Lakhwant Singh | Guru Nanak Dev University Amritsar (original) (raw)

Papers by Lakhwant Singh

Nucleation and Atmospheric Aerosols, 2018

arXiv (Cornell University), Jun 25, 2019

Indian Journal of Pure & Applied Physics, Feb 22, 2016

Journal of Macromolecular Science, Part B, Jun 7, 2016

ABSTRACT Bisphenol-A polycarbonate films were irradiated with 86 MeV swift heavy nickel ions at v... more ABSTRACT Bisphenol-A polycarbonate films were irradiated with 86 MeV swift heavy nickel ions at varying fluences, ranging from 1 × 1011 to 1 × 1013 ions cm−2, under vacuum at room temperature, to analyze the induced electrical and thermal modifications. AC conductivity measurements and UV-visible spectroscopy, Fourier transform infra-red (FTIR) spectroscopy, thermo-gravimetric analysis (TGA), differential scanning calorimetry (DSC), and X-ray diffraction (XRD) techniques were applied to analyze the changes. A significant, exponential increase in conductivity at higher frequency was observed with the increase of nickel ion fluence. UV-visible analysis corroborated the results of the AC conductivity measurement, revealing the increase in size of the carbon clusters embedded in the polymer network, with the increase of heavy ion fluence. FTIR analysis revealed the formation of alkene and alkyne end groups at higher doses, which further supported the suggestion that the variation in electrical properties induced by the ion irradiation of the polymer was due to development of a carbonaceous phase inside the polymer due to the irradiation. Thermal analysis, i.e., TGA and DSC patterns, showed that chain-scission was the leading phenomena in the heavy ion-irradiated polycarbonate samples, resulting in degradation of their thermal stability.

Journal of Macromolecular Science, Part B, Nov 11, 2019

Journal of Molecular Structure, 2022

Abstract A series of tissue equivalent novel Sr(1-x)B4O7:Hox (0 ≤ x ≤ 0.5 mol%) phosphors have be... more Abstract A series of tissue equivalent novel Sr(1-x)B4O7:Hox (0 ≤ x ≤ 0.5 mol%) phosphors have been synthesized via solid state diffusion to investigate their structural and Thermoluminescence features. The rietveld refinement of XRD data confirms pure phase formation with an orthorhombic crystal structure. FTIR and Raman spectroscopy have been used to examine the vibration characteristics and bonding among each constituent of material. The analysis detected bending vibrations of bridging oxygen's within B-O-B bonds in BO3 trigonals, alongwith stretching vibrations of [BO4] tetrahedral. SEM was used to inquire the surface morphology as well as to record EDX patterns for authentication of the elemental composition in all the samples. The microphosphors possess a dense structure with irregularly shaped grains with an average grain size of 1.36-1.45μm. The TL glow curves have been recorded to evaluate the dosimetric properties of γ-exposed phosphors i.e. dose response, fading and reproducibility. Doped samples exhibit higher TL sensitivity as compared to pure samples. The critical holmium concentration for TL was found to be 0.5 mol%. Fading was examined and the TL intensity of the predominant dosimetric TL Peak of SB3 sample was determined to be a -12% decline after 15 days. Repetitive analysis demonstrates that SrB4O7 have high reproducibility. The phosphors exhibit a linear dose response and good reproducibility, with a standard deviation of ∼2%. The trapping parameters (viz. E, b and s) have been computed using PS, IR and Ilich methods. The dosimetric attributes of the novel fabricated phosphors acknowledge their adequacy for dosimetry applications.

Optical Materials, Oct 1, 2021

Abstract The purpose of this study is to synthesize Mg(1-x)O:xLi+ (x = 0, 1, 2 and 3 mol%) lumino... more Abstract The purpose of this study is to synthesize Mg(1-x)O:xLi+ (x = 0, 1, 2 and 3 mol%) luminophors using Solution Combustion Synthesis(SCS) and investigate their potential applications in WLEDs and radiation dosimetry. The single phase (cubic) formation of samples is confirmed by Rietveld refinement of XRD data recorded at room temperature. The vibration characteristics are investigated by Fourier transform infrared spectroscopy. The diffuse reflectance spectra are recorded to calculate the values of the energy band gap of pristine and gamma exposed samples. SEM Micrographs reveal the formation of non-uniform shaped grains and a decrease in grain size with an increment in dopant concentration. Photoluminescence (PL) emission spectra exhibit broad bands around ~398 nm and ~485 nm that are ascribed to various defects in the MgO lattice. The influence of concentration on PL intensity indicates that 1 mol% dopant concentration is optimal. The CIE coordinates located in the blue region advocate the suitability of prepared samples for application in WLEDs. The dosimetric properties such as batch homogeneity, dose response and fading along with the influence of different γ-doses and dopant concentration on the TL intensity of γ-exposed luminophors are explored using recorded thermoluminescence (TL) glow curves of all samples. TL glow curves of lithium incorporated MgO at gamma doses of 50–500Gy show peaks around 150ᵒ-180ᵒ C. Besides, a shoulder peak ~300 °C is observed at higher doses > 1 kGy. Fading analysis indicates that maximum fading of ~10% is detected in the first 48 h s after the irradiation with decrement up to 75% on 15th day. The kinetic parameters of sample ML2 are calculated using three different techniques: the peak shape method, initial rise and the Ilich method.

