Dispersion Stability Of Carbon Nanotubes Research Articles

Dispersion Stability of Carbon Nanotubes and Their Impact on Energy Storage Devices

Carbon nanotubes (CNTs), with their extraordinary combination of mechanical, electrical, and thermal properties, have emerged as a revolutionary class of nanomaterials with immense potential in energy storage and harvesting devices. Realizing this potential hinges on a fundamental challenge: the dispersion stability of CNTs within various matrices. This review paper provides a comprehensive exploration of the critical interplay between CNT dispersion stability and its far-reaching implications for the performance of energy storage and harvesting technologies. By delving into the underlying mechanisms of dispersion, the strategies to achieve stability, and the direct effects on device functionality, this review sheds light on the intricate relationship between nanotube dispersion and the advancement of energy-related applications.

The thermal conductivity improvements of phase change materials using modified carbon nanotubes

This paper describes a new method of modified carbon nanotubes (CNTs) by ethylene grafting or silicon coating. The thermal conductivity of paraffin is enhanced by the modified CNTs. The influence of modification on the dispersion stability of CNTs and the thermal conduction performance of paraffin are studied. Fourier transform infrared spectroscopy, scanning electron microscopy, thermal constant analyzer are used to analyze the composites. The results indicate that CNTs have been modified successfully. The dispersion stability of CNTs is significantly improved by polyethylene grafting or silicon coating. The thermal conductivity of paraffin phase change material is enhanced by 84.6% with the modified CNTs. The prepared paraffin/CNTs phase change materials show good thermal conductivity.

Novel Terahertz Spectroscopy Analysis for the Electrode with Carbon Nanotubes (CNTs) in Lithium-Ion Batteries

In this study, to use carbon nanotubes (CNTs) as a conductive material instead of carbon black in cathode electrodes, their dispersions were prepared in 1-Methyl-2-pyrrolidinone (NMP) solvent by using an ultrasonic horn, and their dispersion stability was analyzed using CNTs on the formation of the network between cathode electrode constituent materials comprised of cathode material, CNTs, and current collectors, and their correlation with electrochemical performance results were investigated using various analytical techniques. Particularly, in the analysis, terahertz time domain spectroscopy (THz-TDS), a new non-destructive analysis method, was used to analyze and compare the various optical properties of the cathode’s slurries that co-existed with CNTs and cathode material, suggesting the suitability of its analytical use in the field of materials dispersion and the slurry manufacturing process for lithium-ion batteries (LIBs). In the investigated results, the sample with the highest dispersion stability of CNTs uniformly formed the networks of CNTs and cathode material in the electrode, which results in the highest electrical conductivity among all samples, and as a result, the best performance in electrochemical evaluations.

Succinylated β-Lactoglobuline-Functionalized Multiwalled Carbon Nanotubes with Improved Colloidal Stability and Biocompatibility.

PEGylation (i.e., attachment of polyethylene-glycol) of carbon nanotubes (CNTs) is one of the most widely used strategies to improve its biocompatibility and aqueous dispersion stability, which are critical for their successful clinical application. However, PEGylation of nanomaterials has recently been associated with production of anti-PEG antibody, low cellular uptake, and degradation. Herein, we explore surface functionalization of CNTs using the bovine-milk-derived protein succinylated β-lactoglobuline (Sblg) as an alternative strategy to PEGylation. The aqueous dispersion stability, in vitro cell uptake and biocompatibility of Sblg-functionalized multiwalled CNTs (Sblg-f-MWCNTs) was compared to PEGylated MWCNTs (PEG-f-MWCNTs). The surface functionalization with Sblg was found to improve the IC50 values of CNTs by ∼5- to 6-fold in comparison with pristine CNTs in various cell lines. Both Sblg-f-MWCNTs and PEG-f-MWCNTs improved the aqueous colloidal stability of CNTs, which remained suspended for a period of one month. Our study concluded that the Sblg provides a cost-effective alternative to the PEG-based CNT functionalization with significant improvement in the biocompatibility and dispersion stability of CNTs.

Dispersibility and dispersion stability of carbon nanotubes in synthetic aquatic growth media and natural freshwater

The dispersion behavior of carbon nanotubes (CNTs) is influenced by both their physicochemical properties and by the aqueous media properties (e.g. ionic strength, presence of divalent cations and natural organic matter) in which they are dispersed. In the current study, the dispersibility and dispersion stability of four multi-walled CNTs (MWCNT) and a single walled CNT (SWCNT) with different physicochemical properties were investigated in three freshwater growth media (with and without natural organic matter; NOM) used in algae and daphnia ecotoxicity studies. CNT dispersion behavior was also investigated in a natural freshwater for comparison. SWCNTs and non-functionalized MWCNTs showed similar dispersibility irrespective of the media type (SWCNTs = 0.5–0.9 mg/L; MWCNTs = 1.5–2.8 mg/L). Functionalized MWCNTs exhibited higher dispersion concentrations, but were more dependent upon the ionic strength and divalent cation concentration of each media (MWCNT-COOH = 3.0–6.6 mg/L). In contrast, CNT surface oxygen content had no influence on CNT dispersibility in the natural water (all MWCNTs = 0.9–1.4 mg/L). Functionalized MWCNTs were affected more by the differences in media properties than non-functionalized MWCNTs. The dispersed CNT concentration decreased over time for all CNT types and in all media due to sedimentation, but was influenced by both CNT and media properties. The study shows how a complex interplay between CNT and media properties can influence the environmental fate of CNTs. Furthermore, the study demonstrates how different CNT types and/or ecotoxicological media in aquatic tests influences the dispersion behavior of the CNTs, and thus their exposure and toxicity to aquatic organisms.

