碳纳米管/氧化镁纳米复合材料的制备和表征

以碳纳米管为模板,采取前驱物分解法合成了碳纳米管/氧化镁纳米复合材料,用XRD、IR、SEM和TG-DTG对产物进行了表征.结果表明,产物是由氧化镁均匀包裹在碳纳米管上构成的一种复合材料,管径约100nm.和碳纳米管相比,复合材料管径变粗且表面粗糙.     

Structural and morphological studies of zinc oxide incorporating single-walled carbon nanotubes as a nanocomposite thin film

Pure zinc-oxide and a composition of zinc oxide-single walled carbon nanotubes (ZnO-SWCNTs) thin films were prepared by using a sol–gel doctor blade technique. A precursor of zinc acetate dehydrate (Zn(CH₃COO)₂·2H₂O), absolute ethanol (C₂H₅OH) and triethanolamine were mixed in one solution. Non-acid treatment SWCNTs were doped in the prepared solution. Structural and morphological properties of ZnO and ZnO-SWCNTs thin films were studied by means of X-ray diffractometer (XRD), field-emission scanning electron microscopy (FESEM), atomic force microscopy (AFM) and transmission electron microscopy (TEM). XRD measurements indicated that the crystallite size of ZnO was bigger than the crystallite size of ZnO-SWCNTs; 0.4331 and 0.3386 nm, respectively. The FESEM images showed the hexagonal and nanorod structures of ZnO thin film and a broccoli-like ZnO nanostructures coated with CNTs for ZnO-SWCNTs thin film. The AFM analysis revealed smoother surface morphology of ZnO-SWCNTs thin film compared to the surface of pure ZnO thin film. TEM results captured the inner structures of ZnO and ZnO-SWCNTs. Inner and outer diameter of non-acid treatment SWCNTs were recorded about 5.09 and 14.95 nm, respectively. Photovoltaic performance of ZnO-SWCNTs based dye-sensitized solar cell (DSSC) showed high power conversion efficiency of 0.102 % compared to ZnO based DSSC (0.019 %). This study suggests that SWCNTs should be acid-treated to produce highly porous structure and greater surface area for better photovoltaic performance of the DSSCs.     

Synthesis of uniform double-walled carbon nanotubes using iron disilicide as catalyst

The preparation of carbon nanotube (CNT) materials with high purity is critical for many potential applications. These materials not only need to be free of carbonaceous impurities but also have uniform diameters. Within the CNT family, double-walled carbon nanotubes (DWNTs), as the simplest member of multiwalled carbon nanotubes, have demonstrated good potential in many bulk applications. However, the synthesis of DWNTs with uniform diameter and high purity is still a challenge. Here, a method to prepare high-purity DWNTs using iron disilicide (FeSi2) as catalyst is demonstrated. Over 90% of CNTs in the sample were DWNTs with a narrow diameter distribution in the range of 4-5 nm. An additional advantage of using FeSi2 as catalyst is to simplify the process to prepare suitable catalyst because commercially available FeSi2 can be used directly without any further treatment.     

Synthesis of carbon nanotubes using Ni95Ti5 nanocrystalline film as a catalyst

Carbon nanotubes (CNTs) were synthesized by low-pressure chemical vapour deposition (LPCVD) using N2:C2H2:H2 gas mixtures on nanocrystalline Ni95Ti5 film. This nanocrystalline film was deposited on silicon substrate using vapour condensation method. The growth temperature and growth time was kept at 800 degrees C and 30 mins, respectively and the pressure was maintained at 10 Torr. The growth mechanism of CNTs was investigated using FESEM, TEM, HRTEM, and Raman Spectroscopy. From FESEM image of Ni95Ti5 nanocrystalline film, it is clear that the particle size varies from 5-10 nm. EDX analysis suggests that Ni95Ti5 alloy contains Ni and Ti both. It is clear from TEM images that CNTs are multiwalled with the diameter varying from 10-30 nm and length of several micrometers. HRTEM image shows that the structure of these multi-walled nanotube (MWNTs) is bamboo-shaped and the catalyst exists at the tip of MWNTs. Fourier Transform Raman Spectroscopy confirmed that graphitic structure of as-prepared CNTs. Field emission measurements reveal that the carbon nanotubes grown for 30 mins showed a turn-on field of 7.2 V/microm, when the current density achieves 10 microA/cm2. The field enhancement factor was calculated to be 708.50 for carbon nanotubes grown for 30 mins.     

