Boron carbide silicon carbide composite ceramic and preparation method thereof

A technology of boron carbide silicon carbide and composite ceramics, which is applied in the field of ceramic materials, can solve the problems of reducing the hardness of products and its high-temperature mechanical properties, difficult to use precision structural engineering, and poor high-temperature mechanical properties, etc., and meets the requirements of fine grain and particle size Good effect of low and high temperature mechanical properties

Inactive Publication Date: 2013-04-10
WUHAN UNIV OF TECH
3 Cites 18 Cited by

AI-Extracted Technical Summary

Problems solved by technology

[0007] In the preparation methods involved in the above patents, if Si is used as an infiltration agent for vacuum infiltration, a large amount of Si elemental remains in the product, which reduces the hardness and high-temperature mechanical properties of the product. In addition, the product prepared by this method , the distribution of the two phases is uneven, resulting in unstable per...
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Abstract

The invention relates to a method for preparing boron carbide silicon carbide composite ceramic and belongs to the technical field of ceramic materials. The boron carbide silicon carbide composite ceramic is prepared by mechanically alloying three-element mixed powder of boron carbide, carbon powder and silicon powder and sintering by a reaction hot-pressing technology, wherein the three-element mixed powder comprises 50 to 90 weight percent of boron carbide powder, 15 to 3 weight percent of carbon powder and 35 to 7 weight percent of silicon powder; and the molar ratio of the carbon powder to the silicon powder is 0.8 to 1.2. The high-compactness boron carbide silicon carbide composite ceramic can be obtained at low temperature without adding a liquid phase sintering aid. Silicon carbide which is obtained through in-situ synthesis in the sintering process of carbon and silicon has high purity and the crystal grains are small and dispersed uniformly, so the mechanical property of the ceramic is improved. The boron carbide silicon carbide composite ceramic prepared by the method has high compactness, high hardness and high high-temperautre mechanical property and can serve as an anti-impact and wear-resistant part of precise structure engineering.

Technology Topic

Carbide siliconComposite ceramic +5

Image

  • Boron carbide silicon carbide composite ceramic and preparation method thereof
  • Boron carbide silicon carbide composite ceramic and preparation method thereof
  • Boron carbide silicon carbide composite ceramic and preparation method thereof

Examples

  • Experimental program(6)

Example Embodiment

[0036] Example 1
[0037] A boron carbide silicon carbide composite ceramic, the mass ratio of boron carbide to silicon carbide in the boron carbide silicon carbide composite ceramic is 4:1, which consists of a ternary mixed powder of boron carbide, amorphous carbon powder and silicon powder through mechanical After alloying, it is sintered by reactive hot pressing technology. According to the weight percentage, the ternary mixed powder includes 80% boron carbide powder (purity 97%, particle size 75um), amorphous carbon powder 6 % (Purity is 98%, particle size is 1um), silicon powder 14% (purity is 99%, particle size is 75um).
[0038] The method for preparing the boron carbide silicon carbide composite ceramics of this embodiment, the specific steps include:
[0039] 1) Preparation of amorphous high-activity boron carbide, carbon and silicon composite powder
[0040] ①According to weight percentage, weigh boron carbide powder with a purity of 97% and a particle size of 75um; an amorphous carbon powder with a purity of 98% and a particle size of 1um; and a silicon powder with a purity of 99% and a particle size of 75um. The weight percentages of boron carbide powder, amorphous carbon powder and silicon powder are 80%, 6% and 14%. The weighed boron carbide powder, amorphous carbon powder and silicon powder are first mixed by hand in agate grinding. The mixed powder and stainless steel grinding balls are placed in a stainless steel vacuum ball mill with a mass ratio of 40:1. The ball mill is evacuated, and then argon is injected. The ball mill is 100h, and the speed of the planetary ball mill is 250rpm;
[0041] ②Use 2mol/L hydrochloric acid to wash away the Fe impurities introduced in the powder during the ball milling process, and then wash the powder after suction filtration with deionized water for 3 times;
[0042] ③Put the acid-washed composite powder in a vacuum drying oven at 100°C for 24 hours, then grind it in agate grinding and pass through a 200-mesh sieve;
[0043] 2) Reaction hot pressing sintering
[0044] Put the composite powder prepared in step 1) into a graphite abrasive tool, separate the composite powder from the abrasive tool and the indenter with graphite paper, and put it into the hot pressing sintering furnace at 20℃/min in a vacuum atmosphere The temperature is raised to 1500°C for 10 minutes, then the temperature is raised to 1950°C at a rate of 10°C/min, the temperature is kept for 60 minutes, a pressure of 30MPa is applied, and the boron carbide silicon carbide composite ceramic can be obtained by natural cooling.
[0045] The properties of the obtained boron carbide silicon carbide composite ceramic samples are as follows: relative density 97.6%, Vickers hardness 29GPa, bending strength 501MPa, fracture toughness 4.9MPa.m 1/2.
[0046] by figure 1 It can be seen that the pre-mixed powder is obtained by mixing raw boron carbide powder, amorphous carbon powder and silicon powder. The XRD pattern contains strong boron carbide and silicon peaks. Because of the amorphous carbon used, the carbon peaks are not The composite powder after the pre-mixed powder undergoes step 1) ①, due to the effect of mechanical alloying, there is almost no obvious peak in the XRD display of the composite powder after the ball milling, indicating that the powder has Transform into a highly active amorphous state; the XRD of the boron carbide silicon carbide composite ceramic obtained after sintering only shows the peaks of boron carbide and silicon carbide, indicating that the composite ceramic only contains these two items, and silicon and carbon have completely reacted to form Silicon carbide.
[0047] by figure 2 It can be seen that the obtained boron carbide silicon carbide composite ceramics are almost completely dense, with only a few pores less than 0.5um in size, and the relative density of the sample is relatively high; the white silicon carbide generated in situ is evenly distributed in the gray boron carbide .

