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We report an effective technique for the growth of graphene nanowalls (GNWs) and nitrogen-doped graphene nanowalls (N-GNWs) using a thermal chemical vapor deposition (TCVD) on the catalyst-free substrate. Ethanol and mixed ethanol-imidazole were used as carbon and carbon-nitrogen sources for the growth of GNWs and N-GNWs, respectively. The effect of imidazole concentration on the morphology, nanostructure, crystal structure, crystallinity, chemical bonding and chemical structure of GNWs and N-GNWs were investigated by scanning electron microscopy, transmission electron microscopy (TEM), X-ray diffraction, Raman spectroscopy and X-ray photoelectron spectroscopy. Focused ion beam combined with TEM was utilized to analyze the growth mechanism. The results show that GNWs and N-GNWs are vertically oriented graphene nanosheets on in-plane-oriented graphitic layer/carbon nanolayer. An increase in imidazole concentration from 2.5 to 5.0 wt% increases the nitrogen content in the N-GNWs from 1.24 to 2.61 at%. The incorporated nitrogen atoms are mainly graphitic-N. One-step facile growth of N-GNWs by TCVD method without the need for a metal catalyst and plasma system was achieved. [ABSTRACT FROM AUTHOR]

ZnO nanostructures, semiconductors with attractive optical properties, are typically grown by thermal chemical vapor deposition for optimal growth control. Their growth is well investigated, but commonly results in the entire substrate being covered with identical ZnO nanostructures. At best a limited, binary growth control is achieved with masks or lithographic processes. We demonstrate nanosecond laser-induced Au catalyst generation on Si(100) wafers, resulting in controlled ZnO nanostructure growth. Scanning electron and atomic force microscopy measurements reveal the laser pulse's influence on the substrate's and catalyst's properties, e.g., nanoparticle size and distribution. The laser-induced formation of a thin SiO2-layer on the catalysts plays a key role in the subsequent ZnO growth mechanism. By tuning the irradiation parameters, the width, density, and morphology of ZnO nanostructures, i.e., nanorods, nanowires, and nanobelts, were controlled. Our method allows for maskless ZnO nanostructure designs locally controlled on Si-wafers. [ABSTRACT FROM AUTHOR]

Although zinc chloride (ZnCl2) has been a well-known efficient activate agent for char, there are few precedents that biochar can efficiently remove nitrate ions with a high adsorptive capacity from aqueous solution. In this study, an efficient biomass (bamboo) activated carbon was developed by ZnCl2 activation. Lignin removed Moso bamboo was activated by 3 times mass ratio of ZnCl2, followed by 500 ℃ pyrolysis for 1 h, named BZ3. For improving the adsorption capacity of BZ3 for nitrate ions, thermal chemical vapor deposition (CVD) was used to treat BZ3 for optimizing the surface structure. Among the tested procedures, the sample treated by the order of an acetonitrile vapor doping nitrogen at 800 ℃, then 950 ℃ heating for 30 min followed by steam treatment at 800 ℃ was proven the most high-spec sample. The obtained activated biochar was proven as BZ3-8AN20-9.5HT30-8ST30. It showed the maximum nitrate adsorption capacity of 0.57 mmol/g in nitrate concentration of 200 mg/L at solution pH 3 with the surface area 900 m2/g, tested by Brunauer–Emmett–Teller method. In the weak acidic to weak alkali solution pH range 6–8, the adsorption capacity of 0.28 mmol/g on BZ3-8AN20-9.5HT30-8ST30 was higher than that of BZ3-8AN20-8ST30. For the kinetic test, BZ3-8AN20-9.5HT30-8ST30 could fit to both pseudo-first-order (R2 = 0.957) and pseudo-second-order well (R2 = 0.993). Article Highlights: The strong anionic adsorptive site quaternary nitrogen (N-Q) was successfully doped on carbonaceous bamboo biochar BZ3 (SBET = 1580 m2/g, Vtotal = 0.94 cm3/g) by thermal chemical vapor deposition (CVD) method. The maximum nitrate ions adsorption capacity was 0.60 mmol/g for BZ3-8AN20-8ST30 and 0.57 mmol/g for BZ3-8AN20-9.5HT30-8ST30 at solution pH 3. Injection of N-Q sites achieves the higher adsorption capacities of bamboo biochar over a wider range of solution pH. Both weight percentage of N-Q and the weight percentage ratio of oxygen and hydrogen (O/H) showed credible positive linear correlation with nitrate ions adsorption capacities of BZ3 series samples. The kinetic adsorption process of surfaced modified sample BZ3-8AN20-9.5HT30-8ST30 could fit to both pseudo-first-order model (R2 = 0.957) and pseudo-second-order model (R2 = 0.993) well. [ABSTRACT FROM AUTHOR]

