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A kind of preparation method of dense silicon carbide ceramics without boron or rare earth elements

A technology of silicon carbide ceramics and rare earth elements, which is applied in the field of structural ceramics, can solve the problems of difficult to achieve densification of silicon carbide ceramics, and achieve the effects of uniform and meticulous microstructure, good mechanical properties and simple equipment.

Active Publication Date: 2016-10-12
SHANGHAI INST OF CERAMIC CHEM & TECH CHINESE ACAD OF SCI
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

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Problems solved by technology

[0004] However, for the sintering of submicron silicon carbide powder, it is difficult to achieve densification of silicon carbide ceramics when aluminum nitride powder and carbon are used as sintering aids alone.

Method used

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  • A kind of preparation method of dense silicon carbide ceramics without boron or rare earth elements
  • A kind of preparation method of dense silicon carbide ceramics without boron or rare earth elements
  • A kind of preparation method of dense silicon carbide ceramics without boron or rare earth elements

Examples

Experimental program
Comparison scheme
Effect test

Embodiment 1

[0050] A method for dense silicon carbide ceramics without boron or rare earth elements, carried out as follows:

[0051] Step 1: 12wt% aluminum sol (containing 20wt% AlOOH, calculated as 2wt% AlN by Al), 10.5wt% phenolic resin (calculated as 3wt% C by residual carbon after thermal cracking and carbothermal reduction reaction), 77.5wt% Silicon carbide powder (the average particle size of the powder is 0.4 microns, and the content after thermal cracking and carbothermal reduction reaction is 95wt%) is uniformly mixed with absolute ethanol, ball milled for 4 hours, dried at 60°C, ground and sieved;

[0052] Step 2: After the mixed powder is dry-pressed at 20 MPa, it is placed in an open mold at the top, and it is heated and cracked in a sintering furnace. The sintering furnace is heated to 900 °C at a heating rate of 2 °C / min, and the holding time is 1h, the atmosphere in the heating cracking process is vacuum;

[0053] Step 3: Carry out the carbothermal reduction reaction in t...

Embodiment 2

[0056] Step 1: 12wt% aluminum sol (containing 20wt% AlOOH, calculated as 2wt% AlN by Al), 3.8wt% carbon black (calculated as 3wt% C by residual carbon after carbothermal reduction reaction), 94.2wt% silicon carbide powder powder (the average particle size of the powder is 0.4 microns, and the content after thermal cracking and carbothermal reduction reaction is 95wt%) and absolute ethanol are uniformly mixed, ball milled for 4 hours, dried at 60°C, ground and sieved;

[0057] Step 2: Dry-press the mixed powder at 20 MPa, press isostatically at 200 MPa for 2 minutes, and obtain a ceramic green body;

[0058] Step 3: Place the ceramic green body in the mold with the upper part open, carry out thermal cracking in the sintering furnace, heat the sintering furnace to 900°C at a heating rate of 2°C / min, and keep it for 1h. During the thermal cracking process The atmosphere is a vacuum;

[0059] Step 4: Carrying out the carbothermal reduction reaction in the sintering furnace, heati...

Embodiment 3

[0062] The difference between this embodiment and specific embodiment 1 is that the AlOOH sol in step 1 is replaced by alumina powder, and the raw material composition is 2.2wt% Al 2 o 3 powder, 11.7wt% phenolic resin and 86.1wt% SiC powder. Other steps and parameter are identical with specific embodiment 1;

[0063] figure 1 The SEM image of the cross-section of the silicon carbide ceramic prepared by in-situ synthesis of aluminum nitride and carbon as sintering aids for specific example 3, it can be seen that there is a uniformly distributed second phase in the silicon carbide ceramic;

[0064] figure 2 The elemental analysis figure of the silicon carbide ceramics of sintering aids for the in-situ synthesis of aluminum nitride and carbon prepared in specific embodiment 3; from figure 2 It can be seen that silicon carbide ceramics contain Si, Al, C and O elements, and N elements are not detected due to the detection limit. They are all elements with small neutron absorp...

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Abstract

The invention relates to a preparation method for compact silicon carbide ceramics free of boron or rare earth elements. The preparation method comprises the steps of 1, evenly mixing, drying, grinding and screening an aluminum source, a carbon source, silicon carbide powder and absolute ethyl alcohol to obtain mixed powder, pressing the mixed powder to obtain ceramic biscuits; 2, carrying out heating and pyrolysis on the ceramic biscuits in vacuum at 650DEG C-1050 DEG C; 3, subjecting the ceramic biscuits to a carbon thermal reduction reaction in nitrogen atmosphere at 1550 DEG C-1750 DEG C; 4, sintering the ceramic biscuits obtained after the carbon thermal reduction reaction in inert atmosphere at 2050 DEG C-2300 DEG C to obtain the compact silicon carbide ceramics. The silicon carbide ceramics prepared through the preparation method contain Si, Al, C, O and N elements all of which have small neutron-absorption cross-sections, and the silicon carbide ceramics do not contain the B or rare earth elements having large neutron-absorption cross-sections.

Description

technical field [0001] The invention relates to a method for preparing dense silicon carbide ceramics without boron or rare earth elements, and belongs to the technical field of structural ceramics. Background technique [0002] Silicon carbide ceramics have excellent properties such as high strength, high hardness, high thermal conductivity, high wear resistance, high temperature stability, and corrosion resistance, and are widely used in machinery, chemical and other fields. Silicon carbide has a low neutron absorption cross-section and good high-temperature stability, and is a very promising structural material in fourth-generation nuclear power systems. Silicon carbide is a covalent bond, and sintering is very difficult. It is usually necessary to add a small amount of sintering aids to promote sintering densification. The commonly used sintering aids are B 4 C+C, AlN+B 4 C+C, AlN+RE 2 o 3 (RE=Y, Nd, Lu and other rare earth elements), Al 2 o 3 +RE 2 o 3 Wait. Th...

Claims

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Application Information

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Patent Type & Authority Patents(China)
IPC IPC(8): C04B35/565C04B35/622
Inventor 刘桂玲苏碧哲黄政仁刘学建陈忠明杨勇姚秀敏
Owner SHANGHAI INST OF CERAMIC CHEM & TECH CHINESE ACAD OF SCI
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