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Deng J.,Taiyuan University of Technology | Kang L.,Taiyuan University of Technology | Bai G.,China Institute of Technology | Li Y.,Taiyuan University of Technology | And 6 more authors.
Electrochimica Acta | Year: 2014

Co3O4 and Co3O4/CoO nanoparticles have been synthesized by a one-step solution combustion process by adjusting the molar ratio of citric acid (fuel) and Co(NO3) 2·6H2O (oxidizer). The effects of citric acid/Co(NO3)2·6H2O molar ratios on phase composition and morphology of products were investigated by XRD and SEM. With the increase of the fuel dosage, the products transformed from granular aggregates of cubic Co3O4 into a mixture of cubic Co 3O4 and tetragonal CoO with fluffy sheet morphologies. Electrochemical measurements indicated that the products (Co3O 4) showed a capacitance up to 179.7 F·g-1 (at 0.2 A·g-1) when the citric acid/Co(NO3) 2·6H2O molar ratio was 7/27. Significantly, the capacitance could be further improved by 102% (362.8 F·g-1 at 0.2 A·g-1) after annealing at 350 °C for 3 h under nitrogen atmosphere. This annealed sample also demonstrated decent rate performance (285.7 F·g-1 at 4 A·g-1) and cycling stability (73.5% retention after 1000 cycles). The current study suggests that this process has promise in large-scale production of electrode materials for supercapacitors. © 2014 Elsevier Ltd. Source


Zhao C.,University of Hertfordshire | Chen Y.K.,University of Hertfordshire | Chen Y.K.,Key Laboratory of Interface Science and Engineering in Advanced Materials | Jiao Y.,University of Hertfordshire | And 2 more authors.
Tribology International | Year: 2014

This paper investigates the effects of surface modification of zinc borate ultrafine powders (ZB UFPs) on their tribological properties as lubricant additives in liquid paraffin (LP). ZB UFPs were successfully modified by hexadecyltrimethoxysilane (HDTMOS) and oleic acid (OA). It is evident that HDTMOS modified zinc borate ultrafine powder (HDTMOS-ZB UFP) delivered a small conglomerate size, good stability in the organic solvent and sound anti-wear property. It has been observed that a continuous and tenacious tribo-film on the worn surface generated from HDTMOS modified ZB UFP as a lubricant additive in LP plays an important role in the outstanding anti-wear property. It is suggested that HDTMOS modified ZB UFP as a lubricant additive in LP has a great potential. © 2013 Elsevier Ltd. All rights reserved. Source


Kang L.,Taiyuan University of Technology | Deng J.,Taiyuan University of Technology | Cui M.,Taiyuan University of Technology | Zhang X.,Auburn University | And 5 more authors.
Journal of Power Sources | Year: 2014

With Co(NO3)2·6H2O (oxidizer and Co source), Ni(NO3)2·6H2O (oxidizer and Ni source) and citric acid (fuel) as starting materials, cobalt-nickel oxides/C/Ni ternary nanocomposites have been synthesized by a scalable, one-step solution combustion process at only 300 °C within 30 min in air. In these composites, the metallic nickel and amorphous carbon (conductive phases) were in situ formed by the reduction of Ni2+ and carbonization of the excess citric acid during combustion, respectively. Experimental results indicated that the fuel:oxidant and Co:Ni molar ratios in precursor solution showed strong influences on the phase composition, morphology and electrochemical performance of products. With the increase of the fuel dosage, the products transformed from well-crystallized cubic NiO/Ni to Ni (nickel-related phases), then to relatively amorphous Ni/NiO and finally NiO. Electrochemical tests indicated that the optimized product showed a high specific capacitance of 446 F g-1 at 1 A g-1 (or 280 F g-1 at 10 A g-1) with a Co:Ni:C6H8O7 molar ratio of 4:5:86/9. Significantly, besides its mild experimental conditions, the method could be used to prepare cobalt-nickel oxides/C/Ni/CNTs quarternary nanocomposites by simply adding acid-treated CNTs into precursor combustion solution. Thanks to the high electrical conduction of CNTs, the specific capacitance could be further improved up to 579 F g-1 at 1 A g-1, or 350 F g-1 at 10 A g-1. © 2014 Elsevier B.V. Source


Dong Q.,Key Laboratory of Interface Science and Engineering in Advanced Materials | Dong Q.,Taiyuan University of Technology | Dong Q.,Hong Kong Baptist University | Li G.,University of Hong Kong | And 7 more authors.
Advanced Functional Materials | Year: 2014

Hard ferromagnetic (L10 phase) FePt alloy nanoparticles (NPs) with extremely high magnetocrystalline anisotropy are considered to be one of the most promising candidates for the next generation of ultrahigh-density data storage system. The question of how to generate ordered patterns of L1 0-FePt NPs and how to transform the technology for practical applications represents a key current challenge. Here the direct synthesis of L10 phase FePt NPs by pyrolysis of Fe-containing and Pt-containing metallopolymer blend without post-annealing treatment is reported. Rapid single-step fabrication of large-area nanodot arrays (periodicity of 500 nm) of L10-ordered FePt NPs can also be achieved by employing the metallopolymer blend, which possesses excellent solubility in most organic solvents and good solution processability, as the precursor through nanoimprint lithography (NIL). Magnetic force microscopy (MFM) imaging of the nanodot pattern indicates that the patterned L10 phase FePt NPs are capable of exhibiting decent magnetic response, which suggests a great potential to be utilized directly in the fabrication of bit patterned media (BPM) for the next generation of magnetic recording technology. Rapid single-step fabrication of large-area nanodot arrays of L10-FePt nanoparticles (NPs) are achieved by employing a metallopolymer blend of individual Fe- and Pt-containing homopolymers as the precursor through nanoimprint lithography. Imaging of the nanodot pattern indicates that the patterned NPs exhibit a decent magnetic response, which suggests potential to be utilized directly in the fabrication of bit-patterned media for the next generation of magnetic recording technology. © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim. Source


Guo X.,Taiyuan University of Technology | Yang Y.,Key Laboratory of Interface Science and Engineering in Advanced Materials | Yang Y.,Taiyuan University of Technology | Zhao X.,Key Laboratory of Interface Science and Engineering in Advanced Materials | And 2 more authors.
Applied Surface Science | Year: 2012

Polymer/carbon spheres (CSs) composite materials, in which polymer was used as continuous phase and CSs as dispersed phase, were synthesized by in situ bulk polymerization. In order to improve CSs dispersibility in polymer matrix and compatibility with polymer matrix, the functional double bonds were introduced onto the surface of CSs by covalent and non-covalent method. Covalent functionalization was accompolished through mixed acid oxidation and subsequent reaction with acryloyl chloride. Field-emission scanning electron microscopy, Fourier-transform Infrared spectrometry and thermogravimetry were used to characterize the morphology, structure and effect of functionalization of CSs. Vinyl-functionalized CSs by acryloyl chloride were well dispersed in organic solvents, such as DMF, acetone and chloroform. Non-covalent functionalization by surfactant was accompolished by electrostatic interaction. Covalent and non-covalent functionalization enabled CSs to be homogeneously dispersed in poly(methyl methacrylate) (PMMA) matrix with good compatibility. These studies lay the foundation of preparing the non-close packed three-dimensional carbon-based photonic crystals. © 2012 Elsevier B.V. All rights reserved. Source

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