Silicon carbide whisker / high entropy boride composite material and preparation method thereof

Abstract

The present invention belongs to the technical field of ultra-high temperature structural material preparation, and specifically relates to a silicon carbide whisker / high entropy boride composite material and a preparation method thereof. The present invention uses metal oxides, boron carbide, graphite and silicon carbide whiskers as raw materials, firstly prepares a high entropy boride powder by a boron carbon thermal reduction method, then the powder and silicon carbide whiskers are subjected to simultaneous ultrasonic dispersion and mechanical stirring treatment to achieve uniform mixing, thereby obtaining a high entropy boride / silicon carbide whisker mixed powder, and then the powder is sintered to obtain a silicon carbide whisker / high entropy boride composite material, which has the advantages of uniform silicon carbide whisker distribution, high density, high hardness and high fracture toughness. The present invention effectively mixes severely agglomerated silicon carbide whiskers with high entropy boride powder by simultaneous ultrasonic dispersion and mechanical stirring treatment, and the process is simple. The fracture toughness of high entropy boride ceramics is increased by 26% relative to the case where silicon carbide whiskers are not added without reducing the hardness.

Description

Technical Field

[0001] The invention belongs to the technical field of ultra-high temperature structural material preparation, and specifically relates to a silicon carbide whisker / high entropy boride composite material and a preparation method thereof. Background Art

[0002] The information disclosed in this background technology section is only intended to enhance the understanding of the overall background of the invention, and should not necessarily be regarded as an admission or any form of suggestion that the information constitutes the prior art already known to a person skilled in the art.

[0003] High entropy boride ceramics are a new type of ultra-high temperature ceramics. Due to the four core effects of high entropy effect, hysteresis diffusion effect, lattice distortion effect and cocktail effect, they have better performance than single-component boride ceramics, such as higher hardness and better oxidation resistance. However, high entropy boride ceramics still have two fatal defects that limit their practical application, namely poor fracture toughness and poor oxidation resistance.

[0004] In order to improve the toughness of ceramics, researchers often use methods including second phase toughening, fine grain strengthening toughening, fiber toughening, and phase change toughening. Among the many reinforcing phases, silicon carbide is the most ideal reinforcing phase for ultra-high temperature ceramics due to its advantages such as high melting point, low density, high strength, and good oxidation resistance. And compared with silicon carbide particles, adding silicon carbide whiskers is more conducive to improving the toughness of ceramics. However, adding silicon carbide whiskers to high entropy boride ceramics requires solving the following three problems: 1. Since silicon carbide whiskers have higher surface energy, they are prone to agglomeration in ceramics and need to be dispersed. The commonly used dispersion method is ball milling, but the ball milling process is prone to introduce impurities and may destroy the whisker morphology; 2. The whisker morphology is prone to degeneration at high temperatures, so the sintering temperature needs to be lowered; 3. Whether the introduction of silicon carbide whiskers will affect the solid solution of high entropy boride ceramics.

[0005] Literature has shown that in B4C-SiCw composite ceramics, compared with B4C ceramics without SiCw, adding silicon carbide whiskers improves the toughness of the ceramics, but reduces the hardness of the ceramics. Therefore, it is of great significance to uniformly disperse silicon carbide whiskers in high-entropy boride ceramics in a reasonable way to regulate the mechanical properties of high-entropy boride material systems. However, there is no report on the toughening of high-entropy boride ceramics by silicon carbide whiskers. Summary of the invention

[0006] In order to overcome the deficiencies in the prior art, the purpose of the present invention is to provide a silicon carbide whisker / high entropy boride composite material and a preparation method thereof. The present invention uses metal oxides, boron carbide, graphite and silicon carbide whiskers as raw materials, firstly prepares a high entropy boride powder by boron carbon thermal reduction method, then simultaneously ultrasonically disperses and mechanically stirs the powder and silicon carbide whiskers, and finally freeze-dries to uniformly disperse the silicon carbide whiskers in the powder. Finally, sintering is performed to obtain a silicon carbide whisker / high entropy boride composite material, which has good practical application value.

