洁净单壁碳纳米管在Fe2O3／Al2O3二元气凝胶催化剂上的水辅助合成

分别以甲烷-氧气和甲烷-氢气-水的混合气作为反应气源,利用Fe2O3/Al2O3二元气凝胶作为催化剂于900℃反应30min合成了单壁碳纳米管.并采用SEM、XRD、TEM,高分辨透射电子显微镜(HRTEM)以及Raman光谱等分析技术对所制得的碳产物的结构和形貌进行了表征,以研究反应气氛中水蒸气的引入对单壁碳纳米管生长的影响.结果表明:反应气氛的组成对最终所形成的碳产物的产率和结构有着密切的关联.通过控制氢气载入甲烷-氢气-水的混合气氛中水蒸气的量可以合成低无定形碳的沽净单壁碳纳米管.     

Probabilistic model of fatigue fracture of carbon nanostructures

Presented evaluation of risk of fatigue fracture of carbon nanostructures (CN) is based on: (a) the criterion of the threshold of the dissipated energy of tensile stresses, and (b) simulation of stochastic character of fracture by the failures in queueing system. The assessments of probability of fatigue fracture of CN in conditions of uniaxial tension, plane torsion and uniaxial compression are done.     

乙烯催化裂解法选择性合成纳米炭纤维

通过采用不同金属催化剂进行乙烯催化裂解制备了具有不同微观结构的纳米炭纤维。利用纳米二氧化硅负载的铁、镍以及铁镍合金催化剂在适当的反应条件下分别制备了管状、实心鱼骨状以及空心鱼骨状的纳米炭纤维。由于金属催化剂与纳米二氧化硅间的强相互作用导致在低反应温度下也能达到高的反应活性，所以能够合成出高收率、小直径而且分布均匀的纳米炭纤维。不同结构的纳米炭纤维归因于金属催化剂的不同分散性以及不同的生长机理。通常利用铁催化剂进行乙烯裂解制备纳米炭纤维需要高于650℃，但是在我们的实验中发现500℃低温下利用纳米二氧化硅负载的铁催化剂进行乙烯裂解就能够合成出管状纳米炭纤维。     

Hot-filament CVD synthesis and application of carbon nanostructures

We have reported the catalyst-assisted hot-filament chemical vapor deposition (HFCVD) of various carbon nanostructures, such as carbon nanotube (CNT), nanoparticle (CNP), and nanofiber (CNF), and their application examples. In the case of CNT, vertically aligned high-density growth has been investigated in detail using in-situ optical reflectivity measurement. For CNF showing large field-emission currents, adsorbate-related emission behavior and the emission from patterned cathodes have been studied. Regarding CNP, the performances of a series of triode field emitters with CNP cathodes have been compared, and the application of CNP triode to miniature time-of-flight mass spectrometer has been discussed.     

壳状碳纳米颗粒的制备和分散

利用高功率CO2连续激光照射C2H2,使之热解,成功制备了中空壳状碳纳米颗粒(CNSs),为增强其分散性,用王水对所制备的CNSs进行表面处理。利用TEM、XRD、FTIR以及Zeta电位测量等技术对CNSs和经化学处理后的碳纳米颗粒(T-CNSs)进行了对比分析。结果表明:CNSs壳层内碳原子呈石墨状规则排列;T-CNSs表面带有含氧的亲水官能团,使其很容易分散;化学处理没有改变CNSs的结构。     

Synthesis of carbon nanostructures by graphite deformation during mechanical milling in air

Abstract

In this investigation, time-dependent carbon nanostructures were prepared by high-energy ball milling in the air from elemental graphite powders. Scanning electron microscopy (SEM), X-ray diffraction (XRD), Raman spectroscopy (RS), and high-resolution transmission electron microscopy (HRTEM) characterized the ball-milled powders. XRD analysis showed that the crystal size decreased with the milling time. Raman spectra confirmed the presence of carbon nanostructures with sp² hybridization. Meanwhile, HRTEM images revealed different carbon morphologies during the milling time. During the different stages, it appears distortion of layers, large tapes, polyhedral morphologies, nanocapsules, and nano-onions. These carbon nanostructures occur in regions where there is carbon accumulation. In this way, the ball milling process in air conditions can promote distorted carbon and different morphologies.     

