Modelling of the interparticle contacts distribution for the evaluation of the components interaction in reaction mixture of mechanically synthesized TiB₂―MoSi₂ powder

Abstract

The influence of the reaction mixtures composition on the features of the mechanosynthesis of 80% (mass) TiB₂―20% (mass) MoSi₂ composite powder has been investigated, and the mathematical modeling of the contacts distribution between powder particles in the reaction mixtures has been performed. It has been established that it is impossible to obtain two-phase composite powder of composition 80% (mass) TiB₂―20% (mass) MoSi₂ by mechanosynthesis of reaction mixtures with the initial components Ti + B + Mo + Si, and the product is a mixture of the TiB₂, Mo₃Si, Mo₅Si₃, and MoB₂ phases. The calculation of the interparticle contacts distribution in the mixture of Ti, B, Mo, and Si powders in the concentration range 80% (mass) TiB₂―20% (mass) MoSi₂ revealed the insufficient mean number of contacts between molybdenum and silicon particles, which prevents the development of the MoSi₂ synthesis reaction. This is explained by the effect of a coarse-grained titanium fraction and high content of titanium and boron particles, whose total mass fraction is equal to 80% (mass). In the case of the ternary Ti + B + MoSi₂ reaction mixture, the two-phase composite powder forms within 30 min at a milling balls-to-powder mass ratio of 10 : 1. In this powder system the formation of TiB₂ is retarded, and pure Ti is registered in the products. This is obviously caused by the fact that the preliminarily synthesized nanosized MoSi₂ powder covers the surface of titanium and boron particles and blocks contacts between them. According to the results of calculation of the contacts distribution between the components of the Ti + B + MoSi₂ powder system, the mean number of Ti―B-type contacts decreases by one third as compared to that for the first mixture. The results of mathematical modeling of the contacts distribution between powder particles in the reaction mixtures agree well with experimental results of mechanosynthesis. The conclusion on the reasonability of per¬forming preliminary mathematical modeling of powder systems for the evaluation of the synthesis realization probability in the composite materials preparation by the mechanosynthesis method has been made.