Papers by Keyword: Porous Metal

Abstract: Metal foam is the cellular structures that made from metal and have pores in their structures. Metal foam also known as the porous metals, which express that the structure has a large volume of porosities with the value of up to 0.98 or 0.99. Porous 316L stainless steel was fabricated by powder metallurgy route with the composition of the SS316L metal powder as metallic material, polyethylene glycol (PEG) and Carbamide as the space holder. The powders were mixed in a ball mill at 60 rpm for 10 minutes and the mixtures were put into the mold for the pressing. The samples were uniaxially pressed at 3 tons and heat treated by using box furnace at 870 °C. There are several tests that have been conducted in order to characterize the physical properties of metal foam such as density and porosity testing, and the morphological testing (Scanning Electron Microscopy (SEM)). The results show that the composition of 85 wt% SS316L of metal foam show high in porosity which suitable for implants application.

Abstract: To fabricate aluminum foam having nonporous surface layer (sandwich structure), the selective laser melting (SLM) was applied to fill surface pores of a commercial closed-cell type aluminum foam with aluminum. A commercially pure aluminum powder was continuously melted and solidified by irradiating with a pulsed Nd:YAG laser with a maximum average power of 50 W. As a result, the aluminum foam having nonporous surface layer (SLM surface layer) was successfully fabricated. The compressive deformation behavior of the fabricated aluminum foam having the SLM surface layers was investigated with uniaxial compression test. The plateau stress of the aluminum foam having the SLM surface layers was improved by approximately 20%, compared with that of the aluminum foam without the SLM surface layers.

Abstract: In this paper, a novel processing method (reactive precursor method) to manufacture high-melting point porous Al-Ti intermetallics is investigated. Especially, morphological control of porous structure is focused. In the reactive precursor process, precursors are made by blending aluminum and titanium powders. The precursor is heated to ignite an exothermic reaction (so called “combustion reaction”) between the elemental powders. Pore formation is a well-known intrinsic feature of the combustion reaction, and we tried to control the pore morphology. Fundamentally, the closed-cell structure can be obtained when the maximum temperature during the reaction exceeds the melting point of the reaction product. By blending the exothermic agent powder in the precursor, the maximum temperature is increased and the reaction products are melted. The porosity is controlled by the maximum temperature. In contrast, an open-cell porous structure can be obtained when the maximum temperature is below the melting point of the reaction product. Microwave heating turned out to be an effective method to create an open cell structure. A powdery substance that does not react with other elemental powders (heat-absorbing agent powder) decreases the temperature during the reaction. Closed, open and bimodal-sized open pores have been achieved by the reactive precursor process so far.

Abstract: Porous copper fabricated by unidirectional solidification of metal-gas eutectic can be used to manufacture a special kind of micro-channel heat sink. A three dimensional model is developed to investigate the heat transfer in porous copper heat sink. However the experimental results of heat transfer performance are far less than the simulation results. That is mainly because some of the pores are nonpenetrative. When the simulation model is modified by taking the penetration ratio into account the experimental results are consistent with the simulation results.

Abstract: A molding process of aluminum foams by using a rotating mold is proposed in order to improve the mold filling and forming process for light-weight parts of vehicles. Aluminum powder mixed with a foaming agent is extruded into the mold through the die heated to a temperature higher than the melting point, and the mold is filled with the aluminum foam. When the diameter of a cylindrical mold is large, the influence of gravity is significant and the mold is not filled successfully. In the proposed molding, the aluminum foam is extruded into the rotating mold of large diameter and the volumetric ratio of foam to mold cavity is improved. However, the effect of the mold rotation on the mold filling is limited due to friction.

Abstract: In order to transfer heat as much as possible through a unit area in unit time, this paper introduces three enhanced heat transfer structures, namely microchannel, open-celled metal foam and open-celled sintered porous metal. From two aspects of the heat transfer performance and the flow resistance, this paper reviews their research progress. Among three kinds of enhanced heat transfer structures, open-celled sintered porous metal has the best heat transfer performance, followed by open-celled metal foam and micro-channel. While, the sequence of the pressure drop of three kinds of enhanced heat transfer structures is in the reverse order. Thus, Enhanced heat transfer Structures with good heat transfer performance and small pressure drop are the future research direction.

Abstract: In order to transfer heat as much as possible through a unit area in unit time, this paper introduces three enhanced heat transfer structures, namely microchannel, open-celled metal foam and open-celled sintered porous metal. Furthermore, the manufacturing methods of three enhanced heat transfer structures are summarized and comparatively analyzed. Among three enhanced heat transfer structures, open-celled sintered porous metal has the best heat transfer performance, followed by open-celled metal foam and microchannel. While, the sequence of the pressure drop of three enhanced heat transfer structures is in the reverse order. In addition, the manufacturing technology of three enhanced heat transfer structures remain inadequate. Thus, enhanced heat transfer structures with good heat transfer performance and small pressure drop and their corresponding manufacturing technology are the future research direction.

Abstract: Cool-drawn 1Cr18Ni9 stainless steel wires of 0.1~0.5 mm can be woven and punched to prepare porous metal filters. There is certain amount of connected micron pores in the transformable components. Filtration mechanism of this porous material is investigated and three series of samples with different diameter of wires, porosities and filtrating ranges are prepared. Filtration performances compares experiments are carried out on a kind of chocolate milk with the brand of Sanyuan. Three-dimensional microscopy, KEYENCE VHX-600, is applied to investigate the diaphragms before and after filtrating. Portable contamination analysis kit, HPCA-2, is chosen to identify the degree of contaminating. Results indicate that these kind of porous metal filters have valid solid/fluid separating effects. Wires diameters and other preparation parameters will identify the porosity. Thinner wires contribute to more and tinier porous and will block particles effectively. Thickness of filters plays the similar role of filtration layer. Higher porosity will increase the cleanliness of the passing fluid and decrease the filtering efficiency. The data in this paper provide technical support to the application in dairy filtration industry.

Abstract: Generally, there are two ways available for porosity measurement of porous metals. One is by calculating density ratio of a porous metal and a corresponding non-porous metal, called as relative density method. The other is by counting the percentage of pores on cross section of a porous metal, called as image analysis method. In this work, both methods were employed for lotus-type porous copper on porosity measurement. The effects of several parameters in both methods on porosity values of the porous copper are reported and discussed. The relative density method is recommended as porosity by this method is more reliable for the porous copper.