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.

We present our preliminary results on a novel technique to electrophoretically sort singlewall carbon nanotubes into metallic and semiconducting tubes using a free-solution nonionic surfactant in a homemade electrophoretic vertical cell. The technique is used to sort purified commercial product SWCNTs, (Thomas Swan Elicarb) into metallic and semiconducting tubes. In contrast to onventional electrophoresis techniques, which takes more than 24 hours to obtain efficient separation, our approach takes ∼ 6 hours to achieve efficient separation, which reduces the separation time by four fold. Characterization of the sorted tubes with micro-Raman spectroscopy analysis shows very strong enrichment of both metallic and semiconducting tubes.

In this paper, we provide the investigation about the controlled surface functionalization of acrylic toner particles for electro photography (“laser printing”) with sodium hydroxide and the subsequent carbodiimide-mediated coupling of numerous functional amines onto the generated carboxylic group. Various chemically valuable functionalities, comprising of thiol, alkyne and azide, were bound onto the particles’ surface and allow for further versatile modifications via huisgen cycloaddition as well as thiol-ene reaction. The functionalization of the acrylic toner surface with alkyne, azide and carboxylic groups increased the cell viability up to 178 % ± 22 % and might offer an interesting path for new applications using common laser printing techniques.

Large electrocaloric (EC) effects in ferroelectric polymers and in ferroelectric ceramics have attracted great attention for new refrigeration development which is more environmental friendly and more efficient and thus could be an alternative to the existing vapor-compression refrigerators which consume large energy and release large amount of green house gas. However in the past, all EC effects investigations have been focused on solid state dielectrics. It is interesting to ask whether a large EC effect can also be realized in dielectric fluids. A dielectric fluid with large EC effect could lead to new design of cooling devices with simpler structures than these based on solid state EC materials, for example, they can be utilized as both the refrigerant and heat exchange fluid. Here we present that a large EC effect can be realized in the liquid crystal (LC) 5CB near it's nematic-isotropic (N-I) phase transition. The LC 5CB possesses a large dielectric anisotropy which can induce large polarization change from the isotropic phase to the nematic phase near the N-I transition. An isothermal entropy change of more than 23 Jkg-1K-1 was observed near 39 oC that is just above the N-I transition.

Diamond was investigated as one of the superior dielectric materials for advanced wakefield accelerators. Both planar and cylindrical wakefield accelerating structures were constructed. An AsTex microwave plasma-enhanced CVD system was modified for synthesis of cylindrical polycrystalline diamond tubes. Cylindrical diamond tubes were successfully synthesized from hydrogen and methane and are characterized with micro Raman, photoluminescence spectroscopy and optical tests. In addition, planar wakefield structures were constructed from commercially available diamond. Wakefield tests on a rectangular diamond structure confirm that diamond can sustain microwave electric field strengths of 0.3 GV/m at its surface without material breakdown.

The sulfur-iodine thermo-chemical cycle (S-I cycle) is one of the promising nuclear hydrogen production methods combined with a high temperature gas-cooled reactor. However, extremely corrosive environments limit the selection of structural materials. Therefore, in this study, corrosion behaviors of several metallic materials were investigated to screen the candidate metallic materials. Coupon type specimens were exposed for 100 h in simulated SO3 and HI decomposer conditions at 850 °C. After 100 h exposure, the surface treated Alloy 617 showed the superior weight change in both environments. However, scanning electron microscope observation showed oxide spallation for EB-treated and NiAl coated Alloy 617. On the other hand, the Ni3Al coated Alloy 617 showed better corrosion resistance in SO3 decomposer condition, such that only formed external Al-rich oxide layer. Especially, in a HI decomposer condition, the damage on the Ni3Al coated Alloy 617 was considerably less significant probably due to the protection by very thin aluminum-rich oxide on the surface.

As ohmic contacts decrease in size and approach nanoscale dimensions, accurate electrical characterization is essential, requiring the development of suitable test structures for this task. We present here a new test structure derived from the standard three-contact circular transmission line model (CTLM) [1], for determining the specific contact resistivity of ohmic contacts. This test structure minimizes sources of error which arise from the CTLM by – (i) reducing the number of contacts within one test pattern from three to two, (ii) ensuring the assumption of equipotential metal contacts used in modelling is more easily attained experimentally, and (iii) allowing the fabrication of reduced geometrical dimensions essential for determining low specific contact resistivity values. The analytical expressions are presented and experiment results are undertaken to demonstrate the accuracy of the technique. There are no error corrections required for determining contact parameters using the presented test structure.

A Ni3(Si,Ti) intermetalic alloy was synthesized by the powder metallurgy method using elemental powders. The raw powder mixtures with various compositions were sintered by a spark plasma sintering apparatus and then homogenized at high temperatures. Microstructure, hardness, tensile properties and density of the sintered alloys were investigated as functions of the chemical composition and sintering temperature. It was found that a highly-densified Ni3(Si,Ti) sintered alloy was obtained by choosing proper chemical composition and sintering temperature. Also, the Ni3(Si,Ti) sintered alloy with an L12 single-phase microstructure exhibited high hardness and tensile strength.

PECVD growth of the microcrystalline silicon junction on a highly textured amorphous top cell often leads to defective absorber layers and finally to low quality bottom cell. This paper reports on the current status of using an innovative smoothening/reflective layer (SRL) as alternative intermediate reflector between top and bottom cell of a Micromorph tandem device deposited on as-grown highly textured LPCVD ZnO layer. Manufacturing of the SRL layer is realized by “liquid phase” deposition technologies. Optical and electrical properties, smoothening effect and photoelectrical results of Micromorph tandem devices are discussed. The implementation of our novel SRL results in the growth of a crack-free bottom cell and to an efficient current transfer from the bottom to the top cell.