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Xu Q.-F.,Shanghai JiaoTong University | Wang J.-N.,Shanghai Key Laboratory for Metallic Functional Materials
Frontiers of Materials Science in China | Year: 2010

Superhydrophobic and transparent coatings have been prepared by self-assembly of dual-sized silica particles from a mixed dispersion. The desirable micro/nano hierarchical structure for superhydrophobicity is constructed simply by adjusting the size and ratio of the dual-sized particles without organic/inorganic templates. The transparency of the prepared coatings is also researched, and the light scattering can be reduced by lowering the ratio of big sub-micro particles while the superhydrophobicity maintains unchanged. When nano particles with a diameter of 50 nm and sub-micro particles with a diameter of 350 nm are assembled, a superhydrophobic property with a water contact angle of 161° is achieved. Additionally, the coated glass is also very transparent. The highest transmittance of the coated glass can reach 85%. Compared to traditional colloid self-assembly approach, which often involves dozens of steps of layer-by-layer processing and organic/inorganic templates, the present approach is much simpler and has advantages for large-scale coating. © 2010 Higher Education Press and Springer-Verlag Berlin Heidelberg.

Paiva M.C.,University of Minho | Xu W.,University of Aarhus | Xu W.,Shanghai Key Laboratory for Metallic Functional Materials | Fernanda Proenca M.,University of Minho | And 3 more authors.
Nano Letters | Year: 2010

Carbon nanotubes (CNTs), functionalized by a cycloaddition reaction, were studied by ultrahigh vacuum scanning tunneling microscopy (STM). The STM images provided evidence for partial or total unzipping of the outer CNT layer. The formation of graphene ribbons was triggered by the STM tip, under specific operating conditions. A model for the unzipping is proposed, based on the perturbation of the φ-conjugation along the CNT surface induced by the cycloaddition reaction. © 2010 American Chemical Society.

Niu J.J.,Shanghai JiaoTong University | Wang J.N.,Shanghai Key Laboratory for Metallic Functional Materials
Acta Materialia | Year: 2010

The dependence on temperature and structure of the electrochemical activity of a catalyst supported on hollow carbon nanocages (HCNCs) with large scales (>5 g h-1) by a simple N2-bubbling floating method is discussed. The effect of gas flow on an HCNC-supported catalyst was systematically studied in our previous work. Here we specify the electrocatalytic activity of the samples with different temperatures and graphite structures under 900 and 1000 °C by cyclic voltammograms. The peak current density of H2-adsorption/desorption is four times higher than that of the commercial Pt/C (Vulcan XC-72). Besides the comparison with commercial carbon, the fuel cell performance was measured. The single fuel cell test for Pt/HCNCs showed a high turn-on voltage of 0.9 V and a relatively high power density of 0.13 W cm-2 under a low temperature of 60 °C and a low gas pressure of 1 atm. © 2009 Acta Materialia Inc.

Schnadt J.,University of Aarhus | Schnadt J.,Lund University | Xu W.,University of Aarhus | Xu W.,Shanghai Key Laboratory for Metallic Functional Materials | And 5 more authors.
Nano Research | Year: 2010

The adsorption of 2,6-naphthalenedicarboxylic acid (NDCA) molecules on the Ag(110), Cu(110), and Ag(111) surfaces at room temperature has been studied by means of scanning tunnelling microscopy (STM). Further supporting results were obtained using X-ray photoelectron spectroscopy (XPS) and soft X-ray absorption spectroscopy (XAS). On the Ag(110) support, which had an average terrace width of only 15 nm, the NDCA molecules form extended one-dimensional (1-D) assemblies, which are oriented perpendicular to the step edges and have lengths of several hundred nanometres. This shows that the assemblies have a large tolerance to monatomic surface steps on the Ag(110) surface. The observed behaviour is explained in terms of strong intermolecular hydrogen bonding and a strong surface-mediated directionality, assisted by a sufficient degree of molecular backbone flexibility. In contrast, the same kind of step-edge crossing is not observed when the molecules are adsorbed on the isotropic Ag(111) or more reactive Cu(110) surfaces. On Ag(111), similar 1-D assemblies are formed to those on Ag(110), but they are oriented along the step edges. On Cu(110), the carboxylic groups of NDCA are deprotonated and form covalent bonds to the surface, a situation which is also achieved on Ag(110) by annealing to 200 °C. These results show that the formation of particular self-assembled molecular nanostructures depends significantly on a subtle balance between the adsorbate-adsorbate and adsorbate-substrate interactions and that kinetic factors play an important role. © 2010 Tsinghua University Press and Springer-Verlag Berlin Heidelberg.

Teng S.J.,Shanghai JiaoTong University | Wang X.X.,Shanghai Key Laboratory for Metallic Functional Materials | Xia B.Y.,Shanghai JiaoTong University | Wang J.N.,Shanghai Key Laboratory for Metallic Functional Materials
Journal of Power Sources | Year: 2010

Carbon nanocages (CNCs) with a hollow structure and high degrees of graphitization and purity have wide applications. However, preparation of such material is still a great challenge. In this study, we report a general strategy for the preparation from iron/graphite core-shell nanoparticles. The core-shell nanoparticles are synthesized by the pyrolysis of acetylene with iron carbonyl. In order to remove the metallic core, rather than using the conventional acid oxidation, the nanoparticles are heat treated in the presence of iodine. It is found that the entrapped iron particles can be completely eliminated and hollow CNCs with good graphitization and high purity can be obtained. The purification process may involve the diffusion of iron atoms out from CNCs and their reaction with iodine molecules in the surrounding atmosphere. The reaction product FeI2 is soluble in ethanol and could thus be easily removed. As an example of a potential application, the CNCs are demonstrated to be a superb material for supporting the Pt catalyst used in low-temperature fuel cells. The present method could be applied to the production of graphitic carbon in large scale, and the resultant material could prove to be practically relevant for fuel cell and many other technologies. © 2009 Elsevier B.V. All rights reserved.

