Prediction of the intrinsic thermal conductivity of phonons in dielectric and semiconductor materials based on the density of the lattice vibration energy

2008 ◽  
Vol 34 (10-15) ◽  
pp. 1129-1132 ◽  
Author(s):  
Fan Qunbo ◽  
Zhang Feng ◽  
Wang Fuchi ◽  
Zhang Huiling
Keyword(s):  
Thermal Conductivity ◽  
Lattice Vibration ◽  
Semiconductor Materials ◽  
Vibration Energy ◽  
Intrinsic Thermal Conductivity

Possible Mechanisms for Thermal Conductivity Enhancement in Nanofluids

2006 ◽  
Author(s):  
Amit Gupta ◽  
Xuan Wu ◽  
Ranganathan Kumar
Keyword(s):  
Heat Transfer ◽  
Thermal Conductivity ◽  
Brownian Motion ◽  
Brownian Dynamics ◽  
Lattice Vibration ◽  
Experimental Studies ◽  
High Heat ◽  
Conductivity Enhancement ◽  
High Heat Transfer ◽  
Dynamics Simulations

This study discusses the merits of various physical mechanisms that are responsible for enhancing the heat transfer in nanofluids. Experimental studies have cemented the claim that ‘seeding’ liquids with nanoparticles can increase the thermal conductivity of the nanofluid by up to 40% for metallic and oxide nanoparticles dispersed in a base liquid. Experiments have also shown that the rise in conductivity of the nanofluid is highly dependent on the size and concentration of the nanoparticles. On the theoretical side, traditional models like Maxwell or Hamilton-Crosser models cannot explain this unusually high heat transfer. Several mechanisms have been postulated in the literature such as Brownian motion, thermal diffusion in nanoparticles and thermal interaction of nanoparticles with the surrounding fluid, the formation of an ordered liquid layer on the surface of the nanoparticle and microconvection. This study concentrates on 3 possible mechanisms: Brownian dynamics, microconvection and lattice vibration of nanoparticles in the fluid. By considering two nanofluids, copper particles dispersed in ethylene glycol, and silica in water, it is determined that translational Brownian motion of the nanoparticles, presence of an interparticle potential and the microconvection heat transfer are mechanisms that play only a smaller role in the enhancement of thermal conductivity. On the other hand, the lattice vibrations, determined by molecular dynamics simulations show a great deal of promise in increasing the thermal conductivity by as much as 23%. In a simplistic sense, the lattice vibration can be regarded as a means to simulate the phononic transport from solid to liquid at the interface.

scholarly journals Low intrinsic thermal conductivity of Spark Plasma Sintered dense KNbO3 and NaNbO3 perovskite ceramics

2021 ◽  
Vol 695 ◽  
pp. 178807
Author(s):  
F. Delorme ◽  
C. Chen ◽  
F. Schoenstein ◽  
N. Jaber ◽  
F. Jean ◽  
...  
Keyword(s):  
Thermal Conductivity ◽  
Spark Plasma ◽  
Perovskite Ceramics ◽  
Intrinsic Thermal Conductivity

scholarly journals The Effects of Variable Thermal Conductivity in Semiconductor Materials Photogenerated by a Focused Thermal Shock

Mathematics ◽  
2020 ◽  
Vol 8 (8) ◽  
pp. 1230
Author(s):  
Faris Alzahrani
Keyword(s):  
Thermal Conductivity ◽  
Thermal Shock ◽  
Analytical Solutions ◽  
Transport Process ◽  
Carrier Density ◽  
Coupled Model ◽  
Variable Thermal Conductivity ◽  
Semiconductor Materials ◽  
Elastic Model ◽  
Unit Step

In this work, the generalized photo-thermo-elastic model with variable thermal conductivity is presented to estimates the variations of temperature, the carrier density, the stress and the displacement in a semiconductor material. The effects of variable thermal conductivity under photo-thermal transport process is investigated by using the coupled model of thermoelastic and plasma wave. The surface of medium is loaded by uniform unit step temperature. Easily, the analytical solutions in the domain of Laplace are obtained. By using Laplace transforms with the eigenvalue scheme, the fields studied are obtained analytically and presented graphically.

scholarly journals Electronic, Mechanical and Elastic Anisotropy Properties of X-Diamondyne (X = Si, Ge)

