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Conducting polymer/bio-material composite coatings for corrosion protection
No full textPresent study demonstrates a facile in situ oxidative copolymerization method to synthesize conducting copolymer composites in aqueous chitosan medium. The development of poly(aniline-co-o-toluidine)-chitosan-SiO2/epoxy composite coatings were carried out by thermal curing of the spray-coated mild steel substrates. FT-IR analysis, XRD studies, SEM and HR-TEM evidenced that the composite has synergistically integrated properties of the copolymer and the SiO2 nanoparticles. The electrochemical analyses of the coatings in 3.5% NaCl solution manifest an efficient role of copolymer composite in the remarkable improvement of the corrosion resistance of the substrate. The analyses involve Tafel polarization and electrochemical impedance spectroscopy (EIS) studies. The corrosion inhibition property of conducting copolymers, the film forming ability of chitosan, and robustness of SiO2 nanoparticles kept the corrosion rate of the coatings significantly low, under highly corrosive conditions. Mild steel coated with 3.0% loading of copolymer composite coating demonstrated very low corrosion current density (i(corr)) and significantly high pore resistance (R-pore)
Conductive polymers for thermoelectric power generation
No full textIn spite of the fact that conducting polymers, during the past decade, have made inroads into various flexible devices including electronics, supercapacitors, sensors, transistors and memories etc. their exploration in the field of thermoelectric power-generation has not yet been significant. This review provides a comprehensive study regarding thermoelectric performance of various conducting polymers depending upon their specific structural and physico-chemical properties. Recent trends in organic thermoelectrics are discussed as: (i) factors affecting thermoelectric performance; (ii) strategies required for improvement of the power factor (due to inherent low thermal conductivity); and (iii) challenges that still lie ahead. A detailed analysis of electrical and thermal transport mechanisms suggests that various processes such as stretching, controlled doping and addition of inorganic materials/carbon nanostructures, may be applied for enhancement of the thermoelectric figure-of-merit. The attempts are made for highlighting as to how these conducting polymers can be realized into efficient thermoelectric generators by summarizing various reported architectural-designs. These devices have a tremendous potential for tapping low-temperature heat (e.g. body/appliances' heat, geo-thermal/oceanic heat etc.) to power wearable medical sensors and smart electronic devices. Finally, the efforts are put together to familiarize the reader with the big breakthrough that can be created by light-weight, flexible, non-toxic conducting polymers in thermoelectric domain
Exploration of Trap Levels in GaN and Al0.2Ga0.8N Layers by Temperature-Dependent Photoconductivity Measurement
No full textThe optoelectronics properties of Gallium Nitride and its alloys are attracting increasing interest due to the potential application of these materials for UV photodetectors and high electron mobility transistors. However, the persistent photoconductivity (PPC) in the GaN based photoconductive devices affects the light sensitive characteristics and with temperature these photoinduced effects are different in ternary alloys such as that of the AlxGa1-xN layers. In order to study the temperature dependent PPC effect, we have performed photoconductivity measurements on two heterostructures constituting unintentional n-type GaN and n-type Al0.2Ga0.8N layers on GaN buffer on Mo back-coated c-plane sapphire substrate using UV monochromatic light. Low temperature PPC measurements have shown that trap levels exist in both AlGaN and GaN layers. In our samples PPC decay behavior in n-Al0.2Ga0.8N layer was found to better than the n-GaN layer at low temperatures. Broad distribution of trap (defect) levels with energies lower than the bandgap energies were observed in both n-Al0.2Ga N-0.8 layer and GaN layer as evident from room temperature photoluminescence spectra. In ternary nitrides, the presence of 2DEG channel dominates the photoresponse at low temperature whereas in binary nitrides, the photoresponse is majorly affected by the trap levels. This study enabled us to propose AlxGa1-xN based UV photodetector for low-temperature applications
Source apportionment of PM10 in Delhi, India using PCA/APCS, UNMIX and PMF
