Abstract: Method for producing .alpha.-silicon nitride whiskers. Silicon is blended with composition particles able to sublime without leaving a residue, such as naphthalene particles. The blend is compacted to a desired shape, after which the composition particles are sublimed from the blend to form a porous silicon precursor compact having the desired shape. The silicon precursor is reacted with a substance that releases free nitrogen, such as nitrogen or dry ammonia. The reaction is carried out at a temperature sufficiently high to form an identically shaped porous compact of .alpha.-silicon nitride whiskers but sufficiently low to avoid subliming substantially all of the formed whiskers. Preferably, the reaction is carried out in a range between about 2100.degree. F. and 2750.degree. F. The shaped porous compact of .alpha.-silicon nitride whiskers may be impregnated with a resin binder, a liquid metal, a colloidal suspension, an ionic solution or a gaseous material to form an isotropic composite.