ABLATION-RESISTANT HIGH-ENTROPY CARBIDE-HIGH-ENTROPY DIBORIDE-SILICON CARBIDE MULTIPHASE CERAMIC AND PREPARATION THEREOF

Abstract

diboride-silicon carbide (SiC) multiphase ceramic, including: (S1) mixing a transition metal oxide mixed powder, nano carbon black and a silicon hexaboride (SiB.sub.6) powder to obtain a precursor powder; and (S2) subjecting the precursor powder to pressureless sintering to obtain the high-entropy carbide-high-entropy diboride-SiC multiphase ceramic with a relative density of 96% or more.

Claims

1. A method for preparing an ablation-resistant high-entropy carbide-high-entropy diboride-silicon carbide (SiC) multiphase ceramic, comprising: (S1) mixing a transition metal oxide mixed powder, nano carbon black and a silicon hexaboride (SiB.sub.6) powder to obtain a precursor powder; and (S2) subjecting the precursor powder to pressureless sintering to obtain the high-entropy carbide-high-entropy diboride-SiC multiphase ceramic; wherein a relative density of the high-entropy carbide-high-entropy diboride-SiC multiphase ceramic is 96% or more.

2. The method of claim 1, wherein a molar ratio of transition metal atoms of the transition metal oxide mixed powder to the nano carbon black to the SiB.sub.6 powder is (1-20):(1-64):(0-8), and a molar content of the SiB.sub.6 powder is greater than zero.

3. The method of claim 1, wherein the transition metal oxide mixed powder comprises hafnium oxide (HfO.sub.2), zirconium dioxide (ZrO.sub.2), tantalum pentoxide (Ta.sub.2O.sub.5), niobium (V) oxide (Nb.sub.2O.sub.5) and titanium dioxide (TiO.sub.2) in a molar ratio of 2:2:1:1:2.

4. The method of claim 1, wherein a particle size of the transition metal oxide mixed powder is 100 nm; a particle size of the nano carbon black is 50 nm; and a particle size of the SiB.sub.6 powder is 3-8 μm.

5. The method of claim 1, wherein step (S1) comprises: (S1-1) subjecting HfO.sub.2, ZrO.sub.2, Ta.sub.2O.sub.5, Nb.sub.2O.sub.5 and TiO.sub.2 to ball milling and drying to obtain the transition metal oxide mixed powder; and (S1-2) subjecting the transition metal oxide mixed powder, the nano carbon black and the SiB.sub.6 powder to ball milling and drying to obtain the precursor powder.

6. The method of claim 5, wherein in step (S1-1), the ball milling is performed in isopropyl alcohol at 200-600 rpm for 8-60 h, and a ratio of a total weight of HfO.sub.2, ZrO.sub.2, Ta.sub.2O.sub.5, Nb.sub.2O.sub.5 and TiO.sub.2 to a weight of balls is 1:(10-20); and In step (S1-2), the ball milling is performed in isopropyl alcohol at 200-600 rpm for 8-60 h, and a ratio of a total weight of the transition metal oxide mixed powder, the nano carbon black and the SiB.sub.6 powder to a weight of balls is 1:(10-20).

7. The method of claim 1, wherein a maximum temperature of the pressureless sintering is 1900-2100° C.; and the pressureless sintering is performed for 1-9 h.

8. The method of claim 1, wherein the pressureless sintering is performed in a stepwise manner through the following temperature program: rising from room temperature to 1900-2100° C. at a rate of 10-50° C./min; 1900-2100° C. for 5-30 min; decreasing to 1600-1900° C. at a rate of 50-100° C./min; 1600-1900° C. for 1-8 h; and decreasing to room temperature at a rate of 10-50° C./min; wherein a vacuum degree of the pressureless sintering is controlled at 0.001-0.05 Pa.

9. The method of claim 7, wherein the pressureless sintering is performed in a stepwise manner through the following temperature program: rising from room temperature to 1900-2100° C. at a rate of 10-50° C./min; 1900-2100° C. for 5-30 min; decreasing to 1600-1900° C. at a rate of 50-100° C./min; 1600-1900° C. for 1-8 h; and decreasing to room temperature at a rate of 10-50° C./min; wherein a vacuum degree of the pressureless sintering is controlled at 0.001-0.05 Pa.