ZnO 1-D nanostructures: Low temperature synthesis and characterizations

ZnO is one of the most important semiconductors having a wide variety of applications in photonic, field emission and sensing devices. In addition, it exhibits a wide variety of morphologies in the nano regime that can be grown by tuning the growth habit of the ZnO crystal. Among various nanostructures, oriented 1-D nanoforms are particularly important for applications such as UV laser, sensors, UV LED, field emission displays, piezoelectric nanogenerator etc. We have developed a soft chemical approach to fabricate well-aligned arrays of various 1-D nanoforms like nanonails, nanowires and nanorods. The microstructural and photoluminescence properties of all the structures were investigated and tuned by varying the synthesis parameters. Field emission study from the aligned nanorod arrays exhibited high current density and a low turn-on field. These arrays also exhibited very strong UV emission and week defect emission. These structures can be utilized to fabricate efficient UV LEDs.     

Facile synthesis of fluorescent carbon dots using watermelon peel as a carbon source

The synthesis of water-soluble fluorescent carbon dots (C-dots) has received much attention recently. Here, high quality fluorescent C-dots have been synthesized through low-temperature carbonization and simple filtration using watermelon peel, a waste and reproducible raw resource, as a novel carbon resource. This facile approach allows large-scale production of aqueous C-dots dispersions without any post-treatment process. The as-prepared C-dots possess small particle sizes (~ 2.0 nm), strong blue luminescence, acceptable fluorescence lifetime and good stability in a wide range of pH values (pH 2.0-11.0) and at a high salt concentration. Besides, the obtained C-dots have been successfully applied in live cell imaging, indicating these carbon nanoparticles can serve as high-performance optical imaging probes.     

Influence of architecture on the Raman spectra of acid-treated carbon nanostructures

Raman spectroscopy was used to characterise 11 varieties of carbon nanostructures (CNSs) consisting on seven varieties of commercial multi-walled carbon nanotubes, two types of carbon nanofibres and two types of lab-synthesised single-walled carbon nanotubes. The Raman spectra of these CNSs provided information on the structural ordering of the as-received (or as-synthesised) material. Additionally, the CNSs were chemically treated by two mixtures of nitric and sulphuric acids at markedly different concentrations and then characterised by Raman spectroscopy. The features of the G and D Raman bands of the CNSs were used to assess structural modifications and generation of defects induced by the acid treatments. Changes in the Raman spectra before and after acidic treatment depend strongly on the initial intensity ratio of the G to D bands and the architecture (number of layers or diameter) of the CNSs.     

On manifestation & physics of the Kurdjumov and spillover effects in carbon nanostructures,under intercalation of high density hydrogen

Abstract

Some experimental evidences and the physics (thermodynamics) of the nanoscale self-intercalation of high-density gaseous molecular hydrogen (ρ?≈?0.045?g/cm³, T?≈?300?K) into surface nanoclusters in highly oriented pyrolytic graphite and epitaxial graphene, as well as the nanoscale self-intercalation of high density solid molecular hydrogen (ρ?≈?0.5?g/cm³, T?≈?300?K, the compressed pressure ～ 0.5 Mbar) into graphite nanofibers are considered, with regard to the problem of compact and efficient hydrogen on-board storage and other clean energy applications. Perspectives of further developments of these results are considered, as well.     

水热法制备CdS纳米结构

利用氯化镉(CdC12)、硫脲(CO(NH2)2)和聚乙烯吡咯烷酮(PVP),在水热条件下获得了玉米棒状和花状等不同形貌的CdS纳米结构.采用X射线衍射(XRD)、扫描电镜(SEM)、透射电镜(TEM)、荧光发光光谱(PL)、紫外可见光分光光度计(UV-vis)对产物进行表征.结果表明:PVP对不同形貌CdS纳米结构的形成起关键作用,随着PVP量的增加,PVP选择性地吸附(102)晶面,抑制了该(102)晶面方向的生长,使产物的形貌由玉米棒状转变为花状;而花状纳米结构的紫外的吸收产生了红移现象,荧光性能无明显变化.     

Novel ZnO nanostructures grown on carbon nanotubes by thermal evaporation

We report on the formation of ZnO/carbon nanotubes heterostructures achieved by means of a thermal evaporation method. Scanning electron microscopy revealed that the main building block of the observed morphologies was the nanorod whose self-assembling resulted in various structures such as polypods and nano-hedgehogs, depending on various factors as well as the location of the ZnO-CNT junction. X-ray diffraction and photoluminescence spectroscopy were used to study the structure and optical properties of obtained nanostructures. Semi-empirical molecular orbital calculations gave evidence for the nature of the binding between ZnO and CNTs.     

