Thermodynamic calculation of phase equilibria of the Bi-Sn-Zn system

A thermodynamic assessment of the Bi-Sn-Zn ternary system was carried out by considering the experimental data including the phase equilibria and thermodynamic properties on the basis of the CALPHAD method. A set of optimized thermodynamic parameters has been obtained, which leads to a very good fit between calculation and experiments. In particular, the thermodynamic calculations in the Sn-rich portion are presented in view of the recent progress in Pb-free solder alloys.     

Environmental stress cracking of poly(acrylonitrile-butadiene-styrene)

The environmental stress cracking (ESC) of acrylonitrile-butadiene-styrene (ABS) copolymer caused by a non-ionic surfactant (poly-oxyethylene alkylether) was studied by constant-load tensile creep tests and edge crack tension (ECT) tests. The fracture surfaces were investigated by a scanning electron microscope (SEM) and the morphology of the crack tip was investigated by a transmission electron microscope (TEM). It was found that the results of the creep tests performed in the non-ionic surfactant were very different from those performed in air. SEM images of the fracture surfaces showed that there were three different mechanisms of fracture and that specimens had a tendency to rupture by ESC when the stress was small. The results of the ECT tests and the TEM images showed that the change in the mechanism of the fracture was attributable to the change of morphology at the crack tip.     

Corrosion resistance of structural materials in high-temperature aqueous sulfuric acids in thermochemical water-splitting iodine–sulfur process

Very harsh environments exist in the iodine–sulfur process for hydrogen production. Structural materials for sulfuric acid vaporizers and concentrators are exposed to high-temperature corrosive environments. Immersion tests were carried out to evaluate the corrosion resistance of ceramics and to evaluate corrosion-resistant metals exposed to environments of aqueous sulfuric acids at temperatures of 320, 380, and 460 °C, and pressure of 2 MPa. The aqueous sulfuric acid concentrations for the temperatures were 75, 85, and 95 wt%, respectively. Ceramic specimens of silicon carbides (SiC), silicon-impregnated silicon carbides (Si–SiC), and silicon nitrides (Si₃N₄) showed excellent corrosion resistance from weight loss measurements after exposure to 75, 85, and 95 wt% sulfuric acid. High-silicon irons with silicon content of 20 wt% showed a fair measure of corrosion resistance. However, evidence of crack formation was detected via microscopy. Silicon enriched steels severely suffered from uniform corrosion with a corrosion rate in 95 wt% sulfuric acid of approximately 1 g m⁻² h⁻¹. Among the tested materials, the ceramics SiC, Si–SiC, and Si₃N₄ were found to be suitable candidates for structural materials in direct contact with the considered environments.     

Thermodynamic assessment of the Aluminum-Manganese (Al-Mn) binary phase diagram

A thermodynamic calculation of the Al-Mn binary system that takes into account recent experimental results and includes five intermetallic compounds and all the solid-solution phases is presented. The Gibbs energy of the body-centered cubic (bcc) phase has been described on the basis of the two-sublattice model that includes the second-order A2/B2 ordering reaction as well. A consistent set of optimized thermodynamic parameters has been arrived at for describing the Gibbs energy of each phase in this system leading to a better fit between calculation and experiments.     

Use of multivariate analysis for the improvement in prediction accuracy of bacterial aerobic plate count by flow cytometry

Flow cytometry (FCM) and aerobic plate count (APC) by the culture method were performed on green tea samples spiked with Escherichia coli type strain NCTC9001 (ATCC11775) solutions of different concentrations. In FCM, fluorescence signals from multiple stained bacteria and other fluorophores are detected using detector channels, and recorded as events with a voltage at each channel. FCM data were analyzed in two ways: conventional and multivariate analysis. In the former, the number of events with voltages larger than the defined threshold values was regarded as the predicted APC. In the latter, voltage histograms of all channels were obtained and merged horizontally to serve as explanatory variables. Then a partial least squares regression (PLSR) model was built to predict APC from the histogram data. The coefficient of determination (R²) and the root mean square error (RMSE) between APC by the culture method and that predicted by conventional FCM were 0.916 and 1.08 cfu/ml². The APC values predicted by the PLSR model and those measured were in good agreement with R² of 0.982 and RMSE of 0.417 cfu/ml, which verified the potential of the proposed method for improving APC prediction accuracy by FCM.     

