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. 2021 May 18;11(5):1323.
doi: 10.3390/nano11051323.

Effects of Functionalization in Different Conditions and Ball Milling on the Dispersion and Thermal and Electrical Conductivity of MWCNTs in Aqueous Solution

Baasandulam Tserengombo  1 , Hyomin Jeong  2 , Erdenechimeg Dolgor  3 , Antonio Delgado  4   5 , Sedong Kim  4
Affiliations

Effects of Functionalization in Different Conditions and Ball Milling on the Dispersion and Thermal and Electrical Conductivity of MWCNTs in Aqueous Solution

Baasandulam Tserengombo et al. Nanomaterials (Basel). .

Abstract

In this work, the effects of a functionalization method involving different conditions and milling processes on the dispersion and thermal and electrical conductivity of multiwalled carbon nanotubes were studied. The surfaces of MWCNTs were modified using a mixture of sulfuric and nitric acid as an acid treatment and potassium persulfate and sodium hydroxide as an alkaline treatment to achieve more hydrophilic MWCNTs. The morphological and structural investigations were carried out using transmission electron microscopy and Fourier transform infrared spectroscopy. Furthermore, the dispersion characteristics and thermal and electrical conductivity of the as-prepared water-based nanofluids were measured. As a result, the dispersion characteristics revealed that the best dispersion and stability results were obtained for alkaline-treated MWCNTs using potassium persulfate and sodium hydroxide. The thermophysical study using a thermal conductivity analyzer exhibited that the thermal conductivity of the pristine MWCNT nanofluid (0.1 wt%) was enhanced from 603.5 to 610.4 mW/m·K and the electrical conductivity of the raw MWCNT nanofluid was increased from 16.2 to 125.8 μS/cm at 25 °C after alkaline treatment and milling processes, which were performed using planetary ball milling. Regarding the overall results, the milling process and mild alkaline oxidation process are more environmentally friendly, effective, and convenient for the functionalization of CNTs, without requiring any organic solvents or strong acids.

Keywords: MWCNTs; alkaline treatment; dispersion; functionalization; thermal conductivity.

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Conflict of interest statement

The authors declare no conflict of interest.

Figures

Figure 1
Figure 1
Schematic of the treatment processes.
Figure 2
Figure 2
TEM images of the raw and functionalized MWCNTs: (A) raw CNT; (B) A-CNT; (C) K-CNT.
Figure 3
Figure 3
FTIR spectra of pristine and functionalized MWCNTs: (A) raw CNT; (B) A-CNT; (C) K-CNT.
Figure 4
Figure 4
UV-Vis spectra (A) and zeta potential (B) comparison of non-ground and ground MWCNT nanofluids for raw and functionalized MWCNTs.
Figure 5
Figure 5
Photographs of pristine and functionalized MWCNT nanofluids for non-ground and ground MWCNTs: (A) raw CNT; (B) A-CNT; (C) K-CNT; (1) after sonication; (2) after 7 days; (3) after 30 days.
Figure 6
Figure 6
Thermal conductivity measurements of distilled water: experimental data and reference data.
Figure 7
Figure 7
Thermal conductivity of non-ground (A), ground and non-ground (B) MWCNT nanofluids for pristine and functionalized MWCNTs.
Figure 8
Figure 8
Electrical conductivity of non-ground (A), ground and non-ground (B) MWCNT nanofluids for pristine and functionalized MWCNTs.
See this image and copyright information in PMC

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