Search

A vibration analysis of single- and double-walled carbon nanotubes as well as nanotubes embedded in an elastic matrix is presented using wave propagation approach. Approximate Flügge shell equations are proposed as the governing equations of vibration for the carbon nanotubes studied here. The double-walled nanotubes are assumed to be coupled together through the van der Waals force between the inner and outer nanotubes. For embedded carbon nanotubes, an elastic medium surrounding the nanotubes is described by a Winkler model. Effects of nanotube parameters and vibrational modes on the natural frequency are investigated and analyzed based on the proposed elastic continuum model. [ABSTRACT FROM AUTHOR]

Atomically resolved scanning tunneling microscopy (STM) results are shown for substitutionally doped boron atoms in the hexagonal carbon network of highly oriented pyrolytic graphite (HOPG). STM images of boron-doped HOPG reveal not only a clear change in the electronic structure of the surface graphene network, but also one that directly affects the electronic structure of the graphene layer from the HOPG surface which is very exceptional for STM measurements. The boron atom site in the graphene network appears as the brightest area in the image including the six adjacent carbon atoms which have relatively higher intensity than normal carbon atoms in the STM image. The average boron-to-boron distance in the basal plane is consistent with Raman spectroscopy results. These structural results suggest that the graphite planes can be tailor made both atomically and electronically, and that boron doping can contribute to controlling the properties of the hexagonal carbon network in order to modify its properties relative to those of ideal graphite. © 2001 American Institute of Physics. [ABSTRACT FROM AUTHOR]

Presents a study which bserved the preparation and electrical properties of bromine intercalated vapor-grown carbon fibers. Details on the experiment; Results of the study; Conclusions.

Graphitic spheres were synthesized by the aerosol-assisted chemical vapor deposition method (AACVD), pyrolyzing a solution of toluene, ferrocene, and thiophene at 1020 °C for 30 min. The graphitic spheres were collected from different zones of the AACVD system. The scanning electron and transmission electron micrographs (SEM and TEM) showed that the synthesized carbon material comprises a complex network containing the structures of coalesced graphitic spheres structures with diameters ranging from 0.1 to 0.8 µm. X-ray diffraction patterns of these structures revealed a slight shoulder at ~ 21 2θ, suggesting the presence of expanded graphitic materials. We have also identified a narrow peak of around 29.3 2θ for samples collected outside the condenser. From a deconvolution analysis, we identified a Raman band around 1179–1194 cm−1, attributed to sp2 and sp3 bond stretching, indicating surface functionalization. The morphology, surface chemistry, composition, and thermal stability of graphitic spheres are discussed. Additionally, we present a density functional theory study to support the structural stability of many functional groups and chemical doping based on the elements sulfur and oxygen on curved carbon structures. The HOMO and LUMO energies and the electrostatic potential from charge density of several chemical species such as C–O–C, C–COOH, O-furan, C–SH, C–SO, C–SO2, and S-doping in a C240 fullerene are discussed. [ABSTRACT FROM AUTHOR]

Abstract: We have evaluated the biological responses to four different types of carbon nanotubes (CNTs), by measuring CD4+ and CD8+ T-cells in peripheral blood, and by the histopathological study on tissues surrounding subcutaneously implanted CNTs for up to 3 months. All mice survived, and no large changes in their weights were observed within our experimental period. After 1 week, only single-walled carbon nanotubes (SWNTs) activated major histocompatibility complex (MHC) class I pathway of antigen–antibody response system (higher CD4+/CD8+ value), resulting in the appearance of an edematous aspect. After 2 weeks, significantly high values in CD4+ and CD4+/CD8+ without change in CD8+ signified an activated MHC class II for all samples. It is worth noting that the toxicological response of CNTs was absolutely lower than that of asbestos. As a result, we envisaged that our result (relatively low toxicity of CNTs) will spur the mass-production, as well widespread application of CNTs in the near future. [Copyright &y& Elsevier]

Abstract: We present a percolation study of a two-dimensional crossbar networks and investigate the percolation behavior in fiber-reinforced composites. A modified model of sticks with a finite width is proposed for predicting percolation threshold of volume fraction of the fiber-reinforced composites. Based on the presented model and Monte Carlo simulations, the influences of fiber aspect ratio and orientation on the percolation behavior were investigated. It was found that the percolation threshold had a linear dependence with aspect ratio more than 40 in double-logarithmic plot. The percolation threshold had larger dependence on the orientation angle less than . In terms of a model considering the tunneling effect, furthermore, the composite system filled with carbon nanotubes predicted to obtain lower percolation threshold. For lower fiber aspect ratios, fiber ends strongly affected the connection of crossbar networks. [Copyright &y& Elsevier]

