A universal constitutive equation between the heat flux vector and the temperature gradient is proposed to cover the fundamental behaviors of diffusion (macroscopic in both space and time), wave (macroscopic in space but microscopic in time), phonon-electron interactions (microscopic in both space and time), and pure phonon scattering The model is generalized from the dual-phase-lag concept accounting for the laging behavior in the high-rate response While the phase lag of the heat flux captures the small-scale response in time, the phase lag of the temperature gradient captures the small-scale response in space The universal form of the energy equation facilitates identifications of the physical parameters governing the transition from one mechanism (such as diffusion or wave) to another (the phonon-electron interaction)

A Unified Field Approach for Heat Conduction From Macro- to Micro-Scales

In the framework of the thermal-spike model the present paper deals with the effect of the electronic stopping power (Se) in metals irradiated by swift heavy ions. Using the strength of the electron-phonon coupling g(z) with the number of valence electrons z as the unique free parameter, the increment of lattice temperature induced by swift-heavy-ion irradiation is calculated. Choosing z=2, the calculated threshold of defect creation by Se for Ti, Zr, Co and Fe is about 11, 27.5, 28 and 41 keV nm-1, in good agreement with experiment. Taking the same z value, the calculation shows that Al, Cu, Nb and Ag are Se insensitive. Moreover, in Fe, the differences in the damage created by U ions of different energies but exhibiting the same value of Se may be interpreted by a velocity effect. Using z=2, other calculations suggest that Be (Se>or=11 keV nm-1), Ga (Se>or=5 keV nm-1) and Ni (Se>or=49 keV nm-1) should be sensitive to Se but Mg should not. These examples put the stress on the effect of the physical parameters governing the electron-phonon coupling constant apart from z determination: the sound velocity linked to the Debye temperature and the lattice thermal conductivity. Furthermore, a simple criterion is proposed in order to predict the Se sensitivity of metals.

/pdf/the-se-sensitivity-of-metals-under-swift-heavy-ion-2g5eyh0z6p.pdf

The Se sensitivity of metals under swift-heavy-ion irradiation: a transient thermal process

The generalized lagging response in small-scale and high-rate heating

This work examines the lagging behavior for heat transport in small-scale and fast-transient processes. The experimental result by Qiu et al. for the femtosecond transient response in gold films and that by Bertman and Sandiford for the temperature pulse traveling through superfluid liquid helium are re-examined with emphasis on the lagging behavior. The model employing the phase-lag concept provides as competent or even better results when describing the special response observed in these experiments.

Experimental support for the lagging behavior in heat propagation

A semiclassical two-temperature model for ultrafast laser heating

Short-pulse laser heating on metals

Femtosecond laser heating of multi-layer metals—I. Analysis

Femtosecond laser heating of multi-layer metals. ii: experiments

Multi-layer metal films such as metallic coatings on metal substrate are important elements in modern engineering applications. Specifically, gold-coated metal mirrors are widely used in high-power laser systems. This work studies microscopic energy deposition and transport processes during short-pulse laser heating of multi-layer metals: the absorption of radiation energy by free electrons and the energy exchange between electrons and the lattice. The results show that multi-layer metals present very different thermal responses from single-layer metals during the heating process. In a gold and chromium multi-layer film, although laser energy is absorbed by free electrons in the top gold coating layer, most of the absorbed energy is converted into lattice energy not in the gold layer but rather in the underlying chromium layer. The underlying chromium layer reduces the lattice-temperature rise of the top gold layer significantly during short-pulse laser heating, suggesting a new way to increase the resistance of mirrors to thermal damage in applications of high-power lasers.

T.Q. Qiu

Papers

Short-pulse laser heating on metals

Femtosecond laser heating of multi-layer metals—I. Analysis

Femtosecond laser heating of multi-layer metals. ii: experiments

Femtosecond laser heating of multi-layer metals--I. analysis