Search query: Thermal conductivity of Ga1−xAlxAs alloys

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abstract: This paper presents the results of our measurement of the room temperature thermal conductivity of the Ga1 xAlxAs alloy system. The study was motivated by our need to characterize the thermal properties of cw heterostructure lasers, in which the heat generated in the optically active layer must flow through a substantial thickness of Ga1 xAlxAs to reach the heat sink. The measurement was made on LPE layers which were separated from their substrates and fashioned into rectangular bars. A steady state heat flow was established in the bars utilizing an argon laser as the heat source, and the conductivity was obtained by measuring the temperature gradient in the bars with thin films of cholesteric liquid crystals. The results indicate that the thermal conductivity of the alloy is well described by an existing theoretical treatment of high temperature lattice thermal conductivity of disordered semiconductor alloys. In the Ga1 xAlxAs system, the increased thermal resistivity of the alloy is shown to be a result.
author_names: Martin A Afromowitz
title: Thermal conductivity of Ga1 xAlxAs alloys
year: 1973

abstract: Some materials such as Cu2 xSe, Cu1.97Ag0.03Se, and SnSe have attracted attention by demonstrating a significant enhancement of their thermoelectric performance, which is associated with a phase transition. This phenomenon, observed in a limited temperature (T) interval, results in sharp changes of the Seebeck coefficient (S) the electrical resistivity (r) and the thermal conductivity (k) which may render the correct evaluation of the dimensionless figure of merit (ZT) difficult. We report the thermoelectric properties of a polycrystalline Cu2 xSe sample which is known to undergo a phase transition near 410 K, containing a mixture of a and b phases at room temperature, as determined by x ray diffraction measurements. We have used a Harman based setup (TEMTE Inc. which assures the direct measurement of ZT at all temperatures, including the phase transition region. This approach ensures that k(T) is determined under steady state conditions at any given temperature, including points arbitrarily close to the transition temperature which cannot be guaranteed by previously used techniques such as laser flash. We have observed a sharp maximum for k(T) near 410 K, similar to the reported specific heat variation, with a ZT peak value of 0.2 at 400 K. The expected gain in ZT related to the phase transition is reduced because the increase in S is counterbalanced by the increase in k(T) Thus, our detailed assessment of the temperature variation of the individual thermoelectric properties accurately evaluates the performance enhancement associated to a structural phase transition and helps to elucidate this complex phenomenon.
author_names: Dmitriy I Vasilevskiy

Mohsen K Keshavarz

J -M Simard

Remo A Masut

Sylvain Turenne

Gerald Jeffrey Snyder
title: Assessing the Thermal Conductivity of Cu2 xSe Alloys Undergoing a Phase Transition via the Simultaneous Measurement of Thermoelectric Parameters by a Harman Based Setup
venue: Journal of Electronic Materials
year: 2018

abstract: In this research, effects of Zn and Cu content on microstructure, mechanical properties, electric and thermal conductivity of the as extruded Al x(Zn+0.5Cu) alloys were investigated. As the content of Zn and Cu increased, the area ratio of Al2Cu intermetallic compounds increased. After homogenization treatment and extrusion process, most of Al2Cu intermetallic compounds was disappeared due to solution in Al matrix of Cu atoms. As the (Zn+0.5Cu) content increased from 1 to 2 wt. the average grain size decreased remarkably from 645 to 227 mm due to the dynamic recrystallization caused by the solute Zn and Cu atoms during the extrusion. With increasing Zn and Cu additions, the thermal conductivity was decreased from 225 (x 1) to 208 (x 2) and 183 W/mK (x 4) due to electric scattering by solute Zn and Cu atoms. The ultimate tensile strength (UTS) of the as extruded Al x(1Zn+0.5Cu) alloys improved remarkably from 77 (x 1) to 142 MPa (x 4) as Zn and Cu content increased, and the elongation increased from 30 to 33% This improvement in the strength resulted from the grain refinement and solid solution strengthening due to the solute Zn and Cu atoms. The Zn and Cu addition in Al alloy played an important role in thermal conductivity and mechanical properties.
author_names: Yong-Ho Kim