Abstract: Carbon nanofiber–copper composite films with different types of nanofibers were fabricated by an electrodeposition process. Four types of carbon nanofibers, vapor-grown carbon nanofibers without heat treatment, vapor-grown carbon nanofibers with heat treatment, vapor-grown carbon nanofibers with smaller diameters, and vapor-grown carbon nanofibers with a cup-stacked nanostructure were used. The carbon nanofibers were homogeneously dispersed in sulfate copper plating baths in the presence of polyacrylic acid. Electrodeposition was carried out under galvanostatic conditions using these copper plating baths. The deposition resulted in electrodeposited copper films containing the carbon nanofibers distributed homogeneously. The surface morphology of the carbon nanofiber–copper composite films was observed to be affected by the type of carbon nanofiber used. [Copyright &y& Elsevier]

Based on a continuum shell model, a structural mechanics approach is presented to simulate stress–strain behavior of carbon nanotubes (CNTs). The nanoscale continuum theory is established to directly incorporate the Morse potential function into the constitutive model of CNTs. According to the present model, the mechanical properties of both zigzag and armchair tubes are investigated. The result shows that the atomic structures of CNTs have a significant influence on the stress–strain behavior. The armchair zigzag tube exhibits larger stress–strain response than the zigzag tube under tensile loading, but its relationship turns over between the tension and compression deformations. The theoretical approach supplies a set of very simple formulas and able be serve as a good approximation on the mechanical properties for CNTs. [Copyright &y& Elsevier]

Multi-walled carbon nanotubes (MWNTs), having a diameter around 100–200 nm, were used as host material for electrodeposition of Ni using a Ni plating bath containing homogeneously dispersed MWNTs. Ni-deposited or coated MWNTs with a skewered dumpling shape accumulated on the Cu cathode electrode. A model representing the growth process of these electrodeposits, which possess such a skewered dumpling shape, is presented. These electrodeposits were separated easily from the cathode electrode by ultrasonic irradiation in an acetone bath to yield a Ni-deposited or coated MWNTs powder. The amount of Ni deposited on the MWNTs can be controlled by selecting the appropriate electroplating conditions. [Copyright &y& Elsevier]

We investigated the stable structures, electronic and Li-adsorption properties of C 54 H 18 and its substituted sheets X 2 C 52 H 18 (X=B, N, Si, P, S, Al and F) by a semiempirical molecular orbital method. The F 2 C 52 H 18 sheet was found to have a unique structure and adsorb more Li atoms than the other sheets. This result suggests that the F-substitution into disordered carbons may increase the Li-storage in disordered carbons. [ABSTRACT FROM PUBLISHER]

Nanocarbons, which have been obtained by controlling the structure and bonding nature at the nanometer scale, can provide highly functional performances. Carbon nanotubes and vapor grown carbon fibers of diameter less than 100 nm can have quantum effects, which are very different from those of conventional carbon fibers. In this paper, preparation and properties of nanocarbon, are demonstrated and discussed. [ABSTRACT FROM PUBLISHER]

We investigated the stable structures, electronic and Li-adsorption properties of C 54 H 18 and its substituted sheets X 2 C 52 H 18 (X=B, N, Si, P, S, Al and F) by a semiempirical molecular orbital method. The F 2 C 52 H 18 sheet was found to have a unique structure and adsorb more Li atoms than the other sheets. This result suggests that the F-substitution into disordered carbons may increase the Li-storage in disordered carbons. [ABSTRACT FROM AUTHOR]

Nanocarbons, which have been obtained by controlling the structure and bonding nature at the nanometer scale, can provide highly functional performances. Carbon nanotubes and vapor grown carbon fibers of diameter less than 100 nm can have quantum effects, which are very different from those of conventional carbon fibers. In this paper, preparation and properties of nanocarbon, are demonstrated and discussed. [ABSTRACT FROM AUTHOR]

To clarify the effect of atom substitution on electronic and lithium (Li) adsorption properties of disordered carbons, we employed circum-coronene (C54H18) as a model cluster for disordered carbons and investigated the stable structures, electronic and Li-adsorption properties of its sulfur-, phosphorus- and silicon-substituted sheets, by using a semiempirical molecular orbital method. Among the three substituted sheets, the silicon-substituted Si2C52H18 sheet was found to have desirable properties as an anode material of rechargeable Li-ion batteries: planar structure and large amount of Li adsorption. Although the Li-adsorption energy of Si2C52H18 is smaller than that of B2C52H18, the dependence of adsorption energy on the number of Li atoms indicates that Si2C52H18 can adsorb more Li atoms than B2C52H18. Therefore, silicon- as well as boron-substituted disordered carbons are expected to be promising materials for the anode in Li-ion batteries. [Copyright &y& Elsevier]

To obtain a new electroconductive composite, the vapor-grown carbon fiber (VGCF) has been applied to the thermoplastic resin composite as a conductive filler. The stability of electrical conductivity of the composite is investigated. The resistivity of VGCF composite is 1.7 x 10-1 ω-cm at room temperature which is one order smaller than that of commercial grade composites with carbon filler. The stability of electrical conductivity, under temperature change (-35 to +60°C) and for exposure tests (at room temperature and at 60°C), the VGCF composites have high degree of stability. The stability of electrical conductivity of the present composites are superior to those of conventional carbon fibers such as PAN-based, under tensile stresses and bending stresses. It is suggested that the fine conductive networks in the present composites give rise to these desirable performances. [ABSTRACT FROM AUTHOR]

Focuses on the development of silicon carbide new ceramics with high thermal conductivity and insulating resistance. Formation of fine silicon carbide powder; Integrated circuit packaging.

