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Conduction pathways in CNF/PTFE composite: Air oxidized CNFs coated with the incomplete layer of PTFE
No full textIn the present work, the conduction pathways by air oxidized carbon nanofibers (CNFs) (coated with Polytetrafluoroethylene (PTFE)) dispersed in PTFE polymer have been studied and explored with backbone and dangling ends model. The utility of critical exponents (t) explains the distribution status of CNFs and indicates the possibility of charge transport by ohmic conduction due to connected conducting channels of CNF and tunneling transmission between close CNFs. A 5 wt% sample exhibits a conductivity of 1.91 S/m. Moreover, a cost and material saving method of coating of decomposed PTFE on CNF; regardless of the coating thickness is discussed and studied in order to improve interfacial interaction and dispersion within the polymer without using sonication. Some interesting and informative evidence have also been revealed such as a decrease in d spacing of layer of CNF after heat treatment at similar to 800 degrees C in air and confirmation of Hexafluoropropylene (HFP) and Octafluoro-1-butene (OF1B) thermal products of PTFE on CNFs. The presence and coating of HFP and OF1B were confirmed by FTIR and TEM respectively
Electronic structure, defect properties, and hydrogen storage capacity of 2H-WS2: A first-principles study
No full textFirst-principles calculations based on density functional theory (DFT) have been performed for layered 2H tungsten disulphide (WS2) with the aim to find its possible applications in opto-electronic and hydrogen storage devices. To study opto-electronic features of WS2, we solve the Bethe-Salpeter-Equation (BSE) on top of the standard self consistent GW quasi particle (QP) calculations. These calculations capture the excitonic effects which originate near the edge of conduction band, shows good agreement with the available measured data. The suitability of WS2 as a prospective material for hydrogen storage were predicted by using the Heyd-Scuseria-Ernzerhof (HSE06) hybrid functional. We have explored the effect of interstitial hydrogen and H-2 molecules insertion on the structural stability of WS2 in detail. The hydrogen atom charge states dependent stability was studied in the context of formation energy. Our calculations suggest that interstitial hydrogen can act as a deep donor whereas H-2 molecule exhibits more stability. The diffusion energy of H-2 molecule from one hollow site to the nearest in-plane hollow site has been calculated using transition state theory. Finally, ab initio molecular-dynamics (AIMD) calculations are carried out for WS2 consisting of 16H(2) molecules that ensures its structural stability at temperatures 300, 500, and 1000 K. Present predictions show that this material may be utilize for hydrogen storage due to expected high hydrogen densit
Enhanced field effect passivation of c-Si surface via introduction of trap centers: Case of hafnium and aluminium oxide bilayer films deposited by thermal ALD
No full textField effect passivation of crystalline silicon surface is controlled by tailoring the built-in charge in a bilayer dielectric system consisting of hafnium oxide (HfO2) and aluminium oxide (Al2O3). The effective surface recombination velocity (S-eff, (max)) similar to 10 cm/s is achieved at intermediate bulk injection levels with thermal ALD deposited HfO2 (top)/Al2O3 (bottom) bilayer system on n-type silicon with individual layer thickness between 3 and 7 nm. The best realized Seffme, value is lower by a factor of similar to 2.5 with respect to the single Al2O3 layer of similar thickness deposited under the same experimental conditions. The improved field effect passivation is quantified by enhanced effective charge density for the bilayer system in comparison with the corresponding value for single Al2O3 layer. The introduction of extra trap centers at the interface of the bilayer system is primarily responsible for the enriched field effect passivation, however, the sequence of the dielectric layers is important
Short Note on Superconductivity at Ambient Temperature and Pressure in Silver-Embedded Gold Nano-particles: a Goldsmith Job Ahead
No full textVery recent observation of superconductivity (arXiv:1807.08572) in both transport (resistance versus temperature) and magnetization (zero field cooled) at around 235 K and above has obviously raised many eyebrows. The experimentalists in particular are more thrilled than the theoreticians. Although the results presented in the paper are clean and both transport and magnetization measurements do approve the observation of superconductivity to some extent (the diamagnetic shielding fraction is low), the problem is to synthesize/fabricate the material. This I called the goldsmith job, primarily because one has to deal with gold and silver nano-particle combination/amalgamation/alloying or even who knows the interfacial new phase, which could be superconducting. This short note is written to let the spark continues, and the interesting work of Thapa and Pandey (arXiv:1807.08572) is reproduced independentl
Five-year measurements of ambient ammonia and its relationships with other trace gases at an urban site of Delhi, India
No full textIn this study, we present the 5-year measurements of ambient ammonia (NH3), oxides of nitrogen (NO and NO2) and carbon monoxide (CO) along with the meteorological parameters at an urban site of Delhi, India from January 2011 to December 2015. The average mixing ratios of ambient NH3, NO, NO2 and CO over the entire period of observations were recorded as 19.3 +/- 4.4 (ppb), 20.1 +/- 5.9 (ppb), 18.6 +/- 4.6 (ppb) and 1.8 +/- 0.5 (ppm), respectively. The mixing ratios of NH3, NO, NO2 and CO were recorded highest during winter season, followed by summer and monsoon season. In the present case, a substantial seasonal variation of NH3 was observed during all the seasons except NO, NO2 and CO. The results emphasized that the traffic could be one of the significant sources of ambient NH3 at the urban site of Delhi as illustrated by positive correlations of NH3 with traffic related pollutants (NO (x) and CO). Surface wind as well as back trajectory analysis also supports the road side traffic and agricultural activities at the nearby area indicating possible major sources of ambient NH3 at observational site. Trajectory analysis, potential source contribution function and concentration weighted trajectory analysis indicated the surrounding nearby areas (NCR, Haryana, Punjab, Rajasthan and Uttar Pradesh) as a significant source region of ambient NH3 at the observational site of Delhi
