Chemical reduction of nano-sized Ag and its applications

• Main Authors: Hsien-Hsuen Lee, 李賢學
• Other Authors: 周更生
• Format: Others
• Language: zh-TW
• Published: 2005
• Online Access: http://ndltd.ncl.edu.tw/handle/64840104963785450520

博士 === 國立清華大學 === 化學工程學系 === 93 === Nanosized Ag was synthesized by chemical reduction method with PVP (Polyvinylpyrrolidone) as the protective agent. The reduction reaction was carried out by formaldehyde in an alkaline environment. The PVP and the by-product could be removed after proper washing process. Under optimum condition, nano-Ag of 28nm having 5% residual PVP could be obtained. The first application was to use nano-Ag to get polymeric conductive adhesives. Nano-Ag will improve the conductivity of the paste with silver flake filling close to the percolation threshold. However, when the silver flake content was above the percolation threshold, the addition of nano-Ag will increase the resistivity due to the smaller contact area between flakes and these nano-Ag powders. If the paste was made from nano-Ag and PVAc (Polyvinyl acetate) only, the viscosity can be easily adjusted by water content and therefore it can be coated by either airbrush or spin coating. The second application was to use this nano-Ag in the ink-jet printing process to make conductive lines on both glass and polyimide film using a commercial printer (EPSON R210). Conducting Ag lines with a resistivity of 5.6×10-6��-cm could be obtained after soft baking followed by the heat treatment at 260℃ for 10 minutes. The electroplating of copper makes a dense deposition over 10 �慆 in thickness onto the silver lines that will reduce the resistance of the circuit. That could serve as an alternative method to make the printed circuit board (PCB), which avoids the tedious and expensive photolithography steps. One can make the prototype fast and easily. The last application investigated here is as an antibacterial reagent that helps the cloth (JIS white cotton cloth) to kill off the Staphylococcus aureus during the AATCC-100 (American Association of Textile Chemists and Colorists) test. Cotton fabrics contain nano-Ag of 105.3ppm at the start still remains about 71% of the nano-Ag after water wash for 20 times. The antibacterial effect is >99.99% and 99.4% respectively. It was also demonstrated that these nano-Ag powder could be dispersed uniformly into Nylon fibers by a series of procedures of praying, drying, re-pelleting and spinning, and thus offers great potential as a functional additive to the synthetic fibers.