10. The method of claim 1, wherein before the pressureless sintering, the precursor powder is pre-pressed into a cylindrical blank by cold isostatic pressing.

11. An ablation-resistant high-entropy carbide-high-entropy diboride-SiC multiphase ceramic prepared by the method of claim 1. A method for preparing an ablation-resistant high-entropy carbide-high-entropy

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0038] The patent or application file contains FIGS. 1, 2 and 3 executed in color. Copies of this patent or patent application publication with color drawing(s) will be provided by the Office upon request and payment of the necessary fee.

[0039] FIG. 1 shows an X-ray diffraction (XRD) pattern of a high-entropy carbide-high-entropy diboride-SiC multiphase ceramic prepared in Example 2;

[0040] FIG. 2 displays a scanning electron microscopy (SEM) image of the high-entropy carbide-high-entropy diboride-SiC multiphase ceramic prepared in Example 2; and

[0041] FIG. 3 illustrates a mass ablation rate of the high-entropy carbide-high-entropy diboride-SiC multiphase ceramic prepared in Example 2.

DETAILED DESCRIPTION OF EMBODIMENTS

[0042] Technical solutions of the present disclosure will be clearly and completely described below with reference to the embodiments and accompanying drawings. Obviously, provided herein are merely some embodiments of this disclosure, which are not intended to limit the disclosure.

[0043] The disclosure provides a method for preparing an ablation-resistant high-entropy carbide-high-entropy diboride-SiC multiphase ceramic, which includes the following steps.

[0044] (S1) Commercially-available HfO.sub.2 powder, ZrO.sub.2 powder, Ta.sub.2O.sub.5 powder, Nb.sub.2O.sub.5 powder and TiO.sub.2 powder (particle size: about 100 nm, and purity ≥99.9%) are mixed by ball milling in a planetary ball mill in a molar ratio of 2:2:1:1:2 to obtain a mixed powder, where the ball milling is performed in isopropyl alcohol at 200-600 rpm for 24-60 h, and a weight ratio of the mixed powder to balls is 1:(10-20). Then the mixed powder is dried, and ground in an agate mortar.

[0045] (S2) The mixed powder, nano carbon black (50 nm) and SiB.sub.6 powder (3-8 μm) are subjected to ball milling in a planetary ball mill to obtain a precursor powder, in which a molar ratio of transition metal atoms of the mixed powder to the nano carbon black to the SiB.sub.6 powder is (1-20):(1-64):(0-8), and a molar content of the SiB.sub.6 powder is greater than zero; the ball milling is performed in isopropyl alcohol at 200-600 rpm for 8-36 h; and a weight ratio of the precursor powder to balls is 1:(10-20).

[0046] (S3) The precursor powder is pre-pressed into a cylindrical blank by cold isostatic pressing, and is subjected to stepwise pressureless sintering through the following temperature program to obtain the uniform and dense high-entropy carbide-high-entropy diboride-SiC multiphase ceramic with a relative density of 96-100%: rising from room temperature to 1900-2100° C. at a rate of 10-50° C./min; 1900-2100° C. for 5-30 min; decreasing to 1600-1900° C. at a rate of 50-100° C./min; 1600-1900° C. for 1-8 h; and decreasing to room temperature at 10-50° C./min, where a vacuum degree is controlled at 0.001-0.05 Pa.

[0047] The above-mentioned transition metal oxide nano powders (HfO.sub.2 powder, ZrO.sub.2 powder, Ta.sub.2O.sub.5 powder, Nb.sub.2O.sub.5 powder and TiO.sub.2 powder, purity ≥99.9%) are manufactured by Shanghai Chaowei Nano Technology CO., Ltd; purity of isopropyl alcohol: ≥99.8%; the nano carbon black is produced by Beijing Innochem Science & Technology CO., Ltd, purity ≥99.9%; and the SiB.sub.6 powder is produced by Alfa Aesar, purity≥98%.

[0048] Instruments: QM-3 SP4 planetary ball mill produced by Nanjing University; DHG-9075A electric thermostatic drying oven produced by SHANGHAI YIHENG INSTRUMENTS CO., Ltd; ZT-50-22Y vacuum graphite tube sintering furnace produced by Shanghai Chenhua Technology Co., Ltd.

