Fiber-like Carbon Research Articles

Top-down strategy for bamboo lignocellulose-derived carbon heterostructure with enhanced electromagnetic wave dissipation

Biomass-derived residue carbonization has been an important issue for “carbon fixation” and “zero emission”, and the carbonized products have multiple application potentials. However, there have been no specific research to study the differences in macro- and micro-morphology, electrical properties and many other aspects of the products obtained from carbonization of pure cellulose, pure lignin or their complex, lignocellulose. In this work, lignocellulose with cellulose to lignin mass ratio of 10:1 is obtained using p -toluenesulfonic acid hydrolysis followed by homogenization process at a controlled condition. Then, carbon heterostructure with fibers and sheets (CH-10) are obtained by pyrolysis at 1500 °C. Detailed results imply that the fiber-like carbon structure possesses high crystallinity and low defect density, coming from carbonization of the cellulose content in lignocellulose (LC) nanofibers. Correspondingly, the graphite-like carbon sheet with high defect density and low crystallinity comes from carbonization of the lignin content in LCs. Further investigation indicates CH-10 possesses enhanced polarization and moderate impedance matching which makes it an ideal candidate for electromagnetic wave (EMW) absorption. CH-10 exhibits an excellent EMW absorption performance with a minimum RL value of −50.05 dB and a broadest absorption bandwidth of 4.16 GHz at a coating thickness as thin as 1.3 mm.

Hydrogen bond interactions within OH-CQDs/fiber-like carbon nitride for enhanced photodegradation and hydrogen evolution

Graphitic carbon nitride (g-C3N4) possess great potential applications in photocatalytic wastewater purification and hydrogen production. However, its activity is moderate because of the sluggish electron transfer and insufficient light absorption. Here, a series of hydroxyl carbon quantum dots modified with fiber-like carbon nitride composites (OH-CQDs/CNF) were synthesized by a solvothermal approach to enhance the photocatalytic activity. Compared to g-C3N4, the prepared OH-CQDs/CNF exhibited significantly improved visible light absorption (UV-VIS), low recombination electron-hole pairs (PL), and dramatically enhanced conductivity (EIS). Therefore, the optimized OH-CQDs/CNF-4 composite (derived from 4 mL OH-CQDs) displayed excellent photodegradation activity, and its rate constant for tetracycline degradation was 11.3 times higher than that in the presence of g-C3N4, even higher than some noble metal or metal oxides modified g-C3N4. In addition, OH-CQDs/CNF-4 rendered around 4 times H2 evolution rate than CNF, mainly because the OH-CQDs were highly dispersed on the CNF surface and formed an intact interface through hydrogen bond interactions. Quenching experiments and ESR results indicated that ·O2− and h+ were the main free radicals generated during TC degradation. This study provides guidance for the design of hydrogen bonding-based metal-free photocatalysts for wastewater purification and hydrogen evolution.

Construction of Schottky-type Ag-loaded fiber-like carbon nitride photocatalysts for tetracycline elimination and hydrogen evolution

In this study, a series of Schottky-type Ag-loaded fiber-like carbon nitride photocatalysts (Ag/CNF) were prepared via a combination of the solvothermal method and sodium borohydride reduction. Transmission electron microscopy images revealed that Ag particles with diameters of 10–20 nm were evenly deposited on the CNF. The Ag/CNF Schottky-type composites exhibited strong photocatalytic activity for tetracycline (TC) degradation upon irradiation with visible light. The rate constant for TC degradation was enhanced approximately 23.56 and 2.97 times in the presence of the 1.2%-Ag/CNF composite as compared with bulk g-C3N4 and CNF, respectively. In addition, the Ag-CNF Schottky-type composites promoted hydrogen evolution. Free radical trap experiments and electron spin resonance results revealed that holes (h+) and superoxide radicals (·O2−) were the major active species during the photocatalytic degradation. The improved photocatalytic performance was attributable to the surface plasmon resonance of Ag and the effective separation of the photogenerated charges due to the construction of Schottky junctions between Ag and the semiconductors. This work might provide a basis for the construction of carbon nitride-based Schottky-type heterojunctions for hydrogen evolution and elimination of TC from the environment.