Preparation of carbon nanostructures from medium and high ash Indian coals via microwave-assisted pyrolysis

This study is focused on valorizing low value and low quality Indian coals via microwave pyrolysis to produce good quality carbon nanostructures in the heat-treated coal char. The effects of operating conditions such as coal type, coal:susceptor (Fe) mass ratio, and microwave power on product yield and quality are evaluated. The quality of the heat-treated coal char was assessed using different characterization techniques such as electron microscopy, porosimetry, X-ray diffraction, and Raman spectroscopy. The addition of Fe enhanced the heating rates, and led to the formation of carbon nanotubes and nanoparticles. Increasing the proportion of Fe resulted in increase in size of nanotubes and nanoparticles, which is attributed to the fusion of small tubes and particles caused by enhanced localized heating. The yield of carbon nanostructures was more from medium ash (~45%) than from high ash coal (~37%) due to the high fixed carbon and low ash content in the former. In addition to char, coal tar and non-condensable gases were characterized. The major compounds in the coal tar were aromatic hydrocarbons, simple phenols and aliphatic hydrocarbons. Hydrogen and methane were the major gases from medium ash coal, while hydrogen, methane and CO were produced in significant quantities from high ash coal. Microwave-assisted pyrolysis is shown to be a promising process to produce carbon nanostructures in a short time period as compared to conventional thermal processes.     

碳纳米管阵列研究进展

在介绍CNT阵列性能的基础上,对国内外直接合成CNT阵列的方法进行了评述,重点阐述了各种方法的基本特点及CNT阵列的生长机理、结构控制和批量制备问题。进而探讨了CNT原生阵列、抽丝形成的CNT丝、以及CNT阵列分散后得到的CNTs在复合材料、力学增强、功能器件等方面的初步应用,展望了CNT阵列的发展趋势,指出低成本、大批量可控制备CNT阵列仍然是未来一段时间内国际研究热点。     

Comparison of dye solar cell counter electrodes based on different carbon nanostructures

Three characteristically different carbon nanomaterials were compared and analyzed as platinum-free counter electrodes for dye solar cells: 1) single-walled carbon nanotube (SWCNT) random network films on glass, 2) aligned multi-walled carbon nanotube (MWCNT) forest films on Inconel steel and quartz, and 3) pressed carbon nanoparticle composite films on indium tin oxide-polyethylene terephtalate plastic. Results from electrochemical impedance spectroscopy and electron microscopy were discussed in terms of the catalytic activity, conductivity, thickness, transparency and flexibility of the electrode films. The SWCNT films showed reasonable catalytic performance at similar series resistance compared to platinized fluorine doped tin oxide-coated glass. The MWCNTs had similar catalytic activity, but the electrochemical performance of the films was limited by their high porosity. Carbon nanoparticle films had the lowest charge transfer resistance resulting from a combination of high catalytic activity and dense packing of the material.     

Temperature effect on synthesis of different carbon nanostructures by sulfur-assisted chemical vapor deposition

The temperature effect on synthesizing different carbon nanostructures in the range of 820−1020 °C by sulfur-assisted chemical vapor deposition is investigated. When the growth temperature is no more than 900 °C (e.g. 820, 860, and 900 °C), carbon onions can be obtained, accompanying with some fishbone-like carbon nanofibers (CNFs), graphite sheet and carbon nanotubes (CNTs). When the growth temperature is increased to 940 °C or above (e.g. 980 and 1020 °C), the products are mainly CNTs. Furthermore, by comparing the nitrogen adsorption-desorption results of samples obtained with and without sulfur addition at each temperature, it is found that the specific surface area (SSA) of products can be remarkably enlarged after introducing small amount of sulfur during growth. This is favorable to their applications in areas like electrodes of supercapacitors, adsorbents, catalyst supports, and so on.     

分级结构沸石/泡沫炭整体复合材料的制备

用T型沸石/聚酰胺酸悬浊液浸渍聚氨酯泡沫,然后在900℃下热处理制备原位担载的T型沸石/泡沫炭复合材料。用SEM,XRD和物理吸附仪等设备对所得样品进行表征。结果表明:所得复合材料为分级结构整体块状材料,泡沫炭基体的大孔平均尺寸约为500μm;泡沫炭孔壁表面均匀镶嵌了大量沸石分子筛。所得复合材料的微孔孔径分布集中于0.45nm左右,比表面积达到328m2/g。复合材料中沸石分子筛自身的结构特性和化学组成保持不变。