Materials ◽  
2019 ◽  
Vol 12 (21) ◽  
pp. 3589 ◽  
Author(s):  
Qingyang Fan ◽  
Zhongxing Duan ◽  
Yanxing Song ◽  
Wei Zhang ◽  
Qidong Zhang ◽  
...  
Keyword(s):  
Thermal Conductivity ◽  
Shear Modulus ◽  
Young’S Modulus ◽  
Density Functional ◽  
Elastic Anisotropy ◽  
Young's Modulus ◽  
Wide Band ◽  
Band Gaps ◽  
Mechanical Anisotropy ◽  
Semiconductor Materials

The three-dimensional (3D) diamond-like semiconductor materials Si-diamondyne and Ge-diamondyne (also called SiC4 and GeC4) are studied utilizing density functional theory in this work, where the structural, elastic, electronic and mechanical anisotropy properties along with the minimum thermal conductivity are considered. SiC4 and GeC4 are semiconductor materials with direct band gaps and wide band gaps of 5.02 and 5.60 eV, respectively. The Debye temperatures of diamondyne, Si- and Ge-diamondyne are 422, 385 and 242 K, respectively, utilizing the empirical formula of the elastic modulus. Among these, Si-diamondyne has the largest mechanical anisotropy in the shear modulus and Young’s modulus, and Diamond has the smallest mechanical anisotropy in the Young’s modulus and shear modulus. The mechanical anisotropy in the Young’s modulus and shear modulus of Si-diamondyne is more than three times that of diamond as determined by the characterization of the ratio of the maximum value to the minimum value. The minimum thermal conductivity values of Si- and Ge-diamondyne are 0.727 and 0.524 W cm−1 K−1, respectively, and thus, Si- and Ge-diamondyne may be used in the thermoelectric industry.

Width dependent intrinsic thermal conductivity of suspended monolayer graphene

2017 ◽  
Vol 105 ◽  
pp. 76-80 ◽  
Author(s):  
Haidong Wang ◽  
Kosaku Kurata ◽  
Takanobu Fukunaga ◽  
Xing Zhang ◽  
Hiroshi Takamatsu
Keyword(s):  
Thermal Conductivity ◽  
Monolayer Graphene ◽  
Intrinsic Thermal Conductivity

Intrinsic Thermal Conductivity of Starch: A Model-independent Determination

1993 ◽  
Vol 58 (2) ◽  
pp. 413-415 ◽  
Author(s):  
TAKAHARU SAKIYAMA ◽  
SOCKCHONG HAN ◽  
N. SUSAN KINCAL ◽  
TOSHIMASA YANO
Keyword(s):  
Thermal Conductivity ◽  
Independent Determination ◽  
Model Independent ◽  
Intrinsic Thermal Conductivity

Ultra-Low Thermal Conductivity in Nanoscale Layered Oxides

2009 ◽  
Vol 132 (3) ◽  
Author(s):  
J. Alvarez-Quintana ◽  
Ll. Peralba-Garcia ◽  
J. L. Lábár ◽  
J. Rodríguez-Viejo
Keyword(s):  
Thermal Conductivity ◽  
Thermal Barrier Coatings ◽  
Room Temperature ◽  
Thermal Barrier ◽  
Layered Oxides ◽  
Barrier Coatings ◽  
3Ω Method ◽  
Nanometer Thickness ◽  
Intrinsic Thermal Conductivity ◽  
Strong Barrier

The cross-plane thermal conductivity of several nanoscale layered oxides SiO2/Y2O3, SiO2/Cr2O3, and SiO2/Al2O3, synthesized by e-beam evaporation was measured in the range from 30 K to 300 K by the 3ω method. Thermal conductivity attains values around 0.5 W/m K at room temperature in multilayer samples, formed by 20 bilayers of 10 nm SiO2/10 nm Y2O3, and as low as 0.16 W/m K for a single bilayer. The reduction in thermal conductivity is related to the high interface density, which produces a strong barrier to heat transfer rather than to the changes of the intrinsic thermal conductivity due to the nanometer thickness of the layers. We show that the influence of the first few interfaces on the overall thermal resistance is higher than the subsequent ones. Annealing the multilayered samples to 1100°C slightly increases the thermal conductivity due to changes in the microstructure. These results suggest a route to obtain suitable thermal barrier coatings for high temperature applications.

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