Herein, we investigated the noncovalent interactions derived from functionalized carbon nanotube matrices grafting metallic alloy PtRu nanoparticle-decorated Vulcan carbon (fMWCNTs-g-PtRu/C) toward the enhancement of alcohol oxidation reactions. The fMWCNTs noncovalently grafted PtRu/C was successfully synthesized and demonstrated significant enhancement of the electro-catalytic activity and stability toward alcohol oxidation reactions as revealed by electrochemical characterizations. The presented results indicate that the grafting matrix specifically enhances ethanol oxidation reaction kinetics much more than methanol and propanol oxidation reactions. Since the same loading of PtRu/C was used for all tests, the differentiation between these reactants revealed the different strength of noncovalent interactions between the functional matrix and corresponding reactants. This result reveals a new strategy for using fMWCNTs matrix as potential catalyst supports due to its facile fabrication and functionalization, cost effectiveness and environmental friendliness, factors in which all of them are necessary for the practical application of direct alcohol fuel cells in near future.

Fabrication of integrated circuits is a multi-step process that involves chemical mechanical polishing (CMP) for planarizing the deposited layers. Although dependent on the consumables and machine operating conditions, most CMP researchers assume that the polishing occurs in the mixedlubrication regime, where the applied load on the wafer is supported by the hydrodynamic slurry pressure and the contact stress generated during the pad-wafer contact. The particle augmented mixed lubrication (PAML) approach has been employed by Terrell and Higgs (2009) as a high-fidelity asperity-scale mixed-lubrication CMP model. The current work introduces a more computationally efficient wafer-scale PAML model, called PAML-lite, which employs a two-dimensional average flow Reynold's Equation incorporating spatial dependence of entrainment velocities to model the hydrodynamic pressure. The contact mechanics are modeled using a Winkler elastic foundation in cylindrical polar coordinates. The resulting slurry hydrodynamic pressure distribution and contact stress are used to determine the equilibrium configuration of the system in the form of a nominal clearance and rolling and pitch angles. Local and wafer scale material removal rate (MRR) is predicted by assuming a uniform distribution of particle sizes. The prediction of PAML-lite were then benchmarked against experimental results. Upon verification, parametric studies were conducted to understand the effect of some unexplored CMP parameters.

The effect of tungsten oxide (WO3) thin film thickness on the surface plasmon resonance (SPR) properties have been investigated. WO3 films of varying the thickness (36 nm, 60 nm, 80 nm, 100 nm, 150 nm and 200nm) have been deposited onto Au coated prism (Au/prism) by radio frequency (RF) magnetron sputtering technique. The SPR responses of bilayer films were fitted with the Fresnel’s equations in order to calculate the dielectric constant of WO3 thin film. The variation of complex dielectric constant and refractive index with the thickness of WO3 thin film was studied.

The temperature dependence of cross-plane lattice thermal conductivity for thin film IV-VI semiconductors grown by molecular beam epitaxy was measured. Samples consisting of PbSe/PbSrSe multiple quantum wells (MQWs) on PbSe/PbSnSe superlattices (SLs) were grown with variations in SL layer thickness and the number of SL pairs. Localized lattice temperatures within the MQW layers were extracted from analysis of continuous wave photoluminescence (PL) emission spectra at heat sink temperatures between 100 K and 250 K. These data, finite element analysis, and electrical characterization were used to determine cross-plane lattice thermal conductivity of two different SL materials. A SL material with three different PbSe/PbSnSe thicknesses (1.2/1.2, 1.8/1.8, and 2.4/2.4 nm) exhibited a fairly constant lattice thermal conductivity from 1.2 to 1.3 W/mK as the sample was cooled from 250 K to 100 K. Another SL material with five different PbSe/PbSnSe thicknesses (0.5/0.5, 1.0/1.0, 1.6/1.6, 2.1/2.1, and 2.6/2.6 nm) exhibited very low lattice thermal conductivities from 0.46 to 0.47 W/mK 250 K to 100 K. These results are consistent with reflection of low energy heat transporting acoustic phonons within the SL material.

Carbon-Li4Ti5O12 (C-LTO) and carbon nanotube-Li4Ti5O12 (CNT-LTO) nanocomposite particles have been synthesized by hydrothermal method and a following high-temperature calcinations using a mixture of micro-size Li-Ti-O precursors and conducting black and carbon nanotubes, respectively. Two different types of coating layers have been characterized and analyzed on two kinds of Li4Ti5O12 particles surface by high resolution transmission electron microscopy images (HR-TEM) and selected area electron diffraction (SAED). Typical HR-TEM images and SAED patterns at nano-scale confirmed and showed that both particles exhibited a well-developed spinel nanocrystal with average sizes around 20-50 nm. The C-LTO particles exhibited the roughly spherical shape with more than 5 nm graphitic coating uniformly on the spherical surfaces; however, the CNT-LTO particles showed uniform square nanocrystal with edge length around 30 nm and a few layers of graphene covering the surface.

