Thermal conductivity and thermal diffusivity of selected oxide single crystals

2001 ◽  
Vol 16 (3) ◽  
pp. 678-682 ◽  
Author(s):  
A. Stanimirovic ◽  
N. M. Balzaretti ◽  
A. Feldman ◽  
J. E. Graebner
Keyword(s):  
Thermal Conductivity ◽  
Thermal Diffusivity ◽  
Specific Heat ◽  
Single Crystals ◽  
Room Temperature ◽  
Structural Orientation ◽  
Relative Standard ◽  
Orthogonal Orientation

Values for the thermal conductivity κ and the thermal diffusivity D of four oxide single crystals were obtained. Near room temperature, the values for κ (W cm−1 K−1) and D (cm2 s−1) are as follows: LaAlO3, κ = 0.115, D = 0.0446; NdGaO3, κ = 0.068, D = 0.0197 for one structural orientation, and κ = 0.059, D = 0.0195 for an orthogonal orientation; (LaAlO3)0.3–SrAl0.5Ta0.5O3, κ = 0.051, D = 0.0133; and, ScAlMgO4, κ = 0.062, D = 0.0229. The relative standard uncertainties in these values are ±10% (1 σ). These values allowed us to calculate the specific heat of the materials. The thermal conductivity was measured by a dc heated bar method, and the thermal diffusivity was measured by a modification of Ångström's method.

Thermophysical Properties of Germanium for Thermal Analysis of Growth from the Melt

1981 ◽  
Vol 9 ◽  
Author(s):  
Roger K. Crouch ◽  
A. L. Fripp ◽  
W. J. Debnam ◽  
R. E. Taylor ◽  
H. Groot
Keyword(s):  
Thermal Conductivity ◽  
Thermal Analysis ◽  
Thermal Diffusivity ◽  
Specific Heat ◽  
Thermophysical Properties ◽  
Room Temperature ◽  
Bridgman Method ◽  
The Other ◽  
Temperature Range ◽  
Diffusivity Measurements

ABSTRACTThe thermal diffusivity of Ge has been measured over a temperature range from 300° C to 1010° C which includes values for the melt. Specific heat has been measured from room temperature to 727° C. Thermal conductivity has been calculated over the same temperature range as the diffusivity measurements. These data are reported along with the best values from the literature for the other parameters which are required to calculate the temperature and convective fields for the growth of germanium by the Bridgman method. These parameters include the specific heat, the viscosity, the emissivity, and the density as a function of temperature.

scholarly journals Temperature-dependent thermal properties of spark plasma sintered alumina

2017 ◽  
Vol 49 (2) ◽  
pp. 117-128 ◽  
Author(s):  
Nouari Saheb ◽  
Umer Hayat
Keyword(s):  
Thermal Conductivity ◽  
Thermal Properties ◽  
Thermal Diffusivity ◽  
Specific Heat ◽  
Room Temperature ◽  
Alumina Powder ◽  
Temperature Dependent ◽  
Plasma Sintering ◽  
Spark Plasma ◽  
Sintering Method

In this work, we report temperature-dependent thermal properties of alumina powder and bulk alumina consolidated by spark plasma sintering method. The properties were measured between room temperature and 250?C using a thermal constants analyzer. Alumina powder had very low thermal properties due to the presence of large pores and absence of bonding between its particles. Fully dense alumina with a relative density of 99.6 % was obtained at a sintering temperature of 1400?C and a holding time of 10 min. Thermal properties were found to mainly dependent on density. Thermal conductivity, thermal diffusivity, and specific heat of the fully dense alumina were 34.44 W/mK, 7.62 mm2s-1, and 1.22 J/gK, respectively, at room temperature. Thermal conductivity and thermal diffusivity decreased while specific heat increased with the increase in temperature from room temperature to 250?C.

Effect of Mechanical Compression on Thermal Characteristics of Tissue-Mimicking Material

2015 ◽  
Author(s):  
Binh T. Hoang ◽  
Austin Roth ◽  
Adriana Druma ◽  
Mallika Keralapura ◽  
Sang-Joon John Lee
Keyword(s):  
Heat Transfer ◽  
Thermal Conductivity ◽  
Heat Flux ◽  
Heat Capacity ◽  
Thermal Diffusivity ◽  
Specific Heat ◽  
Specific Heat Capacity ◽  
Room Temperature ◽  
Mechanical Compression ◽  
Tissue Mimicking Material

