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The Preparation Methods Of Amorphous Boron Powder

2018-8-27      View:

Ultrafine amorphous boron powder is an ideal high-energy additive for lean oxygen-rich fuel propellants and is a high-energy solid fuel. It is widely used in the synthesis of new materials. It is used as a boron-rich fuel because of its large specific surface area and high combustion heat value. It is also used as an initiator for safety balloons. Solid rocket stamping engines are suitable for use with oxygen-poor propellants. Adding metal fuel is an important development direction for high-energy oxygen-poor propellants.

 

Amorphous boron powder can be prepared by molten salt electrolysis, diborane cracking, boron halide hydrogen reduction and metal thermal reduction. Song Mingzhi et al. used boron chloride, potassium fluoroborate and boron oxide molten salt system to obtain boron powder with a purity greater than 90%. However, due to the low current efficiency, poor working environment and discontinuous production, molten salt electrolysis did not Further development. Although diborane pyrolysis and boron halide hydrogen reduction can obtain high-purity boron powder, the harsh operating environment and serious pollution restrict the application of the method.

 

Molten Salt Electrolysis is a metallurgical process in which the salts of certain metals are melted and electrolyzed as an electrolyte to extract and purify metals. The two most commonly used boron-containing compounds are boron oxide and boron fluoride metal salts. The borane cleavage method is used to prepare amorphous boron powder, which is obtained by redox reaction of sodium hydride and trifluorocarbonate to form diborane, and then cleavage of borane at 30 to 900 ° C to obtain amorphous boron.

 

The pyrolysis method is a method of preparing a boron powder by heating a boron-containing compound at a high temperature. The boron powder obtained by this method has a purity of more than 99% and a particle size of 0.8 to 10 um, but the reaction period is relatively long, the process conditions are harsh, and the yield is small, which is not suitable for industrialization. The metal thermal reduction method was the earliest method discovered at the earliest, and it is also the main method currently used in industry.

 

It has been found through research that the use of molten salt electrolysis and self-propagating magnesium thermal reduction or aluminothermic reduction is the main method for preparing amorphous boron powder today. However, it is desirable to prepare higher purity by using simple, convenient and low cost conditions. Amorphous boron powder needs further research.