Geoscience Reference
In-Depth Information
and reactive electrode submerged arc process. A comparison of different ceramic
processing methods have already been discussed in Table 1.6.
The hydrothermal preparation of very fine powders is an excellent approach to
ideal powders. The ideal powder should have the following parameters:
i. Fine powder less than 1
μ
m
ii. Soft or no agglomeration
iii. Narrow particle-size distribution
iv. Morphology sphere or equiaxed
v. Chemical composition controllable
vi. Microstructure controllable
vii. Uniformity
viii. Free flowing
ix. Less defects dense particle
x. Less stress
xi. Reactivity sinterability
xii. Crystallinity
xiii. Reproducibility
xiv. Process control.
The shape of ceramic products obtained under hydrothermal conditions is highly
varied and some common hydrothermal products are listed below:
i. Fine powder (single crystals or amorphous)
ii. Fiber
iii. Hydrate cement
iv. Large single crystal
v. Sintered body
vi. Film.
The major advantages of hydrothermal processing of ceramics are as follows:
i. High quality
ii. High purity
iii. High rate of reaction
iv. Dispersion
v. Better shape control
vi. Pollution free
vii. Energy saving
viii. Low temperature operation
ix. Use of large volume of the equipment
x. New products
xi. Better nucleation control and so on.
However, there are some disadvantages like equipment—autoclaves which are
of complicated design, and the fact that it is expensive; cumbersome operations
like assembling and dissembling; the fact that it is impossible to observe the actual
process; solubility aspects; and problems related to surface chemistry.
Table 10.4
lists some of the salient features of the ceramic synthesis by commonly used
techniques.
