Component-adjustable (Hfx, Zry) C nanowire and preparation method thereof

Abstract

The invention relates to a component-adjustable (Hfx, Zry) C nanowire and a preparation method thereof.The preparation method comprises the steps that ZrCl4 powder and HfCl4 powder are mixed according to a set proportion to obtain mixed powder, then the mixed powder is placed in a powder sublimation area of a chemical vapor deposition furnace, and a SiC nanowire template is placed in a reaction constant-temperature area of the chemical vapor deposition furnace; the preparation method comprises the following steps: reacting a nanowire in a negative pressure environment by taking H2 as a reaction gas, Ar as a diluent gas and ZrCl4 and HfCl4 as a Zr source and an Hf source, and cooling to room temperature after the reaction is finished to obtain the (Hfx, Zry) C nanowire, the components of the obtained (Hfx, Zry) C nanowire are adjustable and controllable, and compared with a SiC nanowire, the obtained (Hfx, Zry) C nanowire is high in high-temperature stability, can still keep a three-dimensional network structure in an oxidizing atmosphere at 1700 DEG C, and is converted into the (Hfx, Zry) O2 nanowire in situ. The (Hfx, Zry) C nanowire prepared by the method is low in synthesis temperature, free of catalyst, stable in preparation process and high in repeatability. The method is wide in application range and can be popularized to preparation of refractory metal carbide single-component and multi-component solid solution nanowires.

Description

Technical Field

[0001] The present invention belongs to the technical field of material preparation, and particularly relates to a method for preparing composition-tunable (Hf x , Zr y )C nanowires by a template method. Background Art

[0002] One-dimensional ceramic nanowires have high melting points, high strengths, high moduli, and high aspect ratios, and are often used for toughening composite materials and ceramic coatings, and have strong application values in fields such as aerospace. Among them, SiC nanowires are currently the most widely used one-dimensional nanomaterials. However, in an oxidation environment not lower than 1700 °C, SiC nanowires will be oxidized into molten SiO 2 , thereby causing the loss of their toughening effect.

[0003] Refractory metal carbides (such as HfC, ZrC, etc.) have relatively high melting points and relatively high melting points of their oxides, so their corresponding nanowires can still exhibit excellent toughening effects in a high-temperature oxidation environment. In addition, research shows that single-phase solid solution nanowires ((Hf x , Zr y )C nanowires) have better high-temperature stability and mechanical properties compared to single-component nanowires. Patent 1 "Zhang Yulei, Zhang Jian. A method for preparing Hf x Zr 1-x C ceramic solid solution nanowires and preparation method, CN202010821297.3[P], 2020" discloses a chemical vapor deposition method using Ni(NO 3 ) 2 as a catalyst to prepare Hf x Zr 1-x C nanowires. However, in the growth process of the nanowires by this method, the assistance of a catalyst is required, and there are metal catalyst particles at the top of the nanowires. The presence of the metal catalyst results in impurities in the nanowires, which will reduce the service performance of the composite materials and coatings toughened by them during high-temperature use. In Document 1 "M. D. Ma, X. F. Hu, H. Meng, et al. High-entropy metal carbidenanowires[J]. Cell Reports Physical Science, 2022, 3(4):100839.", molten salt-assisted carbothermal reduction method was used to prepare multi-component solid solution nanowires. The nanowires prepared by this method are relatively short in length, and Fe(NO 3 ) 3 and Ni(NO 3 ) 2Two catalysts are used, and the products prepared by this method are mostly mixtures of particles and nanowires, making it difficult to obtain nanowires with high purity. In the literature "J. Zhao, Y. Zhang, H. Chen, et al. Single-source precursor derived high-entropy metal-carbide nanowires: Microstructure and growth evolution[J]. Journal of Advanced Ceramics, 2023, 12(11): 2041-2052.", multi-component solid-solution nanowires were prepared by the precursor pyrolysis method. The preparation temperature of nanowires by this method is relatively high (1600~1700 °C), the length of the nanowires is short, the size uniformity is poor, and they are mostly bent and coiled. Catalysts are required during the preparation process. In addition, due to the relatively complex reaction mechanism during the preparation and pyrolysis of the precursor, the repeatability of the nanowire preparation process is poor. Therefore, in order to maximize the toughening effect of the nanowires and promote the application of the nanowires in a high-temperature oxygen-containing atmosphere, it is necessary to develop a nanowire preparation process with good process stability, strong repeatability, simple composition regulation, and wide application range, and prepare solid-solution nanowires with longer length, higher purity, and no catalyst. Summary of the Invention