In this study, using high-crystallinity VGGF as the virgin graphite, the second-stage type (C2F)n fibers were formed and their structures were analyzed by X-ray diffraction and SEM. To obtain a primary lithium battery with high potential, its application to an anode activator was investigated. Thus the potential of the resulting battery was found to be 0.3 V higher than that of a conventional lithium battery. In addition, the flatness of the discharge potential was excellent. This paper will compare this new type of battery and the conventional (CF)n Li primary battery. [ABSTRACT FROM AUTHOR]

This article provides information on a study that examined the electrical conduction of carbon black (CB). Information is presented on the method used to measure the electrical resistivity of the CB samples. The structure of electrically conductive CB is discussed, as well as current-voltage characteristics of the samples.

Data science has been rapidly developed and implemented in diverse scientific and technological fields over the past decade, to accelerate new knowledge generation and develop high‐impact applications. Recently, different data science tools and techniques have been widely used, such as optimizations, regressions, and classifications of data (tabular, spectral, or visual). In this review, data science tools and techniques are discussed for their adoption for the synthesis, characterization, and applications of carbon‐based materials. Materials synthesis in conjunction with data science has resulted in optimal growth conditions with desired properties and processing techniques. Regarding characterization, molecular structures can be reconstructed using microscopy images, and a particular property can be predicted based on the other properties of the desired carbon material. Moreover, for the applications of carbon materials, data science has enabled prediction of the water treatment efficiency, classification of electronic signals, prediction of the biological activity, and virus classification. It is clear that by combining data science and carbon‐related materials, it is now possible to accelerate theory‐experimental research in the quest for novel materials and their emerging applications. [ABSTRACT FROM AUTHOR]

We report the production of carbon-based xerogel film without the need for supercritical drying. Xerogel samples were characterized with field emission scanning electron microscopy, nitrogen adsorption/desorption at 77 K, Raman spectroscopy, thermogravimetric analysis, and electrical conductivity and cyclic voltammetry measurements. Experimental results reveal that the film is largely crack free and homogeneous in thickness, and, importantly, has high surface area, large nanopore volume, and an excellent performance for electrical charge storage—both per unit mass and unit volume. These results indicate that the film has potential applications for electrical energy storage devices. [ABSTRACT FROM AUTHOR]

An aqueous TEMPO-oxidized cellulose nanofiber (TOCN) dispersion and aqueous hydrogenated acrylonitrile-butadiene rubber (H-NBR) latex were mixed with or without applying high shear forces. The TOCN/H-NBR mixtures containing TOCN volume ratios of 0–10.0% were then converted to crosslinked composite sheets with peroxide between the H-NBR molecules by hot-pressing. When the aqueous TOCN/H-NBR mixtures were pretreated with high shear forces, the crosslinked TOCN/H-NBR composites exhibited concomitant high tensile strength, high tensile modulus, high ductility, high storage modulus, and high dimensional stability to temperature. These properties are better than those of H-NBR composites containing single-walled carbon nanotubes or carbon black at the same filler volume ratio. In the crosslinked TOCN/H-NBR comosites prepared with high shear fodrces as pretreatment, electron microscopy images showed that the TOCN elements were homogeneously dispersed in the H-NBR matrix without forming aggregates. Thermal and pulsed NMR analyses of the solvent-extracted residue of the non-crosslinked TOCN/H-NBR composite indicated that characteristic nanostructures formed in the TOCN/H-NBR interfacial phases, which may cause the excellent mechanical and thermal properties of the composite. Image 1 [ABSTRACT FROM AUTHOR]

Nickel-coated carbon nanofibers have been prepared by an electroless deposition process. The carbon nanofibers were pre-treated prior to the nickel electroless deposition. Polyacrylic acid was used to disperse carbon nanofibers in the pre-treatment solutions. The carbon nanofibers were coated homogeneously with nickel by the electroless deposition process using an electroplating bath containing sodium hypophosphite as a reducing agent. The process resulted in a powdery-nickel-coated carbon nanofiber material. [Copyright &y& Elsevier]

Carbon nanofiber–copper composite powder is prepared by an electrodeposition process using a copper plating bath containing homogeneously dispersed carbon nanofibers. Particles of the composite with a spiky ball structure are accumulated on the plating electrode during the initial stage of electroplating, and can be separated easily to give a powder carbon nanofiber–copper composite. The particle size can be controlled by selecting appropriate electroplating conditions. [Copyright &y& Elsevier]

