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Industrial heat island: a case study of Angul-Talcher region in India
Get PDFMost of the urban heat island (UHI) studies are carried out in densely populated cities but core industrial areas are also potential sites of heat island effect despite having a comparatively lower population. In the present study, heat island assessment has been carried out for Angul-Talcher industrial area (ATIA) which is one of the oldest industrial areas of India and is still undergoing a transformation to accommodate more industries and mining operations. As the major contributors towards influencing local meteorology were expected to be industrial (and mining) activities, the heat island was studied as "industrial heat island" (IHI) rather than urban heat island. Industrial and mining sites were the most frequent nighttime canopy-layer heat island intensity (HIN) hotspots due to anthropogenic heat of associated industrial processes as well as built structures. During the daytime, croplands experienced the most frequent canopy-layer HIN hotspots which could be attributed to low moisture of the soils during the non-farming period of the field campaign. Hourly maximum atmospheric heat island intensities were observed in the range of 7-9 degrees C. Monthly maximum HINs ranged from 2.97 to 4.04 degrees C while 3-month mean HINs varied from 1.45 to 2.74 degrees C. Amongst different land use/land cover classes, the highest mean canopy-layer heat island intensity for the entire 3-month-long duration of field campaign during nighttime was assessed at the mining sites (3-month mean 2.74 degrees C) followed in decreasing order by the industrial sites (2.52 degrees C), rural and urban settlements (2.13 degrees C), and croplands (2.06 degrees C). Corresponding daytime canopy-layer heat island intensity was highest for the croplands (2.07 degrees C) followed in decreasing order by the mining sites (1.70 degrees C), rural and urban settlements (1.68 degrees C), and industry (1.45 degrees C)
Insights into coarse particle optics based on field evidence of particle morphology, chemical composition and internal structure
No full textAerosol particles scatter and absorb solar radiation and affect the Earth's radiation budget. The aerosol particles are usually non-spherical in shape and inhomogeneous in chemical composition. For simplicity, these particles are approximated as homogeneous spheres/spheroids in radiative models and in retrieval algorithms of the ground and spaceborne observations. The lack of information on particle morphology (especially shape), chemical composition (that govern their spectral refractive indices) and most importantly internal structure (three dimensional spatial distribution of chemical species) lead to uncertainty in the numerical estimation of their optical and radiative properties. Here, we present a comprehensive assessment of the particles' volumetric composition. The particles were collected from Jaisalmer (arid environment) and Delhi (urban environment) of India and subjected to Focused Ion-Beam (FIB) coupled with Scanning Electron Microscopy (SEM) and Energy Dispersive X-ray Spectroscope (EDS). Based on analysis of #2 particles from Jaisalmer, particles were observed to be composed of Fe, Ca, C, Al, Cu and Mg rich shell with Si and O rich core as opposed to those of Delhi particles (no #3) which were observed to be with Cu and S rich core and Hg, Ag, C, S and N rich shell. Based on the homogeneous sphere/spheroid assumption, conventional SEM-EDS and FIB-SEM-EDS results, different particle model shapes [single species homogeneous sphere (SP1) and spheroid (SPH1); multiple species homogeneously mixed sphere (SP2) and spheroid (SPH2); and core-shell (CS)] were considered for simulating their respective optical properties; SSA (Single Scattering Albedo) and g (Asymmetry parameter). The effect of internal structure on SSA was found to be prominent in particles having low value of the imaginary part of refractive index (k). While the same was observed to be low (nearly negligible) for the particle with the high value of k. The particles rich in copper are found to have high light absorbing property which causes positive radiative forcing
Low-Pressure Mechanical Switching of Ferroelectric Domains in PbZr0.48Ti0.52O3
Get PDFLow-energy switching of ferroelectrics is currently being investigated for energy-efficient nanoelectronics. While conventional methods employ electrical fields to switch the polarization state, mechanical switching is investigated as an interesting alternative low-energy switching concept, if low enough pressures could be achieved. Here, the thickness-dependent mechanical and electrical switching behavior of ferroelectric PbZr0.48Ti0.52O3/YBa2Cu3O7-delta(PZT/YBCO) epitaxial heterostructures grown on single crystalline LaAlO3-(001)(pseudo-cubic)(LAO) substrate is reported. Mechanical switching is found under relatively low force (600 nN; estimated pressure approximate to 0.21 GPa) in atomic force microscopy-based measurements. Mechanically switched domains can be erased by small electric fields and, interestingly, exhibit a surface potential change similar to electrically poled areas. The feasibility of switching these heterostructures with very low pressure makes them promising candidates for nanoscale electromechanical devices
Mechanical, electrical and thermal properties of graphene oxide-carbon nanotube/ ABS hybrid polymer nanocomposites
