Deposition and characterization of diamond-like nanocomposite coatings grown by plasma enhanced chemical vapour deposition over different substrate materials

Diamond-like nanocomposite (DLN) coatings have been deposited over different substrates used for biomedical applications by plasma-enhanced chemical vapour deposition (PECVD). DLN has an interconnecting network of amorphous hydrogenated carbon and quartz-like oxygenated silicon. Raman spectroscopy, Fourier transform–infra red (FT–IR) spectroscopy, transmission electron microscopy (TEM) and X-ray diffraction (XRD) have been used for structural characterization. Typical DLN growth rate is about 1  ${\upmu} $ m/h, measured by stylus profilometer. Due to the presence of quartz-like Si:O in the structure, it is found to have very good adhesive property with all the substrates. The adhesion strength found to be as high as 0·6 N on SS 316 L steel substrates by scratch testing method. The Young’s modulus and hardness have found to be 132 GPa and 14· 4 GPa, respectively. DLN coatings have wear factor in the order of 1 × 10^???7 mm ³ /N-m. This coating has found to be compatible with all important biomedical substrate materials and has successfully been deposited over Co–Cr alloy based knee implant of complex shape.     

Characterization and in vitro and in vivo evaluation of cross-linked chitosan films as implant for controlled release of citalopram

The aim of the present study is to develop cross-linked chitosan (CH) films that can release drug over an extended period of time and that too in a controlled manner. A solution of different percentages of CH, is prepared in 1% lactic acid, followed by addition of citalopram (CTP) and then reacted with increasing amounts of glutaraldehyde (GL) to obtain films with different cross-linking densities. Prepared films are characterized for their physical and mechanical properties. The films are then subjected to in vitro drug release studies using pH 7·4 phosphate buffer saline (PBS) as dissolution medium and cumulative amount of drug released is calculated. Kinetic analysis of drug release is performed using Power law model and Higuchi’s model. With increase in concentration of CH, water absorption capacity and mechanical strength are increased; whereas, water vapour permeability and elasticity of the films are decreased. The effect of cross-linking agent, GL, is such that with an increase in the amount of GL, water vapour permeability, water absorption capacity and elasticity of the films are decreased; whereas, mechanical strength increased to some extent and then decreased. In vitro release studies indicate that films containing 3% CH, cross-linked with 2–3% GL and films containing 4% CH, cross-linked 1% GL are able to sustain the drug release for a prolonged time along with releasing almost complete drug in a desired period. Out of these batches, films containing 3% CH, cross-linked with 2–3% GL are having sufficient strength, water vapour permeation, water absorption capacity and elongation at break for implantation purpose. The in vitro degradation studies and histopathological studies were carried out with a sample film (batch C3 as in table 1) in rabbit model. In vitro degradation study indicates that the films maintained their integrity for desired implantation. The histopathological studies under optical microscope indicates that on implanting, there is no evidence of any inflammation, any foreign body granuloma or any necrosis or hemorrhage. Tissue configuration remains unaltered after 30 days of implantation. So, it can be suggested that cross-linked CH films of above said composition can be used as implant for long term application in depression and related disorders.     

Electrochemical potentials of layered oxide and olivine phosphate with aluminum substitution: A first principles study

First-principles prediction of enhancement in the electrochemical potential of LiCoO₂ with aluminum substitution has been realized through earlier experiments. For safer and less expensive Li-ion batteries, it is desirable to have a similar enhancement for alternative cathode materials, LiFePO₄ and LiCoPO₄. Here, we present first-principles density functional theory based analysis of the effects of aluminum substitution on electrochemical potential of LiCoO₂, LiFePO₄ and LiCoPO₄. While Al substitution for transition metal results in increase in electrochemical potential of LiCoO₂, it leads to reduction in LiFePO₄ and LiCoPO₄. Through comparative topological analysis of charge density of these materials, we identify a ratio of Bader charges that correlates with electrochemical potential and determine the chemical origin of these contrasting effects: while electronic charge from lithium is transferred largely to oxygen in LiCoO₂, it gets shared by the oxygen and Co/Fe in olivine phosphates due to strong covalency between O and Co/Fe. Our work shows that covalency of transition metal–oxygen bond plays a key role in determining battery potential.     

TRANSIENT STABILITY SIMULATION OF UNBALANCED LARGE SCALE POWER SYSTEMS

ABSTRACT

Conventional transient stability analysis is performed on the basis of a balanced system representation. However, a typical power system may be unbalanced due to a variety of reasons, and the computations of sequence quantities due to these unbalances is necessary in order to facilitate the application of countermeasures. This paper presents an algorithm for the simulation of large scale power system dynamics under unbalanced operating conditions. This algorithm finds potential application in the simulation of systems with abnormal loads such as arc furnace and traction, and also in the realistic simulation of unbalanced faults in bulk power transmission systems.     

