Electron–Phonon Coupled Heat Transfer and Thermal Response Induced by Femtosecond Laser Heating of Gold

2017 ◽  
Vol 139 (5) ◽  
Author(s):  
Pengfei Ji ◽  
Yuwen Zhang
Keyword(s):  
Heat Transfer ◽  
Femtosecond Laser ◽  
Density Functional ◽  
Energy Transport ◽  
Thermal Response ◽  
Coupling Factor ◽  
Heat Transfer Process ◽  
Thermal Excitation ◽  
Coupled Heat Transfer ◽  
Electron Heat Capacity

Ab initio simulation is one of the most effective theoretical tools to study the electrons evolved heat transfer process. Here, we report the use of finite-temperature density functional theory (DFT) to investigate the electron thermal excitation, electron–phonon coupled heat transfer, and the corresponding thermal response induced by energy deposition of femtosecond laser pulse in gold. The calculated results for cases with different scales of electron excitations demonstrate significant electron temperature dependence of electron heat capacity and electron–phonon coupling factor. Bond hardening of laser-irradiated gold and structural variation from solid to liquid are observed. The obtained results shed light upon the ultrafast microscopic processes of thermal energy transport from electron subsystem to lattice subsystem and serve for an improved interpretation of femtosecond laser–metal interaction.

Study the Heat Transfer Process From Electron-Phonon Nonequilibrium in Thin Gold Film to Glass Substrate Through Transient Thermoreflectance Measurements

2010 ◽  
Author(s):  
Weigang Ma ◽  
Haidong Wang ◽  
Xing Zhang ◽  
Wei Wang
Keyword(s):  
Heat Transfer ◽  
Transfer Process ◽  
Borosilicate Glass ◽  
Glass Substrate ◽  
Physical Vapor Deposition ◽  
Gold Film ◽  
Coupling Factor ◽  
Heat Transfer Process ◽  
Thin Gold Film ◽  
Open Question

How the energy transfers during electron-phonon nonequilibrium in thin metal films is still an open question, and how to measure the intrinsic thermal transport properties of the material under the covering layer is another challenge. In this paper, the heat transfer process from electron-phonon nonequilibrium in thin gold film to borosilicate glass substrate has been studied by resorting to different segments of the transient thermoreflectance signal, which is obtained from the rear-pump front-probe transient thermoreflectance technique. The gold film, which has a thickness of 23.1 nm, is deposited on the borosilicate glass substrate using using a physical vapor deposition (PVD) approach. Within the framework of the two-temperature model (TTM), the electron-phonon (e-ph) coupling factors of the gold film, which reflect the strength of heat flow from hot electrons to cold phonons, are derived from the signal taken after the first several picoseconds with different pump fluences, and the measured value is (1.95–2.05)×1016 W m−3 K−1. The electron-phonon coupling factor does not significantly change in response to the pump pulse fluence variation and exhibits little change compared to the bulk gold value 2.4×1016 W m−3 K−1. Furthermore, the thermal conductivity of the glass substrate is obtained through the thermoreflectance signal between 20 to 140 picoseconds and the value is W m−1 K−1.

scholarly journals CFD STUDIO: AN EDUCATIONAL SOFTWARE FOR CFD ANALYSIS

2003 ◽  
Vol 2 (2) ◽  
Author(s):  
R. A. Pieritz ◽  
R. Mendes ◽  
R. Ferraz ◽  
C. R. Maliska
Keyword(s):  
Heat Transfer ◽  
Finite Volume ◽  
Educational Software ◽  
Transfer Problem ◽  
Heat Transfer Process ◽  
Coupled Heat Transfer ◽  
Fully Implicit ◽  
Finite Volume Approach ◽  
General Aspects ◽  
User Friendly

The main goal of this paper is to demonstrate the general characteristics of the educational user-friendly CFD Studio package for CFD teaching. The package was designed for teaching 2D fluid mechanics and heat transfer process, including conduction, coupled conduction/convection, natural and forced convection, external and internal flows, among other phenomena. The finite volume methodology and its related topics can also be taught using the software. Therefore, general aspects of the three main modules, pre-processor, solver and post-processor are discussed aiming to show the generality of the tool. These modules are integrated in the application by a so-called “numerical problem project” which guide the student through the steps to obtain the solution. To approximate the partial differential equations the finite volume approach is employed using a fully-implicit formulation with the interpolation schemes CDS, UDS and WUDS. Mesh editing and nonorthogonal boundary-fitted mesh generation, using algebraic interpolation and elliptic equations, are important features of the package. Coupled heat transfer problems are handled using the “solid-block” formulation and the pressure-velocity coupling uses the SIMPLE and SIMPLEC methods with non-staggered grids. To demonstrate the capabilities two fluid flow and heat transfer “problem projects” are presented.

