Biomedical Engineering Reference
In-Depth Information
9.19
Dependence of critical temperature of transition into SC state and
the width of (
T
c
-
T
f
) on the weight ratio of ceramic and polyethylene [21].
Table 9.11 Dependence of critical temperatures of transition into SC state and
the width of (T
c
-T
f
) on the weight ratio of the ceramic and polyethylene
Ceramic:polyethylene
weight ratio
T
l.c.
(K)
T
l.f.
(K)
T
m.c.
(K)
T
m.f.
(K)
T
h.c.
(K)
T
h.f.
(K)
100:0
10
4.5
~
30
~
10
46
~
30
80:20
10
4.5
~
50
10
70
~
50
50:50
79
~
63
temperature (T
l.c.
5K), which does not depend on the formula of the
composition; mid-temperature (T
m.c.
); and comparatively high temperature
(T
h.c.
), which depends appreciably on the content of polyethylene in the
nanocomposites (Table 9.11).
Different degrees of degradation in various fractions of the ceramic cause
the transition into a SC state to have a stepwise character and, accordingly,
decrease the rate of intercalation in relation to the degree of amorphization
of the ceramic grains. It is interesting to note that the beginning of the high-
temperature transition (T
h.c.
), as well as its width, substantially depend upon
the weight ratio of the composite components. As previously stated, the
observed increase in T
h.c.
and T
h.c.
-T
h.f.
can be explained by sufficient
intercalation of the separate fragments of polyethylene or co-catalyst into
the interstitial layer of the Y
1
Ba
2
Cu
3
O
6.97
during gas-phase polymerization
of the ethylene.
As in previous experiments, the SC nanocomposite containing 20m.Kt%
PE was kept in air at ambient temperatures over the course of 1 year. The
SC characteristics at 6 and 12 months showed an increase in T
c
by 5K and
~
