Papers by Dr. Jitender Jindal
CRC Press eBooks, Nov 29, 2022
Department of Chemistry, Maharshi Dayanand University, Rohtak-124 001, Haryana, India E-mail : ve... more Department of Chemistry, Maharshi Dayanand University, Rohtak-124 001, Haryana, India E-mail : [email protected] Departament de Física Aplicada, Universitat Politècnica de València, 46022 València, Spain Manuscript received online 27 November 2014, revised 05 December 2014, accepted 05 December 2014 Porous anodic alumina (PAA) is a versatile template for the fabrication of nanomaterials. To obtain highly ordered nanopore array, two step anodization process is a much less expensive method than other methods like lithography, optical diffraction grating etc. The PAA template was fabricated by two step anodization process. The first step proceeded in oxalic acid to different extent of anodization time and at different voltages to predict the influence of anodization conditions in the first step on the morphology and microstructure of porous anodic alumina film formed in phosphoric acid in the second step. The time varied from 10 to 120 min and voltage varied from 20 to 50 V in th...
Steady state kinetic data from anodic polarization of niobium and tantalum metals under galvanost... more Steady state kinetic data from anodic polarization of niobium and tantalum metals under galvanostatic conditions have been obtained over wide range of temperatures and at different current densities in malic acid electrolyte. The obtained data has been analyzed in the light of various theories of ionic conduction. The value of constant A in Guntherschulze and Betz equation is temperature dependent while B is independent of temperature. The constant A is also dependent on the nature of the electrolyte. The data indicates the temperature independent Tafel slope which rules out the applicability of the single barrier theory of Cabrera and Mott. The data has been analyzed in terms of Dignam's equation. The effects of current density and temperature in aqueous electrolyte on various parameters of Dignam's equation have been examined.
Porous anodic alumina was prepared by two step anodic oxidation process which is much less expens... more Porous anodic alumina was prepared by two step anodic oxidation process which is much less expensive method than other methods like lithography, optical diffraction grating etc to achieve symmetrical pores. The first step of anodization was carried out in 0.3 M oxalic acid at 40 V. In the second step, the anodization was done at constant current density of 5mA/cm 2 for 1 hour in 0.3 M H3PO4. Both the anodization steps were carried out at 15 0 C temperature. The second step anodic oxidation in H3PO4 produced very symmetrical pores. The morphology of porous oxide film was studied by FESEM. The porous anodic alumina was doped with Eu 3+ .The photoluminescence of doped and undoped alumina oxide was studied. The photoluminescence property in PAA membrane is attributed to the presence of F and F + centres.
Porous anodic aluminum oxide film is a versatile template for the fabrication of nanomaterials. P... more Porous anodic aluminum oxide film is a versatile template for the fabrication of nanomaterials. Porous alumina can be fabricated electrochemically through anodic oxidation of aluminum by self-organization method yielding highly ordered arrays of nanoholes. Various techniques such as chemical vapor deposition, electrodeposition, spin coating, dip coating, physical vapor deposition are elaborated for the fabrication of nanomaterials using porous anodic alumina as template.
Ceramics International, 2016
Complex anodic alumina films were preapered by the reanodization of porous anodic oxide films on ... more Complex anodic alumina films were preapered by the reanodization of porous anodic oxide films on aluminium alloy (AA) 5052. The AA 5052 samples were anodized first in H2SO4 for 30 min at 15 V. The reanodization was performed in 0.1 M ammonium pentaborate solution at 15 V for 5 and 10 min. Electrochemical impedance spectroscopy was employed to characterize these complex films. Polarization studies show that the corrosion rate decreases significantly by reanodization and it is further decreases with an increase in reanodization time. Reanodization is found a good method to increase corrosion resistance properties of porous anodic oxide film. Morphologically, no significant difference was observed between simple and complex film as shown in Field Emission Scanning Electron Microscope (FESEM) images. The electrochemical impedance data was fitted with equivalent circuit containing a Constant Phase Element (CPE) and fitted parameters were calculated.
