IR@NPL
Not a member yet
3815 research outputs found
Sort by
Tb3+ and Eu3+ Doped Zinc Phosphate Glasses for Solid State Lighting Applications
No full textTo investigate how central metal tunes the synergetic interactions between substituted metallo-phthalocyanine and single-walled carbon nanotubes in enhancing the gas sensing properties, a comparative study has been performed by varying the central metal ion in fluorinated metal phthalocyanines and single-walled carbon nanotube hybrid. Hybrids of metal(ii)-1,2,3,4,8,9,10,11,15,16,17,18-24,25-hexa-decafluoro-29H,31H-phthalocyanine/single-walled carbon nanotube (F16MPc/SWCNTs-COOH, where M = Co, Zn) have been synthesized through - stacking interactions using the solution route. Spectroscopic (FT-IR, UV-vis, XPS and Raman), electron microscopic (TEM and FE-SEM) and TGA investigations have confirmed the successful functionalization and interaction of SWCNTs-COOH with F16MPc. Parts per billion (ppb) level Cl-2-selective chemiresistive gas sensors have been fabricated on glass substrates with precoated gold electrodes by using these hybrids. The responses of various F16MPc/SWCNTs-COOH sensors have demonstrated the central metal ion-dependence in the sensitivity of Cl-2
Al2O3-TiC Composite Prepared by Spark Plasma Sintering Process: Evaluation of Mechanical and Tribological Properties
No full textAl2O3-10TiC composites were synthesized by spark plasma sintering (SPS) process. Microstructural and mechanical properties of the composite reveal homogeneous distribution of the fine TiC particles in the matrix. The samples were produced with different sintering temperature, and it shows that the hardness and density gradually increases with increasing sintering temperature. Abrasion wear test result reveals that the composite sintered at 1500 A degrees C shows high abrasion resistance (wt. loss similar to 0.016 g) and the lowest abrasion resistance was observed for the composite sample sintered at 1100 A degrees C (wt. loss similar to 1.459 g). The profilometry surface roughness study shows that sample sintered at 1100 A degrees C shows maximum roughness (R (a) = 6.53 A mu m) compared to the sample sintered at 1500 A degrees C (R (a) = 0.66 A mu m) corroborating the abrasion wear test results
Distribution of VOCs in urban and rural atmospheres of subtropical India: Temporal variation, source attribution, ratios, OFP and risk assessment
No full textThis paper reports the first study which comprises the seasonal, diurnal variability, source characterization, ozone forming potential and risk assessment of volatile organic compounds (VOCs) at three sites (two urban and one rural) in the National Capital Territory of Delhi, India. The study was performed during three seasons of the year 2013-14 and two different categories of VOCs (aromatics and halogenated) have been selected. The study used the sampling and analytical procedures of NIOSH methods. Results showed that the mean concentration of sum of VOCs (Sigma VOC) is significantly higher at urban sites (110.0 and 137.4 mu g/m(3) for JN and CP, respectively) as compared to the rural site, DP (56.5 mu g/m(3)). The contribution of individual to total VOC concentrations is noticed to be very similar at all the three sites. Most of the VOCs are observed to be significantly higher in winter followed by summer and autumn. Diurnal cycles of aromatic VOCs are highly influenced by the vehicular traffic and photochemical oxidations which showed higher and lower levels during morning/evening and daytime, respectively. Diagnostic ratios of the toluene/benzene (ranged from 0.65 to 13.9) infers the vehicular traffic might be the main contributing source in the urban sites while xylene/benzene ratio (ranged from 0.7 to 2.8) confirms the VOCs are transported to rural site from the nearby urban areas. Correlation and factor analysis suggested the sources are group of different species (traffic emissions, solvent usage and industrial) rather than single gas. The analysis of reactivity in terms of Prop-Equiv concentrations and ozone forming potential indicated that m/p-xylene and toluene are the main VOC contributing to the total ozone formation in urban and rural sites, respectively. Hazard ratios and lifetime cancer risk values exceeded the permissible standards established by USEPA and WHO suggests that the people are at significant risk
Facile synthesis of earth-abundant and non-toxic p-type Si96B4/SiCp nanocomposites with enhanced thermoelectric performance
