Simultaneous Synthesis and Dispersion of Ultra-fine Particles with the Use of Surfactant Having the Function of Nano-scale Surface Biomechanism

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In order to uniformly disperse ultra-fine particles simultaneously with synthesizing processes, a new aqueous surfactant with a high hydrophilic group density and special cis-structure was prepared from a microbial product and added to reactant solution. Barium titanate size of sol-gel synthesis was tested and the addition of the surfactant made it possible to decrease the the aggregates in suspension as well as the sedimentation velocity while maintaining the stoichiometric composition. The optimum additive content to obtain the minimum aggregate size of about 100-200nm in diameter and the highest dispersion stability in suspension while maintaining the stoichiometric composition of prepared ultra-fine BaTiO_3 particles without other phases was determined at about 7.1wt%. Because the excess addition of this surfactant at more than 8.5wt% inhibited the uniform synthesis of BaTiO_3 particles, an amorphous phase with a highly specific surface a and a BaCO_3 phase formed in the synthesize … More d particles. An acrylic oligomer surfactant, which had a similar molecular weight and similar high density in hydrophilic carboxyl groups to the microbial-derived surfactant was also tested and BaTiO_3 nano-particles with a high dispersion stability in suspension can be prepared. The same microbial derived surfactant was applied also to the synthesis of CaCO_3 and hematite and particles with several nanometers in diameter with less sedimentation characteristics were produced. The mechanism of anionic polymer dispersants in dense ceramics powder suspension, such asn Si_3N_4, Sic, TiC was investigated by atomic force microscopy (AFM) with the aid of newly prepared colloidal probes. Copolymer of ammonium acrylate and methyl acrylate with different hydrophilic to hydrophobic group ratios, m : n, was prepared and added to the suspension. Microscopic surface interaction between a particle and a plate made of porous sinters of the particles in surfactant solution was characterized by using colloidal probe AFM. The relationships between macroscopic suspension viscosity and the microscopic surface interaction were analyzed. Based on these results, the adsorption mechanisms of polymer dispersant on ceramic powders and hetero-coagulation phenomena in suspension were discussed. Less