Journal of Physics and Chemistry of Solids, 2021
Abstract ZnO is a versatile photocatalytic material, yet it needed further modifications to explo... more Abstract ZnO is a versatile photocatalytic material, yet it needed further modifications to explore it on the commercial scale. In the present study, photoactive Li doped ZnO nano-materials with different Li content were synthesized by adopting a facile low-temperature solution combustion approach. Li was introduced to improve ZnO characteristics correspond to photocatalytic efficiency. The effect of lithium doping on morphology, crystallinity, chemical state, and optical properties were investigated by utilizing various advanced techniques. The characterization analysis confirms the presence of thermally stable, well-crystalline wurtzite ZnO with a low bandgap and porous nature. Organic dye, Cibacron Red (CR), and a pesticide, Triclopyr (TC) were taken as model pollutants to evaluate the photodegradation performance of all samples under UV light source. Li doped ZnO nanomaterials containing 5 mol% Li attained the highest photocatalytic activity for the removal of both pollutants. The results of the study demonstrate that a strong electronic interaction between Li and ZnO results in the improvement of charge transferability and retards their recombination. The alteration in optical and surface properties of ZnO due to the substitution of Li into ZnO lattice was another reason for the superior activity of Li doped ZnO.
Advanced Coating Materials, 2018
Environmental Chemistry Letters, 2021
Environmental pollution is a serious issue with the rapid development of urbanization, industrial... more Environmental pollution is a serious issue with the rapid development of urbanization, industrialization and vehicle traffic. In particular, fossil fuel pollution increases atmospheric CO2 levels. To alleviate this problem, various carbon capture and storage technologies have been developed, yet they are actually limited by cost and energy requirements. Alternatively, adsorption appears as a promising technique for carbon capture due to its low cost, low energy requirement and applicability over a wide range of temperature and pressure. Here, we review carbonaceous materials such as activated carbon, activated carbon nanofibers, hollow carbon spheres and biochar for CO2 capture, and we discuss factors controlling CO2 adsorption. CO2 adsorption primarily depends upon micropore volume and surface area which in turn are controlled by carbonization and activation temperature, activating agent and its impregnation ratio, activation time and presence of moisture. Additionally, introduction of basic functional groups such as N-containing functional groups into the adsorbent enhances the adsorption capacities. We discuss possible modifications for cost-effective and commercially viable carbon materials as CO2 adsorbents.
Materials Today: Proceedings, 2019
A series of CaAl 2 O 4 :Eu 3+ (1 mol%) co-doped with Er 3+ (0, 1, 2, and 5 mol%) was synthesized ... more A series of CaAl 2 O 4 :Eu 3+ (1 mol%) co-doped with Er 3+ (0, 1, 2, and 5 mol%) was synthesized by urea assisted combustion method at 600°C and further calcinations was done at 1000°C to enhance the crystalline character and luminescence properties. Synthesized samples were characterized structurally and optically using the X-ray diffraction (XRD) and spectrofluorometer respectively. From XRD analysis, monoclinic phase of CaAl 2 O 4 is reported in all the samples indicating that doping of Eu 3+ and Er 3+ do not change the crystalline structure of calcium aluminate. Both Eu 3+ and Eu 2+ states were detected in the synthesized materials whose ratio changes with calcination as well as with co-doping of the Er 3+ ions. CaAl 2 O 4 :Eu 3+ (1 mol%) synthesized at 600°C show high intense peak around 440 nm due to presence of Eu 2+ state, whose intensity decrease with co-doping and upon calcination where as at the same time intensity of peak in the red region due to the presence of Eu 3+ increases. In the compounds calcined at 1000°C, electric dipole 5 D 0 ? 7 F 3 transition of Eu 3+ at 657 nm appears as peak with highest intensity. The Er 3+ ion acts as sensitizer and enhances the luminescent properties of co-doped samples.
Acta Physica Polonica A, 2017
CaAl2O4:Eu 3+ (1 mol.%) co-doped with varying concentration of Gd 3+ (1, 2, 5, and 10 mol.%) were... more CaAl2O4:Eu 3+ (1 mol.%) co-doped with varying concentration of Gd 3+ (1, 2, 5, and 10 mol.%) were prepared by combustion synthesis method at 600 • C and further annealed at 1000 • C. All the compositions were investigated for their structural and photoluminescence properties. It was observed that both states of europium i.e. Eu 3+ and Eu 2+ were present and ratio of these states changes on heating at 1000 • C. The materials synthesized at 600 • C showed high intense peak around 440 nm due to presence of Eu 2+ and less intense peaks in the red region which were due to presence of Eu 3+. On annealing the compounds at 1000 • C, intensity of peak around 440 nm decreases and intensity of peaks in the red region increases significantly. The 5 D0 → 7 F3 transition due to Eu 3+ at 657 nm appears as the highest intensity peak. All co-doped samples annealed at 1000 • C showed the higher intensity than the mono doped sample which is due to energy transfer from the Gd 3+ to Eu 3+. The second rare-earth ion (Gd 3+) acts as sensitizer and enhances the photoluminescence intensity. The X-ray diffraction spectra reveal the monoclinic phase of CaAl2O4 in all the samples which showed that Eu 3+ and Gd 3+ do not change the crystalline structure of calcium aluminate.
