Theoretical consideration of the effect of porosity on thermal conductivity of porous materials

Sumirat, Iwan; Ando, Yuuki; Shimamura, S.

doi:10.1007/s10934-006-8043-0

Cited by 183 publications

(102 citation statements)

References 7 publications

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“…The validity of our approach will be checked by comparing our results with experimental data and five different models [6,8,23,24] briefly described below. The comparison with the aforementioned models will also allow better understanding the underlying difficulties in modeling thermal conductivity of nano-porous materials.…”

Section: Results and Comparison With Other Modelsmentioning

confidence: 99%

“…At small porosities, however, the Lysenko model shows an important discrepancy with respect to ours and, more disturbing, when porosity tends to zero, the thermal conductivity does not approach the bulk value of silicon given by = 150 Wm -1 K -1 . The formula (16) proposed by Sumirat et al [24] Table 2 wherein the various models are compared to experimental data. Table 2 indicates that whatever the model, the thermal conductivity decreases with the porosity and that at fixed porosity, it is considerably reduced by passing from macro to nanopores.…”

Section: Results and Comparison With Other Modelsmentioning

confidence: 99%

“…The role of porosity and size of the nanopores has been examined. The model has been validated against experimental data and compared to other theoretical models, being those of Stokes [8] and Eucken [6], two models presented recently by Lysenko et al [23] and Sumirat et al [24] and finally the simplified percolation model. It is shown that our model fits better the experimental values than the other models.…”

Section: Discussionmentioning

confidence: 99%

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Size and porosity effects on thermal conductivity of nanoporous material with an extension to nanoporous particles embedded in a host matrix

Machrafi

Lebon

2015

Physics Letters A

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Abstract.A formula for the effective thermal conductivity of nanoporous media is derived, following a thermodynamic approach. An extension to nanocomposites composed of a homogeneous matrix wherein porous nanoparticles are dispersed is proposed as well. The originality of the model is that it is based on extended irreversible thermodynamics, a theory specifically designed for sub-scaled systems. Two different situations are discussed, in the first one, nanoporous silicon with spherical porous inclusions of micro, meso and macro-dimension respectively is considered. The description is validated by comparison with experimental data and five other models. Analysis of the results shows an excellent agreement of our theoretical approach with experiments in the whole range of porous radii, from 2 to 100 nm. In the second part of the work, thermal conductivity of porous silicon nanoparticles embedded in a germanium host matrix is investigated. The coupled influence of the pore and nanoparticles sizes is emphasized.Keywords: nanoporous media, thermal conductivity, phonon scattering, extended thermodynamics IntroductionThe effect of porosity is to decrease considerably the thermal conductivity of crystalline materials, as is observed, for instance, in nanoporous silicon [1][2][3][4][5]. This lowering property has been widely exploited with the objective to reinforce thermal insulation in several systems as microsensors, integrated circuits, semiconductor devices. It has therefore fostered an increasing interest during the last decade. Thermal properties of nanoporous media are generally investigated by referring to, for instance, kinetic theory of phonons [3], molecular simulations [5], Monte Carlo simulations [6], two-component materials [7] or hydrodynamic models [8]. In this work, we take a different route and prefer a thermodynamic approach. To be explicit, we will base our study on extended irreversible thermodynamics (EIT) [9,10], which is a formalism specifically dedicated to the treatment of micro and nano systems and highfrequency processes. For the sake of completeness, the present analysis will be compared to other theoretical models and experimental data.Nanoporous materials are generally made out of a homogeneous matrix wherein nanopores are dispersed. In that respect, such systems are similar to nanocomposites, wherein nanoparticles are embedded in a matrix, the difference being that nanoparticles are replaced by nanopores. A great deal of papers have been devoted to the problem of heat transport in nanofluids and nanocomposites, see for instance the review paper by Michaeledis [11]. In particular, the problem of the overall heat conductivity of the system as a function of the volume fraction of the nanoparticles and their size has drawn much attention. Our purpose in the present work is twofold. Firstly, it is the purpose to study the role of porosity and the size of the pores on the heat conductivity of porous systems, like nanoporous silicon, via our thermodynamic formalism. Secondly, we examine, using t...

