Optical constants of CdS thin films prepared by spray pyrolysis

CdS thin films were prepared by spray pyrolysis techniques. Variable angle spectroscopic ellipsometry was used for optical constant calculations. Multiple angle measurements were taken in the most sensitive angle of incidence region. The sensitive regions of angle of incidence were obtained theoretically using 3-dimensional graph ofδψ andδΔ. Real partn and imaginary partk of the complex refractive index of the samples were calculated in the wavelength range 470–650 nm, taking into account surface roughness. Bruggeman’s effective medium approximation is used for analysis of the surface rough layer of the thin films.     

Photocrosslinking of azidated poly(vinyl chloride) coated onto plasticized PVC surface: Route to containing plasticizer migration

The migration of phthalate esters which are commonly employed for plasticizing poly(vinyl chloride) (PVC) is a significant problem in PVC-based medical devices as well as in packaging used for food stuffs and pharmaceuticals. Medical-grade PVC resin was treated with sodium azide in dimethylformamide (DMF) to prepare the azide polymer. The polymeric azide was coated onto the surface of plasticized PVC sheets by dipping in a solution of the polymer in tetrahydrofuran (THF). Crosslinking of the azide polymer was accomplished by irradiating the surface using a 125 W UV lamp for various lengths of time. Migration of the plasticizer di 2-(ethylhexyl phthalate) (DEHP) from coated and uncoated samples was examined in n-hexane at 30°C. It was found that 50–80% reduction in migration of DEHP could be effected from plasticized PVC in comparison with the controls in 72 h by this technique depending on the concentration of the coating solution, coating thickness, azide concentration, and irradiation dose. © 1995 John Wiley & Sons, Inc.     

Monte Carlo modeling of KAMINI

Monte Carlo modeling of the Kalpakkam Mini Reactor (KAMINI) has been carried out for the first time by using Monte Carlo code (MCNP4A) and continuous energy cross-sections. The safety control plate (SCP) drop experiment is simulated and the computed integral worth of the SCPs is compared with the measured value. The measured axial neutron flux profile and foil reaction rates in one of the in-core irradiation location and the foil reaction rates at the west beam port are also compared with the predicted results. The agreement between measurements and calculations is quite satisfactory. It is confirmed from the calculation and measurement that the north thimble is having nearly 10–20% higher neutron flux as compared to the south thimble depending on the exact elevation.     

Kinetics and mechanism of maleic acid hydroxylation by hydrogen peroxide. Part I: Formal kinetic studies by immobilized catalysis in a pseudo-homogeneous system

Formal kinetic studies of the epoxidation and hydroxylation of maleic acid by hydrogen peroxide (H₂O₂) have been carried out in the presence of a molybdenum salt, as catalyst, immobilized on Amberlite IRA-400 polymer resin in the chloride form. Immobilization of the catalyst on the resin was by a sorption process. Hydroxylation by immobilized catalysis afforded higher H₂O₂ selectivity and increased product yield in excess of 85%. Analysis of kinetic results shows that the reaction in the pseudo-homogeneous system follows the typical pseudo-zero order dependence on H₂O₂ concentration and is first order with respect to maleic acid concentration. However, the rate model developed for the immobilized catalyst fits the experimental data smoothly and parameter estimation using the Lineweaver–Burk plot fulfils the kinetic consistency tests without additional mathematical manipulation. The problem of activity and stability of the present catalyst was also investigated.     

Preparation of microstructured hydroxyapatite microspheres using oil in water emulsions

Hydroxyapatite (HAP) microspheres with peculiar spheres-in-sphere morphology were prepared by using oil-in-water emulsions and solvent evaporation technique. Ethylene vinyl acetate co-polymer (EVA) was used as the binder material. Preparation of HAP/EVA microspheres was followed by the thermal debinding and sintering at 1150°C for 3 h to obtain HAP microspheres. Each microsphere of 100–1000 μm was in turn composed of spherical hydroxyapatite granules of 2–15 (μm size which were obtained by spray drying the precipitated HAP. The parameters such as percentage of initial HAP loading, type of stabilizer, concentration of stabilizer, stirring speed and temperature of microsphere preparation were varied to study their effect on the particle size and geometry of the microspheres obtained. It was observed that these parameters do have an effect on the size and shape of the microspheres obtained, which in turn will affect the sintered HAP microstructure. Of the three stabilizers used viz. polyoxyethylene(20) sorbitan monopalmitate (Tween-40), sodium laurate and polyvinyl alcohol (PVA), only PVA with a concentration not less than 0.1 wt% showed controlled stabilization of HAP granules resulting in spherical microspheres of required size. Morphologically better spherical microspheres were obtained at 20°C. Increasing the stirring speed produced smaller microspheres. Smaller microspheres having size < 50 μm were obtained at a stirring speed of 1500 ±50 rpm. A gradual decrease in pore size was observed in the sintered microspheres with increase in HAP loading.     

