Hidetoshi Masuda

Transient calorimetric technique for measuring total hemispherical emissivities of metals with rigorous evaluation of heat loss through thermocouple leads

An apparatus for the transient calorimetric technique used for measuring the total hemispherical emissivities of metals has been developed. Measurements have been made on specimens of copper and aluminum in the temperature range of 330–630 K. An exact analysis is given of the conduction heat loss through thermocouple leads suspending the specimen. From the numerical results of the lead-wire heat loss, the significant effect of a guard heater employed in the apparatus is illustrated. By taking account of the heat loss, the emissivities of the specimens are accurately evaluated and are compared with the data of previous investigators.

Simultaneous measurements of specific heat and total hemispherical emissivity of chromel and alumel by a transient calorimetric technique

Using a transient calorimetric technique, the specific heat and total hemispherical emissivity of chromel and alumel were measured simultaneously in the temperature range 360–760 K. Two types of specimens for each material were prepared. To obtain reliable experimental values of specific heat and total hemispherical emissivity, an expression for the time history of the temperature of the specimens was developed; this expression is accurate over the whole temperature range. An error analysis is made and the uncertainty (the total error) in the values of specific heat and total hemispherical emissivity is estimated to be 3.1% for the well-designed specimens.

Synthesis, crystal structure refinement and electrical properties of uranium oxysulfide, UOS

Abstract Gas–solid reactions of UO2SO4 with H2, H2S and CS2 to form uranium (IV) oxysulfide, UOS, as a single phase were studied on the basis of thermodynamical analysis of these reactions. H2S was proved to be the best reaction agent. The reaction of UO2SO4 with CS2 resulted in the formation of UOS and US2 mixtures. A refinement of the crystal structure of UOS was made giving isotropic temperature factors and a smallest R value of 1.71%. The obtained UOS showed a p-type semi-conductivity with activation energy 67.5 meV.

Measuring the specific heat capacity of magnetic fluids using a differential scanning calorimeter

The specific heat capacity of magnetic fluids was measured using a heat-flux-type differential scanning calorimeter (DSC). Magnetic fluids which contain 10 to 43 wt% ultrafine magnetite (Fe3O4) particles dispersed with surfactants in water or kerosene were used. The DSC was operated with the optimum heating rate (10 K·min−1) and with equal heat capacities of sample and standard materials in the temperature range, 295 to 345 K. Synthetic sapphire (α-Al2O3) was used as the standard reference material, and the sample pan was made from aluminum. The differences between the measured specific heat capacity values of pure water and pure copper and the recommended values were within ±3 and ±1%, respectively. The specific heat capacity data of magnetic fluids showed weak temperature dependence, but strong concentration dependence. The measured values of specific heat capacity of magnetic fluids were compared with calculated values using a mixing rule.

Synthesis and crystal structure of alkali metal uranium sulfides, Li2US3 and Na2US3

Abstract New mixed uranium sulfides, A 2 US 3 (A=Li, Na), in which uranium is in a tetravalent state, have been synthesized. In the disordered state, the compounds are written as A(A 1/3 ,U 2/3 )S 2 which have a hexagonal ( R 3 m ) structure the same as the lanthanide homologue, ALnS 2 (Ln=trivalent lanthanides). In the ordered state, the compounds take on a monoclinic ( C 2/ m ) structure in which the atom arrangement is very close to the above hexagonal structure. The partial ordering is realized by the coexistence of the two phases. The lattice parameters of hexagonal Li 2 US 3 are a =3.898 and c =18.391 A, while those of monoclinic Li 2 US 3 are a =6.747, b =11.679, c =6.537 A and β =110.2°. The lattice parameters of hexagonal Na 2 US 3 are a =4.036 and c =19.780 A. Those of monoclinic Na 2 US 3 are a =6.990, b =12.105, c =6.992 A and β =109.5°. The molar ratios of the hexagonal and monoclinic phases are 52.2:47.8 for Li 2 US 3 and 68.0:32.0 for Na 2 US 3 , respectively. The atom parameters of uranium and sulfur were obtained by Rietveld calculation of the observed X-ray peaks. The atom separations are discussed in relation to the crystal radii of the component ions.

A transient heating technique for measuring the thermal diffusivity of metals

A transient heating technique, improving the constant-rate-heating technique for the measurements of thermal diffusivities of metals, is proposed. For a physical model of a specimen to be measured, the transient heat-conduction equation was solved with some boundary conditions, and the solution obtained was used as the principle of the present transient heating technique for determining the thermal diffusivity of the specimen. Additionally, a thermal analysis was made to satisfy a boundary condition involved in the principle, that is, the condition of radiative thermal insulation at the two end surfaces of the specimen. To verify the validity of the present technique, the thermal diffusivity of iron, whose thermophysical properties are well-known, was measured with the same apparatus as used in our previous work, and the experimental results are discussed. Moreover, thermal diffusivities of thermocouple materials, namely, constantan, chromel, and alumel, were measured by the technique in the temperature range of 360 to 680 K.

