Fabrication of colored silica glasses by incorporation of nano-sized colloids via reactive electrophoretic deposition (REPD)

摘要

Red glasses can be fabricated in two different ways. The first one is by incorporating nanoscaled gold colloids into a glassy matrix. The coloring mechanism is based on Mie scattering on the colloids. The second mechanism is incorporating semiconductor CdS nano-crystals into a glassy matrix so that light with wave lengths smaller than 600 nm is absorbed and a red color is achieved. The common way of fabricating colored glasses on an industrial scale is melting technology. Apart from the large quantity of energy needed, coloring a glass is a multi-step process because of the following annealing process. However, the fabrication of silica glass by electrophoretic deposition (EPD) offers a large variety of advantages. Especially the control of the pore size of the green body is important because it is the base for the incorporation of nano-sized colloids. Well-known fabrication methods are multi-step processes where a green body is e.g. soaked with an AuCl_3 solution. The colloids are formed during the final sintering step. In the present work, the fabrication of a colored silica glass by a single-step process called reactive electrophoretic deposition (REPD) is presented. In this, the suspension is doped with AuCl_3 so that the gold ions are directly incorporated into the green body during deposition. First results are presented with silica glass powder mixtures as model system. Optical spectra of sintered samples and their microstructures are shown. Further emphasis was laid on the simulation of both absorption coefficients of nano-scaled gold and transmittance spectra.