Geoscience Reference
In-Depth Information
10
Hydrothermal Technology for
Nanotechnology—A Technology
for Processing of
Advanced Materials
10.1 Introduction
The term materials processing is used in a very broad sense to cover all sets of tech-
nologies and processes for a wide range of industrial sectors. Obviously, it refers to
the preparation of materials with a desired application potential. Among various tech-
nologies available today in advanced materials processing, the hydrothermal tech-
nique occupies a unique place owing to its advantages over conventional
technologies. It covers processes like: hydrothermal synthesis, hydrothermal crystal
growth leading to the preparation of fine to ultrafine crystals, bulk single crystals,
hydrothermal transformation, hydrothermal sintering, hydrothermal decomposition,
hydrothermal stabilization of structures, hydrothermal dehydration, hydrothermal
extraction, hydrothermal
treatment, hydrothermal phase
equilibria, hydrother-
mal
electrochemical reactions, hydrothermal recycling, hydrothermal microwave-
supported reactions, hydrothermal
sonochemical,
hydrothermal
electrochemical processes, hydrothermal fabrication, hot pressing,
hydrothermal metal reduction, hydrothermal leaching, hydrothermal corrosion, and
so on. The hydrothermal processing of advanced materials has lots of advantages and
can be used to give high product purity and homogeneity, crystal symmetry,
metastable compounds with unique properties, narrow particle size distributions, a
lower sintering temperature, a wide range of chemical compositions, single-step pro-
cesses, dense sintered powders, submicron to nanoparticles with a narrow size distri-
bution using simple equipment, lower energy requirements, fast reaction times,
lowest residence time, as well as for the growth of crystals with polymorphic modifi-
cations, the growth of crystals with low to ultra-low solubility, and a host of other
applications
[1]
.
In the twenty-first century, hydrothermal technology, on the whole, will not be
just limited to the crystal growth, or leaching of metals, but it is going to take a
very broad shape covering several interdisciplinary branches of science. Therefore,
it has to be viewed from a different perspective. Further, the growing interest in
enhancing the hydrothermal reaction kinetics using microwave, ultrasonic, mechan-
ical, and electrochemical reactions will be distinct
[2]
. Also,
mechanochemical, hydrothermal
the duration of
