Study of electropolymerised polyaniline films using cyclic voltammetry, atomic force microscopy and optical spectroscopy

Electropolymerisation of polyaniline (PANI) has been investigated using cyclic voltammetry in aqueous bath. The effect of dopant on the structure, morphology & optical properties of electrodeposited PANI has also been studied using x-ray diffraction (XRD), atomic force microscopy (AFM), optical absorbance & luminescence spectroscopy. It is shown that the presence of a neutral salt (KI) in the deposition matrix imparts enhanced crystallinity to PANI films.     

A perspective on fast reactor fuel cycle in India

The growing energy needs of India can be fulfilled only by judicious mix of all the fuel resources. It is possible to achieve energy security and sustainability through the introduction of fast reactors in an expeditious manner and closing the fuel cycle. This approach is inevitable in view of the limited uranium resources in India. The Fast Breeder Test Reactor (FBTR) built by India uses mixed carbide as fuel and the 500 MW(e) Fast Breeder Reactor Project (PFBR), to be operational in 2010, will use mixed oxide as fuel. It has also been decided that fast reactors beyond 2020, with enhanced safety features and having better economy, will use metallic fuel. Having successfully operated FBTR with carbide fuels, we need to develop the fuel cycles for both the mixed oxide fuel in the near future and the metallic fuel expeditiously. The progress achieved so far and the plans for implementation are discussed in this paper.     

Towards Combining Probabilistic and Interval Uncertainty in Engineering Calculations: Algorithms for Computing Statistics under Interval Uncertainty, and Their Computational Complexity

In many engineering applications, we have to combine probabilistic and interval uncertainty. For example, in environmental analysis, we observe a pollution level x(t) in a lake at different moments of time t, and we would like to estimate standard statistical characteristics such as mean, variance, autocorrelation, correlation with other measurements. In environmental measurements, we often only measure the values with interval uncertainty. We must therefore modify the existing statistical algorithms to process such interval data.In this paper, we provide a survey of algorithms for computing various statistics under interval uncertainty and their computational complexity. The survey includes both known and new algorithms.     

New Family of Dielectric Materials in Ca–Y–Ti–Nb–O System Having Pyrochlore Type Structure

A new family of pyrochlore-type oxides in the Ca–Y–Ti–Nb–O system has been prepared by the conventional solid-state route. These compounds have a dielectric constant ( K ) in the range 27–92 and, further, the dielectric properties are found to be independent of frequency in the 100 Hz to 1 MHz range for all the compositions in the temperature range 30°–100°C. Their temperature coefficient of the dielectric constant is negative and in the range −80 to −612 ppm/°C. Rietveld analysis of the X-ray diffraction data establishes a cubic pyrochlore-type phase in the space group Fd3m (no. 227). A variation in the stoichiometry of the cations in the system does not change the pyrochlore-type structure.     

Intergranular corrosion damage evaluation through laser scattering technique

AISI type 316 austenitic stainless steel in sensitized condition was subjected to ASTM A262 practice A test (electrolytic etching in 10% ammonium persulphate at 1 A/cm²) for various durations from 10 s to 90 s. The different degrees of intergranular corrosion attack produced on these tested specimens were evaluated by laser scattering technique using a 1 mW He-Ne laser. The scattering intensity pattern of the laser beam incident on the specimen was acquired using a CCD camera and transferred to a computer for further analysis. The specular intensity of the scattering pattern and its full width at half maximum (FWHM) was calculated. The results indicated that the specular intensity decreased and the FWHM increased as the degree of IGC attack increased. A good correlation was found between the extent of IGC with the laser scattering parameters.     