A settling curve modeling method for quantitative description of the dispersion stability of carbon nanotubes in aquatic environments.

Understanding the aggregation and deposition behavior of carbon nanotubes (CNTs) is of great significance in terms of their fate and transport in the environment. Attachment efficiency is a widely used index for well-dispersed CNT solutions. However, in natural waters, CNTs are usually heterogeneous in particle size. The attachment efficiency method is not applicable to such systems. Describing the dispersion stability of CNTs in natural aquatic systems is still a challenge. In this work, a settling curve modeling (SCM) method was developed for the description of the aggregation and deposition behavior of CNTs in aqueous solutions. The effects of water chemistry (natural organic matter, pH, and ionic strength) on the aggregation and deposition behavior of pristine and surface-functionalized multi-walled carbon nanotubes (MWCNTs) were systematically studied to evaluate the reliability of the SCM method. The results showed that, as compared to particle size and optical density, the centrifugal sedimentation rate constant (ks) from the settling curve profile is a practical, useful and reliable index for the description of heterogeneous CNT suspensions. The SCM method was successfully applied to MWCNT in three natural waters. The constituents in water, especially organic matter, determine the dispersion stability of MWCNTs in natural water bodies.

Effects of surface modification on the dispersion and thermal conductivity of CNT/water nanofluids

In the present work, effects of different surface modification methods (surfactant, acid, base, amide, sulfate) on multi walled carbon nanotubes (CNTs) are studied. The dispersion stability of CNTs in aqueous media was confirmed and the effects of the type of treatment on the thermal conductivity of CNT/water nanofluids were investigated. The surface of the CNTs was modified with acid mixtures (H2SO4–HNO3), potassium persulfate (KPS), tetrahydrofuran (THF), octadecylamine and sodium dodecyl sulfate (SDS). UV–visible spectral data indicate that the CNTs treated first with the acid mixture and then with KPS show the best dispersion stability. The basic treatment and SDS treated CNT/water nanofluids (SDS-KCNT/water) showed the highest conductivity of 0.765W/mK which increases 24.9% of water as a base fluid conductor.

Enhancement of Dispersion Stability of Carbon Nanotube in Solvents

Dispersion stability of carbon nanotubes (CNTs) is a challenging issue in the preparation of nanocomposites. This paper reports the enhancement of dispersion stability of multiwall carbon nanotubes (MWCNTs) in four solvents using two surfactants and four polymeric dispersants. The dispersion stability of MWCNTs, in term of Instability Index, was characterized by an accelerated stability analyser. The two polymeric dispersants with ionic anchoring groups and solvent-compatible chains showed the best dispersion stability as they provide polar anchoring and steric barrier which enhance the dispersion stabilisation of MWCNTs in various solvents.

Significance of the Dispersion Stability of Carbon Nanotubes on the Thermal Conductivity of Nylon 610 Nanocomposite

Herein, the effect of the dispersion uniformity of multi-wall carbon nanotubes (MWNTs) on the thermal conductivity of nylon 610/MWNTs nanocomposite was investigated. Compared to raw MWNTs, the carboxylated MWNTs (MWNT-COOH) were well dispersed in aqueous hexamethylenediamine solution and the dispersion stability was further improved by the presence of poly(vinyl alcohol). By means of interfacial polymerization between the aqueous hexamethylenediamine solution containing the MWNTs and a sebacoyl chloride phase, nylon 610/MWNT composites were prepared. It was found that the stable dispersion state of MWNTs in aqueous solutions greatly improved the thermal conductivity of the ultimate nanocomposites. It is noted that the thermal conductivity of nylon 610/MWNT-COOH/PVA nanocomposite was 135% higher than that of nylon 610/raw MWNTs for the same 0.1 wt% content of MWNTs.

Mixed surfactant system for stable suspension of multiwalled carbon nanotubes

The dispersion stability of carbon nanotubes in water and organic solvents is a challenging task for their utilization in nanoscale devices. Multiwalled carbon nanotubes (MWNTs) have been tested with different chemical functionalities of the side groups for their dissolution in organic solvents. Herein, we investigated the dispersive effects achieved by surface-active agents on MWNTs. Dodecyl trimethylammonium bromide (DTAB) and sodium octanoate (SOCT) were found to form exceptionally stable MWNT dispersions. In this study, a novel method was developed to prepare highly dispersed MWNTs using the mixtures of cationic surfactant DTAB and anionic surfactant SOCT. Stable dispersions were obtained at low total surfactant concentration as compared to their concentration when used alone. Zeta potential was confirmed to understand the surface charge-related stability of the nanotubes solutions. The dispersion of MWNTs has been characterized by scanning electron microscopy (SEM). Raman spectroscopy and transmission electron microscopy (TEM) showed non-covalent interaction of MWNTs and surfactants.