Geoscience Reference
In-Depth Information
3
Apparatus
3.1 Introduction
Advances in any scientific field of research depend largely on the equipment
available. Crystal growth or materials processing under hydrothermal conditions
requires a pressure vessel capable of containing highly corrosive solvent at high
temperature and high pressure. Experimental investigations under hydrothermal
conditions require facilities that must operate routinely and reliably under extreme
pressure
temperature conditions. Thus, the experimenter has to face a variety of
difficulties, and often, peculiar problems pertaining to the design, procedure, and
analysis.
Designing a suitable or ideal hydrothermal apparatus, popularly known as an
autoclave, is the most difficult task, and perhaps impossible to define, because
each project has different objectives and tolerances. In Chapter 2, we described
the historical development of hydrothermal technology closely associated with
the development of the instrumentation. If we look into the historical develop-
ment in the design and fabrication of autoclaves, the entire activity was concen-
trated in Europe alone during the nineteenth century. It was only after the
American industrial revolution that activityslowlystartedspreadingintotheother
parts of the world. Here, we discuss only the autoclaves or hydrothermal reactors
used worldwide; they were all developed during the twentieth century. There is a
great variety of apparatus existing in hydrothermal technology. Most of the earlier
workers had dealt with this aspect in their own way. Hence, we have made a
thorough survey of all the available literature and present it here in this section
in a simple way to make the reader understand easily the problems of designing,
fabrication, and maintenance.
The literature survey clearly indicates two schools of autoclave design: (1) Western
school and (2) Russian school. The former is very important as it dominates most
of the earliest designs, which later became the standard international designs through-
out the world. Most of these designs are relatively simple and quite old (designed prior
to the 1970s), whereas, the Russian school had dominated this field from the 1970s
and came out with many new designs. The Special Construction Bureau at the
Institute of Crystallography, Academy of Sciences, Moscow, Russian Federation, has
designed several new autoclaves to suit a specific task of either growing single crys-
tals or studying physicochemical aspects such as solubility and PVT behavior.
Besides, several erstwhile Soviet hydrothermal laboratories have produced their own
designs to suit their requirements and the type of crystal or material under investiga-
tion. Obviously, most of these autoclaves are only local and have not been adopted
