Gas Pressure and Temperature Dependences of Thermal Conductivity of Porous Ceramic Materials: Part 1, Refractories and Ceramics with Porosity below 30%

Litovsky, Efim; Shapiro, M.

doi:10.1111/j.1151-2916.1992.tb04445.x

Cited by 81 publications

(36 citation statements)

References 21 publications

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“…if the grain volume is used instead of the linear size parameter s. Such simulation has been performed and the matching of the GSDF led to much less accord with the experimental data; namely, the function obtained failed to predict the character of GSDF behavior in the region of small grain sizes. This observation seems [4][5][6][7][8][9][10][11][12][13][14][15][16][17] to support the proposition that the division and conglomeration processes may be considered as essentially one-dimensional ones.…”

Section: Theoretical Grain Size Distributionmentioning

confidence: 75%

“…This is also true for electric resistance of copper and gold nanowires [12,13] and dense ceramic materials [14]. These investigations had demonstrated that the deviations of electric and thermal conductivities from the respective bulk properties are primarily related to electron scattering at grain boundary dislocations.…”

Section: Introductionmentioning

confidence: 83%

“…Fitting parameters of the GSDF curves computed from the experimental data ( Fig. 1) with the help of Equations (15) and (16 The fit with the experimental plots is fairly good, despite crude approximations used in deriving Equation (14). Distribution function (14) is not lognormal, contrary to statements in [1,2,5].…”

Section: Theoretical Grain Size Distributionmentioning

confidence: 97%

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Grain size distribution and heat conductivity of copper processed by equal channel angular pressing

Gendelman

Shapiro

Estrin

et al. 2006

Materials Science and Engineering: A

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ABSTRACT. We report the results of measurements of the grain size distribution function and the thermal conductivity of ultrafine-grained copper produced by equal channel angular pressing (ECAP), with special attention to the evolution of these quantities with the number of pressing cycles. To explain the experimental findings, the equilibrium grain size distribution function (GSDF) evolving during ECAP has been calculated on the basis of a simplified theoretical model. The model involves a single unknown physical parameter -the most probable grain size. With this parameter fitted to the experimental data the calculated GSDF fairly closely reproduces the experimental data. A model for thermal conductivity of ECAP processed copper has been proposed, which relates thermal conductivity to the GSDF parameters to the coefficient of electron reflection at grain boundaries.

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Section: Theoretical Grain Size Distributionmentioning

confidence: 75%

Section: Introductionmentioning

confidence: 83%

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Grain size distribution and heat conductivity of copper processed by equal channel angular pressing

Gendelman

Shapiro

Estrin

et al. 2006

Materials Science and Engineering: A

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“…The applied strain rate was 10 À3 s À1 . Thermal conductivity measurements were performed using a stationary method, 5) where a copper specimen and a reference specimen (Macor) of known thermal conductivity were subjected to the same unidirectional heat flux, which was generated by placing the specimens between a heated and a cooled platens. To minimize the thermal resistance between the two specimens and between the specimens and the platens, the specimens were mechanically polished.…”

Section: Methodsmentioning

confidence: 99%

A Portrait of Copper Processed by Equal Channel Angular Pressing

Hellmig

Janeček

Hadzima³

et al. 2008

Mater. Trans.

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Copper is one of the most important materials used for electrical connectors with a high thermal and electricial conductivity, and there is an ongoing demand to improve its mechanical properties without sacrificing other beneficial properties. A possible approach to achieving this aim is to use the method of severe plastic deformation to obtain an ultrafine grained microstructure. Significant grain refinement obtained by equal channel angular pressing (ECAP) leads to an improvement of mechanical, microstructural and physical properties. This paper gives an overview of a range of the properties that can be achieved by ECAP processing of pure copper including microstructural features, thermal stability, thermal conductivity and corrosion resistance.

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“…a b 23,24). Como se refleja en la Figura 7, el material de alúmina porosa está formado por una fase sólida no continua, con poros no esféricos y con un cierto grado de percolación, por lo que la conductividad no se ajusta con el modelo simple de Eucken (20).…”

Section: Conclusionesunclassified

Método del âPulso Láserâ para la medida de la difusividad térmica en materiales cerámicos

Garcia¹,

Martínez²,

Osendi³

et al. 2001

Bol. Soc. Esp. Ceram. Vidr.

