ignition, start circulating water for cooling;

[0077] 6. After cooling, take out the reaction product, the product is (Ti 0.2 Zr 0.2 Hf 0.2 Nb 0.2Ta 0.2 )B2 and magnesium oxide mixture, the product was pickled with 2.5mol / L hydrochloric acid solution to remove magnesium oxide, the remaining (Ti 0.2 Zr 0.2 Hf 0.2 Nb 0.2 Ta 0.2 )B2 powder is filtered, washed and dried to obtain the final product.

[0078] The (Ti obtained in Example 2 0.2 Zr 0.2 Hf 0.2 Nb 0.2 Ta 0.2 )B2 ceramic powder phase composition and component distribution were analyzed, such as Figures 2 to 4 shown. Figure 2 is the XRD pattern of the reaction product prepared by this method, Figure 2 The red curve represents the product after pickling, and the black curve represents the product before pickling. 0.2 Zr 0.2 Hf 0.2 Nb 0.2 Ta 0.2 )B2 and magnesium oxide. After pickling, magnesium oxide is completely removed, and only high entropy (Ti 0.2 Zr 0.2 Hf 0.2 Nb 0.2 Ta 0.2 )B2 phase, no impurity phase exists, proving that high-purity multi-component transition metal boride is obtained. Based on XRD data, the synthesized (Ti 0.2 Zr 0.2 Hf 0.2 Nb 0.2 Ta 0.2 )The lattice constant of the B2 phase is Compared with the experimental values ​​in the literature and theoretical calculated values Very close, indicating that the synthesized high entropy boride has high solid solubility. Figure 3 For synthesis (Ti 0.2 Zr 0.2 Hf 0.2 Nb 0.2 Ta 0.2 ) From the microscopic morphology of the B2 phase, it can be seen that the powder is equiaxed and the particle size is 2-4μm. Figure 4 Yes (Ti 0.2 Zr 0.2 Hf 0.2 Nb 0.2 Ta 0.2)B2 ceramic powder component distribution, it can be seen that the transition metal elements are evenly distributed without obvious segregation. In summary, the multi-component transition metal boride ceramic powder prepared by the method of the present invention has high purity and high solid solubility.

[0079] Comparative Example:

[0080] The preparation method of the transition metal boride ceramic powder of this comparative example is as follows:

[0081] 1. Dry titanium dioxide, zirconium dioxide, hafnium dioxide, niobium pentoxide, tantalum pentoxide, boron oxide and magnesium powder. The magnesium powder is vacuum dried at a vacuum degree of 0.06MPa, a drying temperature of 50°C and a drying time of 24h. Titanium dioxide, zirconium dioxide, hafnium dioxide, niobium pentoxide, tantalum pentoxide and boron oxide are directly dried at a drying temperature of 80°C and a drying time of 24h.

[0082] 2. Evenly mix 10.38 g of titanium dioxide, 16.02 g of zirconium dioxide, 27.37 g of hafnium dioxide, 17.28 g of niobium pentoxide, 28.72 g of tantalum pentoxide, 49.78 g of boron oxide and 106.82 g of magnesium powder after drying to obtain a mixed material;

[0083] 3. Place the mixed material into a sealed reaction vessel, flush the reaction vessel with argon gas to remove all O2 in the reaction vessel, and then fill it with argon gas at a pressure of 2MPa as a protective gas. Use a resistance wire to ignite it to cause a self-propagating magnesium thermal reduction reaction, and after ignition, start circulating water for cooling;

[0084] 4. After cooling, the reaction product is taken out. The product is a mixture of multi-component transition metal boride and magnesium oxide. The product is pickled with 2.5 mol / L hydrochloric acid solution to remove magnesium oxide. The remaining multi-component transition metal boride powder is filtered, washed and dried to obtain the final product.

[0085] The transition metal oxide powders were mixed evenly and then subjected to a self-propagating magnesium thermal reduction reaction as a comparative test. The phase composition and element distribution of the reaction products were shown in Figure 2. Figure 5 and Figure 6 As shown. Figure 5 It can be seen that the reaction product before pickling is high entropy (Ti 0.2 Zr 0.2 Hf 0.2 Nb 0.2 Ta 0.2 )B2, MgO and oxide impurity phases. After pickling, MgO is completely removed, but the oxide impurity phase is still retained, resulting in a lower purity of the product. Figure 6From the distribution of elements in the product after pickling, it can be seen that some elements are segregated, indicating that the components in the powder are not uniform and the degree of solid solubility is low. The reason why the purity and solid solubility of the product prepared by the comparative method are low is that the transition metal elements in the mixed powder are not evenly distributed, and long-range diffusion is required during the reaction, but the self-propagating reaction is completed in a very short time, and the MgO generated by the reaction will isolate the transition metal oxide, and the reaction is carried out in an independent micro-region, resulting in insufficient diffusion of the transition metal elements and the formation of other impurity phases, thereby reducing the purity and solid solubility. The elements in the transition metal solid solution powder have been evenly distributed, and only short-range diffusion is required during the reaction, so that a high-purity, high-solubility product can be obtained.

