Papers by Prof Narendra Kumar Pandey
Journal of Materials Research, 2022
This research deals with study of enhanced liquefied petroleum gas (LPG) and humidity sensing pro... more This research deals with study of enhanced liquefied petroleum gas (LPG) and humidity sensing properties of Sn-doped NiO pellets synthesized by chemical precipitation route. XRD, FTIR, SEM, and UV–Vis studies were employed to understand the effect of Sn doping on the structural, morphological, and optical properties of the NiO nanoparticles. XRD results revealed that doping of tin in NiO had a significant impact on the crystallite size, peak intensity, strain, lattice parameter, etc. The calculated crystallite size of pure and 3 mol% doped NiO was 33.2 nm and 13.3 nm, respectively. SEM micrographs revealed that the structure of the samples was irregular spheres and non-homogeneous. The dependence of LPG sensing properties on the structural and surface morphological properties has also been studied. The maximum response of 30.46% to 2.0 vol% of LPG was observed at room temperature (300 K). The same sample also shows high humidity sensing response of 87.11% towards 90% RH. Graphic abs...
International Journal of Materials Science and Applications, 2017
Paper reports humidity sensing studies of V 2 O 5-ZnO nanomaterial. When sample of V 2 O 5-ZnO an... more Paper reports humidity sensing studies of V 2 O 5-ZnO nanomaterial. When sample of V 2 O 5-ZnO annealed at 500°C was exposed to increasing humidity, resistance decreased. Aging over six months was within ±6% for ZnO and ±2% for V 2 O 5-ZnO; hysteresis was within ±6% for both ZnO and V 2 O 5-ZnO sensing elements. Grain size for pure ZnO was 620 nm, and 400 nm for V 2 O 5-ZnO nanomaterial. XRD suggested a distribution of crystallite size. For ZnO-V 2 O 5 , distribution in the crystallites size was as wide as 130% compared to only 20% for ZnO. Sensitivity of ZnO-V 2 O 5 nanomaterial was 500% more compared to ZnO sample.
Bulletin of Materials Science, 2017
This study reports the humidity sensing characteristics of ZnO-WO 3 nanocomposite. Pellet samples... more This study reports the humidity sensing characteristics of ZnO-WO 3 nanocomposite. Pellet samples of 0-5 weight% ZnO in WO 3 were sintered from 300 to 600 • C. When exposed to humidity, the resistance of the sensing samples was found to decrease with increase in relative humidity (RH). Five percent ZnO-doped WO 3 showed maximum sensitivity of 20.95 M /%RH in 15-95% RH range. Sensor parameters like reproducibility, aging, hysteresis, response and recovery times were also studied. Sensing mechanism is discussed in terms of sintering temperature, composition and crystallite size of the sensing element. It was observed that sensing mechanism is strongly based on annealing temperature and percentage of doping. The sensing samples have also been investigated by X-ray diffraction, scanning electron microscope (SEM) and Raman spectroscopy. The crystalline size of the sample was identified by powder X-Ray Diffraction data. The SEM analysis was used to study the surface morphology. The structure, phase and the degree of crystallinity of the materials were examined by Raman spectroscopy.
Advanced Materials Research, 2011
Paper reports morphological and relative humidity sensing studies of ZnO-TiO2nanocomposite powder... more Paper reports morphological and relative humidity sensing studies of ZnO-TiO2nanocomposite powder pellets obtained through solid-state reaction route. When exposed to humidity, resistance of pellets decreases with increase in relative humidity from 10-90%. Sensing element with 15 weight % of TiO2in ZnO shows best results with maximum sensitivity of 9.08 MΩ/%RH in 10-90% relative humidity range. This sensing element manifests smallest crystallite size of 71 nm as measured from XRD and lowest grain size of 207 nm calculated from SEM micrograph. This sensing element has the lowest value of activation energy, and hence higher electronic conduction.
