Temperature Dependence of Thermal Conductivity of Electronic Ceramics by an Improved Flash Diffusivity Technique

1989 ◽  
Vol 167 ◽  
Author(s):  
R. C. Enck ◽  
R. D. Harris
Keyword(s):  
Thermal Conductivity ◽  
Room Temperature ◽  
Ceramic Materials ◽  
Laser Flash ◽  
Flow Measurements ◽  
Electronic Ceramics ◽  
Temperature Dependences ◽  
Commercial Sources ◽  
Materials Used ◽  
Flash Diffusivity

AbstractThe thermal conductivity of ceramic materials used for IC substrates and packages has increased in importance as chip sizes have decreased and heat loads have risen. AIN which has a room temperature (RT) thermal conductivity (λ) greater than 200 W/m·K and BeO with λ(RT) ∼260 W/m·K are the major candidates for applications demanding high conductivity. Conflicting reports of the temperature dependences of λ for these materials over the range of interest for packaging use (≤200°C) have been published, with some reports suggesting a crossover in λ. These reported differences may be due to the reported problems in measuring λ in AIN using the flash diffusivity method. For the present experiments, we have used a new long wavelength laser flash diffusivity system which has been shown to determine thermal diffusivity to better than ± 3% for AIN with sample thicknesses ranging from 0.3 mm to 5 mm. No absorbinq coatings are required and no correction factors are needed to fit the data to theory. We report λ from room temperature to 400°C for AIN from a number of commercial sources, and for BeO and SiC. At room temperature, BeO has the highest thermal conductivity, but as the temperature is raised, the values for BeO and AIN approach one another, with crossover observed at about 350°C for the highest conductivity AIN sample studied. Recent steady state heat flow measurements agree with our thermal conductivity values rather than with previous literature values.

scholarly journals Determination of the effective thermal conductivity of solid fuels by the laser flash method

2014 ◽  
Vol 35 (3) ◽  
pp. 3-16 ◽  
Author(s):  
Monika Kosowska-Golachowska ◽  
Władysław Gajewski ◽  
Tomasz Musiał
Keyword(s):  
Thermal Conductivity ◽  
Room Temperature ◽  
Laser Flash ◽  
Physical Structure ◽  
Solid Fuels ◽  
Flash Method ◽  
Hard Coal ◽  
Coal Rank ◽  
Dominant Effect

Abstract In this study, a new laser flash system was proposed for the determination of the thermal conductivity of brown coal, hard coal and anthracite. The main objective of the investigation was to determine the effect of coal rank, composition, physical structure and temperature on thermal conductivity. The solid fuels tested were medium conductors of heat whose determined thermal conductivities were in the range of 0.09 to 0.23W/(mK) at room temperature. The thermal conductivity of the solid fuels tested typically increased with the rank of coal and the measurement temperature. The results of this study show that the physical structure of solid fuels and temperature have a dominant effect on the fuels’ thermal conductivity.

Microstructure and Thermal Conductivity of Porous Al2O3-ZrO2 Ceramics

2015 ◽  
Vol 820 ◽  
pp. 268-273
Author(s):  
Tiago Delbrücke ◽  
Rogério A. Gouvêa ◽  
Cristiane W. Raubach ◽  
Elson Longo ◽  
Vânia Caldas Sousa ◽  
...  
Keyword(s):  
Thermal Conductivity ◽  
New Technologies ◽  
Porous Ceramic ◽  
Ceramic Materials ◽  
Laser Flash ◽  
Sem Analysis ◽  
Pressure Vessels ◽  
Flash Method ◽  
Rocket Engines ◽  
Ceramic Fibers

The improvement on the development of porous ceramic materials has leaded to new technologies in thermal insulation, for example, composite materials for better performance of pressure vessels in rocket engines. Within this context, the present work aims to evaluate the ability of a refractory ceramic base alumina/zirconia through the processes of co-precipitation and replica method in an organic fiber template. The green body was burnt-out and sintered at 1200-1600°C to obtain the continuous porous ceramic fibers. In the FEG-SEM analysis, an interconnected porous structure with small grains was observed. The crystalline phases were determined by X-ray diffraction and compared to micro-Raman results regarding the crystalline structure confirms that there present in the material zirconia is composed of more than one phase. Porosity was calculated through a mercury porosimeter as 77.9%, and the Laser Flash method gave a thermal conductivity value of 1.61 K W.m−1.K−1 for the Al2O3-ZrO2 fibers.