Synthesis and characterization of phospholipid-modified multiwalled carbon nanotubes

A simple three-step strategy to functionalize multiwalled carbon nanotubes using 1,2-distearoyl-sn-glycero-3-phosphoethanolamine phospholipids has been described. The resulting phospholipid-modified multiwalled carbon nanotubes were analyzed by TEM, AFM, NMR, IR, UV-vis and TGA techniques. The experimental results show that the use of amine-terminated phospholipids not only improves the dispersity of multiwalled carbon nanotubes in both aqueous and organic solvents greatly, but also results in the significant enhancement of biocompatibility. These findings will serve as a future biological platform for new devices ranging from biosensors to nano-detectors.     

W doped vanadium oxide nanotubes: Synthesis and characterization

W doped vanadium oxide nanotubes (VONTs) were prepared via a rheological phase reaction followed by self-assembling process. The nanotubes were characterized by elemental analysis, IR, XRD, SEM, TEM, HRTEM, SAED and XPS. Elemental analysis, IR, XRD, SAED and XPS could confirm the crystalline characteristic of the W doped VONTs, while the SEM, TEM, and HRTEM confirmed their morphology and microstructure.     

Growth and characterization of bamboo-shaped carbon nanotubes using nanocluster-assembled ZnO:Co thin films as catalyst

Bamboo-shaped carbon nanotubes (CNTs) had been successfully fabricated by a plasma enhanced chemical vapor deposition method, in which nanocluster-assembled ZnO:Co thin film was used as catalyst. It was found that bamboo-shaped CNTs were generally grown in a direction perpendicularly to the substrate surface with the tops of CNTs dominated by the droplet-like catalyst covered by the carbon layer. The diameter of CNTs was ranged from 20-50 nm. High resolution of TEM image showed that the typical CNT had a multi-walled structure with an inner core presented. The ordered graphite layers were inclined to an axis of CNT about 18 degrees and the interlayer space of a CNT was about 0.35 nm. Two peaks in Raman spectrum at 1586 cm(-1) and 1372 cm(-1) were identified as G-band and D-band for graphite, respectively. The results showed that catalyst based on ZnO:Co thin films could be used for the growth of CNTs with bamboo-shaped structure.     

The growth of carbon nanotubes on large areas of silicon substrate using commercial iron oxide nanoparticles as a catalyst

A new approach to chemical vapour deposition (CVD) growth of carbon nanotubes (CNTs) using commercial magnetite nanoparticles, avoiding its in situ synthesis, is reported. Commercial magnetite nanoparticles were used as catalyst material to growth multiwalled carbon nanotubes by chemical vapour deposition onto a silicon substrate of several square centimeters in area. It is shown that the application of an alternating electric field during the deposition of catalytical nanoparticles is an effective technique to avoid their agglomeration allowing nanotube growth. Scanning electron microscopy showed that the nanotubes grow perpendicularly to the substrate and formed an aligned nanotubes array. The array density can be controlled by modifying the deposited nanoparticle concentration.     

碳纳米管/导电聚苯胺纳米复合纤维的合成与表征

为实现碳纳米管在树脂内形成一体化导电网络，从而制备出透明导电性能最优的有机透明导电涂层，必须把导电性的碳纳米管纤维在树脂内有效地组装成一体化导电结构网络。本文报道运用在树脂内可以自组装的导电苯胺来实现碳纳米管纤维自组装的方法．合成出了导电聚苯胺纳米薄膜均匀包覆的碳纳米管/导电聚苯胺纳米复合纤维．并运用透射电镜、傅立叶红外光谱以及四探针法表面电阻测试仪对合成出的具有精细微观结构的纳米复合纤维进行了表征．发现合成出了理想的碳纳米管/导电聚苯胺纳米复合纤维，并且其导电性较碳纳米管和导电聚苯胺自身都有大幅度的提高。这种特殊结构的纳米复合纤维的制备为组装高性能的聚合物基透明导电涂层奠定了坚实基础，而且这种自组装方法为各种纳米纤维的组装提供了可能。     

Synthesis and characterization of Rosebengal/folicacid-functionalized multiwall carbon nanotubes

Multiwall carbon nanotubes (MWCNTs) were functionalized with a photosensitizer, rosebengal (RB), and folicacid (FA), an anti-cancer drug simultaneously and individually, which was characterized with various analytical instruments like Fourier Transform Iinfrared (FTIR) spectroscopy, UV–Vis spectroscopy, Thermogravimetric analysis (TGA), Photoluminescence (PL) spectroscopy, X-ray photoelectron spectroscopy (XPS), and Transmission electron microscopy (TEM). FTIR spectra confirmed the chemical modification of MWCNT. The chemical functionalization of MWCNT with RB was further supported by UV–Vis and PL spectra.     