[0004] In order to solve the problems existing in the prior art, the present invention provides a method for preparing compositionally tunable (Hf x , Zr y )C nanowires by a template method, which solves the problems of insufficient process stability, poor repeatability, the need to use catalysts during the preparation process, uneven nanowire size, and short length in the prior art.

[0005] In order to achieve the above object, in the first aspect, the present invention provides a method for preparing compositionally tunable (Hf x , Zr y )C nanowires, which is characterized by including the following steps: Mix ZrCl 4 and HfCl 4 powders in a set ratio to obtain a mixed powder. Subsequently, place the mixed powder in the powder sublimation zone of a chemical vapor deposition furnace, and place the SiC nanowire template in the reaction constant temperature zone of the chemical vapor deposition furnace; use H 2 as the reaction gas and Ar as the dilution gas, use ZrCl 4 and HfCl 4 as the Zr source and Hf source, and react on the nanowires under a negative pressure environment. After the reaction ends and the temperature drops to room temperature, (Hf x , Zr y )C nanowires are obtained.

[0006] Further, a SiC nanowire template is prepared by chemical vapor deposition, thermal evaporation, polymer conversion or sol-gel method.

[0007] Further, the preparation of the SiC nanowire template includes the following steps: Si, SiO 2 and C powder are ball-milled and mixed in a set ratio, and the mixed Si, SiO 2 and C powder are dried and placed at the bottom of a graphite crucible; The mold is placed in the mixed Si, SiO 2 and C powder, the cleaned and dried substrate is placed above the mold, and the crucible is sealed. Finally, the sealed crucible is heat-treated in an argon atmosphere for 2-4 h, and the SiC nanowires are obtained after the temperature drops to room temperature.

[0008] Further, during the preparation of the SiC nanowire template, the mass ratio of Si, SiO 2 and C powder is 1:(2~5):(1~3).

[0009] Further, the heat treatment temperature for the preparation of the SiC nanowire template is 1500°C - 1700°C.

[0010] Further, the purity of both ZrCl 4 and HfCl 4 powders is 99.9 wt%, and the particle size is 300 mesh; the molar ratio of ZrCl 4 and HfCl 4 powders is 1:30~10:1.

[0011] Further, the reaction temperature for the preparation of (Hf x , Zr y )C nanowires is 1300°C - 1400°C, the reaction time is 2-4 h, the Ar flow rate is 100~500 mL / min, and the H 2 flow rate is 500~1500 mL / min.

[0012] In the second aspect, the present invention provides an application of the above-mentioned method for preparing (Hf x , Zr y )C nanowires. By changing the reactant components, single-component solid-solution nanowires or multi-component solid-solution nanowires are prepared. The single-component solid-solution nanowires are HfC nanowires, ZrC nanowires or TaC nanowires, and the multi-component solid-solution nanowires are (Hf x , Zr y , Ta z )C nanowires, etc.

[0013] In the third aspect, a composition-tunable (Hfx , Zr y )C nanowires, prepared by the above preparation method, are three-dimensional network structures.

[0014] Meanwhile, there is also provided the use of the composition-tunable (Hf x , Zr y )C nanowires in a composite material or coating serving in an oxidation environment not lower than 1700 °C to toughen the composite material or coating.