Investigations on BaMnxTi1-xO3 ferroelectric film based MFS structure for non-volatile memory application

BaMn_xTi_1-xO₃ thin film on a silicon substrate has been prepared through the sol–gel spin coating process. The ferroelectric BaMn_xTi_1-xO₃ film shows the predominant perovskite ABO₃ structure for x?=?0.2 and 0.3 for the annealing temperature of 650 °C under nitrogen ambient. The metal contact on top and silicon substrate at the bottom of the film forms a Metal-Ferroelectric-Semiconductor capacitor structure. In BaMn_xTi_1-xO₃, the deposited film changes its structural and electrical properties as the concentration value of ‘x’ is changed. The crystal structure of the deposited film has been analysed by XRD. FESEM, EDS and XPS characterization of the film were carried out to discuss the change in the film structure with the change in the value of ‘x’. The Capacitor vs. Voltage (C–V), Current vs. Voltage (I–V), Charge vs. Voltage (Q–V), Endurance, PUND (Positive Up Negative Down) and dielectric study of the films are discussed. Memory window of 8.6 V and leakage current of few nA are obtained. The deposited ferroelectric film shows an endurance of?~?10¹¹ iteration cycle for the PUND pulse. The optimized doping molar concentration ‘x’ in BaMn_xTi_1-xO₃ shows favourable results for ferroelectric non-volatile memory application with a low cost fabrication method.

     

Fullerene lipids: Synthesis of C60 fullerence derivatives bearing a long-chain saturated or unsaturated triester system

Tris(hydroxymethyl)aminomethane was successfully esterified with saturated and unsaturated long-chain fatty acids. The resulting amino-triester intermediates were successively reacted with chloroacetyl chloride, sodium azide, and C₆₀ fullerene. Spectral evidence showed that the aziridine ring is joined to the junction of [6,6]-fused rings of the fullerene. The structures of the various C₆₀ fullerene derivatives bearing a long-chain saturated or unsaturated triester system were characterized by spectroscopic and spectrometric methods.     

Performance analysis of charge plasma based dual electrode tunnel FET

This paper proposes the charge plasma based dual electrode doping-less tunnel FET (DEDLTFET). The paper compares the device performance of the conventional doping-less TFET (DLTFET) and doped TFET (DGTFET). DEDLTEFT gives the superior results with high ON state current (I_ON ～ 0.56 mA/μm), I_ON/I_OFF ratio ～ 9.12 × 10¹³ and an average subthreshold swing (AV-SS ～ 48 mV/dec). The variation of different device parameters such as channel length, gate oxide material, gate oxide thickness, silicon thickness, gate work function and temperature variation are done and compared with DLTFET and DGTFET. Through the extensive analysis it is found that DEDLTFET shows the better performance than the other two devices, which gives the indication for an excellent future in low power applications.     

Fabrication and improved performance of poly(3‐hydroxybutyrate‐co‐3‐hydroxyvalerate) for packaging by addition of high molecular weight natural rubber

The packaging industry is searching for alternative materials to attain environmental sustainability. Poly(3‐hydroxybutyrate‐co‐3‐hydroxyvalerate (PHBV) is a semicrystalline polymer that meets this sustainability goal since it is bioderived and biodegradable. However, its brittle nature and relatively high water permeation and transmission rates make it unsuitable for packaging applications. In addition, PHBV has poor mechanical, thermal, and rheological properties above 160 °C, limiting its use in cast sheets and thermo‐formed packaging applications. To improve these properties, new blends of PHBV with high molecular weight natural rubber at 5, 10, 15, and 25% by weight were fabricated, and physico‐chemical properties of the blends were characterized. The rubber in the blends aided in the following: increased thermal stability since the complex viscosities of the blends were improved by one log over pure PHBV at 170 °C, created more uniform melting peaks attesting to improved homogeneity, decreased water permeation to a level similar to that of traditional thermoplastics; increased the elongation at break, and stabilized the Young's modulus. Therefore, these blends can potentially be used in‐place of traditional, petroleum‐based thermoplastics in cast sheets and thermoforms. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43937.