No full textSource apportionment of particulate matter (PM10) measurements taken in Delhi, India between January 2013 and June 2014 was carried out using two receptor models, principal component analysis with absolute principal component scores (PCA/APCS) and UNMIX. The results were compared with previous estimates generated using the positive matrix factorization (PMF) receptor model to investigate each model's source-apportioning capability. All models used the P-10 chemical composition (organic carbon (OC), elemental carbon (EC), water soluble inorganic ions (WSIC), and trace elements) for source apportionment. The average PM10 concentration during the study period was 249.7 +/- 103.9 mu g/m(3) (range: 61.4-584.8 mu g/m(3)). The UNMIX model resolved five sources (soil dust (SD), vehicular emissions (VE), secondary aerosols (SA), a mixed source of biomass burning (BB) and sea salt (SS), and industrial emissions (IE)). The PCA/APCS model also resolved five sources, two of which also included mixed sources (SD, VE, SD+SS, (SA+BB+SS) and 1E). The PMF analysis differentiated seven individual sources (SD, VE, SA, BB, SS, IE, and fossil fuel combustion (FFC)). All models identified the main sources contributing to PM10 emissions and reconfirmed that VE, SA, BB, and SD were the dominant contributors in Delhi
Thickness-dependent magnetic and transport properties of La0.5Sr0.5MnO3 thin films deposited by DC magnetron sputtering on the LaAlO3 substrate
No full textThickness-dependent structural, magnetic and transport properties of La0.5Sr0.5MnO3(LSMO) thin films have been studied. A series of the LSMO films with thickness 30, 60, 125 and 300 nm have been deposited on the LaAlO3 substrate using DC magnetron sputtering. The paramagnetic to ferromagnetic transition at T-c is followed by antiferromagnetic ordering at T-N in all films. It is also found that all LSMO films have T-c lower than that of bulk LSMO. A small variation of T-c is observed on increasing the film thickness. However, T-N is found to rise with increase in the film thickness. The 60 nm-thick film shows a wide insulator to metal transition. The resistivity above 240 K of the films with various thicknesses is consistent with a small polaronic hopping conductivity. The polaronic formation energy E-A rises with the increase of the film thickness except for 60 nm thin film, where a small decline in E-A is observed. The correlation between observed structural, magnetic and electrical properties with the thickness of the films has been discussed in this paper
Thermoelectric properties of BiCuSeO with bismuth and oxygen vacancies
No full textIntroducing vacancies in oxychalcogenides is an effective paradigm for the improvement of thermoelectric properties by reducing thermal conductivity through phonon scattering as well as by decreasing electrical resistivity via incorporation of holes through vacancies. In this paper, we present thermoelectric properties of Bi1-xCuSeO1-y with y = 0 for x = 0, 0.04, and y = 0.02 for x = 0.04, 0.08, 0.12. X-ray diffraction studies reveal BiCuSeO as the main phase with trace amounts of Cu1.8Se in Bi0.92CuSeO0.98 and Bi0.88CuSeO0.98. The impurity phases of Cu1.8Se in Bi0.92CuSeO0.98 and Bi0.88CuSeO0.98 could be due to the presence of vacancies. The electrical resistivity of Bi0.96CuSeO0.98 is lower than BiCuSeO, but higher than Bi0.96CuSeO, since Bi vacancies produce holes that are partially compensated by O vacancies. Electrical resistivity decreases with an increase in Bi vacancy content for y = 0.02. The Seebeck coefficient of samples shows that the similar trend as in electrical resistivity, following Mott's formula. Total and lattice thermal conductivity of Bi0.96CuSeO is higher than BiCuSeO as well as Bi0.96CuSeO0.98. This increases with further increase in bismuth vacancy. Introduction of vacancies (Bi and O) in BiCuOSe lead to higher thermal conductivities and lower Seebeck coefficients, and result in adverse effect on zT
Single-frequency impedance analysis of biofunctionalized dendrimer-encapsulated Pt nanoparticles-modified screen-printed electrode for biomolecular detection
No full textWe report the fabrication of polyamidoamine (PAMAM) dendrimer with 128 carboxyl group-encapsulated Pt nanoparticle-modified screen-printed carbon electrode, as an impedimetric biosensor, for the quantitative detection of human cardiac biomarker troponin-I (cTnI). PAMAM-Pt was electrochemically deposited over SPCE and its 128 terminal carboxyl groups were used as anchors for the site-specific biomolecular immobilization of protein antibody, anti-cTnI. The biosensor was characterized by contact angle measurements, transmission electron microscopy, UV-visible spectroscopy, and electrochemical techniques. A single-frequency impedance analysis study was utilized for the biomolecular sensing by monitoring the changes in the phase angle obtained at an optimized frequency resulting from antigen-antibody interactions. An optimized frequency of 100 Hz was obtained at which maximum changes in the phase angle were observed after immunoreactions for a given concentration of analyte. A concentration-dependent increase in the phase angle of the biosensor was observed with increasing cTnI concentration in the range of 1 pg mL(-1) to 100 ng mL(-1). Based on the concentration response data, the dissociation constant was found to be 0.51 pM reflecting high affinity of biosensor towards cTnI analyte arising due to high anti-cTnI loading with a better probe orientation on the 3-dimensional PAMAM-Pt structure
