Hemlata J. Sharma; Bhaskar M. Bahirwar; Subhash B. Kondawar
Abstract
Metal oxide nanofibers showed keen interest in chemical gas sensing due to their unique chemical and electrical properties at operating temperature more than 200 o C. Their sensitivity can be improved at low operating temperature closed to room temperature by using conducting polymers. In this paper, ...
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Metal oxide nanofibers showed keen interest in chemical gas sensing due to their unique chemical and electrical properties at operating temperature more than 200 o C. Their sensitivity can be improved at low operating temperature closed to room temperature by using conducting polymers. In this paper, Al doped tin oxide/polyaniline composite nanofibers detected H2 molecules at room temperature. A simple versatile electrospinning technique is used for the fabrication of Aluminium (Al) doped (tin oxide) SnO2 nanofibers and polyaniline was encapsulated using chemical oxidative polymerization (COP) of aniline monomer using ammonium persulfate as redox initiator. The structure and morphology of Al-doped SnO2/PANI composite nanofibers were investigated by SEM-EDX, UV-VIS and XRD spectroscopy. Structural changes of SnO2/PANI crystal due to the incorporation of Al 3+ ions have been explained. Al-doped SnO2/PANI composite nanofiber is very much selective towards H2 gas molecules in terms of high sensitivity, rapid response and recovery around room temperature compared to that of Al-doped SnO2. The present sensing mechanism systematically explained the existence of PN junction which is formed by p-type and n-type semiconductors in Al-doped SnO2/PANI hybrid composite material.
Mehdi D. Esrafili; Parisa Nematollahi
Abstract
In this letter, the mechanisms of the oxygen reduction reaction (ORR) on Si- and Al-doped graphene have been investigated to understand the effect of doped graphene on the ORR and predict details of ORR pathways. Density functional theory (DFT) calculations were used to achieve the true mechanism pathways ...
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In this letter, the mechanisms of the oxygen reduction reaction (ORR) on Si- and Al-doped graphene have been investigated to understand the effect of doped graphene on the ORR and predict details of ORR pathways. Density functional theory (DFT) calculations were used to achieve the true mechanism pathways of ORR on the surfaces. Also, free energy diagrams for the ORR were constructed to provide the stability of possible intermediates in the electrochemical reaction pathways. At first stage, the adsorption of O2 molecule on both surfaces was studied with two possible configurations: atop (most stable) and bridge with the Eads of -60.6 and -72.4 kcal/mol, while for bridge site they were about -48.9 and -60.4 kcal/mol, respectively. Then, the most stable configuration (atop) was selected and the pathways formed after the adsorption of four atomic hydrogen to O2 molecule for both surfaces. These mechanisms were similar in both Si- and Al- doped graphene but there was a little difference in the obtained intermediates formed in each surface. In each pathway, the O2 dissociation reaction was neglected because it was unlikely to occur due to the high activation energy (> 45 kcal/mol). The results of this study show an easy and economic way to obtain Si- and Al-doped graphene as a non-metal catalyst for ORR at the cathode electrode in fuel cells.
Virupaxi Auradi; Shivaputrappa Amarappa Kori
Abstract
The present work aims at evaluating the grain refining performance of Al-7Ti master alloys with different microstructures on Al-7Si alloys. Al-7Ti master alloys were prepared in an induction furnace by salt route involving the reactions between K2TiF6 and molten Al. Reaction temperatures chosen for producing ...
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The present work aims at evaluating the grain refining performance of Al-7Ti master alloys with different microstructures on Al-7Si alloys. Al-7Ti master alloys were prepared in an induction furnace by salt route involving the reactions between K2TiF6 and molten Al. Reaction temperatures chosen for producing Al-7Ti master alloys were 800 o C, 900 o C and 1000 o C while reaction time was kept constant at 60min. These indigenously prepared master alloys at different temperatures were characterized by chemical analysis; particles size analysis, XRD and SEM/EDX microanalysis. Results of particle size analysis suggest that mean size of Al3Ti intermetallic particles in Al-7Ti master alloys were increased from 15.8µm to 22.4 µm as temperature is increased from 800 o C-1000 o C. SEM/EDX studies revealed fine blocky morphology, large blocky and flaky/petal morphologies of Al3Ti intermetallic particles in Al-7Ti master alloys at 800 o C, 900 o C and 1000 o C respectively. Results of grain refinement studies suggest that Al-7Ti master alloy prepared at reaction temperature of 800 o C shows better grain refinement performance on Al-7Si alloy when compared to the Al-7Ti prepared at 900 o C and 1000 o C. In future, the influence of reaction time on microstructural and grain refining behaviour of Al-7Ti master alloys will be evaluated and the performance of these Al-7Ti master alloys will be compared with Al-B and Al-Ti-B master alloys.
Gurpreet Kaur; Anirban Mitra; K.L. Yadav
Abstract
Al-doping of 1.5% by weight, in ZnO (Al:ZnO), thin films are deposited on glass substrates at temperature 400 °C and varying oxygen gas pressure (PO2) from 1.33 Pa to 5.32 Pa via Pulsed Laser Deposition (PLD) technique. The single crystalline nature of the thin films is confirmed from the X-ray diffraction ...
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Al-doping of 1.5% by weight, in ZnO (Al:ZnO), thin films are deposited on glass substrates at temperature 400 °C and varying oxygen gas pressure (PO2) from 1.33 Pa to 5.32 Pa via Pulsed Laser Deposition (PLD) technique. The single crystalline nature of the thin films is confirmed from the X-ray diffraction (XRD) pattern. The evaluated crystallite size is found to be <15 nm. Atomic Force Microscopy (AFM) study reveals the columnar grain formation in the thin films, with low surface roughness. The surface morphology of the grown thin films is significantly affected by PO2. Optical measurements depict that the thin films are highly transparent in the visible region with transmittance up to 80%. The optical band gap calculated from Tauc’s plot evinced that Al-doping results in band edge bending in Al:ZnO thin films, a red shift in the band gap is observed with increase in PO2 that is due to the contributing electrons from oxygen ions. Photoluminescence (PL) spectra of films indicate the visible emission peaks originating from defect states. Optical properties of the thin films confirm their applicability for optoelectronic devices. The room temperature, current-voltage (I-V) plots indicate low resistivity in the thin films ~ 10 -2 (Ω-cm).
N. B. Dhokey; V. A. Athavale; N. Narkhede; M. Kamble
Abstract
Aluminium powder metallurgy (Al-PM) alloys are finding promising applications in many areas such as household appliances, automotive vehicles and many other allied sections where reduction in weight is the primary constraint. In the proposed research, two binary alloy systems Al-X were studied by mixing ...
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Aluminium powder metallurgy (Al-PM) alloys are finding promising applications in many areas such as household appliances, automotive vehicles and many other allied sections where reduction in weight is the primary constraint. In the proposed research, two binary alloy systems Al-X were studied by mixing elemental powders of Aluminium (Al), Tin (Sn) and Magnesium (Mg). Two types of mixing techniques were followed. In one case, elemental powders were blended in a mechanical mixer without any mixing media (A) and another case powders were blended with ball to powder ratio of 10:1 (B). The content in binary premix was varied from 0.4 to 0.8 % Sn (by wt.) and 0.5 to 2 % Mg (by wt.) with base of Aluminium. The blended powders was compacted at 450 MPa followed by sintering in ultra high purity nitrogen atmosphere in tubular sintering furnace at 600oC. The mixing technique B showed significant influence on increase in hardness by two-fold and reduction in dimensional growth.