Effect of SiC Whiskers on the Microstructure and Thermal Conductivity of Carbon Foam

2018 ◽  
Vol 917 ◽  
pp. 106-111 ◽  
Author(s):  
Sheng Jie Yu ◽  
Zhao Feng Chen ◽  
Yang Wang
Keyword(s):  
Thermal Conductivity ◽  
Random Distribution ◽  
Chemical Vapor ◽  
Carbon Foam ◽  
Laser Flash ◽  
Homogeneous Distribution ◽  
Silicon Carbide Whiskers ◽  
Sic Whiskers ◽  
Flash Diffusivity ◽  
Insulation Performance

This paper describes the modification of ultralight flexible carbon foam by chemical vapor deposition (CVD) of silicon carbide whiskers (SiCw). The effect of SiC whiskers on the microstructure and the thermal conductivity of carbon foam were investigated by scanning electron microscopy (SEM) and laser flash diffusivity method in a Netzsch LFA427. The results show that the macro-pores (~30 μm) of the carbon foam were divided by the random distribution of SiC whiskers. The diameter of SiC whiskers decreased with decreasing catalyst concentration which resulted in the improved microstructure with a smaller pore diameter (4~6 μm) and a more homogeneous distribution of the pores. The carbon foam reinforced by SiCw exhibits better insulation performance than the pristine carbon foam when the temperature exceeds 200°C.

scholarly journals Thermal conductivity of titanium slags

2019 ◽  
Vol 116 (6) ◽  
pp. 635 ◽  
Author(s):  
Juhani Heimo ◽  
Ari Jokilaakso ◽  
Marko Kekkonen ◽  
Merete Tangstad ◽  
Anne Støre
Keyword(s):  
Thermal Conductivity ◽  
Room Temperature ◽  
Laser Flash ◽  
Analysis Method ◽  
Additional Experiment ◽  
Titanium Slag ◽  
Freeze Lining ◽  
Laser Flash Analysis ◽  
Increasing Temperature ◽  
Additional Sample

In ilmenite smelting furnaces, a freeze lining of solidified slag is used to protect the furnace refractories against the aggressive titanium slag. Freeze lining thickness cannot be measured directly due to harshness of conditions inside the process, thus process modelling is required. Several parameters influence the thickness of the freeze-lining, one of them being thermal conductivity of the frozen slag. However, there is a lack of thermal conductivity values for high titanium slags −especially as a function of temperature. In this study, thermal conductivity of three titanium slag samples and an additional sample of freeze-lining was measured from room temperature to 1100/1400 °C with the laser flash analysis method. In addition, thermal expansion and microstructures of the samples were studied to provide an extensive understanding of how microstructure will affect thermal conductivity. The thermal conductivity of the slag samples was found to increase from 1.2 to a maximum of 2.4 W/(m K) when increasing temperature from room temperature to 1100 °C. An additional experiment at 1400 °C showed that the thermal conductivity increased further as the temperature increased. The freeze-lining sample behaves differently, with conductivity being the highest at room temperature, 2.2 W/(m K).

Pseudo-Superlattices of Bi2Te3 Topological Insulator Films with Enhanced Thermoelectric Performance

2011 ◽  
Vol 1344 ◽  
Author(s):  
V. Goyal ◽  
D Teweldebrhan ◽  
A.A. Balandin
Keyword(s):  
Thin Films ◽  
Thermal Conductivity ◽  
Topological Insulator ◽  
Figure Of Merit ◽  
Room Temperature ◽  
Laser Flash ◽  
Thermoelectric Efficiency ◽  
Thermoelectric Figure ◽  
Surface Transport ◽  
Film Thinning

ABSTRACTIt was recently suggested theoretically that atomically thin films of Bi2Te3 topological insulators have strongly enhanced thermoelectric figure of merit. We used the “graphene-like” exfoliation process to obtain Bi2Te3 thin films. The films were stacked and subjected to thermal treatment to fabricate pseudo-superlattices of single crystal Bi2Te3 films. Thermal conductivity of these structures was measured by the “hot disk” and “laser flash” techniques. The room temperature in-plane and cross-plane thermal conductivity of the stacks decreased by a factor of ∼2.4 and 3.5 respectively as compared to that of bulk. The strong decrease of thermal conductivity with preserved electrical properties translates to ∼140-250% increase in the thermoelectric figure if merit. It is expected that the film thinning to few-quintuples, and tuning of the Fermi level can lead to the topological insulator surface transport regime with the theoretically predicted extraordinary thermoelectric efficiency.