[0086] Embodiment 3:

[0087] This embodiment (Ti 0.25 Zr 0.25 Hf 0.25 Nb 0.25 )B2 The combustion synthesis method of ceramic powder is specifically completed by the following steps:

[0088] 1. Dry titanium powder, niobium powder, zirconium dioxide, hafnium dioxide, niobium pentoxide, boron oxide and magnesium powder. Titanium powder, niobium powder and magnesium powder are dried under vacuum at a vacuum degree of 0.06MPa, a drying temperature of 50°C and a drying time of 24h; zirconium dioxide, hafnium dioxide, niobium pentoxide and boron oxide are directly dried at a drying temperature of 80°C and a drying time of 24h;

[0089] 2. Mix 31.30 g of titanium powder, 35.79 g of niobium powder, 80.56 g of zirconium dioxide, 137.62 g of hafnium dioxide and 35.69 g of niobium pentoxide after drying to obtain a mixed powder;

[0090] 3. The mixed powder is loaded into a high-pressure reaction vessel, and O2 is filled into the vessel. The pressure of the O2 is 15.77 MPa. A nozzle is provided at the lower end of the high-pressure reaction vessel, and the mixed powder is ignited to cause a self-propagating high-temperature synthesis reaction to form a high-temperature melt. The melt is kept warm for 10 seconds, and then the nozzle is opened to spray the melt into water under pressure. After cooling, a suspension of transition metal oxide solid solution powder is obtained. After suction filtration and drying, the transition metal oxide solid solution powder is obtained.

[0091] 4. 136.63 g of transition metal oxide solid solution powder, 76.58 g of boron oxide and 158.02 g of magnesium powder were uniformly mixed to obtain a mixed material;

[0092] 5. Place the mixed material into a sealed reaction vessel, flush the reaction vessel with argon gas to remove all O2 in the reaction vessel, and then fill it with argon gas at a pressure of 2MPa as a protective gas. Use a resistance wire to ignite it to cause a self-propagating magnesium thermal reduction reaction, and after ignition, start circulating water for cooling;

[0093] 6. After cooling, take out the reaction product, the product is (Ti 0.25 Zr 0.25 Hf 0.25 Nb 0.25 )B2 and magnesium oxide mixture, the product was pickled with 2.5mol / L hydrochloric acid solution to remove magnesium oxide, the remaining (Ti 0.25 Zr 0.25 Hf 0.25 Nb 0.25 )B2 powder is filtered, washed and dried to obtain the final product.

[0094] The (Ti 0.25 Zr 0.25 Hf 0.25 Nb 0.25 )B2 ceramic powder is a micron-sized multi-component transition metal boride powder with high purity and high solid solubility.

[0095] Embodiment 4:

[0096] This embodiment (Ti 0.4 Zr 0.4 Hf 0.2 )B2 The combustion synthesis method of ceramic powder is specifically completed by the following steps:

[0097] 1. Dry titanium powder, zirconium dioxide, titanium dioxide, hafnium dioxide, boron oxide and magnesium powder. Titanium powder and magnesium powder are vacuum dried at a vacuum degree of 0.06MPa, a drying temperature of 50°C and a drying time of 24h; zirconium dioxide, titanium dioxide, hafnium dioxide and boron oxide are directly dried at a drying temperature of 80°C and a drying time of 24h;

[0098] 2. Mix 49.60 g of the dried titanium powder, 135.11 g of zirconium dioxide, 4.82 g of titanium dioxide and 115.41 g of hafnium dioxide to obtain a mixed powder;

[0099] 3. The mixed powder is loaded into a high-pressure reaction vessel, and O2 is filled into the vessel. The pressure of the O2 is 15.73 MPa. A nozzle is provided at the lower end of the high-pressure reaction vessel to ignite the mixed powder, and a self-propagating high-temperature synthesis reaction occurs to form a high-temperature melt. The temperature is kept for 10 seconds, and then the nozzle is opened to spray the melt into water under pressure. After cooling, a suspension of transition metal oxide solid solution powder is obtained, and the transition metal oxide solid solution powder is obtained after suction filtration and drying;

[0100] 4. 123.34 g of transition metal oxide solid solution powder, 73.10 g of boron oxide and 145.86 g of magnesium powder were mixed uniformly to obtain a mixed material;

