During the past 20
years, multiwall carbon nanotubes (MWCNTs) have become an important industrial material. Hundreds of tons are produced each year. This review is a survey of the scientific ...literature, motivated by industrial requirements and guidelines for environment, health and safety compliance. Sampling, size, area, density, color, crystallinity, as well as purity compared to properties of non-MWCNT carbon and catalyst metals, are presented. No single measurement tool provides a complete characterization; therefore, we summarize methods that include scanning electron microscopy, transmission electron microscopy (TEM), fast Fourier transform of high-resolution TEM, Raman spectroscopy, reflectance and thermogravimetric analysis. Fourier transform infrared spectroscopy reveals information with regard to functional groups interacting the tube surface. Brunauer–Emmett–Teller (BET) analysis is reviewed as the basis for evaluating specific surface area. We extend the review by presenting taxonomy of defects present in MWCNTs. Finally, we provide an appendix from documentary standards that are pertinent and reasonable for bulk measurements.
Hypothetical model of SWCNT- or MWCNT-induced pulmonary and pleural inflammation.
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•Short SWCNTs induced persistent pulmonary inflammation over a 90-day period following ...instillation.•Pulmonary inflammation after short MWCNT instillation decreased in a time-dependent manner.•MWCNT instillation induced greater levels of pleural inflammation than did short SWCNTs.•Short SWCNTs and MWCNTs underwent lymphatic drainage to the mediastinal lymph nodes after pleural penetration.•The extent and time-dependent changes of pulmonary and pleural inflammation differed following SWCNT and MWCNT instillations.
Relationships between the physical properties of carbon nanotubes (CNTs) and their toxicities have been studied. However, little research has been conducted to investigate the pulmonary and pleural inflammation caused by short-fiber single-walled CNTs (SWCNTs) and multi-walled CNTs (MWCNTs). This study was performed to characterize differences in rat pulmonary and pleural inflammation caused by intratracheal instillation with doses of 0.15 or 1.5mg/kg of either short-sized SWCNTs or MWCNTs. Data from bronchoalveolar lavage fluid analysis, histopathological findings, and transcriptional profiling of rat lungs obtained over a 90-day period indicated that short SWCNTs caused persistent pulmonary inflammation. In addition, the short MWCNTs markedly impacted alveoli immediately after instillation, with the levels of pulmonary inflammation following MWCNT instillation being reduced in a time-dependent manner. MWCNT instillation induced greater levels of pleural inflammation than did short SWCNTs. SWCNTs and MWCNTs translocated in mediastinal lymph nodes were observed, suggesting that SWCNTs and MWCNTs underwent lymphatic drainage to the mediastinal lymph nodes after pleural penetration. Our results suggest that short SWCNTs and MWCNTs induced pulmonary and pleural inflammation and that they might be transported throughout the body after intratracheal instillation. The extent of changes in inflammation differed following SWCNT and MWCNT instillation in a time-dependent manner.
Despite their high theoretical specific capacity (1675 mA h g−1), the practical application of Li–S batteries remains limited because the capacity rapidly degrades through severe dissolution of ...lithium polysulfide and the rate capability is low because of the low electronic conductivity of sulfur. This paper describes novel hierarchical yolk–shell microspheres comprising 1D bamboo‐like N‐doped carbon nanotubes (CNTs) encapsulating Co nanoparticles (Co@BNCNTs YS microspheres) as efficient cathode hosts for Li–S batteries. The microspheres are produced via a two‐step process that involves generation of the microsphere followed by N‐doped CNTs growth. The hierarchical yolk–shell structure enables efficient sulfur loading and mitigates the dissolution of lithium polysulfides, and metallic Co and N doping improves the chemical affinity of the microspheres with sulfur species. Accordingly, a Co@BNCNTs YS microsphere‐based cathode containing 64 wt% sulfur exhibits a high discharge capacity of 700.2 mA h g−1 after 400 cycles at a current density of 1 C (based on the mass of sulfur); this corresponds to a good capacity retention of 76% and capacity fading rate of 0.06% per cycle with an excellent rate performance (752 mA h g−1 at 2.0 C) when applied as cathode hosts for Li–S batteries.