Tissue-mimicking materials (TMM) are often used as surrogates for human tissue when developing prospective treatments such as thermal ablation of tumors. Localized heating or ablation may be applied by methods including high-intensity focused ultrasound (HIFU), radio frequency (RF), microwave, and laser treatment. In such methods, confining the heated region to a narrow target is an important concern for minimizing collateral damage to surrounding healthy tissue. Mechanical compression can potentially assist in confining heat near a target region by constricting microvascular blood flow. However, characterization of the effects of compression on thermal properties of the tissue itself (apart from microvasculature) is needed for accurate modeling of heat transfer. Accordingly this study presents a method and material characterization results that quantify the extent to which mechanical compression alters thermal conductivity, specific heat capacity, and thermal diffusivity of a polyacrylamide-based TMM. Cylindrical test specimens were cast from polyacrylamide material with diameter of 50 mm and height of 45 mm. Compression was applied using custom apparatus for applying prescribed uniaxial displacement, with a modular configuration for testing under ambient temperature as well as on a hot plate. Compression force at room temperature was measured with a load cell that was positioned in-line between compression plates. Prescribed heat flux was delivered based on power input, as quantified with the use of a reference sample in a thermal resistance network. Temperature was measured by an array of thermocouples. Software simulations were performed using finite element analysis (FEA) for structural deformation and computational fluid dynamics (CFD) for heat transfer under the combined effects of conduction and convection. The simulations provided estimates of deformed shape and thermal losses that were compared to experimental measurements. Mechanical stress-strain tests using three TMM replicate specimens at room temperature showed a linear stress-strain relationship from approximately 2% to 14% strain and a compressive modulus of elasticity ranging from 7.56 kPa to 12.7 kPa. Distributed temperature measurements under an imposed heat flux resulted in thermal conductivity between 0.89 W/(m·K) and 1.04 W/(m·K), specific heat capacity between 5590 J/(kg·K) and 6720 J/(kg·K) and thermal diffusivity between 1.29 × 10−7 m 2 /s to 1.71 × 10−7 m2/ s. Viscoelastic effects were observed to reach steady state after approximately 20 seconds, with full elastic recovery upon unloading. Thermal conductivity and thermal diffusivity were observed to decrease under mechanical compression, while specific heat capacity was observed to increase. The results affirm that thermal properties of tissue-mimicking material can be altered by mechanical compression. These findings can be applied to future investigation of temperature distribution during localized ablation by methods such as HIFU, and can be extended to refined material modeling of perfused tissue under compression.

Thermal Characterization of Carbon-Carbon Composites

2011 ◽  
Author(s):  
Messiha Saad ◽  
Darryl Baker ◽  
Rhys Reaves
Keyword(s):  
Thermal Conductivity ◽  
Thermal Properties ◽  
Thermal Diffusivity ◽  
Specific Heat ◽  
Critical Role ◽  
Carbon Composite ◽  
Flash Method ◽  
Carbon Composites ◽  
Energy Storage Devices ◽  
Graphitized Carbon

Thermal properties of materials such as specific heat, thermal diffusivity, and thermal conductivity are very important in the engineering design process and analysis of aerospace vehicles as well as space systems. These properties are also important in power generation, transportation, and energy storage devices including fuel cells and solar cells. Thermal conductivity plays a critical role in the performance of materials in high temperature applications. Thermal conductivity is the property that determines the working temperature levels of the material, and it is an important parameter in problems involving heat transfer and thermal structures. The objective of this research is to develop thermal properties data base for carbon-carbon and graphitized carbon-carbon composite materials. The carbon-carbon composites tested were produced by the Resin Transfer Molding (RTM) process using T300 2-D carbon fabric and Primaset PT-30 cyanate ester. The graphitized carbon-carbon composite was heat treated to 2500°C. The flash method was used to measure the thermal diffusivity of the materials; this method is based on America Society for Testing and Materials, ASTM E1461 standard. In addition, the differential scanning calorimeter was used in accordance with the ASTM E1269 standard to determine the specific heat. The thermal conductivity was determined using the measured values of their thermal diffusivity, specific heat, and the density of the materials.

Experimental Study on Thermal Properties of Hollow Sphere Structures

2021 ◽  
Vol 407 ◽  
pp. 185-191
Author(s):  
Josef Tomas ◽  
Andreas Öchsner ◽  
Markus Merkel
Keyword(s):  
Thermal Conductivity ◽  
Experimental Study ◽  
Thermal Properties ◽  
Thermal Diffusivity ◽  
Specific Heat ◽  
Hollow Sphere ◽  
Plane Source ◽  
Source Method ◽  
Transient Plane Source ◽  
Transient Plane Source Method

Experimental analyses are performed to determine thermal conductivity, thermal diffusivity and volumetric specific heat with transient plane source method on hollow sphere structures. Single-sided testing is used on different samples and different surfaces. Results dependency on the surface is observed.