Wu Z.P.,Shanghai JiaoTong University | Xia B.Y.,Shanghai JiaoTong University | Wang X.X.,Shanghai Key Laboratory for Metallic Functional Materials | Wang J.N.,Shanghai Key Laboratory for Metallic Functional Materials
Journal of Power Sources | Year: 2010

Dispersion of double-walled carbon nanotubes (DWCNTs) in ethylene glycol (EG) medium by a simple ultrasonication method is investigated. Excellent dispersion of DWCNTs in EG without addition of a surfactant is found. Surface structure and crystallinity of the DWCNTs undergo little change. The dispersion state of DWCNTs is found to be very important for deposition of Pt nanoparticles on them. The Pt particles prepared in the homogenous dispersion system has a small size and uniform distribution. As a result, the electrochemical activity of the Pt catalyst is much higher than that prepared in the nondispersible system. In terms of the good dispersion in EG medium achieved by a simple method, the DWCNT solutions could also be widely used in energy, biology, medicine and other fields. © 2009 Elsevier B.V. All rights reserved.

Xu Q.F.,Shanghai JiaoTong University | Wang J.N.,Shanghai Key Laboratory for Metallic Functional Materials | Sanderson K.D.,Pilkington Group Ltd
ACS Nano | Year: 2010

Superhydrophobic, highly transparent, and stable organic-inorganic composite nanocoating is successfully prepared by a simple sol-gel dip-coating method. This method involves control of the aggregation of inorganic colloid particles by polymerization and ultrasonic vibration to create the desired micro/nanostructure in the coating. Superhydrophobicity and transparency of the coating can be controlled by adjusting the initial concentration of monomer and the size of aggregates in the sol-gel. Thus, superhydrophobicity and high transparency can be concurrently achieved in a single coating. The prepared coating also possesses good thermal stability. Its superhydrophobicity can be maintained from 20 to 90 °C. © 2010 American Chemical Society.

Ma J.,Tongji University | Ma J.,Shanghai JiaoTong University | Yu F.,Shanghai JiaoTong University | Wang J.N.,Shanghai Key Laboratory for Metallic Functional Materials
Journal of Materials Chemistry | Year: 2010

A simple freeze-smashing method is described to produce water-dispersible single-walled carbon nanotubes (SWCNTs). This is based on freezing SWCNTs in ice and then smashing it in a crusher. After the smashing process, SWCNTs are found to be dispersible in water without any addition of dispersant and destruction of the good graphitic structure. When such SWCNTs are used as a catalyst support for fuel cells, they show much better performance than the original SWCNTs, multi-walled carbon nanotubes and the commercial catalyst from Johnson Matthey Company as well. It is suggested that the present approach might be useful for preparation of water-dispersible single-walled carbon nanotubes in wide areas such as information technology, biomedicine, environmental and energy industries. © The Royal Society of Chemistry 2010.

Xia B.Y.,Shanghai JiaoTong University | Wang J.N.,East China University of Science and Technology | Teng S.J.,Shanghai JiaoTong University | Wang X.X.,Shanghai Key Laboratory for Metallic Functional Materials
Chemistry - A European Journal | Year: 2010

(Figure Presented) Graphitic carbon is the key: A Pt catalyst that is supported on carbon nanocages with a graphitic structure is found to exhibit not only a high catalytic activity, but also a superior thermal stability and electrochemical durability in harsh operating conditions when compared with a counterpart that is supported on conventional carbon black (see graphic). © 2010 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Wu Z.,Shanghai JiaoTong University | Xu Q.,Shanghai JiaoTong University | Wang J.,Shanghai Key Laboratory for Metallic Functional Materials | Ma J.,Shanghai JiaoTong University
Journal of Materials Science and Technology | Year: 2010

Double-walled carbon nanotube (DWCNT) macro-films with large areas, excellent flexibility and superhy-drophobicity are reported. The area of the macro-film is larger than 30 cm × 15 cm, and this large film can be bended, or folded without any damage, and even can be tailored freely. After a simple modification of perflu-oroalkysilane, the surface of the macro-film shows excellent superhydrophobicity with a water contact angle of 165.7±2 deg. and sliding angle lower than 3 deg., the prepared superhydrophobic films showing excellent antifouling, self-cleaning and water-repellent functions. The topographic roughness and perfluoroalkysilane modification are found to contribute to the observed superhydrophobicity. Considering the outstanding electronic, chemical and mechanical properties of DWCNTs, it is expected that this multifunctional DWCNT macro-film has potential applications in many fields. Copyright © 2010 by The Editorial Board of Journal of Materials Science & Technology. Published by Elsevier Limited. All rights reserved.

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