xPb(Yb1/2Nb1/2)O3-(1 − x)Pb(Zr0.36Ti0.64)O3 (xPYN-(1 − x)PZT) piezoelectric ceramics were prepared by the conventional ceramic processing via a B-site oxide mixing route. The synthesized xPYN-(1 − x)PZT ceramics exhibit majority of perovskite structure with slight content of impurity, which exhibit typical tetragonal structure with slight orthorhombic distortion depending on compositions. All the xPYN-(1 − x)PZT ceramics exhibit high Curie temperature (TC/Tm), higher than 380 °C, and their dielectric behavior above TC/Tm can be fitted well by the Curie-Weiss law. The xPYN-(1 − x)PZT ceramics exhibit large resistivity, and excellent ferroelectric and piezoelectric properties, which provide promising for the high-power and high-temperature piezoelectric applications. However, electric energy density of the xPYN-(1 − x)PZT ceramics is small due to their nearly rectangular shape of polarization-electric field (P-E) hysteresis loop and early electric displacement saturation, which is not suitable for high energy and power storage applications.

A broadband omnidirectional absorber which is realized by heterostructures containing a collision plasma layer and a zero − n̅ mirror is theoretically investigated. A collision plasma layer and an appropriate dielectric layer are put on the top of the PC. It is shown to absorb roughly 70% of all available electromagnetic wave in a relative omnidirectional absorption band width 244 MHz. The absorption band edge of the PC is influenced by the range of the reflection band gap. Meanwhile, the absorption range for the transverse magnetic (TM) wave decreases at large incident angle. Compared with some previous designs, our proposed structure has a relative flatter total absorption spectrum over a broad microwave frequency range and using a zero − n̅ gap as a mirror is insensitive to the incident angle. This kind of heterostructure offers additional opportunities to design novel optoelectronic devices.

Recent studies have shown that graphene paper (GP) is a promising candidate for novel applications in energy storage systems such as electrical batteries and supercapacitors. In this study, a low-cost and free-standing GP was produced by graphene oxide paper (GOP) in the thermal reduction method which heated GOP slowly to 500 °C in a special fixture. In the process of reduction, oxygen functional groups were decomposed and graphene oxide (GO) sheets were reduced to grapene sheets. Moreover, the smooth paper-like structure was maintained by the protection of the special fixture during the heat treatment. The GP paper showed good electrochemical property. The electrical conductivity of the GP reached 182 S cm−1 after the decomposition of oxygen functional groups. The GP as binder-free anodes of lithium ion batteries afforded a capacity of 576 mAh g−1 with good cycling stability.

ZnO thin films were deposited by reactive cathodic radio-frequency (RF) sputtering from a pure Zn target in a gas mixture of 30% O2 and 70% Ar and at different RF powers. The structural properties of the as-deposited thin films were studied by X-ray diffraction (XRD). The optical properties (especially the refractive index, absorption coefficient and optical band gap) were investigated by optical transmission measurements in the ultraviolet-visible-near Infrared wavelength range. The XRD patterns showed that the as-deposited ZnO thin films are polycrystalline. The crystallite size varied with RF power reaching a maximum at 200 W. These results were correlated with X-ray refectometry measurements which revealed a minimum in the film density at 200 W. The deposition rate of these films varied from 2.53 to 5.27 nm/min depending on the RF-power, with a maximum at 200 W. On the other hand, the optical band gap Eg was quasi-constant (about 3.28 eV) when the RF power was increased from 100 to 300 W.

The electronic transport properties of Ga2As2 cluster, which is sandwiched between two semiinfinite Au (1 0 0)-3 × 3 pyramical-shaped electrodes with the Ga-Ga axis of the cluster parallel to the transport direction and the As-As axis of the cluster parallel to the transport direction, respectively, is investigated with a combination of density functional theory and the non-equilibrium Green’s function method. We have simulated the nanoscale junctions breaking process and found that the conductance of cluster decreases then increases when the contact is pulled apart in two configurations. We analyzed the difference of conductance from transmission spectra and projected density of states, and calculated the I-V characteristics of devices in this two configurations when dz = 2.0 Å. The I-V curves display a linear characteristics in the voltage range of 0 ∼ 2.2 V. The negative differential resistance appears within a small range of voltage in the junctions with As-As axis of the cluster parallel to the transport direction when bias is larger than 2.2 V.

