Heat transfer characteristics in the vicinity of irradiated region of the beam of a selective laser melting (SLM) process affect the creation of the melted region during the deposition. The creation of the molten pool is greatly influenced by laser parameters and powder characteristics. The goal of the paper is to investigate the influence of laser parameters and powder porosity on thermal characteristics in the vicinity of the molten pool of the SLM process through repeated finite element analyses (FEAs). The power and the scan speed are chosen as the laser parameters. The laser is assumed to be a volumetric Gaussian heat flux model. Materials of the powder and the substrate are chosen as SUS17-4PH and S45C, respectively. Temperature dependent thermal properties for those material are used to perform the FEA. An appropriate efficiency of the heat flux is predicted by comparing the results of FEAs and those of experiments. The influence of laser parameters on temperature distributions in the vicinity of the melted region and the formation of the molten pool is examined. In addition, the effects of porosity of powders on heat transfer characteristics in the vicinity of the melted region are discussed.

Various techniques for separating mixed oil and water have been developed for the purpose of controlling marine oil pollution and for the purification of wastewater containing oil from industrial processes. In this work, we fabricate porous polydimethylsiloxane (PDMS) capsules to develop a high-performance, selective oil absorber. A template method using a sugar cube is used to fabricate the porous PDMS structure by dissolving the sugar template after infiltrating it with the PDMS solution. A hollow capsule structure was prepared by controlling the infiltration time of the PDMS into the sugar template. Contact angle measurements revealed the highly porous surface of the PDMS capsule maximized the differences between hydrophobicity and oleophilicity, which improved the absorption selectivity of oil from water. The fabricated PDMS capsules exhibited superhydrophobic and superoleophilic wetting properties; the oil droplets were absorbed into the PDMS capsule upon contact, while the water droplets were not absorbed with a contact angle above 170˚. Since the absorbed oil can be stored in the capsule pores, the oil absorption capability per unit weight of the absorber is highly increased. The adsorption performance and recyclability of the PDMS capsules were also evaluated using various waste oils.