Preparation of well-aligned carbon nanotubes/silicon nanowires core-sheath composite structure arrays in porous anodic aluminum oxide templates

The well-aligned carbon nanotubes (CNTs) arrays with opened ends were prepared in ordered pores of anodic aluminum oxide (AAO) template by the chemical vapor deposition (CVD) method. After then, silicon nanowires (SiNWs) were deposited in the hollow cavities of CNTs. By using this method, CNTs/SiNWs core-sheath composite structure arrays were synthesized successfully. Growing structures and physical properties of the CNTs/SiNWs composite structure arrays were analyzed and researched by the scanning electron microscopy (SEM), transmission electron microscopy (TEM) and X-ray diffraction spectrum (XRD), respectively. The field emission (FE) behavior of the CNTs/SiNWs composite structure arrays was studied based on Fowler-Nordheim tunneling mechanism and current-voltage (/-V) curve. And the photoluminescence (PL) was also characterized. Significantly, the CNTs/SiNWs core-sheath composite structure nanowire fabricated by AAO template method is characteristic of a metal/semiconductor (M/S) behavior and can be     

Hierarchically porous carbon cages synthesized through in situ migration of templates

Hierarchically porous networks have been fabricated through immigration of templates.     

Electrochemistry of polystyrene intercalated vertically aligned single- and double-walled carbon nanotubes on gold electrodes

Electrochemical electrodes incorporating double- and single-walled carbon nanotubes (CNTs) were fabricated on cysteamine modified flat gold substrates. Through covalent coupling of the amine end groups with carboxyl functionalized CNTs, a dense forest of vertically aligned CNTs was produced. To these a 30 nm thick insulating polystyrene layer was spin coated, resulting in exposure of the uppermost carbon nanotube ends. The electrochemical performance of each electrode was then determined using the redox probe ruthenium hexaamine. Once surrounded by polymer, the double-walled CNTs (DWCNTs) showed an improved electron transfer rate, compared to the single-walled electrode. This improvement was attributed to the protection of the electronic properties of the inner wall of the DWCNT during the chemical modification and suggests that DWCNTs may offer a useful alternative to SWCNTs in future electrochemical sensors and biosensors.     

不同活性炭负载的镍基催化剂上废塑料裂解制碳纳米管性能

以椰壳炭、竹炭和木炭三种活性炭为载体,采用浸渍法制备炭负载金属镍的催化剂,考察其在废塑料裂解制备碳纳米管过程中的催化反应性能;采用X射线衍射、扫描电镜、透射电镜、拉曼光谱仪、同步热分析仪、比表面积分析仪等手段分析了催化剂和产物碳纳米管的形貌和结构。结果表明,椰壳活性炭为载体制备的镍基催化剂上碳纳米管产量最高、石墨化程度最好。以椰壳活性炭为载体制备的镍基催化剂为例,研究了反应温度和镍负载量对其催化性能的影响。     

Effect of drying on porous silicon

The phase transition of a fluid - in particular water - confined in the pores of silicon during drying is studied. The influence of this process on surface size and porosity is discussed. Methods of air drying, supercritical drying and freeze drying are considered. This revised version was published online in July 2006 with corrections to the Cover Date.     

Catalytic synthesis of carbon nanotubes over ordered mesoporous matrices

Pyrolytic decomposition of acetylene over the surface of nickel-, cobalt- and iron-containing ordered mesoporous MCM-41 silicas has been studied. Catalytically active matrices have been prepared by chemisorption of volatile metal acetylacetonate complexes on the silica surface. Reduction of the supported metal-containing compounds was carried out in hydrogen or acetylene atmosphere. Acetylene is used not only as a source of carbon in synthesis of the nanostructures but also as a reagent capable of reducing metal ions in the surface chemical compounds. Formation of carbon nanotubes and nanofibers is shown to depend on the pyrolysis conditions.     

Pyrolysis of chloroplatinic acid to directly immobilize platinum nanoparticles onto multi-walled carbon nanotubes

Platinum nanoparticles supported on multi-walled carbon nanotubes (Pt/MWCNTs) were first prepared by simple pyrolysis of H₂PtCl₆ solution. The structure of Pt/MWCNTs was characterized with X-ray diffraction (XRD), scanning electron microscope (SEM), and the results showed that the diameter of the obtained platinum nanoparticles immobilized on MWCNTs was below 50 nm, although the obtained platinum nanoparticles were not well uniformly dispersed on the surface of MWCNTs. The electrocatalytic performance of Pt/MWCNTs electrode for methanol oxidation reaction (MOR) was also investigated by linear sweep voltammetry (LSV), indicating that it was possible to employ the obtained platinum nanoparticles as anode material in fuel cell. Developing a novel and simple method to prepare platinum nanoparticles onto MWCNTs is the main contribution of this letter. Published in Russian in Elektrokhimiya, 2008, Vol. 44, No. 8, pp. 1050–1053. The text was submitted the authors in English.     

Preparation of cobalt hexacyanoferrate nanowires using carbon nanotubes as templates

A simple and convenient method for preparation of cobalt hexacyanoferrate (CoHCF) nanowires by electrodeposition was reported. Multiwall carbon nanotubes (MWNTs) were used as templates to fabricate CoHCF nanowires. MWNTs could affect the size of CoHCF nanoparticles and made them grow on the sidewalls of carbon nanotubes during the process of electrodeposition. Thus CoHCF nanowires could be obtained by this method. Field-emission scanning electron microscopy, UV-vis spectroscopy, Fourier transform infrared spectroscopy and X-ray photoelectron spectroscopy were used to characterize these nanowires. These results showed the CoHCF nanowires could be easily and successfully obtained and it gave a novel approach to prepare inorganic nanowires.     

