Various types of cathode materials for lithium secondary battery were synthesized by spray pyrolysis in which mists generated with two-fluid nozzle or ultrasonic atomizer were thermally decomposed at an elevated temperature. The cathode materials had a spherical morphology with a narrow particle size distribution and uniform chemical composition. The cathode materials obtained by spray pyrolysis exhibited an excellent rechargeable capacity and a cycle stability. Pulse combustion spray pyrolysis formed oxide anode materials with the particles size less than 50 nm and exhibited a good rechargeable performance at a higher rate. Mass production of cathode materials was carried out by using flame-type spray pyrolysis. It was demonstrated that the cathode materials were continuously produced and that the rechargeable capacity and cycle performance of cathode materials were comparable with that obtained by spray pyrolysis. The flame-type spray pyrolysis had a high energy-saving for mass production of cathode materials. Therefore the spray pyrolysis process is effective for the synthesis of cathode and oxide anode materials.
When an aerosol, comprised of a carrier gas and powder particles of metal, alloy, or oxide, is sprayed at a high speed onto a substrate, a compacted powder is deposited to form a thick film on the substrate. The authors have applied for the first time this aerosol process to the preparation of rechargeable battery electrodes, and have revealed that the process has unique advantages as anode materials with high capacities. In this review, we introduce highlights of our successful results obtained by the material development of Li-ion battery anodes, and mention a future outlook for the development of the next-generation battery from the viewpoint of the potential of the aerosol process.
Spray pyrolysis is a typical liquid-to-particle conversion processing, and can form complex and highly crystalline oxides due to nucleation in liquid phase and pyrolysis in gas phase at a high temperature. And, this method can control the fine structure in/on the particles with an additive into the source solution. By the spray pyrolysis with citric acid as the additive, aqueous droplets of metal nitrates can convert to porous oxide particles. The electrode, cathode and anode, of solid oxide fuel cell (SOFC) needs porous structure for larger reaction area and higher gas diffusivity. The synthesis of the particle materials of the SOFC electrodes by the spray pyrolysis method with citric acid and the electrochemical evaluation for SOFC are reviewed.
Fabrication of porous ceramic thin films with unique microstructures was carried out by using an electrostatic spray deposition (ESD) process, which is one of the effective thin film preparation techniques through aerosol processes. The deposition process parameters, such as the substrate temperature, the distance between substrate and tip of nozzle and the solvent compositions were changed systematically to examine their effects on film morphology. As a result, it was demonstrated that this technique was useful for the production of electrode films for lithium-ion batteries and electrode and electrolyte films for solid oxide fuel cell (SOFC).
Wafer surface scanners (WSS) are evaluated using a calibration wafer which has size standard polystyrene latex spheres (PSLS) on its surface. Aerosolized PSLS are deposited onto a wafer surface to make the calibration wafer, and the methods for making the wafer are standardized. This study introduces a new procedure for making a calibration wafer whose number of deposited particles and a method for evaluating the uncertainty of the particle number on the wafer are known. The important parameter in the procedure is called the particle number conversion coefficient, γw|p, which is the coefficient for calculating the number of particles deposited on a wafer, Nw, from the number of aerosol particles introduced to a wafer, Np, by Nw= γw|p・Np. To accurately evaluate the value of γw|p the PSLS are deposited inside a circular area whose diameter is a few hundred micrometer. Then, the value of Nw was obtained by visually counting all the deposited PSLS using a scanning electron microscope, and the value was compared to a known value of Np. In order to deposit the PSLS within a narrow area on a wafer the PSLS were first grown to micrometer-sized droplets by condensation, and these droplets were deposited onto a wafer by inertial impaction. In this study the value of γw|p was evaluated using 0.81 μm PSLS, and the relative expanded uncertainty of the predicted particle number on a wafer was ±9.6%. The particle number standard wafers were made by depositing PSLS uniformly over a wafer using a XY stage. Then, the wafers were used to evaluate the counting efficiency of a WSS.
In order to clarify the mechanism to induce biologically hazardous phenomena in the environment by the reaction of the Secondary Organic Aerosol (SOA) and to identify reactive species in SOA atmosphere (particles and gaseous constituents are coexisting), experiments of capturing reactive species in the gas chamber where SOAs were generated via the reaction of ambient air containing α-pinene with ozone have been carried out by taking advantage of radical scavenging reagents. The obtained adducts in SOA atmosphere were analyzed by ESR (Electron Spin Resonance) and LC/MS (Liquid Chromatography/Mass Spectrometry). ESR signal intensities of the radical scavenging samples exposed by SOA atmosphere were smaller than those of the control sample due to the formation of diamagnetic adducts. And new peculiar peaks (α-pinene radical adducts produced by the trapping reactions with radical scavenging reagents) were detected by LC/MS. Thus, it is plausible that reactive species in ambient air can be identified surely from analytical approach of the adducts formed with radical scavenging reagents.
An irregular method is attempted to analyze the source contribution of metallic components and elemental carbon in PM2.5 among “long-range-transport pollutants”, “Asian Dust”, and “locally-emitted pollutants” categories when applying Chemical Mass Balance (CMB) method. In this analysis, source profiles required to run CMB is not supplied from outside, but selected from the long-term dataset of PM2.5 composition measured at Fukuoka (Dazaifu), Japan, during the period of March 2010 through March, 2012. Typical days when PM2.5 aerosol from each source category appears to be dominant are selected in view of areal PM2.5 behavior, light extinction coefficient of non-spherical particles from Lidar data, and NO/NOx concentrations. The CMB analysis applied to two case study periods produced qualitatively consistent result with other indirect measures. The arrival timing of the two long-range transport events in early February, 2011, which was reported in a prior research, was successfully calculated by the CMB source estimation. During a prominent Asian dust event in early May, 2011, the temporal change in the estimated source fraction of air pollutants and Asian Dust agreed qualitatively with that of the fraction of spherical and non-spherical light extinction coefficients of aerosols analyzed from Lidar data.