Abstract
This study is divided into three parts. The first part is about a two-step polyol batch process to synthesize silver nanowires. The principle of experimental design was applied here to investigate the relative importance of several parameters. Here, silver nitrate, PVP, ethylene glycol (EG, both as solvent and weak reductant) together with KCl were used in the process. Our results indicated that the temperature at which the second batch of silver nitrate was added was important in determining the length and uniformity of silver nanowires. Further studies suggested that when the temperature was lowered from 155oC to 145oC at the addition of second batch AgNO3, the Ag NW could decrease from tens micron down to 3 micron. In general, the length and uniformity of Ag NW observed in this work was explained mainly with Ostwald ripening phenomenon in the solution. The second part is on the development of the continuous production of silver nanowires. A one-stage process was investigated. Here the reaction time, PVP quantity and reaction temperature were studied of which reaction temperature seemed to offer very significant effects. After trial-and-error, we could obtain Ag NWs with average length of 22 micron, standard deviation of 5 micron and diameter of 90 nm, if the reaction temperature was maintained at 150-155oC and PVP/AgNO3 weight ratio of 1.66. Based on this fact and our previous experience from batch operation, the two-stage continuous process was also developed. The parameters of AgNO3 concentration, quantity of KCl were studied. We demonstrated that the length of Ag NW could be changed from about 22 micron down to 15 micron. Increase of KCl could indeed decrease the diameter of this wire down to 50 nm. For this continuous process, we could obtain about 2 g Ag NW/hr at the optimal condition. As to the third part, the effect of adding Ag NW to Ag nanoparticle on electrical conductivity was studied. Films of different thickness were fabricated by spray coating with slurry containing both Ag NP and Ag NW. Our results showed that Ag NW can increase the electrical conductivity by 10% when replacing 1% Ag NP with Ag NW. The viscosity of these slurries were also measured and it was found out that the viscosity was mainly affected by solid content and the inclusion of nanowires would have a negative effect on viscosity.