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Special Issue "Metal Foams: Synthesis, Characterization and Applications"

A special issue of Materials (ISSN 1996-1944). This special issue belongs to the section "Porous Materials".

Deadline for manuscript submissions: closed (1 November 2015)

Special Issue Editors

Guest Editor
Dr. Sven De Schampheleire

Department of flow, heat and combustion mechanics, Ghent University, Sint-Pietersnieuwstraat 41, 9000 Ghent, Belgium
Website | E-Mail
Phone: +32 9/264 32 89
Interests: open-cell metal foam, experiments, volume averaging technique, forced and buoyancy-driven convection, conduction, contact and bonding technologies, thermal applications
Guest Editor
Dr. Dirk Lehmhus

ISIS Sensorial Materials Scientific Centre, University of Bremen, 28359 Bremen, Germany
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Interests: porous and cellular metals, metal foams, syntactic foams, metal matrix syntactic foams, metal matrix composites, powder metallurgy, powder technology, finite element analysis, integrated computational materials engineering (ICME), smart structures, sensor integration, sensorial materials, structural health monitoring (SHM)
Guest Editor
Dr. Matej Vesenjak

Faculty of Mechanical Engineering, University of Maribor, Smetanova 31, 2000 Maribor, Slovenia
Website | E-Mail
Interests: porous and cellular materials, foams, geometrical and mechanical characterisation, experimental tests, computer simulations, finite element analysis, crashworthiness
Guest Editor
Dr. Thomas Fiedler

Faculty of Engineering and Built Environment, The University of Newcastle, Building ES 414, NSW 2308 Callaghan, Australia
Website | E-Mail
Interests: Porous materials such as cellular metals and tissue engineering scaffolds; composite materials; thermal energy storage; characterisation of mechanical and thermal properties using experimental and numerical approaches

Special Issue Information

Dear Colleagues,

It is our pleasure to invite you to submit a manuscript to the forthcoming Special Issue “Metal Foams: Synthesis, Characterization and Applications” in Materials (Open Access Materials Science Journal; Impact Factor 1.879).

From the beginning of the new millennium, applications have emerged for metal foam as a special type of porous material. Research towards the structural and thermal characterization is still ongoing for both open- and closed-cell metal foams. The outcome of this research may lead to metal foam being recognized as engineering material for large-scale applications.

For thermal applications, the research focuses on forced and buoyancy driven convection and thermal conduction. The applications range from solar receivers to foamed finned heat exchangers and even a foam matrix embedded in phase change material. Accurate thermal characterization is of utmost importance for these applications. The intention here is mainly to work towards characterization of the geometry and determination of conductive, convective and radiative properties.

For structural applications, similar to the thermal case, geometrical characterization, experimental tests supplemented by modeling and computer simulations across the full parameter range (e.g., density, pore size and shape, strain rate, etc.) are addressed. This is true for established materials, but also for new variants. Reports on new materials and their production are thus also invited. Among these, works on composite and/or hybrid materials like syntactic foams, polymer-metal and ceramic-metal combinations are also welcomed.

Especially the interaction between experimental and numerical work is of importance as there is a whole range of metal foam types with different porosities, topologies, morphologies, PPI values, contact and bonding technologies, etc. Thus, well-documented experimental work is very important to validate numerical studies. Both will be considered for inclusion in the Special Issue.

Research articles, review articles, and communications are invited. Publication is subject to the usual conditions set forth by MDPI as publisher of the journal. Details may be found on the journal’s website at www.mdpi.com/journal/materials.

Should you need any further information about this Special Issue, please do not hesitate to contact us.

Dr. Sven De Schampheleire
Dr. Dirk Lehmhus
Dr. Matej Vesenjak
Dr. Thomas Fiedler
Guest Editors

Manuscript Submission Information

Manuscripts should be submitted online at www.mdpi.com by registering and logging in to this website. Once you are registered, click here to go to the submission form. Manuscripts can be submitted until the deadline. All papers will be peer-reviewed. Accepted papers will be published continuously in the journal (as soon as accepted) and will be listed together on the special issue website. Research articles, review articles as well as short communications are invited. For planned papers, a title and short abstract (about 100 words) can be sent to the Editorial Office for announcement on this website.

