Low-temperature preparation method of high-entropy boride ceramic composite material

Abstract

The invention provides a low-temperature preparation method of a high-entropy boride ceramic composite material. The low-temperature preparation method comprises the following steps: firstly, cutting a carbon fiber bundle into short carbon fibers with the length of about 2mm; then uniformly mixing the high-entropy boride powder, the SiC powder, the Co powder and the short carbon fibers; finally, the mixed powder is subjected to spark plasma sintering under the conditions that the temperature ranges from 1400 DEG C to 1600 DEG C and the pressure ranges from 30 MPa to 60 MPa, the high-entropy boride ceramic composite material is obtained, Co powder serves as a sintering auxiliary agent, the short carbon fibers are introduced, low-temperature densification and fracture toughness improvement of the composite material are achieved at the same time, and compared with a composite material without Co, the high-entropy boride ceramic composite material is obtained. The density of the prepared composite material is improved by more than 35%; compared with high-entropy boride ceramic without short carbon fibers, the fracture toughness of the prepared composite material is improved by 1.7-1.8 times. The method solves the problems that the high-entropy ultrahigh-temperature ceramic is difficult to densify effectively at low temperature and low in fracture toughness.

Description

Technical Field

[0001] The invention relates to the technical field, and in particular to a low-temperature preparation method of a high-entropy boride ceramic composite material. Background Art

[0002] High entropy boride ceramics (HEBs) have high hardness, high thermal stability, low thermal conductivity and excellent oxidation resistance, and have great application potential in aviation, aerospace, nuclear energy and mechanical processing. However, due to the strong covalent bonding, HEBs face high densification temperature (>2000℃) and low fracture toughness (3.5~4.5MPa·m 1 / 2 ) dual challenges. Ma et al. prepared (Hf 0.2 Zr 0.2 Ta 0.2 Nb 0.2 Ti 0.2 )B2 ceramics, with a density of 97.2% and a fracture toughness of 5.3 ± 0.2MPa·m 1 / 2 , to some extent, the densification temperature of HEBs is reduced and the fracture toughness of the material is improved, but the high equipment requirements limit the practical engineering application of this technology. The introduction of a second phase is also an effective way to reduce the densification temperature of boride ceramics and improve the fracture toughness of boride ceramics. Xu et al. 0.2 Zr 0.2 Ta 0.2 Nb 0.2 Ti 0.2 )B2 ceramics by introducing a low melting point sintering aid to reduce the densification temperature of HEBs, but this method cannot effectively improve the fracture toughness of HEBs. Luo et al. found that in (Ti 0.2 Zr 0.2 Hf 0.2 Nb 0.2 Ta 0.2 )C ceramics with 20 vol.% SiC w The fracture toughness of high entropy ceramics can be improved to a certain extent, but the densification temperature of this method is still relatively high (2000°C). Existing preparation methods cannot simultaneously reduce the sintering temperature and improve the fracture toughness of high entropy boride composites. In summary, it is crucial to develop a new low-temperature preparation method for high entropy boride ceramic composites. Summary of the invention

[0003] Based on the above technical problems, the present invention proposes a low-temperature preparation method of a high-entropy boride ceramic composite material.

[0004] A low-temperature preparation method for a high-entropy boride ceramic composite material, characterized in that it comprises the following steps: Step 1: Cut the carbon fiber bundle into short carbon fibers with a length of 2 mm; Step 2: putting high entropy boride (HEBs) powder, SiC powder, Co powder and the chopped carbon fiber into a ball mill, adding anhydrous ethanol and ZrO2 grinding balls for ball milling to obtain a uniformly mixed slurry; Step 3: The slurry after ball milling in step 2 is passed into a vacuum rotary dryer for drying to obtain a uniformly mixed powder; Step 4: The powder obtained in step 3 is placed into a graphite mold, sintered and densified by sintering, and cooled to room temperature to obtain C f / HEB-SiC-Co composite materials.

[0005] Preferably, in step 1, the thickness of the carbon coating on the surface of the carbon fiber bundle is 0-1 μm.

[0006] Preferably, in step 2, the transition metal elements in the high entropy boride powder include at least four of Ti, Zr, Hf, V, Nb, Ta, Cr, Mo and W.

[0007] Preferably, in step 2, the composition of the raw materials is: the high entropy boride powder is 50-75 vol.%, the SiC powder is 10-20 vol.%, the Co powder is 5-10 vol.%, and the chopped carbon fiber is 10-20 vol.%.

[0008] Preferably, in step 2, the average particle size of the SiC powder is 0.3-3 μm, and the average particle size of the Co powder is 1-75 μm.

[0009] Preferably, in step 2, the ball-to-material ratio in the ball mill is 1:1-3:1, the rotation speed of the ball mill is 90-400 r / min, and the ball milling time is 4-24 h.

[0010] Preferably, in step 3, the temperature of the drying process is 60-80° C., and the rotation speed of the vacuum rotary dryer is 10-60 r / min.

