Structural Model of Two-Component Particulate Mixtures with Maximum Heterogeneous Contacts

Abstract

Heterodiffusion processes or chemical reactions in heterogeneous media are initiated at contact points between dissimilar particles of the reagents. Therefore, the number of heterogeneous contacts in the starting mixture is assumed to determine the rate of these processes: in particular, the rate of mass transfer in self-propagating high-temperature synthesis. The conditions for obtaining structures with maximum heterogeneous contacts have not been clearly defined so far in the literature. The paper determines for the first time the optimal ratio of particle sizes for a two-component mixture. This ratio contributes to the starting mixture composition that involves the maximum number of dissimilar contacts at a given weight or volume content of the reagents. A model of two-component densely packed disordered biparticulate granular media is proposed. According to the model, the starting mixture is considered a random packing of spherical particles of two sizes. The particle size ratio has been established so that the number of heterogeneous contacts between the particles of different phases is the highest. The concept of an ideal reaction area, which is a biparticulate structure consisting of the maximum number of dissimilar particles, has been developed and the role of the starting particle size composition in the formation of such structure has been established. An algorithm is presented for calculating the characteristics of the starting mixture to promote the structure with ideal reaction areas.