Electrical Conductivity of Open-cell Metal Foams

2002 ◽  
Vol 17 (3) ◽  
pp. 625-631 ◽  
Author(s):  
K. P. Dharmasena ◽  
H. N. G. Wadley
Keyword(s):  
Electrical Conductivity ◽  
Relative Density ◽  
Linear Dependence ◽  
Aluminum Foam ◽  
Cell Model ◽  
Low Frequency ◽  
Metal Foams ◽  
Unit Cell ◽  
Cross Sectional ◽  
Open Cell

Cellular metal foams are of interest because of the ability to tailor their mechanical, thermal, acoustic, and electrical properties by varying the relative density and cell morphology. Here, a tetrakaidecahedral unit-cell approach is used to represent an open-cell aluminum foam and a simplified electrical resistor network derived to model low frequency current flow through the foam. The analysis indicates that for the range of relative densities studied (4–12%), the conductivity of tetrakaidecahedral foams has a linear dependence upon relative density. The distribution of metal in the cell ligaments was found to significantly affect the conductivity. Increasing the fraction of metal at the ends of the ligaments resulted in a decrease in electrical conductivity at a fixed relative density. Low frequency electrical conductivity measurements of an open-cell aluminum foam (ERG Duocel) confirmed the linear dependence upon density, but the slope was smaller than that predicted by the unit-cell model. The difference between the model and experiment was found to be the result of the presence of a distribution of cell sizes and types in real samples. This effect is due to the varying number of ligaments, ligament lengths, and the cross-sectional areas available for current conduction across the cellular structure.

An Analytical Unit Cell Model for the Effective Thermal Conductivity of High Porosity Open-Cell Metal Foams

2014 ◽  
Vol 102 (3) ◽  
pp. 403-426 ◽  
Author(s):  
Xiao Hu Yang ◽  
Jia Xi Bai ◽  
Hong Bin Yan ◽  
Jiu Jie Kuang ◽  
Tian Jian Lu ◽  
...  
Keyword(s):  
Thermal Conductivity ◽  
Effective Thermal Conductivity ◽  
Cell Model ◽  
Metal Foams ◽  
Unit Cell ◽  
High Porosity ◽  
Unit Cell Model ◽  
Open Cell

scholarly journals Gas Diffusion Layers in Fuel Cells and Electrolysers: A Novel Semi-Empirical Model to Predict Electrical Conductivity of Sintered Metal Fibres

Energies ◽  
2019 ◽  
Vol 12 (5) ◽  
pp. 855 ◽  
Author(s):  
Reza Omrani ◽  
Bahman Shabani
Keyword(s):  
Electrical Conductivity ◽  
Fuel Cells ◽  
Gas Diffusion ◽  
Metal Foams ◽  
Critical Porosity ◽  
Gas Diffusion Layers ◽  
Open Cell ◽  
Diffusion Layers ◽  
Sintered Metal ◽  
Closed Cell

This paper introduces novel empirical as well as modified models to predict the electrical conductivity of sintered metal fibres and closed-cell foams. These models provide a significant improvement over the existing models and reduce the maximum relative error from as high as just over 30% down to about 10%. Also, it is shown that these models provide a noticeable improvement for closed-cell metal foams. However, the estimation of electrical conductivity of open-cell metal foams was improved marginally over previous models. Sintered porous metals are widely used in electrochemical devices such as water electrolysers, unitised regenerative fuel cells (URFCs) as gas diffusion layers (GDLs), and batteries. Having a more accurate prediction of electrical conductivity based on variation by porosity helps in better modelling of such devices and hence achieving improved designs. The models presented in this paper are fitted to the experimental results in order to highlight the difference between the conductivity of sintered metal fibres and metal foams. It is shown that the critical porosity (maximum achievable porosity) can play an important role in sintered metal fibres to predict the electrical conductivity whereas its effect is not significant in open-cell metal foams. Based on the models, the electrical conductivity reaches zero value at 95% porosity rather than 100% for sintered metal fibres.

Preliminary NVH Characterization of Metal Foam-Polymer Interpenetrating Phase Composites

2009 ◽  
Author(s):  
Satish Sharma ◽  
Nassif E. Rayess ◽  
Nihad Dukhan
Keyword(s):  
Mathematical Model ◽  
Thermal Stability ◽  
Hybrid Material ◽  
Aluminum Foam ◽  
Metal Foam ◽  
Dynamic Properties ◽  
Metal Foams ◽  
Thermoplastic Polymer ◽  
Open Cell

The damping and basic dynamic properties of a novel type of multifunctional hybrid material known as Metal Foam-Polymer Composite are investigated. This material is obtained by injection molding a thermoplastic polymer through an open cell Aluminum Foam, in essence creating two contiguous morphologies; an Aluminum Foam interconnected “skeleton” with the open pores filled with a similarly interconnected polymer substructure. This coexistence of both materials allows each to contribute its salient properties (e.g. the plastics contributing surface toughness and the metal foams contributing thermal stability). Basic damping testing results are presented for various Aluminum Foam porosities and pore sizes as well as for three types of polymers. A basic mathematical model of the damping is also presented. The integrity of the interface between the Aluminum Foam and the Polymer is discussed in terms of its effect on the overall material damping.

