Process for the combustion synthesis of multi-component transition metal boride ceramic powders

Abstract

The application relates to the field of ultra-high-temperature ceramic materials and relates to a combustion synthesis method of a multi-component transition metal boride ceramic powder, and aims to solve the problems of low purity and low production efficiency of the multi-component transition metal boride ceramic powder in the prior art. The method comprises the following steps: 1, preparing a transition metal oxide solid solution powder by combustion synthesis of transition metal powder and transition metal oxide powder; 2, uniformly mixing the transition metal oxide solid solution powder, boron oxide and magnesium powder; 3, loading the mixed materials into a sealed reaction container, igniting and causing a self-propagating magnesium hot reduction reaction; and 4, taking out the reaction product after cooling, and obtaining the multi-component transition metal boride ceramic powder after acid washing, suction filtration, washing and drying. The method greatly shortens the production time and can improve the production efficiency. The prepared multi-component transition metal boride ceramic powder has high purity and high solid solution degree. The application is used for preparing the multi-component transition metal boride ceramic powder.

Description

Technical Field

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

[0002] Ultrahigh-temperature ceramics (UHT) typically have melting points above 3000°C and exhibit high strength, resistance to thermal shock, and excellent resistance to oxidation and ablation. They can maintain non-ablative properties and structural integrity in oxidizing environments above 1800°C. Therefore, UHT ceramics hold great promise for applications in extreme environments, such as next-generation hypersonic vehicles, nuclear reactors, aircraft wing leading edges and nose cones, rocket nozzles, air-breathing augmented propulsion systems, and engines. However, with increasing demands for material properties, traditional single-component UHT ceramics are increasingly unable to meet these demands. Compared to single-component ceramics, multi-component ceramics offer superior mechanical properties and oxidation resistance, holding them promise as high-performance UHT ceramic materials. Based on the magnitude of their mixing entropy, multi-component ceramics can be categorized as high-entropy, medium-entropy, and low-entropy ceramics. Solid solutions formed from four or more ceramic components are called high-entropy ceramics. When the components in a high-entropy ceramic are equimolar, the mixing entropy is maximized and the Gibbs free energy is minimized.

[0003] Currently, 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 it warm at high temperature. However, this method requires external high reaction temperature and long reaction time, thus having disadvantages such as high energy consumption and long production cycle.

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

[0006] (3) Mechanical alloying method: This method uses single-component transition metal boride as raw material and prepares multi-component transition metal boride powder by mechanical alloying. The product prepared by this method usually contains a second phase solid solution, which requires sintering to obtain a single multi-component transition metal boride phase. In addition, the cost is high 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: Evenly mix the dried transition metal powder and transition metal oxide powder to obtain a mixed powder;

[0011] Step 3: The mixed powder is placed in a high-pressure reaction vessel, and the high-pressure reaction vessel is filled with O2 or an O2 mixed gas. 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 at a reaction temperature of 3100-4500K to form a high-temperature melt. The melt is kept warm for 5-30 seconds, and 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: Weighing transition metal oxide solid solution powder, adding boron oxide and magnesium powder and mixing 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 it with protective gas, ignite the mixed material, and cause a self-propagating magnesium thermal reduction reaction at a 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, the transition metal powder in step 1 is a mixture of one or more of Ti, Zr, Hf, Nb, Ta, Cr, Mo, and W.

[0016] Furthermore, the transition metal oxide powder in step 1 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 3, 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 (0.9-1.1):(0.9-1.1).

[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 of 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 present 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 from 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, forming a uniform, high-quality high-temperature melt. After keeping the temperature for a period of time, the melt is sprayed into water under pressure and rapidly cooled to obtain a transition metal oxide solid solution powder with a micron size and uniformly distributed components. 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. Only a uniform distribution of transition metal elements is required, so that short-range diffusion occurs 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. The prepared transition metal oxide solid solution powder is (TiZrHfNbTa)O 11The chemical reaction equation is as follows:

[0027]

[0028] Where x and y represent the amounts of transition metal reactants added. By varying the values ​​of x and y, the adiabatic temperature of the reaction can be adjusted within the range of 3100-4500 K, corresponding to the required oxygen pressure range of 15-17 MPa. Because the five transition metal elements must be present in equimolar or near equimolar amounts in the final product, the values ​​of x and y range from 0 to 1. In addition to Ti and Nb powders, other transition metal powders can also be used 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. 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 with a protective gas pressure range of 0.1 to 2 MPa. In addition, an appropriate amount of magnesium oxide can be added to the reaction as a diluent 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. A self-propagating combustion synthesis reaction can occur when the diluent magnesium oxide content accounts for 0 to 37 wt% of the entire raw material. When the diluent magnesium oxide content is between 0 and 6.19 wt%, the adiabatic temperature of the reaction is 3098 K, which is exactly the melting point of magnesium oxide. Therefore, during the reaction, the magnesium oxide will partially melt, and the diffusion rate of the transition metal elements in the liquid phase is higher than the diffusion rate in the solid phase, which is conducive to the preparation of a single-phase multi-component transition metal boride powder with high purity and uniform composition. Since the transition metal elements have 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 solid solubility single-phase multi-component transition metal boride ceramic powder.

