Advanced Materials Research Vol. 832

Abstract: Nanofluid is the suspension of nanoparticle in a base fluid. In this paper, the heat transfer performances of the nanofluids flow through a circular shaped copper minichannel heat sink are discussed analytically. Al₂O₃-water, CuO-water, Cu-water and Ag-water nanofluids were used in this analysis to make comparative study of their thermal performances. The hydraulic diameter of the minichannel is 500 μm and total block dimension is 50mm× 50mm× 4mm. The analysis is done at different volume fractions of the nanoparticle ranging from 0.5 vol.% to 4 vol.%. The results showed that the heat transfer performance increases significantly by the increasing of volume fraction of nanoparticle. Ag-water nanofluid shows the highest performance compared to the other nanofluids. So, this nanofluid can be recommended as a coolant flow through a circular minichannel for cooling of electronic heat sink.

Abstract: Heterostructures consisting of ZnO and diamond appear to have an elusive nature. A rectifying behaviour was previously observed only for heterojunctions with very lightly doped p-type diamond using residual boron gas during the chemical vapour deposition process or type IIb diamond. Other studies, however, claimed to obtain a rectifying behaviour for heterojunctions with p-type diamond with higher carrier densities between 10¹⁸ 10¹⁹ cm^-3. In this work we investigate the behaviour of n-type ZnO on heavily boron-doped p-type diamond. This heterostructure that is sensitive to UV light has been fabricated using ZnO nanorods grown on heavily boron-doped chemical vapour deposition diamond substrates. The I - V measurements show a rectifying characteristic. The threshold voltages under dark and UV conditions are 3.66 and 2.52 V, respectively. The UV illumination also results in an increased current flow. The electrical behaviour due to the UV illumination will be discussed.

Abstract: Composites of polystrene and multiwalled carbon nanotubes were prepared using the solution blending method. Results on the electrical conductivity and alcohol vapor sensing will be presented. Field Emission Scanning Electron Microscopy was used to investigate the structure MWCNT/PS composites. The optical characterization was investigated by Fourier Transform-Infrared Spectroscopy. Thermogravimetric Analysis was used to determine the composition of materials and to predict their thermal stability at temperatures up to 6000°C.

Abstract: Hybrid film of MWCNT/ZnO was prepared on the silver electrodes using electrophoresis deposition. A constant dc voltage of about 20V was applied to the electrodes and the MWCNT/ZnO was deposited on the surface of the anode electrode as a result. Field Emission Scanning Electron Microscopy was used to investigate the structure MWCNT/ZnO composite. The optical characterization was investigated by Raman Spectroscopy. The MWCNT film exhibits excellent field electron emission properties with high emission current densities, low threshold electric fields and good field emission stability.

Abstract: The crystalline calcium tetraborate (CaB₄O₇) nanoparticles were synthesized using a combination of facile co-precipitation and thermal treatment. The synthesized phosphor nanoparticles were found to possess a monoclinic nanostructure of particle size of about 8 nm. The thermoluminescence (TL) glow curve of the nanoparticles shows a single peak centred at about 150°C. The TL nanophosphor revealed an excellent dosimetric response with a respectable linearity in the dose range of 0.05 to 1000 Gy, which is wider than its counterparts prepared by non nanosynthesis methods. They exhibited good luminescence efficiency and wide range linearity, suggesting the present phosphor nanoparticles may be considered as a suitable candidate for the dosimetric applications.

Abstract: Superconducting study present the properties of small weight percent of magnetic nanoparticles Dy₂O₃ from x = 0.0 to 0.10 added in Bi_1.6Pb_0.4Sr₂Ca₂Cu₃O_10+δ (Dy₂O₃)_x. It is found, the form size of magnetic nanoparticles Dy₂O₃ is spherical, nano Dy₂O₃ particles will enter easily into the Bi, Pb-2223 superconductor. From here it is early to conclude the inducing of Dy atoms into the Bi, Pb-2223 crystal structure because Bi-based superconductors are known for their strong anistropic properties and extremely short coherence length (ξ) as long there are significant change in it microstructure, lattice parameter and the normal state conductivity of the system. The characterization on critical temperature (T_c) and transport critical current density (J_c) of magnetic nanoparticles Dy₂O₃ added to enhance the optimum amount levels added. The maximum T_c achieved T_c-(R=0) 109 K (for x = 0.4) as samples respectively compared to the pure samples. This results will discussed directly to the basis properties changes in Bi, Pb-2223 with addition of magnetic nanoparticles of Dy₂O₃.

Abstract: We demonstrate how growth parameters may be adopted to produce morphologically controlled high-quality indium phosphide (InP) nanowires suitable for optoelectronic device applications. Growth temperature, V/III ratio, and catalyst particle size have a significant effect on the morphology, crystallographic quality, and optical properties of the resulting nanowires. Significantly, we find that higher growth temperatures or higher V/III ratios promote the formation of wurtzite (WZ) nanowires while zinc-blende (ZB) nanowires are favourable at lower growth temperatures and lower V/III ratios. Results also show that InP nanowires grow preferably in the WZ crystal structure than the ZB crystal structure with increasing V/III ratio or decreasing diameter. This causes a blue-shift in the bandgap as growth temperature increases. These results show that careful control of growth temperature, V/III ratio and catalyst size are crucial for obtaining InP nanowires of a specific crystal structure needed for device applications.

Abstract: Currently, Computer simulation has become an essential part of nanotechnology and engineering and science. Digital analysis of components, in particular, is important when developing new products or optimizing designs. Today a broad spectrum of options for simulation is available; researchers use everything from basic programming languages to various high-level packages implementing advanced methods. Though each of these techniques has its own unique attributes, they all share a common concern. Hence, the paper present a COMSOL simulation on nanostructures, the past and recent development nanostructures design and simulation for nanogap, nonporous, nanowires and carbon Nanotube. Keywords; Nanostructures. COMSOL Multiphysics, Nanowire, Nanogap, Nanotechnology.

Abstract: In this paper, an investigation of optimized vertical and non-vertical nano-slot silicon waveguides with different cover media (cladding) is presented. The mode properties and light confining effects for both of these slot waveguides geometry are investigated at operating wavelength of 1550nm. Light propagation of waveguide modal profiles for electric field and intensity of such slot waveguides are also presented.

Abstract: Nanofluid is a promising coolant for high-heat dissipation electronics device or system. The effect of nanofluids as thermal performances on a rectangular shape microchannel heat sink (MCHS) is analytically studied. Al₂O₃, SiC, and CuO nanoparticles dispersing in water were considered for analysis. A steady, laminar, and incompressible flow with constant heat flux was assumed in the channel. Nanofluids with concentrations of 0.5 to 4.0 vol. % were analyzed at two different inlet velocities of 0.5 m/s and 3.0 m/s. The results showed that highest thermal conductivity enhancement was 12.45% by using SiC-water nanofluids. In the case of Al₂O₃-water and CuO-water nanofluids maximum improvement were 11.98% and 11.36%, respectively for 4.0 vol. % of nanoparticle concentration. Furthermore, nanofluids as a coolant instead of water showed a highest improve of heat flux 8.51% for water-CuO, and 6.44% and 5.60% increase for Al₂O₃-water and SiC-water, respectively. The maximum pumping power found 0.33 W at 3 m/s and 0.0091 W at 0.5 m/s for the same concentration of 4.0 vol. % for all of these nanofluids.