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Li F.J.,Nanyang Technological University | Li F.J.,Singapore Epson Industrial Pte Ltd | Zhang S.,Nanyang Technological University | Guo J.,Soochow University of China | Li B.,Control Iron and Steel Research Institute, China
Nanoscience and Nanotechnology Letters | Year: 2014

Silicon (Si) nanowires are important building blocks in the devices of photonics, quantum-dots, optoelectronics and energy. So far, however, the morphology is yet well studied. In this work, Si/Si-oxide nanowires were grown through thermal annealing of nickel (Ni) coated Si wafers. Side-by-side biaxial, smooth or sinusoidal triple-concentric, fishbone-profiled, Ni-nanosphere entrapped nanowires, and the transitional morphologies were observed co-existing with the most abundant coaxial ones. The relation between the nanowires and the seeding particles is carefully explored via transmission electron microscopy and selected area electron diffraction pattern. In conjunction with the scrutiny of the existing mechanisms, it is found that the morphology of the nanowires is controlled by the diameter, vibration, phase distribution, and the eutectic precipitation of the seeding Ni-Si-O droplets. A detailed growth mechanism is proposed. Copyright © 2014 American Scientific Publishers All rights reserved. Source


Wang Y.X.,Nanyang Technological University | Zhang S.,Nanyang Technological University | Lee J.-W.,University of Taipei | Lew W.S.,Nanyang Technological University | And 2 more authors.
Nanoscience and Nanotechnology Letters | Year: 2012

This paper describes how hard yet touch ceramic coating is achieved: hard and brittle nanocomposite layers (nanocrystalline CrAlN imbedded in amorphous SiNx or nc-CrAlN/a-SiNx ° are intimately combined with soft and tough CrAlN polycrystalline layers (pc-CrAlN) to build multilayer coatings of different period thickness with a constant total coating thickness of one micron. At the period thickness of 20 nm, an improved hardness of 33 GPa was achieved with a scratch toughness 5 times as much as that of the nanocomposite monolayer. At the period thickness of 40 nm, drastic scratch toughness was increased 7 folds at a slightly reduction of hardness (from 30 to 27.9 GPa). Copyright © 2012 American Scientific Publishers. Source


Wang Y.X.,Nanyang Technological University | Zhang S.,Nanyang Technological University | Lee J.-W.,University of Taipei | Lew W.S.,Nanyang Technological University | And 2 more authors.
Surface and Coatings Technology | Year: 2013

A set of CrAlSiN coatings was synthesized in homogenous and graded composition via magnetron sputtering in mixed Ar and N2 ambient. The microstructures are investigated using glancing angle X-ray diffractometry, field emission scanning electron microscopy and transmission electron microscopy. With compositional grading, CrAlSiN coatings exhibit much improved scratch adhesion strength and better crack propagation resistance at a little expense of hardness. © 2012 Elsevier B.V. Source


Li F.J.,Nanyang Technological University | Li F.J.,Singapore Epson Industrial Pte Ltd | Zhang S.,Nanyang Technological University | Lee J.-W.,Ming Chi University of Technology | Zhao D.,Control Iron and Steel Research Institute, China
Nanoscience and Nanotechnology Letters | Year: 2014

Metal catalyst sometimes is entrapped in crystalline silicon (Si)/amorphous Si-oxide nanowires. Till now, however, the entrapping mechanism is still unclear. In this work, Si/Si-oxide nanowires were grown via thermal annealing of a Si wafer coated with a 10 nm thick layer of gold (Au) which acts as catalyst. Au nanospheres or elongated core are occasionally entrapped in the nanowires. Transmission electron microscopy, energy dispersive X-ray spectroscopy and selected area electron diffraction were employed to study the structure of the grown nanowires and their relationship with the seeding Au particles. The entrapment of the Au catalyst is attributed to the eutectic precipitation of Au and Si in the Si-supersaturated Au-Si-O droplet as the temperature is below the eutectic point. A new mechanism elucidates the entrapping process. Copyright © 2014 American Scientific Publishers Source


Cai Y.,Nanyang Technological University | Zhang S.,Nanyang Technological University | Zeng X.,Singapore Institute of Manufacturing Technology | Sun D.,Singapore Epson Industrial Pte Ltd
Journal of Materials Science: Materials in Medicine | Year: 2011

Dissolution resistance and adhesion strength are two main concerns for long-term stability of surface coated metal implants. In this study, fluorine ions are incorporated into magnesium-containing hydroxyapatite coatings (MgF y HA) via sol-gel method to improve the long-term stability of the implants. Surface and interface are studied in terms of phases, depth profiling and chemical bonds by grazing incidence X-ray diffraction, glow discharge optical emission spectroscopy and X-ray photoelectron spectroscopy. The long-term stability is evaluated by dissolution and pull-off test. The results show that fluorine promotes the incorporation of magnesium in HA lattice. The elemental interdiffusion and chemical bonding take place at the coating/substrate interface. Both the dissolution resistance and the adhesion strength are enhanced by fluorine incorporation, thus the long-term stability of the implant is improved. © 2011 Springer Science+Business Media, LLC. Source

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