Influence of chemical pretreatment on the surface properties of silicon nitride powder

Adsorption energy distributions for nitrogen at the surface of silicon nitr ide samples with different pretreatment have been obtained and related to t he heats of adsorption determined by Brunauer-Emmett-Teller analysis of ads orption isotherms. This has confirmed the conjecture that, in normal condit ions, the surface of silicon nitride is covered by a layer of silica, as su ggested by earlier studies. An attempt to correlate adsorption data with ab initio potentials of the adsorbate-adsorbent interaction has been made. Th e charge-regulated behaviour of the surface of silicon nitride in aqueous e lectrolytic solutions has been investigated in relation to charge titration and electrokinetic experiments. An important role of surface hydrolysis in the interpretation of experimental data has been pointed out. Based on the surface ionization parameters extracted from charge titration data, interp article forces governing the stability of colloidal dispersions have been c alculated in the framework of Derjaguin's approximation. (C) 1999 Elsevier Science B.V. All rights reserved.