http://nopr.niscair.res.in/handle/123456789/11200 Search the Channel search http://nopr.niscair.res.in/simple-search http://nopr.niscair.res.in/handle/123456789/11210 Title: Dielectric properties of Pb_0.5Ba_0.5TiO₃ ferroelectric ceramics <br/> <br/>Authors: Roy, M; Dave, Praniti; Barbar, Shiv Kumar; Jangid, Sumit; Bala, Indu <br/> <br/>Abstract: The polycrystalline samples of pure and modified lead titanates of general formula Pb_1-XBa_XTiO₃ (X= 0.00, 0.5) have been prepared by high temperature solid state reaction technique using the high purity oxides and carbonates. Preliminary structural studies revealed that the basic structure of PbTiO₃ remains unaltered by incorporation of 50% Ba on the A-cation sites of PbTiO₃. Morphological changes have been obtained by scanning electron microscopy. The measured bulk density is comparable with that of the theoretical value. The dielectric constant (relative permittivity) of the compounds has been measured as a function of frequency (5 Hz-13 MHz) and temperature (RT to 400^oC). The phase transition temperature has been reduced from 490^oC in the pure compound to 352^oC in the 50% Ba substituted compound. <br/> <br/>Page(s): 86-90 http://nopr.niscair.res.in/handle/123456789/11209 Title: Age hardening behaviour of 2014 Al alloy-SiC composites: Effect of porosity and strontium addition <br/> <br/>Authors: Badkul, Anshul; Jha, Nidhi; Mondal, D P; Das, S; Yadav, M S <br/> <br/>Abstract: The aging characteristics of 2014 aluminum alloy-SiC composites with and without strontium addition are studied and compared with that of 2014 Al-cenosphere syntactic foam (Al-Cenosphere composite) and 2014 alloy-SiC composite foam in order to examine the effect of strontium addition and porosity on aging behavior. It is observed that primary peak aging time of strontium added 2014 Al-SiC composite is same to that of 2014 Al-SiC composite. But, strontium added 2014 Al-SiC composite shows secondary ageing unlike that of 2014 Al-SiC composite. Again, 2014 Al-SiC composite foam and cenosphere added syntactic foam get peak aged almost at same time, But relatively at slower rate than dense composites. It is observed that the strontium added composite also showed a peak at 10 h for secondary hardening due to delayed precipitation of AlSr₃. <br/> <br/>Page(s): 79-85 http://nopr.niscair.res.in/handle/123456789/11208 Title: Studies on PP/SBS blends with and without nanoclay <br/> <br/>Authors: Shashidhara, G M; Devi, S H Kameshwari <br/> <br/>Abstract: Blends of PP and SBS with and without nanoclay are prepared using twin screw extruder. The nanoclay content and SBS are varied from 1-3% and 5-15%, respectively. Effects of SBS and nanoclay content on tensile, notched impact strength, heat deflection temperature, hardness and melt flow index are studied. The DSC study shows decrease in the degree of crystallinity of PP/SBS blends with increase in SBS content up to 10% loading but shows an increasing trend at 15% loading. An attempt has been made to correlate tensile properties and various crystallization parameters such as peak crystallization temperature (<i style="">T</i>_p), onset temperature of crystallization (<i style="">T</i>_onset), initial slope of exotherm (<i style="">S</i>_i), the quantity (<i style="">T</i>_c-<i style="">T</i>_P), area under the exotherm (<i style="">A</i>/<i style="">m</i>) and width at half height (Δ<i style="">W</i>). We found that the stress at break, tensile modulus and yield stress have good correlation with Δ<i style="">W</i>. The yield stress and stress at break are also influenced by <i style="">X</i>_cwhile strain at break is better correlated to <i style="">T</i>_p which is a function of cooling rate. Yield strain seems to have strong dependency on Δ<i style="">W</i>and <i style="">X</i>_c. The role of SBS as nucleating agent for PP crystallization has been established. Incorporation of 3 phb clay to a 90/10 PP/SBS blend results in an increase in <i style="">G</i>’ at 30^oC. This indicates that the SBS rubber is likely to have interacted molecularly with clay particles. <br/> <br/>Page(s): 69-78 http://nopr.niscair.res.in/handle/123456789/11207 Title: Use of pumice fine aggregate as an alternative to standard sand in production of lightweight cement mortar <br/> <br/>Authors: Degirmenci, Nurhayat; Yilmaz, Arin <br/> <br/>Abstract: The purpose of this study is to evaluate the possibility of using granulated pumice as an alternative to fine aggregate in production of lightweight cement mortar. The cement/pumice fine aggregate ratio is 1:3 for pumice aggregate mortar. The water content is determined by flow table test. Compressive and flexural strength, freeze-thaw resistance, sulfate resistance, water absorption and dry unit weight of the mortars are determined. Mortar using 100% pumice as fine aggregate developed strength in excess 12 MPa and had an oven dry density of 1140-1146 kg/m³would satisfy the requirements for lightweight mortar and<b style=""> </b>it can be used as in cast in place walls, load bearing and non-load bearing structures. Pumice aggregate mortar is about 50% lighter than Portland cement control mortar due to the replacement of comparatively heavier standard sand by lighter pumice aggregate. The pumice aggregate mortar exhibits a higher frost resistance due to the existence of voids in pumice aggregate. Pumice aggregate mortar showed better performance showing higher residual strength at high temperatures compared Portland cement mortar. The residual compressive strength reduction of pumice aggregate mortar is higher than that of Portland cement mortar exposed to freeze-thaw cycles. The use of pumice aggregate as sand provides the resistance to sulfate attack. <br/> <br/>Page(s): 61-68