High-temperature-resistant zirconium carbide whisker as well as preparation method and application thereof

Abstract

The invention discloses a high-temperature-resistant zirconium carbide whisker as well as a preparation method and application thereof, and belongs to the field of new material preparation. The preparation method of the high-temperature-resistant zirconium carbide whisker comprises the following steps: uniformly mixing a zirconium-containing organic precursor, rare earth salt and nickel acetate in an organic solvent to obtain a reactant precursor raw material; drying, grinding and sieving the obtained reactant precursor raw material; and carrying out heating reaction on the dried, ground and sieved reactant precursor raw material in a protective atmosphere to obtain the zirconium carbide whisker. The rare earth salt is added in the reaction process to replace a traditional NaF additive, so that the rare earth salt can serve as a fluxing additive to promote growth of the zirconium carbide whiskers and improve the crystal form stability of the zirconium carbide whiskers, and meanwhile, generation of substances harmful to human bodies and the environment in the preparation process can be avoided; and the influence of the addition of alkali metal Na on the high temperature resistance of the zirconium carbide whisker is effectively avoided.

Description

Technical Field

[0001] The present invention belongs to the technical field of new material preparation, and particularly relates to a high-temperature resistant zirconium carbide whisker, a preparation method thereof and an application thereof. Background Art

[0002] ZrC belongs to ultra-high temperature ceramics (UHTCs), and has characteristics such as a high melting point (about 3693K), high hardness (25.5Gpa), high modulus, etc. At the same time, it also has excellent wear resistance, ablation resistance, and good electrical and thermal conductivity and other properties. Therefore, ZrC ceramics have broad application prospects in the fields of ultra-high temperature ceramics, superhard ceramics, thermal protection, thermal structure materials, electrode materials, nuclear power materials, etc. In addition to the excellent intrinsic properties of zirconium carbide ceramics, zirconium carbide whiskers (ZrCw) also have the ultra-high strength close to the theoretical limit of one-dimensional single crystal materials and their unique geometric characteristics, so that they have more excellent properties and new characteristics in mechanics, electricity, optics, etc. Zirconium carbide whiskers can be used as ideal reinforcing phases for composite materials to improve the mechanical properties, thermal conductivity, electrical conductivity, electromagnetic properties, etc. of composite materials.

[0003] At present, there are few methods for preparing zirconium carbide whiskers, mainly including carbothermal reduction method and chemical vapor deposition method. The literature "Study on the synthesis and growth mechanisms of the refractory ZrC whiskers. International Journal of Refractory Metals and Hard Materials 42(2014):116 - 119" discloses a method for preparing ZrC whiskers by carbothermal reduction method, using ZrO2, C, Ni, NaF as raw materials for ball milling and preparing ZrC whiskers at 1500°C in an Ar atmosphere. The morphology of the ZrC whiskers prepared by this method mainly presents two types: cylindrical and prismatic. However, the prepared whiskers are not only rough on the surface and very short, but also there are a large number of agglomerated particles. The literature "Carbothermal reduction synthesis of near-stoichiometric ZrC whiskers via VLS and SLS growth mechanism. Ceramics International 46.17(2020):27463 - 27468" also discloses a method for preparing ZrC whiskers by carbothermal reduction method, using ZrO2, C, Ni, NaF as raw materials for ball milling and preparing ZrC whiskers at 1500°C in an Ar atmosphere. However, the prepared zirconium carbide whiskers are disorderly, of different sizes, and highly toxic fluorine gas will be generated.

[0004] The Chinese patent document with the publication number CN 108560058 A discloses a method for preparing zirconium carbide whiskers by using zirconium tetrachloride as the zirconium source and mesophase pitch as the carbon source and adopting the isothermal and isobaric chemical vapor deposition method. However, the zirconium tetrachloride raw material used in this method is volatile at high temperatures, the reaction is difficult to control, and a large amount of toxic substances will be generated by the mesophase pitch at high temperatures. The Chinese patent document with the publication number CN 114032607 A discloses a method for catalytically guiding the preparation of single zirconium carbide whiskers by using zirconium carbide seeds. However, sodium fluoride is also introduced in this method, and toxic substances will be generated during the preparation process, thus causing damage to the human body and the environment.