Structural, Thermal, Linear and Nonlinear Optical Studies on New NLO Crystal∶DL-Threonium Trichloroacetate

Crystals of DL-threonium trichloroacetate (DLTTCA) was synthesized from an aqueous solution by slow evaporation technique. The grown crystals were characterized by X-ray diffraction, Fourier transform infrared spectroscopy, UV-Vis-NIR and SHG measurements. Vibrational structure of the crystal was elucidated from FTIR analysis and the hydrogen bond interactions were discussed in detail. The ultraviolet transparent cutoff falls at 212 nm. Thermal stability of the compound was also studied. The powder SHG efficiency of the compound was measured as 0.62 times to that of KDP.     

Investigation of charge transport, photo generated electron transfer and photovoltaic response of iron phthalocyanine (FePc):TiO2 thin films

We have investigated the blend of semiconducting materials (iron(II) phthalocyanine (FePc)) with TiO₂ nano crystals (NC) for photovoltaic application. The photo-induced electron transfer in composite of TiO₂ with FePc is studied by means of photoluminescence (PL) of the blend as well as photo-action spectra of the device. The quenching of the PL and occurrence of broad absorption have been interpreted as an electron transfer between an organic semiconductor and TiO₂ (NC) in excited state. Also, the effects of hole mobility and light intensity on the device properties have been analyzed. The observation of an increase in photocurrent of the device (consisting of TiO₂) is interpreted by the formation of an interconnecting network of FePc with TiO₂ nano particle and formation of bulk hetero junction between aluminum (Al) and indium tin oxide (ITO) electrodes. The electron transfer between FePc and TiO₂ is induced by photo excitation. The experimental results were explained with the help of a model that describes total current density as a function of injected carriers as donor/acceptor interface and contributed photo-generated current is due to the efficient dissociation of excitons.     

Charge generation and photovoltaic properties of hybrid solar cells based on ZnO and copper phthalocyanines (CuPc)

Photovoltaic properties and charge transfer process within the blend of p-type organic semi conducting copper phthalocyanine (CuPc) and inorganic n-type semiconductor zinc oxide (ZnO) nanoparticle have been determined. The photo-induced electron transfer mechanism in the composite thin film structure is predicted on the basis of its optical absorption behavior, photo-action spectra and photoluminescence (PL) characteristics, supported by current–voltage characteristics in dark and under illumination. An efficient electron transfer between donor (CuPc) and acceptor (ZnO) nanoparticle is explained by analyzing the photo-action spectra of the device and respective quenching of photoluminescence (PL) in composite thin film structure. The increase in photocurrent in composite blend based device is justified in terms of formation of bulk heterojunction between CuPc and ZnO nanoparticles. Also, the subsequent increase in photovoltaic response is ascribed to the formation of interconnecting network in between CuPc and ZnO nanoparticles. Our experimental results supports that photo-generation of charge carriers is induced by the production of excitons and their subsequent dissociation of into free carriers at ZnO–CuPc interface which is spread over the bulk region sandwiched between Al and ITO. Additionally, the optical and electrical properties of the composite blend based device have been discussed in details. The capacitance–voltage characteristics of the device support the formation of bulk heterojunction between CuPc and ZnO nanoparticles.     

Temperature dependence of the elastic moduli and damping for polycrystalline LiF-22% CaF2 eutectic salt

The Young's and shear moduli and damping were measured for as-cast polycrystalline LiF-22 (mol%) CaF₂ eutectic specimens as a function of temperature using the piezoelectric ultrasonic composite oscillator technique (PUCOT). The shear modulus decreased with increasing temperature from about 40 GPa at 295 K to about 30 GPa at 1000 K, while the Young's modulus decreased from about 115 GPa at 295 K to about 35 GPa at 900 K. These values are compared with those derived from the rule of mixtures using elastic moduli data for LiF and CaF₂ single crystals. It is shown that, while the shear modulus data agree reasonably well with the predicted trend, there is a large discrepancy between the theoretical calculations and the Young's modulus values, where this disagreement increases with increasing temperature. The reason for this discrepancy is unclear but several possibilities are examined and discussed. The effective activation energy for damping was determined to be about 0.21 eV/atom which was found to be in reasonable agreement with the activation energy for migration of anion vacancies in the CaF₂ phase.