[0015] Compared with the prior art, the present invention has at least the following beneficial effects: The present invention provides a method for preparing composition-tunable (Hf x , Zr y )C nanowires by a template method. By utilizing the reaction of active Zr and Hf atoms generated by the reaction of H 2 with ZrCl 4 and HfCl 4 with SiC nanowires at high temperature, and by adjusting the ratio of ZrCl 4 and HfCl 4 in the original powder, composition-tunable (Hf x , Zr y )C nanowires are obtained. The preparation process of the nanowires is stable and has strong repeatability; no catalyst is needed, and the introduction of impurities such as catalysts can be avoided to the greatest extent; the size of the nanowires is uniform, the diameter of the nanowires is about 200 nm, and the length is several hundred micrometers. Compared with SiC nanowires, the (Hf x , Zr y )C nanowires have stronger high-temperature stability. After oxidation at 1700 °C for 30 min, the three-dimensional network structure of SiC nanowires disappears, and the generated SiO 2 glass undergoes melting and coalescence; while the (Hf x , Zr y )C nanowires still maintain the three-dimensional network structure and are in-situ transformed into (Hf x , Zr y )O 2 nanowires. If the (Hf x , Zr y )C nanowires are introduced into a composite material or coating, in an oxidation environment not lower than 1700 °C, the toughening effect of the (Hf x , Zr y )C nanowires on the composite material and coating will be better than that of SiC nanowires. In addition, different from the smooth surface of the solid solution nanowires reported in the literature, the surface of the nanowires obtained in the present invention is relatively rough, and it is expected to further improve the interfacial bonding strength between the nanowires and the matrix, and thus play a more excellent toughening effect on the composite material or coating. Description of the Drawings

[0016] Figure 1 XRD patterns of (Hf x , Zr y )C nanowires. As can be seen from the figure, the diffraction peak positions of the nanowires are between the standard patterns of HfC and ZrC, and there is only one set of diffraction peaks, indicating that the in-situ synthesized nanowires are (Hf x , Zr y )C nanowires. In addition, the C peak in the figure mainly comes from the carbon matrix.

[0017] Figure 2 SEM images of (Hf x , Zr y )C nanowires. As can be seen from Fig. (a), the in-situ synthesized nanowires have uniform sizes, long lengths, and present a three-dimensional network structure. Fig. (b) shows that different from the reported nanowires with smooth surfaces in the literature, the surfaces of the nanowires prepared by this method are relatively rough, and it is expected to enhance the toughening effect on the composites or coatings.

[0018] Figure 3 SEM images of SiC nanowires and (Hf x , Zr y )C nanowires after oxidation at 1700 °C for 30 min. As can be seen from the figure, after oxidation at 1700 °C for 30 min, the SiC nanowires are oxidized to SiO 2 , and there is a phenomenon of melting and merging, losing the basic morphology and properties of the nanowires, indicating that the stability of SiC nanowires in an oxidation environment at 1700 °C is insufficient; while after oxidation of (Hf x , Zr y )C nanowires for 30 min, they still have the characteristics of nanowires and maintain a three-dimensional network structure, indicating that the (Hf x ,Zr y )C nanowires prepared by this method have better stability in an oxidation atmosphere than SiC nanowires. Detailed implementation manners

[0019] The present invention will be further described below in conjunction with the embodiments and the drawings: Embodiment 1: Weigh Si, SiO 2SiC powder and C powder were weighed and ball-milled for 12 h. Then the mixed powder was dried in an oven at 70 °C for 24 h. The mixed powder was placed at the bottom of a graphite crucible, and then a mold was placed in the mixed powder. Meanwhile, the cleaned and dried graphite paper (the substrate for growing nanowires) was placed above the mold. After the mixed powder and the substrate were properly placed, the crucible was sealed and then placed in an argon atmosphere at 1600 °C for heat treatment for 2 h. After the heat treatment was completed, the power was cut off and the temperature was lowered. After the temperature dropped to room temperature, SiC nanowires as templates could be obtained.