High Temperature Dielectric And Impedance Spectroscopic Studies Of Multiferroic Yb(1-x)Ho(x)Mno(3) (x=0.1) Ceramics
No full textWe have studied the effect of Ho doping on the dielectric and impedance spectroscopic properties of multiferroic Yb1-xHoxMnO3 (x = 0.1). The X-ray diffraction (XRD) studies confirmed the formation of single phase and hexagonal crystal structure with space group P6(3)cm. Impedance spectroscopy has been carried out as a function of temperature and frequency from RT to high temperatures to study its dielectric properties
Metal Oxide Based Hydroelectric Cell for Electricity Generation by Water Molecule Dissociation without Electrolyte/Acid
No full textNever before has electricity been generated out of metal oxides without using any light (UV/IR), acid, or alkali, but it has been achieved by adding a few drops of water on nanoporous metal oxide based Hydroelectric cell (HEC) at room temperature. Electricity generation has been validated and unified for six different metal oxides based on the principle of water dissociation at oxygen deficient nonporous pellet. The presence of oxygen vacancies on the surface of all metal oxide samples has been confirmed by Raman and Photoluminescence spectroscopy techniques. Tin oxide (SnO2) based HEC has delivered maximum power similar to 16.6 mW in a 4.48 cm(2) cell area with highest current 22.2 mA, approximately 2.075 times higher than reported 8 mA current in ferrite based HEC. Water chemidissociation at metal oxide surface was found to be reinforced predominantly by electronegativity of metal cations and oxygen vacancies on nanoporous surface. Divergent peak current values ranging from 22.2 to 1.1 mA were obtained depending on internal resistance, grain boundary nature, water molecule dissociation capability, and nanopores connectivity in different oxides. Slow diffusion of ions in certain metal oxides due to high impedance of grain boundaries has reduced current as confirmed by dielectric and impedance spectroscopy. Metal oxide HEC provides an ecofriendly, cost-effective, and portable green energy source with almost no running cost
Microstructural evolution and photoluminescence performanance of nickel and chromium doped ZnO nanostructures
No full textColumnar growth morphology of ZnO nanostructures were synthesized by employing simple thermal evaporation of zinc precursor electroplated with nickel and chromium. The X-ray powder diffraction studies carried out for determining crystallographic phases of varied ZnO morphologies. The elemental analysis has been carried out to confirm the presence of Ni and Cr doping. The electron microscopy techniques, SEM and HRTEM, were used to investigate the influence of doping on microstructural properties. The columnar growth of ZnO structures observed in undoped ZnO, whereas, Ni doped ZnO reveals the spherical nanoparticles decorated on columnar growth of ZnO nanostructures and Cr doping leads to rod like structures with spherical and cubical nanoscale objects. HRTEM micrograph reveals the growth along different planes of ZnO crystal structure. Photoluminescence (PL) measurements reveal the alteration in defect related emission with doping. Time resolved PL elucidates the decay time parameters and its dependence on microstructural modification in ZnO
Exceeding milli-watt powering magneto-mechano-electric generator for standalone-powered electronics
No full textIn contrast to typical magnetic energy generators that use electromagnetic induction, which are bulky and have low generation efficiency under small magnetic fields at low frequency, magneto-mechano-electric (MME) generators utilizing the magnetoelectric (ME) coupling effect and magnetic interactions are considered promising candidates. MME generators will serve as a ubiquitous autonomous energy source converting stray magnetic noise to useful electric energy for applications in wireless sensor networks (WSN) for the Internet of Things (IoT) and low-power-consuming electronics. The key component in a MME generator is the ME composite consisting of piezoelectric and magnetostrictive materials, which elastically couples the electric and magnetic behaviour of the respective constituent. Here, we report a MME generator consisting of a crystallographically oriented Pb(Mg1/3Nb2/3)O-3-Pb(Zr,Ti)O-3 piezoelectric single crystal macro-fibre composite and a highly textured magnetostrictive Fe-Ga alloy, which exhibits an exceptionally high rectified DC output power density of 3.22 mW cm(-3). The large energy generation in this structure is ascribed to the coupling between the strong anisotropic properties of the piezoelectric single crystal fibres and textured Fe-Ga magnetostrictive alloy. A smart watch with IoT sensors was driven by the MME generator under a 700 mu T magnetic field
Langmuir-Blodgett Nanoassemblies of the MoS2-Au Composite at the Air-Water Interface for Dengue Detection
No full textWe report Langmuir-Blodgett (LB) films of molybdenum disulphide (MoS2) and gold nanoparticles (AuNP) composite being utilized as a biosensing platform for dengue detection. The LB films of the MoS2-AuNP composite have been transferred from the air-water interface to the indium tin oxide-coated glass substrate under optimized conditions. Further, antibodies specific to dengue NS1 antigen were immobilized onto these LB films. The fabricated immunosensor has been explored for NS1 antigen detection in standard samples as well as in spiked sera samples using electrochemical impedance spectroscopy. The NS1 antigen is present in the blood of infected persons from day one of the onset of clinical symptoms in primary dengue infection. The limit of detection for the standard and the spiked samples is found to be 1.67 and 1.19 ng mL(-1), respectively, which is suitable for clinical applications, as NS1 antigen levels in patient's sera range from 0.04 to 2 mu g mL(-1) in primary infection and from 0.01 to 2 mu g mL(-1) in secondary infection