Hierarchical yolk–shell microspheres comprising 1D bamboo‐like N‐doped carbon nanotubes (CNTs) encapsulating Co nanocrystals are first introduced as efficient cathode hosts for Li–S batteries. The synergetic effect of the presence of the N‐doped CNTs with Co nanocrystals and the hierarchical structure of yolk‐shell microspheres is responsible for the superior performances as the cathode hosts for Li–S batteries.
Polypropylene (PP)/carbon nanotube (CNT) nanocomposite studies have been extensively reported in the literature. Most of this previous work has been carried out by dispersing CNTs in PP matrix via ...melt processing, while only limited studies have been carried out where CNT dispersion in PP was achieved by solution processing. Here we report the melt processing of PP/multiwall carbon nanotubes (MWNT) nanocomposites after achieving functionalized MWNT (f-MWNT) dispersion in PP, and in maleic anhydride-g-PP (MA-g-PP) master batches using a butanol/xylene solvent mixture. For comparison, melt mixing of PP with pristine MWNTs (p-MWNTs) without functionalization was also carried out. The three types of nanocomposites (from PP/f-MWNT and MA-g-PP/f-MWNT master batches and from p-MWNT) were prepared using micro-compounding, followed by injection molding. In each case, the weight percent of MWNTs in the injection molded samples was 0.001, 0.005, 0.01, 0.1, 0.3, 0.5, and 1 wt%. Tensile properties, impact strength, and heat deflection temperatures of the composites have been studied. Mechanical property improvements were observed at concentrations as low as 0.001 wt% CNT loading. For example, at 0.001 wt% CNT, a statistically significant increase in modulus was observed using PP/f-MWNT master batch. At 1 wt% CNT loading, impact strength increased by 152% in samples prepared from PP/f-MWNT master batch, as compared to the control PP containing no CNTs. This is the highest percentage increase in impact strength reported to date for the homopolymer PP/CNT or for any other thermoplastic/CNT system, at 1 wt% CNT. This increase has been achieved while maintaining excellent ductility and high strain to failure of 113%. By comparison, the strain to failure at the same CNT concentration of 1 wt% was 12.5% and 19.9% for p-MWNT based and MA-g-PP/f-MWNT based nanocomposites, respectively. The changes in mechanical properties have been discussed in terms of crystallization behavior, structure, and morphology of the nanocomposites.
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•By tailoring the PP/CNT interphase, the impact strength of PP increases significantly at low (0.1 to 1 wt%) MWNT loading.•It has been shown for the first time that the impact strength of PP increases by 152% by using only 1 wt% MWNT.•The increased impact strength has been achieved without a significant loss in polymer ductility.•Improved MWNT dispersion and the formation of β-type crystals were observed in the MA-g-PP incorporated nanocomposites.
•Darcy-Forchheimer flow of carbon nanotubes is examined.•Flow is due to a rotating disk.•Flow saturating porous medium obeys Darcy-Forchheimer relation.•Results are achieved for both SWCNTs and ...MWCNTs.•Series solutions are obtained through optimal homotopy analysis method (OHAM).
The present communication deals with the Darcy-Forchheimer flow of water based carbon nanotubes (CNTs) due to a rotating disk. Results for single-wall carbon nanotubes (SWCNTs) and multi-wall carbon nanotubes (MWCNTs) have been obtained and compared. Flow in porous medium is described by utilizing Darcy-Forchheimer model. Suitable transformations lead to strong nonlinear differential system. Optimal homotopy analysis method (OHAM) is employed for solution development of governing system. The optimal values of auxiliary parameters are obtained. Plots have been displayed in order to analyze how the velocity and temperature fields are affected by various pertinent variables. Further the skin friction coefficients and local Nusselt number have been graphically examined for both SWCNTs and MWCNTs. Our findings reveal that the skin friction coefficients and local Nusselt number are enhanced for larger values of nanoparticles volume fraction.
