Showing papers on "Nanotube published in 2021"

Raman spectroscopy for carbon nanotube applications

Abstract: The use of Raman spectroscopy for carbon nanotube applications is presented here as a tutorial review. After introducing the relevant basic aspects of Raman spectroscopy of graphene-related materials, we will discuss how to use the Raman spectral features for practical purposes of controlling and characterizing nanotube properties relevant for applied materials and devices. Advanced techniques with potential to enhance the relevance of Raman spectroscopy application in the carbon nanotube field are also presented.

Two steps synthesis of CeTiOx oxides nanotube catalyst: Enhanced activity, resistance of SO2 and H2O for low temperature NH3-SCR of NOx

Abstract: Cerium and titanium oxides are considered as promising alternative catalysts for selective catalytic reduction with NH3 (NH3-SCR) to remove NOx. However, the poor SO2 or H2O tolerance and stability limit their practical applications. Herein, CeTiOx with nanotube structure (CeTiOx-T) was prepared by hydrothermal method and used for NH3-SCR reaction. CeTiOx-T shows the excellent catalytic activity, SO2 and H2O tolerance and stability, in which more than 98 % NO conversion can be achieved in the range of 180−390 °C with 100 % N2 selectivity. The characterizations verify that CeTiOx-T exhibits amorphous structure due to the strong interaction between Ce and Ti to form short-range ordered Ce-O-Ti species. As results, CeTiOx-T displays the larger BET surface area, more surface Bronsted acid amounts and chemisorbed oxygen, leading to its higher NH3-SCR performance. In situ DRIFTS results suggest the SCR reaction mainly follow L-H and E-R mechanisms at low and high temperature for over CeTiOx-T, respectively.

Fabrication, Functionalization, and Application of Carbon Nanotube-Reinforced Polymer Composite: An Overview.

Abstract: A novel class of carbon nanotube (CNT)-based nanomaterials has been surging since 1991 due to their noticeable mechanical and electrical properties, as well as their good electron transport properties. This is evidence that the development of CNT-reinforced polymer composites could contribute in expanding many areas of use, from energy-related devices to structural components. As a promising material with a wide range of applications, their poor solubility in aqueous and organic solvents has hindered the utilizations of CNTs. The current state of research in CNTs—both single-wall carbon nanotubes (SWCNT) and multiwalled carbon nanotube (MWCNT)-reinforced polymer composites—was reviewed in the context of the presently employed covalent and non-covalent functionalization. As such, this overview intends to provide a critical assessment of a surging class of composite materials and unveil the successful development associated with CNT-incorporated polymer composites. The mechanisms related to the mechanical, thermal, and electrical performance of CNT-reinforced polymer composites is also discussed. It is vital to understand how the addition of CNTs in a polymer composite alters the microstructure at the micro- and nano-scale, as well as how these modifications influence overall structural behavior, not only in its as fabricated form but also its functionalization techniques. The technological superiority gained with CNT addition to polymer composites may be advantageous, but scientific values are here to be critically explored for reliable, sustainable, and structural reliability in different industrial needs.

Carbon nitride nanotubes with in situ grafted hydroxyl groups for highly efficient spontaneous H2O2 production

Abstract: An active and inexpensive photocatalyst for H2O2 production is desirable for industrial applications. However, obtaining high photocatalytic activity from metal-free catalysts without the use of sacrificial electron donors is difficult. Herein, g-C3N4 (CN) nanotubes functionalized with surface > OH groups that are grafted in situ were successfully synthesized via a novel alkalinization process. The nanotube structures provide a large surface area and improved mass transfer properties. In situ grafted > OH groups can capture photogenerated holes to promote separation of photogenerated charge, enabling the ready availability of electrons and hydrogen ions for H2O2 production. Further, the surface > OH groups help to suppress H2O2 self-decomposition. Consequently, a high rate of 240.36 μmol h−1 g−1 of H2O2 production can be achieved without sacrificial agents, which is the highest H2O2 production in a spontaneous system for metal-free photocatalysts. This work provides a new strategy for an efficient and spontaneous H2O2 production method using a metal-free CN photocatalyst.

