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Ceramic-based thermal barrier coatings are used as heat and wear shields of gas turbine blades. There is a strong need to evaluate the thermal conductivity of coating for thermal design and use. The thermal conductivity of a bulk material is obtained as the product of thermal diffusivity, specific heat capacity, and density above room temperature in many cases. Thermal diffusivity and thermal conductivity are unique for a given material because they are sensitive to the structure of the material. Therefore, it is important to measure them in each sample. However it is difficult to measure the thermal diffusivity and thermal conductivity of coatings because coatings are attached to substrates. In order to evaluate the thermal diffusivity of a coating attached to the substrate, we have examined the laser flash method with the multilayer model on the basis of the response function method. We carried out laser flash measurements in layered samples composed of a CoNiCrAlY bond coating and a 8YSZ top coating by thermal spraying on a Ni-based superalloy substrate. It was found that the procedure using laser flash method with the multilayer model is useful for the thermal diffusivity evaluation of a coating attached to a substrate.

Ceramics-based thermal barrier coatings are used as heat and wear shields of blades of gas turbine. There are strong needs to evaluate thermophysical properties of coatings, such as thermal conductivity, thermal diffusivity and heat capacity of them. Since coatings are attached on substrates, it is not easy to measure these properties separately. In order to evaluate the thermal diffusivity of coating attached on substrate, we have tried to apply the multi-layer model based on the response function method and established a procedure for the measurement by the laser flash method. We verified the procedure by the measurements from room temperature to about 1000 K for two-layer ceramics sample prepared by the doctor blade tape casting method. The thermally sprayed CoNiCrAlY coating on the SUS304 substrate was also used for verification. The thermal diffusivity of coating attached on substrate approximately agreed with that of the single-layer coating removed from substrate. In the case of the ceramics sample, the thermal diffusivity of the coating including the interfacial thermal resistance determined within about 20 % uncertainty. We compared the laser flash measurement signals of the samples prepared by the thermal spraying with variant thickness and found the difference among them. It was found that the procedure has enough resolution to detect the heat shield effect caused by the change with about 200 m in thickness. The result shows that the procedure and analysis were practically effective for the thermal diffusivity estimation of coating attached on the substrate without remove from substrate.

We explored advantages of diverse carbon nanotube forests with tailored structures synthesized by water-assisted chemical vapor deposition (CVD) growth (supergrowth) from engineered catalysts. By controlling the catalyst film thickness, we synthesized carbon nanotube (CNT) forests composed from nanotubes with different size and wall number. With extensive characterizations, many interesting dependencies among CNT forest structures and their properties, which were unknown previously, were found. For example, multiwalled carbon nanotubes (MWNTs) showed superior electronic conductivity while single-walled carbon nanotubes (SWNTs) showed superior thermal diffusivity, and sparse MWNTs achieved lower threshold voltage for field emission than dense SWNTs. These interesting trends highlight the complexity in designing and choosing the optimum CNT forest for use in applications.

Heat flux sensors are focused related to energy conservation. They are convenient tools which can detect direction and amount of heat flux. It is necessary to determine sensitivity of heat flux sensors before they are used. The sensitivity is a relation coefficient between heat flow density and output voltage of sensor. The steady state method is used to determine it in many cases. National Metrology Institute of Japan (NMIJ) of National Institute of Advanced Industrial Science and Technology (AIST) is supplying calibration service for heat flux sensors using by a Guarded Hot Plate (GHP) apparatus. The measurement with GHP apparatus takes long time more than one week although it gives reliable result with small uncertainty. In order to solve this problem, the small apparatus for practical calibration of heat flux sensors was developed according to the steady state method. The apparatus has beautiful steady temperature gradient in the volume of 30 mm × 30 mm x 30 mm. The cover made by expanded polypropylene is effective to decrease heat loss. It takes about 40 minutes to be steady state. Uncertainty of sensitive coefficient estimation using this apparatus was roughly evaluated less than 10% with the coverage factor k = 2.

In order to study the “ $$\frac{1}{8}$$ effect” in different high-Tcoxides from the La-system, muon spin relaxation measurements were applied to the Zn-substituted Bi-2212 system, Bi2Sr2Ca1−xYx(Cu1−yZny)2O8+δ, around the hole concentration p= $$\frac{1}{8}$$ per Cu. It has been revealed that the magnetic correlation between Cu spins is anomalously enhanced in the Zn-substituted samples at $$p \sim \frac{1}{8}$$ per Cu, proving the existence of the “ $$\frac{1}{8}$$ effect" in the Bi-2212 system as well.

Electric resistivity, thermoelectric power and thermal conductivity of a polycrystalline sample of the composite crystal [Ca2CoO3.34]0.614[CoO2], also known as Ca3Co4O9, have been measured below 300 K. Metallic conductivity accompanied by large thermoelectric power has been observed down to 50 K. At 300 K, the sample exhibits a thermoelectric power of S= 133 µV·K-1, resistivity of ?= 15 m?·cm and thermal conductivity of ?= 9.8 mW·K-1·cm-1. The resulting dimensionless figure of merit becomes ZT300= 3.5×10-2, which is comparable to the value reported for a polycrystalline sample of NaCo2O4, indicating that the title compound is a potential candidate for a thermoelectric material.