Electrochemical studies of galvanostatic discharge/charge cycling capacity testing indicated that both Li4Ti5O12particles showed the superior initial discharge capacity of more than 200 mA·h/g at 0.1C rate, and also the CNT-LTO particles show much improved specific capacity than that of the C-LTO particles during different cycling processing. It has been proposed that, grephene covering layers and the CNT interconnection networks are prove to increase electronic conductivity and improve the kinetics of Li4Ti5O12 toward fast lithium insertion/extraction. The comparative experimental results demonstrated that both nanoscale grephene layer and CNT inter-networks among particles is highly effective in improving the electrochemical properties of the CNT-LTO particles.

Mg@ZnO thin films were prepared by DC/RF magnetron co-sputtering in (N2+O2) ambient conditions using metallic Mg and Zn targets. We present a comprehensive study of the effects of film thickness, variation of O2 content in the working gas and annealing temperature on the structural, optical and magnetic properties. The band gap energy of the films is found to increase from 4.1 to 4.24 eV with the increase of O2 partial pressures from 5 to 20 % in the working gas. The films are found to be ferromagnetic at room temperature and the saturation magnetization increases initially with the film’s thickness reaching a maximum value of 14.6 emu/cm3 and then decreases to finally become diamagnetic beyond 95 nm thickness. Intrinsic strain seems to play an important role in the observed structural and magnetic properties of the Mg@ZnO films. On annealing, the as-obtained ‘mostly amorphous’ films in the temperature range 600 to 800°C become more crystalline and consequently the saturation magnetization values reduce.

Graphyne is a generic name for a family of carbon allotrope two-dimensional structures where sp2 (single and double bonds) and sp (triple bonds) hybridized states coexists. They exhibit very interesting electronic and mechanical properties sharing some of the unique graphene characteristics. Similarly to graphene, the graphyne electronic properties can be modified by chemical functionalization, such as; hydrogenation, fluorination and oxidation. Oxidation is of particular interest since it can produce significant structural damages.

In this work we have investigated, through fully atomistic reactive molecular dynamics simulations, the dynamics and structural changes of the oxidation of single-layer graphyne membranes at room temperature. We have considered α, β, and γ-graphyne structures. Our results showed that the oxidation reactions are strongly site dependent and that the sp-hybridized carbon atoms are the preferential sites to chemical attacks. Our results also showed that the effectiveness of the oxidation (estimated from the number of oxygen atoms covalently bonded to carbon atoms) follows the α, β, γ-graphyne structure ordering. These differences can be explained by the fact that for α-graphyne structures the oxidation reactions occur in two steps: first, the oxygen atoms are trapped at the center of the large polygonal rings and then they react with the carbon atoms composing of the triple bonds. The small rings of γ-graphyne structures prevent these reactions to occur. The effectiveness of β-graphyne oxidation is between the α- and γ-graphynes.

The main subject of this paper is to examine and to evaluate the capacitive behaviour of activated carbon electrodes electrochemically decorated by quinone-type functional groups. For this purpose, different electrolytes, i.e. hydroquinone, catechol and resorcinol at the concentration of 0.38 mol L-1, dissolved in 1 mol L-1 H2SO4, 1 mol L-1 Li2SO4 and 6 mol L-1 KOH were used. These electrolytes could generate electroactive groups (able to undergo reversible redox reactions) on the surface of electrode material. Apart from typical adsorption of the mentioned dihydroxybenzenes, so called grafting could occur and might cause generation of quinone|hydroquinone functionals on carbon surface. As an effect of functional reversible redox reaction, additional capacitance value, called pseudocapacitance, could be achieved. Hence, besides typical charge originating from charging/discharging of the electrical double layer on the electrode/electrolyte interface, additional capacitance comes also from faradaic reactions. Activated carbons are the most promising electrode materials for this purpose; apart from great physicochemical properties, they are characterized by well-developed specific surface area over 2000 m2 g-1 which results in high capacitance values.

In the manuscript the influence of the hydroxyl group location as well as electrolyte solution pH on the electrochemical performance of the electrode is discussed.

