Application of the laser pulse method of measuring thermal diffusivity to thin alumina and silicon samples in a wide temperature range

Milošević, Nenad

doi:10.2298/tsci1002417m

Cited by 7 publications

(3 citation statements)

References 8 publications

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“…Diffusive transfer is much slower due to interaction of heat with the medium ( Section 5 ). Ballistic transfer is thus visually discernable from diffusion in the temperature–time curves, especially when T (and thus flux) is high ( Figure 1 e, see also [ 31 , 32 , 33 , 34 , 35 ]). The ballistic increase occurs over a small time interval because the pulse has finite duration.…”

Section: The Methods Of Laser Flash Analysismentioning

confidence: 97%

Dependence of Heat Transport in Solids on Length-Scale, Pressure, and Temperature: Implications for Mechanisms and Thermodynamics

Hofmeister

2021

Materials

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Accurate laser-flash measurements of thermal diffusivity (D) of diverse bulk solids at moderate temperature (T), with thickness L of ~0.03 to 10 mm, reveal that D(T) = D∞(T)[1 − exp(−bL)]. When L is several mm, D∞(T) = FT−G + HT, where F is constant, G is ~1 or 0, and H (for insulators) is ~0.001. The attenuation parameter b = 6.19D∞−0.477 at 298 K for electrical insulators, elements, and alloys. Dimensional analysis confirms that D → 0 as L → 0, which is consistent with heat diffusion, requiring a medium. Thermal conductivity (κ) behaves similarly, being proportional to D. Attenuation describing heat conduction signifies that light is the diffusing entity in solids. A radiative transfer model with 1 free parameter that represents a simplified absorption coefficient describes the complex form for κ(T) of solids, including its strong peak at cryogenic temperatures. Three parameters describe κ with a secondary peak and/or a high-T increase. The strong length dependence and experimental difficulties in diamond anvil studies have yielded problematic transport properties. Reliable low-pressure data on diverse thick samples reveal a new thermodynamic formula for specific heat (∂ln(cP)/∂P = −linear compressibility), which leads to ∂ln(κ)/∂P = linear compressibility + ∂lnα/∂P, where α is thermal expansivity. These formulae support that heat conduction in solids equals diffusion of light down the thermal gradient, since changing P alters the space occupied by matter, but not by light.

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Section: The Methods Of Laser Flash Analysismentioning

confidence: 97%

Dependence of Heat Transport in Solids on Length-Scale, Pressure, and Temperature: Implications for Mechanisms and Thermodynamics

Hofmeister

2021

Materials

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“…Real-time monitoring of laser processing is important for optimizing processes and avoiding potential sources of damage. The monitoring process can be performed automatically by CCD cameras, infrared (IR) cameras, spectroscopy (LIBS, LIF), or other techniques [10][11][12][13][14].…”

Section: Introductionmentioning

confidence: 99%

Monitoring of a ceramic surface temperature field induced by pulsed Nd:YAG laser

et al. 2021

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Temperature distribution induced by laser radiation is a very important parameter for an efficient and safe application of lasers in different ceramic processing techniques. This paper presents the results of an infrared thermography (IRT) application for monitoring temperature distribution on a ceramic surface during Nd: YAG laser irradiation with different fluences and 8ns pulse duration. FLIR, E40 and SC7200 IR cameras were used with the aim of recording the maximum temperature in the irradiated zones. It was expected that IRT could give some information related to the heat affected zone and possible damage to the base material; however, the results have shown that IR cameras, even those with high performance such as SC7200, cannot record the maximum temperature value at the moment of laser operation, but only the average temperature of the bulk sample material after laser pulses. The results of the numerical simulation have confirmed the value of the thermographic measurements. The microstructure and micromorphology of the ceramic surface before and after the laser treatment were analysed by optical and scanning electron microscopy as well as by examining the roughness of the irradiated and non-irradiated surfaces, while the micromechanical changes were analysed by comparing the micro-hardness of the irradiated and non-exposed surfaces.

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“…The constants are calculated according to the shock-wave experiments, determined from isentropic curves of unloading of porous samples, or are found from the experimental data in a wide area of the phase diagram from thermodynamic relations. It is worth mentioning the modern models with fewer constants as the initial data, but still there are too many of them to solve real engineering problems [4][5][6][7][8][9][10]. With this approach, the search for constants for the equation of state becomes a separate, time-consuming research task.…”

Section: Introductionmentioning

confidence: 99%

Melting behind the front of the shock wave

Kraus

Shabalin

2019

THERM SCI

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A simple caloric model of the equation of state is proposed to describe thermodynamic properties of solid materials with phase transitions with the minimum number of parameters as initial data. Thermodynamic characteristics are calculated in the wide range of densities and pressures. The equation of state of the solid phase was modified by introducing configurational entropy, which made it possible to describe a liquid medium by the same functional dependence, but with its initial parameters. This allowed us not only to construct the equation of state for the liquid, but also to determine the dependence of the melting point on pressure as the boundary between the phases with the corresponding state. It is shown that the melting process is practically not noticeable on the shock adiabat in the pressurevolume plane; however, sharp adiabatic breaks are observed in the temperaturepressure plane. The calculated position of the melting curve agrees with the experimental data found; although this does not fully justify the conclusion about the accuracy of the calculation of the liquid phase adiabat, but fully confirms the qualitative picture.

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Application of the laser pulse method of measuring thermal diffusivity to thin alumina and silicon samples in a wide temperature range

Cited by 7 publications

References 8 publications

Dependence of Heat Transport in Solids on Length-Scale, Pressure, and Temperature: Implications for Mechanisms and Thermodynamics

Dependence of Heat Transport in Solids on Length-Scale, Pressure, and Temperature: Implications for Mechanisms and Thermodynamics

Monitoring of a ceramic surface temperature field induced by pulsed Nd:YAG laser

Melting behind the front of the shock wave

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