H Yoo

Hyeon Taek Son
title: Microstructure, Mechanical Properties, Electric and Thermal Conductivity of the As Extruded Al x(1.0 wt. Zn 0.5 wt. Cu) Alloys (x 1, 2 and 4)
venue: Journal of nanoscience and nanotechnology
year: 2020

abstract: In this study, we investigated the effect of Mg addition (0, 0.5, and 1.0 wt% on the microstructure, mechanical properties, and thermal conductivity of as extruded Al RE alloys. With an increase in the Mg content from 0 to 1.0 wt% the average grain size of the alloys decreased remarkably from 740 to 130 mm and the high angle grain boundary fraction increased from 35 to 54% The addition of Mg resulted in the grain refinement of the Al 1.0RE alloy because of the dynamic recrystallization caused by the solute Mg atoms during the extrusion. With an increase in the Mg content from 0.5 to 1.0 wt% thermal conductivity of the alloy decreased from 231 to 193 W/mK because of the electric scattering caused by the solute Mg atoms. With an increase in the Mg content from 0 to 1.0 wt% the ultimate tensile strength of the alloy increased remarkably from 74 to 120 MPa, while the strain reduced from 44 to 34% This improvement in the strength resulted from the grain refinement and solid solution strengthening due to the solute Mg atoms. The Mg addition amount affected the thermal conductivity and strength of the alloys significantly.
author_names: Yong-Ho Kim

H Yoo

Seong Ho Lee

Gyu-Seok Lee

Hyeon Taek Son
title: Effects of Mg Addition on Microstructure, Mechanical Properties, and Thermal Conductivity of As Extruded Al RE Alloys.
venue: Journal of nanoscience and nanotechnology
year: 2020

abstract: The microstructure and thermal conductivity of four groups of Mg rare earth (RE) binary alloys (Mg Ce, Mg Nd, Mg Y and Mg Gd) in as cast and as solutionized states were systematically studied. Thermal conductivity was measured on a Netzsch LFA457 using laser flash method at room temperature. Results indicated that for as cast alloys, the volume fraction of second phases increased with the increase of alloying elements. After solutionizing treatment, a part or most of second phases were dissolved in a Mg matrix, except for Mg Ce alloys. The thermal conductivity of as cast and as solutionized Mg RE alloys decreased with the increase of concentrations. The thermal conductivity of as solutionized Mg Nd, Mg Y and Mg Gd alloys was lower than that of as cast alloys. Thermal conductivity of as solutionized Mg Ce alloys was higher than that of as cast alloys, because of the elimination of lattice defects and fine dispersed particles during solutionizing treatment. Different RE elements have different influences on the thermal conductivity of Mg alloys in the following order: Ce
author_names: Liping Zhong

Jian Peng

Son Il Sun

Yongjiang Wang

Yun Lu

Fu-sheng Pan
title: Microstructure and Thermal Conductivity of As Cast and As Solutionized Mg Rare Earth Binary Alloys
year: 2017

abstract: This study investigated the microstructure and thermal conductivity of as cast and as extruded binary Mg Mn alloys. The large grains and fine a Mn particles contained in the as cast alloys were observed. After extrusion, the average grain sizes significantly decreased, typical basal fibre texture was generated and high amount of nano particles precipitated from the a Mg matrix. The thermal conductivity of both as cast and as extruded Mg Mn alloys gradually decreased with the increase in Mn concentration. As extruded alloys exhibited lower thermal conductivity than as cast alloys except for the as extruded alloys containing higher Mn concentrations >1.2 wt Mn) Compared with binary as extruded Mg Al and Mg Zn alloys reported in literatures, thermal conductivity of the as extruded Mg Mn alloys was higher when the solute content was greater than 0.5 at.
author_names: Liping Zhong

