Pioneers and Landmarks of Diffusion

Abstract

The science of diffusion had its beginnings in the 19th century, although the blacksmiths and metal artisans of antiquity already used diffusion phenomena to make such objects as iron swords and gilded bronze wares. Diffusion as a scientific discipline is based on several corner stones. The most important ones are: (i) The continuum theory of diffusion originated from the work of the German physiologist Adolf Fick, who was inspired by elegant experiments on diffusion in gases and of salt in water performed by the Scotsman Thomas Graham. (ii) The Brownian motion, observed for the first time by the British botanist Robert Brown, was interpreted decades later by Albert Einstein and almost at the same time by the Polish physicist Marian Smoluchowski. Their theory related the mean square displacement of atoms to the diffusion coefficient. This provided the statistical cornerstone of diffusion and bridged the gap between mechanics and thermodynamics. The Einstein-Smoluchowski relation was verified in tedious experiments by the French Nobel laureate Jean Baptiste Perrin and his coworkers. (iii) The atomistics of solid-state diffusion had to wait for the birthday of solid-state physics heralded by the experiments of the German Nobel laureate Max von Laue. Equally important was the perception of the Russian and German scientists Jakov Frenkel and Walter Schottky, reinforced by the experiments of the American metallurgist Ernest Kirkendall, that point defects play an important role for properties of crystalline substances, most notably for those controlling diffusion and the many properties that stem from it. This paper is not meant as systematic history of diffusion. It is devoted to some major landmarks and eminent pioneers of diffusion including also people from recent decades until today.