[0007] In order to achieve the above object, the present invention is implemented through the following technical solutions:

[0008] In a first aspect, the present invention provides a method for preparing a silicon carbide whisker / high entropy boride composite material, comprising the following steps:

[0009] S1, grinding and mixing metal oxide powder, boron carbide powder and graphite, and then calcining to obtain high entropy boride powder;

[0010] S2, mixing high entropy boride powder and silicon carbide whiskers and adding them into deionized water, and simultaneously performing ultrasonic dispersion and mechanical stirring to obtain a mixed solution, and freeze-drying the mixed solution to obtain high entropy boride powder with silicon carbide whiskers uniformly dispersed;

[0011] S3, sintering the high entropy boride powder in which the silicon carbide whiskers are uniformly dispersed to obtain the silicon carbide whisker / high entropy boride composite material.

[0012] In a second aspect, the present invention provides a silicon carbide whisker / high entropy boride composite material obtained by the preparation method of the silicon carbide whisker / high entropy boride composite material described in the first aspect.

[0013] The beneficial effects achieved by one or more technical solutions of the present invention are as follows:

[0014] 1) The present invention uses five kinds of metal oxide powders, boron carbide powder and graphite as raw materials, and first obtains high entropy boride powder by boron-carbon thermal reduction method, and then further simultaneously performs ultrasonic treatment and mechanical stirring mixing with severely agglomerated silicon carbide whiskers, and preferably freeze-drying, to obtain silicon carbide whiskers / high entropy boride powder, which has the advantages of uniform dispersion of silicon carbide whiskers and intact whisker morphology;

[0015] 2) The preparation method provided by the present invention improves the fracture toughness of high entropy boride ceramics by 26% without reducing the hardness by toughening high entropy boride ceramics with silicon carbide whiskers, compared with the case without adding silicon carbide whiskers, and thus has good practical application value. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] The accompanying drawings in the specification, which constitute a part of the present invention, are used to provide a further understanding of the present invention. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute improper limitations on the present invention.

[0017] Figure 1 This is a scanning electron microscope photograph of the silicon carbide whisker / high entropy boride powder prepared in Example 1 of the present invention;

[0018] Figure 2 This is a scanning electron microscope photograph of the silicon carbide whisker / high entropy boride composite material prepared in Example 1 of the present invention;

[0019] Figure 3 This is the XRD spectrum of the silicon carbide whisker / high entropy boride composite material prepared in Example 1 of the present invention. DETAILED DESCRIPTION

[0020] A first typical embodiment of the present invention is a method for preparing a silicon carbide whisker / high entropy boride composite material, comprising the following steps:

[0021] S1. Mixing metal oxide powder, boron carbide powder and graphite and calcining the mixture to obtain high entropy boride powder;

[0022] S2, mixing high entropy boride powder and silicon carbide whiskers and adding them into deionized water, and simultaneously performing ultrasonic dispersion and mechanical stirring to obtain a mixed solution, and freeze-drying the mixed solution to obtain high entropy boride powder with silicon carbide whiskers uniformly dispersed;

[0023] S3, sintering the high entropy boride powder in which the silicon carbide whiskers are uniformly dispersed to obtain the silicon carbide whisker / high entropy boride composite material.

[0024] In one or more embodiments of this implementation, the metal oxide is any five of HfO2, ZrO2, Ta2O5, V2O5, Nb2O5, TiO2, Cr2O3, MoO3, and WO3.

[0025] In one or more examples of this embodiment, the molar ratio of the five metal oxides is 0.1-1:0.1-1:0.1-1:0.1-1:0.1-1.

[0026] In one or more examples of this embodiment, in step S1, the calcination temperature is 1550-1650° C., the time is 1-3 hours, and the calcination is performed in an inert atmosphere.

[0027] In one or more examples of this implementation mode, in step S2, the volume of the silicon carbide whiskers is 15-20% of the volume of the powder.

[0028] In one or more examples of this implementation mode, in step S2, the power of ultrasonic dispersion is 100-500 W, the speed of mechanical stirring is 50-400 rpm, and the time of ultrasonic dispersion and mechanical stirring is 15-60 hours.

