The physicochemical and electrochemical characteristics of Mg-based hydrogen storage alloys modified by various methods are discussed for intended use in nickel-metal hydride batteries. A Mg2Ni-Ni composite prepared by ball-milling of Mg2Ni alloy with Ni (Mg2Ni/Ni=1/1.28 in mole ratio) has a homogeneous amorphous structure and exhibits much improved hydriding-dehydriding characteristics and a very high discharge capacity at room temperature. Surface modification of amorphous MgNi alloys by ball-milling with graphite led to an improvement in the hydriding-dehydriding and charge-discharge characteristics. It is suggested that both a charge-transfer reaction between graphite and Mg and an increase in the Ni/Mg ratio on the alloy surface may be responsible for the enhanced characteristics of the MgNi-graphite composite. By using carbon materials with lower crystallinity for the surface modification, the ball-milling time to reach a maximum discharge capacity was shortened. Moreover, it was found that the combination of partial substitution with Ti and V and the subsequent surface modification with graphite promoted hydrogen desorbability and improved charge-discharge cycle performance and high rate dischargeability. The combination of bulk and surface modifications is very effective in improving the physicochemical and electrochemical characteristics of Mg-based alloys.
Manganese dioxides were prepared by ozone oxidation in no-acidified manganese nitrate solution at 10 ℃ for 3 h. The formation of γ-MnO2 phase was confirmed by X-ray diffraction. The particle size and specific surface area of the product were 0.3μm and 187 m2 g－1, respectively. After heating at 375 ℃ for 5h in air, the formation of β-MnO2 phase was observed. When the product was used as the cathode material of lithium/manganese oxide cell, the discharge capacity of this cell was 288 mAh g－1. It was found that the product obtained by this process is hopeful to be used as a cathode material.
Acrylic acid 2-(2-acryloyloxy-ethyldisulfanyl)-ethyl ester (AAEE) was synthesized and cross-linked to the corresponding polymer as a new cathode material of lithium secondary battery. The electrochemical properties of two types of electrode using the polymerized AAEE were investigated. One of the cells was made of the AAEE electrode containing gel-type electrolyte according to the conventional method, and the electrode was simply made by binding AAEE and carbon black. This cell showed high discharge capacity about 380 mAh/g. The other cell was made of the AAEE composite type electrode containing solid polymer electrolyte. The newly devised electrode was made by the stepwise procedure, after the disulfide was first absorbed to carbon black surface, then PEO was added and polymerized prior to make the cell. This electrode was composite type and this cell showed excellent cycling performance. Even after more than 2000 charge-discharge cycles, no decrease of the performance was observed.
The purpose of this investigation was to form Sn-Cu solder bumps for flip-chip bonding from acid sulfate bath (2M H2SO4+0.2M SnSO4+0.008 M CuSO4) containing N,N-bis(polyoxyethylene)octadecylamine (POOA-10) using electroplating method. Compact and relatively smooth Sn-Cu alloy electrodeposits were obtained from acid sulfate baths containing POOA-10. Cu contents in electrodeposits were approximately constant in the range of current densities from 1.0 to 7.0 A/dm2. The solidus temperature of Sn-Cu alloy electrodeposits was 227℃. Sn-Cu alloy bumps of straightwall and mushroom types with homogeneous composition were obtained from acid sulfate baths containing POOA-10 under galvanostatic condition.
The role of a catalyst during the synthesis of a binder, which could harden a silica slurry, was investigated. Tetramethoxysi1ane oligomer was efficiently hydrolyzed and poly-condensed to the binder when tetramethylammonium hydroxide and tetraethylammonium hydroxide, which are both organic bases having bulky groups, were used as catalysts. On the other hand, nitric acid, sodium hydroxide, potassium hydroxide and ammonia were not effective catalysts for binder synthesis. The difference in the role between these catalysts was explained as follows. The bulky organic groups were assumed to have a steric hindrance interaction with methyl groups in tetramethoxysilane oligomer and this steric interaction could successfully produce the binder.