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Carbon nanotube (CNT) reinforced Al composite foams with different CNT contents are fabricated through an improved powder metallurgy approach by combining in-situ chemical vapor deposition (CVD), short time ball-milling, and space-holder method. The CNTs are uniformly dispersed on the surface of Al particles by in-situ CVD process, followed by a short time ball-milling process enabling an excellent interfacial bonding between CNTs and the Al matrix. The pore size and microstructures of the composite foams can be well tailored by the carbamide particle templates. The yield strength and energy absorption capacity of composite foams reach 18.1 MPa and 15.8 MJ m−3 with 3.0 wt% CNT addition, which are ≈1.3 and ≈3.6 times higher than those of pure Al foam, respectively. The energy absorption efficiency of the CNT/Al composite foams achieves a maximum of ≈0.86, when the CNT content is up to 3.0 wt%. Additionally, compressive and energy absorption properties of the CNT/Al composite foams increase with the increment of relative density. The failure mode of the Al foam changes from plastic mode to brittle mode combined with ductile mode, as a result of CNT addition. [ABSTRACT FROM AUTHOR]

High energy density and power density within a limited volume of flexible solid-state supercapacitors are highly desirable for practical applications. Here, free-standing high-quality 3D nanoporous duct-like graphene (3D-DG) films are fabricated with high flexibility and robustness as the backbones to deposit flower-like MnO2 nanosheets (3D-DG@MnO2). The 3D-DG is the ideal support for the deposition of large amount of active materials because of its large surface area, appropriate pore structure, and negligible volume compared with other kinds of carbon backbones. Moreover, the 3D-DG preserve the distinctive 2D coherent electronic properties of graphene, in which charge carriers move rapidly with a small resistance through the high-quality and continuous chemical vapor deposition-grown graphene building blocks, which results in a high rate performance. Marvelously, ultrathin (≈50 μm) flexible solid-state asymmetric supercapacitors (ASCs) using 3D-DG@MnO2 as the positive electrode and 3D hierarchical nanoporous graphene films as the negative electrode display ultrahigh volumetric energy density (28.2 mW h cm−3) and power density (55.7 W cm−3) at 2.0 V. Furthermore, as-prepared ASCs show high cycle stability clearly demonstrating their broad applications as power supplies in wearable electronic devices. [ABSTRACT FROM AUTHOR]

The damping properties of Al matrix composite foams reinforced by in-situ grown carbon nanotubes (CNTs) have been investigated. The results show that the damping capacity of the CNT/Al composite foams is visibly enhanced with the CNT addition. The loss factors of the composite foams are found not only increase with the increment of CNT content but also increase with the porosity raising. For the 3.0 wt%-CNT/Al composite foams, the loss factor keeps the level of ∼0.26 at 25–200 °C and further increases to 0.36 when the temperature is elevated to 390 °C, which is ∼2.71 and 1.77 times higher than that of the pure Al foam, respectively. The damping improvement of CNT/Al composite foams is mainly due to the high inherent damping of CNTs and the formation of large numbers of well-bonded CNT-Al interfaces. [ABSTRACT FROM AUTHOR]

Abstract: Novel binary and triple carbon nanotubes (CNTs) with one common catalytic particle encapsulated have been synthesized using Ni/Cu/Al2O3 catalyst, which was produced by a sol–gel method. But when using Ni/Al2O3 as catalyst, a mass of common CNTs, that is, one CNT with one catalytic particle encapsulated, was obtained. The results showed that copper-element doping to the Ni/Al2O3 catalyst played a key role in the synthesis of CNTs, signifying a novel approach to modify the Ni/Al2O3 catalyst. Based on the transmission electron microscopy observations, a simple growth mechanism was developed to describe the growth of the binary or triple CNTs, which could be well explained by a diffusion segregation process. [Copyright &y& Elsevier]

