A plurality of carbide, such as silicon carbide, tungsten carbide, etc.,
nanofibrils predominantly having diameters substantially less than about
100 nm and a method for making such carbide nanofibrils. The method
includes the steps of: heating a plurality of carbon nanotubes or
nanofibrils predominantly having diameters less than about 50 nm in a
reaction chamber in the presence of a gas of the form Q.sub.nA.sub.m,
where Q is a metal capable of forming a carbide, A is an element or
radical and n and m are integers necessary to satisfy valences, such as,
for example silicon monoxide, and an inert gas in a reaction vessel to a
temperature substantially less than 1700 C but sufficently high to cause
substantial reaction of the metal in the gas with the carbon of said
carbon nanotubes or nanofibrils to form, in situ, solid carbide
nanofibrils, the temperature being sufficiently low to prevent
substantial fusing together of individidual ones of said carbide
nanofibrils, removing at least a portion of A-based gas from said
reaction chamber as said reaction progresses, and maintaining said
temperature until substantially all the carbon of said nanotubes or
nanofibrils has been converted into Q-based carbide.