Positron annihilation studies of NiO nanoparticles prepared through two different chemical routes

Das, Soumen; Ghoshal, Tandra; Nambissan, P.M.G.

doi:10.1002/pssc.200982134

Cited by 12 publications

(6 citation statements)

References 8 publications

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“…We had similar observations in a few earlier works too [13,14] but the present one is remarkable. The intensity I 2 of the component had fallen too, as if the effect is one of defect agglomeration.…”

Section: Positron Lifetime Measurementssupporting

confidence: 89%

“…The values of E g and its changes with the changes in particle sizes are typically identical in nature and magnitude to similar changes due to the occurrence of quantum confinement effects observed earlier in certain other nanomaterial systems. [13,14] Especially, in semiconductor nanoparticles, such effects directly manifest as increases in bandgap energy (E g ), and the increase usually is of the order of 0.1-1.0 eV. This happens when the particle sizes are reduced to below the exciton Bohr diameter of the material, as explained later.…”

Section: Optical Absorption Measurementsmentioning

confidence: 98%

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Positron annihilation studies of defects and fine size effects in nanocrystalline nickel oxide

Das¹,

Mandal

Roy

et al. 2013

Journal of Experimental Nanoscience

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Ultrafine nickel oxide nanoparticles were prepared by sol-gel method using a solution of nickel nitrate hexahydrate and ammonium hydroxide and subsequently annealed in air at different temperatures in the range 200-275 C for different hours to vary the particle sizes. They were characterised for phase, purity, structure and sizes by X-ray diffraction and high-resolution transmission electron microscopy. They were found polycrystalline in nature and possessed face-centred cubic (NaCl-type) structure with lattice parameter varying with annealing temperature. The ultrafine structure clearly revealed the formation of hexagons with average diameter about 5 nm. Ultraviolet-visible absorption spectroscopy was carried out to study the optical properties and for the estimation of the bandgap. The nanoparticles exhibited weak and strong quantum confinement in the size ranges of 10.47-8.47 and 6.57-5 nm. The samples were then investigated through positron annihilation spectroscopy to characterise and closely monitor the evolution of vacancy-type defects and defect clusters during particle growth in the samples. The positron lifetime drastically increased at very low particle sizes, supporting the confinement effects demonstrated by optical absorption studies. The results from coincidence Doppler broadening measurements were consistent and indicated changes also in the electron momentum distribution during the occurrence of these finite size effects in the nanoparticles.

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Section: Positron Lifetime Measurementssupporting

confidence: 89%

Section: Optical Absorption Measurementsmentioning

confidence: 98%

Positron annihilation studies of defects and fine size effects in nanocrystalline nickel oxide

Das¹,

Mandal

Roy

et al. 2013

Journal of Experimental Nanoscience

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“…Due to the chemical and physical properties, NiO nanoparticles have a wide range of applications, such as nickel zinc ferrite (Ni x Zn 1− x Fe 2 O 4 ) for magnetic materials, nickel sulphamate for electroplating solutions, nickel molybdate for hydro‐desulphurization catalyst, gold‐doped nickel oxide film for transparent electrodes in optoelectronic devices, in cermet anode for solid oxide fuel cell, solar thermal absorber, catalyst for O 2 evolution, gas sensors and in lithium‐ion batteries . Different methods have been reported for the synthesis of NiO nanoparticles, such as solvothermal and sol–gel, using acetic or citric acid . The interest in nanoparticles of NiO and its compounds is mainly due to their high physico‐chemical activity in various applications listed above as a result of high surface area, and also because of ease with which it can be sintered at low temperatures to high density.…”

Section: Introductionmentioning

confidence: 99%

Novel Ion‐Exchange Process for the Preparation of Metal Oxide Nanopowders from Sodium Alginate

2012

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A novel and generic sol-gel method has been developed for the production of high purity metal oxide nanopowders using sodium alginate. This has been demonstrated successfully employing nickel oxide (NiO) as a model material in this instance. The results of this investigation indicate that the final particle size of~20 nm can be obtained after calcination of the predried beads at 500°C for 3 h in ambient air. An insight into the calcination process has been obtained using simultaneous thermo-gravimetric analysis and differential scanning calorimetry (TGA/DSC) and high temperature X-ray diffraction (HT-XRD). Powder X-ray diffraction (XRD) confirms that the obtained samples are single phase cubic NiO powders with no trace of impurity. During the phase transformation, NiO + NiO 2 have been found to coexist between 250°C and 350°C and a reaction scheme is proposed to account for this. The mean crystallite sizes calculated from XRD analysis using Rietveld refinement method is in good agreement with the morphological features observed using transmission electron microscopy (TEM). The NiO nanopowders produced in this study exhibit negligible strain as indicated using Rietveld refinement procedure. The XRD and TEM analyses indicate that there is a significant influence of calcination temperature and time on the particle size, which increases with increasing temperature and annealing time. This new sol-gel method is a simple, environmentally friendly, and nontoxic route for a large scale production of high purity single phase nanopowders in a cost-effective manner at significantly low temperatures. The process described in this study can yield 200 kg of NiO nanopowders per ton of dried Ni-ALG beads.J. Nino-contributing editor Manuscript No. 30902.

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“…Due to the chemical and physical properties, NiO nanoparticles have a wide range of applications, such as nickel zinc ferrite (Ni x Zn 12x Fe 2 O 4 ) for magnetic materials, 1 nickel sulfamate for electroplating solutions, nickel molybdate for hydro-desulfurization catalysts, 2 gold-doped nickel oxide film for transparent electrodes in optoelectronic devices, in cermet anodes for SOFC, 3 solar thermal absorber, 4 catalyst for O 2 evolution, 5 gas sensors, 6,7 and in lithium-ion batteries. 8 Different methods have been reported for the synthesis of NiO nanoparticles, such as solvothermal 9 and sol-gel using acetic 9 or citric acid. 10 The interest in nanoparticles of NiO is mainly due to their high physico-chemical activity in various applications listed above as a result of high surface area and also because of ease with which it can be sintered at low temperatures to high density.…”

Section: Introductionmentioning

confidence: 99%

X-Ray micro-tomography of freeze dried nickel alginate beads and transformation into NiO nanopowders

et al. 2012

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A generic ion-exchange mediated sol-gel method has been developed for the production of high purity nickel and other metal oxide nanopowders using sodium alginate precursor. X-Ray microtomography (XMT) shows that the nickel ions have been uniformly cross-linked in the alginate structure and remained stable after freeze drying as evidenced by the bright green color of the freeze dried beads. The freeze dried nickel alginate beads exhibit a porous foam-like structure composing of a thin nickel alginate film and a dominant fraction of voids. The porous nickel alginate beads when calcined at 700 uC for 1 h in ambient air yielded spherical nickel oxide nanoparticles of y50 nm in size. Powder X-ray diffraction (XRD) confirms that the sample is single phase cubic NiO powders with no trace of impurity. The mean crystallite sizes calculated from XRD analysis using the Rietveld refinement method agree with the morphological features observed by transmission electron microscopy (TEM).

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Positron annihilation studies of NiO nanoparticles prepared through two different chemical routes

Cited by 12 publications

References 8 publications

Positron annihilation studies of defects and fine size effects in nanocrystalline nickel oxide

Positron annihilation studies of defects and fine size effects in nanocrystalline nickel oxide

Novel Ion‐Exchange Process for the Preparation of Metal Oxide Nanopowders from Sodium Alginate

X-Ray micro-tomography of freeze dried nickel alginate beads and transformation into NiO nanopowders

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