Netsu Sokutei
Online ISSN : 1884-1899
Print ISSN : 0386-2615
ISSN-L : 0386-2615
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Volume 46, Issue 3
Displaying 1-9 of 9 articles from this issue
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Article
JSCTA Research Encouragement Award 2018
  • Thermodynamic Analyses of Structural and Functional Changes of Cathode Materials of Solid Oxide Fuel Cells Involving the Change of Oxygen Content
    Eiki Niwa
    2019 Volume 46 Issue 3 Pages 103-110
    Published: July 25, 2019
    Released on J-STAGE: November 20, 2022
    DOIhttps://doi.org/10.11311/jscta.46.3_103
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    Solid oxide fuel cell, SOFC, is expected as high-temperature electrochemical devise with the high energy conversion efficiency. In this study, new SOFC cathode materials were explored and their characters were investigated. The perovskite-type (or -related) oxides including 3d transition metal (Mn, Fe, Co, Ni) are usually utilized as SOFC cathode materials. The change of the physical properties such as structural phase transition and thermal expansion of these oxides are more complex than that of standard oxide materials, because oxygen contents of these oxides change by temperature and oxygen partial pressures, P(O2). In this article, the investigation of the functional changes of LaNi0.6Fe0.4O3-δ with oxygen nonstoichiometry at high temperature were reviewed. The temperature and P(O2) dependence of the oxygen nonstoichiometry and electrical conductivity of LaNi0.6Fe0.4O3-δare smaller than that of La0.6Sr0.4Co0.2Fe0.8O3-δ. This is caused by the small change of average valence of Ni and Fe ions for the change of temperature and P(O2) owing to continuous hole exchange between Ni and Fe ions in LaNi0.6Fe0.4O3-δ. Small change of oxygen nonstoichiometry of LaNi0.6Fe0.4O3-δ was also confirmed by other evaluation procedure such as dilatometry. P(O2) dependence of the total linear thermal expansion of LaNi0.6Fe0.4O3-δ was also small compared to La0.6Sr0.4Co0.2Fe0.8O3-δ.
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Review
  • Development and Application of Solution Calorimeter — Guide for Selection of Detection Principle and Design Technique of Calorimeter —
    Hideo Ogawa
    2019 Volume 46 Issue 3 Pages 111-117
    Published: July 25, 2019
    Released on J-STAGE: November 20, 2022
    DOIhttps://doi.org/10.11311/jscta.46.3_111
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    In the past 40 years, several types of solution calorimeters have been designed and constructed in my laboratory. Suitable construction type and detection principle were selected for each calorimeter considering required precision, measurement purpose, term for development and costs or fund. Improved Picker's type flow calorimeter was designed to measure excess heat capacity with “direct mixing” mode, which was enabled by making two flow paths in the each flow cells. Twin conduction type of flow microcalorimeters were developed for excess enthalpy of binary liquid, and enthalpy of dilution of polymer solution taking account of high accuracy and precision. A simple isoperibol calorimeter for heat of solution was constructed using a Dewar vessel to write a text book for undergraduate student at first, however this prototype was succeeded to development of the research level adiabatic one. To visualize the “calorie” of food or fuel, simple combustion calorimeter was assembled using thermometer, stirrer, beaker and flask to record the movie for scientific TV program. In those developing of calorimeter, suitable type of detection, mixing or reaction manner and construction details have been selected to save time and money for construction, and those viewpoints will be important to familiarize means of calorimetry to the scientific research and industrial analysis.
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  • Oxygen Storage Property of Sr3Fe2O7−δ
    Saburo Hosokawa, Tsunehiro Tanaka
    2019 Volume 46 Issue 3 Pages 118-121
    Published: July 25, 2019
    Released on J-STAGE: November 20, 2022
    DOIhttps://doi.org/10.11311/jscta.46.3_118
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    Sr3Fe2O7−δ with layered perovskite structure shows an excellent oxygen storage performance and has significant potential in the fields of oxygen separators/sensors and the purification of polluted materials such as automobile exhaust gas. This review introduces effects of Pd loading on Sr3Fe2O7−δ and of doping with other transition metals (Mn, Co, Ni) into the Fe sites of Sr3Fe2O7−δ. Pd loading dramatically improves oxygen release rate under H2 atmosphere, because Pd species enhances the adsorption and dissociation of H2. Mn doping of Sr3Fe2O7−δ also increases the oxygen release rate of Sr3Fe2O7−δ. Although the local structures around the transition-metal species in Sr3(Fe0.8Co0.2)2O7−δ and Sr3(Fe0.8Ni0.2)2O7−δ are largely disordered by the release of lattice oxygen, the cation ordering of the as-synthesized Sr3(Fe0.8Mn0.2)2O7−δ was maintained by doping with Mn, even in the reduced state. These results indicate that the oxygen release rate under H2 atmosphere largely contributes to the surface reaction and structural changes in the perovskite structures upon release of lattice oxygen.