Engineering defect-rich Fe-doped NiO coupled Ni cluster nanotube arrays with excellent oxygen evolution activity

Abstract: Herein we present a novel multi-level structure of Fe-doped NiO coupled Ni cluster hollow nanotube arrays (Fe-NiO-Ni CHNAs) grown on carbon fiber cloth as an efficient catalyst for oxygen evolution reaction. In this multi-level structure, rocksalt-type Fe-doped NiO phase hybrids with Ni clusters coupled into the nanospheres anchored to the outside of nanotube, forming a unique 3D corn-like structure. This novel multi-level structure represents a large specific area for catalytic reaction. X-ray absorption fine structure indicates that the defect-rich Fe-doped NiO phase has abundant coordinative unsaturated sites as active sites, and Fe doping downshifts the d-band of metal sites, which is the main contribution to the improved oxygen evolution reaction catalytic activity. The OER of Fe-NiO-Ni CHNAs obeys the adsorbate evolution mechanism with the nonconcerted proton-electron transfer pathway as a rate-determining step. Thus Fe-doped NiO CHNAs exhibits excellent OER performance and outstanding durability that surpasses most of transition metal oxides.

Tailoring the d-band center of N-doped carbon nanotube arrays with Co4N nanoparticles and single-atom Co for a superior hydrogen evolution reaction

Abstract: A 3D self-supported integrated electrode, consisting of heteroatomic nitrogen-doped carbon nanotube arrays on carbon cloth with confined ultrafine Co4N nanoparticles and a distribution of anchored single-atom Co, is fabricated via a cobalt-catalyzed growth strategy using dicyandiamide as the nitrogen and carbon source and a layered cobalt hydroxide-nitrate salt as the precursor. The abundance of exposed active sites, namely, the Co4N nanoparticles, single-atom Co, and heteroatomic N-doped carbon nanotubes, and multiple synergistic effects among these components provide suitable tailoring of the d-band center for facilitating vectorial electron transfer and efficient electrocatalysis. Benefiting from the merits of its structural features and electronic configuration, the prepared electrode exhibits robust performance toward the hydrogen evolution reaction with overpotentials of only 78 and 86 mV at 10 mA cm−2 in acidic and basic electrolytes, respectively. Density functional theory calculations and X-ray photoelectron spectroscopy valence band measurements reveal that the effective tailoring of the d-band center by Co4N nanoparticles plays a crucial role in optimizing the hydrogen adsorption free energy to a more thermoneutral value for efficient electrocatalysis. A carbon-based, environmentally friendly catalyst for enhancing the extraction of hydrogen from water has been synthesized by researchers in China. Separating water into its constituent atoms is a scalable method for producing hydrogen and therefore a source of clean energy. Platinum catalysts can enhance electrochemical splitting, but platinum is rare and expensive. Bo Cao from Inner Mongolia University, Hohhot, and co-workers have developed an alternative carbon nanotube-based catalyst that can be fabricated using a “green” process. Carbon nanotubes have been used previously, often in a powder form, from which it is difficult to make the electrodes required in practical applications. The researchers created three-dimensional electrodes on carbon cloth using arrays of nitrogen-doped carbon nanotubes containing cobalt nitride nanoparticles, and confirmed the excellent electrocatalytic properties of the material. A novel 3D self-supported integrated electrode of Co4N@CoSA/N-CNT/CC is designed for admirable HER electrocatalysis. Experiment and theory studies reveal that the suitable d-band center and electron-charge transfer optimized by Co4N nanoparticles and single-atom Co in the electrocatalyst contribute to an excellent performance. This electrode requires overpotentials of only 78 and 86 mV at 10 mA cm−2 in acidic and basic electrolytes, respectively. Notably, Co4N@CoSA/N-CNT/CC also exhibits superior long-term stability in acidic and alkaline medium, the decrease in current density after continuous electrocatalysis for 50 h are only 5% and 11%, respectively.

Polypyrrole Nanotube-Interconnected NiCo-LDH Nanocages Derived by ZIF-67 for Supercapacitors

Abstract: Layered double hydroxides (LDHs), composed of typical lamellar architectures, have become splendid electroactive materials for supercapacitors by means of large specific surface area and high theor...

