Preparation of highly dispersed core–shell α′′-Fe₁₆N₂/SiO₂ particles using hydroxyapatite as a sintering prevention layer

Highly dispersed core–shell α′′-Fe16N2/SiO2 particles were prepared using hydroxyapatite (HAp) as the sintering prevention layer. HAp was effective as anti-sintering agent, and could be dissolved by solutions with wide pH range. The α′′-Fe16N2 phase was formed by reduction and nitridation, in spite of the presence of SiO2 and HAp. HAp was effective to prevent the aggregation of the core–shell α′′-Fe16N2/SiO2 particles resulted from the elimination of the surface Si–OH of silica shell layer. The HAp was successfully removed using the citric acid without the degeneration of the SiO2 shell layer and α′′-Fe16N2 core particles.