Vibration characteristics of double-walled carbon nanotubes (DWCNTs) with conveying fluid are analyzed based on the Euler–Bernoulli beam theory and using the wave propagation approach. The DWCNTs are considered as two nanotube shells coupled through the van der Waals interaction between them. The influences of internal moving fluids, such as flow velocity and mass density of fluids, on the vibration frequency of DWCNTs and the DWCNTs embedded in an elastic matrix are investigated in detail. The effect of matrix surrounding carbon nanotubes is considered as a spring element defined by the Winkler model. In this paper, we consider the double-walled nanotubes with an inner diameter of 2.2 nm and an outer diameter of 3.0 nm. According to this analysis, the numerical results indicate that the vibration frequency for the first mode (mode 1) reduces to zero at a critical flow velocity in the case of higher flow velocity, which coincides with the previous study based on a single beam model. The critical flow velocity is largely affected by the fluid properties and the vibration modes. [ABSTRACT FROM AUTHOR]

Wave propagation approach of single- and double-walled carbon nanotubes conveying fluid is presented through the use of the continuum mechanics. A simplified Flügge shell equations are proposed as the governing equations of motion for carbon nanotubes studied here. For the double-walled nanotubes, the deflection of nested tubes is considered to be coupled through the van der Waals interaction between two adjacent nanotubes. Effects of filled fluid property and nanotube diameter on the wave propagation are investigated and analyzed based on the proposed elastic continuum model. The theoretical investigation may give a useful reference for potential design and application of nanoelectronics and nanodevices. [ABSTRACT FROM AUTHOR]

This paper presents analytical models of wave propagation in single- and double-walled carbon nanotubes, as well as nanotubes embedded in an elastic matrix. The nanotube structures are treated within the multilayer thin shell approximation with the elastic properties taken to be those of the graphene sheet. The double-walled nanotubes are coupled together through the van der Waals force between the inner and outer nanotubes. For carbon nanotubes embedded in an elastic matrix, the surrounding elastic medium can be described by a Winkler model. Tube wave propagation of both symmetrical and asymmetrical modes can be analyzed based on the present elastic continuum model. It is found that the asymmetrical wave behavior of single- and double-walled nanotubes is significantly different. The behavior is also different from that in the surrounding elastic medium. [ABSTRACT FROM AUTHOR]

Background: Colonoscopy is a useful as a cancer screening test. However, in countries with limited medical resources, there are restrictions on the widespread use of endoscopy. Non-invasive screening methods to determine whether a patient requires a colonoscopy are thus desired. Here, we investigated whether artificial intelligence (AI) can predict colorectal neoplasia. Methods: We used data from physical exams and blood analyses to determine the incidence of colorectal polyp. However, these features exhibit highly overlapping classes. The use of a kernel density estimator (KDE)-based transformation improved the separability of both classes. Results: Along with an adequate polyp size threshold, the optimal machine learning (ML) models' performance provided 0.37 and 0.39 Matthews correlation coefficient (MCC) for the datasets of men and women, respectively. The models exhibit a higher discrimination than fecal occult blood test with 0.047 and 0.074 MCC for men and women, respectively. Conclusion: The ML model can be chosen according to the desired polyp size discrimination threshold, may suggest further colorectal screening, and possible adenoma size. The KDE feature transformation could serve to score each biomarker and background factors (health lifestyles) to suggest measures to be taken against colorectal adenoma growth. All the information that the AI model provides can lower the workload for healthcare providers and be implemented in health care systems with scarce resources. Furthermore, risk stratification may help us to optimize the efficiency of resources for screening colonoscopy. [ABSTRACT FROM AUTHOR]

Abstract Nanocomposites formed from the precursor of molecule-based magnets [Cu(opba)]2− [opba = o -phenylenebis(oxamate)] and single-wall carbon nanotubes (SWCNTs) were characterized by X-ray absorption near edge structure (XANES) and X-ray photoelectron spectroscopy (XPS) at Carbon and Nitrogen K edges and Cu L 2,3 edges. The N K XANES, XPS and micro-ATR-FTIR data strongly suggested that [Cu(opba)]2− molecules be flatly bonded onto the surface of the SWCNTs. Therefore, higher charge delocalization and electronic modifications were observed. The presence of a new band at 286.1 eV in the Carbon peak of XPS spectra of nanocomposites was assigned to the Carbon surface of the SWCNTs modified by interaction with the metal complex. The micro-ATR-FTIR data supported by DFT calculations show many changes in the bands related to νC = C and νC = O groups of the metal complex in the nanocomposites. Such changes confirmed that the vibrational properties of the complex also changed due to interaction with the carbon nanotubes. Highlights • XANES and XPS data of (NBu 4) 2 [Cu(opba)]-SWCNT nanocomposites at several atomic edges. • Micro-ATR-FTIR used for studying the metallic complex over SWCNT surface. • Oxamate-based complex have strong interaction with SWCNT by −Cu N− sites. [ABSTRACT FROM AUTHOR]

The article presents a research on the process of producing mesoporous carbon aerogels with hydrophilicity-controlled pore walls. Researchers state that, the process uses carbon dioxide supercritical drying to form interconnected micropores and small mesopores, and at the same time, uses colloidal silica nanocasting to form larger mesopores and increase pore volumes. It is stated that, the controlled removal of the silica from the pore walls increases the nanoporosity of the walls.

