The preparation step for extrusion (with binders) of Si 3 N 4 powder, as well as the extrusion process itself, modify the original properties of the powder so that its recovery and subsequent rework are not possible.X-ray photoelectron spectroscopy (XPS), X-ray diffraction, infra-red spectroscopy, potentiometric titrations and zeta potential determinations have been used to identify the surface modifications in Si 3 N 4 due to addition of binders, and to examine powders after elimination of the binders by extraction with organic solvents and heat treatment.The original Si 3 N 4 with binders showed a shift in zeta potential and point of zero charge (PZC) to lower pH, indicating the adsorption of organic compounds on the Si 3 N 4 surface at this step. The appearance of one O l s peak at 532 3 eV in the XPS spectrum showed the presence of Si 2 N 2 O. After extraction with organic solvents the PZC value was close to that of the Si 3 N 4 + binders (pH = 3 2), indicating incomplete removal of organics; this was confirmed by XPS determination (C l s intensity data) and chemical analysis. The presence of Si 2 N 2 O was not modified as shown by XPS and the value of the isoelectric point. Heat treatment removes the organics completely but produces an oxidation of Si 3 N 4 to SiO 2 as evidenced by a shift in the binding energy of the O l s photopeak to 534 0 eV.