Biomedical Engineering Reference
In-Depth Information
13.2.1
Materials Preparation Method
h ere are various methods for preparation of materials. Some of the impor-
tant methods are discribed below.
13.2.1.1 Sol-Gel Process
In the sol-gel (solution-geletion) process, a solution of appropriate precur-
sors is formed i rst, followed by conversion into homogeneous gel at er
hydrolysis and condensation. Drying and subsequent calcinations of the
gel yields an oxide product. Hydrolysis is carried out under controlled
temperature, pH and concentration of alkoxides, added water and alco-
hol. At er the process of condensation, the rigid coherent gel is dried and
heated at temperature lower than other techniques. At er heat treatment,
the organic group is removed, leaving metal oxides.
h ere are two main approaches for the sol-gel process and both have
been utilized for the preparation of compound. One of them is the
Colloidal gel route in which a rapid hydrolysis process occurs in the pres-
ence of water. Sol-gel processing of colloids was i rst exploited in the late
1950s for fabrication of h O
2
-UO
2
ceramics for use [62]
as spherical fuel
powders in high-temperature thermal nuclear reactors. h e sol-gel process
is also known as chemical solution deposition. h is method is used for
low-temperature synthesis of BiFeO
3
nanopowders [63],
as well as BiFeO
3
ceramics
[64].
13.2.1.2
Wet Chemical Method
h e wet chemical method involves precipitation, extraction and distilla-
tion. In a wet chemical method, the mixture of two hydroxides was obtained
by mixing and stirring at room temperature. h en, NaOH is mixed drop-
wise again and the processes of stirring, aging and distillation are repeated.
h e obtained hydroxides were i ltered, dried and calcined at 300 C for a
short time. h e advantage of a wet chemical method over vacuum metal
deposition is that the artifacts mentioned above should be eliminated. h e
synthesis of phase-pure BiFeO
3
has been demonstrated by a chemical syn-
thesis route [65].
h in i lm of BiFeO
3
is also prepared by this method [66].
13.2.1.3 Autocombustion Technique
Powder of raw chemicals was taken and dissolved in distilled water. h en
it was placed on a hot plate for 15 minutes and then with a little stirring
the solution was obtained. h en the same molar ratio of the other solu-
tion was taken and added to the above solution. h en Citric acid (as a fuel),