Abstract: The initial stage growth of bamboo-shaped carbon nanotubes (CNTs) synthesized by catalytic decomposition of methane is investigated. A special experimental procedure has been developed to stop the process after short durations (0s to 3min). It has found that during the early stages (60s), carbon cluster-encapsulated nanoparticles are formed. With prolonging synthesis time (3min), some CNTs coexisted with carbon cluster-encapsulated nanoparticles are formed. HRTEM observations show that these CNTs display multi-walled and bamboo structure and the encapsulated catalytic particles are quasi-cone morphologies. At the same time, the catalytic particles only encapsulated with carbon clusters present quasi-sphere structures. For growth up to 60min, two kinds of bamboo mode structures are observed: conical, and cylindrical, which are developed by quasi-cone and quasi-sphere catalytic particles, respectively. Moreover, the early stage growth mode of the CNTs is predominantly of the base growth mode according to TEM observations. [Copyright &y& Elsevier]

Abstract: The possibility of using aluminum powder as transition metal catalyst carrier for CVD growth of carbon nanotubes (CNTs) has been investigated. The fabrication process of Ni/Al catalyst involved the production of binary colloid (Ni(OH)2/Al) by deposition–precipitation method, followed by calcination in N2 and reduction in H2. The nickel particles obtained were with uniform diameters. After the catalytic synthesis at 600°C a mass of well-graphitized multi-walled CNTs with the diameters in the 10–20nm range have been obtained, as evidenced by HRTEM. The operated catalytic particle encapsulated in CNT was nickel according to EDX analysis. However, when using pure nickel without aluminum as the catalyst, no CNTs have formed due to the agglomeration of Ni particles. Thus we speculated that the aluminum powder was responsible for the formation and the even dispersion of the nano-scale transition metal particles. [Copyright &y& Elsevier]

Abstract: A mass of carbon onions have previously been successfully synthesized via catalytic decomposition of methane using nitrogen as a carrier gas over a Ni/Al catalyst. In this study, X-ray photoelectron spectroscopy characterization of the carbon onions shows that the as-grown carbon onions contained nitrogen and that the nitrogen concentration in the carbon onions increased with an increase in reaction time. When hydrogen is used as a carrier gas, it is found that no carbon onions are obtained, indicating that the carrier gas plays an important role in the synthesis of carbon onions and that there is an intimate relationship between carbon onion growth and nitrogen incorporation. [Copyright &y& Elsevier]

Abstract: Ni/Al catalysts with different Ni concentrations have been used successfully for the synthesis of carbon nanotubes and onions from methane by chemical vapor deposition. The catalyst nanoparticles were produced by a deposition–precipitation method, and the carbon products by the catalytic decomposition of methane at 600°C. Carbon nanotubes (CNTs) were formed in the presence of a Ni/Al composite catalyst containing 20wt.% nickel. The CNTs were multi-walled, 10–20nm in diameter and up to 15μm long. Hollow carbon onions were produced in the presence of a Ni/Al composite catalyst containing 80wt.% nickel. The carbon onions were from 5 to 50nm in diameter and consisted of several concentric carbon layers surrounding a hollow core. The mechanisms for the formation of both the CNTs and carbon onions were discussed on the basis of the experimental results. [Copyright &y& Elsevier]

In article number 1600755, Enzuo Liu, Naiqin Zhao, and co‐workers report ultrathin flexible solid‐state asymmetric supercapacitors using 3D nanoporous duct‐like graphene @ MnO2 films as the positive electrode and 3D hierarchical nanoporous graphene films as the negative electrode that display ultrahigh volumetric energy and power densities, demonstrating broad applications as power supplies in wearable electronic devices. [ABSTRACT FROM AUTHOR]

Review: 85 refs. [ABSTRACT FROM AUTHOR]

Abstract: A mass of carbon nanotubes with straight and short bodies was produced by chemical vapor deposition of methane over Ni/Al2O3. Scanning electron microscopy, transmission electron microscopy and thermogravimetric analysis were used to analyze the synthesized carbon nanotubes. The results showed that they were well-graphitized multi-walled nanotubes and had not tangled together. Their average length was several hundreds of nanometers, suitable for their use as a nanometer-scale material. [Copyright &y& Elsevier]