[0005] In summary, the existing preparation methods usually need to introduce fluorine elements, pitch or organic gases during the preparation of zirconium carbide whiskers, resulting in the generation of toxic substances such as fluorine gas and alkane gases during the preparation process. The generation of these toxic substances has caused great damage to human health and the environment. In addition, there are also problems such as high equipment requirements, complex operations, long experimental cycles and low yields in the preparation of zirconium carbide whiskers by chemical vapor deposition method, which are difficult to industrialize and commercialize; while in the preparation by carbothermal reduction method, additives containing alkali metals are introduced, and the introduction of alkali metals will have a greater impact on the high-temperature resistance performance of the prepared zirconium carbide whiskers.

[0006] Therefore, it is of great significance to develop a new preparation method of zirconium carbide whiskers to solve the above problems existing in the existing preparation processes. Summary of the Invention

[0007] The purpose of the present invention is to provide a preparation method of high-temperature resistant zirconium carbide whiskers, so as to solve the problems existing in the existing preparation processes, such as generating toxic gases, needing to introduce alkali metals, which are likely to have an adverse effect on the high-temperature resistance performance of zirconium carbide whiskers, or the preparation process is complex and not conducive to industrial promotion and application.

[0008] The present invention also provides zirconium carbide whiskers prepared by the above preparation process and the application of the prepared zirconium carbide whiskers in metal matrix, resin matrix or ceramic matrix composites.

[0009] The first aspect of the present invention provides a preparation method of high-temperature resistant zirconium carbide whiskers, including:

[0010] Mixing a zirconium-containing organic precursor, a rare earth salt and nickel acetate uniformly in an organic solvent to obtain a reactant precursor raw material;

[0011] Drying, grinding and sieving the obtained reactant precursor raw material;

[0012] Heating the reactant precursor raw material after drying, grinding and sieving from room temperature to 1400 - 1600 °C under a protective atmosphere for reaction, and zirconium carbide whiskers are obtained.

[0013] In the present invention, a zirconium-containing organic precursor, a nickel salt, and a rare earth salt are added together to an organic solvent, and then the obtained reactant precursor is dried, ground, and sieved and then calcined to obtain high-temperature-resistant zirconium carbide whiskers. The specific reaction process is as follows: In the early stage of calcination, the reactant precursor first undergoes a thermal decomposition reaction to generate an oxide (m-ZrO2) and highly active amorphous carbon; as the temperature rises, m-ZrO2 (monoclinic phase) gradually transforms into t-ZrO2 (tetragonal phase) with higher lattice symmetry; in the later stage of calcination, t-ZrO2 and amorphous carbon continue to undergo a carbothermal reaction to obtain a carbide (ZrC).

[0014] In the present invention, by adding a rare earth salt instead of the traditional NaF additive during the reaction process, it can not only promote the growth of zirconium carbide whiskers and improve the stability of the crystal form of zirconium carbide whiskers as a flux additive, but also avoid the generation of harmful substances to the human body and the environment during the preparation process, and effectively avoid the influence of the addition of alkali metal Na on the high-temperature resistance performance of zirconium carbide whiskers.

[0015] It should be noted that the control of the calcination (pyrolysis) temperature has a great influence on the formation and morphology of zirconium carbide whiskers. It affects the generation amount, morphology, and growth rate of ZrCw by influencing the cracking rate of the precursor, the reaction activity of the additive, and the kinetic and thermodynamic behaviors affecting the reaction process.