[0020] In the glove box, ZrCl was weighed according to a molar ratio of 1:1 4 and HfCl 4 powders. After manual mixing for 30 min, the mixed powder was placed in the powder sublimation zone of a chemical vapor deposition furnace. At the same time, the SiC nanowires obtained above were suspended in the reaction constant temperature zone using molybdenum wires. Then the vacuum pump was turned on. When the pressure in the furnace reached 5 kPa, the furnace body was kept under pressure. If the pressure remained unchanged after 30 min, the vacuum pump was turned on, and the temperature of the reaction zone was raised to 1300 °C at a heating rate of 5 °C / min. During this period, the Ar flow rate was 200 mL / min. After the temperature reached 1300 °C, H 2 was introduced, and the H 2 flow rate was 1000 mL / min. After reacting for 4 h, the power was cut off and the temperature was lowered. After the temperature dropped to room temperature, the nanowires were taken out, and (Hf x , Zr y )C nanowires could be obtained. The diameter of the nanowires was about 200 nm, and the ratio of Hf:Zr was about 1:7.

[0021] Example 2: Si, SiO 2 and C powder were weighed according to a mass ratio of 1:5:2 and ball-milled. The ball-milling time was 12 h. Then the mixed powder was dried in an oven at 70 °C for 24 h. The mixed powder was placed at the bottom of a graphite crucible, and then a mold was placed in the mixed powder. Meanwhile, the cleaned and dried C / C composite material (the substrate for growing nanowires) was placed above the mold. After the mixed powder and the substrate were properly placed, the crucible was sealed and then placed in an argon atmosphere at 1700 °C for heat treatment for 2 h. After the heat treatment was completed, the power was cut off and the temperature was lowered. After the temperature dropped to room temperature, SiC nanowires as templates could be obtained.

[0022] In the glove box, ZrCl was weighed according to a molar ratio of 3:1 4 and HfCl 4The powder was manually mixed for 40 min. After that, the mixed powder was placed in the powder sublimation zone of the chemical vapor deposition furnace, and at the same time, the SiC nanowires obtained above were suspended in the reaction constant temperature zone using molybdenum wires. Subsequently, the vacuum pump was turned on. When the pressure in the furnace reached 5 kPa, the pressure of the furnace body was maintained. If the pressure remained unchanged after 30 min, the vacuum pump was turned on, and the temperature of the reaction zone was raised to 1350 °C at a heating rate of 5 °C / min, during which the Ar flow rate was 300 mL / min. After the temperature reached 1300 °C, H 2 , H 2 was introduced with a flow rate of 1000 mL / min. After reacting for 4 h, the power was cut off to cool down. When the temperature dropped to room temperature, the nanowires were taken out, and (Hf x , Zr y )C nanowires could be obtained. The diameter of the nanowires was about 200 nm, and the ratio of Hf:Zr was about 1:10.

[0023] Example 3: Si, SiO 2 and C powders were weighed respectively according to the mass ratio of 1:4:3, and they were ball-milled and mixed. The ball-milling time was 12 h. Subsequently, the mixed powder was dried in an oven at 70 °C for 24 h. The mixed powder was placed at the bottom of the graphite crucible, then the mold was placed in the mixed powder, and at the same time, the cleaned and dried graphite paper (the substrate for growing nanowires) was placed above the mold. After the mixed powder and the substrate were placed well, the crucible was sealed, and then the sealed crucible was heat-treated in an argon atmosphere at 1500 °C for 4 h. After the heat treatment was completed, the power was cut off to cool down. When the temperature dropped to room temperature, the SiC nanowires used as the template could be obtained.

