Thermal Property Measurements of Carbon Nanotube Forest Synthesized by Thermal CVD Process

2009 ◽  
Author(s):  
Qingjun Cai ◽  
Bing-chung Chen ◽  
Yuan Zhao ◽  
Julia Mack ◽  
Yanbao Ma ◽  
...  
Keyword(s):  
Thermal Conductivity ◽  
Thermal Properties ◽  
Carbon Nanotube ◽  
Quartz Substrate ◽  
Laser Flash ◽  
Volume Density ◽  
Thickness Measurement ◽  
Flash Method ◽  
Thermal Cvd ◽  
3 Omega

Carbon nanotube (CNT) forest/cluster synthesized by a thermal CVD process has millimeter growth height, large porosity and nano level pore size, plus high thermal conductivity of individual CNT, thus it is potentially a good wick structure material in developing micro heat transfer devices. However, thermal properties, including effective thermal conductivity (ETC) of a bulky CNT layer, may not be as good as the common metallic wick materials. In this paper, a Netzsch DSC 404 C Pegasus is used for measurement of the CNT heat capacity. CNT volume density is obtained by measuring the ratio of a bulky CNT weight and volume. Both the laser flash and 3-omega measurement methods are employed to measure ETC for CNT wick structures synthesized by the thermal CVD processes. For the laser flash method, measurement deviations caused by reflective silicon and thin substrate are corrected by surface treatment and increased sample thickness. Measurement results of the laser flash indicate that a 600μm thick CNT layer has ETC varying from 0.7–1.2W/m.K. For the 3-omega approach, the measurement system is validated on a quartz substrate. However, the test results yield larger ETC on 250μm CNT samples. Geometric and one dimensional thermal conduction analysis indicate that the bulky CNT thermal properties are tied to CNT synthesis processes. ETC of bulky CNT layer can be enhanced by straightening CNT growth and increasing CNT growth volume density.

Study on Thermal Conductivity of Polyetheretherketone/Thermally Conductive Filler Composites

2007 ◽  
Vol 124-126 ◽  
pp. 1079-1082 ◽  
Author(s):  
Sung Ryong Kim ◽  
Dae Hoon Kim ◽  
Dong Ju Kim ◽  
Min Hyung Kim ◽  
Joung Man Park
Keyword(s):  
Thermal Conductivity ◽  
Thermal Properties ◽  
Carbon Fiber ◽  
Conductive Filler ◽  
Laser Flash ◽  
Flash Method ◽  
Phase System ◽  
Two Phase ◽  
Nielsen Theory ◽  
Thermally Conductive

Thermal properties of PEEK/silicon carbide(SiC) and PEEK/carbon fiber(CF) were investigated from ambient temperature up to 200°C measured by laser flash method. Thermal conductivity was increased from 0.29W/m-K without filler up to 2.4 W/m-K with at 50 volume % SiC and 3.1W/m-K with 40 volume % carbon fiber. Values from Nielsen theory that predicts thermal conductivity of two-phase system were compared to those obtained from experiment.

Improvement of Thermal Conductivity of Silicone by Carbon Nanotube Array (CNTA)

2014 ◽  
Vol 1061-1062 ◽  
pp. 96-99 ◽  
Author(s):  
Liang Ke Wu ◽  
Ji Ying ◽  
Li Ting Chen
Keyword(s):  
Thermal Conductivity ◽  
Carbon Nanotube ◽  
Laser Flash ◽  
Laser Flash Method ◽  
Thermal Interface Material ◽  
Flash Method ◽  
Nanotube Array ◽  
Thermal Interface ◽  
Carbon Nanotube Array ◽  
Operating Temperatures

In order to improve the thermal conductivity of silicone, we prepared silicone/carbon nanotube array (CNTA) composite by immersing the CNTA into silicone solution and cured at 110 °C. The thermal conductivity of silicone and silicone/CNTA composite was measured by laser flash method at 30 °C, 60 °C, 90 °C, 120 °C, which are usually the operating temperatures. It was found that the thermal conductivity of silicone/CNTA composite increased with the temperature until achieved the plateau near 90 °C. The maximum thermal conductivity of silicone/CNTA composite is 0.674 W/mK, which is 220% higher than that of neat silicone. The excellent thermal conductivity makes the composite a promising thermal interface material.

