654
M. C. Bouleklab et al.
their known mechanical characteristics, which exceeded the characteristics of such
composites with other Fe–Cu and MWCNT ratios [33, 37, 40, 41].
The results of the study of the dilatometric and calorimetric characteristics were
analyzed in terms of the MWCNT influence on the structure and morphology of
the samples. Data on the latter were obtained by monitoring the made composites
by the X-ray diffraction, Raman and IR spectroscopy, optical and scanning electron
microscopy.
The obtained data allowed us to draw conclusions about the processes of thermal
expansion of Fe–Cu composites and mechanisms of carbon nanotubes influence
on them. The results of this work can be the basis for making recommendations
on the technological procedures for the Fe–Cu-MWCNT composites producing for
practical use.
4.1 Sample Preparation and Methods
Multi-walled carbon nanotubes (TU U24.1-03291669-009:2009) were synthesized
by us by means of the chemical vapor deposition procedure in a rotating reactor
[42]. Their resulting characteristics were: average diameter—between 10 and
20 nm; specific surface area (determined through Ar—adsorption)—between 200
and 400 m
2 /g; bulk density—between 20 and 40 g/dm
3 [43, 44]. The charge was
made of IP-1 (GOST 9849–86) iron and PMS-1 (GOST 4960–2009) copper powders
in a 4:1 weight ratio. These powders were mixed with MWCNT of concentrations
0.5, 1.0, and 2.0% in volume. After processing in the ball mill the composites were
subjected to a 40% compression followed by annealing at 950 °C for 30 min in
Argon flow. Then, the powder samples were subjected to cold rolling followed with
annealing at 900 °C in Argon flow. The described cycle was repeated three times;
thus, the samples were ultimately undergone to 80% thinning. Finally, the thickness
of the obtained ribbons was near of 0.3 mm. The temperature behavior of some
physical characteristics of the made composites, which were named here and before
as Fe–Cu, Fe–Cu-CNT(0.5), Fe–Cu-CNT(1.0), and Fe–Cu-CNT(2.0), was studied
using dilatometry and calorimetry technique. Structural characteristics and composition of the samples were monitored by X-ray diffraction, Raman scattering, and IR.
The next equipment was used to perform mentioned studies: the NETZSCH 402C
dilatometer (NETZSCH, Selb, Germany) with 3% of accuracy. The heating rate was
near 10 °C/min. The thermal expansion coefficients were measured in the temperature
range from 30 to 800 °C. Differential scanning calorimetry (DSC) test was performed
using the Jupiter STA 449 F3 NETZSCH calorimeter (NETZSCH, Selb, Germany).
The same heating rate was applied as under dilatometric measurements. The X-ray
diffraction patterns of composites under study were obtained using the automated
DRON-4.0 diffractometer with the filtered cobalt radiation Kα = 1.7909 Å under the
following scanning parameters: monitoring range 2 h = (40–130), step scan of 0.05,
and counting time per step at 3 s. The collecting of the diffraction data was performed
by a full-profile analysis using the program providing the experimental diffraction
M. C. Bouleklab et al.
their known mechanical characteristics, which exceeded the characteristics of such
composites with other Fe–Cu and MWCNT ratios [33, 37, 40, 41].
The results of the study of the dilatometric and calorimetric characteristics were
analyzed in terms of the MWCNT influence on the structure and morphology of
the samples. Data on the latter were obtained by monitoring the made composites
by the X-ray diffraction, Raman and IR spectroscopy, optical and scanning electron
microscopy.
The obtained data allowed us to draw conclusions about the processes of thermal
expansion of Fe–Cu composites and mechanisms of carbon nanotubes influence
on them. The results of this work can be the basis for making recommendations
on the technological procedures for the Fe–Cu-MWCNT composites producing for
practical use.
4.1 Sample Preparation and Methods
Multi-walled carbon nanotubes (TU U24.1-03291669-009:2009) were synthesized
by us by means of the chemical vapor deposition procedure in a rotating reactor
[42]. Their resulting characteristics were: average diameter—between 10 and
20 nm; specific surface area (determined through Ar—adsorption)—between 200
and 400 m
2 /g; bulk density—between 20 and 40 g/dm
3 [43, 44]. The charge was
made of IP-1 (GOST 9849–86) iron and PMS-1 (GOST 4960–2009) copper powders
in a 4:1 weight ratio. These powders were mixed with MWCNT of concentrations
0.5, 1.0, and 2.0% in volume. After processing in the ball mill the composites were
subjected to a 40% compression followed by annealing at 950 °C for 30 min in
Argon flow. Then, the powder samples were subjected to cold rolling followed with
annealing at 900 °C in Argon flow. The described cycle was repeated three times;
thus, the samples were ultimately undergone to 80% thinning. Finally, the thickness
of the obtained ribbons was near of 0.3 mm. The temperature behavior of some
physical characteristics of the made composites, which were named here and before
as Fe–Cu, Fe–Cu-CNT(0.5), Fe–Cu-CNT(1.0), and Fe–Cu-CNT(2.0), was studied
using dilatometry and calorimetry technique. Structural characteristics and composition of the samples were monitored by X-ray diffraction, Raman scattering, and IR.
The next equipment was used to perform mentioned studies: the NETZSCH 402C
dilatometer (NETZSCH, Selb, Germany) with 3% of accuracy. The heating rate was
near 10 °C/min. The thermal expansion coefficients were measured in the temperature
range from 30 to 800 °C. Differential scanning calorimetry (DSC) test was performed
using the Jupiter STA 449 F3 NETZSCH calorimeter (NETZSCH, Selb, Germany).
The same heating rate was applied as under dilatometric measurements. The X-ray
diffraction patterns of composites under study were obtained using the automated
DRON-4.0 diffractometer with the filtered cobalt radiation Kα = 1.7909 Å under the
following scanning parameters: monitoring range 2 h = (40–130), step scan of 0.05,
and counting time per step at 3 s. The collecting of the diffraction data was performed
by a full-profile analysis using the program providing the experimental diffraction