Hee-Lack Choi

Effect of ultrasonic treatment on ripening of titanium oxalate salt from solution

Titanium oxalate was precipitated by the addition of TiO(NO3)2 solution to an ethanol solution of oxalic acid and then ripened in the mother solution with/without ultrasound at various temperatures. The influence of various factors such as reaction temperature and ripening time, as well as the effect of ultrasonic treatment in the solution, was investigated. During the ripening reaction of the titanium oxalate, a new crystalline phase was found. The chemical formula and the crystal system of the new phase were as follows: (1) Chemical formula—Ti2O2(C2O4)(OH)2H2O, (2) Crystal system—orthorhombic with lattice constants of a = 1.0503 nm, b = 1.5509 nm, and c = 0.9700 nm. The treatment of ultrasound during the ripening reaction accelerated the dissolution rate of the initial precipitated particles, so that the formation of the crystalline phase was hastened.

Effect of Zn/NaCl ratios on the charge/discharge performance in Na-ZnCl 2 battery

battery, which operates as the same mechanism of battery using solid-electrolyte, is able to reduce its material cost by 40 % comparing to the battery. It has been known that the battery produces as an intermediate phase during charge/discharge process. Therefore, the redox process is divided into four steps having the voltage range of 1.92~2.13 V. However, effects of the critical factors such as the composition of cathode materials, depth of charge and discharge, and additives have not been reported yet. We examined the effect of the Zn/NaCl ratios and revealed that its optimum ratio was in the range of 1.3~1.7.

Effects of cracker cell temperature and V/III ratio on GaInP grown by chemical beam epitaxy using TIPGa, EDMIn and TBP

This paper reports a systematic study of the effects of the cracker cell temperature and the input V/III ratio on the growth of GaInP. GaInP epilayers were grown on GaAs (001) substrates using triisopropylgallium, ethyldimethylindium and tertiarybutylphosphine by chemical beam epitaxy. The surface morphology, growth rate, low temperature (15 K) and room temperature (300 K) photoluminescence (PL) were studied as a function of the cracker cell temperature and input V/III ratio. At an optimum cracker cell temperature and input V/III ratio, the PL spectrum showed only a strong band edge peak with a full width at half maximum of 10.8 meV.

Changes of discharge voltage of plate-type sodium sulfur batteries in the early charge/discharge cycles

The sodium-sulfur batteries which operate at have been mainly used in the field of energy storage system. This batteries consist of liquid sodium anode, sulfur cathode and -alumina solid electrolyte. The conditioning process for stabilization of the batteries is essential since the cells show considerable fluctuation of discharge voltage at the beginning of discharge/charge cycles. It is found that one of the reasons of the fluctuation is the gradual change of contact area between molten sodium and solid electrolyte.