Structural Effect of Conductive Carbons on the Adhesion and Electrochemical Behavior of LiNi0.4Mn0.4Co0.2O2 Cathode for Lithium Ion Batteries

The adhesion strength as well as the electrochemical properties of LiNi0.4Mn0.4Co0.2O2 electrodes containing various conductive carbons (CC) such as fiber-like carbon, vapor-grown carbon fiber, carbon nanotubes, particle-like carbon, Super P, and Ketjen black is compared. The morphological properties is investigated using scanning electron microscope to reveal the interaction between the different CC and the active material. The surface and interfacial cutting analysis system is also used to measure the adhesion strength between the aluminum current collector and the composite film, and the adhesion strength between the active material and the CC of the electrodes. The results obtained from the measured adhesion strength points to the fact that the structure and the particle size of CC additives have tremendous influence on the binding property of the composite electrodes, and this in turn affects the electrochemical property of the configured electrodes. Keywords: Conductive carbons, Composite electrodes, Adhesion property, Lithium ion batteries, Surface and interfacial cutting analysis system

Structural Effect of Conductive Carbons on the Adhesion and Electrochemical Behavior of NMC-442 Cathode for Lithium Ion Battery

The adhesion strength as well as the electrochemical properties of LiNi0.4Mn0.4Co0.2O2 electrodes containing fiber-like carbon; vapor grown carbon fiber (VGCF), carbon nanotube (CNT) and particle-like carbon; super P (SP), ketjen black (KB) were compared. The morphological properties revealing the interaction between the different conductive carbons (CCs) and the active material was investigated using scanning electron microscope. The adhesion strength between the aluminum current collector and the composite film (AC/Al), and the adhesion strength between the active material and the CCs (Amid) of the electrodes were measured using surface and interfacial cutting analysis system (SAICAS). The results obtained from the measured adhesion strength points to the fact that, the structure and the particle size of conductive additives have tremendous influence on the binding property of the composite electrodes and this in turn affects the electrochemical property of the configured electrodes.

Tamarind seed skin-derived fiber-like carbon nanostructures as novel anode material for lithium-ion battery

Demand of low-cost carbonaceous anode materials for lithium-ion batteries has led to the development of anode materials from different bio-sources. In this regard, tamarind seed (skin) was used as a precursor to prepare disordered carbon as an anode material for lithium-ion batteries. The carbon was prepared through simple hydrothermal method and was characterized by X-ray diffraction (XRD), Raman spectroscopy, Brunauer–Emmett–Teller (BET) measurements, field emission scanning electron microscopy (FE-SEM), and transmission electron microscopy (TEM) techniques. It exhibited amorphous carbon particles arranged in a fiber-like morphology with high surface area of 508 m2 g−1. The binder content was optimized for the carbon to achieve high and stable capacity. Electrochemical performance of the as-prepared carbon with optimized binder content showed a stable reversible specific capacity of 224 mAhg−1 after 300 cycles at 1 C-rate. The stable cycling performance of carbon at high current rate is explained by electrochemical impedance spectroscopy (EIS) and FE-SEM data of cycled electrodes. The low cost and stable specific capacity make the carbon as potential anode material for lithium-ion battery.

Dielectric, mechanical and electro-stimulus response properties studies of polyurethane dielectric elastomer modified by carbon nanotube-graphene nanosheet hybrid fillers

The typical nano-carbon materials, 1D fiber-like carbon nanotubes (CNTs) and 2D platelet-like graphene nanosheets (GRNs), that have attracted tremendous attention in the field of polymer nanocomposites due to their unprecedented properties, are used as conducting filler to induce a considerable improvement in the mechanical, thermal and electrical properties of the resulting graphene/polymer nanocomposites at very low loading contents. This study deals with the preparation and electro-stimulus response properties of polyurethane (PU) dielectric elastomer films with such 1D and 2D nanocarbon fillers embedded in the polymer matrix. The various forms of carbon used in composite preparation include CNT, GRN and CNT-GRN hybrid fillers. Results indicate that the dielectric, mechanical and electromechanical properties depend on the carbon filler type and the carbon filler weight fraction. Here, it has been also established that embedding CNT-GRN hybrid fillers into pristine polyurethane endows somewhat better dispersion of CNTs and GRNs as well as better interfacial adhesion between the carbon fillers and matrix, which results in an improvement in electric-induced strain. Therefore, the nanocomposites seem to be very attractive for microelectromechanical systems applications.