scholarly journals CFD STUDIO: AN EDUCATIONAL SOFTWARE FOR CFD ANALYSIS

2003 ◽  
Vol 2 (2) ◽  
pp. 09
Author(s):  
R. A. Pieritz ◽  
R. Mendes ◽  
R. Ferraz ◽  
C. R. Maliska
Keyword(s):  
Heat Transfer ◽  
Finite Volume ◽  
Educational Software ◽  
Transfer Problem ◽  
Heat Transfer Process ◽  
Coupled Heat Transfer ◽  
Fully Implicit ◽  
Finite Volume Approach ◽  
General Aspects ◽  
User Friendly

The main goal of this paper is to demonstrate the general characteristics of the educational user-friendly CFD Studio package for CFD teaching. The package was designed for teaching 2D fluid mechanics and heat transfer process, including conduction, coupled conduction/convection, natural and forced convection, external and internal flows, among other phenomena. The finite volume methodology and its related topics can also be taught using the software. Therefore, general aspects of the three main modules, pre-processor, solver and post-processor are discussed aiming to show the generality of the tool. These modules are integrated in the application by a so-called “numerical problem project” which guide the student through the steps to obtain the solution. To approximate the partial differential equations the finite volume approach is employed using a fully-implicit formulation with the interpolation schemes CDS, UDS and WUDS. Mesh editing and nonorthogonal boundary-fitted mesh generation, using algebraic interpolation and elliptic equations, are important features of the package. Coupled heat transfer problems are handled using the “solid-block” formulation and the pressure-velocity coupling uses the SIMPLE and SIMPLEC methods with non-staggered grids. To demonstrate the capabilities two fluid flow and heat transfer “problem projects” are presented.

scholarly journals Non-equilibrium two-dimensional thermal evolutions in target materials irradiated by femtosecond laser pulse

2013 ◽  
Vol 32 (1) ◽  
pp. 33-39 ◽  
Author(s):  
G. Al-Malkawi ◽  
A. Hassanein
Keyword(s):  
Heat Transfer ◽  
Laser Pulse ◽  
Femtosecond Laser ◽  
Femtosecond Laser Pulse ◽  
Thermal Evolution ◽  
Temporal Distribution ◽  
Spot Size ◽  
Coupling Factor ◽  
Two Dimensional ◽  
Non Equilibrium

AbstractNon-equilibrium heat transfer described by a two-step temperature model was developed to study the thermal evolution through target materials irradiated by femtosecond laser pulse. Two-dimensional heat transfer equations were solved numerically. The temperature dependent thermo-physical properties of the electron and the lattice are considered in the model. The Gaussian spatial and temporal distribution of the heat and temperature of the electron and the lattice is presented. The effect of reflectivity, electron — lattice coupling factor, and the spot size was studied using copper targets.

scholarly journals Dynamic thermal response of bast fiber assemblies

2014 ◽  
Vol 18 (5) ◽  
pp. 1710-1711
Author(s):  
Li-Jun Qu ◽  
Ming-Wei Tian ◽  
Shi-Feng Zhu ◽  
Xiao-Qing Guo ◽  
Ya-Ning Sun ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Performance ◽  
Thermal Response ◽  
Heat Transfer Process ◽  
Cotton Fibers ◽  
Transfer Performance ◽  
Unsteady Heat Transfer ◽  
Bast Fiber ◽  
Dynamic Heat Transfer ◽  
Better Than

Dynamic thermal response of several common bast fiber assemblies was investigated, the dynamic temperature curves of fiber assemblies under high temperature (100?C) were measured and a dynamic heat transfer coefficient was proposed to elucidate the dynamic heat transfer performance during the initial unsteady heat transfer process. The result showed that the dynamic heat transfer performance of bast fibers was better than that of cotton fibers.

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