ZnO nanostructures, semiconductors with attractive optical properties, are typically grown by thermal chemical vapor deposition for optimal growth control. Their growth is well investigated, but commonly results in the entire substrate being covered with identical ZnO nanostructures. At best a limited, binary growth control is achieved with masks or lithographic processes. We demonstrate nanosecond laser-induced Au catalyst generation on Si(100) wafers, resulting in controlled ZnO nanostructure growth. Scanning electron and atomic force microscopy measurements reveal the laser pulse’s influence on the substrate’s and catalyst’s properties, e.g., nanoparticle size and distribution. The laser-induced formation of a thin SiO2-layer on the catalysts plays a key role in the subsequent ZnO growth mechanism. By tuning the irradiation parameters, the width, density, and morphology of ZnO nanostructures, i.e., nanorods, nanowires, and nanobelts, were controlled. Our method allows for maskless ZnO nanostructure designs locally controlled on Si-wafers.

Carbon spheres (CNSs) and carbon nanotubes (CNTs) are attracting more attention from researchers due to their excellent potential applications as adsorbents, catalyst carriers, and drug delivery. The synthesizing of CNTs and CNSs is a challenging and tedious process. A researcher has to produce different catalyst materials and precursors to synthesize CNTs and CNSs. Hence, an attempt has been made to combined in-situ synthesize of CNSs and CNTs in a single experiment. NiO/CuO/Al2O3 catalyst was used as a substrate. The thermal chemical vapor deposition (CVD) process with acetylene as a precursor gas was used to synthesize the CNSs and CNTs. The influence of process parameters and the growth mechanism of carbon nanomaterials were investigated. The obtained carbon nanomaterials samples were characterized using FESEM, HRTEM with SAED pattern, XRD analysis, Raman spectroscopy, and FTIR analysis. Results indicated that the catalyst morphology has a greater influence on the growth of CNTs and CNSs. The CVD process parameters play a vital role in deciding the structure of carbon nanomaterials. A schematic representation was proposed to understand the formation of carbon nanomaterials on top of the catalyst particles.

Hexagonal boron nitride nanosheets (BNNSs) demonstrated potential applications for ultraviolet (UV) nanoelectronics, catalytic support, electron field emission, and many other areas. However, their extensive industrial application is limited by the complicated conventional procedures for scalable preparations. In this study, vertically aligned BNNSs were directly synthesized without any substrates using Fe-catalyzed thermal chemical vapor deposition (CVD) method under a NH 3 gas flow at 1200 °C via the catalytic pyrolysis of the inorganic hybrid precursor. BNNSs grew via an Oswald ripening process assisted by oriented attachment mechanism under Fe catalyzed by analyzing the evolution process. Most nanosheets are <10 nm thick, and the number of constituent layers is typically between 10 and 20 nm. BNNSs improved crystallinity, had high UV light emission, and had excellent anti-oxidation behavior because of their unique structures. The development of a simple, high yield and environmentally friendly synthesis method for BNNSs allows for the exploration of industrial upscaling applications. • Vertically aligned BNNSs deposited by a catalytic-thermal CVD route without substrates. • The inorganic precursor was prepared by a sample wet chemical synthesis methods. • BNNSs exhibited enhanced crystallinity and UV light emission as well as remarkable oxidation resistance. • BNNSs grow via an Oswald ripening process assisted by the oriented attachment mechanism. [ABSTRACT FROM AUTHOR]