[0049] The disclosure will be described in detail below with reference to the embodiments.

Example 1

[0050] Provided was a method for preparing an ablation-resistant high-entropy carbide-high-entropy diboride-SiC multiphase ceramic, which included the following steps.

[0051] (S1) Commercially-available HfO.sub.2 powder, ZrO.sub.2 powder, Ta.sub.2O.sub.5 powder, Nb.sub.2O.sub.5 powder and TiO.sub.2 powder (particle size: about 100 nm, and purity ≥99.9%) were mixed by ball milling in a planetary ball mill in a molar ratio of 2:2:1:1:2 to obtain a mixed powder, where the ball milling was performed in isopropyl alcohol at 500 rpm for 24 h, and a weight ratio of the mixed powder to balls was 1:10. Then the mixed powder was dried, and grounded in an agate mortar.

[0052] (S2) The mixed powder, nano carbon black (50 nm) and SiB.sub.6 powder (3-8 μm) were subjected to ball milling in a planetary ball mill to obtain a precursor powder, in which a molar ratio of transition metal atoms of the mixed powder to the nano carbon black to the SiB.sub.6 powder was 5:14:1; the ball milling was performed in isopropyl alcohol at 550 rpm for 12 h; and a weight ratio of the precursor powder to balls was 1:10.

[0053] (S3) The precursor powder was pre-pressed into a cylindrical blank by cold isostatic pressing, and was subjected to stepwise pressureless sintering through the following temperature program to obtain the uniform and dense high-entropy carbide-high-entropy diboride-SiC multiphase ceramic with a relative density of 97.5%: rising from room temperature to 1900° C. at a rate of 50° C./min; 1900° C. for 30 min; decreasing to 1750° C. at a rate of 100° C./min; 1750° C. for 7 h; and decreasing to room temperature at 50° C./min, where a vacuum degree was controlled at 0.001 Pa.

Example 2

[0054] Provided was a method for preparing an ablation-resistant high-entropy carbide-high-entropy diboride-SiC multiphase ceramic, which included the following steps.

[0055] (S1) Commercially-available HfO.sub.2 powder, ZrO.sub.2 powder, Ta.sub.2O.sub.5 powder, Nb.sub.2O.sub.5 powder and TiO.sub.2 powder (particle size: about 100 nm, and purity ≥99.9%) were mixed by ball milling in a planetary ball mill in a molar ratio of 2:2:1:1:2 to obtain a mixed powder, where the ball milling was performed in isopropyl alcohol at 450 rpm for 36 h, and a weight ratio of the mixed powder to balls was 1:15. Then the mixed powder was dried, and grounded in an agate mortar.

[0056] (S2) The mixed powder, nano carbon black (50 nm) and SiB.sub.6 powder (3-8 μm) were subjected to ball milling in a planetary ball mill to obtain a precursor powder, in which a molar ratio of transition metal atoms of the mixed powder to the nano carbon black to the SiB.sub.6 powder was 5:13:2; the ball milling was performed in isopropyl alcohol at 500 rpm for 24 h; and a weight ratio of the precursor powder to balls was 1:15.

[0057] (S3) The precursor powder was pre-pressed into a cylindrical blank by cold isostatic pressing, and was subjected to stepwise pressureless sintering through the following temperature program to obtain the uniform and dense high-entropy carbide-high-entropy diboride-SiC multiphase ceramic with a relative density more than 98%: rising from room temperature to 1950° C. at a rate of 40° C./min; 1950° C. for 25 min; decreasing to 1700° C. at a rate of 80° C./min; 1700° C. for 6 h; and decreasing to room temperature at 40° C./min, where a vacuum degree was controlled at 0.008 Pa.

[0058] Referring to FIG. 1, the high-entropy carbide-high-entropy diboride-SiC multiphase ceramic provided herein had great crystallinity, and mainly included two phases, respectively (Hf.sub.0.2Zr.sub.0.2Ta.sub.0.2Nb.sub.0.2Ti.sub.0.2)B.sub.2 and SiC, where the primary phase was (Hf.sub.0.2Zr.sub.0.2Ta.sub.0.2Nb.sub.0.2Ti.sub.0.2)B.sub.2, which corresponded to a hexagonal phase HfB.sub.2 PDF NO. 38-1398 and a hexagonal phase NbB.sub.2 PDF NO. 35-0742; and a secondary phase was SiC, which corresponded to a cubic phase SiC PDF NO. 29-1129.

