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Volume 17 (1990)
- Issue 4 Pages 171-
- Issue 3 Pages 113-
- Issue 2 Pages 61-
- Issue 1 Pages 2-
Volume 17, Issue 1
Displaying 1-6 of 6 articles from this issue
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Hideto Matsuo1990 Volume 17 Issue 1 Pages 2-8
Published: January 30, 1990
Released on J-STAGE: September 07, 2009
JOURNAL FREE ACCESSThe thermal diffusivities of POCO graphite AXM-5Q1 and isotrophic graphite IG-110, the candidate graphite material for a High-Temperature Engineering Test Reactor (HTTR), were measured from room temperature to around 2000°C by laser flash method. The thermal conductivities of these materials were also calculated using the literature values of heat capacities. AXM-5Q1 showed a little different behavior at around room temperature to 100°C comparing with the results previously reported in the literatures, whereas at high temperatures it showed almost the same values. Measurements on IG-110 graphite were made on the specimens cut from two graphite blocks, and the mean value and its standard deviation were determined. Measurements were also made on neutron-irradiated IG-110 as well. The conductivities were found to decrease after irradiation and a different temperature dependence was observed. They showed a peak at around 200°C, the degree of the decrease depending on irradiation condition. It was considered that the shift of the peak was caused owing to the degradation of crystallites by neutron irradiation.View full abstractDownload PDF (875K) -
Toshiya Kumagai, Hiroshi Yokota, Susumu Mizuta1990 Volume 17 Issue 1 Pages 9-15
Published: January 30, 1990
Released on J-STAGE: September 07, 2009
JOURNAL FREE ACCESSPyrolyses in Ar and air for the mixture of Y-, Ba-, and Cu-naphthenates or laurates with the molar ratio, Y:Ba:Cu=1:2:3, and subsequent solid state reactions among the solid products Y2O3, BaCO3 and CuO were studied by thermogravimetry (TG), differential thermal analysis (DTA), infrared (IR) and X-ray diffraction (XRD) analyses.
(1) In the mixture of Y-, Ba- and Cu-naphthenates, each constituent naphthenate was independently pyrolyzed boh in Ar and air and no particular mixing effects among them were observed,
(2) In the mixture of Y-, Ba- and Cu-laurates, mutual interactions or special mixing effects among the constituent laurates were found: (i) Main pyrolysis processes of Ba-laurate and Y-laurate simultaneously occurred both in Ar and air, (ii) Pyrolysis of Cu-laurate takes place prior to that of Ba-laurate in air, thus, a dense layer of CuO formed on the surface of the specimen depressed total completion of the pyrolysis on the final stage.
(3) Further heating the solid product mixture (Y2O3, BaCO3 and CuO) up to 900°C yielded YBa2Cu3O7-δ, where a slight amount of Y2Cu2O5 was observed below 800°C.View full abstractDownload PDF (835K) -
Yoshinori Ihara1990 Volume 17 Issue 1 Pages 16-24
Published: January 30, 1990
Released on J-STAGE: September 07, 2009
JOURNAL FREE ACCESSNew type of isomeric transformation from square-planar (low spin) to octahedron (high spin) was discovered and investigated in the thermal reactions of bis (C-substituted ethylenediamine) nickel (II) complexes, [Ni(diamine)2]X2(X=C1, Br, or NO3), in the solid phase. This transformation which proceeded endothermically and was accompanied by a thermochromism from yellow to blue-violet was of discontinuous and reversible. Obvious differences in the reactivity were observed among the complexes with the mono-substituted, 1, 1-di-substituted, dl-form of 1, 2-di-substituted, and meso-form of 1, 2-di-substituted ethylenediamines. This indicates that this type of reaction (and the stability of the square planar species or octahedral ones) is strongly dominated by the steric effect of the substituent group(s) in the coordinated diamines. The enthalpy changes for these endothermic transformations (< 15.9kJmol-1) suggest that the energy gap between square planar and octahedral structures is very small. The activation energies for them were also estimated. The results of all the thermal reactions of the nickel (II) complexes with twelve kinds of C-substituted ethylenediamines, including the transformations, are summarized and discussed systimatically.View full abstractDownload PDF (1119K) -
Norikazu Komada1990 Volume 17 Issue 1 Pages 25-31
Published: January 30, 1990
Released on J-STAGE: September 07, 2009
JOURNAL FREE ACCESSMagnetic heat-capacity anomalies of deerite and grunerite, both of which are silicate minerals containing Fe ions, were resolved by using the new isometric molar lattice heat-capacity formula. In the process of the resolution, apparent θKW, the single fitting parameter contained in the formula, was evaluated from the experimental heat-capacity data, and since the apparent θKW was nearly constant for the heat capacity at higher temperatures where the lattice contribution is dominant, the constant value of θKW was utilized to estimate the lattice heat capacity at low temperatures. The resulting heat-capacity anomaly of deerite was composed of a main peak centered at about 16K which resembles a Schottky anomaly and a symmetric sub-peak centered at about 34K. The heat-capacity anomaly of grunerite which has a sharp peak at 35.5K was found to show a curvature change in the high-temperature side of the slope. The feature is qualitatively explainable by the randomly diluted Ising model. It treats random disruption of spin interaction by non-magnetic ions such as Mg ions which replace a portion of Fe ions.View full abstractDownload PDF (1004K) -
Iwao Katayama1990 Volume 17 Issue 1 Pages 32-40
Published: January 30, 1990
Released on J-STAGE: September 07, 2009
JOURNAL FREE ACCESSThe recent studies concerning the thermodynamic properties of the solid state materials derived from the emf method with the solid electrolytes are reviewed. Materials described in this paper are solid alloys, intermetallic compounds, compound solid solutions, oxides, oxide solid solutions, and some carbides. This paper was intended to compensate for reviews by us (ref. 5 and 7) and by Pratt (ref. 10).View full abstractDownload PDF (1276K) -
Toshihide Tsuji1990 Volume 17 Issue 1 Pages 41-54
Published: January 30, 1990
Released on J-STAGE: September 07, 2009
JOURNAL FREE ACCESSThe oxygen partial pressure as well as temperature and the composition of oxide are one of the important parameters for studying phase equilibria. Thermodynamic properties of phase boundaries and those of nonstoichiometric oxide are obtained from the phase diagram. The defect structures of nonstoichiometric oxide are discussed from the oxygen partial pressure dependence of the departure from stoichiometric composition and that of the electrical conductivity.
The solid electrolyte and oxide semiconductor oxygen sensors are used for measurement of the oxygen partial pressure. The principle and some problems of measurement, and characteristics of each oxygen sensor are reviewed briefly, and both oxygen sensors are compared each other.
The oxygen partial pressures in the intermediate and low oxygen partial pressure ranges are controlled precisely by pumping oxygen into or from flowing (or circulating) gases such as inert, CO2 and H2 gases with a stabilized zirconia cell.
The application of oxygen sensor and oxygen pump to obtain thermodynamic properties of phase boundaries and nonstoichiometric oxide, and to determine defect structure of nonstoichiometric oxide at constant temperature is described.View full abstractDownload PDF (2044K)
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