Jian Peng

Y Sun

Yongjiang Wang

Yun Lu

Fu-sheng Pan
title: Microstructure and thermal conductivity of as cast and as extruded binary Mg Mn alloys
year: 2017

abstract: Abstract In the present work, the thermal conductivities and microstructure of Al x wt% Cu x 1, 3, 5, 15 and 30) and Al y wt% Si y 2, 12.5 and 20) alloys were investigated by using laser flash method, scanning electron microscopy (SEM) and X ray diffraction (XRD) Besides, a CALPHAD (CALculation of PHAse Diagram) approach to evaluate the thermal conductivity of Al Cu Mg Si system was performed. The numerical models for the thermal conductivity of pure elements and stoichiometric phases were described as polynomials, and the coefficients were optimized via PARROT module of Thermal Calc software applied to the experimental data. The thermal conductivity of (Al) based solid solutions was described by using Redlich Kister interaction parameters. For alloys in two phase region, the interface scattering parameter was proposed in the modeling to describe the impediment of interfaces on the heat transfer. Finally, a set of self consistent parameters for the description of thermal conductivity in Al Cu Mg Si system was obtained, and comprehensive comparisons between the calculated and measured thermal conductivities show that the experimental information is satisfactorily accounted for by the present modeling.
author_names: Cong Zhang

Yong Du

Shuhong Liu

Yuling Liu

Bo Sundman
title: Thermal conductivity of Al Cu Mg Si alloys: Experimental measurement and CALPHAD modeling
year: 2016

abstract: In the present work, the effects of Sn, Ca additions on thermal conductivity were investigated in as cast Mg Sn Ca alloys. The measured values of thermal conductivity of Mg 3Sn xCa alloys obviously increased from 85.6 to 126.3 W m 1 K 1 with the increasing Ca from 0 to 1.5 wt and then decreased to 98.3 W m 1 K 1 with the 2.5 wt Ca. In addition, the thermal conductivity of the Mg Sn Ca (Sn/Ca atomic ratio of 1) alloys decreased slightly from 154.2 to 132.1 W m 1 K 1 with the increasing Sn, Ca. Meanwhile, the microstructures of the selected alloys were discussed in detail, suggesting that the solute atoms that caused lattice distortion had greater effect on thermal conductivity compared with the second phases formed in as cast Mg Sn Ca alloys.
author_names: Chunming Wang

Zhen-bao Liu

Sufen Xiao

Yungui Chen
title: Effects of Sn, Ca additions on thermal conductivity of Mg matrix alloys
year: 2016

abstract: This article examines factors affecting the thermal conductivity of aluminium alloys. More specifically, thermal conductivity is measured with the Hot Disk method. The work shows that improvements as high as 50 in thermal conductivity can be achieved through heat treatment of the studied alloys. Optical microscopy and scanning electron microscopy indicate that some elements in solid solution (particularly silicon) precipitate in aluminium grains during annealing. Modifying the microstructure with strontium and sodium increases thermal conductivity slightly, whereas rheocasting and grain refinement treatments do not affect thermal conductivity. AlB treatment improves thermal conductivity especially in low silicon primary aluminium alloys. As cast and heat treated thermal conductivities of the studied alloys are calculated by applying Matthiessen's rule and the Wiedemann Franz law and compared to the measured thermal conductivity.
author_names: Veijo Rauta

Celal Cingi

Juhani Orkas
title: Effect of Annealing and Metallurgical Treatments on Thermal Conductivity of Aluminium Alloys
venue: International Journal of Metalcasting
year: 2016

abstract: Abstract The Wiedemann Franz Law is often used to calculate the thermal conductivity of Fe from experimental measurements of the electrical conductivity. It is shown by measurements of the Seebeck coefficient (S) of solid and liquid Fe at pressures up to 6 GPa and temperatures up to 2100 K that the Sommerfeld value L 0 2.445 x 10 8 W O K 2 of the Lorenz number L represents more than 99% of the electronic component of the thermal conductivity of Fe. Using experimental values of electrical resistivity and thermal conductivity of Fe, L L 0 is shown to vary by as much as 1.22 in the solid state and 1.32 in the liquid state, signifying a non negligible phonon component. An expression for the pressure dependence of L at the melting boundary up to 5 GPa is derived for electron phonon scattering. For Fe Si alloys, L L 0 varies more than for pure Fe and generally increases with increasing Si and state of disorder. New values for the conductive heat flow in a pure Fe core of Mercury are presented.
author_names: Richard A Secco
title: Thermal conductivity and Seebeck coefficient of Fe and Fe Si alloys: Implications for variable Lorenz number
year: 2017