Physical properties and photocatalytic activity of TiO2 thin films coated on various glass substrates were investigated in order to elucidate factors affecting the photocatalytic activity and the role of Na+ ions diffusing from glass substrates. The most predominant factor was found to be crystal size of the TiO2 thin film. The Na+ ions affected the photocatalytic activity by changing the formation temperature of anatase as well as the crystallite size of TiO2 thin film. Na+ appears not to work as a recombination center of electrons and holes contrary to the conventionally accepted mechanism.
The complex plane plots of the electrochemical impedance of the oxygen reduction electrode show various loci depending on the reaction passway. The theoretical expression of Faradaic impedance for oxygen reduction electrode was derived, and the curve-fitling methods of the impedance spectra were proposed. Firstly the curve-fitling with the experimental results was performed by using commercial fitting software, and some parameters, such as the charge transfer resistance and the electric double layer capacitance, were obtained. Furthermore, the reaction rate constants were determined by carrying out the curve-fitling of spreadsheet with the theoretical expression of Faradaic impedance. In addition, the depressed inductive semicircle could be fitted precisely assuming that reaction rate constant depends on frequency of imposed potential modulation.
The spinel LiMn2-xNixO4 (x = 0~0.5) in which a part of Mn was substituted by Ni were prepared, and the Mn valence was determined by chemical analysis. Mn valence increased with increasing Ni content, x. The heats of dissolution of the samples were measured by the solution calorimetry method. The standard enthalpy of formation, ΔfH0, and the enthalpy change of reaction, ΔH, were calculated from the heat of dissolution. Thermodynamic stability was examined by ΔH. From the relation between the cathode performance and the thermodynamic stability of LiMn2-xNixO4 (x = 0~0.5), a more thermodynamically stable sample was found to lead to a good cycle performance.
We investigated the physical property, crystal structure and electrode performance of LiMn1.5Ni0.5O4 as a 5 V class cathode active material, which was prepared by changing the calcined temperature with the sol-gel method. Cycle performance is different from the calcined temperature. LiMn1.5Ni0.5O4, which calcined at 700°C, showed a good cycle performance with the maximum discharge capacity of 125.3 mAh/g, and the capacity after 100 cycles was 95.1% of the maximum capacity. The crystal structure was determined by Rietveld analysis using powder neutron diffraction. From a result, LiMn1.5Ni0.5O4, which calcined at 650°C, composed of mixing two space group P4332 phases. It is suggested that the oxidation states of Ni change in the sample, as these phases are different from each lattice parameter. Ni valence of sub-phase for LiMn1.5Ni0.5O4 calcined at 650°C, which was calculated from Bond Valence Sum, increase. Moreover, we investigated, the distortion and the stability of crystal structure by the bond length and the Madelung energy, nuclear and electron densities by MEM method with neutron diffraction and X-ray diffraction.
In current Cu/low-k damascene processing, post-CMP cleaning poses much more difficulty than in early processes, due to variation in the kinds of slurry and cleaning solutions developed for low-k materials. Though reports have addressed the performance of a number of cleaning chemicals, the mechanism of post-CMP cleaning is not well understood. Therefore, we performed FT-IR measurements, AFM observations, and electrochemical analyses of certain kinds of slurry and chemicals and investigated the mechanisms of Cu CMP and post-cleaning. In the case of cleaning chemicals that showed good performance, FT-IR and AFM measurements indicated that the surface of Cu was clean, and CV (Cyclic Voltammetry) measurement showed that these cleaning chemicals easily reacted with Cu. These findings suggest that slurry components are removed by the cleaning solutions. However, we also found that the effectiveness of cleaning chemicals was sometimes impaired by components of the slurry. In a combination of chemical and slurry that resulted in poor performance, much more residues were observed to remain on the Cu surface. This phenomenon can be explained by the competitive reaction between the slurry and the chemical. In short, the cleaning chemical reaction is impeded by certain elements in the slurry.
A channel flow double electrode (CFDE) was fabricated in order to investigate oxygen reductions with powder type of perovskite oxides. The clay electrode, which consisted of the perovskite oxide powder, carbon powder and binder, was used as the working electrode. From the measurement of the electrochemical impedance, the resistance of the clay electrode was confirmed to be small enough to use in the electrochemical measurements. The collecting electrode current was measured and plotted against the working electrode potential, and the amount of evolved hydrogen peroxide was determined. Moreover, the average number of charge transfer was calculated from the working and collecting electrode currents. The values of were approximately 4 for LaMnO3.15, 3 - 4 for LaMnO3, and 2.5 - 4 for LaFeO3. In the course of the above-mentioned experiment, the ability of the CFDE for the study of oxygen reduction catalytic activity of powder oxide has been confirmed.