Determination of global absorptivity and emissivity of some opaque bulk materials using an integrating sphere calorimeter without ports (original) (raw)
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2010 7th International Conference on Electrical Engineering Computing Science and Automatic Control, 2010
Based on the results of an analytical model developed for a heating/cooling process of a film/substrate system, an experimental method to measure the heat capacity (C) of nanometric films by means of electrical micropulses between 100 and 500 s is discussed. The duration of the applied pulse will depend on the time constant of the studied film/substrate system. The corresponding changes of temperature on films during the micropulse application are measured by means of the changes in their electrical resistance. The micropulses were controlled with an electronic circuit designed with a NTP45N06 MOSFET switch, a 2N222A transistor driver, and a NI-USB-6216 card, which are driven with home-made software developed in LabView 2009. An HP6543A power-supply was used for the electrical pulse. Voltage signals measured on films were acquired with a Tektronix digital oscilloscope phosphor DPO-4054 working at 2.5 Giga samples/s. Gold thin films (100 nm, thickness) were deposited on Kapton substrates (125 µm, thickness) for experimentation. The heat capacity (C) of gold films was estimated by measuring, during the micropulse application, the increase of temperature (∆T), the applied electrical power (Q), and the lapsed-time (∆t) of the applied micro-pulses on films through the simple relation C=(Q ∆t)/(T). The mean value of C for the gold film (100 nm) analyzed was 950 ± 30 nJ/K as obtained with a pulse of 250 µs, in good agreement with the values reported in literature.
Thermal and Optical Properties of Materials
The priority actions at LNE affect currently the areas of sustainable development and some other strategic matters. In recent years, the works of the metrology laboratory devoted to thermal and optical properties of materials have been motivated by some key issues: the development of a high accurate calorimeter for measuring the gross calorific value of natural gas, the construction of reference experimental facilities for measuring the transport properties of solid materials and the measurement of spectral transmittivity of liquids for improving the traceability to SI in analytical laboratories. This article is intended to highlight with developments in progress, LNE R&D activities in the field of thermal and optical properties.
Absolute absorptance measurements on copper-based allows at infrared wavelengths
International Journal of Thermophysics, 1989
We report on a method for obtaining absolute optical absorptance of a metallic sample whereby thermal equilibrium is maintained by balancing input from a laser beam with thermoelectric cooling. This method was applied to a series of copperbased alloy samples and was performed at 1.06 and 10.6#m using continuous Nd:YAG and CO2 laser sources, respectively, at near-normal (6 ~ incidence to the sample faces. Independent calibration was provided by passing a known current through a standard resistance heater. Precision of the technique was demonstrated to be within 5% for all samples. Comparison of experimentally derived absorptance values with DC electrical resistivity yielded rank ordering of data for the 20 sample alloys measured.
Photothermal methods for determination of thermal properties of bulk materials and thin films
Central European Journal of Physics, 2009
Information on the thermal properties of materials is very important both in fundamental physical research and in engineering applications. The development of materials with desirable heat transport properties requires methods for their experimental determination. In this paper basic concepts of the measurement of parameters describing the heat transport in solids are discussed. Attention is paid to methods utilizing nonstationary temperature fields, especially to photothermal methods in which the temperature disturbance in the investigated sample is generated through light absorption. Exemplary photothermal measuring techniques, which can be realized using common experimental equipment, are described in detail. It is shown that using these techniques it is possible to determine the thermal diffusivity of bulk transparent samples, opaque and semi-transparent plate-form samples, and the thermal conductivity of thin films deposited on thick substrates. Results of the investigation of thermal diffusivity of the ground in the polar region, which is based on the analysis of the propagation of the thermal wave generated by sun-light, are also presented. Based on chosen examples one can state that photothermal techniques can be used for determination of the thermal properties of very different materials.
Emissivity of aluminium alloy using infrared thermography technique
Materiali in tehnologije, 2018
Experimental determination of the emissivity of aluminum alloy Al 6082 depends on the surface roughness and temperature. The authors conducted an investigation on aluminum workpieces with different degrees of surface roughness during a continuous-cooling process, using the infrared thermography technique (ITT). The results obtained showed that the emissivity of the examined alloy increases with a larger surface roughness and decreases during the cooling process, its value ranging from 0.09 to 0.24. It was concluded that the surface roughness has a greater influence on the increase of the emissivity at higher temperatures, which can be seen in three-dimensional infrared images (3D IR). Multiple-regression analysis confirmed a strong correlation between the examined parameters and the emissivity, and an original multiple-regression model was determined. Keywords: emissivity, aluminium alloy, infrared thermography technique (ITT), three-dimensional infrared images (3D IR), regression analysis Eksperimentalno dolo~anje emisije aluminijeve zlitine Al 6082 glede na hrapavost in temperaturo povr{ine. Avtorji so izvedli raziskavo na aluminijastih obdelovancih z razli~nimi stopnjami hrapavosti povr{ine med postopkom neprekinjenega hlajenja in z uporabo infrarde~e termografije (ITT). Dobljeni rezultati so pokazali, da se emisija preizku{ane zlitine pove~a z ve~jo povr{insko hrapavostjo in se med procesom hlajenja zmanj{a, njena vrednost pa se giblje med 0,09 in 0,24. Pri vi{jih temperaturah ima hrapavost ve~ji vpliv na pove~anje emisij. Kar lahko vidimo na tridimenzionalnih infrarde~ih slikah (3D IR). Ve~kratna regresijska analiza je potrdila mo~no korelacijo med preiskovanimi parametri in emisivnostjo. Dolo~en je bil ve~kratni regresijski model. Klju~ne besede: emisivnost, aluminijeva zlitina, infrarde~a termografija (ITT), tridimenzionalne infrarde~e slike (3D IR), regresijska analiza
PHYSICAL PROPERTIES OF AU AND AL THIN FILMS MEASURED BY RESISTIVE HEATING
Surface Review and Letters, 2005
The electrical resistivity (ρ), resistive thermal coefficient (αr), thermal expansion coefficient (α t ) and stress (σ) of Al and Au thin films deposited by thermal evaporation were measured while films were heated by Joule effect. Electrical resistivity measured by the four-probe technique was simultaneously measured with surface film temperature in real time. Au films show important variations in the αr and ρ properties when thickness ranged from 0.1 µm to 1 µm; contrarily, Al films show insignificant variations in the 0.1 µm to 2 µm thickness range. The role of the surface aluminum oxide on these measurements and the intrinsic stress on films determined with grazing incidence X-rays are discussed.
A low-cost method for measuring the specific heat of aluminium
Physics Education, 2004
One of the standard experiments in basic thermodynamics is the determination of the specific heat of solids and liquids using a water calorimeter. Recently, the measurement of the specific heat of aluminium without the use of a calorimeter has been proposed, where the cooling curves of the systems container/water and container/water/sample are analysed. Here we discuss an application of this method that simplifies Newton's law of cooling. In spite of the use of only low-cost instruments, this application yields consistent results in determining the specific heat of aluminium. P H Y S I C S E D U C A T I O N 39