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Cr-doped ZnAl2O4: Microwave solution route for ceramic nanoparticles from metalorganic complexes in minutes
No full textA combination of microwave irradiation and metalorganic precursors in solution was used for the synthesis of Cr:ZnAl2O4 nanoparticles with high yields (similar to 92%). Though the spinel phase is formed after similar to 40minutes, 60minutes of microwave irradiation was required for the complete transformation of precursors into the spinel. The as-prepared material is nanocrystalline and phase-pure and was subjected to annealing in air at different temperatures. Annealing improved the crystallinity, and the material turned pink at 1200 degrees C. The structural and optical properties were investigated by XRD, HR-TEM, FE-SEM, FT-IR, diffuse reflectance spectroscopy, and photoluminescence spectroscopy. The two bands in the excitation spectra (400 and 540nm) became more intense as the annealing temperature was raised. The 400nm band was asymmetric and consisted of two peaks, suggesting a trigonal distortion. The emission spectra consisted of a zero phonon line (ZPL), along with its associated multi-phonon side bands. The high Dq/B (3.21) suggested the presence of Cr3+ in a strong crystal field. With annealing, the emission lifetimes increased from similar to 7 to similar to 34ms. This work demonstrates rapid, low-temperature synthesis of a red-emitting phosphor, with potential applications in bio-imaging, sensors, and lighting
An Experimentally Validated Lumped Circuit Model for Piezoelectric and Electrodynamic Hybrid Harvesters
No full textEnergy harvesters transform the ambient energy into usable electrical form that can be potentially used by sensors and other low-power devices. In this paper, modeling of a hybrid energy harvester that is composed of piezoelectric and electrodynamic mechanisms of energy conversion is presented and the predictions from the model are corroborated by experimental results from two hybrid harvesters designed and fabricated for the purpose. A method of representing a hybrid energy harvester using lumped circuit elements is proposed. The optimal electrical loads are then determined with relative ease from the equivalent circuit of the harvester. A magnetic circuit that provides maximum electromechanical coupling in the electrodynamic domain is designed. Moreover, a curved piezoelectric beam is analyzed for a compact arrangement of both domains in a single harvester. Two hybrid energy harvesters having the same electrodynamic domain, one with curved piezoelectric beam and the other with a straight piezoelectric beam, are fabricated and evaluated for their performance in comparison with that estimated from the proposed model. Experimental models generating 1.7 mW from 0.5 g(n) input acceleration have been realized with at least 50% of conversion efficiency
Investigating the electrical conduction and relaxation phenomena in rare earth erbium doped lead free 0.94Na(0.5)Bi(0.5)TiO(3)-0.06BaTiO(3) by impedance spectroscopy
No full textRare earth erbium (Er3+) doped 0.94Na(0.5)Bi(0.5)TiO(3)-0.06BaTiO(3) (NBT-6BT) was prepared via a solid state synthesis route as per the nominal formula 0.94Na(0.5)Bi(0.5-x)Er(x)TiO(3)-0 .06BaTiO(3) (0 <= x <= 0.05). Detailed impedance spectroscopy studies, invoking complex impedance and modulus formalisms, were carried out in order to investigate the influence of erbium doping on the long range electrical conduction and localized relaxation in the system. Our results suggest that a low concentration (x = 0.005) of rare earth doping significantly reduces the long range ionic conductivity (with respect to the undoped NBT-6BT value) and decreases the local relaxation, making the system electrically homogeneous. At a higher doping concentration (x >= 0.01), enhancement in the electrical conductivity occurs and local relaxation increases in the system. Observed trends are rationalized on the basis of a model, which hypothesizes phase segregation at a higher concentration of Er-doping. Such segregation leads to the formation of pure NBT-6BT regions and Er-saturated phase with probable dissimilar polar symmetry compared to that of NBT-6BT. A possible correlation between grain size, electrical conductivity, activation energy of conductivity, and local relaxation is indicated. Published by AIP Publishing
Field Effect Transistor Based on Layered NiPS3
No full textLayered metal phosphochalcogenides of molecular formula, MPX3(M = Mn, Fe,Co, Ni,etc and X = S, Se) have been emerging as new class of semiconductors towards various catalytic and optoelectronic applications. The low cleavage energy associated with these layered chalcogenides may lead to devices with very thin semiconductor channels. Herein, we report the first successful fabrication of field effect transistor (FET) using layered NiPS3 that reveals n-type semiconducting behavior. Devices using bulk and few-layer NiPS3 with gold contacts show on/off ratios of -10(3)-10(5) at 25 degrees C. The device characteristics reveal an increase in on-state current with decrease in threshold voltage and the Schottky barrier height is extracted to be 112 meV. Density functional theory calculations reveal various parameters that affect electron/hole doping in the layered phosphochalcogenide material
Interfacial Microstructure and Mechanical Properties of Friction Stir Welded Joints of Commercially Pure Aluminum and 304 Stainless Steel
No full textIn the present investigation, friction stir welding of commercially pure aluminum and 304 stainless steel was carried out at varying tool rotational speeds from 200 to 1000 rpm in steps of 200 rpm using 60 mm/min traverse speed at 2 (degree) tool tilt angle. Microstructural characterization of the interfacial zone was carried out using optical microscope and scanning electron microscope. Energy-dispersive spectroscopy indicated the presence of FeAl3 intermetallic phase. Thickness of the intermetallic layer increased with the increase in tool rotational speed. X-ray diffraction studies indicated the formation of intermetallic phases like FeAl2, Fe4Al13, Fe2Al5, and FeAl3. A maximum tensile strength of similar to 90% that of aluminum along with similar to 4.5% elongation was achieved with the welded sample at tool rotational speed of 400 rpm. The stir zone showed higher hardness as compared to base metals, heat affected zone, and thermo-mechanically affected zone due to the presence of intermetallics. The maximum hardness value at the stir zone was achieved at 1000 rpm tool rotational speed
