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Electrical-Optical Hybrid Pulse-Heating Electrical-Optical Hybrid Pulse-Heating is a method of rapidly heating a small plate shaped sample of electroconductive material such as metal and carbon. High temperatures such as 1000 Kelvin (727 ºC) to 3000 Kelvin (2727 ºC) in a matter of seconds are generated by passing a pulsing current through the sample then the front face of the sample is irradiated by a pulsing laser. Five thermodynamic properties including specific heat capacity, electrical resistivity, total emissivity, thermal conductivity, and thermal diffusivity are simultaneously measured during the rapid heating process. By rapidly heating the sample there is a minimum amount of exposure to the high temperatures which greatly reduces the risk of contaminating the sample. Also, the material can be exposed to rapid temperature changes in matter of seconds. The speed at which the sample is heated depends on the supplied electrical energy and the heat emission energy lost by the sample. Theory A thin sample of electrcoductive material is place in series with an electrical circuit containing a capacitor and a standard resister. Pulsing current is passed through the sample and is maintained to keep the sample at a constant high temperature for several hundred milliseconds. At that moment the front face of the sample is exposed to a pulsing laser for another several hundred seconds. With the combination of the pulsing current and pulsing laser the sample at room temperature can reach temperatures as high as 3000 Kelvin (2727 ºC) in a matter of two seconds and then cooled back down to near room temperature again almost instantaneously. The transient temperature is read from the back face of the sample. The following five properties can be obtained from the Electrical-Optical Hybrid Pulse-Heating: Specific heat capacity is the measurement of energy needed to raise the temperature of a 1kg of a given material by 1 Kelvin (1 º). When the temperature is being increased at fast rates, the applied energy is much larger than the energy being lost by the sample. The excess amount of heat energy depends on the product of the temperature rise and the specific heat capacity. Since the temperature rise is known and the excess amount of heat energy is monitored, the specific heat capacity of the material can be calculated. Electrical resistivity is represented by multiplying the electrical resistance of a material by the surface area of that material by its length. The electrical resistivity is calculated by knowing the geometry of the sample and measuring the current and voltage from the applied electrical energy. Total emissivity is the comparison of the emissivity of a material and a true black body surface. Total emissivity is measured from the applied electrical energy. Thermal conductivity is represented by the product of specific capacity, thermal diffusivity, and density of the material. Thermal conductivity is measured from the given specific capacity and density of the material and the calculated thermal diffusivity. Thermal diffusivity is a measurement of the capacity to transfer temperature waves. As heat is applied to the front surface of a sample containing two different materials with the same thickness, thermal diffusivity is represented by the rate at which the temperature is changing on the back surface of a sample. Applications Research and development of electrcoductive materials in the aerospace, nuclear, and steam turbine industries is a critical field and usually has little to no room for failure of the final product. The materials found in these industries are exposed to rapid and extreme temperature changes in hostile environments. In the aerospace industries extreme rapid temperature changes are found in the combustion chambers of jet engines, exhaust nozzles of rockets and turbines, and vessels in outer space as well as returning vessels into our atmosphere. In the nuclear industries the nuclear reactors face extreme temperatures and materials being used are very vital to keep the nuclear reactivity contained at all times. In the turbine industries steams turbines face rapid heating and cooling conditions as well. Research and development of new materials for these applications are always being sought out; the problem is testing the new materials accurately and with minimal cost. The Electrical-Optical Hybrid Pulse-Heating Method uses a small thin sample of a given material and is capable of very fast and accurate parameters of the thermal properties of that material. Resources Hiromichi Watanabe. Subsecond Multi-Property Measurement for Thermal Design. Metrology Institute of Japan. AIST TODAY Vol.6, No. 9 (2006).

ULAVC-RIKO. ULVAC-RIKO Announces RMP-1 Rapid Multi Property Measurement System. The National Institute of Advanced Industrial Science and Technology (AIST). http://www.ulvac.co.jp/eng/information/news/2009/20090323.html

Satoaki Ikeuchi, Kenji Shimada, Yoshikazu Ishii and Hiromichi Watanabe. The Rapid Multi-Property Measurement System. ULVAC Technical Journal No. 71E 2009.