Synthesis of ordered ZnS nanotubes by MOCVD-template method

Semiconductor ZnS nanotubes arrays were synthesized in the pores of the porous anodic alumina (PAA) membranes by using metal organic chemical vapor deposition (MOCVD) template methods. The morphology and structure of the ZnS nanotubes were characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), selected-area electron diffraction (SAED) and X-ray diffraction (XRD). It is found that the ZnS nanotubes with diameters in range of 140–250 nm and the length up to tens of microns are polycrystalline. Energy-dispersion spectroscopy (EDS) and X-ray photoelectron spectroscopy analysis (XPS) indicate that the stoichiometric ZnS was formed. A green-blue emission band centered at 510 nm was observed in the photoluminescence spectrum of the ZnS nanotubes.     

High-aligned carbon nanotube film with netlike bulges

High-aligned carbon nanotubes film with netlike bulges made of catalyst particles has been synthesized on a silica wafer by pyrolyzing ferrocene/melamine mixtures. The structure and composition of carbon nanotubes are investigated by scanning electron microscopy, transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS) and electron energy-loss spectroscopy (EELS). It is found that these nanotubes have uniform outer diameters of about 25 nm and lengths of about 40 μm. High-resolution TEM images show that each carbon nanotube is composed of graphite-like layers arranged in a stacked-cup-like structure. XPS spectrum shows that the crust covering the tops of the aligned carbon nanotube film consists of carbon, iron and ferric oxide. The EELS spectrum shows that these nanotubes are pure-carbon tubes. The formation mechanism of the netlike bulges has been provided.     

Poly(anthranilic acid)/multi-walled carbon nanotube composites: spectral, morphological, and electrical properties

In this research article, we have described the synthesis of acid (HCl)-doped poly(anthranilic acid) (PAA) with carboxylic groups containing multi-walled carbon nanotubes (c-MWNTs) via in situ polymerization. Anthranilic acid monomers were adsorbed on the surface of MWNTs and polymerized to form PAA/c-MWNT composites. The structure of PAA/c-MWNT composites was characterized by UV–vis spectra, Fourier transform infrared spectroscopy, nuclear magnetic resonance, and X-ray diffraction patterns. Scanning electron microscopy and transmission electron microscopy images showed that both the thinner fibrous phase and the larger block phase could be observed. The individual fibrous phases had diameters of about 100 nm, and therefore, must be the carbon nanotubes (diameter 10–20 nm) coated by a PAA layer. The electrical conductivities of PAA/c-MWNT increased with the increase of c-MWNT content.     

Facile synthesis and characterization of novel nanocomposites of titanate nanotubes and rutile nanocrystals

The nanocomposites of one-dimensional (1D) titanate nanotubes and 0D rutile nanocrystals were fabricated by hydrothermal treatment of bulky rutile TiO₂ powders in a 10 M NaOH solution without using any templates and catalysts. The as-prepared samples were characterized with transmission electron microscopy (TEM), high-resolution transmission electron microscopy (HRTEM), X-ray diffraction (XRD), Brunauer–Emmett–Teller (BET) surface area, Fourier transform infrared spectroscopy (FTIR), UV–visible spectrophotometry (UV–vis), Raman spectroscopy and X-ray photoelectron spectroscopy (XPS). It was found that many small rutile nanocrystal particles of about 5 nm could uniformly attach to the outer surface and in the inner of the titanate nanotubes, forming an interesting and novel nanocomposite structure. Adjusting reaction time could control the amount of rutile nanoparticles in the nanocomposites. With increasing reaction time, the specific surface areas, porosity, pore volume, UV absorption and band gap energies of the nanocomposites gradually increased due to the fact that rutile particles were steadily turned into the tubular nanocomposites, finally completely formed titanate nanotubes.     