Carbon solubility in the catalyst for the growth of graphene-type nanomaterials is an essential issue for their large-scale fabrication. Iron compounds are fundamental catalysts for the synthesis of carbon materials. The carbon solubility of ferrite (α-Fe) is ∼0.1% at 700 °C, which is enough to promote the growth of graphene nanomaterials. In this work, we synthesized crystalline multilayer graphene flakes (MLGFs) by a two-step catalytic chemical vapor deposition method using an α-Fe catalyst derived from the reduction of nanostructured hematite at 950 °C under an Ar–H 2 environment. In the first step, nitrogen-doped multi-walled carbon nanotubes were synthesized by a benzylamine-ferrocene mixture at 850 °C and oxidized at 620 °C in air. In the second step, the reduced nanostructured hematite was exposed to a mixture of a 1:9 benzylamine-1,2- dichlorobenzene at 950 °C. Raman spectroscopy confirmed the presence of MLGFs with a G band and a significant 2D band intensity. The results of the thermogravimetric analysis show that the maximum oxidation rate was at 643.5 °C. Additional functional density calculations were performed considering graphene growth on the oriented (110) α-Fe surface. This work reasserts the possibility of using alternative carbon sources for graphene growth. N-MWCNTs are oxidized in the air at a temperature of 620 °C to form nanostructured hematite (Fe 2 O 3), which is reduced at 950 °C under an Ar/H 2 flow to obtain nanostructured high carbon solubility γ-Fe. Then a nebulized mixture of benzylamine-1,2 dichlorobenzene flows to carbon-saturated it. Finally, by cooling producing the MLGFs. [Display omitted] • The use of nanostructured Fe-based catalyst for producing MLGFs. • Nebulized carbon precursors containing nitrogen and chloride atoms for synthesis MLGFs. • Electrochemical studies show MLGFs potential uses where extensive electron transfer capability is a necessary process. [ABSTRACT FROM AUTHOR]

The present study aims at developing a silicon/soft-carbon nanohybrid material for high performance lithium-ion battery (LIB). It is composed of micronized silicon coated with so-called “soft-carbon” dispersed in soft-carbon matrix at nanometer level. This material is characterized with abundant nanosized voids with diameter of ca. 70 nm and hard bulk skeletal structure. It exhibited a long cycle life of 163 charging and discharging cycles with a large capacity of 850 mAh/g and retention rate up to 90% of the initial capacity in a half cell with Li-metal counter electrode. For this new material, the volume expansion ratio was 6.9% at a capacity level of 1100 mAh/g. This electrode capacity is approximately three times larger than that of graphite-based electrode currently used in LIB. Furthermore, this electrode retained 80.9% of its capacity at 250 cycles in a full cell with a LiCoO 2 counter electrode. Addition of 5 wt % fluoroethylene carbonate (FEC) to the electrolyte improved the retention up to 81.3% after 300 cycles. These results demonstrate the usefulness and high possibility of this material as the negative electrode of LIB. [ABSTRACT FROM AUTHOR]

[Display omitted] • The effects of heat treatment on the electrical transport properties of polyacrylonitrile-based carbon fibers. • The structural transition affects the temperature dependence of the electrical resistance and the magnetoresistance. • A peculiar metallic transport behavior due to the band overlaps. The effects of heat treatment temperatures from 1000 to 2700 °C on the structural, chemical, and mechanical properties of polyacrylonitrile-based carbon fibers (CFs) were investigated. Structural changes affected mechanical properties, and in particular, a higher sp 3 content induced a higher tensile strength below 1600 °C. For a comprehensive study on the heat treatment effect and the mechanism for developing high-strength CFs, electrical transport properties were measured for the CFs. The transport behaviors in temperature-dependent conductivity and magnetoresistance were also significantly modified, which led to crossover from strong localization to weak localization due to sp2 carbon ordering. Interestingly, in samples that were subjected to intermediate heat treatment temperatures ranging from 1100 to 1600 °C, anomalous metallic temperature-dependent behavior was observed at low temperatures of below 40 K. This unusual charge transport was analyzed further with a pertinent heterogeneous model employing three-dimensional variable range hopping, weak localization, and linear metallic transport. The results suggest that mixed noncrystalline and crystalline structures with sp2/sp3 carbons, oxygen, and quaternary N groups in CFs enabled the transition behavior at such low temperatures. [ABSTRACT FROM AUTHOR]

Rubber/nanocellulose composite sheets improve tensile properties compared with neat rubber sheets, when nanocellulose materials are suitably compounded with rubber matrices. First, two oven‐dried nanocellulose materials containing different additive components were prepared from nanocellulose/water dispersions, and the oven‐dried nanocellulose‐containing materials were compounded with rubber sheets under high shear forces by using a two‐roll mill. The tensile moduli and strength of the rubber/nanocellulose composite sheets were clearly better than those of the rubber sheet prepared without nanocellulose, while the elongations at break were similar. Thin films were cut from the rubber/nanocellulose composite sheets, and their real‐time tensile deformation processes were observed by transmission electron microscopy (TEM) to understand the time‐dependent patterns of crack propagation, void formations, and fusion between cracks and voids in the composites during tensile deformation. TEM observations showed that the composite sheets consisted of individual rubber/nanocellulose clusters. Voids initially formed inside the rubber/nanocellulose clusters, propagated to form cracks, fused with other voids or secondary cracks. There were slight differences between the crack‐propagation patterns of the two rubber composites, probably because of differences in the morphologies, sizes, distributions, and structures of the rubber/nanocellulose clusters, and surface chemical structures of individual nanocellulose elements between the composites. [ABSTRACT FROM AUTHOR]