氮掺杂碳纳米管包覆碳化硅作为不含金属的催化剂(英文)

A hierarchical metal-free catalyst consisting of nitrogen-doped carbon nanotubes decorated onto a silicon carbide (N-CNTs/SiC) macroscopic host structure was prepared. The influence of N-CNTs incorporation on the physical properties of the support was evaluated using different characterization techniques. The catalyst was tested as a metal-free catalyst in the selective oxidation of H2S and steam-free dehydrogenation of ethylbenzene. The N-CNTs/SiC catalyst exhibited extremely good desulfurization performance compared to a Fe2O3/SiC catalyst under less conducive reaction conditions such as low temperature, high space velocity, and a low O2-to-H2S molar ratio. For the dehy-drogenation of ethylbenzene, a higher dehydrogenation activity was obtained with the N-CNTs/SiC catalyst compared to a commercial K-Fe/Al2O3 catalyst. The N-CNTs/SiC catalyst also displayed good stability as a function of time on stream for both reactions, which was attributed to the strong anchoring of the nitrogen dopant in the carbon matrix. The extrudate shape of the SiC support allowed the direct macroscopic shaping of the catalyst for use in a conventional fixed-bed reactor without the problems of catalyst handling, transportation, and pressure drop across the catalyst bed that are encountered with nanoscopic carbon-based catalysts.     

Effects of carbon nanotubes on polymer physics

A single carbon nanotube has many similarities with an individual polymer chain including the fact that the end‐to‐end length of both are often about the same and the diameter of the chain is about the same (for single‐walled nanotubes) or only ～10 to 20 times larger (for multiwalled nanotubes). The combination of the solid surface and the similarity of the two materials means that polymer physics are altered in manners not seen with any other type of commonly used filler. The purpose of this review is to update a chapter that appears in a recent tome by Grady (2011) and describe how polymer physics is altered in composites that contain carbon nanotubes. Subjects that will be discussed include chain configuration, glass transition, polymer diffusion, unit cells and crystalline superstructure (lamellae, spherulites and shish‐kebabs), and crystallization kinetics. © 2012 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys, 2012     

超临界水中煤基多孔炭孔隙形成过程的研究

在半连续超临界水反应器(SCWR)中考察了不同温度、反应时间下昭通褐煤的转化特性,结合半焦有机官能团及碳微晶结构分析,推测在超临界水中半焦孔隙的形成过程以及煤中矿物质的作用。结果表明,超临界水首先快速萃取出褐煤热解产物,促进了半焦石墨化,形成良好的炭素前驱体,此过程对半焦孔结构基本无作用;当温度高于550 ℃,炭素前驱体发生气化反应,产生了较多的C-O-C交联结构,比表面积明显提高,逐渐形成多孔炭材料;脱灰后的煤在升温过程中具有更高的萃取率,形成有利于微孔产生的炭素前驱体,煤中的矿物质更有利于中孔的形成。     

Cytotoxicity of carbon nanotubes

With large-scale production and application at large scale, carbon nanotubes (CNTs) may cause ad-verse response to the environment and human health. Thus, study on bio-effects and safety of CNTs has attracted great attention from scientists and governments worldwide. This report briefly summa-rizes the main results from the in vitro toxicity study of CNTs. The emphasis is placed on the descrip-tion of a variety of factors affecting CNTs cytotoxicity, including species of CNTs, impurities contained, lengths of CNTs, aspect ratios, chemical modification, and assaying methods of cytotoxicity. However, experimental information obtained thus far on CNTs' cytotoxicity is lacking in comparability, and some-times there is controversy about it. In order to assess more accurately the potential risks of CNTs to human health, we suggest that care should be taken for issues such as chemical modification and quantitative characterization of CNTs in cytotoxicity assessment. More importantly, studies on physical and chemical mechanisms of CNTs' cytotoxicity should be strengthened; assaying methods and evaluating criteria characterized by nanotoxicology should be gradually established.     

Efficient thermal conversion of polyyne-type conjugated polymers to nano-structured porous carbon materials

Summary Some aromatic based conjugated polymers having carbon-carbon triple bonds moiety were synthesized and carbonized. The polymers were efficiently carbonized by heating up to 900°C under an argon atmosphere, affording porous carbons in high yields. The polymer characteristics were appropriate to form nano-structured carbons in the pyrolytic carbonization process. The carbon materials were consisted of 2-4 nm sized graphitic crystallites and had slit-shaped micropores with ca. 0.7 nm pore width. Structural defects in the pre-carbon materials caused generation of mesopores with ca. 4 nm pore width after carbonization.     

Synthesis of carbon nanotubes by catalytic pyrolysis method with Feitknecht compound as precursor of NiZnAl catalyst

Carbon nanotubes are synthesized by catalytic pyrolysis method with a kind of new type catalyst--nickel-zinc-alumina catalyst prepared from Feitknecht compound. Tubular carbon nanotubes, bamboo-shaped carbon naotubes, herringbone carbon nanotubues and branched carbon nanotubes are all found formed at moderate temperature. It is important for the formation of quasi-liquid state of the metal nanoparticles at the tip of carbon naotubes during the growth of carbon nanotubes to lead to different kinds of carbon nanotubes. It is likely that the addition of zinc make the activity of nickel catalyst after calcinations and reduction changed strangely.     

溶剂热合成碳纳米管

自1991年Iijima发现碳纳米管以来,碳纳米管因其独特的结构和物理化学性质而成为人们的研究热点。     

Quantum confinement effect in electroluminescent porous silicon

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