Direct synthesis of Y-junction carbon nanotubes by microwave-assisted pyrolysis of methane

Both Y-junction carbon nanotubes and individual carbon nanotubes were synthesized without any additive catalyst by microwave decomposition of methane. Detailed microstructures of as-synthesized products have been characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), and Raman spectroscopy. The results show that these Y-junction CNTs possess an internal bamboo-shaped structure, and some three dimensional multi-terminal junctions are also observed on CNTs. As gas flow rate decreased to 15 sccm, only individual nanotubes could be obtained. A possible mechanism is proposed for the synthesis of the Y-junction carbon nanotubes on these observations. This technique may also have great potential in making other nano-structured carbon materials on a large scale and at low cost.     

Covalent functionalization of single-walled carbon nanotubes with anthracene by green chemical approach and their temperature dependent magnetic and electrical conductivity studies

Single-walled carbon nanotubes (SWCNTs) were covalently functionalized with anthracene in molten urea by a green chemical approach. The anthracene functionalized single-walled carbon nanotubes (Ant-f-SWCNTs) were examined along with SWCNTs, using Fourier transform infrared spectroscopy (FTIR), Raman spectroscopy, powder X-Ray diffraction (XRD), and scanning, and transmission electron microscopy. The observations revealed the functionalization of SWCNTs by anthracene. The temperature dependent magnetization (300–5 K) and electrical resistivity were also measured for both SWCNTs and Ant-f-SWCNTs. The electrical resistivity of Ant-f-SWCNTs at 300 K was found to be 1.27 KΩm, which is much lower than 388.55 KΩm for pristine. This indicated a 300 fold increase in conductivity at room temperature for Ant-f-SWCNTs when compared to SWCNTs. The temperature dependence of the conductivity provided an indication of the semiconducting behaviour.     

An attempt to prepare carbon nanotubes by carbonizing polyphosphazene nanotubes with high carbon content

Polyphosphazene nanotubes with about 20 nm in inner diameter and 100-200 nm in outer diameter were fabricated easily and then carbonized at 800 °C in a nitrogen atmosphere. Scanning electron microscopy and transmission electron microscope results showed that the bulk morphology of polyphosphazene nanotubes was retained after carbonization. The carbon content of the carbonized samples reached 93.28%. X-ray diffraction and Raman spectrum showed that the carbonized samples had low graphitization state. The present method can be used for a mass production of carbon nanotubes.     

Large-scale synthesis of BN nanotubes using carbon nanotubes as template

Boron nitride nanotubes (BN-NTs) were synthesized in large scale by the reaction of NaBH₄ and NH₄Cl in the temperature range of 500-600 °C for 10-18 h, where carbon nanotubes (CNTs) were mixed together with the reactants to serve as template. Pure BN-NTs were obtained by oxidizing the product at about 800 °C in air atmosphere. The structure and morphology of the product with a surface area of 106.635 m²/g were characterized by X-ray diffraction, transmission electron microscopy, Fourier transformation infrared spectroscopy, and thermogravimetric analysis. Large scale preparation of BN-NTs could be realized by this simple and effective route.     

In situ fabrication of carbon nanotube–MgAl2O4 nanocomposite powders through hydrogen-free CCVD

Carbon nanotube–MgAl₂O₄ composite powders were successfully prepared through solution combustion synthesis (SCS) followed by catalytic chemical vapor deposition (CCVD) of methane. Catalyst powders were synthesized starting with the stoichiometric ratios of metal nitrates and urea with a small amount of water and different Fe contents followed by subjecting the solution to heat. The obtained powders were placed in a silica tube to react with methane and form carbon nanotubes. It is noteworthy that no hydrogen was used throughout the whole process. Catalysts and composite powders were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and Raman spectroscopy. The quality of products were evaluated by I_D/I_G ratio obtained from G and D bands intensities in Raman spectra of samples having 10 and 15 wt.% iron. The final product mostly comprised a mixture of single- and double-walled nanotubes on the catalyst containing 10 wt.% Fe, while no carbon product was formed on the catalyst with 5 wt.% Fe.     