Abstract: Changes in the thermogravimetrically determined oxidation behaviors of CVD-grown multi-walled carbon nanotubes (MWNTs) over Ni/Al catalyst with different Ni content were examined. Catalyst type was found to have a measurable impact upon nanotube stability, suggesting differing levels of crystalline perfection in the resulting nanotubes. With increasing the Ni content in the Ni/Al catalyst, the CNTs obtained became less stable during heat treatment in air. Furthermore, high-resolution transmission electron microscopy was employed to investigate the defect sites of as-grown MWNTs. The results provide evidence showing that defect sites along the walls and at the ends of the raw MWNTs facilitate the thermal oxidative destruction of the nanotubes. [Copyright &y& Elsevier]

Abstract: Straight carbon nanotubes, carbon onions and two kinds of herringbone carbon nanofibers have been synthesized over nickel supported on aluminum matrix by catalytic decomposition of methane. Nickel precipitated on the aluminum matrix was used as catalyst, which only had 5wt.% nickel. Through varying the production parameters such as the carrier gas, reaction temperature and reaction time, various morphologies of nanocarbons were obtained, which will be employed to reinforce aluminum matrix composites and thus the aluminum matrix composites obtained will have different potential applications. [Copyright &y& Elsevier]

The difficulty of dispersing high content of graphene nanoplatelets (GNPs) in the metal matrix limits the strengthening efficiency of GNPs reinforcement. Herein, high content GNPs were synthesized on the surface of Cu powders using chemical vapor deposition with solid carbon source incorporating impregnation-reduction route, which made GNPs uniformly dispersed and improved the interfacial bonding between GNPs and Cu matrix. Then, the composites were densified by vacuum hot pressed sintering followed by multi-step hot rolling process, during which the orientation distribution of GNPs was achieved. After a rolling reduction of 70%, the composite materials containing 12 vol% GNPs were increased by 44% in yield strength (256 MPa) compared with that of pure Cu (178 MPa). Furthermore, the in-plane thermal conductivity was increased by 17% (441 W/mK) when the GNPs content is 15 vol%. This work sheds light on designing structural and functional integrated Cu matrix composites. Unlabelled Image • High content graphene nanoplatelets reinforced Cu matrix composites were fabricated. • The graphene nanoplatelets are uniformly dispersed and oriented. • The composites have high thermal conductivity and good mechanical properties. [ABSTRACT FROM AUTHOR]

Developing high-capacity anodes with fast kinetics and stable structure is critical for the effective implementation of sodium ion capacitors (SICs). In this study, Fe 2 O 3 @C nanoparticles modified vertically aligned carbon nanotubes (VACNTs) composites are designed and employed as SIC anodes through a two-step chemical vapor deposition (CVD) process with the aid of a refined Fe 3 O 4 /AlO x dispersion catalyst. With nano-sized Fe 2 O 3 coated with defected carbon layers sufficiently loading onto the VACNTs substrates, the resulting composites demonstrate remarkable sodium storage properties, with a high areal specific capacity (1.26 mAh cm−2 at 0.2 mA cm−2) and rate performance (0.19 mAh cm−2 at 5.0 mA cm−2). Moreover, continuous capacity promotion is observed over 1000 cycles, leading to superior cycling performance (0.444 mAh cm−2 at 1 mA cm−2), with 178% retention after 1000 cycles. This improved cycling performance is attributed to the defective structure and high specific surface area of the VACNTs, which accommodates the volume change of the Fe 2 O 3 particles. In addition, the induced locally graphitization and rearrangement of the carbon layers are demonstrated, which results in better kinetics for Na+ transfer, further enhancing capacity retention over long cycles. [Display omitted] • Fe 2 O 3 @C/VACNTs composites realized superior synergistic effect. • Sustained increasing for capacities were obtained by modifying nano-sized Fe 2 O 3 @C. • Refined Fe 2 O 3 paritcles and Na + insertion inducing graphtization was investigated. [ABSTRACT FROM AUTHOR]

