Kiyotaka Komori

Electrical conductivity and chemical durability in alkali-silicate oxynitride glasses

The effects of incorporation of nitrogen on the electrical conductivity and the chemical durability in the R-Si-O-N oxynitride glasses (R=Li and Na) have been systematically investigated. The electrical conductivities of these oxynitride glasses are enhanced and the chemical durabilities to the acidic and alkaline aqueous solutions are drastically improved as the nitrogen content increases. The extent of the changes in the electrical conductivity and the activation energy for conduction due to the nitrogen incorporation are greater for the Li-Si-O-N oxynitride glasses than for the Na-Si-O-N system. The experimental results are discussed from the viewpoint of the increased covalency of the chemical bonding in the glass network by the formation of covalent Si-N bonding.

Development of glass fiber with high dielectric constant

Abstract Glass fibers with high dielectric constant have been developed to miniaturize printed circuit boards used at high frequencies. The dielectric constant of the glass is 11.6 at 1 GHz while that of E glass is 6.7. In the glass composition system, SiO 2 CaOSrOBaOTiO 2 ZrO 2 NbO 2.5 , it was found that the NbO 2.5 plays an important role in decreasing the liquidus temperature of the glass, resulting in successful fiber-drawing. Using the above glass composition system, glass fibers consisting of 200 filaments with an average diameter of 8 μm have been continuously drawn from a conventional platinum alloy bushing. This glass fiber was then woven into cloth. Laminates with a dielectric constant of 10.5 at 1 GHz have been made with glass cloth impregnated with the thermosetting polyphenylene oxide resin and titanium oxide powder, resulting in high uniformity in the dielectric constant.

Chemical durability of a superconducting oxide YBa2Cu3Ox in aqueous solutions of varying pH values

The chemical durability of a superconducting oxide YBa2Cu3Ox in the aqueous solution was investigated as a function of pH value by measuring the amount of leaching of the cations in the solution by inductively coupled plasma (ICP) analysis. The chemical durability of YBa2Cu3Ox was very low in highly acidic solutions of pH ca, 1, where the cations were dissolved in the same cation ratio as that of the compound. In an ion-exchanged water and NaOH solution, barium ions were leached out preferentially and almost no yttrium and copper ions were leached out. When NH4OH was used as a basic reagent, the amounts of barium ions leached out were higher than in the NaOH solution of the same pH value and the dissolution of copper ions was observed, unlike in the NaOH solution of the same pH value. These observations were explained in terms of the chemical stability of individual oxide components.