Using mechanochemical treatment to obtain metal powders for energy-intensive combustible compositions. 2. Structure and reactivity of mechanically activated Al–modifier–SiО2 mixtures

The paper presents the results obtained when studying particles of aluminum-modifier-quartz composites by different physicochemical methods after mechanochemical treatment (MCT) in a planetary centrifugal mill. Graphite (C), polyvinyl alcohol (PVA) and stearic acid (SA) were used as modifiers. To increase the dispersibility of plastic metal powders in the composition (modifier metal), MCT was carried out in the presence of quartz with its mass fraction in the composite ranging from 5 to 20 %. The most significant grinding of aluminum particles was observed with an increase in the graphite content from 5 to 20 %, and SiO2 from 5 to 10 % in the composition of aluminum-modifier-quartz composites. The particle size decreases, while the crystallite size increases with an increase in the quartz content in the composite during the Al–SA–SiO2 system MCT. Al–SA–5%SiO2 showed the maximum defectiveness of aluminum after MCT. For the Al–PVA–SiO2 composition after MCT, an increase in the particle size and, accordingly, a decrease in the specific surface were observed at sufficiently low crystallite size values. It was shown that with an increase in the quartz content in the system, the defective crystal structure of aluminum particles increases as a result of MCT. In this case, the synthesized powder material is a composite formation of aluminum and quartz particles bound by a polymer obtained from polyvinyl alcohol. As a result of Al–modifier–SiO2 mixture MCT, powder activity increases due to the accumulation and redistribution of defects in aluminum particles, as well as changes in the surface structure occurring after modifying additives penetration into the oxide layer to be destroyed. A conceptual model for the transformation of the surface layer and subgrain structure of aluminum particles as a result of MCT is presented.