The design of the electrode materials for supercapacitors with high volumetric utilization and excellent capacitance is in high demand. In this study, the three dimensional porous hierarchical nickel cobalt layered double hydroxides (NiCo-LDH) grown on the nanotubular Ni supported N-doped graphene (ntN-NG) matrix are fabricated via chemical vapor deposition process combined with hydrothermal method. The ntN-NG substrate with low void content, high specific surface area, appropriated pore size and a hydrophilic surface facilitates the effective nucleation and robust growth of hierarchical NiCo-LDH, and thus, ensures high material loading in a limited space and the structure stability of the composite. The hybrid exhibits a record high volumetric capacitance of 867 F/cm 3 at 1 mA/cm 2 and remarkable cycling stability of 89.4% retention after 10,000 cycles, which holds great promising application as the miniaturized energy storage and conversion devices in the future. [ABSTRACT FROM AUTHOR]

Silica (SiO 2 ) is regarded as one of the most promising anode materials for lithium ion batteries owing to its high theoretical specific capacity, relatively low operation potentials, abundance, environmental benignity and low cost. However, the low intrinsic electrical conductivity and large volume change of SiO 2 during the discharge/charge cycles usually results in poor electrochemical performance. In this work, carbon nanotubes (CNTs) modified SiO 2 /C composites have been fabricated through an in-situ chemical vapor deposition method. The results show that the electrical conductivity of the SiO 2 /C/CNTs is visibly enhanced through a robust connection between the CNTs and SiO 2 /C particles. Compared with the pristine SiO 2 and SiO 2 /C composites, the SiO 2 /C/CNTs composites display a high initial capacity of 1267.2 mA h g −1 . Besides, an excellent cycling stability with the capacity of 315.7 mA h g −1 is achieved after 1000th cycles at a rate of 1 A g −1 . The significantly improved electrochemical properties of the SiO 2 /C/CNTs composites are mainly attributed to the formation of three dimensional CNT networks in the SiO 2 /C substrate, which can not only shorten the Li-ion diffusion path but also relieve the volume change during the lithium-ion insertion/extraction processes. [ABSTRACT FROM AUTHOR]

This work presents an in-situ chemical vapor deposition (CVD) method to synthesis carbon nanotube (CNT) on Al powders in a vertical tube furnace. The carbon nanotube reinforced Al matrix composites (CNT/Al composites) were fabricated by a new powder metallurgy (PM) approach associated with vacuum induction melting technique. It was shown that CNT was homogenously distributed in the Al matrix, and an interfacial transiting layer of Al 4 C 3 was formed between Al matrix and CNT in the bulk material. The tensile test showed that 1.5 vol% CNT/Al composites exhibited the largest tensile strength of 191 MPa as well as an excellent elongation of 32.6%. The strengthening efficiency of the 1.5 vol% CNT/Al composites improved by ~ 80% compared to the unreinforced pure Al. The strengthening mechanisms were mainly attributed to the load transfer of CNT, Al 4 C 3 and dislocation strengthening. The Al 4 C 3 transiting layer was beneficial to increase the interfacial shear strength and prolong the slide deformation of dislocation by forming an orientation relationship of Al 4 C 3 <001> // Al <111> and CNT (002) // Al 4 C 3 (001) according to the transmission electron microscope (TEM) observation. Besides, the thermocycling measurement enriched and deepened the understanding of the effect of Al 4 C 3 on improving the interfacial bonding, degrading the interfacial thermal mismatch between CNT and the Al matrix and increasing the compactness of the CNT/Al composites. [ABSTRACT FROM AUTHOR]