[0101] 5. Place the mixed material into a sealed reaction vessel, flush the reaction vessel with argon gas to remove all O2 in the reaction vessel, and then fill it with argon gas at a pressure of 2MPa as a protective gas. Use a resistance wire to ignite it to cause a self-propagating magnesium thermal reduction reaction, and after ignition, start circulating water for cooling;

[0102] 6. After cooling, take out the reaction product, the product is (Ti 0.4 Zr 0.4 Hf 0.2 )B2 and magnesium oxide mixture, the product was pickled with 2.5mol / L hydrochloric acid solution to remove magnesium oxide, the remaining (Ti 0.4 Zr 0.4 Hf 0.2 )B2 powder is filtered, washed and dried to obtain the final product.

[0103] The (Ti 0.4 Zr 0.4 Hf 0.2 )B2 ceramic powder is a micron-sized multi-component transition metal boride powder with high purity and high solid solubility.

[0104] Embodiment 5:

[0105] This embodiment (Ti 0.5 Zr 0.5 )B2 The combustion synthesis method of ceramic powder is specifically completed by the following steps:

[0106] 1. Dry titanium powder, zirconium dioxide, titanium dioxide, boron oxide and magnesium powder. Titanium powder and magnesium powder are vacuum dried at a vacuum degree of 0.06MPa, a drying temperature of 50°C and a drying time of 24h; zirconium dioxide, titanium dioxide and boron oxide are directly dried at a drying temperature of 80°C and a drying time of 24h;

[0107] 2. Mix 52.26 g of the dried titanium powder, 173.55 g of zirconium dioxide and 25.29 g of titanium dioxide to obtain a mixed powder;

[0108] 3. The mixed powder is loaded into a high-pressure reaction vessel, and O2 is filled into the vessel. The pressure of the O2 is 16.57 MPa. A nozzle is provided at the lower end of the high-pressure reaction vessel, and the mixed powder is ignited to cause a self-propagating high-temperature synthesis reaction to form a high-temperature melt. The temperature is kept for 10 seconds, and then the nozzle is opened to spray the melt into water under pressure. After cooling, a suspension of transition metal oxide solid solution powder is obtained, and the transition metal oxide solid solution powder is obtained after suction filtration and drying;

[0109] 4. 101.55 g of transition metal oxide solid solution powder, 69.62 g of boron oxide and 133.7 g of magnesium powder were uniformly mixed to obtain a mixed material;

[0110] 5. Place the mixed material into a sealed reaction vessel, flush the reaction vessel with argon gas to remove all the O2 in the reaction vessel, and then fill it with argon gas at a pressure of 2MPa as a protective gas. Use a resistance wire to ignite it to cause a self-propagating magnesium thermal reduction reaction, and after ignition, start circulating water for cooling;

[0111] 6. After cooling, take out the reaction product, the product is (Ti 0.5 Zr 0.5 )B2 and magnesium oxide mixture, the product was pickled with 2.5mol / L hydrochloric acid solution to remove magnesium oxide, the remaining (Ti 0.5 Zr 0.5 )B2 powder is filtered, washed and dried to obtain the final product.

[0112] The (Ti 0.5 Zr 0.5 )B2 ceramic powder is a micron-sized multi-component transition metal boride powder with high purity and high solid solubility.

[0113] Embodiment 6:

[0114] This embodiment (Ti 0.8 Zr 0.2 )B2 The combustion synthesis method of ceramic powder is specifically completed by the following steps:

[0115] 1. Dry titanium powder, zirconium dioxide, titanium dioxide, boron oxide and magnesium powder. Titanium powder and magnesium powder are vacuum dried at a vacuum degree of 0.06MPa, a drying temperature of 50°C and a drying time of 24h; zirconium dioxide, titanium dioxide and boron oxide are directly dried at a drying temperature of 80°C and a drying time of 24h;

[0116] 2. Mix 49.13 g of the dried titanium powder, 71.09 g of zirconium dioxide and 102.36 g of titanium dioxide to obtain a mixed powder;

[0117] 3. The mixed powder is loaded into a high-pressure reaction vessel, and O2 is filled into the vessel. The pressure of the O2 is 15.58 MPa. A nozzle is provided at the lower end of the high-pressure reaction vessel, and the mixed powder is ignited to cause a self-propagating high-temperature synthesis reaction to form a high-temperature melt. The melt is kept warm for 10 seconds, and then the nozzle is opened to spray the melt into water under pressure. After cooling, a suspension of transition metal oxide solid solution powder is obtained, and the transition metal oxide solid solution powder is obtained after suction filtration and drying;