Sponge-type nitrogen-doped multiwall carbon nanotubes (N-MWCNTs), synthesized via an aerosol-assisted catalytic chemical vapor deposition (AACCVD) method, were extensively studied. A ball-milled and oxidized red-leptosol (RL) was used as the catalyst precursor, and benzylamine worked as a carbon and nitrogen source. The ball-milled and oxidized RL increased their contact area and purity for the N-MWCNT synthesis. X-ray diffraction characterization revealed that raw RL contained kaolinite, quartz, graphite, hematite, and goethite. According to the electron microscopy analysis, the N-MWCNTs exhibited exotic morphologies and microstructures. The high-resolution X-ray photoelectron spectroscopy showed that the as-grown N-MWCNTs contained pyrrolic and pyridinic nitrogen species. The cyclic voltammetry studies demonstrated that the redox processes in the N-MWCNTs in 0.1 M H 2 SO 4 were dominated by the carboxyl, pyridinic, and pyrrolic groups. Using the natural RL as a catalyst precursor in AACCVD led to a large yield of N-MWCNTs mixed with different minerals, causing the observed morphologies and influencing the electrochemical behavior, which is of interest in energy-storage and sensing applications. Sponge-type nitrogen-doped multiwall carbon nanotubes (N-MWCNTs) synthesized by aerosol-assisted catalytic chemical vapor deposition using benzylamine as carbon and nitrogen sources and a red leptosol as a catalyst precursor. Cyclic voltammetry studies found pyrrolic-N, pyridinic-N, and oxygen groups as the leading chemical surface reactant groups for redox processes. [Display omitted] • A facile route to produce sponge-type nitrogen-doped multiwall carbon nanotubes using a low-cost red-leptosol as catalyst. • Soil minerals in red-leptosol enhance the yield of N-MWCNT. • The synthesized N-MWCNTs show promising properties for electrochemical devices. • CNT morphologies exhibit unusual structures. [ABSTRACT FROM AUTHOR]

In article number 2100205, Morelos-Gomez, Terrones and Endo explore how, with the aid of tools from data science, carbon nanomaterials research and development can accelerate in three key experimental areas: synthesis, characterization, and applications. B Data Science Applied to Carbon Materials b Carbon materials have been the main subject for two Nobel prizes; they exhibit excellent physical and chemical properties that have been used in diverse applications. Data Science Applied to Carbon Materials: Synthesis, Characterization, and Applications (Adv. [Extracted from the article]

Acidic functional groups produced on the surface of acid-treated multi-walled carbon nanotubes (MWCNTs) were quantified by fluorescence measurements using 1-aminopyrene (1-AP) as an in situ probe molecule. The 1-AP cation-like bands were observed on the HNO3/H2SO4 mixture-treated MWCNT surfaces because the 1-AP molecule was tightly immobilized by the hydrogen bonding interaction between its amino group and the Brönsted-acidic groups on the MWCNT surface. The fluorescence measurement allowed us to confirm the Langmuir-type adsorption of 1-AP on the functional groups of the MWCNTs, and estimate their amount of the functional groups and adsorption equilibrium constant. A longer acid treatment caused the chemical modification to generate higher amounts of the Brönsted-acidic functional groups and improve the adsorption ability on the MWCNT surface. About 2% of carbon in the MWCNTs was oxidized by the 24h acid treatment. This value corresponded to 15–22% of carbon in the surface layer. [ABSTRACT FROM AUTHOR]

Vertical graphene (VG) sheets, which consist of few-layer graphene vertically aligned on the substrate with three-dimensionally interconnected porous network, make them become one of the most promising energy storage electrodes, especially for SCs. Nevertheless, the intrinsic hydrophobic nature of pristine VG sheets severely limited its application in aqueous SCs. Here, electrochemical oxidation strategy is adopted to increase the hydrophilicity of VG sheets by introducing oxygen functional groups so that the aqueous electrolyte can fully be in contact with the VG sheets to improve charge storage performance. Our work demonstrated that the introduction of oxygen functional groups not only greatly improved the hydrophilicity but also generated a pseudocapacitance to increase the specific capacitance. The resulting capacitance of electrochemically oxidized VG for 7 min (denoted as EOVG-7) exhibited three orders of magnitude higher (1605 mF/cm2) compared to pristine VG sheets. Through assembled two EOVG-7 electrodes, a symmetric supercapacitor demonstrated high specific capacitance of 307.5 mF/cm2, high energy density of 138.3 μWh/cm2 as well as excellent cyclic stability (84% capacitance retention after 10000 cycles). This strategy provides a promising way for designing and engineering carbon-based aqueous supercapacitors with high performance. The electrochemical oxidation strategy is adopted to increase the hydrophilicity of VG sheets by introducing oxygen functional groups so that the aqueous electrolyte can fully be in contact with the VG sheets to enhance electrochemical charge storage performance. The introduction of oxygen functional groups not only greatly improved the hydrophilicity but also generated a pseudocapacitance to increase the specific capacitance, further improve the energy density. [Display omitted] • Electrochemical oxidation method can significantly increase the functional groups on the surface of VG. • The hydrophilicity and additional pseudocapacitance are generated on surface-functionalized VG. • The optimized oxygen functional groups of VG surface can improve capacitance. • The symmetric SC shows excellent energy density (138.3 μWh/cm2), long-term cycle stability (84 %) and voltage of 1.8 V. [ABSTRACT FROM AUTHOR]

