Maruo Kamino

Advanced Structures in Electrodeposited Tin Base Negative Electrodes for Lithium Secondary Batteries

Tin anodes deposited electrochemically on a copper foil current collector are studied to develop a next-generation lithium-ion battery with higher energy density. Better cycle performance through ten initial cycles under full charge and discharge conditions was attained by annealing tin electrodeposited on a rough surface copper foil. The annealing process was found to change the main active material from Sn to Cu 6 Sn 5 with some minor compounds. Furthermore, a microcolumnar structure of the active material portion was found to he self-organized in accordance with the surface profile of the foil during the first charge-discharge cycle. Advantages of these structural features are discussed in terms of the initial charge and discharge performance. including specific capacity and coulombic efficiency measured by using a three-electrode cell.

Study on Sn–Co Alloy Anodes for Lithium Secondary Batteries I. Amorphous System

An amorphous Sn-Co alloy film electro-codeposited on rough Cu foil was found in our previous works to self-organize a microisland structure, which is a crucial factor to improve Sn alloy anodes for cyclability. This work focused on the electrochemical properties, film morphology, and phase structure, and the behavior of Co atoms was analyzed by extended X-ray absorption fine structure and magnetic susceptibility measurements. Cycle performance up to 20 cycles, in which the capacity anomalously fluctuated, is discussed based on these results, where the capacity change is explained by the morphological and phase structural changes. The stabilization process of the phase is clarified in connection with formation of ferromagnetic face-centered cubic Co particles.

A New-Structure IR Gas Sensor

We developed a new-structure IR gas sensor using a new type of pyroelectric IR detector with a solid-state chopper and an optical filter in the same package. This gas sensor enables high accuracy and high reliability due to the new structure (DEA Structure) and the new IR detector. The accuracy of the measurement is ±0.5% in the range of a 0~20% concentration of CO2 gas. The change of the output signal is within ±0.8% for 1500 hours. The characteristics (especially long-term operation) are superior to those of the conventional NDIR-type gas sensor.

Epitaxial growth of Ba1-xKxBiO3 thin films by high-pressure reactive RF-magnetron sputtering

Epitaxial growth of Ba1-XKXBiO3 (110) thin films has been carried out on SrTiO3 (110) substrates using reactive rf-magnetron sputtering for the first time under a 80 Pa discharge gas which is of a rather higher pressure than is usual. Electrical measurements showed that Tc of as-grown films was 16 K. A preferred orientation of (110) and epitaxial growth of the Ba-K-Bi-O film on the substrates were confirmed by XRD (X-ray diffraction) and RHEED (reflection high-energy electron diffraction), respectively.

Properties of Yb–Ba–Cu–O Superconductors Prepared by a Plasma-Arc Melting and Rapid Quenching Method

A PMQ (plasma-arc melting and rapid quenching) method has been successfully developed to obtain homogeneous and highly dense Yb-Ba-Cu-O compounds through the crystallization of the superconducting phase from the amorphouslike state. The maximum Tc of 91 K and packing density of 7.14 g/cm3 (98% of the theoretical density 7.27 g/cm3) were produced by this method. Furthermore, a large activation energy of 1.5 eV was observed by magnetic relaxation measurements.

Modulation Type Pyroelectric IR Detector

We have developed a new type of pyroelectric IR detector which contains a sensing part and a solid state chopper with two bimorph vibrators and two slit plates in the same package. This new detector (M-type IR detector) features high reliability, small volume and low electric power consumption compared with conventional pyroelectric IR detectors using a rotating chopper. The output voltage and noise voltage of the M-type IR detector have been investigated theoretically and experimentally. It was confirmed that a good performance can be achieved in the M-type IR detector by optimizing the relative position of the two slit plates and the aperture diameter of the shield box.

Enhanced mode detection for microwaves using a high-impedance YBCO-BiO composite superconductor

Abstract We have developed a Josephson type microwave detector using a YBCO-BiO composite superconductor which uses the non-linear effect produced by a complex network of Josephson weak links at the grain boundary (enhanced mode detection). This composite superconductor was prepared by doping YBa2Cu3Ox with Bi2O3, which causes high normal state resistance in the composite and enhances the Josephson effect at the grain boundary. It was found that the measured responsivity (RMV) improved by increasing the normal resistance (Rn) of the detector through enhanced matching of the incident microwaves and the detector. An RMV of 180 V/W and NEP of 1.4×10−14 W/Hz 1 2 were obtained with a detector having an Rn of 13 Ω. These results suggest the feasibility of a practical detector having an RMV of more than 104 V/W which operates at 60 K by the enhanced mode detection of a high-TC superconductor.

Preparation and characteristics of Ba1-xKx BiO3 superconductors using the plasma-arc melting and rapid quenching method

Abstract High-density, homogeneous Ba1-x K x BiO3 superconductors with relative density of 97% were successfully synthesized by the plasma-arc melting and rapid-quenching (PMQ) method. X-ray powder diffraction data showed a single Ba0.6K0.4BiO x structure with a lattice constant of a = 4.283 a. A sharp superconducting transition was observed at 28.5 K, with a transition width of less than 0.5 K.

Preparation and Characterization of a Superconductor-Semiconductor Junction: Ba1-xKxBiO3/Nb-Doped SrTiO3

Electrical properties of Au/native-barrier/BKBO tunnel junction and BKBO/SrTiO3:Nb(0.1wt%) heterojunction were studied. The differential conductance dI/dV spectrum of the Au/native-barrier/BKBO tunnel junction had a clear gap structure and was very close to the ideal BCS form with Δ(0)=3.2 meV. BKBO/SrTiO3:Nb heterojunction fabricated at 350°C showed tunneling-like I-V characteristics. In the dI/dV spectrum of the high-Tc superconductor/semiconductor junction, we observed a superconducting gap structure for the first time.

Epitaxial growth of Ba1−xKxBiO3 thin films by rf-magnetron sputtering

Abstract As-grown Ba 1−x K x BiO 3 (BKBO) epitaxial thin films with a critical temperature of 16.3 K have been successfully prepared at 300°C on SrTiO 3 (110) substrates by a high-pressure rf-magnetron sputtering. A preferred orientation of (110) and epitaxial growth of the BKBO film on the substrates were confirmed by X-ray diffraction (XRD) and reflection high-energy electron diffraction (RHEED), respectively.