[0011] Preferably, in step 4, the sintering process parameters of the sintering method are: heating rate 10~100℃ / min, sintering temperature 1400~1600℃, sintering pressure 30~60MPa, and holding time 10~120min.

[0012] Preferably, in step 4, the atmosphere during the sintering process is vacuum or argon.

[0013] Preferably, in step 4, the sintering method is spark plasma sintering.

[0014] The present invention proposes a low-temperature preparation method of a high-entropy boride ceramic composite material, which has the following technical effects: (1) The present invention achieves the preparation of high-density high-entropy boride ceramic composites at low temperature (~1500°C) by introducing the sintering aid Co. f Compared with HEBs-SiC composites, the Co-containing C f / The density of HEBs-SiC-Co composites increased by more than 35%; (2) The present invention significantly improves the fracture toughness of high entropy boride ceramics by introducing chopped carbon fibers, which is comparable to the fracture toughness of conventional high entropy borides (3.5-4.5 MPa·m 1 / 2 ) compared to C f The fracture toughness of the composite material is increased by 1.7~1.8 times. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 This is a comparison chart of the sintering curves of the composite material before and after the introduction of Co in Example 1; Figure 2 This is the XRD pattern of the composite material before and after the introduction of Co in Example 2; Figure 3 C prepared in Examples 1 and 2 f SEM image of the indentation surface of / HEB-SiC-Co composite material. DETAILED DESCRIPTION

[0016] In order to more clearly understand the above-mentioned purpose, features and advantages of the present invention, the present invention is further described in detail below in conjunction with the accompanying drawings and specific embodiments. It should be noted that the embodiments of the present application and the features in the embodiments can be combined with each other without conflict.

[0017] In the following description, many specific details are set forth to facilitate a full understanding of the present invention. However, the present invention may also be implemented in other ways different from those described herein. Therefore, the protection scope of the present invention is not limited to the specific embodiments disclosed below.

[0018] In all embodiments of the present invention: The chemical formula of high entropy boride ceramic composite material is: C f / (Zr 0.2 Hf 0.2 Nb 0.2 Ta 0.2 Cr 0.2 )B2-SiC-Co; The chemical formula of high entropy boride powder is: Zr 0.2 Hf 0.2 Nb 0.2 Ta0.2 Cr 0.2 )B2; The high entropy boride powder used is prepared by boron / carbon thermal reduction method, the SiC powder used has a purity of 99.9% and a particle size of 500 nm, and the Co powder used has a purity of 99.9% and a particle size of 300 meshes.

[0019] Example 1 A low temperature preparation method of a high entropy boride ceramic composite material is as follows: Step 1: Cut the carbon fiber bundle containing 480nm carbon coating into short carbon fibers with a length of about 2mm; Step 2: Put high entropy boride powder, SiC powder, Co powder and chopped carbon fiber in step 1 in a volume ratio of 11:4:4:1 into a ball mill, add anhydrous ethanol and ZrO2 grinding balls for ball milling to obtain a uniformly mixed slurry; the ball-to-material ratio of the ball milling process is 1:1, the ball milling speed is 300r / min, and the ball milling time is 6h; Step 3: drying the slurry after ball milling in step 2 in a vacuum rotary dryer to obtain a uniformly mixed powder; the drying process temperature is 45° C. and the rotation speed is 30 r / min; Step 4: The powder obtained in step 3 is loaded into a graphite mold, and the powder is sintered and densified by spark plasma sintering. After cooling to room temperature, a high entropy boride ceramic composite material is obtained. The sintering process parameters are a heating rate of 100°C / min, a sintering temperature of 1500°C, a sintering pressure of 60MPa, and a holding time of 10min.

[0020] The density and fracture toughness of the high entropy boride ceramic composite material prepared in this example are 93.4% and 12.3±0.8MPa·m 1 / 2 ; It is similar to the Co-free C prepared under the same conditions. f / (Zr 0.2 Hf 0.2 Nb 0.2 Ta 0.2 Cr 0.2 )B2-SiC composites have a density increase of 36.7% and a fracture toughness of 3.5~4.5MPa·m 1 / 2 ) compared to C f The fracture toughness of the composite material is increased by 1.73 times.

