Mesoporous fibrous silicon nitride by catalytic nitridation of silicon

The catalytic effect of metal oxide/alumina whiskers (CeO₂, Mn₃O₄, NiO, Co₃O₄, Fe₂O₃, Cr₂O₃/AW) was evaluated on their ability to drive the nitridation of silicon and to generate mesoporous fibrous silicon networks. Silicon powder with different particles size along with the catalyst was nitridized at 1300 °C for 5 h in nitrogen and nitrogen diluted with 10 vol% ammonia atmospheres. Nitridation degree of silicon up to 99% was recorded using 1.5 wt% CeO₂ and Fe₂O₃ catalysts in nitrogen-ammonia atmosphere. The catalyzed samples contain submicronic silicon nitride fibres with a diameter of 400–500 nm and a length of up to few micrometers. The compressive strength of 46 ± 1 MPa was measured for silicon samples catalyzed with nickel oxide/alumina whiskers and nitridized in N₂/10 vol%NH₃ atmosphere. Porous silicon nitride networks were produced with 45–52% porosity, pore sizes in the range of 370–1200 nm and median pore in the range of 495–1655 nm.