In this work, sulfur-doped (S-doped) TiO2 with the (001) face exposed was synthesized by thermal chemical vapor deposition at 180 or 250 °C using S/Ti molar ratios RS/Ti of 0, 0.5, 1, 2, 3, 4 and 5. The S-doped samples synthesized at 250 °C exhibit a significantly improved photocatalytic performance. More precisely, S-doping has the following effects on the material: (1) S can adopt different chemical states in the samples. Specifically, it exists in the form of S2− replacing O2− at a ratio of RS/Ti = 1 and also in the form of S6+ replacing Ti4+ at RS/Ti ≥ 2. As a result, S-doping causes a lattice distortion, because the ionic radii of S2− and S6+ differ from that of the O2− and Ti4+ ions. (2) S-doping increases the adsorption coefficient Ae for methylene blue (MB) from 0.9% to 68.5% due to the synergistic effects of the oxygen vacancies, increased number of surface chemical adsorption centers as a result of SO42− adsorption on the TiO2 surface and the larger pore size. (3) S-doping increases the MB degradation rate from 6.9 × 10−2 min−1 to 18.2 × 10−2 min−1 due to an increase in the amount of •OH and •O2− radicals.

Multi‐walled carbon nanotubes (CNTs) are deposited via thermal chemical vapor deposition using cobalt catalyst and MgO promoter. A systematic investigation of the major processing parameters such as temperature (390–620 °C), pressure (3–10 mbar), injection (4–10 ms), and deposition times is performed. The impact of these parameters on the film density and optical properties of CNT coatings is discussed. Irrespective of the growth parameters, a homogeneous deposition of CNTs and a negligible impact on the CNTs' quality are observed. Total hemispherical reflectance (THR) reveals a threshold thickness of 3 μm, above which the CNT films behave as an efficient black absorber in the UV–vis–near‐infrared (NIR) and mid‐infrared (MIR) spectral regions. Spatial and spectral integrations of THR show a reflection below 1% in the 250 nm–2.5 μm spectral range. The low reflection observed in the NIR is retained in the MIR up to λ = 10 μm. [ABSTRACT FROM AUTHOR]

In this report, we propose an easy and viable fabrication method for growing multilayer graphene (MLG)-encapsulated nickel nanoparticles (Ni NPs) via a one-step continuous aerosol process comprising combined spray pyrolysis (SP) and thermal chemical vapor deposition (CVD). A bimodal size distribution was observed for the Ni NPs owing to droplet-to-particle and gas-to-particle conversions undergone in the SP at ~1000 °C. The number of graphene layers grown on the surface of Ni NPs in the thermal CVD was controlled by varying the reaction temperature of 300–700 °C, which perturbed the solubility and diffusion rates of carbon in Ni NPs. Finally, we demonstrated that the MLG-encapsulated Ni NP-added nanoenergetic materials were stably ignited by flash irradiation in a short ignition delay time (~267 μs) with fast burn rate (~200 m·s−1). This suggests that the MLG-encapsulated Ni NPs could play an important role as potential optical igniters for practical thermal engineering applications. Unlabelled Image • Multilayer graphene (MLG) is grown on the surface of Ni nanoparticles (NPs) in the gas phase. • The number of graphene layer is controlled by varying the reaction temperature. • MLG-encapsulated Ni NPs are ignited by flash irradiation due to photothermal effect. [ABSTRACT FROM AUTHOR]

Under a one-step process, catalyst-free growth of one-dimensional (1D) ZnO hierarchical nanostructures was performed on ZnO-seeded Si substrate by thermal chemical vapor deposition with a perpendicular setup. The morphological and crystallographic properties of the nano/micro-structured ZnO rods were investigated with varying growth temperature and growth time. X-ray diffraction patterns of 1D ZnO double-structured rods showed the hexagonal wurtzite structure. The morphology and crystal structure of the ZnO double-structured rods were sensitive to the growth temperature and growth time. From Raman scattering and photoluminescence spectra, the orientation and size effects of the ZnO double-structured rods were discussed in relation to growth temperatures and growth times.

