Improved Method for Measuring Thermal Diffusivity of Bulk Samples and Films. (original) (raw)
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2015
A new measurement technique based on the transient hot strip technique has recently been developed for studying anisotropic thermal transport properties of thin crystalline films. A micrometer-sized hot strip sensor is evaporated on the surface of the crystalline film sample, which has been deposited on a substrate wafer of limited thickness. From a pulsed transient recording, using sub-millisecond square-shaped pulses, a thermal probing depth that is less than the film thickness is assured. In the ongoing work of verifying the technique, we show results from measurements on z-cut crystal quartz and fused silica, using thermal probing depths of only 30 μm, which closely conform to bulk values found in the literature.
Measurement of the thermal diffusivity by the laser-flash method with repeated pulses
High Temperatures-High Pressures, 2001
The paper deals with the measurement of the thermal diffusivity using the laser flash method with repeated pulses. The flash method with repeated pulses was proposed as an extension of the classical 'one pulse' laser flash method aimed to overcome particular experimental difficulties associated with the measurement of some types of insulators, temperature sensitive materials and large-grain heterogeneous materials. Unlike the other approaches, based on reducing the energy intensity and simultaneously increasing the exposure time (the flash method with extended pulse), or substituting step (continuous) heating for pulse irradiation (the step heating method), respectively, in the flash method with repeated pulses the pulse energy consists of several consecutive pulses periodically applied to the sample front face. The thermal diffusivity is calculated from the resulting temperature rise of the rear face, in a similar way to the standard laser flash method. The paper presents the mathematical basis of the flash method with repeated instantaneous pulses. The simple adiabatic mathematical model as well as the more realistic non-ideal theory that considers heat loss from the sample is reviewed here. The built experimental apparatus that is regularly used for serial measurement of the thermal diffusivity in the Austrian Research Centers (ARC) is described here in details. Results of the thermal diffusivity measurements of CrNi austenitic steel are presented and compared. Nomenclature a-thermal diffusivity [m 2 ⋅ s-1 ];
Thermal-Diffusivity Measurement in Low Thermal-Conductivity Solids by a Transient Heating Method
International Journal of Thermophysics, 2012
A simple method for thermal-diffusivity measurement in low thermalconductivity solids is proposed on a basis of the analytical solution of the heat diffusion equation for a solid plate with uniform continuous heating at one of its surfaces. The method involves combined measurements of the temperature evolution at both the front (illuminated) and rear surfaces of the sample in both the thermally thin and thick regimes. The principal advantage of the method is its independence on a knowledge of the convection and radiation heat loss coefficient, and hence, the non-necessity of performing measurements in blackbody similar samples under vacuum conditions. If these conditions are achieved, the thermal conductivity and specific (volume) heat capacity could also be achieved.
Thermal conductivity and interfacial thermal conductance play crucial roles in the design of engineering systems where temperature and thermal stress are of concerns. To date, a variety of measurement techniques are available for both bulk and thin film solid-state materials with a broad temperature range. For thermal characterization of bulk material, the steady-state method, transient hot-wire method, laser flash diffusivity method, and transient plane source method are most used. For thin film measurement, the 3ω method and the transient thermoreflectance technique including both time-domain and frequency-domain analysis are widely employed. This work reviews several most commonly used measurement techniques. In general, it is a very challenging task to determine thermal conductivity and interfacial thermal conductance with less than 5% error. Selecting a specific measurement technique to characterize thermal properties needs to be based on: 1) knowledge on the sample whose thermophysical properties is to be determined, including the sample geometry and size, and the material preparation method; 2) understanding of fundamentals and procedures of the testing technique, for example, some techniques are limited to samples with specific geometries and some are limited to a specific range of thermophysical properties; 3) understanding of the potential error sources which might affect the final results, for example, the convection and radiation heat losses.
Cross-comparison of thermal diffusivity measurements by thermal methods
Infrared Physics & Technology, 2002
Thermal diffusivity is measured applying three techniques: (a) thermal wave generation by thermoelectric device; (b) non-adiabatic flash method with correction for non-ideal Dirac pulse by deconvolution; (c) photothermal deflection. They are applied on a sample of AISI 304. Results are compared with those obtained by the standard laser flash method. Ó 2002 Published by Elsevier Science B.V.
International Journal of Thermophysics, 2005
The thermal diffusivity of thin metal films has been measured by combining a fast infrared radiation thermometer with a mercury cadmium telluride (MCT) detector and a CO 2 laser modulated at a radio frequency up to 2 MHz. The laser output beam modulated by an acousto-optic modulator (AOM) is directed to the front surface of the blackened copper thin film (10 µm thick, 9.5 mm in diameter). The thermal radiation from the back surface of the sample is detected. From the observed phase delay in the detected signal of 0.68 radian to the input laser beam, the thermal diffusivity is determined to be 1.11 × 10 −4 m 2 •s −1 , which agrees well with the value of 0.99 × 10 −4 m 2 •s −1 calculated from literature results. The method is generally applicable for measurements of thermal properties of nano/micro materials.