[0016] When the calcination temperature is low, the transformation of m-ZrO2 to t-ZrO2 is insufficient or ZrC whiskers cannot be synthesized; but when the temperature is too high, it is easy to cause whisker adhesion, coarsening, and even sintering phenomena. When the pyrolysis temperature is too low, the system energy is not enough to reach the threshold of the carbothermal reduction reaction, and the activity of the additive (rare earth salt) is low, resulting in the product mainly being ZrO2 and amorphous carbon generated by the pyrolysis of PZC; as the temperature rises, the activity of the additive increases, which not only promotes the dissolution of ZrO2 and C in the molten pool, but also reduces the activation energy barrier of the carbothermal reduction reaction, thereby driving the nucleation and growth of ZrCw. But when the pyrolysis temperature is too high, it will cause ZrCw to agglomerate into blocks. Therefore, considering the reaction efficiency and product morphology control, it is preferably to control the pyrolysis temperature at 1400-1600 °C, more preferably 1400-1500 °C, and further preferably 1400-1450 °C, so as to obtain well-dispersed ZrCw while ensuring a high conversion rate.

[0017] In addition, the preparation method of the present invention can also effectively reduce the formation temperature of ZrC whiskers (the formation temperature calculated by thermodynamic theory is 1660 °C). The reduction in the temperature of the carbothermal reduction reaction to form ZrC is mainly due to the following multiple effects: The nano-droplets (Ni-La alloy droplets) formed by the additive at high temperature provide a unique liquid-phase reaction microenvironment for the reactants, which can provide a molten pool to dissolve ZrO2 and amorphous carbon, thus significantly reducing the reaction activation energy and accelerating the carbothermal reaction rate; The molten rare-earth salts show excellent solubility in ZrO2 and amorphous carbon; The atomic diffusion coefficient of the reactants in the liquid phase is increased by 2-3 orders of magnitude compared with that in the solid phase, thereby promoting the carbothermal reaction.

[0018] Furthermore, the mass of the rare-earth salt and nickel acetate respectively accounts for 2% - 6% and 1% - 5% of the mass of the zirconium-containing organic precursor. It should be noted that the addition amount of the rare-earth salt plays an important role in ensuring the formation amount of zirconium carbide whiskers. When the addition amount of the rare-earth salt is small, the formation amount of zirconium carbide whiskers is small, but when its addition amount is too large, the whiskers will be coarsened and the yield will decrease due to melting adhesion. More preferably, the mass of the rare-earth salt accounts for 2% - 4% of the mass of the zirconium-containing organic precursor.

[0019] Furthermore, the zirconium-containing organic precursor includes but is not limited to the acetylacetonate zirconium precursor PZC. The PZC is preferably an organic zirconium synthesized directly in one step by adding salicyl alcohol when preparing poly(acetylacetonato)zirconium by reacting acetylacetone with zirconium oxychloride.

[0020] Furthermore, the rare-earth salt is a soluble lanthanum salt or cerium salt, and more preferably lanthanum chloride is used.

[0021] Furthermore, the organic solvent is xylene, p-xylene or acetone.

[0022] Furthermore, the step of uniformly mixing the zirconium-containing organic precursor, the rare-earth salt and nickel acetate in the organic solvent is specifically to make each raw material uniformly mixed by magnetic stirring. The magnetic stirring speed is 250 - 500 r / min and the time is 1 - 4 h.

[0023] Furthermore, the drying temperature is 80 - 120 °C and the time is 600 - 900 min; and / or the step of grinding and sieving is specifically to sieve using a 100-mesh sieve.

[0024] Furthermore, the dried, ground, and sieved reactant precursor raw materials are heated from room temperature to 1400 - 1600 °C under a protective atmosphere for reaction, with the heating rate controlled at 1.5 - 2.5 °C / min and the pyrolysis holding time at 1.5 - 2.5 h. Among them, by optimizing the control of the heating rate and reaction time, not only can the transformation of m-ZrO2 to t-ZrO2 and the formation reaction of ZrC whiskers proceed sufficiently, but also the aspect ratio of the synthesized ZrC whiskers can be effectively controlled to prevent the zirconium carbide whiskers from being too thick. Especially when the reaction holding time is extended, not only will the morphology of the zirconium carbide whiskers evolve from slender to thick, but also the phenomenon of adhesion between the whiskers will occur. Therefore, it is further preferably to control the pyrolysis reaction time to 2 h.