Submitted manuscripts should not have been published previously, nor be under consideration for publication elsewhere (except conference proceedings papers). All manuscripts are thoroughly refereed through a single-blind peer-review process. A guide for authors and other relevant information for submission of manuscripts is available on the Instructions for Authors page. Materials is an international peer-reviewed open access monthly journal published by MDPI.

Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 1500 CHF (Swiss Francs). Submitted papers should be well formatted and use good English. Authors may use MDPI's English editing service prior to publication or during author revisions.

Keywords

  • metal foams
  • mechanical properties
  • thermal properties
  • functional properties
  • manufacturing
  • application
  • computational analysis
  • experimental methods
  • geometrial characterization

Published Papers (16 papers)

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Editorial

Jump to: Research, Review

Open AccessEditorial From Stochastic Foam to Designed Structure: Balancing Cost and Performance of Cellular Metals
Materials 2017, 10(8), 922; doi:10.3390/ma10080922
Received: 31 July 2017 / Revised: 1 August 2017 / Accepted: 1 August 2017 / Published: 8 August 2017
PDF Full-text (6544 KB) | HTML Full-text | XML Full-text
Abstract
Over the past two decades, a large number of metallic foams have been developed. In recent years research on this multi-functional material class has further intensified. However, despite their unique properties only a limited number of large-scale applications have emerged. One important reason
[...] Read more.
Over the past two decades, a large number of metallic foams have been developed. In recent years research on this multi-functional material class has further intensified. However, despite their unique properties only a limited number of large-scale applications have emerged. One important reason for this sluggish uptake is their high cost. Many cellular metals require expensive raw materials, complex manufacturing procedures, or a combination thereof. Some attempts have been made to decrease costs by introducing novel foams based on cheaper components and new manufacturing procedures. However, this has often yielded materials with unreliable properties that inhibit utilization of their full potential. The resulting balance between cost and performance of cellular metals is probed in this editorial, which attempts to consider cost not in absolute figures, but in relation to performance. To approach such a distinction, an alternative classification of cellular metals is suggested which centers on structural aspects and the effort of realizing them. The range thus covered extends from fully stochastic foams to cellular structures designed-to-purpose. Full article
(This article belongs to the Special Issue Metal Foams: Synthesis, Characterization and Applications)
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Research