Phase equilibria in the Co-Ti portion of the Co-Al-Ti ternary system

Phase equilibria of 900, 1000, and 1100 °C in the Co-Ti portion of the Co-Al-Ti system were mainly determined by energy dispersion x-ray spectroscopy. On the Ti-Al side, the β-Ti (A2) phase region is extended by the addition of Co and the β-Ti + AlTi₃ (D0₁₉) two-phase region appears in the ternary equilibrium, while the AlTi (L1₀), AlTi₃, and β-Ti phases show very low solubility of Co. It was found that the two ternary intermetallic compounds, Co₂AlTi (L2₁) and CoAl₂Ti (D8 _a ), exist over a wide solubility range along the CoAl(B2)-CoTi (B2) and CoAl₃-CoTi₃ sections, respectively. The ordering transition and the phase separation due to ordering of the β-Ti, CoAl, or CoTi and Co₂AlTi phases fundamentally possessing the bcc structure are also discussed.     

Experimental studies of optical Raman amplifiers for 1.3‐µm wavelength band and its application to 20 Gbit/s × 2 WDM transmission

Configurations of a Raman amplifier suitable for a 1.3‐µm wavelength band are discussed and their properties are experimentally investigated. Pump light with a wavelength of 1.23 µm that is necessary for the Raman amplification in the 1.3‐µm wavelength band is obtained using a 1.06‐µm fiber laser and Raman laser technique. Concerning the Raman laser, wavelength conversion from 1.06 µm to 1.23 µm is effectively achieved using a cavity configuration including fiber Bragg gratings and a dispersion‐shifted fiber. On the other hand, a conventional dispersion compensation fiber which has an essential property of high nonlinearity is applied in order to obtain large gain at 1.3 µm. Net gain of 35 dB and output power of 15 dBm are achieved. To confirm the applicability of the Raman amplifiers to high‐speed optical transmissions, experiments of 20 Gbit/s × 2 WDM repeaterless transmission through a 80‐km conventional single‐mode fiber are carried out. The 1.3‐µm signal should be degraded due to the dispersion caused by the dispersion compensation fiber in the Raman amplifier; However, bit error rate of less than 10 to 12 is obtained at both wavelengths, which is sufficient performance for practical uses. © 2003 Wiley Periodicals, Inc. Electr Eng Jpn, 143(1): 58–65, 2003; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.10137     

Application of conventional activated carbon loaded with dispersed Pt to PEFC catalyst layer

Improvement of the polymer electrolyte fuel cell (PEFC) requires development of highly active electrodes of low cost to facilitate its widespread use. In the present study, the possibility of applying conventional activated carbon particles loaded with Pt to the electrode catalyst layer was tested because the particles were promising in dispersion of Pt and preparation cost. The catalyst layer was formed from the particles and Nafion® and was supported as a thin film on a rotating glassy carbon disk electrode (GC RDE). Activity for oxygen reduction was evaluated by the hydrodynamic voltammetry in perchloric acid to give a current free of the influence of mass transfer in the solution. Compared with a conventional catalyst layer formed from carbon black loaded with Pt, the new catalyst layer exhibited a significant, approximately 6-fold increase in current in the high potential region corresponding to a 100 mV increase in electrode potential. Activity, however, was retarded in the low potential region. This disadvantage was overcome by mixing a conductive agent into the layer and covering it with another layer containing carbon black loaded with Pt. This double catalyst layer exhibited increased activity across all potential regions, indicating the availability of the activated carbon in the electrodes.