A novel approach is developed for the fabrication of nickel (Ni) matrix composites reinforced by graphene, which involves the synthesis of three-dimensional graphene networks (3D GNs) tightly anchored with Ni nanoparticles (3D Ni@GNs) by an in-situ high-temperature chemical vapor deposition process, subsequent uniform coating of Ni powders around the 3D Ni@GNs by an impregnation-reduction process, and final consolidation of the Ni@GNs/Ni composite powders by spark plasma sintering. Owing to the significant grain refinement and homogeneous dispersion of Ni@GNs in the composites identified through the electron backscattered diffraction, scanning and transmission electron microscopy, the composites exhibited much enhanced mechanical properties; the Ni@GNs/Ni composite with 1.0 vol% GNs was demonstrated a yield strength of 474 MPa and a tensile strength of 546 MPa, ~ 188.4% and ~ 26.0% higher than those of the pure bulk Ni respectively. It was thought that the composites were strengthened by both load transfer from the Ni matrix to the GNs and dispersion strengthening of GNs. Meanwhile, the addition of GNs greatly decreased the grain size of the Ni matrix, leading to a significant grain refinement strengthening for the Ni@GNs/Ni composites. [ABSTRACT FROM AUTHOR]

With the assistance of soluble salt template, we designed and synthesized a Sn-core/CNT-shell nanocable anchored interconnected carbon networks structure via a simple CVD process. The Sn nanorods with a diameter of ∼50 nm are protected by ∼3 nm CNTs. The whole hierarchical structure forms a conductive network, which ensures rapid transportation of electrons. As a result, when utilized as lithium-ion battery anode, the 3DC-Sn@CNT electrode exhibits good cycling stability (700 mAh g −1 after 100 cycles at 0.1 A g −1 ) and rate performance (240 mAh g −1 at 1 A g −1 ). [ABSTRACT FROM AUTHOR]

Carbon nanotube (CNT) reinforced Al composite foams were successfully fabricated by the combination of an in-situ chemical vapor deposition (CVD), short-time ball-milling and space-holder method. The CNTs are homogeneously dispersed and embedded in the Al foam matrix after 90 min ball-milling while maintaining the structural integrity. Both compressive properties and energy absorption capacity of the composite foams increase with the increment of CNT content but decrease with the temperature rising between 25 and 250 °C. The compressive yield strength and the plateau stress of 3.0 wt%-CNT/Al composite foams maintain 16.8 and 20.2 MPa at 150 °C, respectively, which are much higher than the corresponding yield stress (5.7 MPa) and plateau stress (8.6 MPa) of the pure Al foam. Especially, the energy absorption capacity of the 3.0 wt%-CNT/Al composite foams reaches 19.8 MJ/m 3 at 150 °C, which is ~2.5 times higher than that of pure Al foam. Fracture analysis shows that the failure mode of the Al foam changes from ductile type to brittle type combined with ductile type, as a result of the CNT addition in the matrix. [ABSTRACT FROM AUTHOR]

In this study, a Cu matrix composite is synthesized reinforced by an in-situ three-dimensional graphene network (3D-GN) grown through chemical vapor deposition (CVD). Nano Cu powders and polymethylmethacrylate (PMMA) are employed as matrix and carbon source respectively. PMMA is dispersed on Cu powders after ball-milling. During the CVD process, carbon atoms from pyrolyzed PMMA diffuse and precipitate on Cu powders. By inheriting the morphology of Cu powders, carbon atoms build a 3D-GN in-situ on Cu powders. A bulk 3D graphene/composite with 0.5 wt% graphene is obtained by vacuum hot-press sintering. The favorable interfaces that crucial to the achievement of exceptional mechanical properties of a bulk composite are verified by TEM and SEM characterizations. A yield strength and tensile strength of 290 MPa and 308 MPa respectively are achieved of the composite. The structure of 3D-GN is well preserved in the bulk composite. We demonstrate that the 3D-GN serves as an effective obstacle to the propagation of dislocations by TEM further. [ABSTRACT FROM AUTHOR]