Example Embodiment

[0048] Example 2
[0049] A boron carbide silicon carbide composite ceramic, the mass ratio of boron carbide to silicon carbide in the boron carbide silicon carbide composite ceramic is 4:1, which is mechanically alloyed by a ternary mixed powder of boron carbide, carbon black and silicon powder Then, it is sintered by reactive hot pressing technology. The ternary mixed powder according to weight percentage includes 80% of boron carbide powder (purity of 97%, particle size of 75um), carbon black 6% (purity of 98%, particle size is 1um), silicon powder 14% (purity is 99%, particle size is 75um).
[0050] The method for preparing the boron carbide silicon carbide composite ceramics of this embodiment, the specific steps include:
[0051] 1) Preparation of amorphous high-activity boron carbide, carbon and silicon composite powder
[0052] ①Weigh boron carbide powder with a purity of 97% and a particle size of 75um; carbon black with a purity of 98% and a particle size of 1um; silicon powder with a purity of 99% and a particle size of 75um, boron carbide The weight percentages of powder, carbon black and silicon powder are 80%, 6% and 14%. The weighed boron carbide powder, carbon black and silicon powder are mixed manually in the agate grinding, and the pre-mixed powder and stainless steel Put the grinding balls into a stainless steel vacuum ball mill tank with a ball-to-material mass ratio of 50:1. Vacuum the ball mill tank, then pour argon gas into it, ball mill for 80 hours, and rotate the planetary ball mill at 350rpm;
[0053] ②Use 2mol/L hydrochloric acid to wash away the Fe impurities introduced in the powder during the ball milling process, and then wash the powder after suction filtration with deionized water for 3 times;
[0054] ③Place the acid-washed composite powder in a vacuum drying oven at 90°C for 48 hours, then grind it in agate grinding and pass through a 200 mesh sieve;
[0055] 2) Reaction hot pressing sintering
[0056] Put the composite powder prepared in step 1) into the graphite abrasive tool, separate the powder from the abrasive tool and the indenter with graphite paper, put it into the hot pressing sintering furnace, and heat up at 20℃/min in a vacuum atmosphere After the temperature reaches 1500°C, the temperature is kept for 10 minutes, and then the temperature is raised to 1950°C at a rate of 10°C/min, the temperature is kept for 60 minutes, the pressure is 30MPa, and the boron carbide silicon carbide composite ceramic is obtained by natural cooling.
[0057] by image 3 It can be seen that the obtained boron carbide silicon carbide composite ceramics are also very dense, almost no pores are visible, and the relative density of the sample is very high; the white silicon carbide generated in situ is uniformly distributed in the gray boron carbide.

Example Embodiment

[0058] Example 3
[0059] The difference between this embodiment and Embodiment 2 is that the weight percentages of boron carbide powder, carbon black and silicon powder are 90%, 3% and 7%.
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PUM

PropertyMeasurementUnit
Bending strength501.0mPa
Fracture toughness4.9mpa.m1/2
Bending strength477.0mPa
tensileMPa
Particle sizePa
strength10

Description & Claims & Application Information

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Classification and recommendation of technical efficacy words

  • High hardness
  • Improve compactness
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