Jump to: Editorial, Review

Open AccessFeature PaperArticle A Discussion on the Interpretation of the Darcy Equation in Case of Open-Cell Metal Foam Based on Numerical Simulations
Materials 2016, 9(6), 409; doi:10.3390/ma9060409
Received: 8 April 2016 / Revised: 13 May 2016 / Accepted: 20 May 2016 / Published: 25 May 2016
Cited by 3 | PDF Full-text (2508 KB) | HTML Full-text | XML Full-text
Abstract
It is long known that for high-velocity fluid flow in porous media, the relation between the pressure drop and the superficial velocity is not linear. Indeed, the classical Darcy law for shear stress dominated flow needs to be extended with a quadratic term,
[...] Read more.
It is long known that for high-velocity fluid flow in porous media, the relation between the pressure drop and the superficial velocity is not linear. Indeed, the classical Darcy law for shear stress dominated flow needs to be extended with a quadratic term, resulting in the empirical Darcy–Forchheimer model. Another approach is to simulate the foam numerically through the volume averaging technique. This leads to a natural separation of the total drag force into the contribution of the shear forces and the contribution of the pressure forces. Both representations of the total drag lead to the same result. The physical correspondence between both approaches is investigated in this work. The contribution of the viscous and pressure forces on the total drag is investigated using direct numerical simulations. Special attention is paid to the dependency on the velocity of these forces. The separation of the drag into its constituent terms on experimental grounds and for the volume average approach is unified. It is shown that the common approach to identify the linear term with the viscous forces and the quadratic term with the pressure forces is not correct. Full article
(This article belongs to the Special Issue Metal Foams: Synthesis, Characterization and Applications)
Open AccessArticle Experimental and Numerical Evaluation of the Mechanical Behavior of Strongly Anisotropic Light-Weight Metallic Fiber Structures under Static and Dynamic Compressive Loading
Materials 2016, 9(5), 398; doi:10.3390/ma9050398
Received: 2 February 2016 / Revised: 11 May 2016 / Accepted: 13 May 2016 / Published: 21 May 2016
Cited by 2 | PDF Full-text (23863 KB) | HTML Full-text | XML Full-text
Abstract
Rigid metallic fiber structures made from a variety of different metals and alloys have been investigated mainly with regard to their functional properties such as heat transfer, pressure drop, or filtration characteristics. With the recent advent of aluminum and magnesium-based fiber structures, the
[...] Read more.
Rigid metallic fiber structures made from a variety of different metals and alloys have been investigated mainly with regard to their functional properties such as heat transfer, pressure drop, or filtration characteristics. With the recent advent of aluminum and magnesium-based fiber structures, the application of such structures in light-weight crash absorbers has become conceivable. The present paper therefore elucidates the mechanical behavior of rigid sintered fiber structures under quasi-static and dynamic loading. Special attention is paid to the strongly anisotropic properties observed for different directions of loading in relation to the main fiber orientation. Basically, the structures show an orthotropic behavior; however, a finite thickness of the fiber slabs results in moderate deviations from a purely orthotropic behavior. The morphology of the tested specimens is examined by computed tomography, and experimental results for different directions of loading as well as different relative densities are presented. Numerical calculations were carried out using real structural data derived from the computed tomography data. Depending on the direction of loading, the fiber structures show a distinctively different deformation behavior both experimentally and numerically. Based on these results, the prevalent modes of deformation are discussed and a first comparison with an established polymer foam and an assessment of the applicability of aluminum fiber structures in crash protection devices is attempted. Full article
(This article belongs to the Special Issue Metal Foams: Synthesis, Characterization and Applications)
Open AccessArticle Structure and Compressive Properties of Invar-Cenosphere Syntactic Foams
Materials 2016, 9(2), 115; doi:10.3390/ma9020115
Received: 25 December 2015 / Revised: 2 February 2016 / Accepted: 5 February 2016 / Published: 18 February 2016
Cited by 5 | PDF Full-text (8212 KB) | HTML Full-text | XML Full-text
Abstract
The present study investigates the mechanical performance of syntactic foams produced by means of the metal powder injection molding process having an Invar (FeNi36) matrix and including cenospheres as hollow particles at weight fractions (wt.%) of 5 and 10, respectively, corresponding to approximately
[...] Read more.
