Uniformly-coated ceramic particles

A process for the preparation of suspensions of finely divided particles of a first solid which is predominantly an inorganic nitride or carbide in a fluid suspension medium which is predominantly water and with which surfaces of said first solid are chemically reactive, comprising the steps of:

• (a) mixing together particles of said first solid having a first average size, said suspension medium, and a surfactant that is (i) soluble in said suspension medium and (ii) capable of adsorbing on freshly created surfaces of said first solid at a faster rate than the suspension medium can react therewith so that the surfactant at least retards the reaction that would otherwise occur between said first solid and said fluid suspension;
• and
• (b) comminuting the solid particles in the mixture formed in step (a) to particles of a second average size which is smaller than said first average size;
• wherein no subsequent treatment is performed to remove free metal and reduce oxygen containing impurities.

A process for depositing a first solid material upon the surface of a particle of a second solid material suspended in a dispersion medium while substantially avoiding the generation of free particles of said first solid material, comprising the steps of:

• (i) providing in solution in said dispersion medium at least two distinct reagent materials that are capable of reaction to form said first solid material;
• and
• (ii) establishing an increased chemical activity of at least one of said reagents in the part of said dispersion medium in the vicinity of the surface of said second solid material, compared with the bulk of sad dispersion medium,
• whereby reaction occurs between said reagents and said first solid is precipitated upon the surface of said second solid while substantially avoiding precipitation of said first solid from the bulk of said dispersion medium.

A process for the preparation of suspensions of finely divided particles of a first solid which is predominantly an inorganic nitride or carbide in a fluid suspension medium which is predominantly water and with which surfaces of said first solid are chemically reactive, comprising the steps of

• (a) mixing together particles of said first solid, said suspension medium, and a surfactant that is (i) soluble in said suspension medium and (ii) which adsorbs onto freshly created surfaces of said first solid so that the surfactant at least retards the reaction that would otherwise occur between said first solid and said dispersion medium;
• and then
• (b) creating fresh surfaces of said first solid;
• wherein no subsequent treatment is performed on said particles to remove any chemical reaction products generated by reaction between the particles and the fluid medium.