http://nopr.niscair.res.in/handle/123456789/11676 Search the Channel search http://nopr.niscair.res.in/simple-search http://nopr.niscair.res.in/handle/123456789/11685 Title: Evaluation of (Bi_0.25Sb_0.75)₂ Te₃ charge transport parameters formed by hot press sintering <br/> <br/>Authors: Kavei, G <br/> <br/>Abstract: <i style="">P</i>-type (Bi_0.25Sb_0.75)₂Te₃ thermoelectric crystal has higher figure of merit <i>Z</i> than other stoichiometries. The prepared crystal of this compound is pulverized in a particle size ratio of 64% with mesh 80 (200 <img src='/image/spc_char/micro.gif' border=0> m²)/36% with a mesh of 60 (250 <img src='/image/spc_char/micro.gif' border=0> m²). The powder is sintered in a heat up to 350-500ºC under pressing load of 500 MPa (hot pressing). The method comprehension on transport parameters of the compound systematically investigated in nano-scale intrinsic structures by systems of X-ray diffraction, scanning electron microscopy and atomic force microscopy. The obtained data determined homogeneous structures for hot pressed samples along longitudinal and transversal directions. Thermal and electrical conductivities at optimum sintering temperature lead to a maximum <i>Z</i> value of around 1.92×10^-3 K^-1. <br/> <br/>Page(s): 161-167 Tue, 29 Mar 2011 22:58:59 GMT http://nopr.niscair.res.in/handle/123456789/11684 Title: Effect of connector density on shear capacity of reinforced masonry wallettes <br/> <br/>Authors: Mendoza-Pérez, J C S; Rico-García, E; Flores-Corona, L E <br/> <br/>Abstract: The aim of this study is to evaluate the effect of connector density on reinforced masonry wallettes. Firstly, the properties of bricks and mortar are determined. Six densities of connectors and unreinforced specimens are tested in diagonal compression. For each density at least seven probes are tested. Results show that no difference (<i style="">p</i> ≤ 0.05, means that results are only 5% likely or less) is found for connector density, concluding that connector density is not relevant to increase the shear capacity of reinforced masonry. However, all reinforced wallettes show a ductile failure. <br/> <br/>Page(s): 157-160 Tue, 29 Mar 2011 22:58:59 GMT http://nopr.niscair.res.in/handle/123456789/11683 Title: Ionic conduction and relaxation processes in melt compounded poly(ethylene oxide)-lithium perchlorate trihydrate-montmorillonite nanocomposite electrolyte <br/> <br/>Authors: Choudhary, Shobhna; Sengwa, R J <br/> <br/>Abstract: Polymer nanocomposite electrolyte (PNCE) films comprising complexes of poly(ethylene oxide) (PEO) and lithium perchlorate trihydrate (LiClO₄·3H₂O) filled with nano thickness platelets of montmorillonite (MMT) clay up to 20 wt% concentration of PEO are synthesized by melt compounding hot-pressed technique at 70^oC and 105^oC. Complex dielectric function, electric modulus, alternating current electrical conductivity and impedance behaviour of these PNCE films have been investigated in the frequency range 20 Hz to 1 MHz at ambient temperature. The direct current ionic conductivity of the PNCE films initially increases up to 2 wt% MMT loading and vary anomalously at higher concentrations. The PNCE films synthesized at 105^oC have ionic conductivity nearly one order of magnitude higher than that of synthesized at 70^oC. Relaxation times corresponding to electrode polarization and ionic conduction relaxation processes in the PNCE films are determined from the values of peak frequencies of the dielectric loss tangent and electric modulus loss spectra, respectively. Results confirm that the ionic conductivity of the PNCE films are governed by the PEO chain dynamics, electrode polarization and ionic conduction relaxation times, and also the structures of dispersed exfoliated/intercalated MMT nano platelets in PEO matrix and the material melt compounding temperature. <br/> <br/>Page(s): 147-156 Tue, 29 Mar 2011 22:58:59 GMT http://nopr.niscair.res.in/handle/123456789/11682 Title: Tool life performances, wear mechanisms and surface roughness characteristics when turning austenised and quenched AISI 52100 bearing steel with ceramics and CBN/TiC cutting tools <br/> <br/>Authors: Motorcu, Ali Riza <br/> <br/>Abstract: Tool life performances and wear mechanisms of various cutting tools such as mixed alumina ceramic (KY1615), coated ceramic (KY4400) and cubic boron nitride (CBN/TiC) are investigated experimentally under different cutting conditions in turning austenised and quenched AISI 52100 steels. Worn surfaces of the cutting tools are examined by scanning electron microscope (SEM) to find out the effective mechanism of wear. The surface roughness values are measured with surface profilometer and which cutting tool will provide a lower surface roughness values are investigated in the machining of hardened bearing steel AISI 52100. The experimental results showed that tool life decreased with increasing speed for all cutting tools. The longer tool life is obtained for the CBN/TiC cutting tool when machining the hardened AISI 52100 steel. However, the difference among the tool lives decreased considerably with decreasing the cutting speed. In addition, it is observed that the major wear form of the tools is the smooth flank wear for the CBN/TiC tool. However, crater and flank wear are observed for the KY1615 cutting tool while tool nose deformation is observed for the KY4400 cutting tool when machining the hardened steels. CBN/TiC and KY615 tool produced better surface roughness values of <i style="">R_a</i> than the KY4400 tools in all experimental conditions. On the surface roughness, low and medium cutting speed does not show a significant effect for all tools. But, <i style="">R_a</i> surface roughness values decreased with the highest cutting speed value. On the other hand; surface roughness value of <i style="">R_a</i> improved in the lowest depth of cut for all tools. <br/> <br/>Page(s): 137-146 Tue, 29 Mar 2011 22:58:59 GMT