Vacancy activated BN is able to spontaneously reduce various metal ions (Ag, Pt, Au, Cu, Fe) without any reducing agents to form metal-BN heterostructures. It further allows the activated BN as the catalyst support for Pt based single atom catalysis, such as hydrogen evolution reaction. [Display omitted] Hexagonal boron nitride (hBN) has long been considered chemically inert due to its wide bandgap and robust covalent bonds. Its inertness hinders hBN from functionalization for energy conversion applications. A question arising is whether it is possible to make hBN chemically reactive. Here, we report cryomilling in liquid N 2 , as an effective strategy to activate the chemical reactivity of hBN by engineering different vacancies to produce defective-BN (d-BN). The local reactivity of the vacancies is probed by photoluminescence (PL) emissions and electron spin resonance spectroscopy (ESR). Density functional theory calculations reveal that the formation of different vacancies with/without oxygen cause the creation of mid-gap states that are responsible for the PL emissions in the visible region. These vacancies also generate localized free radicals which are both theoretically and experimentally confirmed by spin density calculations and ESR. Due to the vacancy induced free radicals and Fermi level shifts, d-BN can be controllably functionalized with single metal atoms by the spontaneous reduction of metal cations; mono-metallic or bi-metallic clusters can also be effectively reduced. As a proof of concept, the surface-bound metal nanostructures, especially substrate confined single metal atoms, exhibit improved hydrogen evolution catalytic performance, and can be further used for sensing, and quantum information. [ABSTRACT FROM AUTHOR]

A resorcinol resin/water dispersion and a rubber latex are added to 1% 2,2,6,6,‐tetramethylpyperidine‐1‐oxyl (TEMPO)‐oxidized cellulose nanofibers (TEMPO‐CNFs) dispersed in water, followed by oven drying at 40 °C for 20 h to prepare a dried TEMPO‐CNF/resorcinol resin/latex rubber (DTRL) mixture with a weight ratio of 1/0.5/3. DTRL is then added to a nitrile‐butadiene rubber (NBR) or a carboxy group‐containing NBR (X‐NBR) sheet, and the mixture is kneaded by a two‐roll mill at 20–30 °C with high shear forces. The tensile strength and Young's modulus of the crosslinked DTRL/rubber composite sheets remarkably increased from 10 and 12 MPa, respectively, for the reference sheet to 24 and 82 MPa, respectively, for the DTRL/rubber composite sheets containing ≈10 vol% TEMPO‐CNFs. Scanning electron microscopy revealed that no TEMPO‐CNF agglomerates are present in the DTRL/rubber composite sheets. The tensile properties of the composite sheets are the best when a X‐NBR sheet and NBR latex are used as the matrix rubber and latex in DTRL preparation, respectively. When water‐extracted DTRL (WDTRL, mass recovery ratio ≈94%) is used in place of DTRL, the WDTRL/rubber composite sheets show sufficient water resistance, while the tensile properties are almost the same as those of the DTRL/rubber composite sheets. [ABSTRACT FROM AUTHOR]

Abstract: The instability of single-walled carbon nanotubes (SWCNTs) under compressive loading has been observed experimentally by TEM and may limit their performance and structural integrity as atomic force microscopy (AFM) tips. Double-walled carbon nanotubes (DWCNTs) with inner and outer nanotubes of different lengths are proposed as AFM probes, and a theoretical approach based on a nanobeam model is developed for investigating the critical buckling stress of the DWCNTs under an axial compressive load. The influence of structural parameters on the buckling stress of DWCNT AFM probes are analyzed using this approach. The results show that the influence of the length mismatch between inner and outer nanotubes, as well as buckling modes on the buckling stress of DWCNTs was significant. [Copyright &y& Elsevier]

Abstract: Ni–P alloy/multiwalled carbon nanotube (MWCNT) composite films were fabricated on acrylonitrile butadiene styrene (ABS) resin by electroless plating and their microstructures, adhesion strengths, and friction properties were investigated. Various types of MWCNTs were used. In addition, various electroless plating baths were prepared to form Ni–P alloy matrices with various phosphorus contents. To enhance the adhesion strength, the ABS resin substrate was subjected to roughening treatment. The microstructures of the composite films were examined by scanning electron microscopy and X-ray diffraction. Their adhesion strengths were measured by tensile tests. The friction properties of the composite films were investigated using the ball-on-plate method. Ni–P alloy/MWCNT composite films containing various types of MWCNTs and with Ni–P alloy matrices having various phosphorus contents were fabricated on the ABS resin substrates by electroless deposition. The adhesion strength between the Ni–P alloy/MWCNT composite films and the ABS resin substrate was more than 1300Ncm−2. The Ni–P alloy/MWCNT composite films had considerably lower friction coefficients than the Ni–P alloy films. The friction coefficients of the composite films were significantly affected by the type of MWCNTs used. [ABSTRACT FROM AUTHOR]

