Additive-free carbon nanotube dispersions, pastes, gels, and doughs in cresols

Chiou, Kevin; Byun, Segi; Kim, Jaemyung; Huang, Jiaxing

doi:10.1073/pnas.1800298115

Cited by 55 publications

(40 citation statements)

References 24 publications

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“…Previous studies have shown that GO and carbon nanotubes’ dispersions of different concentrations can be divided into four states. [ 29,52 ] In our experiment, increasing GO/G concentrations results in a continuous transition between four states, from a dilute dispersion (<10 mg mL −1 ) to a thick paste (10–50 mg mL −1 ), a free‐standing gel (50–100 mg mL −1 ), and eventually, a kneadable, playdough‐like material (>100 mg mL −1 ). These four states were further transformed into 1D graphene fibers, 2D graphene films, or 3D graphene doughs using various material‐processing techniques (Figure S25, Supporting Information).…”

Section: Resultsmentioning

confidence: 99%

Graphene Oxide “Surfactant”‐Directed Tunable Concentration of Graphene Dispersion

Luo

Yang

Sun

et al. 2020

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Homogeneous graphene dispersions with tunable concentrations are fundamental prerequisites for the preparation of graphene‐based materials. Here, a strategy for effectively dispersing graphene using graphene oxide (GO) to produce homogeneous, tunable, and ultrahigh concentration graphene dispersions (>150 mg mL−1) is proposed. The structure of GO with abundant edge‐bound hydrophilic carboxyl groups and in‐plane hydrophobic π‐conjugated domains allows it to function as a special “surfactant” that enables graphene dispersion. In acidic solutions, GO sheets tend to form edge‐to‐edge hydrogen bonds and expose the π‐conjugated regions which interact with graphene, thereby promoting graphene dispersion. While in alkaline solutions, GO sheets tend to stack in a surface‐to‐surface manner, thereby blocking the π‐conjugated regions and impeding graphene dispersion. As the concentration of GO‐dispersed graphene dispersion (GO/G) increases, a continuous transition between four states is obtained, including a dilute dispersion, a thick paste, a free‐standing gel, and a kneadable, playdough‐like material. Furthermore, GO/G can be applied to create desirable structures including highly conductive graphene films with excellent flexibility, thereby demonstrating an immense potential in flexible composite materials.

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Section: Resultsmentioning

confidence: 99%

Graphene Oxide “Surfactant”‐Directed Tunable Concentration of Graphene Dispersion

Luo

Yang

Sun

et al. 2020

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“…The m-cresol is known to dissolve well highly conjugated polymer such as conducting polymer through second doping [23]. In the same way, the m-cresol interacts with the CNT by charge-transfer through the phenolic hydroxyl proton [13]. By this mechanism, m-cresol initially disperses the nanotubes well at high concentrations to produce a thick CNT paste.…”

Section: Physical and Thermal Propertiesmentioning

confidence: 99%

“…A macronization of nanoparticles, such as the CNT particles, can generally be achieved by the solvent-based strategies for dispersion and processing of the particles. However, some types of solvents for the direct dilution such as 1,2-dichrolobenzene [11], dimethylformamide (DMF) [12] and N-methyl-2-pyrrolidone (NMP) [12] can disperse the nanotubes less than 0.02 wt %, indicating extensive solvents treating and uneconomical efforts in the process of the CNT macronization [13]. Most of the studies have used single-walled CNTs (SWCNTs) for their application in the electronic device [11][12][13].…”

Section: Introductionmentioning

confidence: 99%

“…However, density control of the MWCNT was rarely reported and the work is still challenging [14]. Recently, Chiou et al [13] reported a CNT dispersion method using cresols as a processing solvent, where m-cresol can disperse the CNT powder at high concentration up to tens of wt % without any dispersing agent. Their study demonstrated a few proofs such as thread and film from thick paste, showing a possibility in densification of the CNT powder [13].…”

