For recycle of cathode materials (LiCoO2) contained in spent lithium ion batteries, hydrothermal leaching with organic acids(citric acid and oxalic acid) was investigated. Hydrothermal leaching of LiCoO2 with 0.4 M citric acid at 423 K for 30 min of treatment time by convective heating was compared with that by microwave-assisted heating. Both Li and Co leaching yields were higher with the microwave heating than yields with convective heating. Hydrothermal leaching of LiCoO2 with oxalic acid additives was also studied. In this case, the yield of the solid residue that was probably Co-oxalate was promoted by the microwave heating. Diffusion of Li and Co at the surface boundary layer at the unreacted LiCoO2 core is possibly the controlling step of the leaching process. Microwave affects not only heating rate, but also diffusion of ions-water clusters and thus probably enhanced the leaching efficiency for citric acid and the solid residue formation for oxalic acid. The effect of treatment temperature, treatment time and concentration of citric acid on the hydrothermal leaching of LiCoO2 citric acid was evaluated. Almost 100 % of leaching yield of Li and Co was achieved over 423 K with 0.4 M citric acid. Hydrothermal leaching with 0.4 M oxalate acid at 423 K allowed Li ion to be completely leached but gave Co ion and oxalate anion complex that was insoluble in water.
In this study, TiO2–VO2 solid solutions were heated by microwaves and by an electric-furnace to investigate the spinodal decomposition behavior of a TiO2–VO2 system. Single-mode and multi-mode type microwave irradiation devices were used to investigate the spinodal decomposition of TiO2–VO2 . In the conventional process, spinodal decomposition required 12 h of annealing. However, in the microwave process, spinodal decomposition proceeded at a low temperature for 30 min. Additionally,the metal–insulator transition temperature (TMI ) of the prepared sample was lower than that of pristine VO2. This indicated the existence of an isotropic pressure on the boundary between the Ti-rich phase and the V-rich phase. Furthermore, the microwave-irradiated samples exhibited broadened double endothermic peaks in the DSC profiles. The broad peaks indicated that the samples exhibit several values of T MI , implying variations in the composition of the V-rich phase. The phase variation resulted from the selective heating of the V-rich layer that induced one-directional material diffusion from the V-rich phase to the Ti-rich phase.
There are a lot of epidemiology studies focused on the effects of microwave in life phenomena; however, there are few studies about effects on biomolecular behaviors by microwave irradiation. We constructed microwave irradiation systems for detailed analyses of biomolecular behaviors in this study. We developed a one-direction linear-polarized microwave irradiator with alinear polarization antenna, and a two-direction linear-polarized microwave irradiator with two linear polarization antennas.Finally, a study about influence of microwave in biomineralization, an example of the effects on biomolecular behaviors in life phenomena, was conducted with a precipitating peptide using the developed microwave irradiation systems. Throughout this study, the linear-polarized microwave irradiation systems would be one of the most powerful tools for studies about life and biological phenomena as well as biomolecular behaviors.