Abstract :
Manufacturing of glasses by shaping of
powders and sintering comprises several advantages,
like near-shaping of complex structures. Furthermore,
sintering to fully transparent glasses is typically
obtained at temperatures significantly lower than via
melt fabrication. Thus incorporation of functional
dopants with lower decomposition stability becomes
possible, significantly increasing the variety of possible
doping materials and applications. However, nanosized
particles with their significantly enhanced sintering
activity have to be used for powder manufacturing of
glasses to avoid crystallisation. Unfortunately, no
suitable nanopowders with appropriate composition
are commercially available, and the manufacturing
techniques proposed so far are complicated and timeconsuming,
often resulting in inhomogeneous doping.
In contrast, by means of the newly developed reactive
electrophoretic deposition (EPD) fast shaping and
doping of glasses in only one process step is possible,
using pure nanosized fumed silica powders as starting
material. Doping is achieved by electrophoretic
co-deposition of the nanoparticles and functional ions,
surrounding each particle homogeneously in the electrochemical
double layer. Thus doping with anions as
well with cations was possible, resulting in different
colouration of the silica glass (blue or gold ruby), with
the coefficient of absorption being a function of the ion
concentration within the suspension. Furthermore, a
decrease in sintering temperature was achieved
by EPR with boric acid. Finally, co-doping with anions
and cations resulted in the manufacturing of
multicomponent glasses with a decrease in sintering
temperature of 450 C compared to pure silica
OX50.