scholarly journals Comparative study of thermal transport in Zea mays straw and Zea mays heartwood (cork) boards

2010 ◽  
Vol 14 (1) ◽  
pp. 31-38 ◽  
Author(s):  
Sunday Etuk ◽  
Louis Akpabio ◽  
Ita Akpan
Keyword(s):  
Thermal Conductivity ◽  
Heat Capacity ◽  
Zea Mays ◽  
Thermal Diffusivity ◽  
Comparative Study ◽  
Specific Heat ◽  
Specific Heat Capacity ◽  
Thermal Transport ◽  
Insulation Material ◽  
Thermal Absorptivity

Thermal conductivity values at the temperature of 301-303K have been measured for Zea mays straw board as well as Zea mays heartwood (cork) board. Comparative study of the thermal conductivity values of the boards reveal that Zea mays heartwood board has a lower thermal conductivity value to that of the straw board. The study also shows that the straw board is denser than the heartwood board. Specific heat capacity value is less in value for the heartwood board than the straw board. These parameters also affect the thermal diffusivity as well as thermal absorptivity values for the two types of boards. The result favours the two boards as thermal insulators for thermal envelop but with heartwood board as a preferred insulation material than the straw board.

Thermal Diffusivity and Conductivity of La0.7Ca0.3-xSrxMnO3 (x=0 to 0.10)

2012 ◽  
Vol 501 ◽  
pp. 319-323
Author(s):  
Hasan A. Alwi ◽  
Lay S. Ewe ◽  
Zahari Ibrahim ◽  
Noor B. Ibrahim ◽  
Roslan Abd-Shukor
Keyword(s):  
Thermal Conductivity ◽  
Electrical Conductivity ◽  
Grain Size ◽  
Transition Temperature ◽  
Thermal Diffusivity ◽  
Electrical Properties ◽  
Room Temperature ◽  
Electronic Contribution ◽  
Insulator Metal Transition ◽  
Thermal And Electrical Properties

We report the room temperature thermal conductivity κ and thermal diffusivity α of polycrystalline La0.7Ca0.3-xSrxMnO3 for x = 0 to 0.1. The samples were prepared by heating at 1220 and 1320oC. The insulator-metal transition temperature, TIM and thermal diffusivity increased with Sr content. Phonon was the dominant contributor to thermal conductivity and the electronic contribution was less than 1%. Enhancement of electrical conductivity σ and thermal diffusivity for x ≥ 0.08 was observed in both series of samples. The grain size of the samples (28 to 46 µm) does not show any affect on the thermal and electrical properties.

Influence of Mesocarp Fibre Inclusion on Thermal Properties of Foamed Concrete

2021 ◽  
Vol 87 (1) ◽  
pp. 1-11
Author(s):  
Siti Shahirah Suhaili ◽  
Md Azree Othuman Mydin ◽  
Hanizam Awang
Keyword(s):  
Thermal Conductivity ◽  
Heat Capacity ◽  
Thermal Properties ◽  
Thermal Diffusivity ◽  
Specific Heat ◽  
Specific Heat Capacity ◽  
Volume Fraction ◽  
Thermal Constant ◽  
Volume Fractions ◽  
Foamed Concrete

The addition of mesocarp fibre as a bio-composite material in foamed concrete can be well used in building components to provide energy efficiency in the buildings if the fibre could also offer excellent thermal properties to the foamed concrete. It has practical significance as making it a suitable material for building that can reduce heat gain through the envelope into the building thus improved the internal thermal comfort. Hence, the aim of the present study is to investigate the influence of different volume fractions of mesocarp fibre on thermal properties of foamed concrete. The mesocarp fibre was prepared with 10, 20, 30, 40, 50 and 60% by volume fraction and then incorporated into the 600, 1200 and 1800 kg/m3 density of foamed concrete with constant cement-sand ratio of 1:1.5 and water-cement ratio of 0.45. Hot disk thermal constant analyser was used to attain the thermal conductivity, thermal diffusivity and specific heat capacity of foamed concrete of various volume fractions and densities. From the experimental results, it had shown that addition of mesocarp fibre of 10-40% by volume fraction resulting in low thermal conductivity and specific heat capacity and high the thermal diffusivity of foamed concrete with 600 and 1800 kg/m3 density compared to the control mix while the optimum amount of mesocarp fibre only limit up to 30% by volume fraction for 1200 kg/m3 density compared to control mix. The results demonstrated a very high correlation between thermal conductivity, thermal diffusivity and specific heat capacity which R2 value more than 90%.

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