41 research outputs found
Iron environment non-equivalence in both octahedral and tetrahedral sites in NiFe2O4 nanoparticles: study using Mössbauer spectroscopy with a high velocity resolution
Mössbauer spectrum of NiFe2O4 nanoparticles was measured at room temperature in 4096 channels. This spectrum was fitted using various models, consisting of different numbers of magnetic sextets from two to twelve. Non-equivalence of the 57Fe microenvironments due to various probabilities of different Ni2+ numbers surrounding the octahedral and tetrahedral sites was evaluated and at least 5 different microenvironments were shown for both sites. The fit of the Mössbauer spectrum of NiFe 2O4 nanoparticles using ten sextets showed some similarities in the histograms of relative areas of sextets and calculated probabilities of different Ni2+ numbers in local microenvironments. © 2012 American Institute of Physics
Nitrogen-doped Multi-walled Carbon Nanotubes-MnCo2O4 microsphere as electrocatalyst for efficient oxygen reduction reaction
Nitrogen-doped Multi-walled Carbon Nanotubes (N-doped MWCNT)/MnCo2O4 hybrid is synthesized by a facile hydrothermal method. The X-ray diffraction studies revealed the single phase formation of cubic spinel structured MnCo2O4 and their composites. The presence of D and G band of MWCNT is identified through Raman spectral analysis. The elemental oxidation state and nitrogen content is obtained using X-ray photoelectron spectroscopy, which elucidates that Co and Mn exists in multivalence state and the nitrogen functional groups are in pyrolytic and pyridinic-type. FE-SEM shows the microsphere formation of MnCo2O4 and size exhibits in the range of 6-9 μm. The N-doped MWCNT/MnCo2O4 hybrid catalyst exhibits an improved oxygen reduction electrocatalytic activity in an aqueous alkaline medium when compared with pristine MnCo2O4. © 2016 Hydrogen Energy Publications LLC.1
Suitability of Clustering Algorithms for Crime Hotspot Analysis
Abstract-Crime analysis is a field that needs immediate attention due to the drastic increase of number of crimes. Most of the crimes, from the past experiences of the police, are said to be concentrated in some areas, called hotspots and keep on recurring. Clustering algorithms are best applied to crime analysis, but suitability of broad spectrum of clustering algorithm for an application is an issue to be addressed. In this paper we evaluate three clustering algorithms i.e. hierarchical clustering, k-means clustering and DBSCAN clustering with the intent of finding the best one suitable for crime hotspot analysis. Each one of the clustering algorithm evaluated here need inputs such as number of clusters, neighbour distance, minimum number of points etc. are needed by a cluster. The cluster similarity measure is the Euclidean distance. The results suggest that DBSCAN is much more suitable to crime hotspot analysis due to its inherent nature of being density driven
Critical behavior of resistivity in the pressure-induced first to second order transition in Pr0.6Ca0.4Mn0.96B0.04O3(B = Co and Cr)
10.1016/j.jallcom.2014.08.112Journal of Alloys and Compounds618159-16
Synthesis of Bi2WO6 nanoparticles and its electrochemical properties in different electrolytes for pseudocapacitor electrodes
Nanosized Bi2WO6 particles were successfully synthesized by sonochemical method with an objective to
develop an inexpensive and eco-friendly electrode material for supercapacitors. The prepared material
was subjected to various thermal, structural, morphological, compositional, electrical and electrochemical
studies. Bi2WO6 nanoparticle with homogeneous distribution was achieved through sonochemical
process. The lattice parameter and atomic positions of Bi2WO6 structure were refined through Reitveld
analysis. The electrochemical performance of Bi2WO6 nanoparticles was investigated in various aqueous
electrolytes such as 1 M NaOH, 1 M LiOH, 1 M Na2SO4, 1 M KOH and 6 M KOH solutions. Among these,
the material exhibited an enhanced electrochemical performance in KOH electrolyte due to its smaller
hydration sphere radius, high ionic mobility and lower equivalent series resistance. The charge–discharge
studies rendered a specific capacitance of 608 F/g in 1 M KOH at a current density of 0.5 mA/cm2. Bi2WO6
exhibited an excellent coulombic efficiency and specific capacitance of around 304 F/g at 3 mA/cm2 in
the potential range from
−0.9 to 0.1 V vs Hg/HgO in 1 M KOH electrolyte. The above results assured that
Bi2WO6 could be utilized as suitable negative electrode material for supercapacitor applications and 1 M
KOH could be its desirable electrolyt
Mössbauer and D.C. magnetization studies of (CuFe2O4)1−x (SnO2)x (x=0 and 5 wt.%) nanocomposites
Mossbauer spectroscopy of NiFe2O4 nanoparticles: The effect of Ni2+ in the Fe3+ local microenvironment in both tetrahedral and octahedral sites
