Explanation

The phenomenon of atomic migration caused by thermal vibration. The macroscopic flow of substances due to chemical concentration gradient in the system is called chemical diffusion. Achieve uniform chemical composition of the system through material transportation; The migration process that occurs solely due to thermal vibration without a chemical concentration gradient is called self expansion. In addition, diffusion can be caused by temperature gradient, stress field and electric field. diffusion is a very common phenomenon in nature. diffusion coefficient (D), as the most basic physical quantity representing the speed of diffusion of matter, can be given by Fick's law. The study of diffusion phenomenon involves many physical and chemical processes related to atomic movement in materials science, such as phase transition process, chemical process dynamics, and also provides the most basic information about the energy required for the formation and movement of crystal defect.

Classification