Time filter

Source Type

Feng P.,University of Puerto Rico at San Juan | Sajjad M.,University of Puerto Rico at San Juan | Li E.Y.,University of Puerto Rico at San Juan | Zhang H.,Globalfoundrie | And 3 more authors.
Beilstein Journal of Nanotechnology | Year: 2014

We report studies of the surface fringe structures and tunable bandgap width of atomic-thin boron nitride nanosheets (BNNSs). BNNSs are synthesized by using digitally controlled pulse deposition techniques. The nanoscale morphologies of BNNSs are characterized by using scanning electron microscope (SEM), and transmission electron microscopy (TEM). In general, the BNNSs appear microscopically flat in the case of low temperature synthesis, whereas at high temperature conditions, it yields various curved structures. Experimental data reveal the evolutions of fringe structures. Functionalization of the BNNSs is completed with hydrogen plasma beam source in order to efficiently control bandgap width. The characterizations are based on Raman scattering spectroscopy, X-ray diffraction (XRD), and FTIR transmittance spectra. Red shifts of spectral lines are clearly visible after the functionalization, indicating the bandgap width of the BNNSs has been changed. However, simple treatments with hydrogen gas do not affect the bandgap width of the BNNSs. © 2014 Feng et al.

Dhiman P.,Himachal Pradesh University | Batoo K.M.,King Abdullah Institute for Nanotechnology | Kotnala R.K.,National Physical Laboratory India | Singh M.,Himachal Pradesh University
Micro and Nano Letters | Year: 2012

A report is presented on the structural, electrical, optical and magnetic properties of Fe-doped ZnO nanoparticles synthesised by the solution combustion technique. Structural characterisation by X-ray diffraction confirmed the phase purity of the samples. Surface morphology studied by scanning electron microscope revealed a cubic-type shape of grains. Energy dispersive X-ray spectroscopy analysis confirmed the elemental composition. Less value of DC electrical conductivity and increased bandgap for doped ZnO from UV-Vis studies confirmed change in the defect chemistry of the ZnO matrix. However, varied synthesis process results in ferromagnetic behaviour for doped ZnO nanoparticles. © 2012 The Institution of Engineering and Technology.

Ghannam T.,King Abdullah Institute for Nanotechnology
Applied Optics | Year: 2013

This paper investigates a specific kind of solitary pulse, the modulated zero-area (MZA) solitary pulse, when propagating within MgO photonic bandgap medium doped with silver nanoparticles (NPs). It will be shown that two coupled MZA pulses do propagate unattenuated within this medium but for a certain combination of the dipole moments and the density of the NPs. More important, and in contrast to the other kinds of solitary pulses, one of the two MZA pulses exhibits a slowing in its group velocity in comparison to the other one, depending on the amplitudes of the components of the dipole moments of the NPs that are in resonance with the two MZA pulses. With this particular feature, the system has the potential of working as an all-optical switch. © 2013 Optical Society of America.

Kawwam M.,CNRS Laboratory of Physical Chemistry of Luminescent Materials | Kawwam M.,King Abdullah Institute for Nanotechnology | Alharbi F.,King Abdulaziz City for Science and Technology | Alharbi F.,Qatar Environment and Energy Research Institute | And 3 more authors.
Applied Surface Science | Year: 2012

Cupric oxide (CuO) films were prepared on various substrates by the pulsed laser deposition (PLD) technique to investigate their effects on surface morphology. As the substrate temperature decreased, the film surface roughness was also observed to decrease. This trend was also correlated with the polycrystalline structure of the films. Deposition at low pressures produced greater surface roughness because larger crystallites emerged from the surface, while higher oxygen pressure under an adjusted target-substrate distance produced smaller crystallites and a smoother film surface. Reducing the laser energy density led to lower densities and smaller micro-liquid droplets formed on the surfaces. The presented results could be useful for better understanding the effect of process parameters control on CuO film morphology. It could also serve as a reference for the fabrication of CuO-based devices, in which the surface quality of the CuO films is highly important. © 2012 Elsevier B.V.

Ali M.,King Saud University | Ali M.,King Abdullah Institute for Nanotechnology | Zeitoun O.,King Saud University | Zeitoun O.,King Abdullah Institute for Nanotechnology | Almotairi S.,King Saud University
International Journal of Thermal Sciences | Year: 2013

Experimental investigation on natural convection heat transfer has been carried out inside vertical circular enclosures filled with Al 2O 3 nanofluid with different concentrations; 0.0%, 0.85% (0.21%), 1.98 (0.51%) and 2.95% (0.75%) by mass (volume). Two enclosures are used with 0.20 m inside diameter and with two different aspect ratios. The bottom surface of the enclosure is heated using a constant heat flux flexible heater while the upper surface is cooled by an ambient air stream. Various uniform heat fluxes have been used to generate the natural convection heat transfer data. The average Nusselt number is obtained and correlated with the modified Rayleigh number at each concentration ratio of the nanofluid. The average Nusselt number is obtained for each enclosure and correlated with the modified Rayleigh number using the concentration ratio as a parameter. The results show that the heat transfer coefficient increases as the concentration increases up to a specific value of the concentration and then it decreases as the concentration continues to increase compared to the basic fluid of pure water. Furthermore, a general correlation is obtained using the volume fraction and the aspect ratio as parameters. © 2012 Elsevier Masson SAS. All rights reserved.

Discover hidden collaborations