Nanocrystalline Ni0.7−yZn0.3CayFe2O4 (0.0 ≤ y ≤ 0.7) has been obtained by soft coprecipitation method at different calcination temperatures. The influence of Ca2+ content and heat treatment on microstructure and magnetic properties are investigated using X-ray diffraction (XRD), thermal analysis, scanning electron microscope (SEM), atomic force microscope (AFM) and infrared (IR) spectroscopy. XRD analysis reveals single phase of spinel structure in ferrite with y = 0.2. An endothermic peak in DSC curve is appeared around 700 °C for all compositions due to collapse of the defective surface layer covers the grains. IR spectra for precursors or calcined ferrites shows the existence of bands characteristic for cubic spinel phase. The higher values for specific saturation magnetization (Ms) was obtained for ferrites calcined at 600 °C. Paramagnetic ordered particles was dominated when Ca2+ content increases more than 0.3. On the other hand, the coercivity of the present ferrites is strongly depends on Ca2+ content than calcination temperature.

Lithium ion battery cathode material LiNi0.8Co0.15Al0.05O2 cathode has successfully prepared by co-precipitation. CeO2 surface modification has improved LiNi0.80Co0.15Al0.05O2 electrochemical performance use sol-gel method and subsequent heat treatment at 600 °C for 5 h. Different to other conventional coating material, CeO2 coating layer can not only inhibit the reaction of the electrode and the electrolyte, but also can reduce the impedance of electron transfer due to its high conductivity, and inhibit the production of Ni2+ because of its high oxidation. The surface-modified and pristine LiNi0.80Co0.15Al0.05O2 powders are characterized by XRD, SEM, TEM, XPS, CV and DSC. When CeO2 coating is 0.02% (mole ratio), contrast to pristine NCA, the CeO2-coated NCA cathode exhibits no decrease in its initial specific capacity of 184 mAh g −1 (at 0.2 C) and excellent capacity retention (86% of its initial capacity at 1 C) between 2.75 and 4.3 V after 100 cycles. The results indicate that the CeO2 surface treatment should be an effective way to improve cycle properties due to CeO2 inhibit the electrodes and the electrolyte side effects.

In embedded systems such as electric vehicles, Proton exchange membrane fuel cell (PEMFC) has been an attractive technology for many years especially in automotive applications. This paper deals with PEMFC operation monitoring which is a current target for improvement for attaining extended durability. In this paper, supervision of the PEMFC is done using knowledge-based models. Without extra sensors, it enables a clear insight of state variables of the gases in the membrane electrode assembly (MEA) which gives the PEMFC controller the ability to prevent abnormal operating conditions and associated irreversible degradations. First, a new state-observer oriented model of the PEM fuel cell is detailed. Based on this model, theoretical and practical observability issues are discussed. This analysis shows that convection phenomena can be considered negligible from the dynamic point of view; this leads to a reduced model. Finally a state-observer enables the estimation of the inner partial pressure of the cathode by using only the current and voltage measurements. This proposed model-based approach has been successfully tested on a PEM fuel cell simulator using a set of possible fault scenarios.

The thermal conductivity of the mesoporous composites Cu/MCM-41 was studied to provide some useful data for promising applications. Both of the lattice and electronic thermal conductivities of Cu nanowires with different size were predicted. With the shell of the matrix MCM-41 and the air confined in the mesochannels considered, the effective thermal conductivity (EffTC) of composites Cu/MCM-41 was obtained. The EffTC shows a great anisotropy. The EffTC along the Z direction (axial of the mesochannel) is much lower than that along directions perpendicular to the axial. It is unnecessary to further raise the filling ratio of Cu nanowires for improving the EffTC along the directions perpendicular to the axial, since the filling ratio 20% is high enough. As long as there is a void space in the mesochannel, the EffTC along the Z direction will be as low as the thermal conductivity of the matrix MCM-41, due to the large thermal resistance of the void space in mesochannels.

