Showing papers by "North Eastern Regional Institute of Science and Technology published in 1998"

Laser Raman Study of Terepthalylidene-bis-p-n-Decylaniline (TBDA)

Abstract: The Raman spectra of Terepthalylidene-bis-p-n-declyaniline (TBDA), have been recorded as a function of temperature in the temperature range from 55.0°C (solid) to 199.0°C (isotropic liquid) in the 1100–1200cm−1 and 1520–1650cm−1 regions. The precise values of peak positions, integrated intensities and linewidths of some selected Raman bands have been obtained by deconvoluting the bands. The changes in the molecular alignment and its effect on inter/intra molecular interactions at two particular phase transitions viz., solid-smectic G (K-SG ) and smectic I-Smectic C (SI-Sc ) have been discussed on the basis of variation in the Raman spectral parameters with temperature. From detailed considerations, it is inferred that the increased orientational/vibrational freedom of long alkyl chain on the core is responsible for major spectral changes at the K-SG transition while the changes in the intramolecular interactions of the core part with increased fluidity, is responsible for spectral anomalies at th...

Universal behaviour of ac susceptibility of granular (Bi1.2Pb0.3)Sr1.5Ca2Cu3Oy superconductors

Abstract: Temperature and ac field variations of ac susceptibility were measured on a cylindrical sample of the 110 K phase of the Bi–Sr–Ca–Cu–O system, prepared by the uniaxial press-sintering technique. It is shown that both the temperature and the field variation of the susceptibility could be determined using a single parameter δ , which is a function of full penetration field and the amplitude of the ac field. The temperature variation of the critical current density and the irreversibility temperature were estimated from the analysis of temperature and field variations of δ obtained from the experimental data.

Influence of water absorption on poly–ethylene oxide-based polymer electrolytes complexed with ammonium, sodium and magnesium perchlorates

Abstract: The influence of water absorption on polyethylene oxide and its complexes with NH4ClO4, NaClO4 and Mg(ClO4)2 (for O/M=10 and 3) has been studied. A quantitative estimation of water absorption kinetics has been carried out. The changes in microstructure and thermal behaviour due to water absorption have been studied using X-ray diffraction and thermogravimetric/differential thermal analyses. The electrical conductivity of different films has been measured as a function of relative humidity and explained in terms of the generation of free mobile ions due to water absorption. © 1998 Chapman & Hall

Simultaneous Determination of Cobalt and Nickel in Standard Alloys, Environmental and Biological Samples by Differential Pulse Polarography After Preconcentration of Their Morpholine-4-carbodithioates on Microcrystalline Naphthalene or Morpholine-4-dithiocarbamate-CTMAB-naphthalene Adsorbent

Abstract: A highly sensitive, selective, simple and economical differential pulse polarographic (DPP) method has been developed for the simultaneous determination of trace amounts of cobalt and nickel in standard alloys, biological and environmental samples. The morpholine-4-carbodithioates of cobalt and nickel are quantitatively adsorbed on microcrystalline naphthalene in the pH range 3.5–9.0 and 4.1–9.5 respectively and determined simultaneously with DPP after desorption with 10 ml of 1 M HCl. These metals can alternatively be adsorbed on morpholine-4-dithiocarbamate-cetyltrimethylammonium bromide-naphthalene (MCDT-CTMAB-naphthalene) adsorbent packed in a column and determined similarly. The detection limits are 0.15 ppm for cobalt and 0.20 ppm for nickel at minimum instrumental settings (signal-to-noise ratio=2). The linearity is maintained in the concentration ranges, cobalt 0.6–12.0/0.6–7.0 and nickel 1.0–20.0/1.0–12.0 ppm with a correlation factor of 0.9996 and relative standard deviations of 1.2 and...

A simple household method for the removal of iron from water

Abstract: With a view to developing a simple household method for removing iron from water, a laboratory study was undertaken to assess the potential of potassium permanganate, ceramic candle filter, or a combination of the two in removing iron from iron-spiked tap water. Batch tests using potassium permanganate with 5 min slow mixing and 2.5 h settling showed an iron removal in the range of 79–99% for the water samples tested (pH 6.0–10.0; initial iron concentration 3.5–10.0 mg/L). The optimum dose of potassium permanganate varied between 1.6 and 8.0 mg/L. Removal was generally higher at higher pH. Tests with a ceramic candle filter showed that, used alone, it could not remove iron efficiently; removal ranged between 7 and 20%. However, when water mixed with potassium permanganate (for 5 min) was fed into the filter, a high iron removal (91–99%) was observed. An Escherichia coli challenge test showed improved bacteria removal in presence of potassium permanganate. The results of the study indicated that a combination of potassium permanganate and candle filter can be used effectively for the household removal of iron in the rural areas of developing countries.

Converging Spherical Detonation Waves.

Abstract: The problem of converging spherical detonation waves propagating through a gas with varyingdensity is discussed. By neglecting the effect of variation of Q on the similarity exponent, both analytical and numerical solutions for motion of the detonation front have been obtained and arepresented in graphical form.