Journal of Applied Physics, Sep 3, 2013

Gamma ray induced modifications in natural phlogopite mica have been studied in the dose range of... more Gamma ray induced modifications in natural phlogopite mica have been studied in the dose range of 1–2000 kGy. These modifications were monitored using different techniques viz: ultraviolet-visible spectroscopy, Fourier Transform Infrared spectroscopy, dielectric measurements, X-ray diffraction, and thermoluminescence dosimeter. The analysis of the results reveals that the dose of 100 kGy produces significant change in the natural phlogopite mica as compared to pristine and other exposed samples. Ultraviolet-visible analysis provides the value of optical indirect, direct band gap, and Urbach energy. Cody model was used to calculate structural disorder from Urbach energy. Different dielectric parameters such as dielectric constant, dielectric loss, ac conductivity, and real and imaginary parts of electric modulus were calculated for pristine and irradiated samples at room temperature. Williamson Hall analysis was employed to calculate crystallite size and micro-strain of pristine and irradiated sheets. No appreciable changes in characteristic bands were observed after irradiation, indicating that natural phlogopite mica is chemically stable. The natural phlogopite mica may be recommended as a thermoluminescent dosimeter for gamma dose within 1 kGy–300 kGy.

Journal of Alloys and Compounds, Mar 1, 2021

Indian Journal of Physics, Jul 1, 2009

Radiation Physics and Chemistry, Jun 1, 2013

Nucleation and Atmospheric Aerosols, 2020

Physica B-condensed Matter, Nov 1, 2012

ABSTRACT

Optical Materials, Mar 1, 2016

Abstract Trivalent Dysprosium doped sodium aluminophosphate glasses with composition 50P2O5-10Al2... more Abstract Trivalent Dysprosium doped sodium aluminophosphate glasses with composition 50P2O5-10Al2O3-(20-x)Na2O-20CaO-xDy2O3 (x varying from 0 to 5 mol%) were prepared by melt quench technique. The density of the prepared samples was measured using Archimedes principle and various physical properties like molar volume, rare earth ion concentration, polaron radius, inter nuclear distance and field strength were calculated using different formulae. The differential scanning calorimetry (DSC) was carried out to study the thermal stability of prepared glasses. The UV Visible absorption spectra of the dysprosium doped glasses were found to be comprised of ten absorption bands which correspond to transitions from ground state 6H15/2 to various excited states. The indirect optical band gap energy of the samples was calculated by Tauc’s plot and the optical energy was found to be attenuated with Dy3+ ions. The photoluminescence spectrum revealed that Dy3+ doped aluminophosphate glasses have strong emission bands in the visible region. A blue emission band centred at 486 nm, a bright yellow band centred at 575 nm and a weak red band centred at 668 nm were observed in the emission spectrum due to excitation at 352 nm wavelength. Both FTIR and Raman spectra assert slight structural changes induced in the host glass network with Dy3+ ions.

Journal of Non-crystalline Solids, Nov 1, 2015

Abstract Photocatalytic glass–ceramics were obtained by subjecting (70B2O3–29Bi2O3–1Dy2O3)–xBT (w... more Abstract Photocatalytic glass–ceramics were obtained by subjecting (70B2O3–29Bi2O3–1Dy2O3)–xBT (where BT corresponds to BaO–TiO2) glasses to a suitable heat treatment. X-ray diffraction studies revealed that the glasses heat treated at 570 °C for 24 h gave rise to a crystalline phase of Ba2Ti6O13 embedded in the host glass matrix. The optical absorption measurements carried out on the well-polished samples show a decrease in the optical band gap energy with an increase in BT content. The analysis of the FTIR and Raman spectra of these glass ceramics indicated the presence of mainly BiO6, BiO3, BO3 and BO4 units in the glass network. The study of their spectra also showed that the BT acts as a modifier in the glass network The prepared glass ceramics efficiently decomposed ciprofloxacin under UV irradiation and their decomposition ability was found to increase with an increase in the BT content. The degradation coefficient of glass ceramic with 20% BT content (268 min− 1 m− 2) was observed to be ten times higher than the as quenched glass (24 min− 1 m− 2) and the crystallized glass without BT (18 min− 1 m− 2). The photocatalytic studies carried on these glass ceramics suggested their role as self cleaning glasses.