Highlights • CNC-CMC hybrids were formed by modulating CS 2 injection flow in on/off cycles. • CNC-CMC hybrids gave rise to the stabilized-higher electrical conductivities. • Shielding effectiveness of the CNC-CMC@PU composite was enhanced. Graphical abstract Abstract Carbon nanocoil-carbon microcoil (CNC-CMC) hybrid materials were prepared via the formation of numerous carbon nanocoils (CNCs) on the surface of carbon microcoils (CMCs), using C 2 H 2 as the source gas and CS 2 as the additive gas in a thermal chemical vapor deposition system. During the reaction, CS 2 was injected into the reactor in modulated on/off cycles. The density of CNCs formed on the surface of CMCs increased with an increase in the number of on/off cycle numbers. In the as-grown state, the CNC-CMC hybrid materials showed higher electrical conductivity than that of the materials composed only of CMCs. Composites of CNC-CMC hybrid materials in polyurethane (CNC-CMC@PU) and CMCs in polyurethane (CMC@PU) were fabricated. The CNC-CMC@PU composites showed higher shielding effectiveness than the CMC@PU composites, irrespective of the mixing ratios of carbon nanomaterials in PU. Based on the shielding effectiveness and electrical conductivity, we conclude that the formation of CNC-CMC hybrid materials can enhance shielding effectiveness through a reflection-based mechanism as well as an absorption-based mechanism. [ABSTRACT FROM AUTHOR]

We report on the performance of self-powered ultraviolet (UV) photodetectors composed of SnO 2 nanowire (NW) networks. SnO 2 NWs with a length of several hundred micrometers can be synthesized by thermal chemical vapor deposition (CVD) using SnO powder as the raw material, which has the advantages of a low process temperature and no requirement for a reducing agent. Based on the characterization results obtained through synchrotron X-ray diffraction (XRD), scanning electron microscopy, and transmission electron microscopy (TEM), we determined the growth behavior of SnO 2 NWs via a vapor-liquid-solid mechanism with Au nanoparticles. The NW growth switched from an initial in-plane growth to subsequent vertical growth, forming NW cotton. This was started at a process temperature of 600 ℃ and optimized at 800 ℃. Moreover, the XRD and TEM results indicate that the NWs mainly grew in the form of SnO 2 , although the formation of SnO NWs was also possible. Metal−SnO 2 NW−metal type photodetectors were fabricated, and their photoresponsivity to UV light in the range from 200 to 400 nm was investigated. The device exhibited a photo-to-dark current ratio of ∼2.17 × 106 at an applied bias of 10 V and 254 nm UV exposure. A maximum responsivity of about 1100 A/W was estimated at a wavelength of 270 nm, and the cutoff edge wavelength appeared around 350 nm. In particular, the self-powered photoresponse at nominal zero bias was ∼1.23 nA. The results of this study support the idea that SnO 2 NWs are promising candidates for self-powered deep-UV photodetectors and that thermal CVD using SnO powder is suitable for synthesizing SnO 2 NWs at temperatures as low as 700 °C. [Display omitted] • The use of SnO powder instead of SnO 2 in thermal CVD was effective for synthesizing SnO 2 nanowires without reducing agents. • The nanowire growth switched from an initial in-plane growth to subsequent vertical growth, forming nanowire cotton. • The ultraviolet photodetector showed PDCR > 2.17 × 106, R of ∼660 A/W, and D* of ∼1.12 × 1016 Jones at a bias of 10 V. • The self-powered photoresponse at nominal zero bias was ∼1.23 nA. [ABSTRACT FROM AUTHOR]

The article presents the results of experiments on the synthesis of carbon nanofibers by thermal chemical vapor deposition using copper nanopowders obtained by electric explosion of wire as catalysts. Stable growth of carbon nanofibers was carried out at temperatures significantly lower than normally used. The process parameters that are optimal for low-temperature growth of carbon nanofibers have been identified during the performed experiments. The synthesized samples have different diameters and morphology (from spiral to direct). Copper clusters are both at the ends and inside the fibers. The results of IR spectroscopy indicate that the structure of the obtained carbon nanofibers is polymeric. X-ray analysis revealed the presence of a halo on the diffraction patterns at small values of the angle 2θ, which proves that the grown structures have an amorphous nature. There are no groups that are responsible for long-range order in all Raman spectra. Studies by transmission electron microscopy showed that nanostructures do not have an internal channel and nanofibers are solid.

