Young Ik Seo

Phosphate filtering characteristics of a hybridized porous Al alloy prepared by surface modification

In this study, a porous Al alloy filter was designed for water purification systems. The combination of higher permeability for fluid flow and excellent filtering characteristics for removing pollutants is required for water purification. The filters macropore structure was controlled by a powder metallurgical process using granulated powders for high permeability and its micropore structure was generated by alkali surface modification on the macroporous sintered body for enhanced filtration efficiency. After surface modification, the specific surface area was increased by 10 times over the as-sintered specimen. Phosphate filtering characteristic was noticeably improved by a ligand exchange between phosphate and aluminum hydroxide formed by alkali surface modification.

Ag/Al(OH)3 mesoporous nanocomposite film as antibacterial agent

In this study, Ag/Al(OH)(3) mesoporous nanocomposite film was fabricated for antibacterial agent. As a matrix, a mesoporous Al(OH)(3) layer was prepared by alkali surface modification of an Al substrate. Subsequently, mesoporous Al(OH)(3) matrix was immersed in a polyol solution for 4h at an elevated temperature to deposit silver nanoparticles (Ag NPs) by in situ dispersion. The Al(OH)(3) porous matrix had flaky crystals weaved and covered all substrate surface so that the specific surface area was considerably increased because of voids having several tens of nanometers between the flakes. After in situ dispersion of Ag NPs by polyol process, the Ag NPs were nucleated and grown at the surface of mesoporous Al(OH)(3) layer with tight binding. In antibacterial activity, Ag/Al(OH)(3) mesoporous nanocomposite film demonstrated an excellent bacterial growth inhibition property. It is believed that the Ag/Al(OH)(3) mesoporous nanocomposite film is suitable for the antibacterial agent in a wide variety of biomedical applications.

Removal of bacterial pathogen from wastewater using Al filter with Ag-containing nanocomposite film by in situ dispersion involving polyol process

In this study, a filter with deposited Ag/Al(OH)(3) mesoporous nanocomposite film was fabricated to remove bacterial pathogens from wastewater. Mesoporous Al(OH)(3) film was generated on the Al foam body by alkali surface modification, followed by immersion in a polyol solution for 4h at an elevated temperature in order to deposit silver nanoparticles (Ag NPs). The Al(OH)(3) porous matrix showed a significant increase in specific surface area due to the large size of the voids between flakes, which reached several tens of nanometers. After in situ three-dimensional deposition of Ag NPs by a polyol process, the Ag NPs were nucleated and grown at the surface of the mesoporous Al(OH)(3) film. The filter with Ag/Al(OH)(3) mesoporous nanocomposite film showed a good bacterial pathogen removal rate within a very short contact time compared to the untreated Al foam filter. Filters with deposited Ag/Al(OH)(3) mesoporous nanocomposite film have great potential for application as antimicrobial filters for tap water purification, wastewater treatment, and other bio-related applications.

Microstructure and High Temperature Mechanical Properties of Inconel 617

Inconel 617 is a candidate tube material for high temperature gas-cooled reactors (HTGR). The microstructure and mechanical properties of Inconel 617 were studied after exposure at high temperature of 1050oC. The dominant oxide layer was Cr-oxide. The internal oxide and Crdepleted region were observed below the Cr-oxide layer. The major second phases are M23C6 and M6C types of carbides. The composition of M23C6 and M6C were determined to be Cr21Mo2C6 and Mo3Cr2(Ni,Co)1C, respectively, by EDS. These carbides are coarsened during exposure. M6C carbide is more stable than M23C6 at high temperature. There was not much change in mechanical properties after exposure at 1050oC for 1000 h.

Effect of Al2O3 particle size on compressive behavior of al composites

Compressive behavior of 7xxx series Al metal matrix composite (MMC) powders with different ceramic contents and different particle size were investigated. As a starting powder of the experiments, ceramic contents of each starting powder were 5 and 10 wt.% and ceramic particle size of starting powder were 20 and 100 ㎛, respectively. And 7xxx Al blended powder was used for comparison. The powders were uniaxially cold-compacted using cylindrical die with a compacting pressure 250 MPa and sintered at 620oC in a dry N2 atmosphere for 60 min with heating rate of 20oC/min. In case of heat treatment condition, sintered parts were solution treated at 475oC and aged at 175oC. To reveal the effect of Al2O3 particle content and particle size on the mechanical properties of composites, compression test were conducted with constant strain rate of 1×10-3/s using sub-size cylindrical samples of 9 mm diameter. Compression test was performed 5 times and its average value was used. Then fractography analysis was conducted using scanning electron microscope.

Compressive Behavior of 7xxx Series Al Composites Reinforced with Al2O3

Mechanical properties of 7xxx series Al metal matrix composite (MMC) powders containing different amounts of ceramic were investigated. The ceramic contents of the starting powders were 5 wt.% or 10 wt.%. 7xxx Al blended powder was used for comparison. The powders were uniaxially cold compacted using a cylindrical die with a compacting pressure of 250 MPa and were sintered at 620oC in a dry N2 atmosphere for 60 min. The heating rate was varied up to 100oC/min. For the heat treatment, sintered parts were solution treated at 475oC and aged at 175oC. Compression tests were conducted to reveal the effect of Al2O3 particle content on the mechanical properties of the composites. Fractography was examined using a scanning electron microscope.