Visible light photocatalytic properties of novel molybdenum treated carbon nanotube/titania composites

Two types of molybdenum–carbon nanotubes and molybdenum treated carbon nanotubes/titania composites were prepared using a sol–gel method. These composites were characterized comprehensively by the Brauer–Emett–Teller (BET) surface area, scanning electron microscopy (SEM), energy dispersive X-ray (EDX) analysis, X-ray diffraction (XRD), transmission electron microscopy (TEM) and UV-vis absorption spectroscopy. It was found that the photocatalytic degradation of a methylene blue solution could be attributed to the combined effects caused by the photo-degradation of titania, the electron assistance of carbon nanotube network, and the enhancement of molybdenum. The proposed redox mechanism of the photodegradation of methylene blue on Mo-CNT/TiO₂ composites is suggested.     

Carbon-nanotube-supported Ag and Cu2O nanoparticles: Dendrimer-mediated synthesis and their broadband optical limiting properties

Multiwalled carbon nanotubes (MWCNTs) were covalently functionalized with fourth-generation poly(amido amine) (PAMAM) dendrimers with a trimesyl core (DT4), and the as-synthesized MWCNT-DT4 was used as the template for in situ growth of Ag and Cu₂O nanoparticles on MWCNTs. Extensive characterizations of the resultant hybrids have been performed using X-ray diffraction, transmission electron microscopy (TEM), high resolution TEM, energy dispersive X-ray spectroscopy, selected area electron diffraction, thermal gravimetric analysis, and X-ray photoelectron spectroscopy. The side-wall of the nanotubes was uniformly coated with the nanoparticles with mean sizes of 7–8 nm. The optical limiting property measurements of the nanoparticle-modified MWCNTs were carried out by the open-aperture z-scan technique. The results demonstrate that the samples suspended in water show broadband OL performance, and their OL behavior is better than that of MWCNT-DT4 in water due to the presence of Ag and Cu₂O nanoparticles.     

Facile synthesis of MnO2/CNT nanocomposite and its electrochemical performance for supercapacitors

A nanocomposite of manganese dioxide coated on the carbon nanotubes (MnO₂/CNTs) was synthesized by a facile direct redox reaction between potassium permanganate and carbon nanotubes without any other oxidant or reductant addition. The morphology, microstructure and crystalline form of this MnO₂/CNT nanocomposite were characterized by scanning electron microscopy (SEM), transition electron microscopy (TEM), X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS). The electrochemical properties are characterized by cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS) and galvanostatic charge/discharge (GCD). The results show that the facile prepared MnO₂/CNTs nanocomposite shows specific capacitance of 162.2 F g⁻¹ at the current density of 0.2 A g⁻¹ and excellent charge/discharge property with 90% of its specific capacitance kept after 2000 cycles at the current density of 5 A g⁻¹.     

Catalytic Graphitization of Phenolic Resin

The catalytic graphitization of thermal plastic phenolic-formaldehyde resin with the aid of ferric nitrate(FN) was studied in detail.The morphologies and structural features of the products including onion-like carbon nanoparticles and bamboo-shaped carbon nanotubes were investigated by transmission electron microscopy(TEM),high-resolution transmission electron microscopy(HRTEM),X-ray diffraction and Raman spectroscopy measurements.It was found that with the changes of loading content of FN and residence time at 1000 ℃,the products exhibited various morphologies.The TEM images showed that bamboo-shaped carbon nanotube consisted of tens of bamboo sticks and onion-like carbon nanoparticle was made up of quasi-spherically concentrically closed carbon nanocages.     

碳纳米管的催化裂解聚苯乙烯法的制备及其表征研究

利用流动催化裂解法以聚苯乙烯为碳源,二茂铁为催化剂前躯体制备出了碳纳米管.用扫描电子显微镜,透射电子显微镜,拉曼光谱和X射线衍射对碳纳米管的结构进行了表征.再者,通过导入噻吩,合成了一种有很多细碳纳米管分支的碳纳米管.该制备过程工艺简单,碳源价格低廉.利用这个方法,通过控制条件,可得到不同结构的碳纳米管.     

