|Differential thermal analyzer
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In the diffusion between solid bodies, such as during soldering, E activation energy is necessary for the atoms to change their position. If a is the interparticle distance and k the Boltzmann constant, we obtain D=a2τ0 exp(Ek T) as the diffusion coefficient, which is known to be strongly temperature dependent. The size 1τ0 indicates here the jump rate of the particles. For example, the diffusion coefficient of C in Fe is around 0,02-0,1 cm 2 /day at 1000 ° C. See also Fick's laws of diffusion.