Transport of heat and mass
Growth and coarsening of particles or precipitates in a matrix require the transport of heat or mass or both simultaneously. Heat and mass can be transported by diffusion, where heat diffusion in a crystal occurs by the random transport of enthalpy via electrons and phonons, quantized lattice vibrations, with a direction set by the temperature gradient, where heat always flows from high to low temperatures. Mass diffusion occurs in crystals by a random walk of atoms utilizing lattice vacancies. The details on heat and mass transport are discussed in standard textbooks on solid state physics and material sciences. In liquids heat and mass can be transported by diffusion, convection, or both. To describe the diffusion process we derive the conservation equations for heat and mass under diffusive and convective-diffusive conditions. These basic equations are later used for particle growth and coarsening.
KeywordsConvection Enthalpy Incompressibility
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