EPR-Characterization of Carbon Inclusions in Boron Carbide

摘要

The dependence of the EPR line width (ΔB) with g = 2.0028 in boron carbide from the contents of free carbon, c_C, is used for characterization of surface condition of carbon inclusions. Consecutive reduction of c_C was carried out by a method of low-vacuum oxidation at various temperatures. The amount of a free carbon (a graphite phase) in samples was measured by the X-ray method. The analysis of ΔB(c_C) changes has shown, that at a surface layer of polycrystalline boron carbide particles there are inclusions of free carbon, for which relation S/V in 2 times smaller, than for inclusions located in volume of particles. Is established that the value of the activation energy, ΔE, of thermal generation of free charge carriers for superficial inclusions of carbon is more than for the carbon inclusions in volume of the boron carbide particles.