Thermal Transport Properties of Multi-Walled Carbon Nanotube Arrays

2007 ◽  
Author(s):  
Huaqing Xie ◽  
An Cai ◽  
Xinwei Wang
Keyword(s):  
Thermal Conductivity ◽  
Carbon Nanotube ◽  
Thermal Diffusivity ◽  
Room Temperature ◽  
Infrared Detector ◽  
Laser Flash ◽  
Temperature Range ◽  
Nanosecond Pulsed Laser ◽  
Multi Walled Carbon Nanotube ◽  
Individual Cnts

A laser flash technique was applied to measure the thermal diffusivity along a multi-walled carbon nanotube (CNT) array in temperature range of −55∼200 °C. In the measurements, a nanosecond pulsed laser was used to realize noncontact heating and the temperature variations were recorded by an infrared detector. The experimental results show that the thermal diffusivity of the CNT array increases slightly with temperature in the −55∼70 °C temperature range and exhibits no obvious change in the −75∼200 °C temperature range. The CNT array has much larger thermal diffusivity than several known excellent thermal conductors, reaching about 4.6 cm2s−1 at room temperature. The mean thermal conductivity (λ) of individual CNTs was further estimated from the thermal diffusivity, specific heat (Cp), and density (ρ) by using the correlation of λ = αρCp. The thermal conductivity of individual CNTs increases smoothly with the temperature increase, reaching about 750 Wm−1K−1 at room temperature.

scholarly journals Влияние замещения висмута празеодимом и лантаном на термоэлектрические свойства оксиселенидов BiCuSeO

2019 ◽  
Vol 53 (2) ◽  
pp. 226
Author(s):  
А.П. Новицкий ◽  
И.А. Сергиенко ◽  
С.В. Новиков ◽  
К.В. Кусков ◽  
Д.В. Лейбо ◽  
...  
Keyword(s):  
Thermal Conductivity ◽  
Electrical Resistivity ◽  
Rare Earth ◽  
Room Temperature ◽  
Charge Carrier Concentration ◽  
Rare Earth Ions ◽  
Solid State Reaction Technique ◽  
Substitution Level ◽  
Temperature Dependences ◽  
Electronic Configurations

AbstractThe  results  of  investigating  the  thermoelectric  properties of the bulk р -type oxyselenides Bi_1 –_ x Pr_ x CuSeO ( x = 0, 0.04, 0.08) and Bi_0.96La_0.04CuSeO obtained by the solid-state reaction technique are presented. The temperature dependences of the thermopower, electrical resistivity, and thermal conductivity are measured at temperatures from room temperature to 800 K. Over the whole temperature range, a decrease in the electrical resistivity and thermopower is observed with increasing substitution level, while the thermal conductivity is almost unaffected by the substitution of rare-earth elements for bismuth. Despite the nominal valence of Bi, La, and Pr being the same, the replacement of bismuth by rare-earth ions leads to an increase in the charge-carrier concentration, which may be caused by a difference in the electronic configurations of ions, resulting in a shift of the Fermi level to the valence band.

Application of Norbury Rule to Thermal Conductivity in Intermetallic Compounds

1994 ◽  
Vol 364 ◽  
Author(s):  
Yoshihiro Terada ◽  
Tetsuo Mohri ◽  
Tomoo Suzuki
Keyword(s):  
Thermal Conductivity ◽  
Solid Solution ◽  
Intermetallic Compounds ◽  
Room Temperature ◽  
Laser Flash ◽  
Flash Method ◽  
Horizontal Distance ◽  
Conductivity Data ◽  
Host Metal ◽  
Thermal Conductivity Λ

AbstractThermal conductivity data at room temperature, which are measured by laser-flash method, are presented in B2 aluminides and titanides, and in nickel based L12 compounds. The thermal conductivity λ is changed in the following order of the compounds. λ(NiAl) >λ(CoAl)>λ(FeAl), λ(NiTi)<λ(CoTi)<λ(FeTi), λ(Ni3Al)>λ(Ni3Si) and λ(Ni3Ga)>λ(Ni3Ge). According to Norbury rule originally proposed for the concentration dependence of electrical resistivity, the increasing rate is greater in the solid solution, where the position of solute elements is more remote in horizontal distance from a host metal in the periodic table. It is found that this rule holds for the thermal conductivity measured for the intermetallic compounds with the combination of a series of guest constituents and a fixed host constituent both in the B2 and Ll2 intermetallic compounds.

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