The present study investigates the mechanical performance of syntactic foams produced by means of the metal powder injection molding process having an Invar (FeNi36) matrix and including cenospheres as hollow particles at weight fractions (wt.%) of 5 and 10, respectively, corresponding to approximately 41.6 and 60.0 vol.% in relation to the metal content and at 0.6 g/cm3 hollow particle density. The synthesis process results in survival of cenospheres and provides low density syntactic foams. The microstructure of the materials is investigated as well as the mechanical performance under quasi-static and high strain rate compressive loads. The compressive stress-strain curves of syntactic foams reveal a continuous strain hardening behavior in the plastic region, followed by a densification region. The results reveal a strain rate sensitivity in cenosphere-based Invar matrix syntactic foams. Differences in properties between cenosphere- and glass microsphere-based materials are discussed in relation to the findings of microstructural investigations. Cenospheres present a viable choice as filler material in iron-based syntactic foams due to their higher thermal stability compared to glass microspheres. Full article
(This article belongs to the Special Issue Metal Foams: Synthesis, Characterization and Applications)
Open AccessArticle Development of a Hopkinson Bar Apparatus for Testing Soft Materials: Application to a Closed-Cell Aluminum Foam
Materials 2016, 9(1), 27; doi:10.3390/ma9010027
Received: 20 November 2015 / Revised: 22 December 2015 / Accepted: 29 December 2015 / Published: 5 January 2016
Cited by 3 | PDF Full-text (5066 KB) | HTML Full-text | XML Full-text
Abstract
An increasing interest in lightweight metallic foams for automotive, aerospace, and other applications has been observed in recent years. This is mainly due to the weight reduction that can be achieved using foams and for their mechanical energy absorption and acoustic damping capabilities.
[...] Read more.
An increasing interest in lightweight metallic foams for automotive, aerospace, and other applications has been observed in recent years. This is mainly due to the weight reduction that can be achieved using foams and for their mechanical energy absorption and acoustic damping capabilities. An accurate knowledge of the mechanical behavior of these materials, especially under dynamic loadings, is thus necessary. Unfortunately, metal foams and in general “soft” materials exhibit a series of peculiarities that make difficult the adoption of standard testing techniques for their high strain-rate characterization. This paper presents an innovative apparatus, where high strain-rate tests of metal foams or other soft materials can be performed by exploiting the operating principle of the Hopkinson bar methods. Using the pre-stress method to generate directly a long compression pulse (compared with traditional SHPB), a displacement of about 20 mm can be applied to the specimen with a single propagating wave, suitable for evaluating the whole stress-strain curve of medium-sized cell foams (pores of about 1–2 mm). The potential of this testing rig is shown in the characterization of a closed-cell aluminum foam, where all the above features are amply demonstrated. Full article
(This article belongs to the Special Issue Metal Foams: Synthesis, Characterization and Applications)
Open AccessArticle Compressive Behavior and Microstructural Characteristics of Iron Hollow Sphere Filled Aluminum Matrix Syntactic Foams
Materials 2015, 8(11), 7926-7937; doi:10.3390/ma8115432
Received: 21 October 2015 / Revised: 14 November 2015 / Accepted: 17 November 2015 / Published: 23 November 2015
Cited by 3 | PDF Full-text (4153 KB) | HTML Full-text | XML Full-text
Abstract
Iron hollow sphere filled aluminum matrix syntactic foams (AMSFs) were produced by low pressure, inert gas assisted infiltration. The microstructure of the produced AMSFs was investigated by light and electron microscopy, extended by energy dispersive X-ray spectroscopy and electron back-scattered diffraction. The investigations
[...] Read more.
Iron hollow sphere filled aluminum matrix syntactic foams (AMSFs) were produced by low pressure, inert gas assisted infiltration. The microstructure of the produced AMSFs was investigated by light and electron microscopy, extended by energy dispersive X-ray spectroscopy and electron back-scattered diffraction. The investigations revealed almost perfect infiltration and a slight gradient in the grain size of the matrix. A very thin interface layer that ensures good bonding between the hollow spheres and the matrix was also observed. Compression tests were performed on cylindrical specimens to explore the characteristic mechanical properties of the AMSFs. Compared to other (conventional) metallic foams, the investigated AMSFs proved to have outstanding mechanical properties (yield strength, plateau strength, etc.) and energy absorbing capability. Full article
(This article belongs to the Special Issue Metal Foams: Synthesis, Characterization and Applications)
Open AccessArticle Sound Absorption Characteristics of Aluminum Foams Treated by Plasma Electrolytic Oxidation
Materials 2015, 8(11), 7511-7518; doi:10.3390/ma8115395
Received: 27 July 2015 / Revised: 12 October 2015 / Accepted: 15 October 2015 / Published: 9 November 2015
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Abstract
Open-celled aluminum foams with different pore sizes were fabricated. A plasma electrolytic oxidation (PEO) treatment was applied on the aluminum foams to create a layer of ceramic coating. The sound absorption coefficients of the foams were measured by an impedance tube and they
