Chiaki Sakamoto

Corrosion of Inconel 600 alloy in high concentrated NaOH solution.

Corrosion of Inconel 600 (I-600) in concentrated NaOH (1-20M) solutions was studied under various temperatures (50-140°C) and potentials. The solution treated (1050°C, 15min) and sensitized (650°C 10hrs) specimens were used. The results are as follows:(1) The polarization curves for the both specimens showed no change in electrochemical behavior in various corrosive environmental conditions at 50°C. However, the both specimens showed three peaks at higher temperatures than 50°C. The solution treated specimen showed a slightly low current density in the primary passive region and a slightly high current density in the secondary anodic peak, compared with those of the sensitized specimen.(2) The films formed on the specimen surface during corrosion tests in 20M NaOH solution at 140°C were made of NiO, Cr2O3 and Fe3O4.(3) The tests of crevice corrosion of I-600 and carbon steel (S15C) showed that general corrosion took place on the solution treated specimen, but the intergranular corrosion under the oxide films took place and it propagated to the crevice in the sensitized specimen.

Crystal growth of α-quartz from a silica gel using alkali halide flux

Crystals of α-quartz were obtained from a silica gel in alkali halides. We found that the addition of LiCl to NaBr provides the most suitable flux. The gel was heated to 850°C, and cooled slowly near the transition temperature. By this treatment β-quartz was converted to α-quartz. The following results were obtained.(1) The NaBr-LiCl system provides the best flux for the crystallization of α-quartz. The best flux molar ratio R1 (=NaBr/LiCl) for obtaining α-quartz was 9.7/0.3.(2) The crystal size decreased with decreasing ratio R2 (=silica gel/flux, molar ratio) from 0.1 to 0.01, and reached a maximum (0.5×0.5×1.2mm).(3) When 1wt%-CaCO3 was added to the flux under conditions (1) and (2), an α-quartz crystal with a maximum size of 0.5×0.5×2.5mm were obtained.

The Crystal Growth of Diopside Using NaCl

ディオプサイド (CaMgSi2O6) のアルカリハライドフラックスによる結晶成長を試み, 結晶原料としてドロマイト原石及びα-石英が, フラックスとしてNaClが最適であることを見いだした. 次にR1=α-石英/ドロマイト (モル比), R2=出発原料/NaCl (重量比), 保持温度及び保持時間を変化させて, 生成した結晶の種類, 形態及び最大結晶長について検討を行った. 保持温度1100℃, 保持時間12h及びR2=0.02の条件において, 次の結果を得た.(1) 0.25≦R1≦1.00ではモンチセライト (CaO・MgO・SiO2), 0.75≦R1≦1.75ではオケルマナイト (2CaO・MgO・2SiO2), 1.25≦R1≦3.00ではディオプサイドが生成した.(2) 上記3種類の結晶のうち比較的結晶成長の良好であったディオプサイドについては, R1=2.00で最大結晶が生成した. その結晶長及び形態は, 2.0×1.5×0.5mmの板状晶, 1.0×1.0×0.8mmの多面体状晶及びφ0.3×4.0mmの針状晶であった.