[0118] 4. 88.54 g of transition metal oxide solid solution powder, 69.62 g of boron oxide and 121.55 g of magnesium powder were mixed uniformly to obtain a mixed material;

[0119] 5. Place the mixed material into a sealed reaction vessel, flush the reaction vessel with argon gas to remove all O2 in the reaction vessel, and then fill it with argon gas at a pressure of 2MPa as a protective gas. Use a resistance wire to ignite it to cause a self-propagating magnesium thermal reduction reaction, and after ignition, start circulating water for cooling;

[0120] 6. After cooling, take out the reaction product, the product is (Ti 0.8 Zr 0.2 )B2 and magnesium oxide mixture, the product was pickled with 2.5mol / L hydrochloric acid solution to remove magnesium oxide, the remaining (Ti 0.8 Zr 0.2 )B2 powder is filtered, washed and dried to obtain the final product.

[0121] The (Ti 0.8 Zr 0.2 )B2 ceramic powder is a micron-sized multi-component transition metal boride powder with high purity and high solid solubility.

Claims

1. A combustion synthesis method for multi-component transition metal boride ceramic powder, characterized in that: The method comprises the following steps: Step 1, drying the transition metal powder, transition metal oxide powder, boron oxide and magnesium powder; Step 2, mixing the dried transition metal powder and transition metal oxide powder evenly to obtain a mixed powder; Step 3, the mixed powder is loaded into a high-pressure reaction vessel, and O2 or O2 mixed gas is filled into the high-pressure reaction vessel. A nozzle is provided at the lower end of the high-pressure reaction vessel, and the nozzle orifice diameter of the nozzle is 1-6 mm. The mixed powder is ignited to cause a self-propagating high-temperature synthesis reaction. The reaction temperature is 3100-4500K to form a high-temperature melt, which is kept warm for 5-30 seconds. Then the nozzle is opened and the melt is sprayed into water under pressure. After cooling, a suspension of transition metal oxide solid solution powder is obtained. After suction filtration and drying, a transition metal oxide solid solution powder is obtained. Step 4: Weigh transition metal oxide solid solution powder, add boron oxide and magnesium powder and mix evenly to obtain a mixed material; Step 5: Place the mixed material into a sealed reaction vessel, remove all O2 in the sealed reaction vessel, fill in protective gas, ignite the mixed material, and cause a self-propagating magnesium thermal reduction reaction at a reaction temperature of 2200-3098K. After the mixed material is ignited, start circulating water for cooling; Step 6: After cooling, the reaction product is taken out, and the product is washed with acid to remove magnesium oxide, and then filtered, washed, and dried to obtain a multi-component transition metal boride ceramic powder.

2. The combustion synthesis method of multi-component transition metal boride ceramic powder according to claim 1, characterized in that: In step 1, the transition metal powder is a mixture of one or more of Ti, Zr, Hf, Nb, Ta, Cr, Mo, and W.

3. The combustion synthesis method of multi-component transition metal boride ceramic powder according to claim 1 or 2, characterized in that: In step 1, the transition metal oxide powder is a mixture of two or more of TiO2, ZrO2, HfO2, Nb2O5, Ta2O5, Cr2O5, MoO2, and WO3.

4. The combustion synthesis method of multi-component transition metal boride ceramic powder according to claim 3, characterized in that: When there are two or more transition metal elements in the transition metal oxide solid solution powder obtained in step 3, the molar ratio of each transition metal element can be any ratio.

5. The combustion synthesis method of multi-component transition metal boride ceramic powder according to claim 3, characterized in that: When there are four or more transition metal elements in the transition metal oxide solid solution powder obtained in step 3, the molar ratio of each transition metal element is (0.9 to 1.1): (0.9 to 1.1).

6. The combustion synthesis method of multi-component transition metal boride ceramic powder according to claim 1, characterized in that: The magnesium powder in step 1 is dried in vacuum, inert gas or reducing gas.

7. The combustion synthesis method of multi-component transition metal boride ceramic powder according to claim 6, characterized in that: In step 1, the drying temperature is 50-80°C and the drying time is 24h.

8. The combustion synthesis method of multi-component transition metal boride ceramic powder according to claim 1, characterized in that: The O2 mixed gas in step 3 is a mixed gas of oxygen and inert gas.

9. The combustion synthesis method of multi-component transition metal boride ceramic powder according to claim 1, characterized in that: In the mixed material described in step 4, the mass fraction of magnesium powder is 35%-50%, the mass fraction of boron oxide is 15%-30%, and the remainder is transition metal oxide solid solution powder.

10. The combustion synthesis method of multi-component transition metal boride ceramic powder according to claim 1, characterized in that: In step 5, the pressure of the protective gas is 0.1-2 MPa.

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