[...] Read more.
Open-celled aluminum foams with different pore sizes were fabricated. A plasma electrolytic oxidation (PEO) treatment was applied on the aluminum foams to create a layer of ceramic coating. The sound absorption coefficients of the foams were measured by an impedance tube and they were calculated by a transfer function method. The experimental results show that the sound absorption coefficient of the foam increases gradually with the decrease of pore size. Additionally, when the porosity of the foam increases, the sound absorption coefficient also increases. The PEO coating surface is rough and porous, which is beneficial for improvement in sound absorption. After PEO treatment, the maximum sound absorption of the foam is improved to some extent. Full article
(This article belongs to the Special Issue Metal Foams: Synthesis, Characterization and Applications)
Open AccessArticle Fabrication of Aluminum Tubes Filled with Aluminum Alloy Foam by Friction Welding
Materials 2015, 8(10), 7180-7190; doi:10.3390/ma8105373
Received: 10 September 2015 / Revised: 8 October 2015 / Accepted: 10 October 2015 / Published: 23 October 2015
Cited by 8 | PDF Full-text (7049 KB) | HTML Full-text | XML Full-text
Abstract
Aluminum foam is usually used as the core of composite materials by combining it with dense materials, such as in Al foam core sandwich panels and Al-foam-filled tubes, owing to its low tensile and bending strengths. In this study, all-Al foam-filled tubes consisting
[...] Read more.
Aluminum foam is usually used as the core of composite materials by combining it with dense materials, such as in Al foam core sandwich panels and Al-foam-filled tubes, owing to its low tensile and bending strengths. In this study, all-Al foam-filled tubes consisting of ADC12 Al-Si-Cu die-cast aluminum alloy foam and a dense A1050 commercially pure Al tube with metal bonding were fabricated by friction welding. First, it was found that the ADC12 precursor was firmly bonded throughout the inner wall of the A1050 tube without a gap between the precursor and the tube by friction welding. No deformation of the tube or foaming of the precursor was observed during the friction welding. Next, it was shown that by heat treatment of an ADC12-precursor-bonded A1050 tube, gases generated by the decomposition of the blowing agent expand the softened ADC12 to produce the ADC12 foam interior of the dense A1050 tube. A holding time during the foaming process of approximately tH = 8.5 min with a holding temperature of 948 K was found to be suitable for obtaining a sound ADC12-foam-filled A1050 tube with sufficient foaming, almost uniform pore structures over the entire specimen, and no deformation or reduction in the thickness of the tube. Full article
(This article belongs to the Special Issue Metal Foams: Synthesis, Characterization and Applications)
Open AccessArticle Deformation and Plateau Region of Functionally Graded Aluminum Foam by Amount Combinations of Added Blowing Agent
Materials 2015, 8(10), 7161-7168; doi:10.3390/ma8105366
Received: 2 August 2015 / Revised: 22 September 2015 / Accepted: 6 October 2015 / Published: 21 October 2015
PDF Full-text (2916 KB) | HTML Full-text | XML Full-text
Abstract
Recently, to further improve the performance of aluminum foam, functionally graded (FG) aluminum foams, whose pore structure varies with their position, have been developed. In this study, three types of FG aluminum foam of aluminum alloy die casting ADC12 with combinations of two
[...] Read more.
Recently, to further improve the performance of aluminum foam, functionally graded (FG) aluminum foams, whose pore structure varies with their position, have been developed. In this study, three types of FG aluminum foam of aluminum alloy die casting ADC12 with combinations of two different amounts of added blowing agent titanium(II) hydride (TiH2) powder were fabricated by a friction stir welding (FSW) route precursor foaming method. The combinations of 1.0–0 mass %, 0.4–0 mass %, and 0.2–0 mass % TiH2 were selected as the amounts of TiH2 relative to the mass of the volume stirred by FSW. The static compression tests of the fabricated FG aluminum foams were carried out. The deformation and fracture of FG aluminum foams fundamentally started in the high-porosity (with TiH2 addition) layer and shifted to the low-porosity (without TiH2 addition) layer. The first and second plateau regions in the relationship between compressive stress and strain independently appeared with the occurrence of deformations and fractures in the high- and low-porosity layers. It was shown that FG aluminum foams, whose plateau region varies in steps by the combination of amounts of added TiH2 (i.e., the combination of pore structures), can be fabricated. Full article
(This article belongs to the Special Issue Metal Foams: Synthesis, Characterization and Applications)
Open AccessArticle Influence of Orientation and Radiative Heat Transfer on Aluminum Foams in Buoyancy-Induced Convection
Materials 2015, 8(10), 6792-6805; doi:10.3390/ma8105340
Received: 30 July 2015 / Revised: 21 September 2015 / Accepted: 23 September 2015 / Published: 9 October 2015