Bandgap Engineered HgCdTe Nano-Crystal Based Hetero-Junction Infrared Sensor
No full textAdvantage of remote-sensing in mid wave infrared (MWIR) spectral range (2 mu m-5 mu m) due to atmospheric transmission window. Dominant photon detectors in this range are single crystal InSb and HgCdTe, while cost of these detectors is very high and requires cooling around 80K to reduce dark current. Semiconductor Nano-Crystals or Quantum dots (QD) provide an alternative, combining the advantages of speed and Detectivity (D*) of quantum detectors with much reduced fabrication costs compared to single crystal epitaxial materials. This paper highlights synthesis of ternary alloy semiconductor Mercury Cadmium-Telluride (HgCdTe) colloidal quantum dots and realization of HgCdTe/Si hetero-junction infrared detector sensitive in MWIR range at room temperature. The photo-response of the nano-crystal HgCdTe/Si heterojunction devices is found to have significant response in MWIR region at room temperature
Composites of Sulfur-Titania Nanotubes Prepared by a Facile Solution Infiltration Route as Cathode Material in Lithium-Sulfur Battery
No full textAchieving high energy density has been the focus of research in rechargeable batteries. Lithium-sulfur system is attractive due to its high theoretical energy density (2500 Wh kg(-1)). The major problem in Li-S system is associated with the dissolution of lithium polysulfides formed at the cathode during discharge. Shuttling of polysulfides between the cathode and anode during cycling reduces the efficiency of cycling. In the present study, TiO2 nanotubes are prepared from nanoparticles by hydrothermal route. Titania-sulfur composite has been prepared by infiltrating sulfur solution into the TiO2 nanotubes and studied as a cathode material in a non-aqueous electrolyte. Cycling behavior of Li-S cells fabricated using pristine sulfur and TiO2 nanoparticle-sulfur composite is also studied for comparison. Cells with TiO2 nanotubes exhibit better discharge capacity and coulombic efficiency than the cells with TiO2 nanoparticles and pristine sulfur
Coordination-driven self-assembly of ruthenium(II) architectures: synthesis, characterization and cytotoxicity studies
No full textCoordination-driven self-assembly of organometallic eta(6)-arene ruthenium(ii) supramolecular architectures (MA(1)-MA(4)) was carried out by employing dinuclear ruthenium acceptors Ru-2(mu-eta(4)-C2O4)(CH3OH)(2)(eta(6)-p-cymene)(2)](CF3SO3)(2) (Ru-a), Ru-2(mu-eta(4)-C6H2O4)(CH3OH)(2)(eta(6)-p-cymene)(2)](CF3SO3)(2) (Ru-b), Ru-2(dhnq)(H2O)(2)(eta(6)-p-cymene)(2)](CF3SO3)(2) (Ru-c) and Ru-2(dhtq)(H2O)(2)((6)-p-cymene)(2)](CF3SO3)(2) (Ru-d) separately with a new tetratopic donor (TD) in methanol at room temperature TD = N,N,N,N-tetra(pyridin-4-yl)-1,1-biphenyl]-4,4-diamine]. All the coordination architectures were characterized by using spectroscopic techniques. The potency of these self-assembled architectures against human cervical cancer HeLa and human lung adenocarcinoma A549 cell lines is explored in vitro using MTT (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide), annexin V-FITC/PI and 2,7-dichlorofluorescein-diacetate assays
Confirmation of wormhole attack in MANETs using honeypot
No full textThe flexibility and ease of deployment provided by Mobile Ad hoc Networks (MANETs) come at the cost of lack of security and vulnerability. Many solutions are proposed to protect MANET from attacks, ranging from attack identification to prevention. Although these solutions reduce the attacks in a MANET, they are likely to identify many false attacks as real ones. Such false alarms occur more often when an attack is complex and have multiple features, for example in a wormhole attack. In this paper we propose a Wormhole Attack Confirmation (WAC) System using honeypot to mitigate false alarms in a MANET and protect its resources. The confirmation of attacks dictates the necessity of analyzing all the possible scenarios of the attack. In order to analyze the wormhole attack we have built a Wormhole Attack Tree based on its symptoms. The honeypot confirms the wormhole attack using the Wormhole Attack Tree (WAT) and history of attacks. We have simulated the proposed system in several MANET environments of varying sizes of nodes and applications. On several occasions the results have demonstrated that the proposed system is efficient in confirming the wormhole attack, thereby saving the resources and minimizing the path re-establishment. (C) 2018 Elsevier Ltd. All rights reserved
Note: Multi-sheet light enables optical interference lithography
No full textWe propose and demonstrate a modified spatial filter-based single-shot lithography technique for fabricating an array of microfluidic channels. This is achieved by illuminating the photopolymer specimen with a multiple light sheet (MLS) pattern. Modified spatial filtering is employed in a cylindrical lens system to generate the MLS pattern. The transmission window the difference (alpha - beta) angle] of the spatial filter determines the characteristics of the pattern and the fabricated microfluidic channel array. After exposing to a negative photoresist (DPHPA monomer with rose bengal as the photoinitiator), this gives rise to an array of micro-fluidic channels (post development process). We studied the effect of micro-channel geometry (channel width, inter-channel separation, and aspect ratio) for varying exposure times that show near-linear dependence. The results show that the fabricated array has 7 prominent channels with an individual channel width and inter-channel separation of approximately 5 mu m and 12 mu m, respectively. The proposed technique enables selective plane patterning and reduces the overall cost for large-scale production. Published by AIP Publishing