Nanoparticles are synthesized in various ways, but the thermal plasma method, which is a rapid cooling process from a very high-temperature reaction field, has the potential to produce nanoparticles that cannot be obtained using other methods. In the thermal plasma method, the particle size can be controlled by the cooling rate, and the crystalline phase can be controlled by the type of plasma gas for some materials. It is also possible to synthesize superhard materials such as nitrides and carbides of metals, as well as metal nanoparticles with a core-shell structure. This paper introduces the synthesis of these nanoparticles by thermal plasma method.

Outline, principle of operation and applications on milling, particle design devices and measuring instruments were explained. Those are used in production facilities for energy materials, materials for environmental loading reduction, information equipment materials where technological development is most advanced around the world.

Grinding is a unit operation to reduce particle size by milling, and recently the demands for such operations have been increasing more and more. Computer simulation is effective in optimizing the grinding process and designing equipment, and the number of studies is increasing. To predict grinding results quickly with a low calculation load, it is useful to output the impact energy obtained from ball-only calculations as an indicator of grinding. We introduce how simulation can be used in grinding process analysis, including examples of reproducing ball behavior, predicting grinding results such as particle size distribution, and analyzing mechanochemical effects.

Polyanion-based cathode materials have been introduced as promising next-generation cathode materials for lithium-ion batteries. It has been demonstrated that nanostructured polyanion-based cathode materials can be successfully synthesized by spray pyrolysis, or a combination of spray pyrolysis and wet ball milling followed by heat treatment. Furthermore, these materials have been shown to exhibit excellent lithium battery performance.

Correlations of the interfacial and wall friction factors, f_i and f_w, and the volumetric flux of droplets, J_E, were developed based on the experimental data obtained in our previous studies on swirling annular flows in vertical pipes. The developed correlations of f_i and f_w in swirling flows consist of f_i and f_w in non-swirling flows, respectively, with effects of swirl motion. The developed correlation of J_E accurately evaluates the characteristics of J_E in swirling annular flows, i.e., it decreases with increasing the gas volumetric flux. Calculations based on a one-dimensional three-fluid model were also carried out to examine the validity of the developed correlations. The calculations reproduced well the liquid film thickness and the pressure gradient of swirling annular flows in vertical pipes and a small-scale model of a steam separator.

In recent years, the cleaning effects of FBs (Fine Bubbles) have been attracting attention. However, quantitative evaluation and clarification of the cleaning mechanism have not yet been achieved in the plumbing cleaning technology using FBs. Moreover, the effectiveness of UFBs (Ultrafine Bubbles) has not been clarified yet for plumbing cleaning either. Therefore, in this study, we used an artificially created object to be cleaned and experimentally investigated the cleaning rate, cleaning mechanism, and differences in diameter distribution of bubbles with respect to the plumbing cleaning using FBs. The results showed that not only the cleaning rates of water with MBs (Microbubbles) and water with MBs and UFBs were higher than those of tap water, but also the generation of MBs for water with UFBs may further enhance the cleaning effect compared to water with only MBs. However, under conditions where high cleaning rates could be achieved with tap water alone, the enhancement of cleaning rates with water with MBs or water with MBs and UFBs were marginal. In both cases where the test plates were made of PVC and SUS304, the cleaning rate was improved by FBs. The cleaning mechanism is thought to involve the coalescence of multiple MBs, resulting in the formation of larger diameter bubbles that adsorb or push the object to be cleaned toward downstream side due to hydrophobic interaction or electrical interaction. The results of the bubble diameter measurement showed that the number of bubbles increased and the distribution of bubble diameters changed in water with MBs and UFBs compared to water with MBs. We concluded that these changes allow bubbles to penetrate the gaps between the object to be cleaned and the test plate, facilitating cleaning.

In our previous studies, we carried out air-water counter-current flow experiments under flooding conditions in vertical pipes having a diameter of D = 40 mm with combinations of sharp-edged or rounded top and bottom ends, and we measured counter-current flow limitation (CCFL), pressure gradient dP/dz, and void fraction α_G. We obtained the wall and interfacial friction factors f_w and f_i, and proposed correlations for f_w and f_i. In the present study, we carried out similar experiments in vertical pipes of D = 60 mm with rounded top and sharp-edged or rounded bottom ends (R/S or R/R) to evaluate effects of diameters on flow characteristics. For the smooth film (SF) due to flooding at the top end in the region of low superficial gas velocity J_G, the |dP/dz| value was very small and the wall friction term was large. The liquid film thickness δ_f could be expressed by the previously proposed correlation. For the rough film (RF) due to flooding at the bottom end in the region of high J_G, no significant difference was observed for f_w and f_i between D = 40 and 60 mm. We confirmed that CCFL characteristics at the lower end (CCFL-L) with R/S could be expressed by the Kutateladze parameters in the range of D = 40-60 mm and the characteristics were those for large diameters in the region of D ≥ 40 mm.