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Entre las distintas técnicas de medida de la conductividad/difusividad térmica de materiales, destaca la técnica del pulso láser por la rapidez de medida de la difusividad térmica y la facilidad de preparación de las muestras. Sin embargo, cuando se mide la difusividad térmica en materiales porosos, aparecen problemas relacionados con la transmisión del haz láser y la subestimacion del espesor de la muestra. En este trabajo, se propone un método para evitar estos problemas que consiste en formar un sistema tricapa Cu/material poroso/Cu. Este método se ha verificado experimentalmente utilizando materiales de alúmina densa y porosa. Los valores experimentales para la alúmina porosa se han explicado a partir de modelos que estiman la conductividad térmica efectiva de un material poroso en función de la conductividad del material denso, la porosidad y el tipo de microestructura.Palabras Clave: Difusividad térmica, conductividad térmica, cerámicas porosas. Thermal diffusivity in ceramics by laser flash methodAmong the several techniques available to measure the thermal conductivity/ diffusivity, the laser flash method stands out for its low run time (less than 1 hour per temperature) and the reduced sample size required. Nevertheless, the laser flash technique is not very accurate for porous materials due to laser transmission problems and the underestimation of the total sample thickness. The attaching to the porous sample of two thin foils of an opaque and high diffusivity material (Cu) can solve these problems. This type of assembly was used to measure diffusivity in a porous alumina material. Data obtained are compared with theoretical models, wich predict effective thermal conductivity of the porous material from the thermal conductivity of the dense material, the amount of porosity and the type of microstructure. INTRODUCCIÓNEn la mayoría de las aplicaciones industriales, los materiales cerámicos están sometidos a gradientes térmicos que originan tensiones residuales y degradan su resistencia mecáni-ca. Estos gradientes térmicos dependen de la difusividad y de la conductividad térmica del material y, por ello, es fundamental conocer dichos parámetros y su variación con la temperatura. Existen varios métodos de medida (1) dependiendo del tipo de material y del rango de difusividad o conductividad. En general, se pueden agrupar en dos clases: aquellos que miden la difusividad ("pulso láser") y los que miden directamente la conductividad ("hilo caliente", "panel", "placa caliente", "comparativo"...). Algunos métodos son dinámicos como el "pulso láser" y el método del "hilo caliente", en los que el gradiente de temperatura en la muestra varía con el tiempo, mientras que otros son métodos estacionarios y calculan la conductividad cuando el sistema se encuentra en equilibrio térmico.Las características de los métodos comúnmente usados para medir la conductividad de materiales cerámicos se resumen en la Tabla I. Entre todos ellos, destaca el método del pulso láser por varias razones tales como la rapidez (1 h para ca...

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Gas Pressure and Temperature Dependences of Thermal Conductivity of Porous Ceramic Materials: Part 1, Refractories and Ceramics with Porosity below 30%

Cited by 81 publications

References 21 publications

Grain size distribution and heat conductivity of copper processed by equal channel angular pressing

Grain size distribution and heat conductivity of copper processed by equal channel angular pressing

A Portrait of Copper Processed by Equal Channel Angular Pressing

Método del âPulso Láserâ para la medida de la difusividad térmica en materiales cerámicos

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Gas Pressure and Temperature Dependences of Thermal Conductivity of Porous Ceramic Materials: Part 1, Refractories and Ceramics with Porosity below 30%

Cited by 81 publications

References 21 publications

Grain size distribution and heat conductivity of copper processed by equal channel angular pressing

Grain size distribution and heat conductivity of copper processed by equal channel angular pressing

A Portrait of Copper Processed by Equal Channel Angular Pressing

Método del âPulso Láserâ para la medida de la difusividad térmica en materiales cerámicos

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Product

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Método del âPulso Láserâ para la medida de la difusividad térmica en materiales cerámicos