Influence of the Carbon Allotropes on Dilatometric Properties …
659
2.9·10
−3 , and 0.1·10
−3 for the Fe–Cu, Fe–Cu-MWCNT(0.5), Fe–Cu-MWCNT(1.0),
and Fe–Cu-MWCNT(2.0), respectively.
Some additive details of the dilatometry behavior of the samples under study
become better visible from the temperature variations of the thermal expansion
coefficients, CTE = α(T), (Fig. 13).
The shape of the dilatometric curves, α(T), for all four materials is different. At the
same time, there are some common features, those allowed us to select the temperature ranges similar to those noted above for the L/L 0 curves. If regarding the Fe–Cu
sample, this statement concerns the next of the temperature ranges: ~35–150, 200–
325, 325–550, 575–700, and 700–800 °C (Fig. 13, curve 1). Moreover, if compare
the data for the Fe–Cu, Fe–Cu-MWCNT(1.0), and Fe–Cu-MWCNT(2.0) samples
we see similar behavior of the α(T) curves in the ranges ~150–300, 300–600 and
600–800 °C. However, the α(T) values for Fe–Cu and Fe–Cu-MWCNT(1.0) samples
are fairly close, while for the Fe–Cu-MWCNT(2.0) sample with the largest content of
the MWCNTs, they are smaller by two orders of magnitude. The values and behavior
of the α(T) curves for the samples Fe–Cu and Fe–Cu-MWCNT(0.5) are similar in
the ranges 0–125–200°C, but α(T) dependence for the Fe–Cu-MWCNT(0.5) sample
differs radically in the range 300–600 °C from other three curves noted above. Thus,
the described situation is similar to that observed for the L/L 0 data. At the same time,
we have to emphasize that despite the similarity in general terms, there are a number
of differences within each of the selected ranges. This refers to both of the number
of features (singularities) in each of the ranges, the position of the features, and their
nature—it is a local maximum or a minimum. The data about the position and character of the singularities have been accumulated in Table 1. Taking into account the
significant, in some cases, inaccuracy of the α(T) measurement it is easy to see that
the same features are inherent in various curves. We found four singularities in the
ranges 0–125–200 °C, five singularities in the range 200–400 °C, three singularities
in the range 400–600 °C, and at least two singularities in the range 600–800 °C.
Consequently, we can assume that even in those cases where there are no distinct
peaks on the wide bands of the both L/L 0 and α(T) curves, those bands are in fact a
superposition of several strongly overlapping components. Besides, it worth to note
that number of singularities is larger for the composite samples those contain a higher
amount of the MWCNTs. We see only two features for the Fe–Cu sample in the range
0–400 °C, while there are five singularities for the Fe–Cu-MWCNT(0.5) composite,
and 8 details for the Fe–Cu-MWCNT(1.0) composite. At the same time, the number
of singularities is more stable (4–5) for the temperature range of 400–800 °C. Some
of the singularities are well pronounced, while other ones are poorly selected (like to
shoulders, see Fig. 13 and Table 1, e.g., columns 5–11). (The α(T) curve for the Fe–
Cu-MWCNT(2.0) composite is out of consideration here as measured α(T) changes
are small and close to experimental inaccuracy.) Thus, we have to state the rather
complicated temperature behavior of the L/L 0 and α(T) characteristics. The data
on the dilatometric characteristics of such composite materials are very limited in
the literature, even for the Fe–Cu samples [25, 27, 34, 45–48]. The data for Fe–
Cu composites where carbon was introduced as carbon nanotubes, according to our
information, are just given for the first time in published literature.
659
2.9·10
−3 , and 0.1·10
−3 for the Fe–Cu, Fe–Cu-MWCNT(0.5), Fe–Cu-MWCNT(1.0),
and Fe–Cu-MWCNT(2.0), respectively.
Some additive details of the dilatometry behavior of the samples under study
become better visible from the temperature variations of the thermal expansion
coefficients, CTE = α(T), (Fig. 13).
The shape of the dilatometric curves, α(T), for all four materials is different. At the
same time, there are some common features, those allowed us to select the temperature ranges similar to those noted above for the L/L 0 curves. If regarding the Fe–Cu
sample, this statement concerns the next of the temperature ranges: ~35–150, 200–
325, 325–550, 575–700, and 700–800 °C (Fig. 13, curve 1). Moreover, if compare
the data for the Fe–Cu, Fe–Cu-MWCNT(1.0), and Fe–Cu-MWCNT(2.0) samples
we see similar behavior of the α(T) curves in the ranges ~150–300, 300–600 and
600–800 °C. However, the α(T) values for Fe–Cu and Fe–Cu-MWCNT(1.0) samples
are fairly close, while for the Fe–Cu-MWCNT(2.0) sample with the largest content of
the MWCNTs, they are smaller by two orders of magnitude. The values and behavior
of the α(T) curves for the samples Fe–Cu and Fe–Cu-MWCNT(0.5) are similar in
the ranges 0–125–200°C, but α(T) dependence for the Fe–Cu-MWCNT(0.5) sample
differs radically in the range 300–600 °C from other three curves noted above. Thus,
the described situation is similar to that observed for the L/L 0 data. At the same time,
we have to emphasize that despite the similarity in general terms, there are a number
of differences within each of the selected ranges. This refers to both of the number
of features (singularities) in each of the ranges, the position of the features, and their
nature—it is a local maximum or a minimum. The data about the position and character of the singularities have been accumulated in Table 1. Taking into account the
significant, in some cases, inaccuracy of the α(T) measurement it is easy to see that
the same features are inherent in various curves. We found four singularities in the
ranges 0–125–200 °C, five singularities in the range 200–400 °C, three singularities
in the range 400–600 °C, and at least two singularities in the range 600–800 °C.
Consequently, we can assume that even in those cases where there are no distinct
peaks on the wide bands of the both L/L 0 and α(T) curves, those bands are in fact a
superposition of several strongly overlapping components. Besides, it worth to note
that number of singularities is larger for the composite samples those contain a higher
amount of the MWCNTs. We see only two features for the Fe–Cu sample in the range
0–400 °C, while there are five singularities for the Fe–Cu-MWCNT(0.5) composite,
and 8 details for the Fe–Cu-MWCNT(1.0) composite. At the same time, the number
of singularities is more stable (4–5) for the temperature range of 400–800 °C. Some
of the singularities are well pronounced, while other ones are poorly selected (like to
shoulders, see Fig. 13 and Table 1, e.g., columns 5–11). (The α(T) curve for the Fe–
Cu-MWCNT(2.0) composite is out of consideration here as measured α(T) changes
are small and close to experimental inaccuracy.) Thus, we have to state the rather
complicated temperature behavior of the L/L 0 and α(T) characteristics. The data
on the dilatometric characteristics of such composite materials are very limited in
the literature, even for the Fe–Cu samples [25, 27, 34, 45–48]. The data for Fe–
Cu composites where carbon was introduced as carbon nanotubes, according to our
information, are just given for the first time in published literature.