Silica Films Containing Ordered Pores Prepared by Dip Coating of Silica Nanoparticles and Polystyrene Beads Colloidal Mixture

Silica films containing three dimensionally (3D) ordered pores were prepared by a simple dip coating method. A colloidal sol containing silica particles in the nanometer size range and a polystyrene latex (PSL) colloidal sol containing particles of tens of nanometers to one micrometer in size were used as precursors. The pore periodicity, which in turn produces the dielectric periodicity, can be easily altered by changing the size of the PSL beads. Films having a high surface smoothness were obtained by using small silica particles, large PSL particles, and a low withdrawal speed in the dip-coating. When the films were irradiated with a white light source, the reflective spectrum was changed by varying the incident angle, indicating its possible use as a monochromator. The change in the reflective spectrum was explained using effective medium approximation combined with a simple Bragg reflection equation.     

Effect of number of walls on plasmon energy in interaction of charged particles with double walled metallic nanotubes

The interaction of charged particles with double-walled metallic nanotubes (DWMNTs) has been investigated theoretically. Numerical results for energy dispersion relations as a function of the wave vector are presented when the charged particle is located outside of the nanotube. Calculations show that there are four modes for each angular mode (m) in DWMNT. Calculations show that the plasmon energy of DWMNTs depends on interwall spacing between two walls.     

In vitro biological evaluations of Fe3O4 compared with core–shell structures of chitosan-coated Fe3O4 and polyacrylic acid-coated Fe3O4 nanoparticles

Research on Chemical Intermediates - Today the use of magnetic nanoparticles (MNPs) is widely investigated because of their biocompatibility and nontoxicity. The objective of this study was to...     

Interaction of charged particles with nanotubes

We have studied the interaction of charged particles with single-walled metallic nanotubes by solving Poisson’s equation with appropriate boundary conditions. Numerical results for the energy dispersion relations as a function of the wave vector are presented when the charged particle is inside or outside the nanotube.     

Modified Homotopy Perturbation Method for Modeling Quantum Dots in the Quantum Clusters

The homotopy perturbation method (HPM) has been applied for the solving nonlinear differential equations of quantum dots (QDs). However, the HPM just gives the QDs behavior inside thick dielectric barriers as well as islands with deep quantum wells. In this paper, we apply a new approach which is based on modified homotopy perturbation method (MHPM) with self limiting model (SLM) to investigate the QDs behavior inside islands between clusters of sample surface. The MHPM and SLM are very effective, convenient and quite accurate to systems of partial differential equations and deal with nonlinearities distribution of the nonlinear differential equation. By using this method, we can find the exact solution of the QDs problem inside the islands.     

Experimental investigation of nanoparticle dispersion by beads milling with centrifugal bead separation

A new type of beads mill for dispersing nanoparticles into liquids has been developed. The bead mill utilizes centrifugation to separate beads from nanoparticle suspensions and allows for the use of small sized beads (i.e. 15-30 microm in diameter). The performance of the beads mill in dispersing a suspension of titanium dioxide nanoparticle with 15 nm primary particles was evaluated experimentally. Dynamic light scattering was used to measure titania particle size distributions over time during the milling process, and bead sizes in the 15-100 microm range were used. It was found that larger beads (50-100 microm) were not capable of fully dispersing nanoparticles, and particles reagglomerated after long milling times. Smaller beads (15-30 microm) were capable of dispersing nanoparticles, and a sharp peak around 15 nm in the titania size distribution was visible when smaller beads were used. Because nanoparticle collisions with smaller beads have lower impact energy, it was found by X-ray diffraction and transmission electron microscopy that changes in nanoparticle crystallinity and morphology are minimized when smaller beads are used. Furthermore, inductively-coupled plasma spectroscopy was used to determine the level of bead contamination in the nanoparticle suspension during milling, and it was found that smaller beads are less likely to fragment and contaminate nanoparticle suspensions. The new type of beads mill is capable of effectively dispersing nanoparticle suspensions and will be extremely useful in future nanoparticle research.     

