Concentrated colloidal suspensions of monodispersed silica particles have been examined to identify the dominant model of shear-thickening behavior of concentrated colloidal suspension. The suspending media were changed from an aqueous medium to highly viscous suspending media using ethylene glycol group organic solvents, poly ethylene glycol, and water/poly ethylene glycol co-solvents. Colloidal suspensions of monodispersed silica particles formed colloidal crystals and exhibited shear-thinning flows. With the change of the suspending medium from an aqueous medium to ethylene glycol group organic solvents, the suspensions exhibited shear-thickening behavior under high shear rates. Although the shear rate at the onset of shear-thickening occurred decreased in accordance with increases in the suspending media viscosity, the shear stress at the onset of shear-thickening behavior occurred was defined regardless of the suspending media viscosity. In addition, the critical shear stress depended on the square reciprocal of the particle size. Overall behaviors derive that shear-thickening behavior of concentrated colloidal suspensions of monodispersed silica particles can be explained by the diffusion-friction-dominant model.
The color tone of pigments is affected by various factors such as crystal structure and particle size. These characteristics should be determined by synthesis condition. In this study, the influence of cobalt source on the color tone of cobalt blue pigment was investigated. Cobalt blue (CoAl2O4) was synthesized by solid-state reaction method. Co3O4 and Co(OH)2 with two different particle sizes were used as the cobalt source, and γ-Al2O3 was used as the aluminum source. The products were characterized by spectrophotometry, XRD, SEM, and TG/DTA. It was revealed that the chroma of the synthesized cobalt blue depends on the cobalt source. The cobalt blue synthesized using smaller size Co(OH)2 showed most vivid color. It was suggested that the number of the contact points between the starting materials increased with decreasing the particle size, leading to the progress of the reaction.
Mechanochemistry is a study that deals with the interaction between mechanical energy and chemical energy. Mechanochemical reaction is a chemical reaction by mechanical energy. We have synthesized various next-generation battery materials using the mechanochemical method and evaluated their unique properties. In this paper, we review our recent researches on mechanochemical syntheses of sulfide materials as next-generation battery materials.
Functional nanoparticle syntheses by thermal plasmas are reviewed. The advantages of thermal plasmas, such as high enthalpy, high chemical reactivity, and rapid quenching capability, have brought the advances and demands in plasma processing. Recent researches by DC arc, multiphase AC arc, and induction thermal plasma are summarized. Metal, intermetallic compounds, oxide, nitride, and boride nanoparticles are successfully synthesized by thermal plasma method. In particular, nanomaterial synthesis for the utilization in lithium-ion battery are summarized. Attractive nanomaterials related to cathode, anode, and electrolyte are successfully synthesized by thermal plasmas. High-productivity of the nanoparticles by thermal plasmas for industrial utilization can be achieved by improving energy efficiency and solving electrode erosion issue.