Nano Engineering and Materials Technologies II

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Authors: Eksuree Saksornchai, Jutarat Kavinchan
Abstract: Cubic phase of silver antimony sulfide (AgSbS2) nanostructures were successfully synthesized from silver nitrate (AgNO3), antimony acetate (CH3CO2)3Sb, and sodiumthiosulphate pentahydrate (Na2S2O3.5H2O) in propylene glycol (PG) without using any surfactants or splitting agents by a facile wet chemical route at 160 OC for 30 min. The XRD, SEM and TEM reveal AgSbS2 nanostructures forming the clusters. Due to the UV-visible absorption shows its direct band gap, is 1.80 eV, AgSbS2 is found to be the excellent material for the solar energy converters. And the possible formation of AgSbS2 nanostructured cluster was also discussed.
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Authors: Serap Senturk Dalgic
Abstract: The morphological and structural transitions in CdSe hollow nanoparticles (hNPs) with zinc blende structure have studied by molecular dynamics (MD) simulation method under heating. The seven samples of CdSe-hNPs are constructed with different thicknesses from the solid NPs at 10nm and 15nm sizes. Morphological changes in CdSe-hNPs have presented by describing the first stage melting in hollow semiconductor NPs. The thermal effect on the atomic arrangement has also examined by the cubic zinc blende-to-wurtzite transformation occurred during the melting in hNPs. MD results show that the inner shells of those with thin walls have begun to melt at lower temperatures due to the thickness of the NPs. The first stage melting, which resulted in the filling of the void within the particle, takes place almost at the same temperature for hNPs with the thick wall thickness. Then, the melting of the particles is completed at higher temperatures. The cubic diamond structure disappears with the collapse of the inner cavity, and the hcp structure begins to appear at later temperatures.
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Authors: Sena Güler Özkapı, Barış Özkapı, Seyfettin Dalgıç
Abstract: In this work, we have investigated electronic structures of pure and doped (with Cr and Mn atoms, separately) BN nanowires along [001] direction with zinc blende phase by means of density functional theory calculations. Our results show that the substitution doping of nanowires by Cr and Mn atoms decrases the band gaps of the all BN nanowires. Also, spin polarized calculations exhibit that the density of states (DOS) for spin up and spin down electrons are antisymmetric structure for both Cr and Mn doped BN nanowires. All these show that doped BN nanowire systems have potential applications in electronics and spintronics.
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Authors: Jan Rommel C. Mateo, Annalou L. Salut, Menandro C. Marquez
Abstract: This paper aims to find various ways to maximize the potential of nickel oxide (NiO) nanostructures which is produced via simple route method. The morphology of the NiO nanostructures was modified by adding surfactants such as Tween 80, SDS and CTAB. The effect on the morphology and optical property of the type and amount of the surfactant used were determined. The synthesized nanostructures were compared in terms of its shape, uniformity and size. SEM images revealed that the morphologies were altered by simply adding and adjusting the amount of surfactant such as CTAB, Tween 80 and SDS on to the solution. Nanocubic, nanospheres and nanoblades were produced using CTAB, Tween 80 and SDS respectively. XRD confirmed the presence of oxide and hdroxides of nickel on the produced product. The effects on the morphology of the NiO upon adding surfactant could give a good impact in different applications such as electrode, catalysts and gas sensors.
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Authors: Xing Hui Hou, Jing Kun Yu
Abstract: The Al2O3 ceramic-lined composite steel pipes were produced by the SHS gravitational separation process (SHS-GS process) from Al, Fe2O3 and Cr2O3 as the raw materials within different reaction systems. The phase, composition, micro-structure and properties of ceramic coatings were investigated to discuss the strengthening mechanism of the composite steel pipe. The results showed that the phase composition of Al-Fe2O3-Cr2O3 reaction system could be Al2O3 and Fe-Cr alloy compared with the Al2O3-Fe-FeAl2O4 phases of Al-Fe2O3 reaction system, which led to the increase of strength and hardness of ceramic coating. Because the Fe-Cr alloy was formed instead of Fe element, and the addition of Cr2O3 reduced the production of erodible FeAl2O4. The transition structure consisted of ceramic coating-transition layer-steel pipe was formed, and in its direction the Al and O element contents decreased, the metallic Fe and Cr increased. Therefore, the transitional changes of all the element contents could decrease the stress difference between the layers, and increase the bonding strength of the composite steel pipe.
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Authors: Igor Shishkovsky, Vladimir Scherbakov
Abstract: The surface improvement of light-weighted metals by adding of hard ceramic particles into a metal matrix has promised to be perspectives for aerospace industry. In the present study, titanium carbides of nano size were incorporated to the titanium substrate by a selective laser melting (SLM) of Ti + (10, 15 and 20 wt.%) TiC powder mixtures via an Ytterbium fiber laser with 1.075 mm wavelength. Optimal regimes of the 3D laser additive process were determined. We studied how the interfacial properties would change due to the difference in composition in case of the titanium matrix nano composites (TMNC) reinforced with carbides. The phase analysis of the fabricated TMNC showed that the initial carbide particles are dissolved after the remelting with different velocities. A particular attention was paid to the carbide dilution and secondary carbides formation mechanisms when the TiC was mixed with titanium. Various parameters, such as microstructure, phase constitution and mechanical properties of the gradient TMNCs were investigated by means of OM, SEM, XRD and microhardness measurement. It was shown that the microstructure had two types of heterogeneity: the TiC particles at the interlayer interfaces and element chemical segregation on the boundaries of the tracks.
