Abstract: A method of manufacturing nitrided silicon parts by sintering a silicon powder containing aluminium under an atmosphere rich in nitrogen. A small quantity of carbon monoxide is added to the nitrogen atmosphere and the nitrogen and carbon monoxide partial pressures and the aluminium content of the silicon powder are chosen so that the oxidation reaction by the carbon monoxide on the nitrided silicon formed in the surfaces layers of the parts maintains therein an open porosity which is sufficient to allow the nitrogen to penetrate to the cores of the parts until the parts are homogeneously nitrided. Application to the manufacture of parts which must retain good mechanical strength at high temperature.

Abstract: Method of manufacturing silicon nitrides with a general formula of Si.sub.6-z Al.sub.z O.sub.z N.sub.8-z, in which z is a number less than or equal to 2.8. Silicon nitride is made to react at a temperature higher than 1600.degree. C. and in the finely divided state on aluminium oxynitride, and in the presence of an agent which generates gaseous silicon monoxide. Application to the manufacture of hard materials of high resistance to oxidation and to creep at high temperature.