Science and Technology of Nanomaterials

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Authors: Rengaswamy Jayaganthan, Gan Moog Chow
Abstract: An analysis of surface segregation of Au-Ti alloy nanoparticle (atomic ratio 1:1) is carried out using Monte Carlo simulation with the energetics described by Bozzolo-Ferrante-Smith method. The surface compositions of Au in Au-Ti nanoparticles are calculated based on the simulation that takes into account the size effect. The segregated surface compositions of Au in the Au-Ti binary alloy single-crystal nanoparticles (with particle diameter of 10-100 nm) are observed to be larger than that of the corresponding bulk single crystal (with the particle diameter > 100 nm). The details of Monte Carlo simulation and the calculated surface compositions due to segregation are discussed.
Authors: S.W. Du, R.V. Ramanujan
Abstract: The Herzer model suggests that superior magnetic properties can be observed in magnetic alloys provided a suitable microstructure consisting of soft magnetic nanometre size precipitates separated by nanometre size distances is obtained. In order to explore new magnetic alloy compositions which can satisfy the Herzer model, we studied selected alloys in which we wished to obtain suitable microstructures, one such alloy has the composition Fe40Ni38B18Mo4. This alloy is amorphous as received, the heat treatment schedule required to obtain nanoprecipitates was designed based on DSC, resistivity and x-ray results. Heat treatment at temperatures between 420 0C and 500 0C and different heat times was carried out on the amorphous ribbon. Transmission Electron Microscopy (TEM) results of the early stage of crystallization behavior showed that soft magnetic precipitates of nano-size were indeed observed within the amorphous matrix. The crystal structure, composition analysis and thermal stability of the precipitates were studied by XRD, EDS and TEM. These results will be presented and the implication of these results to the production of new soft magnetic alloys will be emphasized.
Authors: J.H. Hsieh, Can Hua Li, C.M. Wang, Y.C. Liu, Z.Z. Tang
Abstract: Four alloy thin films were deposited on Si(100) by co-sputtering of various metals to investigate the formation of near-amorphous structure which may lead to featureless surface morphology and boundary-free structure. These thin films, Nb-Cr, Ta-Cr, Ti-Nb, and Zr-Cr, were examined using XRD SEM, and TEM. It is found that the forming ranges of near-amorphous thin films by co-sputtering are related to the difference in atomic size of the paired metals as well as their heat of mixing. Accordingly, Zr-Cr has the widest concentration range to form the near-amorphous structure. The addition of nitrogen during deposition can further enhance amorphization and reduce the surface roughness, until nitride phases are formed.
Authors: Soo Jin Park, Byung Joo Kim
Abstract: In this work, the catalytic reduction of NO over activated carbon fibers (ACFs)/Ag prepared by nanoscaled Ag electroplating has been studied. It is observed that silver content on ACF surfaces increases with increasing the plating time. However, a decrease of adsorption properties, including BET’s specific surface areas and total pore volumes, in increasing the plating time is observed within the range of well-developed micropore structures. As the experimental results, the net heat of adsorption of the ACFs/Ag samples is largely influenced on the amount of silver metal, and the catalytic ability for NO removal over ACFs/Ag samples is improved in the presence of silver on the ACFs. However, the adsorption properties of the excessively silver loaded samples are significantly reduced, resulting in the decrease of the removal efficiency. Therefore, the NO removal is largely depended on silver content on ACFs, together with the results of adsorption properties of the ACFs.
Authors: K. Moto, Stan Veprek
Abstract: As alternative to TiN based material, nc-(Ti1-xAlx)N and h-AlN were deposited on steel substrate using plasma CVD technique and characterized by means of XRD, XPS, EDX. The effect of Al substitution can be shown by the decrease of the lattice parameters of TiN as the fraction of Al increases. As the fraction of Al further increases up to 0.8, the hexagonal AlN phase precipitates. The hardness of these coating are around 30 GPa higher than that prepared by other method.
Authors: Zhou Wei, Oh Joo Tien, Hng Huey Hoon
Abstract: Nickel-based alloy is an important class of magnetic materials that have high permeability, large saturation and remnant magnetization, low hysteresis loss and low coercivity. These properties vary with the grain size, shape, magnetic domains and orientation. As the grain approaches nanoscale, an important averaging of the magnetocrystalline anisotropy over many grains coupled within an exchange length results in a significant increase of the magnetic softness and the effect of the internal thermal energy becomes more pronounced. The crystalline Ni-Fe-Cu-Cr system processed by high-energy ball milling (HEBM) and metal injection moulding (MIM)were investigated using TEM and SEM. The average grain size of the HEBM samples was found to be in the order of several tens of nanometers while those of the MIM are in the order of tens of micrometers. The magnetic properties of the HEBM and MIM samples were also investigated. The magnetic properties of the HEBM samples are significantly ‘softer’ magnetically when compared to the MIM samples. The coercivity (Hc) of MIM sample is 37.5 Oe while the HEBM sample is 17.5 Oe. More remarkably, the initial permeability (µi) of the HEBM sample is an order higher than the MIM sample 2184 and 225 Oe respectively.
Authors: Jittiporn Kruenate, R. Tongpool, P. Kongrat
Abstract: EVA/tetraethylorthosilane(silane) nanocomposites were prepared. Rheological properties were studied in both dynamic and steady modes at 150oC. The rheological properties of the nanocomposites are strongly affected by silane dispersed in EVA matrix. As silane content incresed, the polymer strength increased due to interconnections between filler clusters which can be disrupted by high shear rate (in steady mode). The degree of silane dispersion in the EVA matrix decreased with increasing silane content, leading to a “pseudo-solid-like” behaviour. The samples showed viscous and elastic behaviour at low- and high-shear rate regions, respectively. The nanocomposite films were almost as clear as EVA film.
Authors: Matthew Oaten, Namita Roy Choudhury
Abstract: The potential of cyclic silsesquioxanes as flexible coatings has been explored in this work for corrosion protection of metal. A polyurethane coating containing an inorganic polyhedral oligomeric silsesquioxane (POSS) was synthesized and characterized by means of photo-acoustic infrared spectroscopy, X-ray photoelectron spectroscopy (XPS), contact angle and modulated differential scanning calorimetry (MDSC). The coating has been applied to clean steel substrates via dip and spin coating. The POSS based hybrid coating is found to be uniform, dense and essentially defect free. XPS shows that the coating forms a lamellar layered structure on the substrate.
Authors: G.B. Ma, Jian Min Zhu, Nai Ben Ming
Abstract: Chestnut-bur-like rutile titania assemblies are successfully synthesized by a sonochemical method. Scanning electron microscopy and transmission electron microscopy analyses reveal that the assemblies are formed by radial coagulation of rutile acicular nanocrystals. Effects of experimental conditions on the phase and structure of the products are also presented.
Authors: Z.G. Liu, L. Lu, M.O. Lai
Abstract: Formation of partial nanocrystal and amorphous tungsten alloys was synthesized via crystallization of a completely amorphized tungsten alloy synthesized by mechanical alloying. Structural characterization shows formation of amorphous structure from mechanical alloying of a mixture of elemental tungsten and iron powders after about 150 hours. Partial nanocrystalline phases within the amorphous matrix were formed through annealing the amorphous tungsten alloy at 1075°C.

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