Biomedical Engineering Reference
In-Depth Information
processes improve the compaction process to produce high-performance
MMNCs. A microwave-assisted sintering process has shown improvements
to the mechanical properties of MMCs (Gupta and Wong, 2005). Tun and
Gupta (2007) use a microwave-assisted rapid sintering technique coupled
with hot extrusion to fabricate magnesium nanocomposites with nano-yttria
as reinforcement. The results show that even though the microwave assisted
the compaction process, the mechanical properties of the MMNCs did not
improve significantly (Tun and Gupta, 2007).
Even though the solid-phase methods are the most frequently used to
fabricate nanoparticulate-enhanced MMNCs, there are still some unsolved
problems.
.
Powder contamination results from the fracture and reaction process of
powders during the milling process. Some measures have been taken to
avoid contamination of particles, for example using coated milling balls,
but the problem is still not thoroughly solved.
.
Procedures are complex.
.
There is a lack of scientific theory, with no model to explain the whole
process (Sherif and Eskandarany, 1998)
.
The process is harder to control due to the many process parameters
involved.
Two-phase MMNC ex-situ fabrication processes
Two-phase processes mostly involve producing MMNC powders by a liquid
method and then consolidating them in a solid phase. Paramsothy et al.
(2011a, 2011b) reported a novel method of disintegrated melt deposition
(DMD) + hot extrusion. In that research, mechanical stirring was used to
mix CNT powder and superheated ZK60A melt. Two jets of argon were
used to disintegrate the melt when the mixed melt was pouring from a small
orifice. The disintegrated melt slurry was subsequently deposited on a
substrate. Hot extrusion was then used to consolidate the deposited ingot.
Hassan (2011) compared the mechanical properties of Y
2
O
3
/Mg nanocom-
posite fabricated by DMD and powder metallurgy. Metal matrix hardness,
UTS, and ductility were all improved by adding Y
2
O
3
. DMD-processed
material exhibited superior overall mechanical properties while material
processed by powder metallurgy exhibited excellent ductility and work of
fracture.
Thermal spray methods are used to form MMNCs. Laha et al. (2004)
used plasma spray forming for an aluminum nanocomposite and the
mechanical properties were tested. The nanocomposite had higher hardness
and elastic modulus but lower ductility than the monolithic metal. Mazaheri
et al. (2011) used high-velocity oxygen fuel spraying to deposit particles on a