Get PDFMultiwalled carbon nanotubes (MWCNTs), functionalized carbon nanotubes (FCNTs) and graphene oxide-carbon nanotube (GCNTs) hybrid Bucky paper (BP) reinforced acrylonitrile-butadiene-styrene (ABS) composites are prepared via vacuum filtration followed by hot compression molding. The nanomechanical, electrical and thermal properties of these BP reinforced ABS composites are studied. The nanoindentation hardness and elastic modulus of GCNTs-ABS hybrid composites reached to 389.98 +/- 91.79 MPa and 7669.6 +/- 1179.12 MPa respectively. Other nanomechanical parameters such as plastic index parameter, elastic recovery, the ratio of residual displacement after load removal and displacement at maximum load are also investigated. The improved nanomechanical properties are correlated with Raman spectroscopy and scanning electron microscopy (SEM). It is found that GCNTs and their composites showed the higher value of defect density. The maximum value of defect density range for GCNTs and GCNTs-ABS is (297.4 to 159.6) and (16.0 to11.6), respectively. The higher defect density of GCNTs indicates that the interfacial interaction between the ABS, which was further correlated with electrical and thermal properties. Additionally, the through-plane electrical conductivities of MWCNTs, FCNTs and GCNTs based ABS composites were 6.5 +/- 0.6, 4.5 +/- 0.7 and 6.97 +/- 1.2 S/cm respectively and thermal conductivities of MWCNTs, FCNTs and GCNTs reinforced ABS composites; 1.80, 1.70 and 1.98 W/mK respectively. These GCNTs-ABS composites with this value of thermal conductivity can be used in various applications of efficient heat dissipative materials for electronic devices
Metal nanoparticles enhanced thermophysical properties of phase change material for thermal energy storage
No full textPhase change materials (PCMs) are one of the promising materials in thermal energy storage systems. In this work PCM nanocomposites were prepared using melt-blending technique by dispersing metal nanoparticles (Fe, Cu) at mass fraction of 0.5 wt% in magnesium nitrate hexahydrate (MNH), an inorganic salt hydrate PCM. The as-prepared PCM nanocomposites were analyzed by scanning electron microscopy (SEM) and X-ray diffractometer (XRD). Fourier transform infrared spectroscopy (FTIR) analysis was carried out to monitor the changes in chemical nature of PCM nanocomposites. The heat transfer characteristics were investigated by conventional heating system, which were used to carry out melting (charging) and solidification (discharging) cycle of MNH-metal nanocomposites. The experiment results clearly indicates that the rate of melting and solidification of MNH-metal nanocomposites increased at 0.5 wt% mass fraction of metal nanoparticles as compared to MNH. The thermal conductivity of MNH-metal nanocomposites at 0.5 wt% mass fraction of metal nanoparticles (Fe, Cu) in solid phase was measured using the transient hot method, which clearly indicates that thermal conductivity improved to (0.61) W m(-1) K-1 for MNH-Fe nanocomposite & (0.63) W m(-1) K-1 for MNH-Cu nanocomposite than that of pure MNH (0.4) W m(-1) K-1. The prepared nanocomposites showed good heat transfer characteristics and better thermal conductivity. Therefore, this study demonstrates that metal nanoparticles, added to inorganic PCM (MNH) had a significant potential for enhancing the thermophysical properties and makes it promising candidate for thermal energy application
Partially unwound helical mode in surface stabilized ferroelectric liquid crystal geometry
No full textWe report the dielectric relaxation spectroscopy and textural observations in surface stabilized ferroelectric liquid crystal (FLC) (SSFLC), having thickness less than the pitch value of the FLC and non-SSFLC geometries, having thickness of sample cell more than the pitch value of same FLC material, namely SCE-13 to get a deeper understanding of the helicoidal structure at the surface of bounding substrate. In SSFLC sample cell, the surface boundaries of cell allow stronger surface forces to align molecules parallel to the substrate and resultant helix becomes unwound. In non-SSFLC cell, the boundary effect is slightly weaker than in SSFLC and hence the helical structure is slightly unwound at the interface of the substrate and FLC; whereas in bulk the helix is naturally wound. The suppression of helix in SSFLC state has resulted in distinct and sharp partial relaxation peaks of unwound helical mode (p-UHM) whereas in non-SSFLC cells no p-UHM relaxation peak is observed. The p-UHM process is highly dependent on the applied oscillating voltage above the threshold voltage of 300 mV, whereas the dependence of well-established Goldstone mode is negligible. Furthermore, textural observations in SSFLC state have shown three molecular orientations, whereas in non-SSFLC cells, optical textures are multi domain planar-aligned. The underlying studies will give fundamental insights into the SSFLC and non-SSFLC structures which in turn pave a way towards the fabrication of high-performance futuristic electro-optical devices
Forster resonance energy transfer in organic photovoltaics devices fabricated by electric field assisted spray technique