Synthesis and characterization of anatase and rutile TiO2 nanorods by template-assisted method

Well-aligned anatase and rutile TiO₂ nanorods and nanotubes with a diameter of about 80–130 nm have successfully been fabricated via sol-gel template method. The prepared samples were characterized by using thermogravimetric (TG) and differential thermal analysis (DTA), X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and energy dispersive X-ray spectroscopy (EDS). The XRD results indicated that the TiO₂ nanorods were crystallized in the anatase and rutile phases, after annealing at 400–800 °C for different periods of time from 0.2 to 10 h.     

一维纳米材料的ECR-CVD方法制备

应用电子回旋共振微波等离子体化学气相沉积方法(ECR-CVD)进行了一维纳米材料的制备.以Fe3O4纳米粒子为催化剂,采用不同的气源,在多孔硅基底上制备出了碳纳米管、掺硼碳纳米管以及异质结构的纳米管.利用扫描电子显微镜(SEM)、透射电子显微镜(TEM)和 X射线光电子谱(XPS)对样品的形貌、结构及组分进行表征.     

Synthesis and characterization of amorphous hollow carbon spheres

Nanostructured carbon materials have attracted enormous attention in last two decades due to their unique chemical, electrical, and mechanical properties. In this work, amorphous hollow carbon spheres (AHCSs) with diameters in the range of 100–750 nm, which are dispersed among bent graphitized carbon nanotubes, are synthesized by using radio frequency plasma enhanced chemical vapor deposition in mixed CH₄/H₂ gases. The carbon spheres were characterized with scanning electron microscope, energy-dispersive X-ray spectroscopy, Raman spectroscopy, and transmission electron microscopy. It is found that MgO and Co/Ni nanoparticles as well as hydrogen play crucial roles in the formation of AHCSs. Moreover, a possible growth mechanism of AHCSs was proposed. The results of this study provide new insights into the fundamental understanding of nonstructural carbon materials toward applications in nanodevices.     

Effect of milling time in characteristics of the powder Cu-5wt.%Graphite

Composites of Cu-5wt.%Graphite were prepared by high-energy milling, under argon atmosphere for milling time of up to 50 h, to investigate the influence of the milling time on the size and dispersion of the copper and carbon phases. The formation of a monophasic carbon-copper solid solution was also investigated. The powder samples were collected at different times and characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM and FESEM), transmission electron microscopy (TEM), energy dispersive X-ray spectroscopy (EDS) and Raman spectroscopy. Composite particles were formed by fragments of graphite embedded in the soft Cu matrix. After 50 h of milling, the Cu phase had a crystallite size of 24 nm and micro-strain of 0.26 %. The lattice parameter showed a reduction of 0.001545 nm and reached a value of 0.360152 nm. Furthermore, no carbon diffraction peak was observed in the milled powders, due to the small graphite crystallites. Meanwhile, the Raman spectra showed that the carbon phase remains crystalline, even after 50 h of milling. When the composite was annealed at 600 °C, for 1 h and under argon atmosphere, no carbon precipitate was observed. These results suggest the absence of the formation of a solid solution of carbon in copper.     

Preparation and characterization of γ-MnO2/CNTs nanocomposite

A layer of manganese dioxides (γ-MnO₂) was adsorbed upon carbon nanotubes (CNTs) surface by using a chemical deposit process. The morphologies of the MnO₂/CNTs composite were characterized using transmission electron microscopy (TEM), energy-dispersive X-ray spectrometry (EDS), X-ray diffraction (XRD) and laser Raman spectroscopy (RS). It is found that the adsorbed layer belongs to the γ-MnO₂ nanoparticles in the size of about 10 nm, and coated homogeneously around the CNTs. It is expected that this γ-MnO₂/CNTs composite will be applied to make supercapacitors.     

Effects of boron-doping on the morphology and magnetic property of carbon nanotubes

Boron carbide nanotubes (nano-fibers) was prepared by B powder and carbon nanotubes (CNTs) at high temperature in a vacuumed quartz tube. The morphology, microstructure, component and magnetic property of samples were characterized by transmission electron microscopy (TEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and magnetic property measurement system (MPMS) controller. The results showed that B-doping CNTs have great difference in the morphology and magnetic property from those of pristine CNTs. __________ Translated from Journal of Functional Materials, 2006, 37(9): 1398–1400 (in Chinese)