No full textOne of the impediments in the development of thermoelectric devices for power generation is that they mostly contain toxic and expensive elements and/or are synthesized using expensive or time-consuming material processing methodology. We report the synthesis of Silicon-Boron (Si96B4) alloy employing earth abundant constituent element using a facile single-step reactive sintering using spark plasma sintering technique. In order to enhance its mechanical properties, the synthesized Si96B4 alloy was dispersed with SiC nanoparticles and the effect of its addition on the thermoelectric and mechanical properties in the resulting Si96B4/SiC nanocomposite has been investigated. A thermoelectric figure-of-merit ZT similar to 0.27 at 1123 K was realized at an optimized composition of Si96B4/1 wt% SiC nanocomposite. This enhancement in ZT primarily originates from a noticeable reduction in the thermal conductivity on SiC dispersion in Si96B4 alloy, owing to the scattering of heat-carrying phonons by nanoscale SiC particles and mesoscale SiB3 precipitates, formed in-situ. The synthesized samples were characterized using X-ray diffraction and field emission scanning electron microscopy, based on which the enhancement in their thermoelectric and mechanical properties are discussed. Considering the low-cost and nontoxicity of the constituent elements coupled with facile and up-scalable one-step processing employed in its synthesis, Si96B4/SiC nanocomposites could be a potential p-type thermoelectric material for high-temperature power generation applications
Synthesis and electromagnetic shielding behaviour of poly(o-toluidine)/red mud composite
No full textThis paper is an attempt to find out application of red mud in controlling electromagnetic pollution. Composite of PoT/RM has been prepared by in-situ chemical oxidative polymerization and has been tested for electromagnetic shielding effectiveness. Red mud here acted as a filler material. The incorporation of 50wt% red mud in the polymer matrix results in a shielding effectiveness of 8.9dB in 8.2 to 12.4GHz frequency range (X-band). Furthermore, the structural analysis, morphology, and magnetization have been studied using XRD, TEM, and VSM techniques, respectively. TEM image of the composite shows the distribution of red mud particles in the polymer matrix. The magnetization decreases on incorporation of red mud in the polymer matrix
Structural, multiferroic, dielectric and magnetoelectric properties of (1-x) Ba0.85Ca0.15Ti0.90Zr0.10O3-(x)CoFe2O4 lead-free composites
No full textHigh performance lead-free multiferroic composites with strong magnetoelectric coupling effect are desired to replace lead-based ceramics in multifunctional device applications due to increasing environmental issues. We report crystal structure, ferroelectric, magnetic, dielectric and magnetoelectric properties of (1-x)Ba0.85Ca0.15Ti0.90Zr0.10O3-(x)CoFe2O4 (BCTZ-CFO) lead-free composites with x = 0.1, 0.3, 0.5, 0.7 and 0.9 synthesized by chemical solution method. BCTZ power was synthesized by sol-gel method while CFO was prepared by metallo-organic decomposition (MOD) method. The XRD results confirm successful formation of the BCTZ-CFO composites without presence of any impurity phase. At room temperature, the BCTZ-CFO composites show multiferroic behavior characterized by ferroelectric and ferromagnetic hysteresis curves. The composite having 10 wt% of CFO exhibited maximum polarization, remnant polarization and coercive field of P-s similar to 5.1 mu C/cm(2), P-r similar to 1.4 mu C/cm(2) and E-c similar to 11.6 kV/cm respectively. The BCTZ-CFO composite with 90 wt% of CFO incorporation exhibits improved ferromagnetic properties with M-s similar to 32 emu/g, M-r similar to 11.7 emu/g and H-c similar to 504 Oe. Mossbauer spectra analysis show two sets of six-line hyperfine patterns for BCTZ-CFO composites, indicating the presence of Fe3+ ions in both A and B sites. Increasing BCTZ content was found to decrease the hyperfine field strength at both sites and is consistent with the decreasing magnetic moment observed for the samples. The maximum dielectric constant value epsilon' similar to 678 is obtained at 1 MHz for composite with 10 wt% of CFO phase. The results indicate that the BCTZ-CFO composites are potential lead-free room temperature multiferroic systems
Scattering and absorption characteristics of aerosols at an urban megacity over IGB: Implications to radiative forcing
No full textAerosol scattering and absorption characteristics were investigated at an urban megacity Delhi in the western Indo-Gangetic Basin (IGB) during the period from October 2011 to September 2012 using different in-situ measurements. The scattering coefficient (sigma(sp) at 550 nm) varied between 71 and 3014 Mm(-1) (mean similar to 710 +/- 615 Mm(-1)) during the entire study period, which was about ten times higher than the absorption coefficient (sigma(abs) at 550 nm similar to 67 +/- 40 Mm(-1)). Seasonally, sigma(sp) and sigma(abs) were substantially higher during the winter/post-monsoon periods, which also gave rise to single scattering albedo (SSA) by similar to 5%. The magnitude of SSA (at 550 nm) varied between 0.81 and 0.94 (mean: 0.89 +/- 0.05). Further, the magnitude of scattering Angstrom exponent (SAE) and back-scattering Angstrom exponent (BAE) showed a wide range from -1.20 to 1.57 and -1.13 to 0.87, respectively which suggests large variability in aerosol sizes and emission sources. Relatively higher aerosol backscatter fraction (b at 550 nm) during the monsoon (0.25 +/- 0.10) suggests more inhomogeneous scattering, associated with the coarser dust particles. However, lower value of b during winter (0.13 +/- 0.02) is associated with more isotropic scattering due to dominance of smaller size particles. This is further confirmed with the estimated asymmetry parameter (AP at 550 nm), which exhibits opposite trend with b. The aerosol optical parameters were used in a radiative transfer model to estimate aerosol radiative forcing. A mean radiative forcing of -61 +/- 22 Wm(-2) (ranging from -111 to -40 Wm(-2)) was observed at the surface and 42 24 Wm(-2) (ranging from 18 to 87 Wm(-2)) into the atmosphere, which can give rise to the mean atmospheric heating rate of 1.18 K day(-1)