Laser Flash Measurement of Samples With a Transparent Reference Layer

2009 ◽  
Author(s):  
Heng Ban ◽  
Zilong Hua
Keyword(s):  
Thermal Conductivity ◽  
Thermal Properties ◽  
Thermal Diffusivity ◽  
Temperature Response ◽  
Front Surface ◽  
Laser Flash ◽  
Laser Flash Method ◽  
Flash Method ◽  
Thermal Diffusivity Measurement ◽  
Reference Layer

The laser flash method is a standard method for thermal diffusivity measurement. This paper reports the development of a method and theory that extends the standard laser flash method to measure thermal conductivity and thermal diffusivity simultaneously. By attaching a transparent reference layer with known thermal properties on the back of a sample, the thermal conductivity and thermal diffusivity of the sample can be extracted from the temperature response of the interface between the sample and the reference layer to a heating pulse on the front surface. The theory can be applied for sample and reference layer with different thermal properties and thickness, and the original analysis of the laser flash method becomes a limiting case of the current theory with an infinitely small thickness of the reference layer. The uncertainty analysis was performed and results indicated that the laser flash method can be used to extract the thermal conductivity and diffusivity of the sample. The results can be applied to, for instance, opaque liquid in a quartz dish with silicon infrared detector measuring the temperature of liquid-quartz interface through the quartz.

Thermal Properties and Fracture Behavior of Compositionally Graded Al-SiCp Composites

2004 ◽  
Vol 449-452 ◽  
pp. 621-624 ◽  
Author(s):  
Kyung Mok Cho ◽  
Il Dong Choi ◽  
Ik Min Park
Keyword(s):  
Thermal Conductivity ◽  
Thermal Properties ◽  
Thermal Shock ◽  
Volume Fraction ◽  
Laser Flash ◽  
Fatigue Tests ◽  
Functionally Graded ◽  
Flash Method ◽  
Compositional Gradient ◽  
Infiltration Process

Compositionally graded Al-SiCp composites were fabricated using pressureless infiltration process. Microstructure was examined and thermal properties were characterized for Al-SiCp composites. Al-SiCp composites with fairly uniform distribution and compositional gradient of SiC reinforcement in the Al matrix though the thickness direction was successfully fabricated. The thermal conductivity of Al-SiCp composites was measured at room temperature, 200°C and 400°C using laser flash method. Thermal conductivity of Al-SiCp composites increases non-linearly with decreasing the volume fraction of SiC. Cyclic thermal shock fatigue tests were performed by immersing Al-SiCp functionally graded materials(FGM) into water from the various heating temperatures of 400°C , 300°C and 200°C , repeatedly. After cyclic thermal shock fatigue tests, micro-hardness was measured and formation of cracks was investigated.e fati

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.

scholarly journals XVI Международная конференция "Термоэлектрики и их применения --- 2018" (ISCTA 2018), Санкт-Петербург, 8-12 октября 2018 г. Влияние неидеальности геометрической формы образца на неопределенность измерений теплопроводности методом лазерной вспышки

2019 ◽  
Vol 53 (6) ◽  
pp. 731
Author(s):  
А.В. Асач ◽  
Г.Н. Исаченко ◽  
А.В. Новотельнова ◽  
В.Е. Фомин ◽  
К.Л. Самусевич ◽  
...  
Keyword(s):  
Thermal Conductivity ◽  
Measurement Uncertainty ◽  
Conductivity Measurement ◽  
Laser Flash ◽  
Comsol Multiphysics ◽  
Flash Method ◽  
Cylindrical Shape ◽  
Plane Parallel ◽  
Coefficient Of Thermal Conductivity ◽  
Truncated Cylinder

The influence of the geometric shape of the samples on the uncertainty of the coefficient of thermal conductivity measurement of materials by the method of a laser flash has been studied. Using a method of mathematical modeling in the Comsol Multiphysics software, a model that simulates the process of measuring the coefficient of thermal conductivity of samples made of graphite, Mg2Si0.4Sn0.6 and bismuth telluride using a laser flash method has been created. Samples of cylindrical shape with plane-parallel sides and samples in the form of a truncated cylinder, as well as samples in the form of a parallelepiped with a square base, were investigated. It is shown that the measurement uncertainty of samples with plane-parallel sides and sizes up to 12.7 mm, does not exceed 2%. For samples in the form of a truncated cylinder with a diameter of 3 mm and at an angle of ϕ= 1.5°, the measurement uncertainty does not exceed 3%. With an increase in the sample diameter and the ϕ angle, the measurement uncertainty increases significantly.

