68,077 research outputs found
Effect of Salt Concentration on Dielectric Properties of Li-Ion Conducting Blend Polymer Electrolytes
In the present article, we have studied the effect of the salt concentration
(LiPF6) on transport properties and ion dynamics of blend solid polymer
electrolyte (PEO PAN) prepared by solution cast technique. Fourier transform
infrared (FTIR) spectroscopy confirms the presence of microscopic interactions
such as polymer ion and ion ion interaction evidenced by a change in peak area
of anion stretching mode. The fraction of free anions and ion pairs obtained
from the analysis of FTIR implies that both influence the ionic conductivity
with different salt concentration. The complex dielectric permittivity,
dielectric loss, complex conductivity have been analyzed and fitted in the
entire frequency range (1 Hz to 1 MHz) at room temperature. The addition of
salt augments the dielectric constant and shift of relaxation peak in loss
tangent plot toward high frequency indicates a decrease of relaxation time. We
have implemented the Sigma representation sigma double prime vs sigma prime for
solid lithium ion conducting films which provide better insight toward
understating of the dispersion region in Cole Cole plot epsilon double prime vs
epsilon prime in lower frequency window. The dielectric strength, relaxation
time and hopping frequency are in correlation with the conductivity which
reveals the authenticity of results. Finally, the ion transport mechanism was
proposed for getting the better understanding of the ion migration in the
polymer matrix.Comment: Journal of Materials Science: Materials in Electronics, 201
Structural, Electrical Properties and Dielectric Relaxation in Na+ Ion Conducting Solid Polymer Electrolyte
Present paper reports, the structural, microstructural, electrical,
dielectric properties and ion dynamics of a sodium based solid polymer
electrolyte films comprising of PEO8-NaPF6+ x wt. % SN. The structural and
surface morphology properties have been investigated by XRD and FESEM.
Different microscopic interaction among the polymer, salt and SN have been
analyzed through FTIR. The dielectric permittivity and loss tangent enable us
to estimate the dc conductivity, dielectric strength, double layer capacitance,
and relaxation time. The loss tangent relaxation peak shifts towards
high-frequency side which indicates the decrease of relaxation time and faster
ion dynamics. Further, the relation among various relaxation times ...... has
been developed systematically. The ionic conductivity has been estimated in
whole frequency window including JPL and displays strong dependency on SN
content. The sigma representation ........ has been introduced for exploring
the ion dynamics by highlighting the dispersion region in Cole-Cole plot
(........) at lower frequency window and increase in the radius of semicircle
indicates a decrease of relaxation time. A well convincing/logical scheme has
been proposed which justify the recorded experimental data
Insights into the use of polyethylene oxide in energy storage/conversion devices: A critical review
In this review, latest updates in the poly (ethylene oxide) based
electrolytes are summarized. The ultimate goal of researchers globally is
towards the development of free standing solid polymeric separator for energy
storage devices. This single free standing solid polymeric separator may
replace the liquid and separator (organic/Inorganic) used in existing
efficient/smart energy technology. As an example polyethylene oxide (PEO)
consist of an electron donor rich group which provides coordinating sites to
the cation for migration. Owing to this exclusive structure PEO exhibits some
remarkable properties such as; low glass transition temperature, excellent
flexibility and ability to make complexation with various metal salts which are
unattainable by another polymer host. Hence, the PEO is the most emerging
candidate that have been examined or is currently under audition for
application in energy storage devices. So, this review article first provides
the detailed study of the PEO properties, characteristic of constituents of the
polymer electrolyte and suitable approaches for the modification of polymer
electrolytes. Then, the synthesization and characterizations techniques are
outlined. The structures, characteristics, and performance during
charge-discharge of four types of electrolyte/separators which are Liquid,
Plasticized, and dispersed/intercalated electrolyte are highlighted. The
suitable ion transport mechanism proposed by researchers in the different
renowned group have been discussed for better understanding of the ion dynamics
in such systems
Optimization of salt concentration and Explanation of Two Peak Percolation in Blend Solid Polymer Nanocomposite Films
The present paper report is focused toward the preparation of the flexible
and freestanding blend solid polymer electrolyte films based on PEO-PVP
complexed with NaPF6 by solution cast technique. The structural/morphological
features of the synthesized polymer nanocomposite films have been investigated
in detail using X-ray diffraction, Fourier transform infra-red spectroscopy,
field emission scanning electron microscope, and atomic force microscopy
techniques. The film PEO-PVP+NaPF6 O/Na:8 exhibits highest ionic conductivity
~5.92x10-6 S cm-1 at 40 oC and ~2.46x10-4 S cm-1 at 100 oC. The temperature
dependent conductivity shows Arrhenius type behavior and activation energy
decreases with the addition of salt. The high temperature (100 oC) conductivity
monitoring is done for the optimized PEO-PVP+NaPF6 O/Na:8 highly conductive
system and the conductivity is still maintained stable up to 160 h (approx. 7
days). The thermal transitions parameters were measured by the differential
scanning calorimetry (DSC) measurements. The prepared polymer electrolyte film
displays the smoother surface in addition of salt and a thermal stability up to
300 oC...........