High-performance field emission device utilizing vertically aligned carbon nanotubes-based pillar architectures
Get PDFThe vertical aligned carbon nanotubes (CNTs)-based pillar architectures were created on laminated silicon oxide/silicon (SiO2/Si) wafer substrate at 775 degrees C by using water-assisted chemical vapor deposition under low pressure process condition. The lamination was carried out by aluminum (Al, 10.0 nm thickness) as a barrier layer and iron (Fe, 1.5 nm thickness) as a catalyst precursor layer sequentially on a silicon wafer substrate. Scanning electron microscope (SEM) images show that synthesized CNTs are vertically aligned and uniformly distributed with a high density. The CNTs have approximately 2-30 walls with an inner diameter of 3-8 nm. Raman spectrum analysis shows G-band at 1580 cm(-1) and D-band at 1340 cm(-1). The G-band is higher than D-band, which indicates that CNTs are highly graphitized. The field emission analysis of the CNTs revealed high field emission current density (4mA/cm(2) at 1.2V/mu m), low turn-on field (0.6 V/mu m) and field enhancement factor (6917) with better stability and longer lifetime. Emitter morphology resulting in improved promising field emission performances, which is a crucial factor for the fabrication of pillared shaped vertical aligned CNTs bundles as practical electron source
Heat Capacity and Mossbauer Study of Self-Flux Grown FeTe Single Crystal
No full textWe report mainly the heat capacity and Mossbauer study of self-flux grown FeTe single crystal, which is a ground state compound of the Fe chalcogenides superconducting series i.e. FeTe1-x (Se/S) (x) The as grown FeTe single crystal is large enough to the tune of a few centimetres and the same crystallizes in tetragonal structure having space group of P4/nmm. FeTe shows the structural/magnetic phase transition at 70 K in both magnetic and resistivity measurements. Heat capacity measurement also confirms the coupled structural/magnetic transition at the same temperature. The Debye model fitting of low temperature (below 70 K) heat capacity exhibited Debye temperature (oee integral (D) ) to be 324 K. Mossbauer spectra are performed at 300 and 5 K. The 300-K spectra showed two paramagnetic doublets and the 5-K spectra exhibited hyperfine magnetic sextet with an average hyperfine field of 10.6 Tesla matching with the results of Yoshikazu Mizuguchi et al
Experimental investigation of variations in morphology, composition and mixing-state of boundary layer aerosol: A balloon based study over urban environment
No full textThe morphology, composition, and complex mixing states of aerosol are extremely important physicochemical properties which are the major inputs to the optical/radiative models. Though, ground based observations of the said properties are abundant but the vertical profiles of the same are very much limited throughout the globe. The information on the vertical heterogeneity of the aforementioned properties over a polluted environment like Delhi will be very helpful to develop a better understanding of the thermodynamics of the lower atmosphere.
In present study, we carried out a tethered balloon based field campaign in National Physical Laboratory (28 degrees 38' 10 '' N, 77 degrees 10' 17 '' E) from 21 to 27 February 2014 to explore the vertical distribution of the said properties. Based on the microscopic observations, the bubbly shaped sulfate particles number percentage is less (5%) on the ground, abundant (49%) on altitude 350 m. At 500 m altitude, particles were majorly of spiked shape with elongated dimension similar to 3-4 mu m. The number percentage of the aged fractals has been found to increase by 4% in the 100-350 m range against the ground observations. Based on the bulk composition of non-carbonaceous species, at 200 m altitude, we observed significant amount (74%) of the oxides of sulfur compared to that of ground observations (30%) that could be due to temperature inversion and air parcel movement from IGP (Indo Gangetic Plain). Various core-shell type particle configurations have been observed at different altitudes. At 200 m altitude, particles were majorly aged with anionic species (like S, Cl and HSO4) and cationic species (like C2H5). The bulk and individual particle level data generated over Delhi environment in this experiment may improve our understanding of boundary layer aerosol and could provide the scientific insights of their probable effects on low level cloud formation