The element synthesis of metal borides

Someone had been prepared molybdenum boride in a molybdenum crucible, the temperature is 1300~2050. Someone also prepared molybdenum boride in graphite crucible and hydrogen, the temperature is 1500 ~1700. With a purity of 99% molybdenum powder and 83% to 85% boron powder can be obtained a purity of 96% to 98 % product, most of the impurities removed by evaporation while sintering. Some people prepared molybdenum boride and europium boride using the method that: in an evacuated quartz tube heating a mixture of boron and metal to 1200 and heat preservation for 48h, or in vacuo heated the same mixture in 1500-1600 MgO crucible for a few minutes. Prepare chromium boride is in vacuum induction furnace heated to above 1600 to smelt a mixture of chromium and boron, or sintering the powder mixture in the 1150evacuated quartz tube for 48 ~ 72h.When the 1150 sintered time increasing to 20 days, can obtain single crystal, the raw material is 99.4% electrolytic chromium and 98%-99% boron powder. This boron powder is obtained by used hydrogen reduce boron tribromide in the quartz tube, the reduction temperature is 750 ~ 800.

Preparation of zirconium boride is melted the element in a vacuum induction furnace; zirconium boride is hard gray crystals, there are three components that is, zirconium boride, zirconium diboride, three zirconium boride, only zirconium diboride in a very wide temperature range is stable. Industrial production is mainly the zirconium diboride. Zirconium diboride is hexagonal crystal, gray crystal or powder, relative density is 5.8, melting point is 3040. Thermostability, the strength under normal and high temperature are very high. Good thermal shock resistance, low resistance, high temperature oxidation. The temperature is about 3000, with metallic luster, have metallicity, resistance is slightly lower than the metal zirconium, after heating in a wide temperature range is stability. Although melting point is high, but can be sintered at lower temperature. Prepared by the mixture of metal zirconium, boron carbide, boron nitride heated to 2000 in argon. It can be used as aerospace high temperature materials, wear-resistant smooth solid materials, cutting tools, temperature thermocouple protection tubes and the electrode materials of electrolysis molten compound, particularly suitable for using as the ball bearing surface.

Preparation of boride powder is vacuum sintering the mixed powder under 1800 ~ 1900 for 0.5h, or at 1150vacuum quartz tube sintered 100 ~ 150h; the manganese boride prepared is at 1100 ~ 1200 sintered 48 ~ 72h, if you need to get a single crystal should heat preservation 7 to 10 days. Directly at 2850 hot-press the mixture of metal powder and boron powder, can be obtained the boride components with the same dense as hot-press boride powder.

Dense boride components and boride coatings were able to through restore or thermal decomposition of boron halide and a metal halide vapor in the hot surface to obtain, or in the hot metal surfaces to restore or replace boron halides, and make the boron diffused into the metal matrix, of course, the latter method may be formed eutectic on the metal boron substrate. Some eutectic’s melting point is lower the pure boride or metal, thereby reducing the heat resistance of the obtain coating.

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