Abstract In this study, thin films containing mono and few-layer MoS 2 were directly synthesized by one-step thermal chemical vapor deposition on Si/SiO 2 substrate. The effects of precursors' ratios including sulfur and MoO 3 powders were systematically studied by altering sulfur content for the growth of MoS 2 nanoflakes. The X-Ray diffraction patterns and scanning electron microscopy confirmed the formation of MoS 2 nanoflakes in sulfur contents of 500 and 1000 mg. According to the line width and frequency difference between the E1 2g and A 1g in Raman spectroscopy, the nanoflakes grown with sulfur content of 500 and 1000 mg were two-dimensional MoS 2 structures having few numbers of layers. Moreover, it was verified by assessment of the nanoflakes' band gap via UV–visible and photoluminescence analysis. In addition, the open-aperture and close-aperture Z -scan techniques were employed to study the nonlinear optical properties including nonlinear absorption and nonlinear refraction of the synthesized nanoflake in sulfur content of 500 mg. The experiments were performed using a diode laser with a wavelength of 532 nm as light source at different powers. The nanoflakes displayed considerable saturable absorption (SA) under low laser power and reverse saturable absorption (RSA) at higher laser powers. In general, few-layered MoS 2 would be useful for the development of nanophotonic devices like optical limiters, optical switchers, etc. [ABSTRACT FROM AUTHOR]

The integration of electronic elements with conventional textiles is essential for the fabrication of intelligent clothes. Carbon nanotubes (CNTs) owing to their light weight, high surface area, excellent electric and mechanical properties, have recently been applied as the electronic element to make wearable electronic textiles by a dip-drying process. In this research, Carbon nano tubes were in situ synthesized on glass fiber mat using chemical vapor Deposition method. The electrical conductivity properties on glass mat coated with carbon nanotubes (CNT) were investigated. Process time and temperature was considered as variable parameters to achieve optimal conditions for CNT deposition on glass mat. In this research, acetylene gas was used as the hydrocarbon source. Also Argon was used as a carrier gas. Scanning Electron Microscopy (SEM), Transmission Electron Microscopy (TEM) and Raman Spectroscopy were used for investigating the morphology and quality of produced CNTs. Electrical conductivity was observed and compared on both untreated and coated glass mat. The optimum time and temperature for the production of nanotubes on glass mat was studied. [ABSTRACT FROM AUTHOR]

We fabricated tin oxide nanowires (NWs) on Au/Si 3 N 4 /Si(001) substrates using thermal chemical vapor deposition (CVD) in a hydrogen reduction atmosphere. Unlike typical thermal CVD conditions, a mixture of H 2 and Ar gas was used as the carrier gas, and a catalyst powder such as graphite was not used. The hydrogen gas maintained the reducing atmosphere and easily vaporized the SnO 2 powder without a catalyst, to supply vapors of Sn and O. This process enables vapor-liquid-solid (VLS) growth of SnO 2 NWs at temperatures below 600 °C. The formation of a eutectic AuSn alloy that acts as a liquid seed during the VLS process contributes to lowering the growth temperature. X-ray diffraction and transmission electron microscopy analysis show that SnO 2 NWs and SnO NWs coexist in the as-prepared sample. The oxygen-deficient atmosphere results in nucleation and growth of SnO NWs. [ABSTRACT FROM AUTHOR]

The main aim of this research work is in situ synthesis of carbon nano tube (CNT) on nonwoven glass mat. Different types of catalyst were used and the effect of them on growth of carbon nanotubes on glass mat was investigated. The process was considered as variable catalysts to achieve optimal conditions for CNT deposition on glass mat. In this research, iron, cobalt, copper and nickel were used as catalysts and acetylene gas was used as the hydrocarbon source. Also, argon was used as a carrier gas. In first step, samples were coated by mentioned catalyst using plasma sputtering method. The thickness of the catalyst on the surface of samples was fixed at 100 nm. In second part, thermal chemical vapor deposition (TCVD) system was used for growth of carbon nano tubes. Scanning electron microscopy (SEM) and raman spectroscopy, thermogravimetric analysis (TGA-DTG) and transmission electron microscopy (TEM) were used for investigating the morphology and quality of produced CNT. Electrical conductivity was observed and compared on both untreated and coated glass mat. The results show that, by pre sputtering of samples with nickel, the quality of CNT on the surface of glass mat will be improved and the resistivity of samples reach to 610 Ω. [ABSTRACT FROM AUTHOR]

The work reports the traces of graphene synthesized by Thermal-CVD technique over oxidized silicon substrates coated with nickel and cobalt catalysts under different pressures. Other process parameters like temperature, gas composition and time are kept constant during the growth. Effect of pressure on the nature of defects and structure of the graphene has been analyzed by Raman spectra. Effect of pressure on morphology has also been studied. It has been observed that the variation of pressure is responsible for any change in the structure and morphology of the graphene for a given catalyst. Formation of graphene and its defects has been explained with the help of two-step diffusion process. [ABSTRACT FROM AUTHOR]