[0025] Furthermore, the protective atmosphere is an Ar atmosphere with a gas flow rate of 50 - 200 cc / min.

[0026] The second aspect of the present invention also provides a high-temperature resistant zirconium carbide whisker prepared by the method according to the first aspect of the present invention.

[0027] Furthermore, the diameter of the zirconium carbide whisker is 50 - 200 nm, and the length is 2 - 50 μm.

[0028] The third aspect of the present invention also provides an application of the high-temperature resistant zirconium carbide whisker prepared by the method according to the first aspect of the present invention in metal matrix, resin matrix, or ceramic matrix composites. By adding zirconium carbide whiskers as a reinforcing phase in the above composites, they can be reinforced and toughened.

[0029] Furthermore, the present invention also provides an application of the high-temperature resistant zirconium carbide whisker or the composite material containing the whisker in the fields of superhard ceramics, electrode materials, nuclear power materials, etc.

[0030] Adopting the technical solution provided by the present invention, compared with the prior art, the following beneficial effects can be achieved:

[0031] (1) By adding rare earth salts during the preparation process of zirconium carbide whiskers, the present invention can not only promote the formation of zirconium carbide whiskers, reduce the generation of harmful substances to the human body and the environment during the preparation process, but also effectively avoid the influence of the addition of alkali metal Na on the high-temperature resistance performance of zirconium carbide whiskers. Moreover, the entire preparation process is simple in operation, short in production cycle, low in cost, and convenient for industrial promotion and application.

[0032] (2) The present invention further optimizes the control of the addition amount of rare earth salts and specific preparation process parameters such as reaction temperature and reaction time, which is not only beneficial to promoting the formation amount of zirconium carbide whiskers, but also can prevent the aspect ratio of zirconium carbide whiskers from being too large and the occurrence of adhesion phenomenon, and ensure the uniformity of their dimensions.

[0033] (3) Since rare earth elements are introduced in the present invention, it can play a role in stabilizing the crystal form during the preparation process; at the same time, due to its high melting point, the zirconium carbide whiskers can have both high-temperature strength and high-temperature ablation resistance while improving the mechanical properties of the composite material, so as to meet the requirements for use of the composite material in harsh service environments. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Figure 1 Scanning pictures of the products obtained in Examples 1-3 and Comparative Example 1;

[0035] Figure 2 For Figure 1 EDS analysis results of potential 1 and 2 in (d); (a) potential 1, (b) potential 2;

[0036] Figure 3 TEM analysis results of the product obtained in Example 1: (a) low-magnification TEM image, (b) enlarged TEM image of area A, (c) enlarged TEM image of area B, (d) diffraction pattern, (e) HAADF image and Mapping image;

[0037] Figure 4 XRD patterns of the products obtained in Example 2, Example 4 and Comparative Example 2;

[0038] Figure 5 Scanning pictures of the products obtained in Example 2, Example 4 and Comparative Example 2; (a, b) 1300 °C, (c, d) 1400 °C, (e, f) 1500 °C;

[0039] Figure 6 For Figure 5 EDS analysis results of different positions in; (a) position 1, (b) position 2, (c) position 3 and (d) position 4;

[0040] Figure 7 Comparison of scanning pictures of products under different pyrolysis reaction times; (a, b) 1 h, (c, d) 1.5 h, (e, f) 2 h, (g, h) 2.5 h;

[0041] Figure 8 For Figure 7 EDS analysis results of different positions in; (a) position 1, (b) position 2. DETAILED DESCRIPTION OF THE INVENTION

[0042] To further understand the content of the present invention, the present invention will be described in detail below in conjunction with specific embodiments.

