diffusionfree

Diffusionfree is a term used in physics and materials science to describe conditions under which diffusion-driven transport is negligible on the timescale of interest. A diffusionfree regime occurs when atomic, molecular, or thermal diffusion is effectively suppressed, so that composition and temperature gradients do not change appreciably during observations.

Key determinants include very low temperatures, high-viscosity or glassy states, high activation energies for diffusion, and confinement within nanoscale structures that hinder transport. In practice, diffusionfree is an approximate description; the diffusion coefficient may be so small that, for the duration of the experiment, diffusion can be neglected.

Applications and implications: In kinetic studies, assuming diffusionfree transport separates chemical reaction rates from mass transport effects; in materials processing, diffusionfree conditions can stabilize metastable phases or microstructures; in modelling, the diffusion term is omitted to simplify equations for short timescales.

Limitations: The term is timescale-dependent and context-dependent; at longer times or higher temperatures diffusion becomes relevant; the concept does not imply perfect immobility.

Related topics include diffusion, diffusionless transformations, and glass transition.