[0032] Beneficial effects of the present invention:

[0033] The present invention utilizes a self-propagating magnesium thermal combustion synthesis method to produce micron-sized, multi-component transition metal boride powders with high purity and solid solubility. This method offers the advantages of low energy consumption, short reaction time, low cost, and high production efficiency. Compared to existing synthesis methods, self-propagating magnesium thermal combustion synthesis relies on the energy released by chemical reactions and, except for the ignition process, requires no external energy. The self-propagating reaction is completed in an extremely short time, significantly shortening production time and improving production efficiency.

[0034] The method of the present invention uses transition metal oxides as raw materials, which can reduce raw material costs. The method prepares transition metal oxide solid solution powders through a combustion synthesis water mist method, which uniformly distributes the transition metal elements in advance, thereby improving the purity and solid solubility of the multi-component transition metal boride and obtaining a 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 performance is excellent and it 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 ) Micromorphology 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 The XRD pattern of the reaction product prepared in the 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 embodiments listed below, but also includes any combination of the specific embodiments.

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

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

[0045] Step 2: Evenly mix the dried transition metal powder and transition metal oxide powder to obtain a mixed powder;

[0046] Step 3: The mixed powder is placed in a high-pressure reaction vessel, and the high-pressure reaction vessel is filled with O2 or an O2 mixed gas. 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 at a reaction temperature of 3100-4500K to form a high-temperature melt. The melt is kept warm for 5-30 seconds, and 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: Weighing transition metal oxide solid solution powder, adding boron oxide and magnesium powder and mixing 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 it with protective gas, ignite the mixed material, and cause a self-propagating magnesium thermal reduction reaction at a 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. The other steps and parameters are the same as those of specific embodiments 1 or 2.

[0052] Specific embodiment 4: In this embodiment, 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. Other steps and parameters are the same as those in specific embodiment 3.

[0053] Specific embodiment 5: When there are four 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 (0.9-1.1):(0.9-1.1). Other steps and parameters are the same as those in specific embodiment 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 maximized, the Gibbs free energy is minimized, and the ceramic material is more stable.

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

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

[0057] Specific embodiment 8: The O2 mixed gas in step 3 of this embodiment is a mixed gas of oxygen and inert gas. The other steps and parameters are the same as those in specific embodiments 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 balance is transition metal oxide solid solution powder. The other steps and parameters are the same as those of specific embodiments 1 to 8.

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

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

[0061] Example 1:

[0062] This embodiment (Ti 0.2 Zr 0.2 Hf 0.2 Nb 0.2 Ta0.2 The combustion synthesis method of B2 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. The titanium powder, niobium powder and magnesium powder are vacuum dried at a vacuum degree of 0.06 MPa, a drying temperature of 50°C and a drying time of 24 hours. 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 24 hours.

[0064] 2. Mix 23.94 g of dried 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 to obtain a mixed powder;

[0065] 3. The mixed material is placed in a high-pressure reaction vessel, and the vessel is filled with O2 at a pressure of 16.07 MPa. A nozzle is provided at the lower end of the high-pressure reaction vessel to ignite the mixed powder, causing 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. After suction filtration and drying, the transition metal oxide solid solution powder is obtained.

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

[0067] 5. Place the mixed material into a sealed reaction vessel, flush the sealed reaction vessel with argon to remove all O2 in the reaction vessel, and then fill it with argon 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. 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 acid washed 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, the transition metal elements are evenly distributed, which is conducive to obtaining a single-phase solid solution through short-range diffusion in the subsequent process.

