3-D Laser Confocal Microscopy Study of the Oxidation of Nd-Fe-B Magnets in Atmospheric Conditions.

摘要

3D confocal microscopy conducted at room temperature and in a normal laboratoty atmosphere has shown that, in the unmagnetised state, the corrosion process is nucleated and confined to the Nd-rich grain boundary triple points of the exposed NdFeB surfaces. Over a 6 hour period it is observed that the growth of the reaction zone is predominantly vertical rather than lateral in nature. Small platelets with a lateral extent of approximately 1.7 μm~2 are evident immediately after transfer from the inert atmosphere of the glove box. An increase in step height of approximately 0.15μm occurs in less than 60 seconds which then grows to a height of 0.7 μm over 6 hours. A diffusion coefficient of 3x10~(-13)cm~2/sec has been calculated which is large for a process occuring at room temperature. Raman spectroscopy indicates that the platelets contain a mixture of Nd_20_3 and Nd(OH)_3.