Experimental Investigation on Mechanical Properties of Carbon Nanotube-Reinforced Epoxy Composites for Automobile Application

Abstract: Carbon nanotubes are established as a superior form of carbon. These have superior characteristics in terms of mechanical and chemical properties when compared to the other fibres available. High-strength fibres can be employed in a composite in a short form and mass-produced to fulfil high demands in composite applications. These composites can meet the strength requirements of nonstructural and structural components in a wide range of industries. Because of their light weight and excellent strength-to-weight ratio, these composites can be used in a wide range of applications. With Young’s modulus as high as 1 TPa and tensile strength up to 63 GPa, they are among the stiffest and strongest fibres. There is currently a lot of interest in using carbon nanotubes in a matrix to take advantage of these features. There have been a variety of polymer matrices used, and nanotube/ceramic and nanotube/metal composites are gaining popularity. The study of these materials is an ongoing process, as researchers and design engineers have yet to realize their full potential. Carbon nanotubes (CNTs) are used in this study to create the composite with the resin. The percentage of CNT used as a filler material in the composite is varied from 1 to 4 percent, with the best percentage chosen for optimal mechanical properties.

Metalloporphyrin-based D-A type conjugated organic polymer nanotube for efficient photocatalytic degradation

Abstract: A series of porphyrin-based D-A type conjugated organic polymer (COP) nanotubes MTAPP-BT (M= H2, Zn, Cu, Fe) were synthesized through acid-catalyzed Schiff base reaction between metalloporphyrins (MTAPP) and benzothiadiazole (BT) units. Among them, CuTAPP-BT shows superior photocatalytic activity and recyclability for bisphenol A (BPA) degradation. The transfer and separation of photo-induced carriers can be significantly improved through the metal-to-ligand charge transfer (MLCT) and electron push-pull effect between porphyrin units (electron donor, D) and benzothiadiazole moieties (acceptor, A). The nanotube structure exposed abundant active sites and improved the adsorption capacity for BPA through the π-π interaction and surface hydrogen bond. The possible mechanism of photocatalytic degradation for BPA over CuTAPP-BT was proposed based on molecular orbital (MO) theory. This investigation will provide a new insight about design and synthesis of novel D-A type COPs with enhanced photocatalytic activities.

Clay nanotube-metal core/shell catalysts for hydroprocesses.

Abstract: Catalytic hydroprocesses play a significant role in oil refining and petrochemistry. The tailored design of new metal nanosystems and optimization of their support, composition, and structure is a prospective strategy for enhancing the efficiency of catalysts. Mesoporous support impacts the active component by binding it to the surface, which leads to the formation of tiny highly dispersed catalytic particles stabilized from aggregation and with minimized leaching. The structural and acidic properties of the support are crucial and determine the size and dispersion of the active metal phase. Currently, research efforts are shifted toward the design of nanoscale porous materials, where homogeneous catalysts are displaced by heterogeneous. Ceramic materials, such as 50 nm diameter natural halloysite nanotubes, are of special interest for this. Much attention to halloysite clay is due to its tubular structure with a hollow 10-15 nm diameter internal cavity, textural characteristics, and different chemical compositions of the outer/inner surfaces, allowing selective nanotube modification. Loading halloysite with metal particles or placing them outside the tubes provides stable and efficient mesocatalysts. The low cost of this abundant nanoclay makes it a good choice for the scaled-up architectural design of core-shell catalysts, containing active metal sites (Au, Ag, Pt, Ru, Co, Mo, Fe2O3, CdS, CdZnS, Cu-Ni) located inside or outside the tubular template. These alumosilicate nanotubes are environment-friendly and are available in thousands of tons. Herein, we summarized the advances of halloysite-based composite materials for hydroprocesses, focusing on the selective binding of metal particles. We analyze the tubes' morphology adjustments and size selection, the physicochemical properties of pristine and modified halloysite (e.g., acid-etched or silanized), the methods of metal clusters formation, and their localization. We indicate prospective routes for the architectural design of stable and efficient nanocatalysts based on this safe and natural clay material.

