Biomedical Engineering Reference
In-Depth Information
Raw
materials
Wet and dry
mixing grinding
Shaping
(Cold pressing)
Calcination
Testing
Electroding
Sintering
Figure 13.6
Flowchart of solid-state reaction method.
h e general steps involved in the solid-state reaction method for synthe-
sizing ceramics are described below.
Step 1 - Raw materials
Oxides and carbonates are the most common constituents of all ceramic
materials of traditional and technological importance. All starting raw
materials (carbonates, oxides, nitrides, etc.) of high purity are weighted
according to stoichiometric formula of desirable composition of ceramic
material using high precession electronic weighing machine. h e purity of
raw materials controls the quality of resulting ceramic.
Step 2 - Mixing and milling/grinding
h e second step is the mixing and milling processing of solid-state reaction
which is used to control the separation of oxides and carbonates. In this
step, all the weighted raw materials are mixed in a liquid medium (ace-
tone, ethanol, etc.) and then properly grinded for a long duration to obtain
homogeneous distribution of starting raw materials in agate mortar and
pestle or ball milling machine. h orough grinding decreases the particle
size of mixed powder. h is is necessary for obtaining close contact among
the atoms so that the right material is formed.
Step 3 - Calcinations
At er the process of mixing and milling, the grinded powder is heated
(calcined) in air atmosphere for the i rst time, where the solid-state reac-
tion takes place between the mixed constituents powder. Not only this, the
process of calcinations provides linear expansion of particles and forma-
tion of grains. h e proper formation of compound depends upon the time,
temperature and atmosphere conditions applied in the process of calcina-
tions. It has been verii ed by experiments that the calcination temperature
apparently inl uences the density of the sintered i nal ceramic products,
while the grain size of the ceramics mainly depends on the i nal sinter-
ing temperature. If the calcination temperature is very high, homogeneous
ceramic product of higher density may be obtained. h erefore proper cal-
cination at the right temperature is necessary to obtain the best micro-
structural, morphological, electrical and mechanical properties [81].
