Rapaka S C Bose; L Rangaraj; Abanti Nag
Abstract
The p-type thermoelectric material Ca3Co4O9 were synthesized by the sol-gel synthesis in the presence of complexing agent of citric acid and dispersant of polyethylene glycol 400, and followed by the uni-axial hot-pressing (HP) technique. Observation by X-ray diffraction revealed that the formation of ...
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The p-type thermoelectric material Ca3Co4O9 were synthesized by the sol-gel synthesis in the presence of complexing agent of citric acid and dispersant of polyethylene glycol 400, and followed by the uni-axial hot-pressing (HP) technique. Observation by X-ray diffraction revealed that the formation of phase pure sample on calcination at 1073 K for 4 h. Scanning electron microscopy indicated that the significant enhancement of the grain growth through HP technique. The density of the sintered pellets increased with an increase of applied pressure. The electrical resistivity was greatly reduced with an increase of the applied pressure, whereas the Seebeck coefficient was little increased with an increase of the applied pressure. As a result, the pellet treated by the HP technique under the condition of 1098 K, 25 MPa and 30 min showed a maximum power factor of about 498 μWm-1K-2 at 950K. Copyright © 2017 VBRI Press.
Rabesh Kumar Singh; Anuj Kumar Sharma; Amit Rai Dixit; Arun Kumar Tiwari; Amitava Mandal
Abstract
Health and environmental concerns about the use of excessive conventional cutting fluids during conventional machining has led to the development of a new type of cutting fluid. Inefficient disposal of industrial cutting fluids during wet machining also reduces the use of conventional cutting fluid. ...
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Health and environmental concerns about the use of excessive conventional cutting fluids during conventional machining has led to the development of a new type of cutting fluid. Inefficient disposal of industrial cutting fluids during wet machining also reduces the use of conventional cutting fluid. Nano-material mixed cutting fluids have shown superior thermal properties and tribological properties. In the present work, different nanofluids are prepared by suspension of Titanium dioxide (TiO2), Silicon oxide (SiO2) and Aluminum oxide (Al2O3) nanoparticles in vegetable oil and water-based emulsion at room temperature in different volumetric concentrations. The viscosity and density of the developed nanofluids are measured at different temperatures for different nanoparticle volumetric concentrations. From the experimental results, it has been found that with the increase of nanoparticle concentration in base fluid, enhanced the its viscosity and density. Furthermore, addition of nanoparticles at 25 ºC enhances viscosity more compared to its addition at higher temperatures. For an increase of concentration from 0.25% to 3%, enhancement in viscosity of Al2O3, SiO2 and TiO2 nanofluids is observed as 41.6%, 43.75% and 35.55%, respectively, while for higher temperatures almost constant improvement of 25%, 24% and 30% is observed for Al2O3, SiO2 and TiO2 nanofluids, respectively. The viscosity and density of three different nanofluids are also compared. Results showed that newly prepared Al2O3 based nanofluid exhibits better properties than TiO2 and SiO2 based nanofluids. Copyright © 2017 VBRI Press.