No full textThin films of the ternary polymer blend (donors PCE-10 and PCDTBT with the acceptor PC71BM in chlombenzene) were fabricated by using spray coating technique without and with applied voltage to the nozzle during deposition. The increased absorption range from 400 nm to 800 nm indicates that Forster resonance energy transfer (FRET) is occurring for the films deposited under the electric field. This is also supported by photo-luminescence measurements and suggesting that under the applied voltage the orientation of polymer chains are changing at desired distances to facilitate FRET phenomenon to occur due to repulsion between uniformly charged ultrafine droplets. The size of droplets further reduced at higher applied voltage. Absorption, photo-luminescence, femtosecond transient absorption spectra and Kinetics traces were recorded to elucidate the role of applied DC voltages during the deposition of these films on photovoltaic performance of bulk heterojunction organic solar cell. The effect of FRET in polymer-polymer thin film under applied voltage during the deposition is observed, which indicates enhancement in the power conversion efficiency with the maximum value of 6.86% (J(sc) of 15.81 mA/cm(2) and V-oc of 0.77 V) at an applied voltage of 750 V
High energy electron beam induced improved thermoelectric properties of PEDOT:PSS films
No full textThe tailoring of electrical conductivity and thermoelectric properties of conducting polymer through chemical dopants is an important area of research. However in the present work we demonstrate that the exposure of PEDOT:PSS films to high energy electron beam to improve its thermoelectric properties. The electron beam treatment of the films was carried out with 10 MeV RF accelerator by delivering dose up to 75 kGy in steps. The electrical conductivity was found to enhance linearly while the Seebeck coefficient systematically decreases with increasing dose up to 25 kGy and over all power factor improves till 10 kGy. In depth characterizations using PL, UV-Vis, FESEM, XPS, FTIR and Raman spectroscopy revealed that on irradiation the losses of PSS units and associated structural modifications along with increase in oxidation level of PEDOT component are responsible for improved conductivity and lowering of Seebeck coefficient. The study also highlights the utilization of flexible and simply prepared PEDOT:PSS thin films as potential radiation dosimeter based upon linear rise in electrical conductivity with increasing dose of electron beam
Impact of twisted alignment on the smectic layer structure of ferroelectric liquid crystal
No full textThe twisted aligned cell of ferroelectric liquid crystal is assessed through electro-optical and dielectric spectroscopy and a comparison is made with antiparallel planar aligned cells of the same thickness around 8 mu m. The study has been carried in two types of twisted aligned samples, one is natural cooled sample in the heating chamber and another is slow cooled at the rate of 0.05 degrees C/min. The influential distinct results have been observed in natural cooled twisted cells. In natural cooled cells, the helicoidal structure at the surface and in the bulk of the cell is distinct and contributes separately to the response of the cell. On the other hand, at the same cooling condition in twisted cell, the smectic layers are in a twisted state resulting into a non-uniform helical structure, therefore, the partial helicoidal unwound structure at the surface and in the bulk of the cell are not observed contributing to the dielectric permittivity separately unlike in planar aligned cell. The twisted cell is found to induce the restoring force within the sample. However, the slow cooling cydes on the twisted cell changes to the strain free equilibrium state, whereas the behavior of the planar sample cell remains unchanged. The studies are significant for the display devices based on twisted alignment of FLC cells
Improved optical properties of ion beam irradiated (K,Na)NbO3 thin films
No full textIn the present study, we have demonstrated the effect of swift heavy ion (SHI) irradiation on photoluminescence (PL) and time-resolved photoluminescence (TRPL) properties of potassium sodium niobate (KNN) thin films deposited on Si and quartz substrates using RF magnetron sputtering. Ion beam irradiation of crystalline KNN films was carried out at room temperature using 100 MeV Ni ions with different fluences such as 1 x 10(12), 5 x 10(12) and 1 x 10(13) ions/cm(2). Various modes obtained in Raman spectra of films are related to NbO6 octahedron which confirms the crystalline phase of KNN. Moreover, the decrease in peak intensities with ion fluence is attributed to defects produced after SHI irradiation. Xray photoelectron spectroscopy results show the increase in oxygen vacancies after irradiation. The optical properties of pristine and irradiated films were evaluated using UV-Vis-NIR spectroscopy and a significant improvement in optical transmittance upon irradiation was observed. The optical band gap of films is decreased to 3.14 eV upon irradiation at 1 x 10(12) ions/cm(2). PL spectra of films were obtained with excitation wavelength of 274 nm and, the results depict the emission wavelengths (band-to-band or near band edge) of KNN thin films in regime of 313-367 nm (3.96-3.38 eV). The origin of blue and green emission is due to defects created as a result of ion irradiation. The green luminescence evolved at higher fluence (i.e. 1 x 10(13) ions/cm(2)) may be attributed to intrinsic defects such as oxygen vacancies. The obtained Commission Internationale de I'Elcairage (CIE) color coordinates are shifted towards white point in chromaticity diagram as a function of ion fluence. TRPL result reveals the decay lifetime of KNN films in nanosecond regime and, is varied with ion fluence. At fluence of 1 x 10(13) ions/cm(2), film exhibited the minimum average decay lifetime (1.75 ns) which suggests that KNN can be a potential candidate for optical switching, optical display and sensors, and opto-electronic device applications