# Univesity of Toledo Vacancy Diffusion & Interstitial Diffusion Mechanism Questions

Description

5.9 A sheet of steel 1.5 mm thick has nitrogen atmospheres on both sides at 1200°C and is permitted to achieve a steady-state diffusion con- dition. The diffusion coefficient for nitrogen in steel at this temperature is 6 × 10?11 m2/s, and the diffusion flux is found to be 1.2 × 10?7 kg/m2s. Also, it is known that the concentration of nitrogen
3 in the steel at the high-pressure surface is 4 kg/m .
How far into the sheet from this high-pressure side will the concentration be 2.0 kg/m3? Assume a lin- ear concentration profile.

5.9 A sheet of steel 1.5 mm thick has nitrogen
atmospheres on both sides at 1200°C and is
permitted to achieve a steady-state diffusion con-
dition. The diffusion coefficient for nitrogen in
steel at this temperature is 6 x 10-11 m²/s, and the
diffusion flux is found to be 1.2 x 10-7 kg/m².s.
Also, it is known that the concentration of nitrogen
in the steel at the high-pressure surface is 4 kg/m².
How far into the sheet from this high-pressure side
will the concentration be 2.0 kg/m?? Assume a lin-
ear concentration profile.
Diffusion Mechanisms
5.3 (a) Compare interstitial and vacancy atomic
mechanisms for diffusion.
(b) Cite two reasons why interstitial diffusion is
normally more rapid than vacancy diffusion.