[0043] Example 1

[0044] The preparation method of the high-temperature resistant zirconium carbide whiskers in this embodiment comprises the following steps:

[0045] 1) Weigh the zirconium-containing organic precursor (PZC), lanthanum chloride (LaCl3), and nickel acetate (Ni(CH3COO)2) according to a mass ratio of 1:4%:1% for standby;

[0046] 2) Add the weighed raw materials into xylene, and use a magnetic stirrer to stir and mix evenly. The stirring speed is 300 r / min, and the time is 2 h to obtain a uniformly mixed reactant precursor raw material;

[0047] 3) Put the uniformly mixed reactant precursor raw material into an oven and dry it at a temperature of 80 °C for 600 min;

[0048] 4) Grind the dried powder and screen it with a 100-mesh sample sieve to obtain a powder with uniform particle size;

[0049] 5) Put the sieved powder into a crucible, send it into a tube furnace, heat it from room temperature to 1400 °C at a heating rate of 2 °C / min, and calcine it for 2 h under the protection of Ar with a gas flow rate of 50 cc / min to obtain the high-temperature resistant zirconium carbide whiskers.

[0050] Example 2

[0051] The preparation method of the high-temperature resistant zirconium carbide whiskers in this embodiment is basically the same as that shown in Example 1. The main difference is that: in this embodiment, the addition amount of lanthanum chloride (LaCl3) accounts for 2% of the mass of the zirconium-containing organic precursor (PZC). Due to the relatively small addition amount of lanthanum chloride (LaCl3), the generation amount of ZrCw is significantly less than that in Example 1.

[0052] Example 3

[0053] The preparation method of the high-temperature resistant zirconium carbide whiskers in this embodiment is basically the same as that shown in Example 1. The main difference is that: in this embodiment, the addition amount of lanthanum chloride (LaCl3) accounts for 6% of the mass of the zirconium-containing organic precursor (PZC).

[0054] Comparative Example 1

[0055] The preparation method of the high-temperature resistant zirconium carbide whiskers in this comparative example is basically the same as that in Example 1. The main difference is that: in this comparative example, lanthanum chloride (LaCl3) is not added.

[0056] As Figure 1 shown are the SEM pictures of the products obtained in Examples 1-3 and Comparative Example 1 respectively, where Figure 1In a, b are SEM images of the products in the comparative example, c, d are SEM images of the products in Example 2, e, f are SEM images of the products in Example 1, and g, h are SEM images of the products in Example 3. Combining Figure 1 It can be seen that when the addition amount of LaCl3 is 0 wt%, the product is ZrO2. Since the participation of LaCl3 does not reduce the reaction activation energy of the system, the conditions for the carbothermal reaction to generate ZrCw are not achieved. As the addition amount of LaCl3 increases from 2 wt% to 4 wt%, the yield of ZrCw gradually increases; however, when the addition amount of LaCl3 is 6 wt%, a melting adhesion phenomenon occurs, resulting in the coarsening of ZrCw and a decrease in the yield. Among them, Figure 1 The EDS analysis results of the points 1 and 2 shown in (d) are as Figure 2 shown.

[0057] Taking Example 1 as an example, the obtained product was analyzed by TEM, and the results are as Figure 3 shown. It can be seen from the figure that the product presents a typical linear growth morphology, the whisker diameter shows a gradient change (200 - 400 nm), and the length reaches the micron level. There are obvious heterogeneous attachments on the surface of ZrCw. High-resolution transmission electron microscopy analysis (HRTEM, Figure 3 b) shows that the A region of the whisker presents clear lattice fringes, and the measured interplanar spacing is about 0.234 nm, which is consistent with the standard spacing of the ZrC(200) crystal plane, indicating that the whisker preferentially grows along the

[200] crystal direction. In addition, an interplanar spacing of 0.363 nm is observed in the B region of the whisker ( Figure 3 c), corresponding to the m-ZrO2(100) crystal plane, indicating that there is an unreacted ZrO2 phase remaining on the surface of the whisker. The selected area electron diffraction pattern (SAED, Figure 3 d) shows a regular arrangement of diffraction spots, confirming that ZrCw is a single crystal structure; the existence of secondary diffraction spots is attributed to the polycrystalline diffraction of the residual ZrO2. Combining HAADF-STEM (high-angle annular dark-field scanning transmission electron microscope image) and Mapping (element distribution) analysis, it is further verified that the obtained whiskers are ZrCw.