[0070] Example 2:

[0071] This embodiment (Ti 0.2 Zr 0.2 Hf 0.2 Nb 0.2 Ta 0.2 The combustion synthesis method of B2 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 0.06 MPa, a drying temperature of 50°C and a drying time of 24 hours; zirconium dioxide, hafnium dioxide, tantalum pentoxide and boron oxide are directly dried at a drying temperature of 80°C and a drying time of 24 hours;

[0073] 2. Mix 23.94 g of dried 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 to obtain a mixed powder;

[0074] 3. The mixed powder is placed in a high-pressure reaction vessel, and the vessel is filled with O2 at a pressure of 16.92 MPa. A nozzle is provided at the lower end of the high-pressure reaction vessel to ignite the mixed powder, causing 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, which is filtered and dried to obtain the transition metal oxide solid solution powder.

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

[0076] 5. Place the mixed material into a sealed reaction vessel, flush it with argon to remove all the O2 in the vessel, and then fill it with argon 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 acid washed 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 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. According to 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 The results are very close, indicating that the synthesized high entropy boride has high solid solubility. Figure 3 For the synthesis (Ti 0.2 Zr 0.2 Hf 0.2 Nb 0.2 Ta 0.2 ) The microscopic morphology of the B2 phase shows that the powder is equiaxed and has a particle size of 2-4 μm. Figure 4 Yes (Ti 0.2 Zr 0.2 Hf 0.2 Nb 0.2 Ta 0.2)B2 ceramic powder composition 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. Magnesium powder is dried under vacuum at a vacuum degree of 0.06 MPa, a drying temperature of 50°C and a drying time of 24 hours. 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 24 hours.

[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 vessel with argon to remove all O2 in the vessel, and then fill it with argon 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 self-propagating magnesium thermal reduction reaction was carried out after the transition metal oxide powder was evenly mixed as a comparative test. The phase composition and element distribution of the reaction product are 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 still remains, 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] Example 3:

[0087] This embodiment (Ti 0.25 Zr 0.25 Hf 0.25 Nb 0.25 The combustion synthesis method of B2 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 vacuum dried at a vacuum degree of 0.06 MPa, a drying temperature of 50°C and a drying time of 24 hours; zirconium dioxide, hafnium dioxide, niobium pentoxide and boron oxide are directly dried at a drying temperature of 80°C and a drying time of 24 hours;

[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 placed in a high-pressure reaction vessel, and the vessel is filled with O2 at a pressure of 15.77 MPa. A nozzle is provided at the lower end of the high-pressure reaction vessel to ignite the mixed powder, causing 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, which is filtered and dried to obtain the transition metal oxide solid solution powder.

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

[0092] V. The mixture is loaded into a closed reaction vessel, the reaction vessel is flushed with argon, O2 in the reaction vessel is removed, and then argon is filled into the reaction vessel as a protective gas with a pressure of 2 MPa. The self-propagating magnesium thermal reduction reaction is ignited by an electric resistance wire, and after ignition, circulating water is started to cool;

[0093] VI. The reaction product is taken out after cooling, and the product is a mixture of (Ti 0.25 Zr 0.25 Hf 0.25 Nb 0.25 )B2 and magnesium oxide. The product is washed with 2.5 mol / L hydrochloric acid solution to remove magnesium oxide, and 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 prepared in this example is a micron-sized multi-component transition metal boride powder with high purity and high solid solubility.

[0095] Example 4:

[0096] The combustion synthesis method of the (Ti 0.4 Zr 0.4 Hf 0.2 )B2 ceramic powder in this example is completed according to the following steps:

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

[0098] II. The dried 49.60 g titanium powder, 135.11 g zirconium dioxide, 4.82 g titanium dioxide, and 115.41 g hafnium dioxide are mixed uniformly to obtain a mixed powder.

[0099] III. The mixed powder is loaded into a high-pressure reaction vessel, O2 is filled into the vessel, the pressure of the filled O2 is 15.73 MPa, a nozzle is arranged at the lower end of the high-pressure reaction vessel, the mixed powder is ignited to occur a self-propagating high-temperature synthesis reaction to form a high-temperature melt, and the melt is sprayed into water under the action of pressure after 10 s of heat preservation. A suspension liquid of transition metal oxide solid solution powder is obtained after cooling, and the transition metal oxide solid solution powder is obtained after filtration and drying.

[0100] Four, 123.34 g of transition metal oxide solid solution powder, 73.10 g of boron oxide and 145.86 g of magnesium powder are mixed uniformly to obtain a mixture;

[0101] Five, the mixture is loaded into a closed reaction container, the reaction container is flushed with argon, O2 in the reaction container is removed, and then argon with a pressure of 2 MPa is filled as a protective gas. The self-propagating magnesium hot reduction reaction is ignited by resistance wire, and after ignition, circulating water is opened for cooling;

[0102] Six, after cooling, the reaction product is taken out, the product is a mixture of (Ti 0.4 Zr 0.4 Hf 0.2 )B2 and magnesium oxide, the product is washed with 2.5 mol / L hydrochloric acid solution to remove magnesium oxide, and 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 prepared in this example is a micron-sized multi-component transition metal boride powder with high purity and high solid solubility.

