Significantly improved reaction kinetics and properties have been realized for reaction bonded Si3N4 (RBSN) by using Si powders having unusual physical and chemical characteristics combined with clean, oxygen-free processing conditions. For instance, complete nitridation can be achieved in < 1 h at 1150°C or < 100 m at 1250°C without pre-nucleation, or < 1 h at 1100°C with pre-nucleation. These compare with normal schedules of ∼100 h at 1470-1500°C. Resulting strengths (up to 870 MPa) and oxidation resistances of the RBSN essentially equal those of fully dense Si3N4 even though RBSN includes 25% open porosity. The results show that every aspect of the process, ranging from powder synthesis to < ppm levels of oxygen in the nitriding atmosphere, have demonstrable effects on the reaction kinetics and the resulting properties of the parts. With careful processing, reaction formed ceramics can compete advantageously with fully dense counterparts.