Self-Assembled Carbon Nanostructures in Nickel Containing Hydrogenated Amorphous Carbon Matrix by One-Step Electrodeposition

Carbon nanostructures incorporated hydrogenated amorphous carbon matrix composite was facilely assembled by the electrolysis of a methanol solution of nickel pentanedionate at ambient atmosphere pressure. Results confirmed that, nickel grains were embedded in amorphous carbon matrix forming nanocrystallite/amorphous composite structure, meanwhile fiber-like carbon were interconnected and dispersed in nickel containing hydrogenated amorphous carbon matrix. The growth mechanism of the as-deposited nanocomposite film mainly involved fiber-like carbon growing onto an enriched nickel template at the un-equilibrium micro-zone around the cathodic substrate during the electrochemical process.

Study on the carbon deposition in steam reforming of ethanol over Co/CeO2 catalyst

Abstract In this work, coke formation over Co/CeO2 catalysts for the steam reforming of ethanol was studied. Variations of ethanol conversion and product distribution with reaction temperature and time were investigated and the used catalysts were characterized with thermal analysis method and transmission electron microscopy. The results indicate that the reaction temperature exerts influences on coke formation and its property significantly. As the reaction temperature is 450 °C or lower, catalyst particles are heavily enclosed by cokes, leading to severe deactivation. As the reaction temperature is 500 °C or 550 °C, the encapsulation of catalyst particles is rarely observed due to the formation of another kind of carbon, namely, tube- or fiber-like carbon, which results in mild deactivation. When the reaction temperature is over 600 °C, carbon deposition is not a major problem for the steam reforming of ethanol over Co/CeO2 catalysts, for carbon deposition or coke formation under these temperatures is not notable.

SHS of composite ceramics from mechanochemically treated and thermally carbonized SiO2 powders

New ceramic composites have been synthesized upon combined use of mechanochemical treatment (MCT) of SiO2, its thermal carbonization (followed by baking), and SHS in a mixture of thus activated (carbonized) SiO2 with Al powder. MCT and thermal carbonization were found to result in formation of fiber-like carbon structures on the surface of silica particles. The rigid carbon frameworks formed on the surface of silicon dioxide were found to improve the physicochemical properties of resultant carbon-containing refractory materials.

Study of Field Emission Behavior of Carbon Nanotubes with Different Sources

AbstractThe field emission properties of carbon nanotubes (CNTs) from various sources are investigated for the application of field emission displays. Comparisons are made between graphite with Ni metal as catalyst and polycyclic aromatic hydrocarbon as precursor by the arc discharge method. Cathode deposits are examined using scanning electron microscopy (SEM) and high-resolution transmission electron microscopy (HRTEM) to determine microstructure. Carbon structure is studied using Raman spectroscopy. Electron field emission characteristics are measured with the diode method at 10-6 torr pressure. In this study, SEM micrographs of cathode deposits show dense random fiber-like carbon nanotubes. The HRTEM images clearly exhibit characteristic features of multiwalled carbon nanotubes. Microstructural investigation provides evidence that both the metal catalyst and the precursor can be used to synthesize carbon nanotubes. The Raman spectrum shows a stronger peak at about 1580 cm-1 indicating formation of a well-graphitized carbon nanotube. The degree of carbon nanotube graphitization is high and is in good agreement with the HRTEM result. From field emission measurements, the lowest onset field is about 1.0 V/μm and can be attributed to highly sharp tips and the high density of carbon nanotubes. Based on microstructure characterization and field emission measurements, the influence on field emission properties including turn on voltage and threshold voltage of carbon nanotubes synthesized from different sources is discussed.