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Vacuum Sintering Process of Boron Carbide Ceramics

Boron carbide is an important special ceramic, which has many excellent properties and has been widely used. Boron carbide has a series of excellent properties, such as low density, high hardness and stable chemical properties. At the same time, boron carbide has a strong ability to absorb neutrons. Based on these excellent characteristics, boron carbide has been widely used in many fields. It is mainly used in five aspects: structural materials, chemical raw materials, electrical properties, nuclear properties and composite ceramics.

Application of boron carbide as structural material

This is the main application field of boron carbide materials in industry. On the one hand, boron carbide is used as abrasive. It can be used in industries from the powder with a particle size of 1 im to the small ball with a diameter of 10 mm. For example, the cost of the grinding process can be greatly reduced by using boron carbide as the grinding material in the polishing, fine grinding or crushing process of other hard materials, such as cemented carbide and engineering ceramics, instead of the diamond abrasive used previously. On the other hand, boron carbide devices with wear resistance and corrosion resistance are made by powder metallurgy, and have achieved good application results in many fields. For example, boron carbide devices can be used as pneumatic slide valves, hot extrusion dies, and journal bearings of cooling systems in atomic power plants. It is used as a corrosion and friction resistant device in ceramic gas turbines. Sand blasting nozzle and high-pressure water jet cutting nozzle. Boron carbide is also an excellent gas bearing material in long-life gyroscope. As boron carbide is stable to molten iron and has good thermal conductivity, it can be used as continuous casting mould in mechanical industry. Because boron carbide material can resist strong acid corrosion and wear, it can be used as the flow transmitter tip of rocket liquid engine fuel. In addition, the externally applied boron carbide material can also be used as cutting blade, mortar, tamper, etc. Boron carbide can also be used as a light armored bulletproof vest for helicopters.

Application of Boron Carbide as Chemical Raw Material

Boron carbide powder, activated by halogen, can be used as a boronizing agent for steel or other alloys to boronize the steel surface to generate a thin layer of iron boride to enhance the strength and wear resistance of the material. Boron carbide can also be used as a non-metallic additive for some metal based friction materials. When boride powder is prepared by reduction and combination method, boron carbide can be used as the boron source to prepare TiB2, ZrB2, CrB2 and other powders, which is called the “boron carbide method” for powder preparation.

Application of electrical properties of boron carbide

The boron carbide graphite thermocouple consists of a graphite tube, a boron carbide rod and a boron nitride bushing between the two. In inert gas and vacuum, the operating temperature is up to 2200 ℃. Between 600 ℃ and 2200 ℃, the linear relationship between potential difference and temperature is good.

Application of boron carbide in nuclear properties

In the core assemblies of nuclear reactors, neutron absorbing materials (control rods, control rods, accident rods, safety rods, shielding rods) are important functional elements second only to fuel elements. Boron carbide has high neutron absorption cross section, wide absorption energy spectrum, low price, rich raw materials, and no strong secondary radiation of radiation after neutron absorption, so the waste is easy to be treated. Therefore, boron carbide is an important neutron absorbing material.

Boron carbide composite ceramics

Silicon carbide has good mechanical and physical properties, including high specific strength, specific modulus, good corrosion resistance and thermal shock resistance, low density and thermal expansion coefficient. At the same time, adding appropriate amount of boron carbide to silicon carbide can obtain a more compact sintered body. The composite ceramics can better maintain the excellent physical and mechanical properties of boron carbide ceramics while reducing the sintering conditions of boron carbide ceramics. B4C SiC ceramic is considered as a kind of high temperature corrosion resistant and wear-resistant material with broad application prospects, and has been applied in industrial nozzle, pump seal, hot extrusion die and other fields.

Preparation of boron carbide ceramics

The main preparation process of boron carbide ceramics is the typical powder metallurgy process of powder preparation, molding and sintering. The forming and sintering methods mainly include atmospheric sintering, hot pressing, activated sintering, etc. The pressureless sintering and hot pressing sintering are common methods for preparing pure boron carbide ceramics. The ideal boron carbide ceramic products are made by high temperature vacuum sintering furnace.

Sintering Preparation of Boron Carbide

Boron carbide is a compound with strong covalent bond, so its sintering performance is very poor. The pressureless sintering temperature without any additives is about 2300 ℃. When Al and Si are used as sintering aids, boron carbide ceramics can be obtained by atmospheric sintering at 2050 ℃.

The pressureless sintered boron carbide ceramic material without additives is a process method suitable for mass production of parts with complex shapes. For powder, the method of adding sintering aids is usually used to improve the sintering behavior of boron carbide, which is cheaper and more practical. boron carbide products.

Selection of sintering equipment: The RVS series vacuum sintering furnace produced by SIMUWU is suitable for vacuum sintering furnaces including boron carbide and silicon carbide ceramics. It has the advantages of good temperature uniformity, good sealing, high vacuum, etc. It is an ideal product for machining boron carbide ceramics.