Measurement of Thermal Conductivity and Thermal Diffusivity of Solid Materials Using a Novel Stamp Sensor: A Feasibility Study with Numerical Analysis

Abstract

Contact-probe methods have been developed to measure thermal transport properties of solid materials. Although they have an advantage of being used for non-destructive in-situ measurement, it has a substantial problem that the measured results are influenced by thermal contact between the probe and the specimen. To overcome this problem, we proposed a new technique using a gel to eliminate the contact resistance. A unique feature of the method is that a thin film heater is fabricated on a substrate at the bottom of a shallow cavity, which provides a gel layer of the thickness that is almost the same as the cavity depth. When we use this sensor, we press it against a surface of a specimen with a gel in between. We named it "stamp sensor" from its supposed use and appearance. The thermal conductivity and the thermal diffusivity of a specimen and the thickness of the gel layer are determined simultaneously by comparing the measured temperature rise of the sensor with that obtained by numerical analysis. The objective of the present paper is to demonstrate the feasibility of the method by virtual experiments. The process to determine the thermal conductivity and the thermal diffusivity was examined using simulated experimental data that have been generated from the temperature rise of the sensor obtained by numerical analyses with given artificial scattering. Effects of the scattering of the data, the heating power and the heating time on the measurement error were also discussed.

Contact measurement of thermal conductivity and thermal diffusivity of solid materials: Experimental validation of feasibility with a prototype sensor

“…However, significantly larger error was found in thermal diffusivity for acrylic resin and SUS304; the difference from the literature value was 23.9% for acrylic resin and 35.9% for SUS304, while it was only 0.9% for agar gel and 1.5% for machinable ceramic. This resulted from the fact that the temperature rise is less sensitive to the thermal diffusivity than the thermal conductivity, which has been demonstrated in the discussion with theoretical analysis [23].…”

“…The measured voltage was recorded by a data acquisition system that was controlled by a computer. The heating rate was determined from our previous study that examined the measurement accuracy using numerical simulations [23]. The sensor was heated up to ~5K in the temperature rise within 5 s for all the materials.…”

“…Hence to develop a convenient method for measuring solids including soft materials, we have proposed a new contact method using a 'stamp-type sensor' [23]. The thermal transport properties are measured by pressing a small thin film sensor that was fabricated on a surface of a thin plate.…”

“…In addition, a shallow cavity with given dimensions has been prepared around the sensor for the gel. The feasibility of the method to determine the thermal conductivity and the thermal diffusivity has been checked using virtual experimental data that have been generated by adding an artificial scattering to a theoretical temperature change of the sensor [23]. The results indicated that the thermal conductivity was determined within the error less than ~2 % and the thermal diffusivity within ~5 % error.…”

The design of high-temperature thermal conductivity measurements apparatus for thin sample size

“…Also, this method has a limitation in high thermal conductivity material and high-temperature measurements [9]. Other proposed thermal conductivity measurements have proposed using point probe method [10] and stamp sensor method [11,12,13] that has the capability in in-situ measurements, but this method also has a limitation in high-temperature measurements. The common method in high-temperature thermal conductivity measurements is axial heat flow based on the standard of ASTM E1225-99 [14] which use a bored thermocouple in the specimen [15,16].…”