Cited by 6 | PDF Full-text (3608 KB) | HTML Full-text | XML Full-text
Abstract
Two differently-produced open-cell aluminum foams were compared to a commercially available finned heat sink. Further, an aluminum plate and block were tested as a reference. All heat sinks have the same base plate dimensions of four by six inches. The first foam was
[...] Read more.
Two differently-produced open-cell aluminum foams were compared to a commercially available finned heat sink. Further, an aluminum plate and block were tested as a reference. All heat sinks have the same base plate dimensions of four by six inches. The first foam was made by investment casting of a polyurethane preform and has a porosity of 0.946 and a pore density of 10 pores per linear inch. The second foam is manufactured by casting over a solvable core and has a porosity of 0.85 and a pore density of 2.5 pores per linear inch. The effects of orientation and radiative heat transfer are experimentally investigated. The heat sinks are tested in a vertical and horizontal orientation. The effect of radiative heat transfer is investigated by comparing a painted/anodized heat sink with an untreated one. The heat flux through the heat sink for a certain temperature difference between the environment and the heat sink’s base plate is used as the performance indicator. For temperature differences larger than 30 °C, the finned heat sink outperforms the in-house-made aluminum foam heat sink on average by 17%. Furthermore, the in-house-made aluminum foam dissipates on average 12% less heat than the other aluminum foam for a temperature difference larger than 40 °C. By painting/anodizing the heat sinks, the heat transfer rate increased on average by 10% to 50%. Finally, the thermal performance of the horizontal in-house-made aluminum foam heat sink is up to 18% larger than the one of the vertical aluminum foam heat sink. Full article
(This article belongs to the Special Issue Metal Foams: Synthesis, Characterization and Applications)
Open AccessArticle Synthesis and Quasi-Static Compressive Properties of Mg-AZ91D-Al2O3 Syntactic Foams
Materials 2015, 8(9), 6085-6095; doi:10.3390/ma8095292
Received: 7 August 2015 / Revised: 28 August 2015 / Accepted: 3 September 2015 / Published: 11 September 2015
Cited by 2 | PDF Full-text (2640 KB) | HTML Full-text | XML Full-text
Abstract
Magnesium alloys have considerably lower density than the aluminum alloy matrices that are typically used in syntactic foams, allowing for greater specific energy absorption. Despite the potential advantages, few studies have reported the properties of magnesium alloy matrix syntactic foams. In this work,
[...] Read more.
Magnesium alloys have considerably lower density than the aluminum alloy matrices that are typically used in syntactic foams, allowing for greater specific energy absorption. Despite the potential advantages, few studies have reported the properties of magnesium alloy matrix syntactic foams. In this work, Al2O3 hollow particles of three different size ranges, 0.106–0.212 mm, 0.212–0.425 mm, and 0.425–0.500 mm were encapsulated in Mg-AZ91D by a sub-atmospheric pressure infiltration technique. It is shown that the peak strength, plateau strength and toughness of the foam increases with increasing hollow sphere wall thickness to diameter (t/D) ratio. Since t/D was found to increase with decreasing hollow sphere diameter, the foams produced with smaller spheres showed improved performance—specifically, higher energy absorption per unit weight. These foams show better performance than other metallic foams on a specific property basis. Full article
(This article belongs to the Special Issue Metal Foams: Synthesis, Characterization and Applications)
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Open AccessArticle Endurance of Damping Properties of Foam-Filled Tubes
Materials 2015, 8(7), 4061-4079; doi:10.3390/ma8074061
Received: 20 May 2015 / Revised: 22 June 2015 / Accepted: 29 June 2015 / Published: 7 July 2015
Cited by 2 | PDF Full-text (3029 KB) | HTML Full-text | XML Full-text
Abstract
The favorable energy-absorption properties of metal foams have been frequently proposed for damping or anti-crash applications. The aim of this paper is to investigate the endurance of these properties for composite structures, made by a metal or a hybrid metal-polymeric foam used as
[...] Read more.
The favorable energy-absorption properties of metal foams have been frequently proposed for damping or anti-crash applications. The aim of this paper is to investigate the endurance of these properties for composite structures, made by a metal or a hybrid metal-polymeric foam used as the core filling of a tubular metal case. The results of experimental tests are shown, run with two types of structures: 1) square steel tubes filled with aluminum or with hybrid aluminum-polymer foams; 2) round titanium tubes filled with aluminum foams. The paper shows that the damping properties of a foam-filled tube change (improve) with the number of cycles, while all other dynamic properties are nearly constant. This result is very important for several potential applications where damping is crucial, e.g., for machine tools. Full article
(This article belongs to the Special Issue Metal Foams: Synthesis, Characterization and Applications)