Crystal structure and magnetic susceptibility of uranium palladium sulfide bronze, UxPd3S4

Abstract The lattice parameter of cubic U x Pd 3 S 4 was measured by X-ray diffractometry for various apparent x values between 0.5 and 1.5. It seemed to change with x , but the existence of a non-stoichiometric range for uranium could not be definitely determined since the product was not in a single phase. The Rietveld refinement for U x Pd 3 S 4 ( x =1) showed that the compound was U 0.90 Pd 3 S 4 and that the space group was Pm3n with the final R I value of 0.052. The lattice parameter was 6.637(1) A, and the isotropic temperature factors were 0.59, 0.70 and 0.70 A 2 for U, Pd and S, respectively. The measured reciprocal magnetic susceptibility for U 0.90 Pd 3 S 4 was not a linear function of temperature. From the slope in a temperature range of 50–200 K, the effective magnetic moment was obtained, which showed that both the U 4 + and U 3 + ions are present in this compound in nearly the same amounts.

A method for the simultaneous measurement of total hemispherical emissivity and specific heat of metals by the transient calorimetric technique

Abstract A resistive self-heating technique by which an electric current is passed through a specimen has been applied to multiple measurements of the thermophysical properties of metals. An alternative approach is proposed for the simultaneous measurement of the total hemispherical emissivity ϵh and specific heat c of metals. The measuring method used here is the transient calorimetric technique, which has been used in the past only for measuring ϵh of metals. In the proposed approach, it is necessary to prepare two types of specimens, one made of a metallic material to be measured, and the other a compound specimen constructed of both the material to be measured and a standard reference metallic material whose emissivity and specific heat are well known. The ϵh and c values of the measured material can be simultaneously determined from the experimental results obtained for the two specimens, that is, the two temperature-versus-time curves. Constantan and copper were selected as the material to be measured and the standard reference material, respectively, and were used for the two types of specimens. The measurements were performed in the temperature range of 380–720 K, and the ϵh and c values were obtained. From the results, it was verified that the proposed approach is applicable to the simultaneous measurement of the total hemispherical emissivity and specific heat of metals.

Preparation and structure of quaternary mixed sulphide Li(Lu,M)S2 (M=U,Ce)

Abstract The Li(Lu,M)S 2 (M=U,Ce) compounds were prepared by the reaction of the weighed mixture of Li 2 CO 3 , Lu 2 O 3 and UO 2 or CeO 2 in a CS 2 +N 2 gas mixture at 800°C for 2 h. It was proved that a series of Li(Lu y U 1− y )S 2 compounds showed an NaCl-type structure in a wide range of y values from 0.2 to 0.8, while the ternary sulphides LiLuS 2 and Li 2 US 3 crystallized in hexagonal α -NaFeO 2 -type structure (R3m) and monoclinic structure (C2/m), respectively. The Rietveld refinement showed that the compound was Li 1.5 Lu 0.5 U 0.5 S 2.5 with cubic lattice parameter 5.420 A and that the space group was Fm3m with the final R I value of 0.027. A series of Li(Lu y Ce 1− y )S 2 compounds also showed the NaCl structure in a range of y values from 0.4 to 0.8, though LiCeS 2 adopts a Th 3 P 4 structure. The final R I value for the compound Li 1.17 Lu 0.5 Ce 0.5 S 2.17 with cubic lattice parameter 5.531 A was 0.052 after the Rietveld refinement.

Control of Radiation Heat Transfer from Solid Surface Using Grating Composed of Parallel Elliptical Cylinders. Energy Concentration in Direction Normal to Solid Surface.

A specially designed grating is applicable to directional control of radiation heat transfer from a heated surface. In this paper, a study of radiation heat transfer control using a grating composed of elliptical cylinders (GEC) is described. An analysis of radiation heat transfer is performed for a physical model in which the grating of circular cylinders (GCC) of our previous study are replaced by the GEC and the major or minor axes of the elliptical cylinders are set vertically to the heated base surface. Numerical solutions are obtained. The apparent hemispherical emissivity and the limiting angle expressing the degree of radiation energy concentration are calculated for geometrical parameters, e. g., ratio of the major axis to the minor axis and center-to-center distance of cylinders. It is found that the GEC has even better characteristics for the control of radiation heat transfer, compared with the GCC, especially for apparent hemispherical emissivity, i. e., the heat-transfer rate.