In solar still, transparent cover plays a decisive role in the process of evaporation and condensation of water. Also receiving the solar radiation strongly depends on the geometry and orientation of the glass. In order to determine the impact of changing glass cover geometry on conventional solar still heat balance, we elaborate a theoretical model for a spherical solar still. The obtained equations are solved by using 4th order Runge–Kutta method. The numerical results allowed us to evaluate the water temperatures and the yield of still. Theoretical results are validated by the experimental tests in different climatic conditions. We observed that the spherical geometry of the transparent cover has the advantage of a large surface of condensation and does not have a preferred direction to capture maximum of solar energy.

This work is undertaken to study the reliability of eddy current nondestructive testing (ED-NDT) when the defect concerns a change of physical property of the material. So, an intrusive spectral stochastic finite element method (SSFEM) is developed in the case of 2D electromagnetic harmonic equation. The electrical conductivity is considered as random variable and is developed in series of Hermite polynomials. The developed model is validated from measurements on NDT device and is applied to the assessment of the reliability of failure in steam generator tubing of nuclear power plants. The exploitation of the model concerns the impedance calculation of the sensor and the assessment of the reliability of failure. The random defect geometry is also considered and results are given.

Superionic solids an area of multidisciplinary research activity, incorporates to study the physical, chemical and technological aspects of rapid ion movements within the bulk of the special class of ionic materials. It is an emerging area of materials science, as these solids show tremendous technological scopes to develop wide variety of solid state electrochemical devices such as batteries, fuel cells, supercapacitors, sensors, electrochromic displays (ECDs), memories, etc. These devices have wide range of applicabilities viz. power sources for IC microchips to transport vehicles, novel sensors for controlling atmospheric pollution, new kind of memories for computers, smart windows/display panels, etc. The field grew with a rapid pace since then, especially with regards to designing new materials as well as to explore their device potentialities. Amongst the known superionic solids, fast Ag+ ion conducting crystalline solid electrolytes are attracted special attention due to their relatively higher room temperature conductivity as well as ease of materials handling/synthesis. Ion conduction in these electrolytes is very much interesting part of today. In the present review article, the ion conducting phenomenon and some device applications of crystalline/polycrystalline superionic solid electrolytes have been reviewed in brief. Synthesis and characterization tools have also been discussed in the present review article.

Li2SO4 have been synthesized from lithium sulphate monohydrate by melting at 880 °C and slow cooling. The XRD results indicates that the melt cooled Li2SO4 is crystallized to monoclinic structure. The AC conductivity (σac) and dielectric relaxation (tan δ) have been measured within the temperature range 170–250 °C and frequency range 100 Hz–120 kHz, respectively. The DC conductivities are conveniently extracted from σac (typical values ∼2 × 10−7 and ∼2 × 10−6 S/cm at 200 and 250 °C, respectively) and are fitted to linear Arrhenius plot. The slope of this linear plot leads to an activation energy of 1.10 eV. It is found that the conduction in Li2SO4 is mainly through Li+. Further, we carried out first principles calculations and obtained the structural and bonding properties of Li2SO4. From band structure, Li2SO4 is found to be a wide band gap insulator with a band gap of 6.1 eV. The partial density of states reveals the finite states of Li+ near to Fermi level, which limits its use of full capacity. This indicates a kinetic barrier for Li ions and electrons ambipolar diffusion.

A systematic study of the electric-field-induced forces between a solid glass sphere and a flat gold-plated substrate filled with an insulating liquid has been carried out. Using atomic force microscopy, we measure the electrostatic force f(s, V) between the sphere and substrate as a function of the surface separation s and applied voltage V. The measured f(s, V) is found to be well described by an equation for a conducting sphere. Further force measurements for the “wet” porous glass spheres filled with an aqueous solution of urea and the dried porous glass spheres filled with (dry) air suggest that there is a water layer of a few nanometers in thickness adsorbed on the hydrophilic glass surface under ambient conditions. This adsorbed water layer is more conductive than the dielectric core of the glass sphere, making the sphere surface to be at a potential close to that of the cantilever electrode. As a result, the electric field is strongly concentrated in the gap region between the glass sphere and gold-plate substrate and thus their electrostatic attraction is enhanced. This surface conductivity effect is further supported by the thermal gravimetric analysis (TGA) and force response measurements to a time-dependent electric field. The experiment clearly demonstrates that the adsorption of a conductive water layer on a hydrophilic surface plays a dominant role in determining the electrostatic interaction between the dielectric sphere and substrate.