All-carbon nanotube (CNT) hybrid films are fabricated through a facile vacuum filtration method by using hydrophilic single-walled carbon nanotube (SWCNT) films as filters and multi-walled carbon ...nanotube (MWCNT) powder dispersed in ethanol as liquor. The hydrophilic SWCNT film provides penetration channels for water, while the superhydrophobic MWCNTs have self-cleaning, self-spreading, and broadband absorption ability. The hybrid film exhibits ultra-high solar absorbance (∼99%), low thermal conductivity, and excellent light-to-heat conversion capacity. The temperature of the hybrid film increases from 24 to 60 °C in 1 s under one-sun illumination in air. The individual hybrid film exhibits a high water evaporation rate of 1.37 kg m−2 h−1 and a solar thermal efficiency of 87.4% under one-sun after 1 h illumination. The solar thermal efficiency maintains at ∼80% when many pieces of hybrid films self-assemble into a large film (∼40 cm2). The hybrid films have great potential in the desalination of seawater and sewage treatment. Ion concentrations in seawater decrease significantly to drinkable water standards by only one distillation treatment. Organic pollutants, such as rhodamine B and methylene blue, are removed effectively from sewage water by using the hybrid films in a solar steam generator.
All-carbon nanotube hybrid films with broadband optical absorption and self-cleaning ability are prepared. The films are efficient and effective in solar steam generation with a high solar evaporation efficiency of 87.4%, showing great potentials in seawater desalination and sewage purification. Display omitted
A sulfur‐linked carbonyl‐based poly(2,5‐dihydroxyl‐1,4‐benzoquinonyl sulfide) (PDHBQS) compound is synthesized and used as cathode material for lithium‐ion batteries (LIBs). Flexible binder‐free ...composite cathode with single‐wall carbon nanotubes (PDHBQS–SWCNTs) is then fabricated through vacuum filtration method with SWCNTs. Electrochemical measurements show that PDHBQS–SWCNTs cathode can deliver a discharge capacity of 182 mA h g−1 (0.9 mA h cm−2) at a current rate of 50 mA g−1 and a potential window of 1.5 V–3.5 V. The cathode delivers a capacity of 75 mA h g−1 (0.47 mA h cm−2) at 5000 mA g−1, which confirms its good rate performance at high current density. PDHBQS–SWCNTs flexible cathode retains 89% of its initial capacity at 250 mA g−1 after 500 charge–discharge cycles. Furthermore, large‐area (28 cm2) flexible batteries based on PDHBQS–SWCNTs cathode and lithium foils anode are also assembled. The flexible battery shows good electrochemical activities with continuous bending, which retains 88% of its initial discharge capacity after 2000 bending cycles. The significant capacity, high rate performance, superior cyclic performance, and good flexibility make this material a promising candidate for a future application of flexible LIBs.
A carbonyl compound (oligomeric poly(2, 5‐dihydroxyl‐1,4‐benzoquinonyl sulfide)‐based flexible cathode with superior rate performance and cyclic stability is reported. The carbonyl compound is served as active material, and single‐wall carbon nanotube, can act as a current collector and binder. Since all the materials used are inherently flexible, this flexible electrode is ready for a potential application in flexible lithium‐ion batteries.
Recent development in epidermal and bionic electronics systems has promoted the increasing demand for supercapcacitors with micrometer‐thickness and good compatibility. Here, a highly flexible ...free‐standing epidermal supercapacitor (SC‐E) with merely 1 μm thickness and high performance is developed. Single‐walled carbon nanotube/poly(3,4‐ethylenedioxythiophene) hybrid films with unique inner‐connected reticulation are adopted as electrodes for ultrathin structure and high electric conductivity. Then, based on two substrates with different surface energies, a stepwise lift‐off method is presented to peel off the ultrathin integrated supercapacitor from the substrates nondestructively. As a result of the high conductive hybrid electrodes and the thin electrolyte layer, the as‐designed supercapacitors (based on the total mass of two electrodes) achieve a good capacitance of 56 F g−1 and a superhigh power density of 332 kW kg−1, which manifest superior performance in contrast to the other devices fabricated by traditional electrodes. Meanwhile, the ultrashort response time of 11.5 ms enables the epidermal supercapacitor (SC‐E) work for high‐power units. More importantly, the free‐standing structure and outstanding flexibility (105 times bending) endow the SC‐E with excellent compatibility to be integrated and work in the next generation of smart and epidermal systems.
