Fabrication of Colored Silica Glasses by Incorporation of Nano-Sized Colloids via Reactive Electrophoretic Deposition (REPD)

Abstract

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 nanocrystals 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.

A Current Opinion on Electrophoretic Deposition in Pulsed and Alternating Fields

“…This mode of EPD, which is called reactive electrophoretic deposition (REPD), can yield exceedingly strong deposits. Furthermore, the properties of the formed deposit can be changed by altering the nature of the reaction product formed at the electrode by using suitable dopants …”

“…Furthermore, the properties of the formed deposit can be changed by altering the nature of the reaction product formed at the electrode by using suitable dopants. 25 Particle and Double Layer Behavior in the Bulk Suspension in AC Fields. In 1933, Debye predicted that, when a sound wave is transmitted through an electrolyte, a potential should be generated due to differences in frictional forces and inertia of hydrated ions.…”

Preparation of High-Purity Glasses and Advanced Ceramics Via EPD of Nanopowders

“…Thus it was possible to prepare doped silica and multicomponent glasses from SiO 2 nanoparticles by reactive electrophoretic deposition [65], but also gold ruby glasses with the heterogeneous formation of nano-sized colloids [78]. The incorporation of potassium and boron oxides in silica glass compacts is of very high technical importance to reduce the sintering temperature and to increase the coefficient of thermal expansion (CTE).…”

“…The disadvantage of the layer-wise structuring is the limited mechanical strength because delamination in the boundary region between the layers is a major problem. In EPD at least one side can be structured by depositing on a shaped electrode or membrane [68,78,118,138,201,202]. Applications were demonstrated for ceramic microcomponents of PZT or alumina [201,203], PZT microtubes [204], nanorods [205,206], and artifical opal growth [207].…”