山本 宏明

The electrodeposition of Fe-Al alloy in AlCl3-NaCl-KCl-FeCl2 quaternary molten salts was investigated by potentiostatic electrolysis to prepare Fe-Al alloy film with a thermoelectric conversion function. In the AlCl3-NaCl-KCl-FeCl2 molten salts with an AlCl3/FeCl2 mole ratio of 200 (FeCl2: 32.6 mmol l(-1)), the electrodeposited Al formed a solid solution with Fe in the potential range from 0.5 to 0.2 V vs Al(III)/Al and formed the intermetallic compound of Fe3Al at the potential of 0.1 V. Fe-Al alloys containing 0.8-34.5 mol% Al were obtained by controlling the AlCl3/FeCl2 mole ratio (FeCl2 concentration) in AlCl3-NaCl-KCl-FeCl2 molten salts and the applied potential in the potential range from 0.2 to -0.1 V vs Al(III)/Al. The Fe-Al alloy films prepared in the present study exhibited the p- or n-type thermoelectric conversion, depending on their composition.

The standard Gibbs energies of formation, Delta(f)G(o), of CrB4, CrB2, Cr3B4, Cr5B3, and CrBO3 existing along the oxidation path of Cr-B binary alloy were determined using the electromotive forces of galvanic cell composed of the ZrO2-Y2O3 solid electrolyte. The electromotive force showed plateaus and decreases in the process that CrB4-CrB2 two-phase alloy used for the cell materials were oxidized via two- and three-phase regions along its oxidation path. From the plateaus of electromotive forces corresponding to the cell materials in the three-phase regions, the values of Delta(f)G(o)(CrB4), Delta(f)G(o)(CrB2), Delta(f)G(o)(Cr3B4), Delta(f)G(o)(Cr5B3), and Delta(f)G(o)(CrBO3) in the temperature range from 1273 to 1346 K were determined as follows:Delta(f)G(o)(CrB4)/J (mol of compd.)(-1) = 167500 - 261.2 T +/- 7200Delta(f)G(o)(CrB2)/J (mol of compd.)(-1) = -21020 - 79.22 T +/- 2100Delta(f)G(o)(Cr3B4)/J (mol of compd.)(-1) = -173400 - 95.47 T +/- 2500Delta(f)G(o)(Cr5B3)/compd.)(-1) = -318900 + 20.64 T +/- 5800Delta(f)G(o)(CrBO3)/J (mol of compd.)(-1) = -958800 + 59.24 T +/- 4100The Delta(f)G(o) values determined in the present study satisfied the phase equilibria in the Cr-B binary system. Using the determined Delta(f)G(o) values, the composition-oxygen partial pressure diagram of the Cr-B-O system was constructed under the conditions at 1300 K and a total pressure of 1 bar (100 kPa). It is useful to understand the oxidation property of the Cr-B binary alloys.

The standard Gibbs energies of formation, Delta(f)G degrees, of intermediate compounds of Cr3B4, CrB2, and CrB4 in the boron-rich side of the Cr-B binary system were determined by measuring electromotive forces of the galvanic cells using ZrO2-Y2O3 solid electrolyte. The phase equilibria for the Cr-B binary system were clarified to construct the cells using the solid electrolyte. The measured electromotive forces of the cells were evaluated as linear temperature functions under the conditions that the transport numbers of oxide ion in solid electrolyte were regarded as 1.0. The Delta(f)G degrees functions determined from the electromotive forces via the Nernst equation were as follows:Delta(f)G degrees(Cr3B4)/J (mol of compd)(-1) = -264540 - 26.697 T +/- 970 (1256-1322 K),Delta(f)G degrees(CrB2)/J (mol of compd)(-1) = -84572 - 32.442 T +/- 790 (1253-1350 K),Delta(f)G degrees(CrB4)/J (mol of compd)(-1) = -105120 - 57.921 T +/- 2200 (1280-1352 K).The present Delta(f)G degrees values satisfied the phase equilibria in the Cr-B binary system. Using the Delta(f)G degrees values determined in the present study, the composition-oxygen partial pressure diagram of the Cr B-O ternary system was constructed under the conditions of 1300 K and a total pressure of 1 bar (100 kPa). It is useful to understand the oxidation path of the boron-rich side of Cr-B binary alloys.