Papers by Keyword: Porous Metals

Abstract: Development of lightweight materials becomes essential and has been applied for various structural and functional applications in industrial field since last decade. Porous metal can contribute to lightweight material with great mechanical, thermal and electrical properties. In this study, porous stainless steel was fabricated by using powder metallurgy technique and egg shell as a new potential space holder material. Stainless steel 316L was used as metal matrix powder, egg shells as space holder material, and polyethylene glycol (PEG) as binder to increase the green density of the preforms. The material was mixed using roller mill before the mixtures are ready to the next process of compaction by using uniaxial pressing machine. The samples were sintered to two-stage sintering at temperature 1000°C in a tube furnace. Physical properties of porous stainless steel were studies by performing density and porosity test. Scanning Electron Microscopy (SEM) apparatus was used to characterize morphology properties. The results show that, porous stainless steel with the composition of 30 wt. % of egg shells added into formulation yields the highest porosity compared to other compositions and the distribution of pores can be classify as micro-pores.

Abstract: The effect of high-enthalpy gas flow on transpiration cooling systems is considered. The influence of thermo-physical properties and porosity of some metals on heat transfer of the models is studied.

Abstract: Composite materials are the most advanced class of materials invented and produced by humans in modern times as well as a challenge for the future in the field of scientific and technological performance. They are made up of at least two phases of different nature which are so combined to form a new material with a superior combination of properties. They are generally materials with unusual performances on the relationship between properties and specific gravity. Composites are multiphase materials with distinct and well-defined interface between the constituent phases ensuring a transfer of property but can lead to obtaining a product with exceptional performance from the starting material. In this paper we have focused research on Al-Mg alloys with magnesium and silicon carbide (SiC). Stabilized Aluminium Foams (SAF) are new class of materials with low densities and novel physical, mechanical, thermal, electrical and acoustic properties. They offer potential for lightweight structures, for energy absorption, and for thermal management; and some of them, at least, are cheap. Metal foams offer significant performance gains in light, stiff structures, for the efficient absorption of energy, for thermal management and perhaps for acoustic control and other, more specialized, applications. They are recyclable and nontoxic. They hold particular promise for market penetration in applications in which several of these features are exploited simultaneously. The paper presents some results related to the research of metallic foams based on AlMg10 metallic alloy obtained by melt bubbled C₄H₁₀ addition of SiC particles. Microsrtucture of these foams is analyzed by using (SEM) Scanning Electron Microscope, laying out the network of pores imbued into each others developed around SiC particles and other issues microstructural characteristics.

Abstract: To improve mechanical properties of a closed-cell type aluminum foam, the surface pores are filled with aluminum powder by selective laser melting (SLM). The relationship between the laser irradiation conditions and solidification characteristics of aluminum powder is investigated with one-line laser irradiation on the aluminum powder with a thickness of 5 mm. The aluminum powder is continuously melted and solidified with laser spot diameter of 0.6 mm and scanning speed of 10–20 mm/s. According to the successful melting and solidification conditions, the SLM is applied to the surface pores of a closed-cell type aluminum foam supplied with aluminum powder. The supplied aluminum powder is confirmed to be successfully melted and welded to the aluminum foam. As the result, the aluminum foam with nonporous surface layer (sandwich structure) is fabricated by the SLM with aluminum powder. The compressive behavior of the fabricated aluminum foam with nonporous surface layer is investigated.

Abstract: Deformation behavior of porous aluminum alloys with aligned unidirectional pores through equal-channel angular extrusion (ECAE) was investigated. The porous aluminum alloys were fabricated by dipping pure aluminum pipes into semi-solid slurry base metal. The pipes did not detach from the base metal even through the ECAE process. Comparing the sample dimension of pores before and after ECAE process, the amount of decrease in a dimension of pores was 19.4% in this study. The Vickers hardness increased by work hardening. Especially, the hardness value of area where plastic flow arose increased significantly. These results show that we can improve the mechanical properties with maintenance of the porous structure and measure the amount of the sample deformation quantitatively.

Abstract: The bulk porous nickel was fabricated by layer scanning jet electrodeposition, a novel porous metal preparation technique. The dendritic crystalline layer or normal layer of the bulk porous nickel can be obtained by controlling of the growth conditions. The effects of deposition conditions, such as jet velocity, deposition current density, jet scanning mode, scanning rate, electrolyte solution, etc., on the morphology and growth process of the dendritic structures were studied in detail. It is revealed that the deposition rate and the uniformity of the pore distribution for the bulk porous Ni increase with the decrease of jet velocity. The depositing current density has an upper and lower limit. The dendritic structures are sensitive to the scanning rate, scanning mode, electrolyte solution. As a result, the optimized bulk porous nickels with controllable dendritic crystalline layered structure, pore size and porosity were fabricated by accurately controlling the growth conditions above.

Abstract: To obtain SAF we have focused research on Al-Mg alloys with different concentrations of magnesium and silicon carbide (SiC). To obtain these materials has been chosen different gas blowing method (N₂, SO₂ and C₄H₁₀). It was observed that the best results in terms of pore volume gave blowing with C₄H₁₀. The samples obtained were analyzed by optical and electron microscopy.

Abstract: A porous aluminum alloy was fabricated by joining pure aluminum pipes and Al-13mass% Si melt through continuous casting. Compressive tests were carried out with test specimens of the porous aluminum alloy fabricated by this method, non-porous aluminum alloy fabricated by continuous casting using Al-Si melt, and porous aluminum alloy consisting of only Al-Si fabricated by drilling non-porous Al-Si bar. From the compressive tests, it was confirmed that specific proof strength of the porous aluminum alloy fabricated by joining pipes and melt can be described by rule of mixture of Al-Si base metal, pure aluminium pipes and pores.

Abstract: Metal foams are very interesting materials in new emerging technologies as aeronautic, spatial research, auto-motion or heat exchanger, but there are other areas in which these materials could be advantageous. Here is a new proposal for using these materials in electromagnetic shielding. The goal is to demonstrate that, although having a smaller effective electrical conductivity than massive materials, it is possible to attain operative electromagnetic shielding with a reduction of mass and, in addition, to bring together in a single product a supplementary protection against vibrations, impact, noise, etc., as corresponds to the well-known properties of porous materials. In terms of the operating frequency, conductivity and thickness of the metallic foams the electromagnetic screening was calculated. It is shown how to guarantee a specified shielding the necessary thickness in porous materials with respect to massive metals obeys to a quadratic relation.

Abstract: Lotus-type porous structure is a new kind of micro-channel structure and can be used as heat sink for heat elimination of high powered electronic devices. Numerical analysis based on the simple fin model was used to predict the equivalent heat transfer coefficient of lotus-type porous copper micro-channel heat sink. Compared with the water, GaInSn working fluid could further promote the heat transfer performance of the heat sink. According to the theoretical analysis, a heat transfer coefficient as high as 14W/(cm²K) was attainable when the pressure drop was 50 KPa and an appropriate structure parameters: 0.4 mm in pore diameter, 0.4 in porosity and 4mm in height of porous copper were achieved.