Biomedical Engineering Reference
In-Depth Information
more homogenously distributed. Therefore, an improved reinforcement-
matrix interface bond can be achieved. In-situ processing is also more cost
effective compared to most ex-situ routes. The shortcoming of this
technique is the complex reaction process. Most of the structure of
reinforcement is hard to control. Also, the selection of the reinforcement
material is limited. For example, composites with nanosized hard phases
with high energy of formation (e.g. SiC, WC, B
4
C) are difficult to produce
in-situ.
6.5
Future trends
Different kinds of methods have been used to fabricate MMNCs. Some of
the most exciting attributes of MMNCs are:
.
potentially improved performance in terms of strength, hardness, and
wear resistance
.
elimination of some expensive heat-treatment steps
.
large range of material compositions available
.
consolidation route based on commercially affordable processes
.
fundamental mechanistic behavior similar to conventional engineering
metallics.
However, the fabrication of MMNCs is much more complex than the
fabrication of MMCs. When particles scale down from microlevel to the
nanolevel, the major challenges are as follows.
.
The reaction process between the bonding interface is still unclear.
.
There is a lack of understanding about the strengthening mechanisms.
When the reinforcements scale to nanolevel, new strengthening
mechanisms are needed to explain the enhancement theory.
.
Different processes have been applied but modeling of these processes is
needed.
.
Agglomeration and clustering in bulk materials can still be observed.
Dispersion during processing needs to be optimized.
.
Currently, only low-volume fabrication methods are observed. A
transition to high-volume and high-rate fabrication is pivotal
to
applying the technology to real industry fabrication.
.
Cost effectiveness is another factor that hinders the fabrication of
nanocomposites.
6.6
References
Ajayan P M, Schadler L S, and Braun P (2003), Nanocomposite science and
technology, London, Wiley-VCH.