[0024] In the glove box, ZrCl 4 and HfCl 4 powders were weighed respectively according to the molar ratio of 1:3, and they were manually mixed for 30 min. After that, the mixed powder was placed in the powder sublimation zone of the chemical vapor deposition furnace, and at the same time, the SiC nanowires obtained above were suspended in the reaction constant temperature zone using molybdenum wires. Subsequently, the vacuum pump was turned on. When the pressure in the furnace reached 5 kPa, the pressure of the furnace body was maintained. If the pressure remained unchanged after 30 min, the vacuum pump was turned on, and the temperature of the reaction zone was raised to 1300 °C at a heating rate of 5 °C / min, during which the Ar flow rate was 300 mL / min. After the temperature reached 1300 °C, H 2 , H 2 was introduced with a flow rate of 1000 mL / min. After reacting for 4 h, the power was cut off to cool down. When the temperature dropped to room temperature, the nanowires were taken out, and (Hf x , Zr y )C nanowires could be obtained. The diameter of the nanowires was about 200 nm, and the ratio of Hf:Zr was about 1:2.

[0025] Example 4: Weigh Si, SiO 2 and C powder according to the mass ratio of 1:5:2, and ball-mill and mix them. The ball-milling time is 12 h, and then dry the mixed powder in an oven at 70 °C for 24 h. Place the mixed powder at the bottom of a graphite crucible, then place the mold in the mixed powder, and at the same time place the cleaned and dried graphite paper (the substrate for growing nanowires) above the mold. After placing the mixed powder and the substrate, seal the crucible, and then place the sealed crucible in an argon atmosphere at 1700 °C for heat treatment for 2 h. After the heat treatment is completed, cut off the power and let it cool down. After the temperature drops to room temperature, SiC nanowires serving as a template can be obtained.

[0026] Weigh ZrCl 4 and HfCl 4 powders in a glove box according to the molar ratio of 1:30, manually mix them for 30 min, then place the mixed powder in the powder sublimation zone of a chemical vapor deposition furnace, and at the same time use molybdenum wire to suspend the SiC nanowires obtained above in the reaction constant temperature zone. Then turn on the vacuum pump. When the pressure in the furnace is 5 kPa, keep the pressure of the furnace body. If the pressure remains unchanged after 30 min, turn on the vacuum pump and raise the temperature of the reaction zone to 1300 °C at a heating rate of 5 °C / min. During this period, the Ar flow rate is 100 mL / min. After the temperature rises to 1300 °C, introduce H 2 , and the H 2 flow rate is 1500 mL / min. After reacting for 4 h, cut off the power and let it cool down. When the temperature drops to room temperature, take out the nanowires, and (Hf x , Zr y )C nanowires can be obtained. The diameter of the nanowires is about 200 nm, and the ratio of Hf:Zr is about 12:1.

[0027] Example 5: Weigh Si, SiO 2 and C powder according to the mass ratio of 1:4:3, and ball-mill and mix them. The ball-milling time is 12 h, and then dry the mixed powder in an oven at 70 °C for 24 h. Place the mixed powder at the bottom of a graphite crucible, then place the mold in the mixed powder, and at the same time place the cleaned and dried graphite paper (the substrate for growing nanowires) above the mold. After placing the mixed powder and the substrate, seal the crucible, and then place the sealed crucible in an argon atmosphere at 1600 °C for heat treatment for 2 h. After the heat treatment is completed, cut off the power and let it cool down. After the temperature drops to room temperature, SiC nanowires serving as a template can be obtained.

[0028] Weigh ZrCl 4 and HfCl4 The powder was manually mixed for 30 min. After that, the mixed powder was placed in the powder sublimation zone of a chemical vapor deposition furnace, and at the same time, the SiC nanowires obtained above were suspended in the reaction constant temperature zone using molybdenum wires. Subsequently, a vacuum pump was turned on. When the pressure in the furnace reached 5 kPa, the furnace body was kept under pressure. If the pressure remained unchanged after 30 min, the vacuum pump was turned on, and the temperature of the reaction zone was raised to 1300 °C at a heating rate of 5 °C / min, during which the Ar flow rate was 500 mL / min. After the temperature reached 1300 °C, H 2 , H 2 was introduced with a flow rate of 500 mL / min. After reacting for 4 h, the power was cut off to cool down. When the temperature dropped to room temperature, the nanowires were taken out, and (Hf x , Zr y )C nanowires could be obtained. The diameter of the nanowires was about 200 nm, and the ratio of Hf:Zr was about 1:14.