Influence of growth temperature on structural and optical properties of laser MBE grown epitaxial thin GaN films on a-plane sapphire
Get PDFEpitaxial thin GaN films (similar to 60 nm) have been grown on a-plane sapphire substrates at different growth temperatures (500-700 degrees C) using laser molecular beam epitaxy (LMBE). The effect of growth temperatures on the structural and optical properties of GaN layers grown on low temperature (LT) GaN buffer on prenitridated a-sapphire have been studied systematically. The in situ reflection high energy electron diffraction pattern revealed the three-dimensional epitaxial growth of GaN films on a-sapphire under the adopted growth conditions. The full width at half maximum (FWHM) value of x-ray rocking curves (XRCs) along GaN (0002) and (10-12) planes decreases with increasing growth temperature. The FWHM values of (0002) and (10-12) XRC for the 700 degrees C grown GaN film are 1.09 degrees and 1.08 degrees, respectively. Atomic force microscopy characterization showed that the grain size of GaN increases from 30-60 to 70-125 nm with the increase in growth temperature as GaN coalescence time is shorter at high temperature. The refractive index value for the dense GaN film grown at 600 degrees C is obtained to be similar to 2.19 at the wavelength of 632 nm as deduced by spectroscopic ellipsometry. Photoluminescence spectroscopy confirmed that the epitaxial GaN layers grown on a-sapphire at 600-700 degrees C possess near band edge emission at similar to 3.39 eV, close to bulk GaN. The GaN growth at 700 degrees C without a buffer still produced films with better crystalline and optical properties, but their surface morphology and coverage were inferior to those of the films grown with LT buffer. The results show that the growth temperature strongly influences the structural and optical quality of LMBE grown epitaxial GaN thin films on a-plane sapphire, and a growth temperature of >600 degrees C is necessary to achieve good quality GaN films. Published by the AVS
Influence of Li co-doping on structural property of sol-gel derived terbium doped zinc oxide nanoparticles
No full textThe presence of lattice distortion and defects in a composition leads towards a significant change in the optical, magnetic and electrical properties of the host material. In the present work, we have investigated the role of Li concentrations (0.25-1.0%) on structural property of Tb (1%) doped zinc oxide nanoparticles. A small concentration of terbium (1%) has been used to get minimum lattice distortion in the original structure of ZnO. To reduce the possible large lattice deformation on doping of Tb ion we have co-doped the material with Li. The crystalline nature of the sample has been confirmed by the XRD, Raman and FTIR studies of the material. The variation of bond length and lattice disorder in ZnO lattice due to the substitution of Tb and Li were studied from the EXAFS analysis at Zn K edge and Tb L3 edge. Interestingly, the study also shows that disorder decreases due to co-doping of Li in the considered system. Moreover, the oxidation states of all the elements present in the prepared samples were ascertained the XANES analysis. The morphology and particle size are calculated by TEM characterization. This work mainly emphasises on the structural property of synthesized compositions using these analyses. The study will also be helpful in exploring the change in optical, magnetic and electrical properties of the doped ZnO nanoparticles
As-pyrolyzed sugarcane bagasse possessing exotic field emission properties
No full textThe present study aims to demonstrate the application of sugarcane bagasse as an excellent field emitter. Field emission property of as-pyrolyzed sugarcane bagasse (p-SBg) before and after the plasma treatment has been investigated. It has been observed that electronic nature of p-SBg transformed from semiconducting to metallic after plasma treatment. Maximum current and turn-on field defined at 10 mu A/cm(2) was found to be 800 mu A/cm(2) and 2.2 V/mu m for as-pyrolyzed sugarcane bagasse (p-SBg) and 25 mu A/cm(2) and 8.4 V/mu m for H-2-plasma treated p-SBg. These values are found to be better than the reported values for graphene and activated carbon. In this report, pyrolysis of bagasse has been carried in a thermal chemical vapor deposition (Th-CVD) system in inert argon atmosphere. Scanning electron microscopy (SEM), X-ray Diffraction (XRD), High-resolution transmission electron microscopy (HRTEM) and X-ray photoelectron spectroscopy (XPS) have been used to study the structure of both pre and post plasma-treated p-SBg bagasse's sample. HRTEM study reveals that carbonaceous structures such as 3D-nanographene oxide (3D-NGO), graphite nanodots (GNDs), carbon nanotubes (CNTs), and carbon onions are present in both pre-treated and plasma-treated p-SBg. Hence, we envision that the performed study will be a forwarding step to facilitate the application of p-SBg in display devices