The synthesis of InP/ZnS core/shell nanocrystals and TiO2 nanotubes and the optimization study to couple them together were explored for quantum dot sensitized solar cells. InP/ZnS nanocrystals have advantages of tunable optical properties and intrinsic nontoxicity. Highly luminescent InP/ZnS nanocrystals were produced by precursor-based colloidal synthesis for a photosensitizer. In order to improve on air stability, ZnS shell was grown on InP core. The emission peak was observed at 550 nm. Transmission electron microscopy (TEM) image shows that the nanocrystals highly crystalline and monodisperse. TiO2 nanotube is main inorganic material which is capable of harvesting light as well as being a prominent anode electrode in solar cells. The nanotubular form of TiO2 enhances charge transfer and reduces interfacial charge recombination. Free-standing TiO2 nanotubes were produced by anodization using ammonium fluoride. The free-standing nanotubes were formed under the condition that chemical dissolution speed which depends on fluoride concentration was faster than the speed of Ti oxidation. Electrophoretic deposition was carried out to couple the InP/ZnS nanocrystals with the TiO2 nanotubes. Under an optimized applied voltage condition, the current during the electrophoretic deposition decreased continuously with time. The amount of the deposited nanocrystals was estimated by calculation and the deposited nanocrystals on the TiO2 nanotubes were observed in the TEM.

In this article, structural evolution in nickel doped zinc oxide nanostructures is reported. The ZnO nanostructures are synthesized with 1-10% of Ni doping adopting a chemical precipitation method. The undoped and doped nanostructures thus prepared, were systematically investigated employing X-ray diffraction (XRD), transmission and scanning electron microscopy (TEM/SEM), Fourier transform infrared (FTIR) and micro-Raman spectroscopy (μRS). The identification of wurtzite phase and determination of lattice parameters of Ni doped ZnO nanocrystallites is ascertained through XRD analysis. TEM/SEM images reveal the structural alteration of ZnO with variation of Ni doping concentrations. The study of vibrational modes of nanostructures at different stages of structural transformation, as performed through FTIR and Raman spectroscopy, assist in deciphering the crucial role of Ni doping concentration in gradual evolution of nickel doped ZnO structure from nanoparticles to nanorods.

Rare-earth telluride compounds are characterized by their high performance thermoelectric properties that have been applied to the development of functional materials [1]. Recently, May and co-workers reported that nanostructured bulk lanthanum telluride (La3-xTe4, 0 ≤ x ≤ 1/3) by mechanical ball-milling exceeded the figure of merit (ZT) of 1 at high temperatures near 1300K [2-3]. Since the increased thermoelectric efficiency of nanostructured materials is due to the enhancement of phonon scattering introduced by quantum confinement, thin films have also generated significant scientific and technological interest [4-6]. Here, we report on the electrodepostion of lanthanum telluride and lanthanum thin films in ionic liquids in ambient conditions. Surface morphologies varied from needle-like to granular structures and depend on deposition conditions. This novel electrochemical synthesis approach is a simple, inexpensive and laboratory-environment friendly method of synthesizing nanostructured thermoelectric materials.

The use of a laser annealing and chemical texturing process (dubbed the LaText process) on room-temperature sputtered ZnO:Al has been shown to generate unusually high haze properties, favorable for thin film silicon solar cells.This is due to the melting of the ZnO:Al layer by the XeCl laser, and the formation of crystalline domains onthe surface, for which the grains and grain boundaries are subsequently etched at different rates. The unusual surface morphology produced through this process can strongly impact the nature of the amorphous or microcrystalline silicon material deposited thereupon. In this paper, we report on results for amorphous silicon devices, for which the surface texture is seen to slightly impact thelight absorption in the material, but more interestingly, also the light-induced degradation of the cells.For co-deposited cells, devices deposited on surfaces with the characteristic "LaText" morphologyundergo a much lesser degradation. Furthermore, the decreased degree of degradation coincides with a notable shift in the Raman scattering peak. This provides a rapid diagnostic for testing multiple textures and deposition parameters.

Pastes of waste glass (WG) and metakaolin (MK) were prepared by chemical activation with sodium silicate solutions of modulus Ms = 0.5, 0.75, 1 and 1.25 adjusted with sodium hydroxide. An experimental design was carried out using the Taguchi method. The compressive strength (CS) was followed for up to 120 days and then 4 selected formulations of the higher CS were further characterized by X-ray diffraction and scanning electron microscopy. The results showed that the CS depends on the experimental conditions of %WG, %Na2O and Ms and showed a maximum of 70 MPa after 120 days for the paste with 100%WG (%wt.), 8% Na2O and Ms=1.25; while a Portland cement specimen cured at 20°C reached 43MPa. The WG is more reactive than the MK under less alkaline conditions. The features of the microstructures varied notably with the %WG; however all showed relative dense matrices of reaction products, in agreement with the CS attained.

Silicon nanowires are becoming more important because of increasing requirements of the small scale and dense integration of devices. We report a top-down fabrication method for silicon nanowires using high-energy ion beam irradiation of bulk p-type silicon followed by electrochemical etching. Silicon nanowires with a diameter of ∼50nm have been fabricated and densely patterned nanowire arrays fabricated in different resistivity silicon wafers. With a suitable support structure, free standing silicon nanowires are also achieved. We investigate results depending on silicon wafer resistivity and location within the irradiated area.

