This paper describes an experimental study of the relationships between thermal diffusivity and m... more This paper describes an experimental study of the relationships between thermal diffusivity and mechanical characteristics including Brinell hardness, microhardness, and Young’s modulus of common pine (Pinus sylvestris L.), pedunculate oak (Quercus robur L.), and small-leaf lime (Tilia cordata Mill.) wood. A dependence of Brinell hardness and thermal diffusivity tensor components upon humidity for common pine wood is found. The results of the measurement of Brinell hardness, microhardness, Young’s modulus, and main components of thermal diffusivity tensor for three perpendicular cuts are found to be correlated. It is shown that the mechanical properties correlate better with the ratio of longitude to transversal thermal diffusivity coefficients than with the respective individual absolute values. The mechanical characteristics with the highest correlation with the abovementioned ratio are found to be the ratio of Young’s moduli in longitude and transversal directions. Our technique ...
Reliable thermophysical property values of thin films are important to develop advanced industria... more Reliable thermophysical property values of thin films are important to develop advanced industrial technologies such as highly-integrated electric devices, optical disks, magneto-optical disks, and thermoelectric devices. In order to meet this requirement, the National Metrology Institute of Japan of the National Institute of Advanced Industrial Science and Technology (NMIJ/AIST) has developed thermoreflectance methods by picosecond pulse heating and nanosecond pulse heating under the same geometrical configuration to the laser flash method which is the standard method to measure thermal diffusivity of bulk materials. These light pulse heating methods observe one-dimensional heat diffusion across well-defined length of the specimen thickness. Thermal diffusivity values across thin films were measured with small uncertainty. Since the geometry is very simple, thermal diffusivity can be determined reliably with uncertainty evaluation based on Guide to the Expression of Uncertainty in ...
We present a study of the of thermal transport in thin single crystals of iron-intercalated titan... more We present a study of the of thermal transport in thin single crystals of iron-intercalated titanium disulphide, Fe x TiS 2 for 0 ≤ x ≤ 0.20. We determine the distribution of intercalants using high-resolution crystallographic and magnetic measurements, confirming the insertion of Fe without long-range ordering. We find that iron intercalation perturbs the lattice very little, and suppresses the tendency of TiS 2 to self-intercalate with excess Ti. We observe trends in the thermal conductivity that are compatible with our ab initio calculations of thermal transport in perfectly stoichiometric TiS 2 .
-Measurement technology, metrological standard, standardization of measurement method, and databa... more -Measurement technology, metrological standard, standardization of measurement method, and database for thermal diffusivity by laser flash method - The National Metrology Institute of Japan implemented a system to supply reliable thermal diffusivity data efficiently and rapidly to society. The system was born out of R&D on technology for thermal diffusivity measurement by using a laser flash method, by establishing a metrological standard and reference materials, and by standardization of measurement technology. Uncertainty in measurement of thermal diffusivity with practical apparatus was reduced using technology to homogenize the laser beam, a fast response infrared thermometer, and a curve fitting method to analyze temperature response curves. JIS and ISO standards were established based on the advanced laser flash method. In addition, methods to evaluate uncertainty in measurement of thermal diffusivity and laser flash device calibration by reference materials are described in the latest update of the JIS standard. Traceable thermophysical property data produced by this system are stored in a database system developed and operated by the National Metrology Institute of Japan (NMIJ), which can be accessed from the web.
Thermoreflectance methods by picosecond pulse heating and by nanosecond pulse heating have been d... more Thermoreflectance methods by picosecond pulse heating and by nanosecond pulse heating have been developed under the same geometrical configuration as the laser flash method by the National Metrology Institute of JAPAN, AIST. Using these light pulse heating methods, thermal diffusivity of each layer of multilayered thin films and boundary thermal resistance between the layers can be determined from the observed transient temperature curves based on the response function method. The measurement results of various thin films as transparent conductive films used for flat panel displays, hard coating films and multilayered films of the next generation phase-change optical disk will be presented.
Ceramics-based thermal barrier coatings are used as heat and wear shields of gas turbines. There ... more Ceramics-based thermal barrier coatings are used as heat and wear shields of gas turbines. There are strong needs to evaluate thermophysical properties of coating, such as thermal conductivity, thermal diffusivity and heat capacity of them. Since the coatings are attached on substrates, it is no easy to measure these properties separately.
ABSTRACT We have developed a thermal effusivity measurement system that can measure distribution ... more ABSTRACT We have developed a thermal effusivity measurement system that can measure distribution of local thermal effusivity of inhomogeneous materials. A specimen is uniformly coated with a molybdenum thin film of about 100 nm thick before the measurements. A modulated beam from an argon-ion laser sinusoidally heats a small spot of the specimen surface. Absorbed heat in the molybdenum film diffuses into the specimen and the local temperature of the heated spot changes proportionally to the sinusoidal heating with a phase lag. The temperature change of the molybdenum film surface at the same spot is measured with the thermoreflectance technique. The phase responses of the 50 nm, 100 nm, 200 nm and 500 nm molybdenum thin films deposited on the Pyrex 7740 glass substrates were measured to verify the validity of the measurement technique.
We have developed a laser flash apparatus for simultaneous measurements of thermal diffusivity an... more We have developed a laser flash apparatus for simultaneous measurements of thermal diffusivity and specific heat capacity of solid materials by introducing recent technical progress: uniform heating by a homogenized laser beam using an optical fiber with a mode mixer, measuring transient temperature of a specimen with a calibrated radiation thermometer, analyzing a transient temperature curve with a curve fitting method, to achieve differential laser flash calorimetry. Thermal diffusivity, specific heat capacity and thermal conductivity of glassy carbon and molybdenum were measured in the temperature range from 300 to 1100 K.
Proceedings of SPIE - The International Society for Optical Engineering, 2004
Thermal conductivities and boundary thermal resistances of thin films having the thickness of the... more Thermal conductivities and boundary thermal resistances of thin films having the thickness of the order of ten nanometers were measured by using the thermo-reflectance method at room temperature. A thermal simulation of HD DVD-ARW (the next-generation advanced rewritable DVD) media was carried out to clarify the effect of boundary thermal resistance at the interface of those films. The thermal conductivity of thin films greatly depends on film thickness. The result of the thermal simulation depends significantly on whether the boundary thermal resistance is considered or not. Thus it is important to consider the boundary thermal resistances and using thermal properties of thin films to perform more accurate calculation for the phase change recording media. The results of the thermal simulation also suggested that the boundary thermal resistances dominate the thermal diffusion and response of the medium.
Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms, 2013
The thermal and optical properties of the nuclear detector CR-39 were studied in light of the dem... more The thermal and optical properties of the nuclear detector CR-39 were studied in light of the demand for CR-39 and its novel physical properties, as well as its technological implications in many fields. Thermal diffusivity is the most important parameter when this detector is exposed to nuclear radiation and when consequent heat transfer processes influence the photothermal deflection spectroscopy. Thermalinduced effects on the surface of the CR-39 detector were studied using transient heat diffusion simulations. The resulting thermal deformation due to alpha particle irradiation of CR-39 will be presented. Irradiation of CR-39 by a-particles was found to lower the refractive index change with temperature. The temperature distribution was studied numerically by solving the heat diffusion equation to illustrate the effects of a-particle exposure on the CR-39. The thermal diffusivity of exposed CR-39 is the primary subject of this article.
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Papers by Tetsuya Baba