[0029] Example 6: Si, SiO 2 and C powders were weighed respectively according to a mass ratio of 1:4:2, and they were ball-milled and mixed for 12 h. Then, the mixed powder was dried in an oven at 70 °C for 24 h. The mixed powder was placed at the bottom of a graphite crucible, and then a mold was placed in the mixed powder. At the same time, the cleaned and dried graphite paper (the substrate for growing nanowires) was placed above the mold. After the mixed powder and the substrate were placed properly, the crucible was sealed, and then the sealed crucible was heat-treated in an argon atmosphere at 1600 °C for 2 h. After the heat treatment was completed, the power was cut off to cool down. When the temperature dropped to room temperature, SiC nanowires as templates could be obtained.

[0030] ZrCl 4 and HfCl 4 powders were weighed respectively in a glove box according to a molar ratio of 1:1 and manually mixed for 30 min. After that, the mixed powder was placed in the powder sublimation zone of a chemical vapor deposition furnace, and at the same time, the SiC nanowires obtained above were suspended in the reaction constant temperature zone using molybdenum wires. Subsequently, a vacuum pump was turned on. When the pressure in the furnace reached 5 kPa, the furnace body was kept under pressure. If the pressure remained unchanged after 30 min, the vacuum pump was turned on, and the temperature of the reaction zone was raised to 1400 °C at a heating rate of 5 °C / min, during which the Ar flow rate was 200 mL / min. After the temperature reached 1400 °C, H 2 , H 2 was introduced with a flow rate of 1000 mL / min. After reacting for 2 h, the power was cut off to cool down. When the temperature dropped to room temperature, the nanowires were taken out, and (Hf x , Zr y )C nanowires could be obtained. The diameter of the nanowires was about 200 nm, and the ratio of Hf:Zr was about 1:2.

[0031] Comparative Example 1: The difference between this comparative example and the foregoing embodiment is that the reaction temperature of the nanowires is relatively low, and the nanowires cannot be completely solid-soluted to form (Hf x , Zr y )C nanowires. Weigh Si, SiO 2 and C powder according to the mass ratio of 1:4:2, and ball-mill and mix them. The ball-milling time is 12 h, and then the mixed powder is dried in an oven at 70 °C for 24 h. Place the mixed powder at the bottom of a graphite crucible, then place the mold in the mixed powder, and at the same time place the cleaned and dried graphite paper (the substrate for growing nanowires) above the mold. After placing the mixed powder and the substrate, seal the crucible, and then place the sealed crucible in an argon atmosphere at 1600 °C for heat treatment for 2 h. After the heat treatment is completed, cut off the power supply and cool down. After the temperature drops to room temperature, the SiC nanowires used as the template can be obtained.

[0032] Weigh ZrCl 4 and HfCl 4 powders according to the molar ratio of 1:3 in a glove box. After manually mixing for 30 min, place the mixed powder in the powder sublimation zone of a chemical vapor deposition furnace, and at the same time use molybdenum wire to suspend the above-obtained SiC nanowires in the reaction constant temperature zone. Then turn on the vacuum pump. When the pressure in the furnace is 5 kPa, perform a pressure holding treatment on the furnace body. If the pressure remains unchanged after 30 min, turn on the vacuum pump and raise the temperature of the reaction zone to 1200 °C at a heating rate of 5 °C / min. During this period, the Ar flow rate is 200 mL / min. After the temperature rises to 1300 °C, introduce H 2 , and the H 2 flow rate is 1000 mL / min. After reacting for 4 h, cut off the power supply and cool down. When the temperature drops to room temperature, take out the nanowires. The obtained nanowires are not (Hf x , Zr y )C nanowires, but a mixture of nanowires composed of Hf x Si y , Zr x Si y and HfC and other phases.

