Air-exposure effect on the resistivity of thin bismuth films

A survey of previous studies on vacuum deposited metal films shows that in high frequency measurements, explicit reference to the effect of air-exposure is not made. The present work on bismuth films (in-situ and air-exposed) at dc and rf frequencies, carried out mainly to study the air-exposure effect, shows that in-situ dc and rf and exposed rf all show nearly the same resistivity for thick continuous films. But air-exposed dc film resistances, when compared to in-situ dc resistances, show that the grain boundary reflection coefficient, R _gin Mayadas-Shatzkes model changes from 0·2 to 0·6. This is shown to be due to the grain boundary oxidation. The result is substantiated by rf measurements.     

Influence of oxygen on the guiding properties of V2O5-clad glass waveguide

An optical waveguide clad with V2O5 is proposed as a new type of oxygen sensor in ambient air. The presence of gas changes the light transmission (TE0-polarized mode) through the guide, due to the change in refractive index of the cladding which changes the effective index of the guide. O2 gas concentration is varied from a few (≈10) ppm to several percent (4%). Sensors exhibit the same sensitivity at a slightly elevated temperature. The increase in thickness of the cladding causes a reduction in sensitivity and increase in linearity. It is observed that the sensor exhibits the same performance using the static or incremental mode. This revised version was published online in November 2006 with corrections to the Cover Date.     

Temperature coefficient of resistivity of polycrystalline films

The expression for the temperature coefficient of the resistivity of a polycrystalline metal film is derived. A significant result is that the fast fall off of TCR of polycrystalline films with decreasing thickness can be explained if grain boundary scattering is taken into account.     

Effects of various ambient-aging processes in chopped and non-chopped optical films

The effects of various ambients on the non-chopped and chopped films of cryolite, MgF₂ and mixed cryolite-MgF₂, as measured by ellipsometer, are reported. The moisture decreases the refractive index whereas an increase is observed in air and other ambients. In all the ambient-aging the chopped films show smaller changes (nearly half) in refractive index than non-chopped films. Aging seems to be due to three main processes, a long-term adsorption-like surface reaction and two short-term reactions.     

A smart coating established with encapsulation of Zinc Molybdate centred nanocontainer for active corrosion protection of mild steel: release kinetics of corrosion inhibitor

In the current work smart coating of corrosion inhibitive nanocontainer was developed based on the encapsulation of ultrasonically synthesized Zinc Molybdate (ZM) nanoparticles. The ZM nanoparticles were doped ultrasonically with the layers of Myristic acid (MA), Polyaniline layer (PANI), benzotriazole layer and polyacrylic acid layer respectively to prepare layer by layer assembled nanocontainer. Results of XRD, PSD, FTIR, zeta potential and TEM analysis proves the successful formation of the layered structure of ZM nanocontainer particles. The release rate of benzotriazole at various experimental pH values was estimated using UV–vis spectroscopy. Different semi-empirical models were examined to predict the release mechanism of the benzotriazole. The corrosion inhibitive performance of ZM nanocontainers has been evaluated by incorporating 1wt % ZM nanocontainer in the epoxy based coating formulations and assessing by DC polarization measurement and Bode plots. The results from corrosion potential and Bode plots suggest the successful use of ZM nanocontainer in the multifunctional anticorrosion coating formulations.     

Studies on the dissolution of carbide fuels

The dissolution of carbide fuels was tried with the aid of various oxidants like H₂O₂, NaBiO₃, (NH₄)₂Ce(NO₃)₆, (NH₄)₂S₂O₈, and AgO in nitric acid medium. During the dissolution, the carbon dioxide liberated has been measured. Among the oxidants studied, H₂O₂ and NaBiO₃ appeared to be more effective for dissolution of carbides. 200–300 mg of sintered uranium carbide sample dissolved within 15 minutes in the presence of oxidants H₂O₂ or NaBiO₃. Mixed carbide sample (70%) was dissolved within 30 min, whereas plutonium carbide required more than one hour. From the resulting solutions uranium and plutonium could be determined by conventional redox methods. More than 97% of plutonium could be recovered and purified from the resulting carbide solutions by conventionally used anion exchange method.     

Effect of minute’s-scale aging on refractive index of chopped and non-chopped optical films

The refractive indices of non-chopped and chopped films of cryolite, MgF₂ and mixed cryolite-MgF₂, which is higher than the bulk value, measured using spectro-photometer, ellipsometer and Abeles method are observed to be higher than corres-ponding bulk values. Chopped films show a higher refractive index than non-chopped films. The electron diffraction study shows a more amorphous structure for the chopped films. The major part played by chop-time seems to be in increasing the initial minute’s-scale aging rather than settling of ad-atoms during chop-time. The observed dispersion curve shows that some unknown material other than water gives an important aging effect.     

Determination of plutonium and uranium in the same aliquot by potentiometric titration

A potentiometric titration method was developed for the determination of plutonium and uranium in the same aliquot in nitric acid medium. Plutonium was first determined by oxidation to Pu/VI/ by fuming with conc. HClO₄. Pu/VI/ formed was reduced to Pu/IV/ with known excess of Fe/II/ and the excess Fe/II/ was titrated with standard K₂Cr₂O₇ to a potentiometric end point. Uranium in the same solution was determined by reduction to U/IV/ with Fe/II/ in conc. H₃PO₄ medium and titrating U/IV/ formed with standard K₂Cr₂O₇ using the potentiometric end point detection technique. For the quantity of plutonium and uranium each in the range of 3–5 mg per aliquot a precision of ±0.2% and ±0.4%, respectively, was obtained.