Image smog restoration using oblique gradient profile prior and energy minimization

Removing the smog from digital images is a challenging pre-processing tool in various imaging systems. Therefore, many smog removal (i.e., desmogging) models are proposed so far to remove the effect of smog from images. The desmogging models are based upon a physical model, it means it requires efficient estimation of transmission map and atmospheric veil from a single smoggy image. Therefore, many prior based restoration models are proposed in the literature to estimate the transmission map and an atmospheric veil. However, these models utilized computationally extensive minimization of an energy function. Also, the existing restoration models suffer from various issues such as distortion of texture, edges, and colors. Therefore, in this paper, a convolutional neural network (CNN) is used to estimate the physical attributes of smoggy images. Oblique gradient channel prior (OGCP) is utilized to restore the smoggy images. Initially, a dataset of smoggy and sunny images are obtained. Thereafter, we have trained CNN to estimate the smog gradient from smoggy images. Finally, based upon the computed smog gradient, OGCP is utilized to restore the still smoggy images. Performance analyses reveal that the proposed CNN-OGCP based desmogging model outperforms the existing desmogging models in terms of various performance metrics.     

Shrinkage of Glass Soot Samples using Hot-Stage Scanning Electron Microscopy

Glass soot samples were generated by both flame hydrolysis and oxidation of silicon and germanium tetrachlorides. The shrinkage of these samples during sintering was determined accurately by hot-stage scanning electron microscopy. Shrinkage data were analyzed by an extension of Frenkel's theory of viscous sintering.     

Retardation of Cs+ and Cl− Diffusion Using Blended Cement Admixtures

Diffusion of cesium chloride through thin plates of hardened cement pastes was studied. Blast-furnace slag and condensed silica fume were used as blending admixtures in an attempt to retard the diffusion of cesium and chloride ions. The curing and diffusion temperatures were varied from 27° to 60°C, and the water/solid ratio was varied from 0.30 to 0.40. Results indicate that the cesium ion diffuses more slowly than the chloride ion in hardened cement paste systems. Blending admixtures caused a further reduction in diffusivity for both ions, which is important for preventing corrosion or restricting radionuclide transport.     

Environment sensitive impedance spectroscopy and dc conductivity measurements on NiWO4

Measurements of impedance spectroscopy and dc conductivity over the temperature range 300–1000K in atmospheres of dry and wet argon on antiferromagnetic NiWO4 are presented. The measured polycrystalline material was produced by a co-precipitation route. The conductivity was found to be sensitive to moisture over the temperature range 300–450 K. Impedance spectroscopy measurements separated the contributions of the bulk lattice and grain boundaries to the conductivity. These were separated over the temperature range 615–833 K by equivalent circuit modelling and an activation energy for the bulk lattice conductivity obtained. Conductivity measurements indicated that the compound is an intrinsic semiconductor and obeys the Arrhenius conductivity equation; =492.7 exp(–1.15 eV/kT)-1 m-1, above 625 K where K and T have their usual meaning.     

Mechanical and morphological investigation of virgin polyethylene and silver nanoparticle-loaded nanocomposites film: comprehensive analysis of kinetic models for non-isothermal crystallization

This research was accomplished to examine the mechanical, morphological and crystallization kinetics study of polyethylene/silver nanoparticles (Ag-NPs) nanocomposite films. In this research, low-density polyethylene (LDPE) nanocomposite films were prepared containing Ag-NPs using maleic-anhydride-grafted low-density polyethylene (LDPE-g-MAH) as a compatibilizer by the melt mixing process. From mechanical property evaluation, it is revealed that the LDPE/LDPE-g-MAH/Ag-NPs nanocomposite films showed decreased tensile strength as compared with virgin LDPE matrix. Thermal characteristics of the prepared virgin LDPE and its nanocomposite films were studied by differential scanning calorimetry (DSC). Comprehensive analysis of different kinetic models such as the Avrami and Mo model on non-isothermal crystallization kinetics was performed in order to correlate the rate of crystallization and its various kinetic parameters. Further, the macrokinetic equation as proposed by Malkin has been applied to describe the kinetics of crystallization in the light of the Avrami equation. Concerning virgin LDPE and Ag-NP-reinforced LDPE, the former shows primary crystallization, whereas the later exhibits both primary and secondary crystallization with varying Avrami exponents. Kinetic parameters are recognized, and confirm the influence of Ag-NPs on crystallization kinetics. X-ray diffraction spectroscopy and transmission electron microscopic analysis of the nanocomposite films were conducted to verify the dispersion of inorganic filler particles in the resulting hybrids.     

Luminescence properties of ZnO/TiO<Subscript><Emphasis Type="Bold">2</Emphasis></Subscript> nanocomposite activated by Eu<Superscript><Emphasis Type="Bold">3</Emphasis><Emphasis Type="Bold">+</Emphasis></Superscript> and their spectroscopic analysis

A new type of novel orange-red emitting Eu-doped ZnO/TiO ₂ nanocomposite phosphors have been synthesized by simple low temperature co-precipitation route. Structure and morphology of the prepared sample have been investigated using X-ray diffraction and field emission scanning electron microscopy (FESEM) techniques. XRD pattern confirmed the presence of both phases of ZnO and TiO ₂ simultaneously. The luminescence properties, such as photoluminescence (PL) excitation and emission spectra, Judd–Ofelt parameters, CIE colour coordinates and the dependence of luminescence intensity on the doping level were investigated. The luminescence spectrum characteristics of Eu ³⁺ ions have a strong dependence on Eu ³⁺ doping levels as well as ZnO/TiO ₂ ratio variations. The photoluminescence results indicate that these phosphors could be efficiently excited by near-ultraviolet radiation, which causes emissions in orange–red regions.