[0058] Example 4

[0059] The preparation method of the high-temperature resistant zirconium carbide whiskers in this example is basically the same as that shown in Example 2, and the main difference is that: the calcination temperature in this example is 1500 °C.

[0060] Comparative Example 2

[0061] The preparation method of the high-temperature resistant zirconium carbide whiskers in this comparative example is basically the same as that in Example 2, and the main difference is that: the calcination temperature in this comparative example is 1300 °C.

[0062] The XRD patterns of the products obtained in Example 2, Example 4 and Comparative Example 2 are as follows Figure 4 As shown, it can be seen from the figure that only the diffraction peaks of m-ZrO2 and t-ZrO2 are detected in the product at 1300 °C. Among them, the diffraction peak intensity of m-ZrO2 is higher, while the diffraction peak intensity of t-ZrO2 is lower, indicating that a large amount of m-ZrO2 has not been converted into t-ZrO2. When the temperature is raised to 1400 °C, the diffraction peak heights of m-ZrO2 and t-ZrO2 in the product decrease, and their contents decrease. At the same time, a diffraction peak of ZrC with high intensity appears, indicating that the transformation of m-ZrO2 to t-ZrO2 and the carbothermal reduction reaction of t-ZrO2 have not been completely completed at this temperature. When the temperature is further raised to 1500 °C, the diffraction peak of t-ZrO2 in the product disappears, and only a small amount of diffraction peaks of m-ZrO2 remain besides the ZrC diffraction peak, indicating that ZrO2 and C have almost completely reacted.

[0063] The scanning pictures of the products obtained in Example 2, Example 4 and Comparative Example 2 are as follows Figure 5 As shown, it can be seen from the figure that the pyrolysis products at 1300 °C are mainly irregularly shaped and sized particles, and no whisker structure is observed. Combining with Figure 4 , it can be judged that the particles are composed of m-ZrO2 and t-ZrO2, indicating that the pyrolysis temperature of 1300 °C is not sufficient to promote the nucleation and growth of ZrCw. When the pyrolysis temperature is raised to 1400 °C, dispersed whiskers are observed in the product, and most of the whiskers are linear. Combining with the EDS analysis in Figure 6 , it shows that C, Zr, O, La and trace amounts of Ni elements are detected at point 1. The atomic content of C is much higher than that of Zr, indicating that the whiskers are ZrCw. The high C atomic content is due to the free carbon that has not completely reacted during the pyrolysis of PZC. At the same time, ZrCw extends from spherical particles. The EDS results show that the elemental composition of the spherical particles is the same as that of ZrCw, but the contents of La and Ni elements are much higher than those at point 1. It is speculated that the spherical particles are the molten pools for the nucleation and growth of whiskers, which promote the outward growth of whiskers. When the pyrolysis temperature is further raised to 1500 °C, whiskers with larger lengths are formed in the product, and the whiskers with smaller lengths agglomerate into blocks, and some particles are in a relatively regular granular shape, indicating that local melting and aggregation occur in the product at this high temperature. In addition, EDS ( Figure 6 c and d) shows that the main components of point 3 on the particles and point 4 on the whiskers are C, O and Zr. The Zr and O contents of the particles are high, and the C and Zr contents of the whiskers are high, indicating that ZrCw is formed during the carbothermal reduction of ZrO2 to generate ZrC.