Two samples of combustion synthesized nickel ferrite nanoparticles were characterized using X-ray diffraction, scanning and transmission electron microscopy, magnetization measurements and MOssbauer spectroscopy with a high velocity resolution. It was shown that MOssbauer spectra of nickel ferrite can be well fitted by using ten magnetic sextets related to the different numbers of Ni2+ cations in the Fe3+ local microenvironments in both tetrahedral and octahedral sites supported by calculations of such probabilities. it was shown that increase of the number of Ni2+ cations in the Fe-57 local microenvironment around both sites leads to decrease of the hyperfine field. (C) 2017 Elsevier B.V. All rights reserved
High Performance Solid-State Electric Double Layer Capacitor from Redox Mediated Gel Polymer Electrolyte and Renewable Tamarind Fruit Shell Derived Porous Carbon
The
activated carbon was derived from tamarind fruit shell and utilized
as electrodes in a solid state electrochemical double layer capacitor
(SSEDLC). The fabricated SSEDLC with PVA (polyvinyl alcohol)/H<sub>2</sub>SO<sub>4</sub> gel electrolyte delivered high specific capacitance
and energy density of 412 F g<sup>‑1</sup> and 9.166 W h kg<sup>‑1</sup>, respectively, at 1.56 A g<sup>‑1</sup>. Subsequently,
Na<sub>2</sub>MoO<sub>4</sub> (sodium molybdate) added PVA/H<sub>2</sub>SO<sub>4</sub> gel electrolyte was also prepared and applied for
SSEDLC, to improve the performance. Surprisingly, 57.2% of specific
capacitance (648 F g<sup>‑1</sup>) and of energy density (14.4
Wh kg<sup>‑1</sup>) was increased while introducing Na<sub>2</sub>MoO<sub>4</sub> as the redox mediator in PVA/H<sub>2</sub>SO<sub>4</sub> gel electrolyte. This improved performance is owed
to the redox reaction between Mo(VI)/Mo(V) and Mo(VI)/Mo(IV) redox
couples in Na<sub>2</sub>MoO<sub>4</sub>/PVA/H<sub>2</sub>SO<sub>4</sub> gel electrolyte. Similarly, the fabricated device shows the excellent
capacitance retention of 93% for over 3000 cycles. The present work
suggests that the Na<sub>2</sub>MoO<sub>4</sub> added PVA/H<sub>2</sub>SO<sub>4</sub> gel is a potential electrolyte to improve the performance
instead of pristine PVA/H<sub>2</sub>SO<sub>4</sub> gel electrolyte.
Based on the overall performance, it is strongly believed that the
combination of tamarind fruit shell derived activated carbon and Na<sub>2</sub>MoO<sub>4</sub>/PVA/H<sub>2</sub>SO<sub>4</sub> gel electrolyte
is more attractive in the near future for high performance SSEDLCs
Facile synthesis of monodispersed 3D hierarchical Fe3O4 nanostructures decorated r-GO as the negative electrodes for Li-ion batteries
One-pot solvothermal process is adopted to develop, 3D hierarchical Fe3O4 nanoparticles supported 2D reduced
graphene oxide sheets (Fe3O4/r-GO) as possible negative electrodes for lithium ion batteries. The synthesis
parameters are optimized to prepare agglomeration-free Fe3O4 nanostructures with uniform size and shape on r-
GO. The field emission scanning electron microscopic (FESEM) image reveals that the 3D hierarchical Fe3O4
nanostructures are uniformly decorated on r-GO. The physicochemical and functional properties of Fe3O4/r-GO
are systematically investigated using various techniques. The fabricated Fe3O4/r-GO electrode delivers an initial
discharge capacity of 1221 mAh g−1 at a current density of 100 mA g−1 and retains the specific capacity of
1560 mAh g−1 after 100 cycles. Fe3O4/r-GO significantly enhances cyclic performance, when compared with
bare Fe3O4 nanoparticles due to the uniform distribution of Fe3O4 nanoparticles on the graphene sheet with the
more number of electrochemically active sites.114Nsciescopu
High Performance Solid-State Electric Double Layer Capacitor from Redox Mediated Gel Polymer Electrolyte and Renewable Tamarind Fruit Shell Derived Porous Carbon
The
activated carbon was derived from tamarind fruit shell and utilized
as electrodes in a solid state electrochemical double layer capacitor
(SSEDLC). The fabricated SSEDLC with PVA (polyvinyl alcohol)/H<sub>2</sub>SO<sub>4</sub> gel electrolyte delivered high specific capacitance
and energy density of 412 F g<sup>‑1</sup> and 9.166 W h kg<sup>‑1</sup>, respectively, at 1.56 A g<sup>‑1</sup>. Subsequently,
Na<sub>2</sub>MoO<sub>4</sub> (sodium molybdate) added PVA/H<sub>2</sub>SO<sub>4</sub> gel electrolyte was also prepared and applied for
SSEDLC, to improve the performance. Surprisingly, 57.2% of specific
capacitance (648 F g<sup>‑1</sup>) and of energy density (14.4
Wh kg<sup>‑1</sup>) was increased while introducing Na<sub>2</sub>MoO<sub>4</sub> as the redox mediator in PVA/H<sub>2</sub>SO<sub>4</sub> gel electrolyte. This improved performance is owed
to the redox reaction between Mo(VI)/Mo(V) and Mo(VI)/Mo(IV) redox
couples in Na<sub>2</sub>MoO<sub>4</sub>/PVA/H<sub>2</sub>SO<sub>4</sub> gel electrolyte. Similarly, the fabricated device shows the excellent
capacitance retention of 93% for over 3000 cycles. The present work
suggests that the Na<sub>2</sub>MoO<sub>4</sub> added PVA/H<sub>2</sub>SO<sub>4</sub> gel is a potential electrolyte to improve the performance
instead of pristine PVA/H<sub>2</sub>SO<sub>4</sub> gel electrolyte.
Based on the overall performance, it is strongly believed that the
combination of tamarind fruit shell derived activated carbon and Na<sub>2</sub>MoO<sub>4</sub>/PVA/H<sub>2</sub>SO<sub>4</sub> gel electrolyte
is more attractive in the near future for high performance SSEDLCs