[0033] Comparative Example 2: The difference between this comparative example and the foregoing embodiment is that the content of H 2 is insufficient during the preparation of the nanowires, and there are more silicides in the nanowires. Weigh Si, SiO 2C powder, and ball-mill and mix them. The ball-milling time is 12 h. Subsequently, dry the mixed powder in an oven at 70 °C for 24 h. Place the mixed powder at the bottom of a graphite crucible, then place the mold in the mixed powder, and at the same time, place the cleaned and dried graphite paper (the substrate for growing nanowires) above the mold. After placing the mixed powder and the substrate, seal the crucible, and then place the sealed crucible in an argon atmosphere at 1700 °C for heat treatment for 2 h. After the heat treatment is completed, cut off the power supply to cool down. After the temperature drops to room temperature, SiC nanowires as templates can be obtained.

[0034] Weigh ZrCl 4 and HfCl 4 powders in a glove box at a molar ratio of 1:1, manually mix them for 30 min, then place the mixed powder in the powder sublimation zone of a chemical vapor deposition furnace, and at the same time, use molybdenum wire to suspend the SiC nanowires obtained above in the reaction constant temperature zone. Subsequently, turn on the vacuum pump. When the pressure in the furnace is 5 kPa, perform a pressure holding treatment on the furnace body. If the pressure remains unchanged after 30 min, turn on the vacuum pump and increase the temperature of the reaction zone to 1300 °C at a heating rate of 5 °C / min. During this period, the Ar flow rate is 100 mL / min. After the temperature rises to 1300 °C, introduce H 2 , and the H 2 flow rate is 100 mL / min. After reacting for 4 h, cut off the power supply to cool down. When the temperature drops to room temperature, take out the nanowires. In the obtained (Hf x , Zr y )C nanowires, in addition to containing (Hf x , Zr y )C, there are also Hf x Si y , Zr x Si y .

[0035] Reference Figure 1 , the peak positions of the diffraction peaks of the nanowires are between the standard spectra of HfC and ZrC, and there is only one set of diffraction peaks, indicating that the in-situ reaction obtained nanowires are (Hf x , Zr y )C nanowires. In addition, Figure 1 the C peak in Figure 2 mainly comes from the carbon matrix; refer to the SEM photos of (Hf x , Zr y )C nanowires shown in Figure 2 . As can be seen from Figure (a) in Figure 2 , the in-situ reaction obtained nanowires have uniform sizes, are relatively long, and present a three-dimensional network structure. Figure (b) shows that different from the reported nanowires with smooth surfaces in the literature, the nanowires prepared by this method have relatively rough surfaces, and it is expected that the toughening effect on composites or coatings can be enhanced; refer toFigure 3 The SEM images of the shown SiC nanowires and (Hf x , Zr y )C nanowires after oxidation at 1700 °C for 30 min. As can be seen from the figure, after oxidation at 1700 °C for 30 min, the SiC nanowires are oxidized to SiO 2 , and there is a phenomenon of melting and merging, losing the basic morphology and characteristics of the nanowires, indicating that the stability of SiC nanowires in the oxidation environment at 1700 °C is insufficient; while after the (Hf x , Zr y )C nanowires are oxidized for 30 min, they still have the characteristics of nanowires and maintain a three-dimensional network structure, indicating that the (Hf x , Zr y )C nanowires prepared by this method have better stability in the oxidation atmosphere than SiC nanowires.

[0036] The present invention provides a method for preparing (Hf x , Zr y )C nanowires by a template method. First, SiC nanowire templates are prepared by thermal evaporation method, and then by chemical vapor deposition method, using ZrCl 4 and HfCl 4 react with H 2 to generate active Zr atoms and Hf atoms, which react with SiC nanowires to convert the SiC nanowires into (Hf x , Zr y )C nanowires. The (Hf x , Zr y )C nanowires prepared by the above method have adjustable composition. Compared with SiC nanowires, they have strong high-temperature stability, can still maintain a three-dimensional network structure in the oxidation atmosphere at 1700 °C, and are in-situ transformed into (Hf x , Zr y )O 2 nanowires. The (Hf x , Zr y )C nanowires prepared by this method have a low synthesis temperature, do not require the use of catalysts, have a stable preparation process, and strong repeatability. This method has a wide range of applications and can be extended to the preparation of refractory metal carbide single-component and multi-component solid solution nanowires.