[0064] Example 5

[0065] The preparation method of the high-temperature resistant zirconium carbide whiskers in this example is basically the same as that shown in Example 2, and the main difference is that: the calcination holding time in this example is 1.5 h.

[0066] Example 6

[0067] The preparation method of the high-temperature resistant zirconium carbide whiskers in this example is basically the same as that shown in Example 2, and the main difference is that: the calcination holding time in this example is 2.5 h.

[0068] Comparative Example 3

[0069] The preparation method of the high-temperature resistant zirconium carbide whiskers in this example is basically the same as that shown in Example 2, and the main difference is that: the calcination holding time in this example is 1 h.

[0070] The comparison results of the scanning pictures of the products obtained under different calcination holding times are as Figure 7 shown. Combining Figure 7 it can be seen that when the holding time is 1 h, the pyrolysis products are mainly particles with a size less than 3 μm, and the small-sized particles are adsorbed on the surface of the large particles. At this time, no whisker structure is observed. Combining XRD analysis, the particles are composed of m-ZrO2 and t-ZrO2, indicating that the pyrolysis holding time of 1 h is not sufficient to promote the nucleation and growth of ZrCw. As the holding time is extended to 1.5 h ( Figure 7 c and d in Figure 8 ), a whisker structure is observed in the products; most of the whiskers are short rod-shaped, and the length of individual whiskers increases, indicating that the whiskers start to nucleate and grow at this time, but due to the short time, the growth of the whiskers is limited. EDS analysis ( Figure 8 ) shows that both the short rod-shaped whiskers at point 1 and the layered whiskers at point 2 contain C, Zr and a small amount of O elements, and the C / Zr atomic ratio is significantly higher than the stoichiometric ratio (1:1), which is presumably related to the carbon substrate or the amorphous carbon adsorbed on the surface during detection, indicating that both are ZrCw. A small amount of oxygen may come from the residual precursor, and its content is low and does not affect the main phase composition of ZrCw, further confirming that the whiskers with different morphologies are all ZrC phases.

[0071] When the time is further extended to 2 h ( Figure 7 e and 7f), whiskers with a larger length are formed in the products, which may be because the long-time holding provides sufficient energy for the full growth of the whiskers. However, when the holding time reaches 2.5 h ( Figure 7 g and Figure 7 h), the whisker morphology begins to coarsen, the whisker diameter increases and shows a curved spiral morphology, granular protrusions and branch structures appear on the surface, and at the same time, the adhesion phenomenon between whiskers is observed. This is because as the holding time is extended, while the whiskers continue to grow axially, the Ostwald ripening effect is enhanced, and the transverse growth of the whiskers becomes gradually significant, resulting in an increase in its diameter and the evolution of the morphology from slender to thick and large. It shows that too long pyrolysis holding time leads to the fusion and secondary growth of the whiskers.

[0072] Example 7

[0073] 1) Weigh the zirconium-containing organic precursor (PZC), lanthanum chloride (LaCl3), and nickel acetate (Ni(CH3COO)2) in a mass ratio of 1:5%:3% for standby.

[0074] 2) Add the weighed raw materials into p-xylene, and use a magnetic stirrer to stir and mix evenly. The stirring speed is 250 r / min and the time is 4 h to obtain a uniformly mixed reactant precursor raw material.

[0075] 3) Put the uniformly mixed reactant precursor raw material into an oven and dry it at a temperature of 120 °C for 900 min.

[0076] 4) Grind the dried powder and screen it with a 100-mesh sample sieve to obtain a powder with uniform particle size.

[0077] 5) Put the sieved powder into a crucible, send it into a tube furnace, heat it from room temperature to 1450 °C at a heating rate of 2.5 °C / min, and calcine it for 3 h under the protection of Ar with a gas flow rate of 100 cc / min to obtain high-temperature-resistant zirconium carbide whiskers. The aspect ratio and yield of the zirconium carbide whiskers prepared in this example are slightly lower than those in Example 1.