[0021] Example 2 A low temperature preparation method of a high entropy boride ceramic composite material is as follows: Step 1: Cut the carbon fiber bundle containing 730nm carbon coating into short carbon fibers with a length of about 2mm; Step 2: Put high entropy boride powder, SiC powder, Co powder and chopped carbon fiber in step 1 in a volume ratio of 11:4:4:1 into a ball mill, add anhydrous ethanol and ZrO2 grinding balls for ball milling to obtain a uniformly mixed slurry; the ball-to-material ratio during the ball milling process is 3:1, the ball milling speed is 90 r / min, and the ball milling time is 24 h; Step 3: drying the slurry after ball milling in step 2 in a vacuum rotary dryer to obtain a uniformly mixed powder; the drying process temperature is 60° C. and the rotation speed is 60 r / min; Step 4: The powder obtained in step 3 is loaded into a graphite mold, sintered and densified by spark plasma sintering, and cooled to room temperature to obtain a high entropy boride ceramic composite material. The sintering process parameters are: a heating rate of 50°C / min, a sintering temperature of 1500°C, a sintering pressure of 60MPa, and a holding time of 10min. The density and fracture toughness of the high entropy boride ceramic composite material prepared in this embodiment are 94.7% and 12.4±1.1MPa·m 1 / 2 , compared with the Co-free C prepared under the same conditions f / (Zr 0.2 Hf 0.2 Nb 0.2 Ta 0.2 Cr 0.2 )B2-SiC composites have a density increase of 38.7% and a fracture toughness of 3.5~4.5MPa·m 1 / 2 ) compared to C f The fracture toughness of the composite material is increased by 1.76 times.

[0022] The sintering curves of the composite material before and after the introduction of Co powder in Example 1 were compared. Figure 1 As shown in Figure 3, the introduction of Co powder accelerates the densification of the composites.

[0023] The high entropy boride ceramic composite material obtained in Example 2 was mixed with a Co-free C f / (Zr 0.2 Hf 0.2 Nb 0.2 Ta 0.2 Cr 0.2 )B2-SiC composite materials were subjected to XRD tests, such as Figure 2 As shown in the figure: Similar to the composite material without Co, the Co-containing composite material prepared by this method is mainly composed of (Zr 0.2 Hf 0.2 Nb 0.2 Ta 0.2 Cr 0.2 )B2, SiC and C f It is composed of three phases, but a small amount of Co2B phase is formed.

[0024] The indentation surface of the high entropy boride ceramic composite material prepared in Examples 1-2 was tested by SEM. Figure 3 As shown in a and b: uniformly dispersed C f It can effectively inhibit crack propagation and thus improve the fracture toughness of the composite material.

[0025] 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 low-temperature preparation method for a high-entropy boride ceramic composite material, characterized in that: The following steps are involved: Step 1: Cut the carbon fiber bundle into short carbon fibers with a length of 2 mm; Step 2: placing high entropy boride powder, SiC powder, Co powder and the chopped carbon fiber into a ball mill, adding anhydrous ethanol and ZrO2 grinding balls for ball milling to obtain a uniformly mixed slurry; Step 3: The slurry after ball milling in step 2 is passed into a vacuum rotary dryer for drying to obtain a uniformly mixed powder; Step 4: The powder obtained in step 3 is placed into a graphite mold, sintered and densified by sintering, and cooled to room temperature to obtain C f / HEB-SiC-Co composite materials.

2. The low-temperature preparation method of the high-entropy boride ceramic composite material according to claim 1, characterized in that: In step 1, the thickness of the carbon coating on the surface of the carbon fiber bundle is 0-1 μm.

3. The low-temperature preparation method of the high-entropy boride ceramic composite material according to claim 1, characterized in that: In step 2, the transition metal elements in the high entropy boride powder include at least four of Ti, Zr, Hf, V, Nb, Ta, Cr, Mo and W.

4. The low-temperature preparation method of the high-entropy boride ceramic composite material according to claim 1, characterized in that: In step 2, the composition of the raw materials is as follows: the high entropy boride powder is 50-75 vol.%, the SiC powder is 10-20 vol.%, the Co powder is 5-10 vol.%, and the chopped carbon fiber is 10-20 vol.%.

5. The low-temperature preparation method of the high-entropy boride ceramic composite material according to claim 1, characterized in that: In step 2, the average particle size of the SiC powder is 0.3-3 μm, and the average particle size of the Co powder is 1-75 μm.

6. The low-temperature preparation method of high entropy boride ceramic composite material according to claim 1, characterized in that: In step 2, the ball-to-material ratio in the ball mill is 1:1-3:1, the rotation speed of the ball mill is 90-400 r / min, and the ball milling time is 4-24 h.

7. The low-temperature preparation method of high entropy boride ceramic composite material according to claim 1, characterized in that: In step 3, the temperature of the drying process is 60-80° C., and the rotation speed of the vacuum rotary dryer is 10-60 r / min.

8. The low-temperature preparation method of high entropy boride ceramic composite material according to claim 1, characterized in that: In step 4, the sintering process parameters of the sintering method are: heating rate 10~100℃ / min, sintering temperature 1400~1600℃, sintering pressure 30~60MPa, and holding time 10~120min.

9. The low-temperature preparation method of the high-entropy boride ceramic composite material according to claim 1, characterized in that: In step 4, the atmosphere during the sintering process is vacuum or argon.

10. The low-temperature preparation method of high entropy boride ceramic composite material according to claim 1, characterized in that: In step 4, the sintering method is spark plasma sintering.

Images