[0059] Referring to FIG. 2, the high-entropy carbide-high-entropy diboride-SiC multiphase ceramic provided herein was relatively dense and uniform with a relative density of 98.6% and a particle size of 3 μm. SiC was uniformly dispersed in the high-entropy diboride.

[0060] Referring to FIG. 3, a mass ablation rate of the high-entropy carbide-high-entropy diboride-SiC multiphase ceramic provided herein was 0.078 mg cm.sup.−2 s.sup.−1 under a 2500° C. oxyacetylene flame for 120 s. Amass ablation rate of the high-entropy carbide-high-entropy diboride-SiC multiphase ceramic provided herein as −0.108 mg Cm.sup.−2 s.sup.−1 under a 3000° C. oxyacetylene flame for 120 s.

[0061] Accordingly, the high-entropy carbide-high-entropy diboride-SiC multiphase ceramic, prepared through pressureless sintering based on synergetic effect of carbon-boron-silicification reaction and solid solution with SiB.sub.6 as Si source and B source, is near fully dense (relative density of 99%), and has evenly distributed phases and small grain size (3 μm). The multiphase ceramic prepared by the method provided herein has great crystallinity, and the high-entropy diboride and SiC are uniformly dispersed in the high-entropy carbide to form a dense and stable oxide protective layer after oxidation and ablation, which preferably forms with the synergistically induced by Si and B. Thereby, the ablation resistance of the high-entropy ultrahigh temperature multiphase ceramic is greatly improved. The method provided herein has simple preparation and low sintering temperature, and the element, phase composition, and microstructure are controllable. The method provided herein can performed by one step, and is suitable for preparation of any size and shape ceramics. The multiphase ceramic has excellent ablation resistance, which has a mass ablation rate of slightly larger than −0.05 mg cm.sup.−2 s.sup.−1 under the 2500° C. oxyacetylene flame for 120 s, and a mass ablation rate of not larger than −0.2 mg cm.sup.−2 s.sup.−1 under the 3000° C. oxyacetylene flame for 120 s, and has no obvious cracks on the surface.

Example 3

[0062] Provided was a method for preparing an ablation-resistant high-entropy carbide-high-entropy diboride-SiC multiphase ceramic, which included the following steps.

[0063] (S1) Commercially-available HfO.sub.2 powder, ZrO.sub.2 powder, Ta.sub.2O.sub.5 powder, Nb.sub.2O.sub.5 powder and TiO.sub.2 powder (particle size: about 100 nm, and purity ≥99.9%) were mixed by ball milling in a planetary ball mill in a molar ratio of 2:2:1:1:2 to obtain a mixed powder, where the ball milling was performed in isopropyl alcohol at 300 rpm for 60 h, and a weight ratio of the mixed powder to balls was 1:20. Then the mixed powder was dried, and grounded in an agate mortar.

[0064] (S2) The mixed powder, nano carbon black (50 nm) and SiB.sub.6 powder (3-8 μm) were subjected to ball milling in a planetary ball mill to obtain a precursor powder, in which a molar ratio of transition metal atoms of the mixed powder to the nano carbon black to the SiB.sub.6 powder was 10:32:1; the ball milling was performed in isopropyl alcohol at 300 rpm for 36 h; and a weight ratio of the precursor powder to balls was 1:20.

[0065] (S3) The precursor powder was pre-pressed into a cylindrical blank by cold isostatic pressing, and was subjected to stepwise pressureless sintering through the following temperature program to obtain the uniform and dense high-entropy carbide-high-entropy diboride-SiC multiphase ceramic with a relative density of 99%: rising from room temperature to 2000° C. at a rate of 20° C./min; 2000° C. for 10 min; decreasing to 1900° C. at a rate of 60° C./min; 1900° C. for 4 h; and decreasing to room temperature at 20° C./min, where a vacuum degree was controlled at 0.005 Pa.

[0066] Described above are merely preferred embodiments of the disclosure, which are not intended to limit the disclosure. It should be understood that replacements, modifications and variations made by those skilled in the art without departing from the spirit and scope of the disclosure shall fall within the scope of the disclosure defined by the appended claims.