Papers by Keyword: Self-Convection

Abstract: The deposition of copper onto acrylic resin powder in its self-convective motion by magnetron DC sputtering was examined in order to prepare granular polymeric spacers coated with the metal, aiming at enhancing the cell wall structure of sintered highly porous aluminum materials. The fabrication of sintered highly porous aluminum materials was carried out in an ordinary powder metallurgy processing combined with a space-holder method with the polymer-copper binary spacer granules prepared by powder-coating using the sputter-deposition technique. The effects of the sputter-deposition of copper onto the spherical polymeric spacers on cell structures of the sintered porous compacts were investigated. According to optical observations, it was found that the sputtered copper could be uniformly and adherently deposited onto the surface of the acrylic granules. According to EPMA analysis on the cross-section on a sintered porous compact, it was found that Cu atoms were distributed at the vicinity of its cell walls, concluding that cell wall structures could be enhanced by this processing. Therefore it was expected that the compressive properties of the sintered highly porous aluminum materials were also improved by this powder coating process.

Abstract: Fabrication of sintered compact from aluminum powder coated with tin deposits was examined, in order to enhance the bonding among the aluminum particles under the assistance of tin and thereby the sintering effect of the aluminum powder, aiming at improving the mechanical properties of sintered aluminum materials. For the coating of aluminum powder with tin deposits, the deposition of pure tin onto the aluminum particles was carried out by magnetron DC sputtering during the self-convective motion of the aluminum powder in a vacuum chamber. The tablet consisting of the aluminum powder coated with tin deposits was sintered at 650°C in a vacuum chamber for 2 hours, while the tablet consisting of non-coated aluminum powder was also sintered under the same condition for comparison. The sintered compact from the coated aluminum powder was solid and uniform, and its consolidation reached over 95% while that from non-coated aluminum powder was around 85%. According to tensile tests, the tensile strength of the sintered compact from the coated aluminum powder was 75.4N/mm2 while that from non-coated aluminum powder was 71.0N/mm2, and the elongation of the sintered compact from the coated aluminum powder reached over 20% while that from non-coated aluminum powder was around 10%. Therefore it was found that the consolidation and the mechanical properties of the sintered compact consisting of aluminum powder were considerably improved by this powder coating process.

Abstract: The deposition of Sn-5wt.%Al alloy onto pure aluminum powder in its self-convective motion by magnetron DC sputtering was examined in order to prepare Al-Sn composite particles, aiming not only at the development of highly uniform sintered binary compact materials but also at the improvement of the bonding between the aluminum particles after sintering at low temperature such as 250°C. The self-convection phenomenon of the aluminum powder in the vacuum chamber occurred when a perpendicular vibration was applied to the powder. The sputter-deposition of the Sn-Al alloy was carried out during the self-convection of the aluminum powder. Under SEM and according to EPMA analysis, as well as according to thermal analysis with DSC, it was confirmed that the obtained particles were coated with the Sn-Al deposits. Therefore it was found that Sn-Al composite powder could be produced by this processing, and thereby not only the development of highly uniform sintered binary compact materials but also the improvement of the bonding between the aluminum particles after sintering at low temperature were expected.