Mechanochemical synthesis of boron carbide powder obtained from a mixture of carbon black and boron amorphous, its structure and properties
The most promising for production of highly dispersed nanopowder of boron carbide is the use of mechanochemical method. During processing in the mill energozatratno-mechanoreceptors, along with the dispersion, the interaction between initial substances (mechanochemical synthesis), causing the formation of new phases. Under optimal conditions of realization of the process of mechanically synthesized phases are in the ultrafine state with a highly developed surface of grain boundaries and subgrains with nano- or microcrystalline structure, which will increase its density after vibration compaction, thereby to reduce the rate of burnout and slow down the decrease of absorbing properties under the action of neutron irradiation. The aim of this work was the study of the structure and properties of powders of boron carbide obtained by mechanochemical treatment of soot and amorphous boron. As starting materials for the synthesis of boron carbide was used carbon black type PM - 15 and amorphous boron grade A in a stoichiometric ratio. Mechanochemical synthesis was carried out using a planetary ball mill "Activator 2S" when the rotational speed of planetary disk is 600-900 rpm and speed reels 1000-1800 rpm, when the ratio of the mass of balls to mass of mixture is 30 to 45:1 in argon atmosphere at P = 3 - 5 ATM. in the course of 5-120 minutes. The results of the research showed the possibility of obtaining nanosized powder of boron carbide by mechanochemical treatment of soot and amorphous boron. The methods of raster electronic spectroscopy, Raman spectroscopy (Raman spectra), PAM, powder x-ray diffraction studied the structure and properties of powders of boron carbide. It is shown that complete conversion of the starting materials (soot and amorphous boron) in the boron carbide (В4С) occurs during mechanical treatment of the mixture within (30-60) min. Microelectrospray powder В4С received by mechanosynthesis, has a characteristic rentgenologii phase ring structure with some inclusions of the crystalline phase.