Yukio Kanaji

Properties of CaCl2 hydrate with an inorganic powder. Part 2.—Melting behaviour and thermodynamic properties of CaCl2·nH2O (n= 6.00–7.35) with α-Al2O3 or α-SiC powder

The melting behaviour of CaCl2·nH2O (n= 6.00 and 7.35) coexisting with two powders, α-Al2O3 and α-SiC, has been investigated by differential scanning calorimetry (DSC). With α-Al2O3 powder and CaCl2· 6.00H2O, the melting point of the hydrate and the molar enthalpy of melting decreased as the water content decreased and the specific surface area of the powder increased. The observed melting point corresponded to the transition point shown by the electrical conductivity. With α-SiC powder and CaCl2· 6.00H2O, the melting point and molar enthalpy of fusion for the hydrate were constant over the range 17.2–48.0 vol.% hydrate content. These observations led to the conclusion that the phase transition of the hydrate near the surface of the solid phase was significantly influenced by the hydrophilicity of the surface of the powder.

Properties of CaCl2 hydrate with an inorganic powder. Part 1.—Electrical conductivity of CaCl2·nH2O (n= 6.00–7.35) with α-Al2O3 powder

Electrical conductivity and its temperature dependence have been measured for mixtures of α-Al2O3 powder and CaCl2·nH2O (n= 6.00–7.35) with liquid content 17.1–42.9 vol.%. The influence of the solid surface on electric conduction and phase transition in the liquid phase is discussed. Plots of the logarithm of the electrical conductivity, ln σ, vs. reciprocal temperature, 1/T, showed an abrupt change of slope at a temperature, Tt, the deflection point. The value of Tt appears to correspond to the end-point of the melting of the hydrate. The value of Tt decreased as the liquid phase decreased and as n increased. The activation energy for the electrical conductivity, ΔEa, decreased with increase in the apparent average thickness of the liquid phase up to 30–40 nm, after which ΔEa became constant. These results show that the thickness of the liquid layer which exists on, and is influenced by, the solid phase is ca. 30–40 nm. In this region, the melting point of the hydrate melt tends to be lowered and this change contributes to the electric conduction of hydrate at temperatures below the melting point.

The Electrical Conductivity of Solid/Liquid Coexisting Systems: Composition Dependence of the Electrical Conductivity

The electrical conductivity was measured for α-Al 2 O 3 powder/various kinds of chloride aqueous solution coexisting systems, and its composition dependence was investigated. We applied the equation of the percolation theory, (σ/α 0 )=a(Φ l -Φ c ) m , (Φ l >Φ c ), for the prupose of discussion for the composition dependence and tried to give some definitions of the parameters. The composition dependence of the electrical conductivity was influenced by the specific surface area of the solid phase, concentration of electrolyte, and ionic species in the liquid phase. In most cases, because the threshold value, Φ c , was close to zero, the dependence was nearly equivalent to Archies equation, (σ/σ 0 )=αΦ l sm. For the system containing the powder with large specific surface area as the solid phase, the composition dependence deviated from Archies equation

The Electrical Conductivity of Solid/Liquid Coexisting Systems Aqueous Solution System

The electrical conductivity and its temperature dependence were investigated for α-Al 2 O 3 powder/CaCl 2 aqueous solution coexisting system by ac impedance method. The electrical conductivity of the paste unusually decreased with an increase of the volume fraction of the solid phase. The temperature dependence of the electrical conductivity of log a s. 1/T showed a good linear relationship for the system containing the dilute solution as a liquid phase. The activation energy for the electrical conductivity, ΔE a , was determined from the temperature dependence

Discrimination of Ceramics—Study on the Microstructures of Ceramics

A method for discrimination of alumina ceramics was developed based on the observation of the surface morphology of etched surfaces, density, X-ray diffraction line profiles and grain size distributions. The experimental observations of the surface microstructure were made, using the scanning electron microscopy (SEM), on several different alumina ceramics with high (>99%), middle (96 to 98%) and low (approximately 92%) alumina content in order to identify them. The samples were prepared with a sulfuric acid (4.5 mol/L) etching method performed at 150 ≈ 200°C for 2 h on low and middle purity alumina ceramics and for 4 h on high purity alumina ceramics. The results indicate that the SEM observation coupled with computerized image analysis to determine grain size distribution is a powerful tool to discriminate among alumina ceramics that exhibit similar morphological characteristics. The X-ray diffraction line profile study is suggested as an additional useful index for the determination of microcrystalline structure.

Determination of calcium ion in the presence of phosphate anion and collagen by capillary-type isotachophoresis

Abstract A new procedure for the determination of Ca2+ 1in the presence of phosphate anion and collagen was developed using capillary-type isotachophoresis. Ca2+ could be determined successfully using a leading electrolyte containing 1 · 10−2M potassium acetate-acetic acid (pH 5.4) and a terminating electrolyte containing 1 · 10−2Mn-hexanoic acid in the presence of collagen. Phosphate anion influenced the determination of Ca2+ at pH greater than 3 but not at pH 2–3. The calcium in several calcium phosphates was determined successfully by adjusting the pH of sample solutions made from them to between 2 and 3 with hydrochloric acid.

Effect of added MoO3 and tungsten on photoelectrochemical behavior of thermally decomposed WO3 electrodes.

パラタングステン酸アンモニウムの熱分解により得られた多結晶WO3n-型半導体電極は, 酸性溶液中 (0.5mol/dm3 硫酸水溶液) で, 金属タングステンの直接酸化, CVD などにより調製された WO3 薄膜電極と同様の良好な光応答性を示した。さらに熱分解で得られた WO3に, MoO3 およびタングステン金属粉末を添加した電極について光電気化学特性および積分球を用いた光吸収スペクトルを測定することにより, 不純物添加効果を検討した。その結果MoO3 ならびにタングステン金属粉末の添加濃度がWO3 に対するモル比で 5×103 付近で光電流は, WO3 単一組成電極の約 1.5 倍に増大した。これらの挙動は不純物によるドナー濃度の変化によるものと推定された。これら電極の光電流は, 光励起により生成したホールが関与した酸素発生反臨であった。また光吸収スペクトル測定により得られたみかけの光吸収係数とフォトンエネルギーの依存性より光学的バンドギャップを決定した。その結果バンドギャップエネルギーに対する不純物添加の顕著な影響は認められず,得られたバンドギャップ値 2.6eV は, バンド-バンド間接遷移によるバンドギャップに対応していた。