Dielectric spectroscopy study of the new compound [C<Subscript>12</Subscript>H<Subscript>17</Subscript>N<Subscript>2</Subscript>]<Subscript>2</Subscript>CdCl<Subscript>4</Subscript>

The temperature dependence of the electrical conductivity of the compound 2,4,4-trimethyl-4,5-dihydro-3H-benzo[b] [1,4] diazepin-1-ium tetrachlorocadmiate in the different phases follows the Arrhenius law. The imaginary part of the permittivity constant is analyzed with the Cole–Cole formalism. In the temperature range 348–394 K, the activation energy of conductivity obtained from complex permittivity in regions I and II are, respectively, 1.03 and 0.33 eV, and E _m (in regions I and II are, respectively, 0.97 and 0.36 eV) obtained from the modulus spectra is close, suggesting that the ion transport is probably due to a hopping mechanism. The Kohlrausch–Williams–Watts function, j(t) = exp( - ( \fractt_\textKWW )^b ) \varphi (t) = \exp \left( { - {{\left( {\frac{t}{{{\tau_{\text{KWW}}}}}} \right)}^\beta }} \right) , and the coupling model are utilized for analyzing electric modulus at various temperatures. The decreasing of β at 373 K is due to approaching the temperatures of change in the conduction mechanism of the sample.     

The structure of the high-pressure gas jet from a spark plug fuel injector for direct fuel injection

Abstract  

A spark plug fuel injector (SPFI), which is a combination of a fuel injector and a spark plug was developed with the aim to convert any gasoline port injection spark ignition engine to gaseous fuel direct injection (Mohamad in Development of a spark plug fuel injector for direct injection of methane in spark ignition engine. PhD thesis, Cranfield University, 2006). A direct fuel injector is combined with a spark plug using specially fabricated bracket connected to a fuel pipe and a fuel path running along the periphery of a spark plug body to deliver the injected fuel to the combustion chamber. The injection nozzle of SPFI is significantly bigger than normal direct fuel injector nozzles. Therefore, it is important to understand the effect of such a configuration on the injection process and subsequently the air–fuel mixing behaviour inside the combustion chamber. The flow was visualized using the planar laser-induced fluorescent technique. For safety reasons, nitrogen was used as fuel substitute. Nitrogen at 50, 60 and 80 bar pressure was seeded with acetone as a flow tracer and injected into a bomb containing pressurised nitrogen. Bomb pressure was varied to simulate the pressure inside combustion cylinder during the compression stroke where actual injections in engine experiments will take place. The shape and depth of tip penetration of the gas jet were measured. Results show that the gas jet follows the behaviour suggested by vortex ball model (Turner in Mechanics 13:356–369, 1962). The cone angle and the maximum jet width of the fully developed gas jets from the SPFI injection are 23° and 25 mm, respectively regardless of the injection pressures. The penetration lengths of the fully developed jets are between 90 and 100 mm at 8–14 ms after the start of injection, depending on the bomb and injection pressure. Jet penetration is directly proportional to the injection pressure but inversely proportional to the cylinder or bomb pressure. The penetration lengths indicate that sufficient distance should be travelled by the gas jet for satisfactory air–fuel mixing in the engine.     

Multivariate curve resolution-alternating least squares (MCR-ALS) and central composite experimental design for monitoring and optimization of simultaneous removal of some organic dyes

In this work, multivariate curve resolution-alternating least squares (MCR-ALS) has been applied to resolve and study the simultaneous degradation of three toxic organic dyes using Fenton reaction. Second-order kinetic-spectrophotometric data in the simultaneous degradation of malachite green, crystal violet and methylene blue were analyzed by MCR analysis to get their concentration profiles and calculate their degradation factors. The effect of three parameters (Fe²⁺, H₂O₂ concentration and initial pH) and their possible interaction in the simultaneous degradation of mentioned dyes were studied and optimized using experimental design and response surface method. Acquiring second-order data makes possible the analysis and study of the studied dyes in the gray systems which is termed as second-order advantage in the literatures. The prominent point of this work is the combination of second-order data and response surface methodology.