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Journal Articles

Measurement of density and viscosity for molten salts

Sato, Rika*; Nishi, Tsuyoshi*; Ota, Hiromichi*; Hayashi, Hirokazu; Sugawara, Takanori; Nishihara, Kenji

Dai-43-Kai Nihon Netsu Bussei Shimpojiumu Koen Rombunshu (CD-ROM), 3 Pages, 2022/10

no abstracts in English

Journal Articles

In-situ microscopic observation of crystal growth of graphene using thermal radiation

Terasawa, Tomoo; Saiki, Koichiro*; Yasuda, Satoshi; Asaoka, Hidehito

Dai-39-Kai Nihon Netsu Bussei Shimpojiumu Koen Rombunshu (CD-ROM), p.262 - 264, 2018/11

Graphene, monolayer graphite, has been expected as one of the new materials targeting the next generation electronics since its first isolation in 2004, due to the ultrahigh carrier mobility up to 100,000 cm $_{2}$ /Vs and high transparency of 97.7%. The high transparency of graphene make it invisible on various substrates. Particularly, graphene on Cu, one of the common growth substrates for high-quality graphene, cannot be observed by optical microscopes. Here, we report the optical microscopic method to visualize graphene using thermal radiation. We observed a Cu surface by a zoom-lens and a CMOS camera during the growth of graphene by chemical vapor deposition. When graphene was grown on Cu substrates, the thermal radiation intensity increased at the area covered with graphene. The thermal radiation contrast between Cu surfaces with and without graphene showed that the thermal radiation intensity increased as the number of graphene layers in a layer-by-layer manner. We quantitatively analyzed the thermal radiation contrasts at various temperatures. We found the thermal radiation contrast was independent from the sample temperature. This result suggests that the emissivity of graphene is independent from the temperature, which is consistent with the theory of the optical properties of graphene. Our findings are essential for the discussion of the thermal radiation from the atomically thin materials including graphene.

Journal Articles

Thermal conductivity of minor actinide nitride fuels

Nishi, Tsuyoshi; Takano, Masahide; Arai, Yasuo; Kurata, Masaki

Dai-34-Kai Nihon Netsu Bussei Shimpojiumu Koen Rombunshu, p.199 - 201, 2013/11

By installing the laser flash apparatus and the drop calorimeter in the glove box, the thermal diffusivity and the heat capacity measurements of nitride containing MA elements of long-lived radioactive nuclides were enabled. The sample holder and the platinum container were designed to measure the thermal diffusivity and the heat capacity of very small quantity of MA nitride samples. The thermal conductivities of MA nitride increased with temperature, unlike that of conventional oxide-type nuclear fuels. In addition, the thermal conductivities of MA nitride decreased with increasing Am contents. The thermal conductivity of ZrN-based MA nitride, which is proposed as a candidate material for the ADS fuel, was fitted to equations as functions of the temperature and ZrN concentration. The predicted values agreed well with the experimental ones, indicating that the thermal conductivity of nitride fuel for ADS can be predicted for a practical design.

Journal Articles

Measurement of thermal property for tungsten-stainless steel alloy and high purity tungsten

Kawai, Masayoshi*; Li, J.*; Watanabe, Ryuzo*; Kurishita, Hiroaki*; Kikuchi, Kenji; Igarashi, Tadashi*; Kato, Masahiro*

Dai-23-Kai Nihon Netsu Bussei Shimpojiumu Koen Rombunshu, p.313 - 315, 2002/11

The objective of the present study is to develop the stainless-steel-bonded tungsten alloys by powder metallurgy processes. Commercially available tungsten powders and stainless steel (SUS304L) powder were used as the raw materials and mixed by ball milling at the ratios of 97mass% W -3% SUS and 93mass% W -7mass% SUS. Powder compacts were formed by die pressing and cold isostatic pressing (CIP), then sintered mainly in vacuum at the temperatures above the melting point of the stainless steel phase. Some samples were fabricated by glass-encapsulated hot isostatic pressing (HIPing) at lower temperatures. The microstructural observation was made by scanning electron microscopy (SEM). The thermal properties of the produced alloy and various tungsten materials supplied from Allied Material Corp. was measured with the laser-frash method. It was found that stable liquid-phase-sintered microstructures were not easily formed in the tungsten-stainless steel system. The electron probe microanalysis (EPMA) revealed that tungsten was considerably dissolved in the stainless steel phase during sintering. Therefore, thermal conductivity of the W/7 mass% SUS alloy was 22.8-53.5 W/m/K that was very lower than theoretical value calculated from those of pure tungsten and stainless steel. Its temperature dependence is resembled to that of stainless steel, i.e., thermal conductivity increased with the specimen temperature as like stainless steel. The diffusivity of pure tungsten is compared with those of tungsten alloys.

Journal Articles