Synthesis and characterization of carbon nanoribbons and single crystal iron filled carbon nanotubes

Carbon nanoribbons and single crystal iron filled multiwall carbon nanotubes (MWCNTs) have been synthesized by simple pyrolysis technique. SEM investigation shows that the material consist mainly carbon nanoribbons and carbon nanotubes (CNTs). X-ray diffraction (XRD), electron energy loss spectroscopy (EELS), electron energy dispersive X-ray (EDX), transmission electron miscroscopy (TEM) and highresolution transmission electron miscroscopy (HRTEM) studies reveal carbon nanotubes are filled with α-Fe. Closer inspection of HRTEM images indicated that the bcc structure α-Fe nanowires are monocrystalline and Fe (1 1 0) plane is indeed perpendicular to the G (0 0 2) plane, whereas orientation of (0 0 2) lattice planes of carbon nanoribbon is perpendicular to the axis of growth. Magnetic properties studied by superconducting quantum interference device (SQUID) at 300 K and 10 K exhibited coercivity of 1037 Oe and 2023 Oe. The large coercitivity is strongly attributed to the small size monocrystalline single phase α-Fe, single domain nature of the encapsulated Fe crystal, magnetocrystalline shape anisotropy and ferromagnetic behaviour of localized states at the edges of the carbon nanoribbons.     

Mass-produced multi-walled carbon nanotubes as catalyst supports for direct methanol fuel cells

Commercially mass-produced multi-walled carbon nanotubes, i.e., VGNF (Showa Denko Co.), were applied to support materials for platinum-ruthenium (PtRu) nanoparticles as anode catalysts for direct methanol fuel cells. The original VGNFs are composed of high-crystalline graphitic shells, which hinder the favorable surface deposition of the PtRu nanoparticles that are formed via borohydride reduction. The chemical treatment of VGNFs with potassium hydroxide (KOH), however, enables highly dispersed and dense deposition of PtRu nanoparticles on the VGNF surface. This capability becomes more remarkable depending on the KOH amount. The electrochemical evaluation of the PtRu-deposited VGNF catalysts showed enhanced active surface areas and methanol oxidation, due to the high dispersion and dense deposition of the PtRu nanoparticles. The improvement of the surface deposition states of the PtRu nanoparticles was significantly due to the high surface area and mesorporous surface structure of the KOH-activated VGNFs.     

Heterogeneous cycloaddition of styrene oxide with carbon dioxide for synthesis of styrene carbonate using reusable lanthanum–zirconium mixed oxide as catalyst

Clean Technologies and Environmental Policy - Development of environmentally benign green processes for utilization of carbon dioxide to synthesize value-added compounds using heterogeneous...     

Synthesis and characterization of alumina-coated carbon nanotubes and their application for lead removal

Alumina-coated multi-wall carbon nanotubes were synthesized and characterized by scanning electron microscopy, X-ray diffraction, and FTIR. They were used as an adsorbent for the removal of lead ions from aqueous solutions in two modes, batch and fixed bed. In the batch mode, experiments were carried out to investigate the effect of contact time, agitation speed, adsorbent dosage and solution pH on the removal of lead. The coated nanotubes exhibit better removal ability over uncoated. For fixed-bed columns, thickness of the layer and flow rate were investigated. Increasing the thickness and decreasing the flow rate enhanced the removal of lead. The prepared adsorbent displayed the main advantage of separation convenience when a fixed-bed column was used compared to the batch adsorption treatment.     

Synthesis and characterization of water-soluble multiwalled carbon nanotubes grafted by a thermoresponsive polymer

Water-soluble multiwalled carbon nanotubes (MWNTs) with temperature-responsive shells were successfully prepared by grafting poly (N-isopropylacrylamide) (PNIPAM) from the sidewalls of MWNTs, via surface reversible addition-fragmentation chain transfer (RAFT) polymerization using RAFT agent functionalized MWNTs as the chain transfer agent. Thermogravimetric analysis (TGA) measurements showed that the weight composition of the as-grown PNIPAM polymers on the MWNTs can be well controlled by the feed ratio (in weight) of NIPAM to RAFT agent functionalized MWNTs (MWNT-SC(S)Ph). The MWNT-g-PNIPAM has good solubility in water, chloroform, and tetrahydrofuran (THF). Transmission electron microscope (TEM) and scanning electron microscope (SEM) images also showed that the MWNT-g-PNIPAM was dispersed individually and eventually bonded with the polymer layer by surface RAFT polymerization. The PNIPAM shell is very sensitive to a change of temperature. This method could find potential applications by grafting other functional polymer chains onto MWNTs.     