Structure and Deformation of Gradient Metal Foams Produced by Machining

2019 ◽  
Author(s):  
H. Qiao ◽  
T. G. Murthy ◽  
C. Saldana
Keyword(s):  
Aluminum Foam ◽  
Mechanical Performance ◽  
Metal Foams ◽  
Aluminum Foams ◽  
Open Cell ◽  
Computed Tomographic ◽  
Surface Gradient ◽  
Structure Changes

Abstract The effects of surface structure on mechanical performance for open-cell aluminum foam specimens was investigated in the present study. A surface gradient for pore structure and diameter was introduced into open cell aluminum foams by machining-based processing. The structure changes in the strut and pore network were evaluated by computed tomography characterization. The role of structure gradients in affecting mechanical performance was determined using digital volume correlation and in situ compression within the computed tomographic scanner. These preliminary results show that the strength of these materials may be enhanced through surface structural gradients.

scholarly journals Simulation of Thermal Transport in Open-Cell Metal Foams: Effect of Periodic Unit Cell Structure

2006 ◽  
Author(s):  
Shankar Krishnan ◽  
Suresh V. Garimella ◽  
Jayathi Y. Murthy
Keyword(s):  
Thermal Transport ◽  
Pore Space ◽  
Cell Structure ◽  
Flow Characteristics ◽  
Metal Foams ◽  
Unit Cube ◽  
Unit Cell ◽  
Face Centered Cubic ◽  
Open Cell ◽  
Periodic Unit Cell

Direct simulation of thermal transport in open-cell metal foams is conducted using different periodic unit cell geometries. The periodic unit cell structures are constructed by assuming the pore space to be spherical and subtracting the pore space from a unit cube of the metal. Different types of packing arrangement for spheres are considered - Body Centered Cubic, Face Centered Cubic, and the A15 lattice (similar to a Weaire-Phelan unit cell) - which give rise to different foam structures. Effective thermal conductivity, pressure drop and Nusselt number are computed by imposing periodic boundary conditions for aluminum foams saturated with air or water. The computed values compare well with existing experimental measurements and semi-empirical models for porosities greater than 80%. The effect of different foam packing arrangements on the computed thermal and fluid flow characteristics is discussed. The capabilities and limitations of the present approach are identified.

Structure and Deformation of Gradient Metal Foams Produced by Machining

2019 ◽  
Vol 141 (7) ◽  
Author(s):  
Haipeng Qiao ◽  
Tejas G. Murthy ◽  
Christopher Saldana
Keyword(s):  
Aluminum Foam ◽  
Mechanical Performance ◽  
Metal Foams ◽  
Aluminum Foams ◽  
Open Cell ◽  
Computed Tomographic ◽  
Surface Gradient ◽  
Structure Changes

The effects of surface structure on mechanical performance for open-cell aluminum foam specimens were investigated in the present study. A surface gradient for pore structure and diameter was introduced into open-cell aluminum foams by machining-based processing. The structure changes in the strut and pore network were evaluated by computed tomography characterization. The role of structure gradients in affecting mechanical performance was determined using digital volume correlation and in situ compression within the computed tomographic scanner. These preliminary results show that the strength of these materials may be enhanced through surface structural gradients.

Thermal and Fluid Transport in Micro-Open-Cell Metal Foams: Effect of Node Size

2017 ◽  
Vol 140 (1) ◽  
Author(s):  
Xiaohu Yang ◽  
Yang Li ◽  
Lianying Zhang ◽  
Liwen Jin ◽  
Wenju Hu ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Fluid Flow ◽  
Chemical Engineering ◽  
Fluid Transport ◽  
Metal Foams ◽  
Cross Sectional ◽  
Open Cell ◽  
Conjugated Heat Transfer ◽  
Sectional Shape ◽  
Node Size

Open-cell metal foams exhibit distinctive advantages in fluid control and heat transfer enhancement in thermal and chemical engineering. The thermofluidic transport characteristics at pore scale such as topological microstructure and morphological appearance significantly affect fluid flow and conjugated heat transfer in open-cell metal foams, important for practically designed applications. The present study employed an idealized tetrakaidecahedron unit cell (UC) model to numerically investigate the transport properties and conjugated heat transfer in highly porous open-cell metal foams (porosity—0.95). The effects of foam ligaments and nodes (size and cross-sectional shape) on thermal conduction, fluid flow, and conjugated heat transfer were particularly studied. Good agreement was found between the present predictions and the results in open literature. The effective thermal conductivity was found to decrease with increasing node-size-to-ligament ratio, while the permeability and volume-averaged Nusselt number were increased. This indicated that the effects of node size and shape upon thermofluidic transport need to be considered for open-cell metal foams having high porosities.

Numerical Investigation of the Thermal Properties of Irregular Foam Structures

2011 ◽  
Vol 312-315 ◽  
pp. 941-946 ◽  
Author(s):  
Seyed Mohammad Hossein Hosseini ◽  
A. Kharaghani ◽  
Christoph Kirsch ◽  
Andreas Öchsner
Keyword(s):  
Thermal Conductivity ◽  
Thermal Expansion ◽  
Thermal Properties ◽  
Relative Density ◽  
Metal Foams ◽  
Foam Structure ◽  
Open Cell ◽  
Closed Cell ◽  
Effective Thermal Expansion ◽  
Degree Of Irregularity

The thermal properties of irregular open-cell and closed-cell metal foams are investigated via numerical simulation. The influence of relative density and cell irregularity on the thermal conductivity and thermal expansion of the foam structure is determined. It is concluded that the effective thermal conductivity of the foam structure depends linearly on the relative density, whereas no dependence on the degree of irregularity is observed. The effective thermal expansion coefficient of the foam structure is constant for the range of parameters considered.

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