[0078] Example 8

[0079] 1) Weigh the zirconium-containing organic precursor (PZC), cerium chloride, and nickel acetate (Ni(CH3COO)2) in a mass ratio of 1:4%:5% for standby.

[0080] 2) Add the weighed raw materials into acetone, and use a magnetic stirrer to stir and mix evenly. The stirring speed is 500 r / min and the time is 1 h to obtain a uniformly mixed reactant precursor raw material.

[0081] 3) Put the uniformly mixed reactant precursor raw material into an oven and dry it at a temperature of 100 °C for 800 min.

[0082] 4) Grind the dried powder and screen it with a 100-mesh sample sieve to obtain a powder with uniform particle size.

[0083] 5) Put the sieved powder into a crucible, send it into a tube furnace, heat it from room temperature to 1600 °C at a heating rate of 1.5 °C / min, and calcine it for 4 h under the protection of Ar with a gas flow rate of 200 cc / min to obtain high-temperature-resistant zirconium carbide whiskers. In this example, the zirconium carbide whiskers obtained have coarsening phenomenon and there is adhesion sintering of the whiskers.

Claims

1. A preparation method of high-temperature resistant zirconium carbide whiskers, characterized in that, Comprising: Mixing a zirconium-containing organic precursor, a rare earth salt, and nickel acetate uniformly in an organic solvent to obtain a reactant precursor raw material; Drying, grinding, and sieving the obtained reactant precursor raw material; Reacting the dried, ground, and sieved reactant precursor raw material at a temperature of 1400 - 1600 °C from room temperature under a protective atmosphere to obtain zirconium carbide whiskers.

2. The preparation method of the high-temperature resistant zirconium carbide whiskers according to claim 1, characterized in that, The mass of the rare earth salt and nickel acetate respectively accounts for 2% - 6% and 1% - 5% of the mass of the zirconium-containing organic precursor.

3. The preparation method of the high-temperature resistant zirconium carbide whiskers according to claim 2, characterized in that, The zirconium-containing organic precursor includes but is not limited to the acetylacetonate zirconium precursor PZC; And / or the rare earth salt uses a soluble lanthanum salt or cerium salt; And / or the organic solvent uses xylene, p-xylene, or acetone.

4. The preparation method of the high-temperature resistant zirconium carbide whiskers according to any one of claims 1-3, characterized in that, The step of mixing the zirconium-containing organic precursor, the rare earth salt, and nickel acetate uniformly in the organic solvent is specifically to mix the raw materials uniformly by magnetic stirring, with the magnetic stirring speed being 250 - 500 r / min and the time being 1 - 4 h.

5. The preparation method of the high-temperature resistant zirconium carbide whiskers according to any one of claims 1-3, characterized in that, The drying temperature is 80 - 120 °C and the time is 600 - 900 min; and / or the grinding and sieving is specifically to sieve using a 100-mesh sieve.

6. The preparation method of the high-temperature resistant zirconium carbide whiskers according to any one of claims 1-3, characterized in that, Reacting the dried, ground, and sieved reactant precursor raw material at a temperature of 1400 - 1600 °C from room temperature under a protective atmosphere, controlling the heating rate to be 1.5 - 2.5 °C / min, and the pyrolysis holding time to be 1.5 - 2.5 h.

7. The preparation method of the high-temperature resistant zirconium carbide whiskers according to claim 6, wherein, The protective atmosphere uses an Ar atmosphere with a gas flow rate of 50 - 200 cc / min.

8. A high-temperature resistant zirconium carbide whisker prepared by the method according to any one of claims 1 - 7.

9. The high-temperature resistant zirconium carbide whisker according to claim 8, wherein, The diameter of the zirconium carbide whisker is 50 - 200 nm and the length is 2 - 50 μm.

10. An application of a high-temperature resistant zirconium carbide whisker prepared by the method according to any one of claims 1 - 7 in a metal matrix, resin matrix, or ceramic matrix composite material.

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