[0029] In one or more examples of this embodiment, in step S4, the sintering temperature is 1700-1900°C, the sintering pressure is 20-40MPa, the sintering heating rate is 50-150°C / min, the sintering holding time is 5-20min, and the sintering is carried out in an argon atmosphere or in a vacuum.

[0030] A second typical embodiment of the present invention is a silicon carbide whisker / high entropy boride composite material, which is obtained by the preparation method of the silicon carbide whisker / high entropy boride composite material described in the first typical embodiment.

[0031] In one or more examples of this embodiment, the nominal molecular formula of the silicon carbide whisker / high entropy boride composite material is SiC w / (M1 0.2 M2 0.2 M3 0.2 M4 0.2 M5 0.2 )B2, wherein M1, M2, M3, M4, and M5 are respectively one of the transition metal elements Hf, Zr, Ti, Ta, Nb, Cr, V, Mo, and W.

[0032] In one or more examples of this implementation, the high entropy boride is composed of transition metal atomic layers and boron atomic layers alternately stacked in the c-axis direction, and five transition metals are randomly distributed in the transition metal atomic layers.

[0033] In order to enable those skilled in the art to more clearly understand the technical solution of the present invention, the technical solution of the present invention will be described in detail below in combination with specific embodiments and comparative examples.

[0034] Example 1

[0035] In this embodiment, a silicon carbide whisker / high entropy boride composite material is prepared. The specific steps are as follows:

[0036] S1. Powders are prepared according to a molar ratio of HfO2:ZrO2:Ta2O5:V2O5:Nb2O5:B4C:C=2:2:1:1:1:7.5:3.8, the prepared powders are mixed and kept at 1600°C for 2h to obtain high entropy boride powders;

[0037] S2, mixing the high entropy boride powder obtained in step S1 with 15 vol% of severely agglomerated silicon carbide whiskers in a test tube, adding 40 ml of deionized water, and simultaneously performing ultrasonic dispersion and mechanical stirring for 48 h, the speed of mechanical stirring being 100 rpm, and the power of ultrasonic dispersion being 100 W, to obtain a mixed solution;

[0038] S3, freeze-drying the mixed solution after ultrasonication and stirring in step S2 for 48 hours using a freeze dryer to obtain high entropy boride powder with uniformly dispersed silicon carbide whiskers;

[0039] S4. Sintering the freeze-dried powder in step S3 at 1800° C. in an argon atmosphere with a sintering pressure of 30 MPa and a holding time of 10 min to obtain a silicon carbide whisker / high entropy boride composite material.

[0040] Compared with the material without adding silicon carbide whiskers, the density and hardness of the material are slightly increased, and the fracture toughness is improved by 26%.

[0041] The microstructure of the obtained silicon carbide whisker / high entropy boride powder is referenced Figure 1 The scanning electron microscope photo shown. The microstructure and phase structure of the obtained silicon carbide whisker / high entropy boride composite material refer to Figure 2 and Figure 3 The scanning electron microscope image and XRD pattern are shown in Figure 2. In the XRD pattern, the composite material contains diffraction peaks of silicon carbide and high entropy boride (HEB).

[0042] Embodiment 2:

[0043] In this embodiment, a silicon carbide whisker / high entropy boride composite material is prepared. The specific steps are as follows:

[0044] S1. Powders are prepared according to a molar ratio of HfO2:ZrO2:Ta2O5:V2O5:Nb2O5:B4C:C=2:2:1:1:1:7.6:3.5, the prepared powders are mixed and kept at 1600°C for 2h to obtain high entropy boride powders;

[0045] S2, mixing the high entropy boride powder obtained in step S1 with 10 vol% of severely agglomerated silicon carbide whiskers in a test tube, adding 45 ml of deionized water, and simultaneously performing ultrasonic dispersion and mechanical stirring for 50 h, the speed of mechanical stirring being 50 rpm, and the power of ultrasonic dispersion being 100 W, to obtain a mixed solution;

[0046] S3, freeze-drying the mixed solution after ultrasonication and stirring in step S2 for 50 hours using a freeze dryer to obtain high entropy boride powder with uniformly dispersed silicon carbide whiskers;

[0047] S4. Sintering the freeze-dried powder in step S3 at 1800° C. in an argon atmosphere with a sintering pressure of 30 MPa and a holding time of 10 min to obtain a silicon carbide whisker / high entropy boride composite material.

