http://nopr.niscpr.res.in/handle/123456789/42399 Sun, 11 Oct 2026 22:32:40 GMT 2026-10-11T22:32:40Z http://nopr.niscpr.res.in/handle/123456789/42407 Title: Microstructure and EDS analysis on titanium/aluminium dissimilar laser welded joint subjected to age hardening Authors: Kalaiselvan, K; Elango, A; Nagarajan, N M Abstract: Laser beam welding of titanium and aluminium alloy is very much needed for aerospace and automotive industries due to its high strength and light weight. The dissimilar welding is having a bearing on high temperature at the weldment and grain coarsening may cause if thermal cycle is not checked. In order to maintain good weld joint properties, phase transformation during rapid thermal cycles is required. Such cycles occur during welding of titanium/aluminium dissimilar sheets and age hardening heat treatment after welding. Titanium and aluminium alloys are sensitive to heat due to their difference in melting temperatures. This may cause changes in microstructures in weldment. The aim of this study is to analyse the changes in titanium (TI6AL4V) and aluminium (AA2024) alloy thin sheets welded joint using SEM and EDS studies before and after age hardening heat treatment. From the results, it is observed that laser beam focusing from titanium side gives well refined age hardened structure and EDS reveals that the bond is metallurgical one. Page(s): 377-382 Thu, 01 Dec 2016 00:00:00 GMT http://nopr.niscpr.res.in/handle/123456789/42407 2016-12-01T00:00:00Z http://nopr.niscpr.res.in/handle/123456789/42406 Title: Grain refining mechanism of ZnO particles on magnesium alloys Authors: Liu, Xuan; Zhang, Zhiqiang; Hu, Wenyi; Le, Qichi; Bao, Lei; Lu, KaiKai Abstract: Grain refining of ZnO particles on magnesium alloys has been investigated by suction casting. Based on the experimental and thermodynamic data available, ZnO particles would be converted into the solute Zn in Mg melt. However, the ZnO particles have a slightly stronger grain refining potency than Zn. The grain refining efficiency of ZnO particles is mainly attributed to the restricting effect of Zn solute and in situ produced MgO particles as potent nuclei. Meantime, the large amount of reaction heat may cause intensive micro convection and mass transfer to eliminate the solute accumulation between existed grains, which could improve the nucleation rate. Page(s): 383-388 Thu, 01 Dec 2016 00:00:00 GMT http://nopr.niscpr.res.in/handle/123456789/42406 2016-12-01T00:00:00Z http://nopr.niscpr.res.in/handle/123456789/42405 Title: Analytical and experimental investigation of particulate filled polymer composites with enhanced thermal conductivity Authors: Banjare, Johan; Agrawal, Alok; Sahu, Yagya Kumar; Satapathy, Alok Abstract: The present study aims at investigating an opportunity of enhancing heat conduction ability of a typical particulate filled polymer composite. A mathematical correlation for evaluating the effective thermal conductivity (<i>k_eff</i>) of polymer composites filled with elliptical shape particles is developed. To validate this model, high thermal conductivity aluminium powders were incorporated in the epoxy matrix for the first set of polymer composites whereas, for the second set, an industrial waste, i.e., red mud is taken as a filler material. Simple hand lay-up technique is used for fabrication purpose.Thermal conductivities of these fabricated composite samples are determined experimentally using the Unitherm™ Model 2022 tester which works on the principle of double guarded heat flow meter method according to ASTM E1530 standard. Measured values are then compared with the values obtained from the proposed mathematical model and also with some already existing correlation. It has been observed that the results obtained from the proposed model fits well with the experimental data. An improvement of about 260% in the value of <i>k_eff</i> is recorded with addition of 25 vol% of aluminium filler in epoxy resin whereas with similar loading of red mud, it is noticed that <i>k_eff</i> increases by about 200%. Apart from this thermal investigation, physical properties like density and void content along with morphological behaviour of the fabricated composites are also reported. Page(s): 389-398 Thu, 01 Dec 2016 00:00:00 GMT http://nopr.niscpr.res.in/handle/123456789/42405 2016-12-01T00:00:00Z http://nopr.niscpr.res.in/handle/123456789/42404 Title: Characterization of SiO₂ nanoparticles dispersed (PVA–PEO) blend based nanocomposites as the polymeric nanodielectric materials Authors: Choudhary, Shobhna Abstract: Polymer nanocomposite (PNC) films consisting of poly(vinyl alcohol) (PVA) and poly(ethylene oxide) (PEO) blend matrix dispersed with nanosize particles of silicon dioxide (SiO₂) [i.e., (PVA-PEO)–<i>x</i> wt% SiO₂, where <i>x </i> is 0, 1, 3 or 5] have been prepared by aqueous solution-cast method. The structural properties of the PNCs are characterized by X-ray diffraction measurements, which confirm the semi-crystalline structures of these materials. The complex dielectric function, alternating current electrical conductivity, electric modulus and impedance spectra of the PNC films have been investigated in the frequency range 20 Hz to 1 MHz by employing the dielectric relaxation spectroscopy. Effects of SiO₂ concentrations and temperatures on the dielectric permittivity, electrical conductivity and structural dynamics of these PNC materials have been explored. The dielectric relaxation mechanism of the PVA–PEO blend based these materials is mainly governed by the PEO chain segmental dynamics. The relaxation times and conductivity activation energies of the PNC films are determined from the Arrhenius plots. Dielectric and electrical parameters values reveal the suitability of these materials as low-permittivity nanodielectrics for the radio frequency electric field. Page(s): 399-410 Thu, 01 Dec 2016 00:00:00 GMT http://nopr.niscpr.res.in/handle/123456789/42404 2016-12-01T00:00:00Z