2002
The paper deals with the measurement of the thermal diffusivity using the laser flash method with repeated pulses. The flash method with repeated pulses was proposed as an extension of the classical 'one pulse' laser flash method aimed to overcome particular experimental difficulties associated with the measurement of some types of insulators, temperature sensitive materials and large-grain heterogeneous materials. Unlike the other approaches, based on reducing the energy intensity and simultaneously increasing the exposure time (the flash method with extended pulse), or substituting step (continuous) heating for pulse irradiation (the step heating method), respectively, in the flash method with repeated pulses the pulse energy consists of several consecutive pulses periodically applied to the sample front face. The thermal diffusivity is calculated from the resulting temperature rise of the rear face, in a similar way to the standard laser flash method. The paper presents the mathematical basis of the flash method with repeated instantaneous pulses. The simple adiabatic mathematical model as well as the more realistic non-ideal theory that considers heat loss from the sample is reviewed here. The built experimental apparatus that is regularly used for serial measurement of the thermal diffusivity in the Austrian Research Centers (ARC) is described here in details. Results of the thermal diffusivity measurements of CrNi austenitic steel are presented and compared. Nomenclature a-thermal diffusivity [m 2 ⋅ s-1 ];
Microelectronic Engineering, 2007
We have measured the temperature dependence of thermal conductivity up to several hundred degrees for memory device materials. In the measurement of thermal conductivity, we used a novel technique of nanosecond thermoreflectance measurement spectroscopy (Nano-TheMS) developed by Baba et al. The main advantage of this technique is that it can measure thin films of nanometer-order by easy sample preparation. Using this system with a heat stage, the measurement of thermal conductivities of Ge 2 Sb 2 Te 5 and ZnS-SiO 2 , which were selected as representative materials of memory devices, from room temperature to 400 or 500°C was carried out. All thermal conductivities increased with higher temperature. Using their temperature dependence, optical disk thermal simulation was carried out, and the results were compared with conventional calculated results without the dependence. It was found that the largest difference at maximum temperature was approximately 80°C. The temperature dependence of thermal properties is essential for realistic temperature simulation.
Construction of a Novel Method of Measuring Thermal Conductivity for Nanostructures
Makara Journal of Technology, 2015
With the aim of characterizing the thermal conduction in a nanometer-scaled materials, we have constructed a novel method on the basis of an ac calorimetric method. In this method, periodic sample heating is performed by light irradiation and the corresponding periodic temperature is detected by infrared irradiative thermometer. This makes us measure the thermal diffusivity out of contact with the objective sample. In the present study, we confirm to measure the thermal diffusivity of bulk Si and Cu by this non-contact method with halogen-lamp irradiation. In determining the thermal diffusivity from the relationship between distance deviation and delay time, the simplest wave equation is used, and the obtained values of thermal diffusivity for Si and Cu are close to those reported. Therefore, this non-contact method is useful for evaluating the thermal conduction and applicable for nanometer-scaled materials by improving local heating and local detecting systems. Abstrak Penyusunan Metode Baru untuk Mengukur Konduktivitas Termal untuk Strukturnano. Dengan tujuan untuk menggambarkan proses konduksi termal pada bahan-bahan berskala nanometer, kami telah menyusun sebuah metode baru yang didasarkan pada metode kalorimetrik ac. Di dalam metode ini, pemanasan sampel secara periodik dilaksanakan dengan iradiasi sinar, dan suhu periodik yang sejajar dideteksi dengan termometer iradiatif infra merah. Dengan demikian, kami mengukur difusivitas termal tanpa melibatkan kontak dengan sampel objektif. Di dalam kajian ini, kami memutuskan untuk mengukur difusivitas termal dari limbak Si dan Cu menggunakan metode tanpa kontak ini dengan iradiasi lampu halogen. Untuk menentukan difusivitas termal dari hubungan antara deviasi jarak dan waktu tunda, kami menggunakan persamaan gelombang yang paling sederhana, dan angka-angka difusivitas termal dari Si dan Cu yang diperoleh ternyata hampir sama dengan angka-angka yang telah dilaporkan. Oleh karena itu, metode tanpa kontak ini berguna untuk mengevaluasi konduksi termal dan dapat diterapkan untuk bahan-bahan berskala nanometer dengan memperbaiki pemanasan lokal dan sistem-sistem pendeteksian lokal.