Frontiers of Materials Science, 2019
In the past few decades, many novel non-metal doped ZnO materials have developed hasty interest d... more In the past few decades, many novel non-metal doped ZnO materials have developed hasty interest due to their adaptable properties such as low recombination rate and high activity under the solar light exposure. In this article, we compiled recent research advances in non-metal (S, N, C) doped ZnO, emphasizing on the related mechanism of catalysis and the effect of non-metals on structural, morphological, optical and photocatalytic characteristics of ZnO. This review will enhance the knowledge about the advancement in ZnO and will help in synthesizing new ZnO-based materials with modified structural and photocatalytic properties.
Journal of the Australian Ceramic Society, 2018
ZnAl 2 O 4 :Eu 3+ or Tb 3+ (1 mol%) and ZnAl 2 O 4 :Eu 3+ /Tb 3+ with varied concentrations of Eu... more ZnAl 2 O 4 :Eu 3+ or Tb 3+ (1 mol%) and ZnAl 2 O 4 :Eu 3+ /Tb 3+ with varied concentrations of Eu 3+ and Tb 3+ were prepared by solution combustion method. The photoluminescence spectra of synthesized compounds shows that simultaneous doping of Tb 3+ and Eu 3+ causes enhancement in Eu 3+ luminescence intensity. This indicates some energy transfer from Tb 3+ to Eu 3+. This phenomenon of Tb 3+ → Eu 3+ energy transfer, accomplishing enhanced intensity of Eu 3+ ions, is attributed to the cross relaxation phenomenon, which is favored by overlap between the donor and acceptor transition. The energy is transferred to Eu 3+ cascade rapidly via non-radiative transitions to 5 D 0 state. The synthesized compounds were characterized by XRD, SEM for their structural and morphological characteristics respectively.
Ceramics International, 2016
Yb 3+ doped ZnO/MgO nanocomposite were prepared by combustion synthesis method. The samples were ... more Yb 3+ doped ZnO/MgO nanocomposite were prepared by combustion synthesis method. The samples were further heated to 1000 ºC to improve their crystallinity and photoluminescent efficiency. The concentrations of Yb 3+ and Mg 2+ were varied between 1 to 2% and 5 to 70% respectively in prepared samples. The nano-powders were characterized by Scanning Electron Microscopy and X Ray Diffraction for morphology and structural determination. XRD studies have revealed the wurtzite structure for Mg x Zn 1-x O for Mg concentrations below 30 %. Higher concentrations of Mg results in Yb 3+ doped ZnO/MgO nanocomposite containing three phases; the wurzite hexagonal phase typical of ZnO, the cubic phase of MgO and a small amount of cubic Yb 2 O 3 phase. As expected, the amount of cubic phase in nano-powders increased with the increase of Mg concentration in ZnO. The crystallite size of ZnO/MgO composites decreased from 55 nm to 30 nm with increase of Mg content. SEM images of Yb 3+ doped ZnO/MgO nanocomposite with higher Mg content (> 50%) showed clearly distinct hexagonal and cubical shaped nano-particles. Photoluminescent emission showed a broad band in the range (435 nm to 700 nm). Pure ZnO nano-phosphor showed an emission peak around 545 nm, which is blue shifted with Mg content. The photoluminescence intensity increased with increase of Mg content in ZnO and it became maximum with 30% Mg concentration. Time resolved decay curves of photoluminescence indicated decay time in microsecond time scale.
The micro structural properties of nanoporous anodic oxide film formed in H3PO4 were highly influ... more The micro structural properties of nanoporous anodic oxide film formed in H3PO4 were highly influenced by addition of a low concentration of KMnO4 (0.0005 M) in 1 M H3PO4 solution. The KMnO4 as additive enhanced the growth rate of oxide film formation as well as thickness of pore walls. Furthermore the growth rate was found increased with increase in applied current density. The increase in temperature and lack of stirring during anodization causes the thinness of pore wall which leads to increase in pore volume. With the decrease in concentration of H3PO4 in anodizing electrolyte from 1M to 0.3 M, keeping all other conditions constant, the decrease in porosity was observed. This might be due to the dissolution of aluminium oxide film in highly concentrated acidic solution.