[0048] Compared with the material without adding silicon carbide whiskers, the density and hardness of the material are slightly increased, and the fracture toughness is improved by 15%.

[0049] Embodiment 3:

[0050] In this embodiment, a silicon carbide whisker / high entropy boride composite material is prepared. The specific steps are as follows:

[0051] S1. Powders are prepared according to a molar ratio of HfO2:ZrO2:Ta2O5:TiO2:Nb2O5:B4C:C=2:2:1:2:1:7.5:4, the prepared powders are mixed and kept at 1600°C for 2h to obtain high entropy boride powder;

[0052] S2, mixing the high entropy boride powder obtained in step S1 with 15 vol% of severely agglomerated silicon carbide whiskers in a test tube, adding 50 ml of deionized water, and simultaneously performing ultrasonic dispersion and mechanical stirring for 55 h, the speed of mechanical stirring being 80 rpm, and the power of ultrasonic dispersion being 100 W, to obtain a mixed solution;

[0053] S3, freeze-drying the mixed solution after ultrasonication and stirring in step S2 for 52 hours using a freeze dryer to obtain high entropy boride powder with uniformly dispersed silicon carbide whiskers;

[0054] S4. Sintering the freeze-dried powder in step S3 at 1800° C. in an argon atmosphere with a sintering pressure of 35 MPa and a holding time of 15 min to obtain a silicon carbide whisker / high entropy boride composite material.

[0055] Compared with the material without adding silicon carbide whiskers, the density and hardness of the material are slightly increased, and the fracture toughness is improved by 15%.

[0056] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A method for preparing a silicon carbide whisker / high entropy boride composite material, characterized in that: The following steps are involved: S1. Mixing metal oxide powder, boron carbide powder and graphite and calcining the mixture to obtain high entropy boride powder; S2, mixing high entropy boride powder and silicon carbide whiskers and adding them into deionized water, and simultaneously performing ultrasonic dispersion and mechanical stirring to obtain a mixed solution, and freeze-drying the mixed solution to obtain high entropy boride powder in which silicon carbide whiskers are uniformly dispersed; the volume of the silicon carbide whiskers is 15-20% of the volume of the high entropy boride powder; S3, sintering the high entropy boride powder in which the silicon carbide whiskers are uniformly dispersed to obtain the silicon carbide whisker / high entropy boride composite material; The metal oxides are any five of HfO2, ZrO2, Ta2O5, V2O5, Nb2O5, TiO2, Cr2O3, MoO3, and WO3.

2. The preparation method according to claim 1, characterized in that The molar ratio of the five metal oxides is 0.1-1:0.1-1: 0.1-1: 0.1-1: 0.1-1.

3. The preparation method according to claim 1, characterized in that: In step S1, the calcination temperature is 1550-1650°C, the time is 1-3 h, and the calcination is carried out in an inert atmosphere.

4. The preparation method according to claim 1, characterized in that: In step S2, the power of ultrasonic dispersion is 100-500W, the rotation speed of mechanical stirring is 50-400 rpm, and the time of ultrasonic dispersion and mechanical stirring is 15-60 hours.

5. The preparation method according to claim 1, characterized in that: In step S3, the sintering temperature is 1700-1900°C, the sintering pressure is 20-40 MPa, the sintering heating rate is 50-150°C / min, the sintering holding time is 5-20min, and the sintering is carried out in an argon atmosphere or in a vacuum.

6. A silicon carbide whisker / high entropy boride composite material, characterized in that: The method is obtained by the preparation method of the silicon carbide whisker / high entropy boride composite material according to any one of claims 1 to 5.

7. The silicon carbide whisker / high entropy boride composite material according to claim 6, characterized in that: The molecular formula of the silicon carbide whisker / high entropy boride composite material is SiC w / (M1 0.2 M2 0.2 M3 0.2 M4 0.2 M5 0.2 )B2, wherein M1, M2, M3, M4, and M5 are respectively one of the transition metal elements Hf, Zr, Ti, Ta, Nb, Cr, V, Mo, and W.

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