Biomedical Engineering Reference
In-Depth Information
silicate powders, it is necessary to select proper chemicals, synthesis method,
and control reaction conditions. To our knowledge, the sol-gel method is
more suitable for the synthesis of the ternary-oxide and quaternary-oxide
silicate powders than other methods (Wu and Chang, 2004, 2007, forthcom-
ing; Wu, Ramaswamy, Soeparto, et al. 2008; Zreiqat et al. 2010). In addition,
the calcining temperature for the sol-gel method is much lower than that for
the solid-reaction method.
For preparation of dense silicate ceramic bulks, the conventional pressure-
less sintering technique was mostly selected. It is difficult to completely sin-
ter silicate bioceramics with high density by using conventional sintering
technique (see Figure 2.2) (Wu, Chang, Ni, et al. 2006). The main reason is
that the calcining temperature to synthesize most of silicate powders is rela-
tively high (>1000°C), which results in the crystal growth of silicate powders
and in turn influences the density of ceramic bulks. We used a special sinter-
ing method, spark plasma sintering (SPS) (Long et al. 2006), to prepare dense
silicate ceramics, and their density reached 99%.
Silicate bioceramics, such as wollastonite (CaSiO
3
), diopside (CaMgSi
2
O
6
),
akermanite (Ca
2
MgSi
2
O
7
), bredigite (Ca
7
MgSi
4
O
16
), and nagelschmidtite
(Ca
7
Si
2
P
2
O
16
), have been prepared as three-dimensional (3D) porous scaffolds
for bone tissue engineering applications (Lin et al. 2004; Ni et al. 2006; Wu,
Chang, Zhai, et al. 2006; Wu, Chang, et al. 2007; Wu, Ramaswamy, Boughton,
et al. 2008; Wu et al. 2010). There are three main techniques to prepare silicate
bioceramic scaffolds. The first silicate bioceramic scaffold was prepared by
the porogen method. Lin et al. (2004) prepared CaSiO
3
scaffolds by using
polyethylene glycol (PEG) particulates. Although the prepared scaffolds
FIGURE 2.2
Akermanite (Ca
2
MgSi
2
O
7
) bioceramics prepared by the pressureless sintering technique.
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