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. The laser flash method is one of the most popular thermal diffusivity measurement methods above room temperature for solid materials. The surface of the plate shape specimen is heated by the pulsed laser-beam, then the time variation of the temperature of the rear surface is observed by the infrared radiometer. The laser flash method is non-contact and short time measurement. In general, the thermal diffusivity of solids that are dense, homogeneous and stable, are measured by this method. It is easy to measure thermal diffusivity of a specimen which shows heat diffusion time about 1 ms to 1 s consistent with the specimen thickness of about 1 mm to 5 mm. On the other hand, this method can be applied to measure the specific heat capacity of the solids. And it is also used to estimate the thermal diffusivity of an unknown layer in the layered materials. In order to evaluate the thermal diffusivity of the coating attached on substrate, we have developed a measurement procedure using the laser flash method. The multi-layer model based on the response function method was applied to calculate the thermal diffusivity of the coating attached on substrate from the temperature history curve observed for the two-layer sample. We have verified applicability of the laser flash measurement with the multi-layer model using the measured results and the simulation. It was found that the laser flash measurement for the layered sample using the multi-layer model was effective to estimate the thermal diffusivity of an unknown layer in the sample. We have also developed the two-layer ceramics samples as the reference materials for this procedure.
A rapid-response heat flux gauge has been developed. Platinum resistance bulb of 0.4×0.4 mm area made by vacuum vapor deposition is manufactured by laser trimming on an alumina cylinder of 1.6 mm diameter and 2 mm length. Calibration test for a newly developed heat flux gauge has been conducted and fixed the temperature coefficient and the value of √ρCλ. The response of the heat flux gauge appears to be less than tens of micro seconds and the accuracy is ±10%. The heat flux distribution in the tile gap of an un-manned space shuttle has been measured with high-accuracy and wide range.
It is known that among numerous factors, industrial turbine Inlet gas Temperature (TIT, hereafter) has greatest influence on thermal efficiency of industrial gas turbine. In order to achieve higher thermal efficiency, TIT has already reached as high as 1500°C, which has been realized owing to improvement and development of cooling configuration and materials for hot parts. On the other hand, to operate gas turbines soundly, it is necessary to evaluate metal temperature of hot parts precisely. So, metal temperature evaluation methods of Ni base superalloy were investigated and developed based on coarsening phenomenon of γ' phase and carbide particles.
Direct methanol fuel cell (DMFC) is promising as new portable power source in various electronics devises. However, the performance of DMFC decreases by many problems which the factor of the structure and material effects each species concentration in the electrode catalyst layer. The anode reaction in DMFC products carbon dioxide, and CO2 bubbles generate in anode electrode. Diffusion layer in DMFC electrode is made carbon paper. The CO2 bubbles resulted in gas slugs blocking the pores in carbon paper. The CO2 bubble is affected by structure and surface characteristics in the diffusion layer. The behavior of bubble is analyzed some structure. We showed the relationship between bubble effect and contact angle of carbon fiber. And also, the model results indicate that the contact angle can improve the cell performance.