Microstructure and properties of nanoporous silver fabricated by chemical dealloying of Ag-Al alloys

• Main Authors: Tzu-Yang Wu, 吳子揚
• Other Authors: Jui-Hung Hsu
• Format: Others
• Language: en_US
• Published: 2014
• Online Access: http://ndltd.ncl.edu.tw/handle/16821358002767821496

碩士 === 國立中山大學 === 材料與光電科學學系研究所 === 102 === The pure Ag nanoporous foams are prepared by simple chemical dealloying of the melt spun Ag30Al70, Ag35Al65, and Ag40Al60 (in at%) ribbons, measuring ~8 mm in width and ~100 m in thickness. Ag30Al70 is located with the Al content greater than the eutectic composition, and the other two are less than the eutectic point. The composition difference would affect the microstructure and grain structure before dealloying and the porous morphology after dealloying. The melt-spun ribbons contain only the face-centered cubic (FCC) -Ag phase and the hexagonal -Ag2Al intermediate phase. Through proper chemical dealloying in HCl, the -Ag2Al phase would be etched away, leaving the pure Ag ligaments. The resulting open-cell foams are characterized by X-ray diffractometer (XRD), scanning electron microscopy (SEM) in terms of secondary and backscattered electron image (SEI and BEI) and energy dispersive spectrometry (EDS), as well as Brunauer Emmet and Teller (BET), Vickers microhardness, nanoindentation, mini-tension, and other means for their functional properties. In this report, the mechanical response is presented. The three pure Ag open-cellporous foams dealloyed from Ag30Al70, Ag35Al65, and Ag40Al60 possess the average pore size and of 500, 300 and 100 nm, respectively. Pore porosity is 69%, 66%, 58%, respectively. The specific surface area, measured by BET, is 4.1, 3.9 and 2.3 m2/g, respectively. The surface area decreases with decreasing pore porosity. The average micro-hardness readings for these three foams are 2.4, 2.9 and 4.5 Hv. Based on nanoindentation measurements. The elastic modulus data of these three foams are 521, 620, 916 MPa and the hardness data of these three foams are 26, 32, 43 MPa, respectively. The modulus and hardness both decrease with increasing pore porosity. Ag nano-porous foams were characterized by four point probe, and the resistivity increases exponentially with increasing pore porosity. In antimicrobial testing, Ag thin film and Ag ribbon (both without nano-pores) have better antimicrobial ability than Ag nano-porous foams. The current pore size in the Ag nano-porous foams appears too small for bacteria to penetrate, reducing the antimicrobial capability. Keywords: Nanoporous foam, Ag, mechanical response, hardness, resistivity, Antimicrobial test