Review

Jump to: Editorial, Research

Open AccessFeature PaperReview How to Study Thermal Applications of Open-Cell Metal Foam: Experiments and Computational Fluid Dynamics
Materials 2016, 9(2), 94; doi:10.3390/ma9020094
Received: 7 December 2015 / Revised: 15 January 2016 / Accepted: 21 January 2016 / Published: 3 February 2016
Cited by 10 | PDF Full-text (31328 KB) | HTML Full-text | XML Full-text
Abstract
This paper reviews the available methods to study thermal applications with open-cell metal foam. Both experimental and numerical work are discussed. For experimental research, the focus of this review is on the repeatability of the results. This is a major concern, as most
[...] Read more.
This paper reviews the available methods to study thermal applications with open-cell metal foam. Both experimental and numerical work are discussed. For experimental research, the focus of this review is on the repeatability of the results. This is a major concern, as most studies only report the dependence of thermal properties on porosity and a number of pores per linear inch (PPI-value). A different approach, which is studied in this paper, is to characterize the foam using micro tomography scans with small voxel sizes. The results of these scans are compared to correlations from the open literature. Large differences are observed. For the numerical work, the focus is on studies using computational fluid dynamics. A novel way of determining the closure terms is proposed in this work. This is done through a numerical foam model based on micro tomography scan data. With this foam model, the closure terms are determined numerically. Full article
(This article belongs to the Special Issue Metal Foams: Synthesis, Characterization and Applications)
Open AccessFeature PaperReview Commercial Applications of Metal Foams: Their Properties and Production
Materials 2016, 9(2), 85; doi:10.3390/ma9020085
Received: 15 December 2015 / Revised: 22 January 2016 / Accepted: 26 January 2016 / Published: 29 January 2016
Cited by 17 | PDF Full-text (15618 KB) | HTML Full-text | XML Full-text
Abstract
This work gives an overview of the production, properties and industrial applications of metal foams. First, it classifies the most relevant manufacturing routes and methods. Then, it reviews the most important properties, with special interest in the mechanical and functional aspects, but also
[...] Read more.
This work gives an overview of the production, properties and industrial applications of metal foams. First, it classifies the most relevant manufacturing routes and methods. Then, it reviews the most important properties, with special interest in the mechanical and functional aspects, but also taking into account costs and feasibility considerations. These properties are the motivation and basis of related applications. Finally, a summary of the most relevant applications showing a large number of actual examples is presented. Concluding, we can forecast a slow, but continuous growth of this industrial sector. Full article
(This article belongs to the Special Issue Metal Foams: Synthesis, Characterization and Applications)
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Open AccessFeature PaperReview Composite and Nanocomposite Metal Foams
Materials 2016, 9(2), 79; doi:10.3390/ma9020079
Received: 31 October 2015 / Revised: 18 January 2016 / Accepted: 19 January 2016 / Published: 28 January 2016
Cited by 16 | PDF Full-text (4792 KB) | HTML Full-text | XML Full-text
Abstract
Open-cell and closed-cell metal foams have been reinforced with different kinds of micro- and nano-sized reinforcements to enhance their mechanical properties of the metallic matrix. The idea behind this is that the reinforcement will strengthen the matrix of the cell edges and cell
[...] Read more.
Open-cell and closed-cell metal foams have been reinforced with different kinds of micro- and nano-sized reinforcements to enhance their mechanical properties of the metallic matrix. The idea behind this is that the reinforcement will strengthen the matrix of the cell edges and cell walls and provide high strength and stiffness. This manuscript provides an updated overview of the different manufacturing processes of composite and nanocomposite metal foams. Full article
(This article belongs to the Special Issue Metal Foams: Synthesis, Characterization and Applications)
Open AccessReview The Role of Computer Simulation in Nanoporous Metals—A Review
Materials 2015, 8(8), 5060-5083; doi:10.3390/ma8085060
Received: 7 July 2015 / Revised: 7 July 2015 / Accepted: 4 August 2015 / Published: 7 August 2015
Cited by 6 | PDF Full-text (3106 KB) | HTML Full-text | XML Full-text
Abstract
Nanoporous metals (NPMs) have proven to be all-round candidates in versatile and diverse applications. In this decade, interest has grown in the fabrication, characterization and applications of these intriguing materials. Most existing reviews focus on the experimental and theoretical works rather than the
[...] Read more.
Nanoporous metals (NPMs) have proven to be all-round candidates in versatile and diverse applications. In this decade, interest has grown in the fabrication, characterization and applications of these intriguing materials. Most existing reviews focus on the experimental and theoretical works rather than the numerical simulation. Actually, with numerous experiments and theory analysis, studies based on computer simulation, which may model complex microstructure in more realistic ways, play a key role in understanding and predicting the behaviors of NPMs. In this review, we present a comprehensive overview of the computer simulations of NPMs, which are prepared through chemical dealloying. Firstly, we summarize the various simulation approaches to preparation, processing, and the basic physical and chemical properties of NPMs. In this part, the emphasis is attached to works involving dealloying, coarsening and mechanical properties. Then, we conclude with the latest progress as well as the future challenges in simulation studies. We believe that highlighting the importance of simulations will help to better understand the properties of novel materials and help with new scientific research on these materials. Full article
(This article belongs to the Special Issue Metal Foams: Synthesis, Characterization and Applications)

