Geoscience Reference
In-Depth Information
Vessel body
Pressure
inlet
Electrical
leads
Working
volume
Closure
nut
Closure head
and packings
Furnace
windings
Sample
holder
Water
outlet
Figure 3.17 Schematic diagram of the internally heated high-pressure apparatus
[38]
.
However, vessels of this type are both expensive and cumbersome for routine and
small-scale hydrothermal research.
Similar to the above-discussed high-pressure autoclaves, there are many other
designs, but most of them are for dry systems and also for growing crystals from
flux in high-pressure medium. For example, the belt apparatus, piston cylinder
apparatus, opposed anvil or diamond anvil systems, or high-pressure autoclave
system for flux growth
[47
51]
. However, this equipment is more useful for the
geological sciences than for crystal growth or materials processing and hence we
do not discuss these designs in this topic.
3.5.2 Novel Autoclaves
The novel designs of the autoclaves are for specific studies such as controlled
growth, kinetics, solubility, PVT studies, hydrothermal
electrochemistry, conduc-
tivity of electrolytes, visual examination, HHP, microwave-plus-hydrothermal, and
sonar-plus-hydrothermal. The actual motive behind the designing of such novel
equipment is that, in the hydrothermal method, little information is available as to
the processes taking place in the autoclave and also it is extremely difficult to
observe these processes inside metal reactors or autoclaves. Hence, several earlier
workers called the hydrothermal vessels/reactors as “black boxes.” Some of these
novel designs have come from the Special Construction Bureau, Institute of
Crystallography, Moscow, during the 1970s. It is very difficult to discuss each
and every design in this topic, as there are too many novel autoclave designs.
Therefore, we shall restrict our discussion to only a few popular and unique
designs.