Laser flash method for measuring thermal conductivity of liquids. Application to molten salts

1981 ◽  
Vol 20 (4) ◽  
pp. 333-336 ◽  
Author(s):  
Yutaka Tada ◽  
Makoto Harada ◽  
Masataka Tanigaki ◽  
Wataru Eguchi
Keyword(s):  
Thermal Conductivity ◽  
Molten Salts ◽  
Laser Flash ◽  
Laser Flash Method ◽  
Flash Method

scholarly journals Effect of Equal Channel Angular Extrusion on the Thermal Conductivity of an AX52 Magnesium Alloy

Crystals ◽  
2020 ◽  
Vol 10 (6) ◽  
pp. 497
Author(s):  
Zuzanka Trojanová ◽  
Kristýna Halmešová ◽  
Ján Džugan ◽  
Zdeněk Drozd ◽  
Peter Minárik ◽  
...  
Keyword(s):  
Thermal Conductivity ◽  
Thermal Properties ◽  
Magnesium Alloy ◽  
Equal Channel Angular Extrusion ◽  
Light And Electron Microscopy ◽  
Processing Route ◽  
Flash Method ◽  
Nominal Composition ◽  
Microstructural Parameters ◽  
Angular Pressing

An AX52 magnesium alloy (nominal composition Mg-5Al-2Ca in w.%) was submitted to equal channel angular pressing (ECAP) using processing route A; 1–8 passes through the ECAP tool were applied. The thermal conductivity of the ECAP samples was measured using a flash method in the temperature interval from room temperature up to 350 °C. The microstructure and texture of the samples were studied by light and electron microscopy. The severe plastic deformation, realized by the ECAP, influences the thermal properties of the alloy. The possible microstructural parameters determining the thermal conductivity were analyzed. New dislocations, the grain, phase boundaries, and texture of the samples may perceptibly change the thermal properties.

Thermoelectric Properties of Phase Separated Composite of Ln-Doped SrTiO3 and TiO2 Micro Crystals

2007 ◽  
Vol 1044 ◽  
Author(s):  
Kiyoshi Fuda ◽  
Kenji Murakami ◽  
Shigeaki Sugiyama
Keyword(s):  
Thermal Conductivity ◽  
High Performance ◽  
Fine Particles ◽  
Bulk Material ◽  
Laser Flash ◽  
Flash Method ◽  
Helium Atmosphere ◽  
Low Thermal Conductivity ◽  
Seebeck Coefficients ◽  
Thermal Diffusivities

AbstractIt seems that no satisfactory TE property has been found in n-type oxide bulk materials even though Al-doped ZnO and La-doped SrTiO3 have high thermoelectric (TE) responses. Difficulty in developing high-performance TE materials seems to lie in finding low thermal conductivity in such oxides. The purpose of this study is to find a possibility to make an n-type TE oxide bulk material having low thermal conductivity and excellent TE properties as well. For this purpose, we fabricated and examined a series of composites constructed of TiO2 and Ln-doped SrTiO3 fine crystals. The composites were prepared via two processing steps: (1) precursor oxide preparation by wet processes; (2) sintering by using spark plasma sintering (SPS) apparatus. The microscopic structure was examined by using scanning electron microscope (SEM; HITACHI S-4500 model) attached with an energy dispersive x-ray spectroscopy. The electrical conductivities and the Seebeck coefficients were measured simultaneously using an ULVAC ZEM-1 instrument in helium atmosphere. The thermal diffusivities were measured by a laser flash method in vacuum. The composites obtained here were found to commonly have a mosaic type texture constructed of TiO2 and SrTiO3 fine particles with a typical size of 500 nm. The thermal conductivity values measured for three samples with different contents are ranged between 3 and 4 Wm-1K-1 in the temperature range from room temperature to 800 C. The values are apparently lower than the value for single crystal SrTiO3 samples presented in literature. Taking account the other TE data, e.g. Seebeck coefficient and electrical conductivity, we calculated dimensionless figure of merit, ZT, to be at maximum 0.15 at 800°C.

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