[0037] Finally, it should be noted that: the above embodiments are only used to illustrate the technical solutions of the present invention, not to limit it; although the present invention has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that: they can still modify the technical solutions recorded in the foregoing embodiments, or perform equivalent replacements on some or all of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. One component can be regulated (Hf x , Zr y ) A method for preparing C nanowires, characterized in that: The following steps are involved: ZrCl4 and HfCl4 powders were mixed in a set ratio to obtain a mixed powder, and then the mixed powder was placed in a powder sublimation zone of a chemical vapor deposition furnace, and a SiC nanowire template was placed in a reaction constant temperature zone of a chemical vapor deposition furnace; H2 was used as a reaction gas, Ar was used as a diluent gas, and ZrCl4 and HfCl4 were used as Zr sources and Hf sources, respectively, and the nanowires were reacted under a negative pressure environment, and (Hf x ,Zr y )C nanowires.

2. According to claim 1, the composition can be adjusted (Hf x , Zr y ) A method for preparing C nanowires, characterized in that: The SiC nanowire template is prepared by chemical vapor deposition, thermal evaporation, polymer conversion or sol-gel method.

3. According to claim 1, the composition can be adjusted (Hf x , Zr y ) A method for preparing C nanowires, characterized in that: The preparation of the SiC nanowire template comprises the following steps: mixing Si, SiO2 and C powders by ball milling according to a set ratio, and drying the mixed Si, SiO2 and C powders and placing them at the bottom of a graphite crucible; The mold is placed in a mixture of Si, SiO2 and C powders, the cleaned and dried substrate is placed on top of the mold, and the crucible is sealed. Finally, the sealed crucible is heat treated in an argon atmosphere for 2-4 hours, and SiC nanowires are obtained when the temperature drops to room temperature.

4. According to claim 1, the composition can be adjusted (Hf x , Zr y ) A method for preparing C nanowires, characterized in that: When preparing SiC nanowire templates, the thermal evaporation method was used, and the mass ratio of Si, SiO2 and C powder was 1:(2~5):(1~3).

5. According to claim 1, the composition can be adjusted (Hf x , Zr y ) A method for preparing C nanowires, characterized in that: The preparation heat treatment temperature of the SiC nanowire template is 1500°C-1700°C.

6. According to claim 1, the composition can be adjusted (Hf x , Zr y ) A method for preparing C nanowires, characterized in that: The purity of ZrCl4 and HfCl4 powders is 99.9wt%, and the particle size is 300 mesh; the molar ratio of ZrCl4 and HfCl4 powders is 1:30~10:

1.

7. According to claim 1, the composition can be adjusted (Hf x , Zr y ) A method for preparing C nanowires, characterized in that: Preparation (Hf x , Zr y )The reaction temperature of C nanowires is 1300℃-1400℃, the reaction time is 2-4h, the Ar flow rate is 100~500mL / min, and the H2 flow rate is 500~1500mL / min.

8. The method according to any one of claims 1 to 7 x , Zr y ) Application of the method for preparing C nanowires, characterized in that, By changing the reactant components, single-component solid solution nanowires or multi-component solid solution nanowires are prepared. The single-component solid solution nanowires are HfC nanowires, ZrC nanowires or TaC nanowires, etc., and the multi-component solid solution nanowires are (Hf x , Zr y , z )C nanowires, etc.

9. A compositionally adjustable (Hf x , Zr y )C nanowire, characterized in that The preparation method according to any one of claims 1 to 8 is used to obtain the three-dimensional network structure.

10. The composition of claim 9 wherein the composition is adjustable (Hf x , Zr y ) Application of C nanowires, characterized in that, It is used to add into composite materials or coatings serving in an oxidizing environment of not less than 1700°C and to toughen the composite materials or coatings.

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