A method for preparing deagglomerated fibres and/or particles and for providing the fibres and/or particles with a substantially uniform protective coating, the fibres and/or particles being of a material selected from the group consisting of carbides oxides, nitrides, silicides, borides, metals and graphite, including SiC, TiC, ZrC, WC, NbC, AlN, TiN, BN, Si.sub.3 N.sub.4, MgO, Al.sub.2 O.sub.3, SiO.sub.2, ZrO.sub.2, Fe.sub.2 O.sub.3, Y.sub.2 O.sub.3, steel, tungsten, molybdenum and carbon, the method comprising (a) preparing an inorganic colloid sol, and (b) mixing the fibres and/or particles are deagglomerated and substantially homogeneously distributed. The fibres and/or particles, e.g. SiC whiskers provided with an aluminum oxide coating by treatment with an aluminum hydroxide-based sol, are used for the preparation of metal matrix composite materials, e.g. based on aluminum or an aluminum alloy.