Measurement Science and Technology, 2006
Page 1. Optical humidity sensors based on titania films fabricated by solgel and thermal evapora... more Page 1. Optical humidity sensors based on titania films fabricated by solgel and thermal evaporation methods This article has been downloaded from IOPscience. Please scroll down to see the full text article. 2007 Meas. Sci. Technol. 18 260 ...
Bulletin of Materials Science, 2012
This paper reports morphological and relative humidity sensing behaviour of ZnO-TiO 2 nanocomposi... more This paper reports morphological and relative humidity sensing behaviour of ZnO-TiO 2 nanocomposite powder pellets obtained through solid-state reaction route. Resistance of the pellets is observed to decrease with increase in relative humidity in the 10-90% range. Sensing element with 15 wt % of TiO 2 in ZnO shows best results with a sensitivity of 9•08 M /%RH in 10-90% relative humidity range. This sensing element manifests crystallite size of 71 nm as measured from XRD and average grain size of 207 nm calculated from SEM micrograph. This sensing element manifests low hysteresis, less effect of ageing and good reproducibility. Response and recovery times of this sensing element are measured to be 84 s and 396 s, respectively.
Pressure induced microbends have been created in a 50 µm graded index multimode optical fibre wit... more Pressure induced microbends have been created in a 50 µm graded index multimode optical fibre with spatial periodicity Λ = 4.5 mm, embedded in the sample of araldite. If high pressure is applied directly to optical fibre having microbends, it may break, and if pressure is applied to embedded fibre in a solid structure without microbends, the sensitivity is lower. In this paper, a combination of the embedded sensor and microbend sensor is presented. It has the advantage of sensing high pressure on a structure with the sensitivity of a microbend sensor without breaking the optical fibre. It measures pressure up to 1.6 MPa with reproducibility within ± 5% of the measurand. The average sensitivity of the sensor is 5.3/ MPa on an arbitrary scale.
ECP 2023
This article is an open access article distributed under the terms and conditions of the Creative... more This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY
Physica B: Condensed Matter, 2021
Abstract In this work, pure and tungsten (W) doped ZnO nano-crystals have been synthesized throug... more Abstract In this work, pure and tungsten (W) doped ZnO nano-crystals have been synthesized through the co-precipitation technique. The prepared samples are employed to study the effect of tungsten doping on the structural, morphological, and humidity sensing properties of ZnO nanomaterials. The structural and morphological studies have been carried out using X-ray Diffraction (XRD) and Field Emission Scanning Electron Microscopy (FESEM), respectively. The XRD of the synthesized nanomaterials reveals a hexagonal wurtzite structure and a reduction of crystallite size from 44.46 nm to 37.38 nm with increase in doping concentration. The SEM images reveal a cuboidal columnar growth. Finally, the samples have been exposed to a humidity range from 10% to 90% RH and observed that the sensitivity of the sensor is enhanced as the concentration of tungsten is increased. The sample doped with 1.75 mol% tungsten demonstrates the highest sensitivity of 144% among all the samples with good stability.
International Journal of Scientific Research in Physics and Applied Sciences, 2018
MnO 2 doped nanostructured zinc oxide was synthesized by solid state reaction route. The prepared... more MnO 2 doped nanostructured zinc oxide was synthesized by solid state reaction route. The prepared material was characterized by X-ray diffraction, scanning electron microscope and UV-Vis absorption spectroscopy. The doping of MnO 2 in ZnÒ enhanced the crystallization and decreased the crystallite size. Surface morphology of the sensing material showed that the hexagonal shaped particles were uniformly distributed in zinc oxide that left large number of pores. These pores acted as humidity adsorption sites. With increase in the concentration of MnO 2 , the pores also increased. The optical band gap of pure ZnO was 4.05 eV. The value of band gap decreased with increase in the MnO 2 doping concentration. The average sensitivity of undoped zinc oxide was 3400 KΩ/%RH. The sensitivity of the sensing element increased with increase in the doping concentration. Sensitivity of MnO 2 doped ZnO composite is more than four times the sensitivity of pure zinc oxide at annealing temperature 600 o C.
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Papers by Prof Narendra Kumar Pandey