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Authors: Beh Hoe Guan, Muhammad Hanif bin Zahari, Kean Chuan Lee
Abstract: Spinel ferrite with the chemical formula of Mn0.5Zn0.5LaxFe2-xO4 (x = 0.02, 0.04, 0.06, 0.08, 0.10) were prepared by a sol-gel auto-combustion method. The effect of the rare-earth substitution on the microstructural properties of the synthesized powders were investigated through X-ray diffraction (XRD) and field-emission scanning electron microscopy (FESEM), while for the magnetic properties, vibrating sample magnetometer (VSM) measurements were made. XRD patterns revealed characteristic peaks corresponding to spinel Mn-Zn ferrite structures with accompanying secondary phases, such as Fe2O3 and LaFeO3. The initial addition of La3+ into the spinel ferrite system resulted in an initial spike of the lattice parameter and crystallite size before proceeding to decrease as the rare-earth content continues to decrease. FESEM micrographs reveals agglomerated particles with considerable grain size distribution. The magnetic properties, especially the saturation magnetization, Ms, was found to decrease with each increase in La3+ substitution. The research findings revealed the critical influence of the La3+ substitution towards the overall structural and magnetic properties of the Mn-Zn ferrite samples.
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Authors: John Lemuel G. Untalasco, Abdul Rahman Mariscal, Menandro C. Marquez
Abstract: The morphology of cobalt oxide / cobaltous oxide (Co3O4) nanostructures was controlled using different seed layer concentrations and deposition time. Co3O4 nanostructures were deposited on ITO glass synthesized using two step solution route. The morphological evolution of the Co3O4 nanostructures has been investigated using scanning electron microscopy (SEM). This has been correlated to the electrochemical activity of the material using cyclic voltammetry (CV) in a potassium hydroxide (KOH) and phosphoric acid (H3PO4) media. Other characterization technique such as x-ray diffraction analysis (XRD) was used to verify the crystal structures of the Co3O4 nanostructures. The Co3O4 nanostructures revealed pronounced redox peaks in a 1M KOH electrolyte which proved its high electrochemical activity. Also the redox peaks increases with the increase in scan rate which demonstrated good reversibility of a fast charge-discharge response. Varying CV curves have been observed in a 1M H3PO4 electrolyte which denotes the instability of Co3O4. The change in the morphology of Co3O4 certainly affects the electrochemical property of the Co3O4. This leads to an advance study for its promising electrochemical applications for a cleaner energy.
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Authors: Wei Hu, Cheng Li, Shun Li Zheng, Teng Fei Xiang, Pan Jin Liu, Shi Bing Ding
Abstract: A nickel coating on the surface of alumina particles, used as a reinforcement in metal-ceramic composite materials, its dielectric and electromagnetic properties have important application value. In this paper, nickel was deposited on alumina powder surface by the way of hydrothermal and sintering. The results showed that the nickel powders were fcc structure. The size of the crystal grains ranged from 10 nm-50 nm. The electro-magnetic characteristics were measured by HP 8722ES microwave net work analyzer in the band of 2-18 GHz. It was showed that both the Ni-Al203 and Co-Al203 nanopowders had low dielectric constant, low electromagnetic and good properties in microwave absorption.
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Authors: Menandro C. Marquez
Abstract: Zinc oxide (ZnO) nanorods were grown on the pre-seeded substrate using a facile, solution route technique. The multilayer self-assembly of polyaniline (PAni) and tetrasulphonated phthalocyanine (TSCuPc) on ZnO nanorods was monitored by FTIR, UV-Vis SEM and XRD. Infrared spectrum of the assembled layer showed peaks centered at 1589cm-1and 1504 cm-1, confirmed the presence of quinoid and benzenoid structures of PAni, while peaks centered at ~1165cm-1and ~775cm-1 provided evidence for the presence of TSCuPc species. Absorption spectra of the assembled layer show broadened peaks at ~600nm and ~700nm affirmed the presence of PAni and TSCuPc molecules. A linear increase in the absorbance level at these wavelengths was also observed upon increasing the number of bilayers. The surface modification of the ZnO nanorods after self-assembly was confirmed through SEM. The edges of the ZnO nanorods was observed to change from sharp to dull upon employing layer by layer deposition of PAni and TSCuPc. XRD pattern of the assembled layer showed broadened peaks at low 2Θvalues associated to the amorphous nature of the emeraldine base of PAni. Even so, the diffraction peaks in XRD patterns of ZnO nanorods and ZnO/(TSCuPc-PAni) multilayer have been indexed as hexagonally wurtzite structure. The multilayer deposition of PAni and TSCuPc on the surface of ZnO as monitored by UV-Vis spectroscopy and confirmed by FTIR, XRD, and SEM provides a new way of anchoring dye molecules without carboxylic moieties on the surface of metal oxides
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