To develop novel dispersants for submicrometer-sized Si3N4 powder, the surface chemistry of a powder has been investigated using thermodesorption, carrier-gas heat extraction, X-ray photoelectron spectroscopy, diffuse reflectance infrared Fourier transform spectroscopy, and zeta potential measurements. This study indicates that the powder surface is composed mainly of silanol groups and exhibits acidic behavior, Furthermore, the interaction affinity of various surface probe molecules with the powder surface has been studied using adsorption isotherms. The detailed description of the surface chemistry can be used as a guide for designing efficient dispersants, as will be presented in part II.