Hybrid silicon laser is a promising solution to enable high-performance light source on large-scale, silicon-based photonic integrated circuits (PICs). As a compact laser cavity design, hybrid microring lasers are attractive for their intrinsic advantages of small footprint, low power consumption and flexibility in wavelength division multiplexing (WDM), etc. Here we review recent progress in unidirectional microring lasers and device thermal management. Unidirectional emission is achieved by integrating a passive reflector that feeds laser emission back into laser cavity to introduce extra unidirectional gain. Up to 4X of device heating reduction is simulated by adding a metal thermal shunt to the laser to “short” heat to the silicon substrate through buried oxide layer (BOX) in the silicon-on-insulator (SOI) substrate. Obvious device heating reduction is also observed in experiment.

Grain boundaries are known to be able to impede phonon transport in the material. In the thermoelectric application, this phenomenon could help improve the figure-of-merit (ZT) and enhance the thermal to electrical conversion. Bi2Te3 based alloys are renowned for their high ZT around room temperature but still need improvements, in both n- and p-type materials, for the resulting power generation devices to be more competitive. To implement high density of grain boundaries into the bulk materials, a bottom-up approach is employed in this work: consolidations of nanocrystalline powders into bulk disks. Nanocrystalline powders are developed by high energy cryogenic mechanical alloying that produces Bi(Sb)Te(Se) alloy powders with grain size in the range of 7 to 14 nm, which is about 25% finer compared to room temperature mechanical alloying. High density of grain boundaries are preserved from the powders to the bulk materials through optimized high pressure hot pressing. The consolidated bulk materials have been characterized by X-ray diffraction and transmission electron microscope for their composition and microstructure. They mainly consist of grains in the scale of 100 nm with some distributions of finer grains in both types of materials. Preliminary transport property measurements show that the thermal conductivity is significantly reduced at and around room temperature: about 0.65 W/m-K for the n-type BiTe(Se) and 0.85 W/m-K for the p-type Bi(Sb)Te, which are attributed to increased phonon scattering provided by the nanostructure and therefore enhanced ZT about 1.35 for the n-type and 1.21 for the p-type are observed. Detailed transport properties, such as the electrical resistivity, Seebeck coefficient and power factor as well as the resulting ZT as a function of temperature will be described.

In this study the length scale dependence of the operative mechanisms of time-dependent plastic deformation was studied using room temperature compression tests performed on Au micro-pillars and micro-spheres of 1.0 to 5.0 µm diameter. All the samples tested displayed deformation that had a component of random strain jumps. In the case of the Au micro-pillars, the frequency of the strain jumps showed a bilinear dependence upon pillar diameter with the frequency being larger, and more sensitive to diameter, when the pillar diameter was small (and τR was high). We suggest that this indicates a transition from deformation occurring by deformation on multiple slip planes to deformation occurring predominantly by single-plane dislocation slip when the pillar diameter is less than 2 µm.

The strain jump frequency during the constant-load micro-pillar creep tests showed a linear dependence upon τR. Creep tests performed on the micro-spheres of 5.0 µm diameter displayed displacement jump frequency that was essentially independent of the applied load while the jump frequency increased with increasing load for the smaller 2.5 µm diameter micro-spheres. We suggest that this difference is related to the volume of the micro-sphere. When the volume is small, the component of the deformation that occurs by a stochastic dislocation glide process is increased and becomes strongly dependent upon the magnitude of the local shear stress.

In the past fifty years, experimental works based on TEM or grazing incidence X ray diffraction have clearly shown that alloys and ceramics exhibit a nano pattering under irradiation [1,2,3]. Many works were devoted to study the nano patterning induced by ion beam mixing in solids [17,18,19]. Understanding the nano patterning will provide scientific bases to tailor materials with well-defined microstructures at the nanometric scale. The slowing down of impinging particles in solids leads to a complex distribution of subcascades. Each subcascade will give rise to an athermal diffusion of atoms in the medium. In this work, we focused on this point. Based on the well-known Cahn Hilliard Cook (CHC) equation, we analytically calculate the structure factor describing the nano patterning within the mean field approximation. It has shown that this analytical structure factor mimics the structure factor extracted from direct numerical simulations of the time dependent CHC equation. It appears that this structure factor exhibits a universal feature under irradiation.

We employ Monte Carlo simulations of the electron transport that occurs within the two-dimensional electron gas formed at a ZnO/ZnMgO heterojunction. Steady-state and transient electron transport results are presented. We find that at high fields, increases in the free electron concentration result in decreases in the electron drift velocities.