Moderate temperature synthesis of single-walled carbon nanotubes on alumina supported nickel oxide catalyst

A simple nickel oxide catalyst has been developed in synthesizing single-walled carbon nanotubes (SWNTs) at moderate temperature. The catalyst used in the experiment was without a preceding reduction in hydrogen flow. The synthesis of SWNTs was performed at a temperature of 700 °C, which represents a moderate reaction temperature. The presence of SWNTs on the catalyst was confirmed by transmission electron microscope (TEM) and Raman spectroscope. The Raman spectrum shows a strong intensity at the radial breathing mode, indicating that the occurrence of SWNTs was dominant. Raman data further reveals that the synthesized SWNTs had the diameters in the range from 0.58 to 2.02 nm.     

Synthesis of carbon nanotubes and nanospheres with controlled morphology using different catalyst precursors

Carbon nanotubes and carbon nanospheres have been selectively synthesized in a polypropylene matrix by simply altering the catalyst precursor. When a mixture of ferrocene and cobalt (II) acetate was added to the polypropylene, well-dispersed carbon nanotubes were produced. When only cobalt (II) acetate was added, however, carbon nanospheres were obtained. In a third case, when the added catalyst precursor was ferrocene, no graphitic carbon was formed.     

Synthesis and characterization of carbon nanotubes grown on montmorillonite clay catalysts

Multiwall carbon nanotubes have been grown on montmorillonite clay catalysts through anchoring on FeCo nanoparticles. The starting clay is a commercial sodium-rich montmorillonite in which the intercalated sodium ion was exchanged for cobalt(II) and iron(III) ions via mechanical agitation or sonication, both with and without subsequent centrifugation. The cobalt-iron intercalate clay was used as a catalyst for the synthesis of carbon nanotubes via decomposition of ethylene at 700 °C. The largest carbon deposit was obtained for catalysts prepared with 3 or 4 cation exchange equivalents. X-ray diffraction indicates both that the basal spacing of the clay increases from 12.43 Å to 16.4 Å upon intercalation of cobalt and iron. Atomic absorption analysis of the catalysts indicates that virtually all of the sodium ions originally present in the clay have been replaced by iron(III) and cobalt(II). Transmission electron micrographs show the presence of multiwall carbon nanotubes with inner and outer diameters of ca. 10 nm and 20 nm grown on metal particles present on the plates of catalysts. The iron-57 Mössbauer spectra indicate that the intercalated clay contains iron(III) in octahedral and tetrahedral sites and iron(II) in octahedral sites, the catalysts contain an extensive amount of small superparamagnetic particles of α-Fe₂O₃ and that the carbon-nanotube catalyst composites show the presence of iron(II) and iron(III) paramagnetic doublets, characteristic of a reduced montmorillonite, and of sextets that are characteristic of an FeCo alloy and of Fe₃C cementite. The Mössbauer spectra indicate that the carbon nanotubes grow on FeCo metallic nanoparticles and bond to these particles through the formation of cementite.     

Synthesis and characterization of polyurethane-grafted single-walled carbon nanotubes via click chemistry

Polyurethane (PU)-grafted carbon nanotubes were synthesized by the coupling of alkyne moiety decorated single walled carbon nanotube (SWCNT) with azide moiety containing PU using Cu(I) catalyzed Huisgen [3 + 2] cycloaddition click chemistry. The azide moiety containing poly(s-caprolactone)diol was synthesized by ring-opening polymerization and further used for PU synthesis. Alkyne-functionalizion of SWCNT was completed by the reaction of p-aminophenyl propargyl ether with SWCNT using a solvent free diazotization procedure. Nuclear magnetic resonance, Fourier transform infrared, and Raman spectroscopic measurements confirmed the functionalization of SWCNT. Scanning electron microscopy and transmission electron microscopy images showed an excellent dispersion of SWCNTs, and specially debundling of SWCNTs could be observed due to polymer assisted dispersion. A quantitative grafting was successfully achieved even at high content of functional groups.