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  • Texture Control and Thermal Conductivity of Aluminum Nitride Ceramics
    Ryota Kobayashi, Hiroya Okazaki, Makoto Sasaki, Emiko Fukushi
    2019 Volume 46 Issue 3 Pages 122-127
    Published: July 25, 2019
    Released on J-STAGE: November 20, 2022
    DOIhttps://doi.org/10.11311/jscta.46.3_122
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    Aluminum nitride (AlN) is one of typical non-oxide ceramic materials that have intrinsic high thermal conductivities and electrical insulation. Therefore, AlN ceramics have been applied to substrate materials for power devices. AlN is a sintering resistant ceramic due to its high covalence. High temperature and long sintering time with sintering aids are required to obtain dense AlN ceramics. Although sintering temperature of AlN ceramics can be lowered by using low temperature sintering additives and pressure assisted sintering, the low-temperature-sintered AlN ceramics do not show superior thermal conductivity due to the increase of grain boundary caused by the restrained grain growth. To solve these problems, controlling the shape and orientation of AlN grains seems to be useful, as are adjustment of sintering conditions and additives. In this review, we introduce the densities, microstructures, and thermal conductivities of texture controlled AlN ceramics by addition of coarse AlN particles or AlN whiskers. Although the addition of coarse AlN particles or AlN whiskers slightly decreases the relative densities of AlN ceramics, dense textures containing the coarse particles or whiskers are obtained. Samples containing AlN whiskers show an anisotropic thermal conductivity originated from the orientation of AlN whiskers in the samples.
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  • Development of an Absolute Measurement Technique for the Seebeck Coefficient using the Thomson Effect
    Yasutaka Amagai, Takeshi Shimazaki, Kenjiro Okawa, Hiroyuki Fujiki, No ...
    2019 Volume 46 Issue 3 Pages 128-134
    Published: July 25, 2019
    Released on J-STAGE: November 20, 2022
    DOIhttps://doi.org/10.11311/jscta.46.3_128
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    The Seebeck coefficient is the most widely measured property specific to thermoelectric materials. The absolute Seebeck coefficient S determined from the Thomson effect is highly sensitive to systematic errors incurred in the determination of the material thermal conductivity and geometry and heat loss from the sample to surroundings caused by temperature differences. Here, we review a technique for the precision measurement of S based on the Thomson effect using an AC-DC technique. This technique utilizes accurate equivalent-amplitude AC and DC currents, which can eliminate the need for acquiring accurate thermal conductivity and geometry values. These parameters can be replaced by the precisely and readily measurable parameters of electrical resistance and temperature changes caused by the Joule effect. The correction term of the heat loss owing to heat transfer via the thermocouple vanishes upon calculating the ratio of the measured temperature changes for both AC and DC excitations.
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  • Investigation of Electronic States by Angle-Resolved Magnetic Heat Capacity Measurements by Using High-Resolution Calorimeters Designed for Small Amounts of Samples
    Shusaku Imajo, Sotaro Fukuchi, Yasuhiro Nakazawa
    2019 Volume 46 Issue 3 Pages 135-141
    Published: July 25, 2019
    Released on J-STAGE: November 20, 2022
    DOIhttps://doi.org/10.11311/jscta.46.3_135
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    To investigate electronic states under extreme conditions such as low temperatures, high magnetic fields, and high pressures, are of special importance because electronic systems are strongly affected by external perturbations since they have quantum mechanical degrees of freedom. Therefore, developments of high-resolution physical property measurements in such extreme conditions are situated in the essential position for precise discussion of physical properties. We have been engaged in developments and improvements of calorimetry technique and high-resolution calorimeters to obtain precise thermodynamic information utilized for cultivated discussions of electronic states. In this work, some relaxation calorimeters were designed for low-temperature heat capacity measurements with extremely small amounts of samples with external magnetic fields whose directions against crystal axes are precisely controlled. Employing these calorimeters, we have performed thermodynamic discussion on the low-temperature electronic and magnetic states of organic conductors. Because they have a rich variety of electronic phases originating from the molecular degrees of freedom, detection of phase transitions and low energy excitations by heat capacity can give entropic information to clarify the mechanism of the phenomena. Our high-resolution calorimeters have succeeded to provide some novel insights into the electronic states formed by π-electrons. We also introduce the process of the developments of the calorimeters and show our recent results of heat capacity measurements of some organic salts.
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