Printable and recyclable carbon electronics using crystalline nanocellulose dielectrics

Abstract: Electronic waste can lead to the accumulation of environmentally and biologically toxic materials and is a growing global concern. Developments in transient electronics—in which devices are designed to disintegrate after use—have focused on increasing the biocompatibility, whereas efforts to develop methods to recapture and reuse materials have focused on conducting materials, while neglecting other electronic materials. Here, we report all-carbon thin-film transistors made using crystalline nanocellulose as a dielectric, carbon nanotubes as a semiconductor, graphene as a conductor and paper as a substrate. A crystalline nanocellulose ink is developed that is compatible with nanotube and graphene inks and can be written onto a paper substrate using room-temperature aerosol jet printing. The addition of mobile sodium ions to the dielectric improves the thin-film transistor on-current (87 μA mm−1) and subthreshold swing (132 mV dec−1), and leads to a faster voltage sweep rate (by around 20 times) than without ions. The devices also exhibit stable performance over six months in ambient conditions and can be controllably decomposed, with the graphene and carbon nanotube inks recaptured for recycling (>95% recapture efficiency) and reprinting of new transistors. We demonstrate the utility of the thin-film transistors by creating a fully printed, paper-based biosensor for lactate sensing. All-carbon thin-film transistors—made using crystalline nanocellulose as a dielectric, carbon nanotubes as a semiconductor and graphene as a conductor—can be printed onto paper substrates and the constituent materials subsequently recycled.

Radiofrequency transistors based on aligned carbon nanotube arrays

Abstract: The development of next-generation wireless communication technology requires integrated radiofrequency devices capable of operating at frequencies greater than 90 GHz. Carbon nanotube field-effect transistors are promising for such applications, but key performance metrics, including operating frequency, at present fall below theoretical predictions. Here we report radiofrequency transistors based on high-purity carbon nanotube arrays that are fabricated using a double-dispersion sorting and binary liquid interface aligning process. The nanotube arrays exhibit a density of approximately 120 nanotubes per micrometre, a maximum carrier mobility of 1,580 cm2 V−1 s−1 and a saturation velocity of up to 3.0 × 107 cm s−1. The resulting field-effect transistors offer high d.c. performance (on-state current of 1.92 mA µm−1 and peak transconductance of 1.40 mS μm−1 at a bias of −0.9 V) for operation at millimetre-wave and terahertz frequencies. Transistors with a 50 nm gate length show current-gain and power-gain cutoff frequencies of up to 540 and 306 GHz, respectively, and radiofrequency amplifiers can exhibit a high power gain (23.2 dB) and inherent linearity (31.2 dBm output power of the third-order intercept point) in the K-band (18 GHz). Transistors based on arrays of aligned carbon nanotubes can exhibit cutoff frequencies of up to 540 GHz, and could be further scaled for operation at millimetre-wave and terahertz frequencies.

Superior rate-capability and long-lifespan carbon nanotube-in-nanotube@Sb2S3 anode for lithium-ion storage

Abstract: It is vital to improve the rate capability and cycling performance of Sb2S3 to promote its application in lithium-ion batteries. Herein, Sb2S3 is successfully anchored inside a carbon nanotube-in-nanotube via a multi-step method based on a metal–organic framework and carbon nanotubes. The composite has a large specific surface area (48.1 m2 g−1), relatively high content of Sb2S3 (57%), and an external highly conductive nitrogen-doped amorphous carbon nanotube. Benefitting from these advanced structure advantages, such as well-confined Sb2S3, completely closed internal void space, highly conductive carbon matrix, and formation of C–S covalent bonds, the composite exhibits superior lithium storage performance. The rate capability is its highlight. Even at 15 A g−1, the discharge capacity still reaches 361 mA h g−1. After the rate test, a cycling test at 5 A g−1 up to 400 cycles demonstrates its excellent structural stability. The cycling performance is very impressive (710.5 mA h g−1 at 1 A g−1 after 1500 cycles, 316 mA h g−1 at 5 A g−1 after 1700 cycles, 201.5 mA h g−1 at 10 A g−1 after 1000 cycles). The reversible capacity is outstanding (1117.2 mA h g−1 at 0.1 A g−1). Electrochemical kinetic analyses and ex situ observation of the cycled composite are studied in detail to comprehensively elucidate its electrochemical mechanism. It can be concluded that carbon nanotube-in-nanotube@Sb2S3 is a promising anode material for high-performance lithium-ion batteries.

