Advanced Materials Research Vols. 622-623

Abstract: The strongly geometrical shape, high aspect ratios, and nanoscale cross-section of nanowires is expected to affect optical properties through confinement effects. Herein we have investigated optical properties of Cu nanowires with studies of second harmonic generation (SHG) spectra. These optical properties of Cu nanowires will be one of the most important issues when considering the types of materials used in current applications and development of new applications.

Abstract: Hydroxyl modified multi-walled carbon nanotubes (OH-MWCNT)/ polyurethane (PU) and graphene nanosheets (GNS)/PU composites were prepared by dispersing the OH-MWCNT and GNS at different wt % in to the PU matrix. It was found that the electrical percolation threshold of the GNS/PU composite is much higher compared to that of OH-MWCNT/PU and also the electrical conductivity of the OH-MWCNT/PU composite is higher than the GNS/PU composite in the same level of filler content. This may be due to the two composites having different electrical conduction mechanisms: The OH-MWCNT/PU composite represents a three dimensional conduction system while, the GNS/PU composite represents a two dimensional conduction system. The improvement in the electrical conductivity with the incorporation of GNS as a filler in the composite is far lower than what theoretically expected. It is also observed that the tensile strength of the OH-MWCNT/PU composite is higher compared to the GNS/PU in the same level filler content.

Abstract: Industrial application of sliding components required to improve the tribological properties by increasing the surface hardness, friction and wear resistance. Modern modification of surface layers for friction applications combines surface texturing and filling of textured layers by wear resistant coatings of various compositions to improve its functional aspect and enhanced service life. Texturing of contact surfaces has a remarkable influence on their tribological properties, especially in the effect of wear and friction. This work proposes the coating of nano sized Titanium Aluminum Nitride (TiAlN) by Magnetron Sputtering-Physical Vapour Deposition (PVD) on the Titanium alloy (6Al-4V) substrate and study the performance of the coated surfaces by pin on disc tribometer. Two kinds of substrates were prepared one is the lapped surface and the other one is the textured surface by Laser beam machining. The Tribological performance of the wear resistant coatings on lapped and textured surfaces was experimentally investigated under various normal load conditions and the results were compared. Critical parameters such as friction coefficient, wear rate, wear volume, wear morphology and micro wear mechanism were investigated in this work. The coating surfaces and wear scars were evaluated by scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDAX). The results showed that the TiAlN coating on textured surfaces exhibited lower friction coefficient and wear rate than the TiAlN coating on lapped surfaces under same testing conditions.

Abstract: Rutile nano-TiO₂ was modified with surfactant to improve its dispersion in organic solvents. The modified nano- TiO2 was used in furniture paint, anticorrosive paint and automotive paint. The ultraviolet resistance of the paint was knowed by detecting the color difference and gloss loss rate of the paint. The results show that: the nano-TiO₂ which is modified with B/C surfactant has excellent dispersion in paint. And it shows excellent ultravioleting performance in paint applications. The paint color and gloss can be maintained for a longer time.

Abstract: Experiments are performed to investigate the single-phase flow heat transfer augmentation of MWCNT/HT-B oil in both smooth and microfinned helical tubes with constant wall temperature. The tests in laminar regime were carried out in helical tubes with three curvature ratios of 2R/d=25, 30 and 35. Flow Reynolds number varied from 170 to 1800 resulting in laminar flow regime. The effect of some parameters such as the nanoparticles concentration, the dimensionless curvature radius (2R/d) and the Reynolds number on heat transfer was investigated for the laminar flow regime. The weight fraction of nanoparticles in base fluid was less than 0.4%. within the applied range of Reynolds number; results indicated that for smooth helical tube the addition of nanoparticles to the base fluid enhanced heat transfer remarkably. However, compared to the smooth helical tube, the average heat transfer augmentation ratio due to nanoparticle addition for finned tube was small, about 17%. Also, by increasing the weight fraction of nanoparticles in microfinned helical tubes, no substantial changes were observed in the rate of heat transfer enhancement. For the pressure drop, the results show that the pressure drop of nanofluids was slightly higher than the base fluid and increase as the volume concentrations go up.

