http://nopr.niscpr.res.in/handle/123456789/24324 2026-10-08T23:18:40Z http://nopr.niscpr.res.in/handle/123456789/24470 Title: Spectroscopic studies on curing of novolac epoxy resin—Polyamide and polyamine hardener systems in presence of a polysulphide Authors: Makashir, P S; Agawane, NT; Mahajan, R R; Agrawal, J P Abstract: Novolac epoxy resins have recently been reported for inhibition of hydroxy terminated polybutadiene (HTPB) based composite propellants and their elongation has been improved by the incorporation of some flexibilizers. In the present investigation, curing behaviour of a novolac epoxy resin (Dobeckot E4) by hardeners (polyamide EH 411 and polyamine H 758) in conjunction with a polysulphide flexibilizer has been studied using infrared (IR) spectroscopy. It is observed that the rate of curing of Dobeckot E4 by hardeners such as hardener EH411 and hardener H 758, is higher as compared to polysulphide flexibilizer LP-33. Further, rate of curing of epoxy resin by hardeners such as EH411 and H758 enhances in the presence of flexibilizer LP-33. The curing studies by infrared (IR) spectroscopy suggest that hardeners EH41l/H758 react with epoxy ring of epoxy resin and as a result, epoxy ring opens while curing. Similarly, -SH group of polysulphide flexibilizer LP-33, reacts with the epoxy ring of resin and opens it as curing progresses and thus enhances the rate of curing of epoxy resin in conjunction with hardeners EH411/H758. This is also supported by the gel time and exotherm peak temperature data. Page(s): 381-385 2001-12-01T00:00:00Z http://nopr.niscpr.res.in/handle/123456789/24468 Title: Optical waveguiding in vacuum deposited polyaniline thin films Authors: Sharma, Sudhir Kumar; Sharma, V K; Kapoor, A; Misra, S C K; Tripathi, K N Abstract: Polyaniline thin films prepared by vacuum deposition of polyaniline powder, have been found to exhibit good optical waveguiding properties. The waveguide parameters, refractive index, propagation loss and depth, are found to be strongly affected by doping of these thin films. A detailed study of the optical absorption, effective refractive index, optical propagation losses and propagation depth for these thin films has been carried out using the integrated optics techniques.Vacuum deposited polyaniline thin film planar optical waveguides exhibit low optical attenuation and have optical refractive index 1.590 and excellent transmission in the wavelength range 350-650 nm, which make this polymer promising for integrated optical devices. Page(s): 377-380 2001-12-01T00:00:00Z http://nopr.niscpr.res.in/handle/123456789/24465 Title: Spectroscopic investigation of BiSeI, SbSeI compounds and BiSbS_xSe_l-xI solid solutions Authors: Kanchana, G; Arivuoli, D Abstract: The compounds such as SbSeI, BiSeI and solid solutions of BiSbS_xSe_1-xI (x = 0.2 to 0.8 mol fractions) are grown from vapour by chemical vapour transport method. The IR and Raman spectra were recorded in the range 600-50 cm^-1. The IR spectra reveal that the frequency modes are sensitive to selenium substitution and the Raman spectra show that the bands below 200 cm^-1 are halogen sensitive. Page(s): 373-376 2001-12-01T00:00:00Z http://nopr.niscpr.res.in/handle/123456789/24463 Title: Microwave related properties of fritless Ag thick film metallisation and effect of long-term air exposure Authors: Puri, Vijaya; Rane, S B Abstract: Investigations on the laboratory- formulated fritless silver thick film metallisation for use at microwave frequencies is reported here. The reflectometer method has been used to measure the microwave (8-18 GHz) transmittance and reflectance of these films deposited by screen printing onto 96% alumina substrates. The effects of firing temperature, composition and long term air exposure on the microwave properties and d.c. resistivity are also reported. In the X-band frequency, composition and firing temperature-dependent transmittance and reflectance of metallisation are obtained whereas at Ku-band, the above properties are to a large extent independent of these factors. The microwave conductivity as well as the d.c. resistivity are found to increase on aging. The results indicate the utility of these fritless Ag thick film metallisation up to 18 GHz. Firing temperature-independent properties provide substantial energy saving and increased furnace life as the films fired at 800°C compare well with those fired at 900°C especially at higher frequencies. Page(s): 366-372 2001-12-01T00:00:00Z