Research Information System
DIAMOND AND RELATED MATERIALS, vol.150, no.111739, pp.1-18, 2024 (SCI-Expanded)
In the preparation of nanocomposites, the agglomeration of multi-walled carbon nanotubes (MWCNTs) in the
composite due to their low colloidal stability limits their use in industrial areas. To overcome these problems, it is
important to develop simpler, economical, high-yield and non-hazardous techniques to replace existing techniques
with low yields, expensive additional equipment or hazardous liquids. This study explores how surfactants
affect the macrodispersion of thermal stress-modified MWCNTs in cryogenic environments, focusing on their
application in polymer film preparation. Firstly, optimal conditions for modifying MWCNTs through thermal
stress were identified using liquid nitrogen. Parameters assessed included the number of cycles (2, 4, and 6),
duration in liquid nitrogen (10, 20, and 30 min), and subsequent waiting time at room temperature (5, 12, and
20 min). Results showed that the highest surface area was obtained with 2 cycles, 20 min in liquid nitrogen, and
5 min at room temperature. Analytical techniques such as Brunauer-Emmett-Teller (BET), X-Ray Diffraction
(XRD), High Contrast Transmission Electron Microscopy (CTEM) and Raman spectroscopy were used to evaluate
the functionalization process's effects on MWCNTs' internal graphitic structure and physicochemical properties.
CTEM micrographs indicated that thermal stress reduced the length of MWCNTs, while Raman analysis showed
improved graphite quality. The modification process, carried out with 100 % efficiency and no sample loss,
increased the BET surface area from 297.551 m2/g to 397.295 m2/g. The study also investigated the impact of
surfactants (polyethylene glycol sorbitan monooleate-Tween 80, sodium dodecyl sulfate-SDS, and hexadecyltrimethylammonium
bromide-CTAB) on MWCNTs' macrodispersion degrees (DM%) and energy band gaps via
UV–visible (UV–Vis) absorption spectroscopy. CTAB provided the highest and most stable macrodispersion,
reducing the energy band gaps of MWCNTs from 5.65–5.75 eV to 3.53–3.60 eV. CTAB showed excellent colloidal
stability with a zeta potential of 44.2 mV, while SDS had 49.9 mV. Polyvinyl alcohol (PVA) polymer films,
created using MWCNT solutions with optimal macrodispersion, were confirmed by Scanning Electron Microscope
(SEM), Fourier Transform Infrared Spectroscopy (FTIR), Differential Scanning Calorimeters (DSC), and BET
surface area analyses to have successfully and homogeneously incorporated MWCNTs. In addition to the superior
properties of MWCNTs modified with the functionalization technique developed within the scope of this study by
increasing their specific surface area and porosity, the excellent colloidal stability provided may have various
effects in many industrial areas. These advantages enable MWCNTs functionalized with the developed technique
to have a wider range of applications in industrial applications and provide more efficient and sustainable
solutions.