Abstract: Ni–P alloy–carbon black (CB) composite films were fabricated by electroplating and their microstructures and properties were examined. The CB and phosphorus contents of the composite films were also investigated. The CB particles were found to be embedded in the Ni–P alloy matrix. The CB content in the deposits increased, reached a maximum value of 0.77mass% with increasing CB concentration in the bath up to 10gdm−3, and then decreased with a further increase in the CB concentration in the bath. Both before and after heat treatment, the composite films had higher hardnesses and lower friction coefficients than the Ni–P alloy films. Both before and after heat treatment, the friction coefficient of 0.77mass% CB composite films was about half that of Ni–P alloy films without CB. [Copyright &y& Elsevier]

Abstract: The induced electric-field has been applied to measure the elastic modulus of carbon nanotubes. However, the vibrational modes of the multi-walled carbon nanotubes are quite different from those of the single-walled carbon nanotubes. Analysis of the vibration characteristics of double-walled carbon nanotubes (DWCNTs) with simply supported boundary condition are carried out based on Euler–Bernoulli beam theory. The DWCNTs are considered as two nanotube shells coupled through the van der Waals interaction between them. It is found that the vibrational modes of DWCNTs are noncoaxial intertube vibrations, and the deflections of the inner and outer nanotubes can occur in the same or in opposite deflections. In the same vibrational mode, the resonant frequencies of DWCNTs with deflections between the inner and outer nanotubes in the same direction are smaller than those of DWCNTs with the opposite deflections. [Copyright &y& Elsevier]

Abstract: This paper presents the effect of interface on the equivalent thermal conductivity of the carbon nanotube composites. The element free Galerkin method has been utilized as a numerical tool to evaluate the thermal conductivity of the composites. The numerical results have been obtained using continuum mechanics approach for a model composite problem, and it was found that the interface has a major effect on the thermal conductivity of the composites. The effect of interface on the effective conductivity of the composite is small for short nanotubes as compared to long nanotubes. Interface thickness also plays an important role on the effective thermal conductivity of the composite. Nanotube anisotropy has got a small effect on effective thermal conductivity of the composites. Transverse thermal conductivity of the composite has got nearly linear variation with nanotube length. [Copyright &y& Elsevier]

Abstract: Rubber composite sheets filled with 5wt.% and 30wt.% of highly aligned carbon nanotubes (CNTs) were fabricated through conventional rubber technology. The alignment of CNTs was possibly derived from dragged shear force during the optimized milling process. The selective alignment of CNTs led to enhancements in the elastic modulus, thermal conductivity, electrical conductivity, and electromagnetic shielding property, compared to neat rubber sheet. [Copyright &y& Elsevier]

Abstract: The multi-walled carbon nanotubes (MWCNTs, mean diameter: 100–200nm) with nickel–phosphorous (Ni–P) coatings were obtained by an electroless deposition process. To prepare the MWCNTs covered with continual Ni–P layers, a pre-treatment procedure comprised of acid-cleaning, sensitization and activation has been developed. The resulting MWCNTs have a uniform distribution of the Ni–P layers coated on the MWCNTs with the fibrous appearance maintained. X-ray diffraction (XRD) and transmission electron microscopy (TEM) observations revealed that the as-coated MWCNTs were comprised of the amorphous Ni–P layers and inner carbon nanotubes covered with the Ni–P layers. These amorphous Ni–P-coated MWCNTs were used as precursors for preparing MWCNTs with nanocrystalline Ni–P(crystalline Ni and Ni3P intermetallic compound) layers by the heat-treatment above 400°C, which were determined by differential scanning calorimeter (DSC) and XRD studies. The results of this work provide an effective electrochemical method for preparing powdery MWCNTs with Ni–P layer as new composite materials from the aqueous solution. [Copyright &y& Elsevier]

Abstract: Nickel–carbon nanofiber composites were synthesized by means of pulse-reverse (PR) electrodeposition technique from a standard Watts nickel plating bath using a cationic polymer as the dispersing agent of nanofibers. The obtained composites were characterized by electron probe X-ray microanalyzer, field-emission scanning electron microscope and X-ray diffractometer to demonstrate their microstructures. Results clearly showed that the composites were formed as the continuous films filled by a large amount of individual Ni-coated nanofibers with a closely packed arrangement. The PR electrodeposition enhanced the carbon nanofiber concentration compared to the DC electrodeposition in the nickel–carbon nanofiber composites. The morphological features and the composition of composites exhibited controllable characters by selectively modulating the PR electrodeposition parameters. [Copyright &y& Elsevier]