Abstract: Normal grain growth of silver thin film predominates above the critical transition temperature below which bimodal grain growth predominates. In this experiment silver Nano layers were prepared by spin coating on glass substrate and which were annealed at different temperature. The lowest attainable resistance was 1.23 Ohm/sq. The woulf plot of fcc silver suggests that during growth (111) family plane predominated on surface of every grain and that was true according to SEM figure. This is the reason for low resistivity of silver thin film. Not only on surface but also this stable (111) plane was present on grain boundary as singular interface. However, ADF Simulation has been done to construct 40 nm silver nano particle and to construct band structure of silver. The valance band and conduction band overlap shows the metallic characteristic property of silver.

Abstract: An experimental investigation has been carried out to study the heat transfer and pressure drop characteristics of MWCNT-Base oil nano-fluid flow inside horizontal rectangular channels under constant wall temperature. The temperature of the tube wall was kept constant at around 95 °C to have isothermal boundary condition. The required data were acquired for laminar fully developed flow inside round and rectangular channels. The effect of different parameters such as mass velocity, aspect ratio of rectangular channels and nano-particles concentration on heat transfer coefficient and pressure drop of the flow is studied. Observations show that the heat transfer performance is improved as the aspect ratio is increased. Also, increasing the aspect ratio will result in the pressure drop increasing. In addition, the heat transfer coefficient as well as pressure drop is increased by using nano-fluid instead of base fluid. Furthermore, the performance evaluation of the two enhanced heat transfer techniques studied in this investigation showed that applying rectangular channels instead of the round tube is a more effective way to enhance the convective heat transfer compared to the second method which is using nano-fluids instead of the base fluid.

Abstract: Combining the versatility of electrospinning and chemical etching technique enables selective controlled synthesis of CeO₂ nanostructure. The as-prepared CeO₂ material exhibits one- or two- dimensional microstructure based on different processing conditions. XRD and EDX characterization demonstrated that SrFeO₃ crystal particles as template can be introduced into the bulk of CeO₂ nanofiber using co-electrospinning to optimize related nanostructures. SEM images showed that the electrospun nanofiber of ceria can be transformed into nanoparticles, nanofibers or porous films according to treatment conditions.

Abstract: Hydrogen production from NaBH4 hydrolysis is very important for environment-friendly fuel cells. Here Ni/CNTs nanocomposites were prepared by microwave-assisted method and used as the catalyst for catalytic hydrolysis of NaBH₄. XRD and SEM characterization showed that uniform Ni/CNTs nanocomposites can be obtained through microwave heating and solvent optimization. Ni/CNTs nanocomposites exhibit excellent catalytic activity in the hydrolysis of NaBH₄, i.e., the average hydrogen generation rate at 25°C is 840ml.min-1.g-1 for the CNTs-supported Ni/CNTs, while the hydrogen generation rate of 86ml.min^-1.g^-1 for unsupported Ni catalyst. Compared with the unsupported Ni catalyst, Ni/CNTs nanocomposites presented higher catalytic activity for hydrolysis of aqueous NaBH₄ solution.

Abstract: Photodynamic therapy (PDT) is an effective, noninvasive and nontoxic therapeutics for cancer and some other diseases. It is becoming a alternative of traditional therapeutics for cancers. But the efficacy of PDT was restricted by insufficient selectivity and low solubility. In this study, novel multifunctional silica-based magnetic nanoparticles were prepared as targeting drug delivery system to achieve higher specificity and better solubility. Haematoporphyrin derivative (photosan) was used as photosensitizer. Magnetite nanoparticles (Fe3O4) and photosan were incorporated in silica nanoparticles by microemulsion and sol-gel methods. The prepared nanoparticles were characterized by X-ray diffraction, and transmission electron microscopy. The nanoparticles possessed good biocompatibility and could cause remarkable photodynamic anti-tumor effects. These suggested that photosan-Fe3O4 nanoparticles had great potential as effective drug delivery system in targeting photodynamic therapy.