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Section: Results and Comparison With Other Modelsmentioning

confidence: 99%

Section: Results and Comparison With Other Modelsmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

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Size and porosity effects on thermal conductivity of nanoporous material with an extension to nanoporous particles embedded in a host matrix

Machrafi

Lebon

2015

Physics Letters A

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“…Some theoretical and experimental data showed that thermal conductivity of nanoporous materials decreases with increasing porosity [25]. Rahman et al [24] have reported that the increase of the petroleum coal dust addition conduct to the decrease of mechanical strength and thermal conductivity and the increase of porosity.…”

Section: Cmss-2017mentioning

confidence: 99%

Ecofriendly bricks elaborated from coal waste of Moroccan Jerrada Mining

et al. 2018

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Abstract. Solid waste generated during mining is one of the major environmental problems associated with this industrial activity. The best solution to overcome the environmental impact of this waste is to find recycling facilities in mass-produced products that can absorb the large quantities of these available byproducts. The present study shows the feasibility of using the coal waste of Moroccan Jerrada mining in the production of ecological brick. The first step consists of consecutive stages of crushing, grinding and heating at 650°C of the coal waste with a small amount of lime in order to promote the reactive products of elaborated binders. The second step of the process consists of mixing treated coal waste with a small amount of marble dust, sand, gravel, and water, then pressed and dried at room temperature to manufacture a laboratory ecofriendly bricks. The mechanical strength and thermal conductivity are investigated.

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“…Considering the apparent powder density of 40% and the fact that the preceding layer of the powder bed is already melted and solidified, a weighted powder bed density of 60% was used in calculations. The following equations were used to estimate the physical properties of the surface powder bed layer as a function of the relative powder bed density ϕ, such as the thermal conductivity k 0 [7], the specific heat c p0 [8], and the electrical resistivity ρ 0 [9] :…”

Section: Simplified Modeling Of the L-pbf Melt Poolmentioning

confidence: 99%

Laser Powder Bed Fusion of Water-Atomized Iron-Based Powders: Process Optimization

Letenneur

Braïlovski

Kreitcberg

et al. 2017

JMMP

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Abstract:The laser powder bed fusion (L-PBF) technology was adapted for use with non-spherical economical water-atomized iron powders. A simplified numerical and experimental modeling approach was applied to determine-in a first approximation-the operation window for the selected powder in terms of laser power, scanning speed, hatching space, and layer thickness. The operation window, delimited by a build rate ranging from 4 to 25 cm 3 /h, and a volumetric energy density ranging from 50 to 190 J/mm 3 , was subsequently optimized to improve the density, the mechanical properties, and the surface roughness of the manufactured specimens. Standard L-PBF-built specimens were subjected to microstructural (porosity, grain size) and metrological (accuracy, shrinkage, minimum wall thickness, surface roughness) analyses and mechanical testing (three-point bending and tensile tests). The results of the microstructural, metrological and mechanical characterizations of the L-PBF-built specimens subjected to stress relieve annealing and hot isostatic pressing were then compared with those obtained with conventional pressing-sintering technology. Finally, by using an energy density of 70 J/mm 3 and a build rate of 9 cm 3 /h, it was possible to manufacture 99.8%-dense specimens with an ultimate strength of 330 MPa and an elongation to failure of 30%, despite the relatively poor circularity of the powder used.

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Theoretical consideration of the effect of porosity on thermal conductivity of porous materials

Cited by 183 publications

References 7 publications

Size and porosity effects on thermal conductivity of nanoporous material with an extension to nanoporous particles embedded in a host matrix

Size and porosity effects on thermal conductivity of nanoporous material with an extension to nanoporous particles embedded in a host matrix

Ecofriendly bricks elaborated from coal waste of Moroccan Jerrada Mining

Laser Powder Bed Fusion of Water-Atomized Iron-Based Powders: Process Optimization

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