Planned Papers

The below list represents only planned manuscripts. Some of these manuscripts have not been received by the Editorial Office yet. Papers submitted to MDPI journals are subject to peer-review.

Type of Paper: Article
Title: Aluminum Foam-finned Condensers Application in Mini- Vapor Cycle Systems (VCSs) for Electronic Cooling
Author: G. Righetti, S. Mancin*, C. Zilio
Affiliation: Dept. of Management and Engineering, University of Padova, Str.lla S. Nicola, 1, IT-3600, Vicenza, Italy
Abstract: Metal foams belong to a class of cellular structured materials with low density and novel thermal and mechanical properties. Open cell metal foams have high specific surface area, relative high thermal conductivity and present tortuous flow paths to promote mixing. In the last decade, aluminum foams have been suggested as a highly compact replacement for conventional fins for brazed aluminum heat exchangers. This paper presents a study on the possible application of aluminum foams in compact air-cooled condensers to be implemented in mini Vapour Cycle Systems (VCSs) for electronics cooling in aeronautical applications. Based on the experimental and theoretical experience on air forced convection in metal foams of the present authors, different optimized solutions are developed and compared in order to identify the most suitable ones as a function of the pore density and porosity. In particular, the effects of the pore density on the heat transfer and on the fluid flow performance of the aluminum foam-finned condensers are analysed by varying the number of pores per inch from 5 to 40, while the porosity is varied from 0.85 to 0.96. Furthermore, the performance of air cooled condensers especially designed for aeronautical applications, which implement both these new enhanced surfaces and the traditional finned ones, are simulated using a numerical code in order to assess the improvements achievable when using the metal foams as extended surfaces.

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