Carbon nanotube (CNT) reinforced Al matrix composites were produced by a modified powder metallurgy route, including in-situ synthesis of CNTs on Al powders by chemical vapor deposition and subsequent ball-milling process. The influence of CNT content (0–4.5 wt%) on the microstructure, mechanical and coefficient of thermal expansion (CTE) performance of CNT/Al composites was systematicly investigated. During the fabrication process, well dispersed CNTs with integrated structure are deeply embedded in Al matrix to form an effective interface bonding. The hardness and tensile strength of CNT/Al composites monotonically increase with the increment of CNT content. The 4.5 wt%-CNT/Al composites exhibit largest hardness and tensile strength, which is 2.3 and 2.4 times higher than that of starting Al, respectively. The CTEs of the composites decrease with the increase of CNT content at the temperature range of 100–300 °C. The CTE of the 4.5 wt%-CNT/Al composites reduces as much as 17% compared with that of starting Al at 100 °C. Thus, we offer a large variety of mechanical and CTE properties which depend on the CNT content in CNT/Al composites, all of them might be good alternatives depending on the application purpose. [ABSTRACT FROM AUTHOR]

A facile and scalable strategy was developed to fabricate SnO 2 -Fe 3 O 4 @C micrometer-sized particles as a good lithium-ion battery anode. The obtained materials were constructed by aggregated nanoclusters (100–200 nm) consisting of SnO 2 -Fe 3 O 4 @C nanospheres (20 ∼ 30 nm), in which SnO 2 and Fe 3 O 4 nanoparticles (5 ∼ 8 nm) were homogeneously embedded in a percolating carbonaceous network with an average thickness of about 3 nm. SnO 2 -Fe 3 O 4 @C microparticles were synthesized by a one-pot hydrothermal process followed by annealing under Ar and subsequent chemical vapor transformation (CVT) under vacuum. The peculiar strategy allows to obtain hierarchical structure of micrometer-sized particles including nanospheres, nanoclusters and micro-scale particles, and the combination of SnO 2 and Fe 3 O 4 could promote the synergistic effects to enhance the reversible capacity as well as the structural stability. Meanwhile, the carbon layer, homogeneously covering the nanoparticles does not only accommodate the volume change of active materials to maintain the structural integrity but also forms a conductive network throughout the whole micro-sized structure during charge/discharge processes. As a result, the electrode of SnO 2 -Fe 3 O 4 @C microparticles exhibits good rate performance (1056 mAh g −1 at 0.1 C, 734 mAh g −1 at 0.2 C, 449 mAh g −1 at 0.5 C, 212 mAh g −1 at 1 C and 133 mAh g −1 at 2 C, 1 C = 1 A g −1 ), high reversible capacity and good cycling stability (a high initial charge capacity of 1131.8 mAh g −1 was achieved and the capacity maintained 853.3 mAh g −1 after 50 cycles at 0.1 A g −1 ). [ABSTRACT FROM AUTHOR]

A mass of carbon nanospheres (CNSs) have been synthesized by chemical vapor deposition of C 2 H 2 directly over Fe-based glassy alloy particles (Fe 76 Si 9 B 10 P 5 ) without the addition of an external catalyst. The morphology and microstructure as well as the growth mechanism of the CNSs have been investigated by using scanning and transmission electron microscopy. The results showed that the obtained products consist of hollow CNSs and CNSs with Fe nanoparticles encapsulated. The CNSs with amorphous walls have high purity (>95%) and uniform size distribution (50–150 nm). The possible formation and growth mechanism of the CNSs were discussed on the basis of the investigation on their initial growth stages. [ABSTRACT FROM AUTHOR]

Abstract: An approach was developed to fabricate carbon nanotube (CNT)-reinforced Al composites. In a typical process, the Co catalyst was evenly deposited on the surface of Al powder by impregnation route, and then the CNTs were grown in the Al powder by chemical vapor deposition to obtain CNT/Al powders. After ball-milling of the obtained powders for a short time, the CNT/Al composites were fabricated by compacting, sintering and hot extrusion of the ball-milled powders. During this process, the well dispersed CNT reinforcement is deeply embedded in the Al powder forming an effective interface bonding with matrix. As a result, the CNT/Al composites containing 2.5wt.% CNTs exhibit the ultimate tensile strength of 334MPa which is 1.7 times higher than that of unreinforced Al, and good ductility of ∼18% elongation to failure. Thus, well-balanced strength and ductility are achieved in CNT-reinforced Al composites. [Copyright &y& Elsevier]