Evidence of oxygen bubbles forming nanotube embryos in porous anodic oxides

Abstract: Anodic TiO2 nanotubes have been studied widely for two decades because of their regular tubular structures and extensive applications. However, the formation mechanism of anodic TiO2 nanotubes remains unclear, because it is difficult to find convincing evidence for popular field-assisted dissolution or field-assisted injection theories and the oxygen bubble model. Here, in a bid to find direct evidence that oxygen bubbles form nanotube embryos, a new method is applied to handle this challenge. Before nanotube formation, a dense cover layer was formed to make nanotubes grow more slowly. Many completely enclosed nanotube embryos formed by oxygen bubbles were found beneath the dense cover layer for the first time. The formation of these enclosed and hollow gourd-shaped embryos is convincing enough to prove that the nanotubes are formed by the oxygen bubble mold, similar to inflating a football, rather than by field-assisted dissolution. Based on the ‘oxygen bubble model’ and ionic current and electronic current theories, the formation and growth process of nanotube embryos is explained clearly for the first time. These interesting findings indicate that the ‘oxygen bubble model’ and ionic current and electronic current theories also apply to anodization of other metals.

Study on the adsorption properties of methyl orange by natural one-dimensional nano-mineral materials with different structures.

Abstract: Methyl orange (MO) is a common anionic azo dye that is harmful to the environment and biology, so it must be treated innocuously before it can be discharged. Adsorption is an effective method to remove anionic dyes. Nanotube mineral is a natural one-dimensional adsorption material, and its unique morphology and structure endow it with good adsorption capacity. Although there are many related studies, there is a lack of in-depth discussions on the influence of nanotube’s composition and structure on the adsorption of dyes and other pollutants. In this paper, two kinds of natural one-dimensional silicate minerals [halloysite nanotubes (HNTs) and chrysotile nanotubes (ChNTs)] with similar morphology but slightly different compositions and crystal structures were used as adsorbents, and MO solution was used as simulate pollutants. It is the first time to discuss in depth the influence of the composition and structure of nanotube minerals on their charge properties and the adsorption performance of methyl orange dyes. It is found that HNTs and ChNTs have different adsorption capacity due to the difference of electronegativity between Al3+ and Mg2+ in the crystal, so they possess negative and positive charges respectively in near-neutral solution, which leads to the adsorption capacity of MO by ChNTs with positive charges which is greater than that of HNTs.

Oxygen-Defect Enhanced Anion Adsorption Energy Toward Super-Rate and Durable Cathode for Ni-Zn Batteries.

Abstract: The alkaline zinc-based batteries with high energy density are becoming a research hotspot. However, the poor cycle stability and low-rate performance limit their wide application. Herein, ultra-thin CoNiO2 nanosheet with rich oxygen defects anchored on the vertically arranged Ni nanotube arrays (Od-CNO@Ni NTs) is used as a positive material for rechargeable alkaline Ni–Zn batteries. As the highly uniform Ni nanotube arrays provide a fast electron/ion transport path and abundant active sites, the Od-CNO@Ni NTs electrode delivers excellent capacity (432.7 mAh g−1) and rate capability (218.3 mAh g−1 at 60 A g−1). Moreover, our Od-CNO@Ni NTs//Zn battery is capable of an ultra-long lifespan (93.0% of initial capacity after 5000 cycles), extremely high energy density of 547.5 Wh kg−1 and power density of 92.9 kW kg−1 (based on the mass of cathode active substance). Meanwhile, the theoretical calculations reveal that the oxygen defects can enhance the interaction between electrode surface and electrolyte ions, contributing to higher capacity. This work opens a reasonable idea for the development of ultra-durable, ultra-fast, and high-energy Ni–Zn battery.