Biomedical Engineering Reference
In-Depth Information
7.19
2.5wt% MWCNT-SiO
2
composites after thermal shock test from
(a) 1000
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C and (b) 1200
8
C. No cracks can be seen in specimen quenched
from 1000
8
C while the specimen quenched from 1200
8
C showed cracks
due to the formation of cristobalite.
7.20
2.5wt% MWCNT-SiO
2
composites after thermal shock test
comprising 20 cycles from 1000
C. Cracks can be seen on (a) surface and
(b) cross-section of the specimen due to cristobalite formation because
of thermal cycling.
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20 times, did not lead to failure of the composites due to thermal shock but
it encouraged devitrification in silica glass. Figure 7.20 shows images of the
surface and cross-section of CNT-SiO
2
composites thermally cycled up to
1000
C, 20 times; surface cracks only formed due to the crystallization of
cristobalite at 1000
8
C on repeated heating of the specimens. It can be
inferred from the results on CNT-SiO
2
composites that the incorporation of
CNTs is likely to increase thermal shock resistance when reinforced in glass
systems susceptible to thermal shock.
Thermal ageing of CNT-glass/glass-ceramic composites is another
important area of research in order to find the maximum working
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