Abstract: In this paper, carbon nanotubes (CNTs) are added in order to investigate their influence on the electronic conductivity of LiFePO4 cathode. CNTs/LiFePO4 composites are prepared by in-situ chemical vapor deposition method and the traditional mechanical mixture method respectively in order to investigate the influence of CNTs as an additive on the electrochemical performance of LiFePO4 cathode. The particle morphology and electrochemical performances of the CNTs/LiFePO4 composites are characterized and compared with commercial cathodes, LiFePO4 mixed with carbon black. The in-situ synthesized CNTs/LiFePO4 composite by chemical vapor deposition method maintains full retaining ratio after 100 cycles at 1C and 94.5% retention after 20 cycles at 10C, which precede the CNTs/LiFePO4 composite fabricated by the mechanical mixture method as well as the commercial cathode. The enhanced electrochemical performance is due to the excellent interface bonding between LiFePO4 and CNT in in-situ synthesized CNTs/LiFePO4 composites. The interface benefits the electronic conductivity of the composites, as well as the polarization reduction. [Copyright &y& Elsevier]

Abstract: In this study, we report an efficient method for synthesis of well-graphitized hollow carbon nano-onions (CNOs). CNOs were firstly fabricated by chemical vapor deposition (CVD) method at 850°C using an Fe–Ni alloy catalyst with diameters of 10–15nm. Then hollow CNOs were obtained by annealing as-prepared CNOs at 1100°C for 3h. It is found that during the CVD growth, the presence of nickel retards the deactivation of Fe–Ni–C austenite, providing the possibility for the growth of up to two hollow CNOs from each alloy particle. The subsequent high-temperature annealing led to the escaping of the Fe–Ni alloy from the graphitic layers, and the re-catalysis of precipitation and graphitization of the carbon atoms previously dissolved in the alloy particle (Fe0.64Ni0.36) to form hollow CNOs. The hollow CNOs exhibit good performance as materials for electrochemical hydrogen storage, with a discharge capacity of 481.6mAh/g under a current density of 500mA/g, corresponding to a hydrogen storage capacity of 1.76wt.%. Our results demonstrate that the hollow CNOs are promising materials as a storage medium for hydrogen as a fuel source. [Copyright &y& Elsevier]

Abstract: It is well known that Fe, Co, Ni, and their alloy are the effective catalyst components in chemical vapor deposition growth of carbon nanotubes (CNTs), while Cu has low catalytic activity owing to its nearly zero carbon solubility. In this paper, a simple and effective approach was developed to synthesize multi-walled CNTs using unmodified Cu catalyst supported on Al matrix under a low temperature (600°C). The obtained CNTs with bamboo-like structure are mainly composed of well-crystallized graphite. It is found that the Al carrier plays a key role in the catalytic growth of CNTs, signifying a new way for low-temperature synthesis of multi-walled CNTs. [Copyright &y& Elsevier]

Abstract: Multi-walled carbon nanotubes (CNTs), which are with the diameter from 15 to 50 nm and length from several microns to several tens of microns, were synthesized over Ni/Al composite catalyst by CVD of methane at the temperature range of 723 K–923 K. The Ni content in the Ni/Al composite catalyst varied from 5 wt.% to 15 wt.%. As the synthesis temperature increased from 723 K to 923 K and the nickel content increased from 5 wt.% to 15 wt.%, the CNT yield increased by about 17 times. The purity of CNTs decreased and the diameter of CNTs increased with the increase of Ni content in the catalyst. The relative amount of crystalline graphite sheets increased progressively with the growth temperature and a higher degree of crystalline perfection could be achieved at 923 K. These results demonstrated that the growth rate, diameter, and crystallinity of CNTs can be controlled by varying the synthesis temperature and catalyst composition. [Copyright &y& Elsevier]