In this research, ZnO nanostructure hexagonal pyramid rods with high optical and structural quality were synthesized by the simple thermal chemical vapor deposition of Zn powder without a metal catalyst. Surface morphologies were characterized by scanning electron microscopy (SEM). XRD analyses demonstrated that ZnO hexagonal pyramid rods had a wurtzite structure with the orientation of (002). Investigation of optical properties of samples by photoluminescence spectrum exhibited a sharp UV emission peak at 380nm. The quality and composition of the ZnO pyramid rods were characterized using the Fourier transform infrared spectrum (FTIR) at room temperature. In addition, the growth mechanism of ZnO hexagonal rods is also briefly discussed.

The mechanism of the one-order-of-magnitude increase in the density of vertically aligned carbon nanotubes (CNTs) achieved by a recently developed thermal chemical vapor deposition process was studied using synchrotron radiation spectroscopic techniques. In the developed process, a Ti film is used as the underlayer for an Fe catalyst film. A characteristic point of this process is that C2H2 feeding for the catalyst starts at a low temperature of 450°C, whereas conventional feeding temperatures are ∼800°C. Photoemission spectroscopy using soft and hard X-rays revealed that the Ti underlayer reduced the initially oxidized Fe layer at 450°C. A photoemission intensity analysis also suggested that the oxidized Ti layer at 450°C behaved as a support for nanoparticle formation of the reduced Fe, which is required for dense CNT growth. In fact, a CNT growth experiment, where the catalyst chemical state was monitored in situ by X-ray absorption spectroscopy, showed that the reduced Fe yielded a CNT forest at 450°C. Contrarily, an Fe layer without the Ti underlayer did not yield such a CNT forest at 450°C. Photoemission electron microscopy showed that catalyst annealing at the conventional feeding temperature of 800°C caused excess catalyst agglomeration, which should lead to sparse CNTs. In conclusion, in the developed growth process, the low-temperature catalyst activation by the Ti underlayer before the excess Fe agglomeration realised the CNT densification.

This work reports the growth of magnesium oxide (MgO) nanocubes by thermal chemical vapor deposition at various temperatures. The MgO nanocubes were investigated by X-ray diffraction, FESEM, EDAX, TEM and FTIR studies to study its various properties. The material is well-dispersed and has a cubical shape with an average size of 16 nm. XRD shows a face cubic centered structure, and SEM and TEM reveal nanocube morphology. The mechanism of the growth process is briefly detailed. The MgO nanocubes, if deposited on an overhead projector sheet, can be used as a chemoresistive sensor for hydrogen at a constant temperature of typically 200 °C and an applied voltage of 5 V. The sensor can detect hydrogen in the 3000 to 5000 ppm concentration range, and the lowest detectable concentration (at a signal-to-noise ratio of 3) is 3000 ppm. [ABSTRACT FROM AUTHOR]

The synthesis of carbon-nanocoil–carbon-microcoil (CNC–CMC) hybrid materials, namely carbon nanocoils (CNCs) formed together with the growth of the carbon microcoils (CMCs), were achieved using C 2 H 2 as the source gas and SF 6 as an additive gas in a thermal chemical vapor deposition system. During the reaction, SF 6 was injected into the reactor in modulated on/off cycles. The CNC–CMC hybrid materials were not observed without the on/off cycles of SF 6 flow. When we varied the number of the on/off cycles, the density of CNCs formed in the CNC–CMC hybrid materials increased with increasing cycle number. The cause for the difference in CNC–CMC formation with cycle number was investigated. Based on the results, a growth mode of the CNC–CMC hybrid materials was proposed. [ABSTRACT FROM AUTHOR]

In this research, we investigated the effect of structure and morphology of carbon nanotubes (CNTs) on nitrogendioxide (NO2) gas sensing. CNTs were synthesized by thermal chemical vapor deposition (TCVD) at different synthesistemperatures. The structure and morphology of CNTs were investigated by various characterization tools such as scanningelectron microscopy (SEM), transmission electron microscopy (TEM) and Raman spectroscopy. The resistance changes ofCNTs were obtained upon NO2 gas exposure with concentrations of 600, 1,800 and 3,000 ppm at room temperature. Ourresults show that the CNTs prepared at 950°C showed the highest response. We suggest that the response of CNTs to NO2gas depends more strongly on the interstitial area and electronic structure than on the defects of CNTs. These results are ingood agreement with the theoretical calculations on adsorption sites (surface, pore, groove and interstitial) and electronicstructure (metallic or semiconducting) reported by previous studies.