[0104] Example 5:

[0105] The combustion synthesis method of the (Ti 0.5 Zr 0.5 )B2 ceramic powder in this example is completed according to the following steps:

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

[0107] Two, 52.26 g of dried titanium powder, 173.55 g of zirconium dioxide and 25.29 g of titanium dioxide are mixed uniformly to obtain a mixed powder;

[0108] Three, the mixed powder is loaded into a high-pressure reaction container, O2 is filled into the container, the pressure of the filled O2 is 16.57 MPa, a nozzle is arranged at the lower end of the high-pressure reaction container, the mixed powder is ignited to occur a self-propagating high-temperature synthesis reaction to form a high-temperature melt, and the melt is sprayed into water under the action of pressure after 10 s of heat preservation, to obtain a suspension of transition metal oxide solid solution powder after cooling, which is filtered and dried to obtain the transition metal oxide solid solution powder.

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

[0110] 5. Place the mixed material into a sealed reaction vessel, flush the vessel with argon to remove all O2 in the vessel, and then fill it with argon 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 acid washed 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] Example 6:

[0114] This embodiment (Ti 0.8 Zr 0.2 The combustion synthesis method of B2 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 0.06 MPa, a drying temperature of 50°C and a drying time of 24 hours; zirconium dioxide, titanium dioxide and boron oxide are directly dried at a drying temperature of 80°C and a drying time of 24 hours;

[0116] 2. Mix 49.13 g of 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 placed in a high-pressure reaction vessel, and the vessel is filled with O2 at a pressure of 15.58 MPa. A nozzle is provided at the lower end of the high-pressure reaction vessel to ignite the mixed powder, causing 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, which is filtered and dried to obtain the transition metal oxide solid solution powder.

[0118] Four, 88.54 g of transition metal oxide solid solution powder, 69.62 g of boron oxide and 121.55 g of magnesium powder are mixed to obtain a mixture;

[0119] Five, the mixture is loaded into a closed reaction container, the reaction container is flushed with argon to remove O2 in the reaction container, and then argon with a pressure of 2 MPa is filled as a protective gas. The self-propagating magnesium thermal reduction reaction is ignited by resistance wire, and after ignition, circulating water is opened for cooling;

[0120] Six, after cooling, the reaction product is taken out, and the product is a mixture of (Ti 0.8 Zr 0.2 )B2 and magnesium oxide. The product is washed with 2.5 mol / L hydrochloric acid solution to remove magnesium oxide, and 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 prepared in the embodiment 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: Evenly mix the dried transition metal powder and transition metal oxide powder to obtain a mixed powder; Step 3: The mixed powder is placed in a high-pressure reaction vessel, and the high-pressure reaction vessel is filled with O2 or an O2 mixed gas. 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 at a reaction temperature of 3100-4500 K to form a high-temperature melt. The melt is kept warm for 5-30 seconds, and then the nozzle is opened and the melt is sprayed into water under pressure. After cooling, a suspension of a transition metal oxide solid solution powder is obtained. After filtration and drying, a transition metal oxide solid solution powder is obtained. Step 4: Weighing transition metal oxide solid solution powder, adding boron oxide and magnesium powder and mixing 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 it with protective gas, ignite the mixed material, and cause a self-propagating magnesium thermal reduction reaction at a temperature of 2200-3098 K. After ignition, start circulating water for cooling; Step 6: After cooling, the reaction product is taken out, and the product is acid-washed to remove magnesium oxide, and then filtered, washed, and dried to obtain a multi-component transition metal boride ceramic powder; In step 1, the transition metal powder is a mixture of one or more of Ti, Zr, Hf, Nb, Ta, Cr, Mo, and W; 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.

2. The combustion synthesis method of multi-component transition metal boride ceramic powder according to claim 1, 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.

3. The combustion synthesis method of multi-component transition metal boride ceramic powder according to claim 1, 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 (0.9~1.1): (0.9~1.1).

4. 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.

5. The combustion synthesis method of multi-component transition metal boride ceramic powder according to claim 4, characterized in that: In step 1, the drying temperature is 50-80°C and the drying time is 24 hours.

6. 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.

7. The combustion synthesis method of multi-component transition metal boride ceramic powder according to claim 1, characterized in that: In the mixed material of 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.

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

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