Section: Introductionmentioning

confidence: 99%

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Preparation of MWCNT Microbeads for the Application of Bed Materials in a Fluidized Bed Heat Exchanger

Lee

Kim

2020

Materials

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Fluidized beds have been utilized for various chemical and physical applications including heat transfer such as the gas–solid heat exchanger. It is advantageous to use carbon nanotubes (CNTs) with high thermal conductivity as bed materials for heat transfer enhancement in a direct gas–solid contacting heat exchanger. However, the poor fluidization of CNTs is the biggest challenge due to the strong cohesive force between the particles. A control over the macroscopic shapes of CNT powders is required for their application. A preparation method of CNT microbeads has been proposed to be suitable for fluidized bed applications. The method is characterized by using m-cresol known as processing solvents for fabrication of the CNT microbeads. Multiwalled CNT powders were directly mixed with m-cresol to yield a thick paste-like material. The paste droplets were rolled into round particles with in pure water with and without surfactant. The obtained particles were dried in a vacuum oven. The obtained microbeads have diameters ranging 300–2200 μm and apparent particle density of 350–400 kg/m3, which corresponds to Geldart group B in the fluidization classification. The micrograph of the CNT microbeads exhibited stacked nanotubes array on the surface, indicating obvious densification of the raw CNT powders. The microbeads prepared in water containing surfactant have better shape factor such as circularity and solidity. The thermal conductivity of the microbeads is about 1.18 W/mK in a bulk state, which is much higher than raw CNT powder (0.032 W/mK). The flowability and fluidization characteristics of the multiwalled CNT (MWCNT) microbeads showed a possibility as promising bed material suitable for the fluidized bed heat exchanger.

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“…There are a lot of experiments done with most common solvents to get stable dispersions of CNTs (Fukushima et al, 2003;Bergin et al, 2009;Davis et al, 2009); however, generally the most common solvents used, such as N-methyl-2-pyrrolidone, dimethylformamide, and 1,2-dichrolobenzene, can disperse only CNTs with specific size and dimension at low concentrations. Recently, Chiou et al (2018) dispersed carbon nanotube powders in m-cresol at very high concentrations giving them a doughlike consistency. However, m-cresol is highly volatile, and the processing requires a controlled environment.…”

Section: Introductionmentioning

confidence: 99%

Regenerated Silk and Carbon Nanotubes Dough as Masterbatch for High Content Filled Nanocomposites

et al. 2019

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Regenerated silk (RS) is a natural polymer that results from the aggregation of liquid silk fibroin proteins. In this work, we observed that RS dispersed in aqueous solution undergoes a reversible solid/liquid transition by programmed heating/cooling cycles. Fourier transform infrared, atomic force microscopy imaging and Raman measurements of the RS reveal that the transition from random coil to β-sheet structures is involved in this liquid-solid transition. The reversible solid-liquid transition of silk fibroin was then found to be helpful to prepare polymer-like carbon nanotube (CNT) dispersions. We demonstrate that the gelation of RS makes the CNTs with the consistency of a dough with polymeric behavior. Such RS can disperse carbon nanotubes at high concentrations of tens of weight percent. Finally, such carbon nanotube dough has been used for the realization of rubber composites. With this method, we pave the way for handling nanopowders (e.g. CNTs or graphene related materials) with safety and reducing the filler volatility that is critical in polymer-processing.

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Additive-free carbon nanotube dispersions, pastes, gels, and doughs in cresols

Cited by 55 publications

References 24 publications

Graphene Oxide “Surfactant”‐Directed Tunable Concentration of Graphene Dispersion

Graphene Oxide “Surfactant”‐Directed Tunable Concentration of Graphene Dispersion

Preparation of MWCNT Microbeads for the Application of Bed Materials in a Fluidized Bed Heat Exchanger

Regenerated Silk and Carbon Nanotubes Dough as Masterbatch for High Content Filled Nanocomposites

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