Efficient Inference in Large Discrete Domains
In this paper we examine the problem of inference in Bayesian Networks with
discrete random variables that have very large or even unbounded domains. For
example, in a domain where we are trying to identify a person, we may have
variables that have as domains, the set of all names, the set of all postal
codes, or the set of all credit card numbers. We cannot just have big tables of
the conditional probabilities, but need compact representations. We provide an
inference algorithm, based on variable elimination, for belief networks
containing both large domain and normal discrete random variables. We use
intensional (i.e., in terms of procedures) and extensional (in terms of listing
the elements) representations of conditional probabilities and of the
intermediate factors.Comment: Appears in Proceedings of the Nineteenth Conference on Uncertainty in
Artificial Intelligence (UAI2003
Structural, Microstructural and Electrochemical Properties of Dispersed Type Polymer Nanocomposite Films
The free standing solid polymer nanocomposite films has been prepared through
standard solution cast technique. The improvement in structural,
microstructural and electrochemical properties has been observed on the
dispersion of nanofiller in polymer salt complex. X Ray diffraction studies
clearly reflect the formation of complex formation as no corresponding salt
peak appeared in the diffractograms. The FTIR analysis suggested a clear and
convincing evidence of polymer ion, ion ion and polymer ion nanofiller
interaction. The highest ionic conductivity of the prepared solid polymer
electrolyte films is 5x10-5 S cm-1 for 7 wt. TiO2. The Linear Sweep Voltammetry
provide the electrochemical stability window of the prepared solid polymer
electrolyte films, which is of the order of 3.5 V. The ion transference number
has been estimated, tion is 0.99 through dc polarization technique. Dielectric
spectroscopic studies were performed to understand the ion transport process in
polymer electrolytes. All solid polymer electrolyte possesses good thermal
stability up to 300C. DSC analysis confirms the decrease of melting temperature
and signal of glass transition temperature with addition of nanofiller which
indicates the decrease of crystallinity of polymer matrix. An absolute
correlation between diffusion coefficient, ion mobility, number density, double
layer capacitance, glass transition temperature, melting temperature, free ion
area and conductivity has been observed. A convincing model to study the role
of nanofiller in polymer salt complex has been proposed which supports the
experimental findings. The prepared polymer electrolyte system with significant
ionic conductivity, high ionic transference number, good thermal, voltage
stability could be suggested as a potential candidate as electrolyte cum
separator for fabrication of rechargeable lithium-ion battery system.Comment: arXiv admin note: text overlap with arXiv:1807.0353
On maximal area integral problem for analytic functions in the starlike family
For an analytic function defined on the unit disk , let
denote the area of the image of the subdisk under ,
where . In 1990, Yamashita conjectured that for convex functions and it was finally settled in 2013 by
Obradovi\'{c} and et. al.. In this paper, we consider a class of analytic
functions in the unit disk satisfying the subordination relation
for and
. We prove Yamashita's conjecture problem for functions in this
class, which solves a partial solution to an open problem posed by Ponnusamy
and Wirths.Comment: 12 pages, 8 figures, 2 tables, submitted to a journa
On a generalization of close-to-convex functions
A motivation comes from {\em M. Ismail and et al.: A generalization of
starlike functions, Complex Variables Theory Appl., 14 (1990), 77--84} to study
a generalization of close-to-convex functions by means of a -analog of a
difference operator acting on analytic functions in the unit disk
. We use the terminology {\em
-close-to-convex functions} for the -analog of close-to-convex functions.
The -theory has wide applications in special functions and quantum physics
which makes the study interesting and pertinent in this field. In this paper,
we obtain some interesting results concerning conditions on the coefficients of
power series of functions analytic in the unit disk which ensure that they
generate functions in the -close-to-convex family. As a result we find
certain dilogarithm functions that are contained in this family. Secondly, we
also study the famous Bieberbach conjecture problem on coefficients of analytic
-close-to-convex functions. This produces several power series of analytic
functions convergent to basic hypergeometric functions.Comment: 14 pages, to appear in a journal (this version of the paper may not
be the final version
Revisiting the entropic force between fluctuating biological membranes
The complex interplay between the various attractive and repulsive forces
that mediate between biological membranes governs an astounding array of
biological functions: cell adhesion, membrane fusion, self-assembly,
binding-unbinding transition among others. In this work, the entropic repulsive
force between membranes---which originates due to thermally excited
fluctuations---is critically reexamined both analytically and through
systematic Monte Carlo simulations. A recent work by Freund \cite {Freund13}
has questioned the validity of a well-accepted result derived by Helfrich
\cite{Helfrich78}. We find that, in agreement with Freund, for small
inter-membrane separations (), the entropic pressure scales as ,
in contrast to Helfrich's result: . For intermediate separations,
our calculations agree with that of Helfrich and finally, for large
inter-membrane separations, we observe an exponentially decaying behavior.Comment: accepted to Journal of Mechanics and Physics of Solid
Development of Novel Cathode Materials based on MWCNT for Energy Storage/Conversion Devices
Novel compound comprising of Li2FexMn(1-x)SiO4/MWCNT were prepared by using
Sol-Gel technique. In this study, improved electrochemical properties are
observed by substituting Fe to replace Mn. and further multiwalled carbon nano
tubes are used to prepare composite with prepared cathode material in Lithium
ion battery and electrode materials in super capacitors. Various
characterization techniques like: FESEM, EDX confirms the structure, morphology
and texture of the material. Average particle size is found to be of order of
20-30 nm. As particles with smaller size reveal better electrical
conductivity/electrochemical properties, which are confirmed by A.C Impedence
spectroscopy and cyclic voltammetery results
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