AIP Conference Proceedings, 2016
Ta 2 O 5 :Eu 3+ : Mg 2+ or Ca 2+ phosphor materials were prepared by molten salt method using KCl... more Ta 2 O 5 :Eu 3+ : Mg 2+ or Ca 2+ phosphor materials were prepared by molten salt method using KCl as flux. The Xray diffraction (XRD) patterns illustrated that the well crystallized Ta 2 O 5 :Eu 3+ : Mg 2+ or Ca 2+ were formed in the presence of flux under reduced temperature (800 ºC) in contrast to conventional solid state method (1200-1500 ºC). Scanning electron microscope (SEM) images indicate the achievement of well dispersed particles (hexagonal tablet and rod-like structures). Meanwhile, the photo-luminescent studies demonstrated that Ta 2 O 5 is an efficient host to sensitize europium red emissions. The addition of Mg 2+ or Ca 2+ as co-dopant enhanced the luminescent intensity of Ta 2 O 5 : Eu 3+ compound.
Acta Physica Polonica A, 2016
The anodic oxide films were prepared on the niobium and tantalum in aqueous electrolyte mixtures ... more The anodic oxide films were prepared on the niobium and tantalum in aqueous electrolyte mixtures containing 1 M CH3COOH + 1 M H3PO4 or 1 M CH3COOH + 1 vol.% HF or 1 M CH3COOH + 1 M H3PO4 + 1 vol.% HF at 30 V for 30 min. The barrier films were obtained on both niobium and tantalum surfaces in all electrolyte mixtures except niobium oxide film formed in 1 M CH3COOH + 1 vol.% HF which is porous in nature. The anodic oxide films were characterized by FESEM. Also, electrochemical impedance spectroscopy at open-circuit potential on Nb and Ta was applied and obtained data were analyzed by fitting with four different equivalent circuits.
The Zn(1-x-y)MoO4:Eu3+(x): Y3+(y) (x = 1 mol% and y = 1 or 2 mol%) compounds were prepared by com... more The Zn(1-x-y)MoO4:Eu3+(x): Y3+(y) (x = 1 mol% and y = 1 or 2 mol%) compounds were prepared by combustion synthesis method. The crystal structure of the samples was identified by X-ray diffraction (XRD). The photoluminescence properties were investigated and it is observed that the co-doping of Y3+ enhances the luminescence emission intensity of ZnMoO4:Eu3+ material. The Y3+ acts as a sensitizer in the ZnMoO4:Eu3+ lattice. The particle size is calculated from XRD data by using Scherer Equation. The particles has been found in the range of 30-40 nm.
Transactions of the Indian Ceramic Society, 2015
BaAl 2 O 4 :Eu 2+ /Eu 3+ (1 mol %) co-doped with varying concentrations of Gd 3+ (1, 2, 5 and 10 ... more BaAl 2 O 4 :Eu 2+ /Eu 3+ (1 mol %) co-doped with varying concentrations of Gd 3+ (1, 2, 5 and 10 mol%) were prepared by combustion synthesis method at 600 o C. All the compositions were investigated for their structural and photoluminescence properties. Samples prepared in open atmosphere showed the presence of both Eu 3+ and Eu 2+ states which indicates the reduction of Eu 3+ to Eu 2+ during the preparation of these compounds. The prepared materials at 600 o C showed high intense broad peaks around 498 nm corresponding to Eu 2+ and small peaks in the red region which are attributed to the presence of Eu 3+. In the 1000 o C annealed compounds, the intensity of the peak at 498 nm got increased. The intensity of this broad band for BaAl 2 O 4 :Eu 2+ /Eu 3+ (1 mol%):Gd 3+ (1 mol%) was three times than that of BaAl 2 O 4 :Eu 2+ /Eu 3+ (1 mol%). Thus second rare earth ion (Gd 3+) acted as a good sensitizer and enhanced the photoluminescence intensity. The XRD spectra revealed the presence of hexagonal phase of BaAl 2 O 4 as main phase and a small amount of a mixed phase Ba O! 6.6 Al 2 O 3. Doping of Eu 3+ , Gd 3+ did not change the crystalline structure of barium aluminate (BaAl 2 O 4).
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Papers by Dr. Jitender Jindal