Selected Articles
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Investigation of Single Ammonia Droplet Evaporation Characteristics Under High Temperature and Pressure Conditions
Ammonia is a promising alternative fuel for significantly reducing CO₂ emissions. However, to utilize it efficiently, it is necessary to develop technologies that enable direct spray combustion of liquid ammonia. In this study, we clarified—for the first time in the world—the evaporation characteristics of ammonia droplets under high-temperature and high-pressure conditions. Furthermore, we obtained essential droplet evaporation data necessary for the development of ammonia spray combustion technology.
Leang So Khuong, Nozomu Hashimoto, Yu Ito, Nobuto Nakamichi, Yusuke Konno, and Osamu Fujita
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Recovery of phosphate from carbonized sewage sludge by chlorination
The present research group has recently found a method to recover phosphorus, which is called “biological and technical nutrient”, from sewage sludge as phosphorus chloride forms. Specifically, we have developed a simple sewage sludge recycling technology that first carbonizes sewage sludge to improve handling, then chlorinates the resulting carbonized material at 500℃, and finally separates phosphorus chloride species and impurities by a cooled deposition method. This method can be applied to sewage sludge incineration ash, livestock manure, steelmaking slag, etc.
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Selective separation of Li, Ni, Co and Mn from model spent Li ion battery cathode materials by dry processing using the combination of chlorination and oxidation
The present group has recently developed a technology to selectively recover valuable metals (Li, Ni, Co and Mn) from used lithium-ion battery cathode materials (LiNiO₂, LiCoO₂, LiMn₂O₄, and their composite composition). Specifically, we found that Li, Ni, Co and Mn can be selectively separated from LiNiO₂, LiCoO₂, and LiMn₂O₄ by chlorination up to 600℃ followed by air oxidation up to 1300℃. This research paper was selected as a Key Scientific Article by the selection committee of Advances in Engineering, Canada, and is highly evaluated.
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Pore properties and CO₂ adsorption performance of activated carbon prepared from various carbonaceous materials
The production of activated carbon using biomass and coal as carbon sources, melamine as a nitrogen source, and K₂CO₃ as a chemical activator revealed that the lower carbon content and lower ash content of the carbon source resulted in better pore development, and that the surface area and micropore volume of activated carbon affected the CO₂ adsorption capacity. It was also shown that the optimal micropore size for CO₂ adsorption is 0.5 to 1.2 nm. These results are expected to lead to the establishment of production guidelines for activated carbon with high CO₂ adsorption capacity.
Yuuki Mochizuki, Javzandolgor Bud, Enkhsaruul Byambajav, and Naoto Tsubouchi
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Imaging valley-vortex edge modes in a phononic crystal at ultrahigh frequencies
We perform optical measurements and numerical simulations of guided phonon propagation in novel topological phononic crystal structures at ultrahigh frequencies. The structures support valley-polarized states that exhibit an energy vortex nature and propagate with high efficiency at domain boundaries because backscattering is suppressed due to conservation of time reversal symmetry. We extract frequency- and time-resolved spatial mode patterns and -space images, together with dispersion relations. We investigate the conditions required for robust propagation along interfaces and thereby observe very high efficiency waveguiding.
Paul H. Otsuka, Motonobu Tomoda, Daiki Hatanaka, Hiroshi Yamaguchi, Kenji Tsuruta, and Osamu Matsuda