Carbon nanofibers (CNFs) decorated with Cu2O particles were grown on a Ni catalyst layer deposited on a Cu substrate by thermal. chemical vapor deposition from liquid petroleum gas. Ni catalyst nanoparticles with different sizes were produced in an electroplating system at 35˚C. These nanoparticles provide the nucleation sites for CNF growth, removing the need for a buffer layer. High temperature surface segregation of the Cu substrate into the Ni catalyst layer and its exposition to O2 at atmospheric environment, during the CNFs growth, lead to the production of CNFs decorated with Cu2O particles. The surface morphology of the Ni catalyst films and grown CNFs over it was studied by scanning electron microscopy. Transmission electron microscopy and Raman spectroscopy revealed the formation of CNFs. The selected area electron diffraction pattern and electron diffraction studies show that these CNFs were decorated with Cu2O nanoparticles.

Multi-walled carbon nanotube arrays (MWCNTAs) were grown by thermal chemical vapor deposition (TCVD) in a horizontal furnace reactor. The scanning electron microscopy (SEM) results show that MWCNTAs grown on the bottom and the central of the quartz tube are different in one experiment. Moreover, the MWCNTAs grown on the central position are more aligned and longer than those on the bottom. A computational fluid dynamics (CFD) model was employed to investigate the gas flow field impact on the MWCNTAs growth. The results show that gas circulations appear after carrier gas and carbon source are injected into the quartz tube. Because of the existence of gas circulations, the gas flow field at the central of the quartz tube is more stable, which is conducive to the growth of MWCNTAs. The CFD simulation results match well with the experimental data. [ABSTRACT FROM AUTHOR]

Nitrogen-doped carbon nanotubes (N-doped CNTs) were grown on Fe-coated Si substrates through thermal chemical vapor deposition using C 2 H 2 , H 2 , Ar, and NH 3 gases. The effects of the flow rate of NH 3 gas during the growth of N-doped CNTs were investigated. As the proportion of NH 3 gas was increased from 0 to 30%, the growth rate exponentially decreased from 50 nm/s to 5 nm/s, while the diameter (10–17 nm) and wall numbers (∼7 layers) of the N-doped CNTs seldom changed. However, with the increased proportion of NH 3, the nitrogen concentration in N-doped CNTs gradually increased. From XPS and Raman results, we observed that pyrrolic and pyridine bonding was dominant at low proportions of NH 3 , causing an increase in the number of defects and disorders in the CNTs. However, the quaternary bonding appeared at the NH 3 proportions of 30%, while the concentration of pyrrolic and pyridine bonding saturated. Consequently, N-corporation inside the carbon honeycomb structure occurred above a specific proportion of NH 3. This indicates that a high proportion of NH 3 during the CNT growth is necessary to acquire the quaternary bonding between CNTs and nitrogen. [ABSTRACT FROM AUTHOR]

Carbon nanocoils (CNCs) were deposited on Al 2 O 3 substrates using C 2 H 2 and H 2 as source gases in a thermal chemical vapor deposition system. Composites of CNCs in polyurethane (CNC@PU) and CNCs plus other carbon-based materials, such as carbon microcoils (CMCs) and carbon nanotubes (CNTs), in polyurethane (CNC + CMC@PU, CNC + CNT@PU) was fabricated. The electromagnetic-wave-shielding effectiveness of the CNCs-incorporated composites were examined and compared with those of other carbon-based materials in the measurement-frequency range of 0.25–4.0 GHz. The incorporation of CNCs in CMC@PU composites reduced the shielding effectiveness; on the other hand, it slightly enhanced the shielding effectiveness of CNT@PU composites within the measurement frequency range of 0.5–3.0 GHz. Based on the resulting shielding effectiveness, we conclude that the incorporation of CNCs was useful for the materials that exhibited reflection-based shielding effectiveness although the CNCs themselves had poor electrical conductivity. [ABSTRACT FROM AUTHOR]