Fabrication of Porous Iron with Directional Pores through Thermal Decomposition of Chromium Nitride

摘要

Lotus-type porous iron with long directional pores was fabricated by a continuous zone melting technique through thermal decomposition of chromium nitride Cr1.18N. Nitrogen decomposed from the nitride powders dissolves in the molten iron. Insoluble nitrogen evolves the directional gas pores when the melt is solidified in a direction. The porosity increases with increasing transference velocity, while the pore diameter is almost constant. The porosity change with the transference velocity is attributed to the difference in decomposition rate of chromium nitride. The compound Cr1.18N is composed of CrN and Cr2N, the latter of which is considered to evolve the pores because of the coincidence of heating rate of the continuous zone melting with that for the decomposition of Cr2N.