An epidermal supercapacitor with micrometer‐thickness and high performance is developed by the combination of single‐walled carbon nanotube/poly(3,4‐ethylenedioxythiophene) hybrid electrodes and a stepwise lift‐off technique. The free‐standing supercapacitor has superior capacity and a superhigh power density of 332 kW kg−1 as well as outstanding flexibility. It is promising for integration into future smart and epidermal systems.
A comparative study on the sodium-ion insertion and extraction of commercially-available multi-wall and single-wall carbon nanotubes is reported. Single-wall carbon nanotubes exhibit charge/discharge ...capacities of 126 mA h g−1 and multi-wall carbon nanotubes produce a lower capacity of 28 mA h g−1 after 50 cycles at 25 mA g−1. To understand these differences, a combination of X-ray diffraction and solid state nuclear magnetic resonance measurements were performed at various states of sodium insertion and extraction.23Na nuclear magnetic resonance studies, a technique previously rarely used for characterising electrodes from sodium-ion batteries, shows differences in the sodium chemical environment near multi-wall compared to single-wall carbon nanotubes with distinct sodium sites found to be active during sodium insertion and extraction for the carbon nanotubes. Both types of carbon nanotubes show a similar amount of reversible sodium available for insertion/extraction reactions, but multi-wall carbon nanotubes feature half the initial insertion capacity relative to single-wall carbon nanotubes. The electrochemical performance of the carbon nanotube electrodes are discussed in relation to the observed mechanism of sodium insertion.
•Single-walled CNTs show capacities of 126 mA h g−1 at 50 cycles in sodium-ion cells.•Single-walled CNTs ∼4 times higher capacities than multi-walled CNTs.•NMR data show both types of CNTs have similar reversible sodium cycling capacity.•The insertion capacity of single-walled CNTs are much higher than multi-walled CNTs.•Na environment more ordered in single-walled CNTs and differs to multi-walled CNTs.
Silicon‐based anodes are considered ideal candidate materials for next‐generation lithium‐ion batteries due to their high capacity. However, the low conductivity and large volume variations during ...cycling inevitably result in inferior cyclic stability. Herein, a dry method without binders is designed to fabricate Si‐based electrodes with single‐walled carbon nanotubes (SWCNTs) network and to explore the different mechanisms between SWCNT and multiwalled carbon nanotubes (MWCNTs) as a conductive network. As expected, higher initial discharge capacity (1785 mAh g−1), higher initial Coulombic efficiency (ICE, 81.52%) and outstanding cyclic stability are obtained from the SiOx@C|SWCNT anodes. Furthermore, its lithium‐ion diffusion coefficient (DLi+) is 3–4 orders of magnitude higher than that of SiOx@C|MWCNT. The underlying mechanism is clarified by in situ Raman spectroscopy and theoretical analysis. It is found that the SWCNTs can maintain good contact with SiOx@C even under tensile stresses up to 6.2 GPa, while the MWCNTs lose electrical contact due to alternating compressive stress up to 8.9 GPa and tensile stress up to 2.5 GPa during long‐term cycling. Under such very large stresses, the more flexible SWCNTs and their stronger van der Waals forces ensure that SiOx@C still has good contact with SWCNTs.
A facile dry method without binders is designed to explore why single‐walled carbon nanotubes (SWCNTs) are critical to the cyclic performance of SiOx/C. The different mechanisms between SWCNTs and multiwalled carbon nanotubes as conductive networks are clarified by in situ Raman spectroscopy. The study proposes a new approach to characterizing electrical contacts and understanding the relationships between contact and performance.
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