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1.
A series of polymer nanocomposite films based on intercalation of (PAN)8LiCF3SO3 into the nanometric clay channels of an organomodified clay has been prepared using the standard solution-casting technique.
The role of organoclay concentration on polymer–ion interaction, ion–ion interaction, and ion–clay interaction in clay-based
nanocomposite films has been analyzed using Fourier transform infrared (FTIR) analysis. Substantial ion dissociation is observed
even at a very low clay loading (1–2 wt.%) in the nanocomposites. FTIR results suggest the presence of both uncoordinated
CF3SO3
− (free-anions) and ion pairs in the nanocomposite evidenced by changes in CF3SO3
− symmetry from C3ν to Cs and marked asymmetry in the profile of degenerate δd(CF3
−) mode. The experimental results suggest a direct correlation of clay-assisted ion dissociation process with variation in
conductivity (σ
dc) and glass transition temperature (T
g) as a function of clay concentration. A model has been proposed to explain the observed correlation on the basis of polymer–ion–clay
interaction. The proposed scheme of ion transport mechanism appears to be consistent with the experimental observation. 相似文献
2.
Thin films of ZnSe and PEO–chitosan blend polymer doped with NH4I and iodine crystals were prepared to form the two sides of a semiconductor electrolyte junction. ZnSe was electrodeposited
on indium tin oxide (ITO) conducting glass. The polymer is a blend of 50 wt% chitosan and 50 wt% polyethylene oxide. The polymer
blend was complexed with ammonium iodide (NH4I), and some iodine crystals were added to the polymer–NH4I solution to provide the I−/I3−redox couple. The room temperature ionic conductivity of the polymer electrolyte is 4.32 × 10−6 S/cm. The polymer film was sandwiched between the ZnSe semiconductor and an ITO glass to form a ZnSe/polymer electrolyte/ITO
photovoltaic cell. The open circuit voltage (V
oc) of the fabricated cells ranges between 200 to 400 mV and the short circuit current between 7 to 10 μA. 相似文献
3.
In the present paper, the ionic conductivity and the dielectric relaxation properties on the poly(vinyl alcohol)-CF3COONH4 polymer system have been investigated by means of impedance spectroscopy measurements over wide ranges of frequencies and
temperatures. The electrolyte samples were prepared by solution casting technique. The temperature dependence of the sample’s
conductivity was modeled by Arrhenius and Vogel-Tammann-Fulcher (VTF) equations. The highest conductivity of the electrolyte
of 3.41×10 − 3 (Ωcm) − 1 was obtained at 423 K. For these polymer system two relaxation processes are revealed in the frequency range and temperature
interval of the measurements. One is the glass transition relaxation (α-relaxation) of the amorphous region at about 353 K and the other is the relaxation associated with the crystalline region
at about 423 K. Dielectric relaxation has been studied using the complex electric modulus formalism. It has been observed
that the conductivity relaxation in this polymer system is highly non-exponential. From the electric modulus formalism, it
is concluded that the electrical relaxation mechanism is independent of temperature for the two relaxation processes, but
is dependent on composition. 相似文献
4.
K. Fukao Y. Oda K. Nakamura D. Tahara 《The European physical journal. Special topics》2010,189(1):165-171
The glass transition temperature and the dynamics of the α-process have been investigated using dielectric relaxation spectroscopy
for single and stacked thin films of poly(2-chlorostyrene) (P2CS). The stacked film consists of 10 layers of single thin films
with thickness of 12 nm or 18 nm. The glass transition temperature T
g
of the single thin films of P2CS is found to decrease with decreasing film thickness in a similar way as observed for polystyrene
thin films. The magnitude of the depression of T
g
for the stacked thin films is larger than that of the single thin films with corresponding thickness. The depression of the
temperature at which the dielectric loss shows a peak due to the α-process at a given frequency, T
α, is larger than that of the single thin films, although the magnitude is smaller than that of T
g
. Annealing at a high temperature could cause the T
g
and T
α of the stacked thin films to approach the values of the bulk system. 相似文献
5.
Hellar Nithya S. Selvasekarapandian P. Christopher Selvin Dorai Arun Kumar Muthusamy Hema 《Ionics》2011,17(7):587-593
The plasticized polymer electrolyte consisting of poly(epichlorohydrin-ethyleneoxide) [P(ECH-EO)], lithium perchlorate (LiClO4) and γ-butyrolactone (γ-BL) have been prepared by simple solution casting technique. The polymer–salt–plasticizer complex
has been confirmed by XRD analysis. The ionic conductivity studies have been carried out using AC impedance technique. The
effect of plasticizer (γ-BL) on ionic conductivity has been discussed with respect to different temperatures. The maximum
value of ionic conductivity is found to be 1.3 × 10−4 Scm−1 for 70P(ECH-EO):15γ-BL:15LiClO4 at 303 K. The temperature dependence of the plasticized polymer electrolyte follows the Vogel–Tamman–Fulcher formalism. The
activation energy is found to decrease with the increase in plasticizer. 相似文献
6.
Solvent-free films of poly (ethylene oxide)–silver triflate (PEO–AgCF3SO3)/MgO-based nanocomposite polymer electrolytes (PEO)50AgCF3SO3–x wt.% MgO (x = 1, 3, 5, 7, and 10) obtained using solution casting technique were found to exhibit an appreciably good complexation of
MgO nanofiller within the polymer electrolyte system and non-Debye type of relaxation as revealed by Fourier transform infrared
and complex impedance analyses. Optimized filler (5 wt.% MgO) when incorporated into the polymer electrolyte resulted in a
maximum electrical conductivity of 2 × 10−6 S cm−1 in conjunction with a silver ionic transference number (t
Ag+) of 0.23 at room temperature (298 K). Detailed structural, thermal, and surface morphological investigation indicated a slight
reduction in the degree of crystallinity owing to the addition of MgO nanofiller. 相似文献
7.
A sodium ion conducting composite polymer electrolyte (CPE) prepared by solution-caste technique by dispersion of an electrochemically
inert ceramic filler (SnO2) in the PEO–salt complex matrix is reported. The effect of filler concentration on morphological, electrical, electrochemical,
and mechanical stability of the CPE films has been investigated and analyzed. Composite nature of the films has been confirmed
from X-ray diffraction and scanning electron microscopy patterns. Room temperature d.c. conductivity observed as a function
of filler concentration indicates an enhancement (maximum) at 1–2 wt% filler concentration followed by another maximum at
∼10 wt% SnO2. This two-maxima feature of electrical conductivity as a function of filler concentration remains unaltered in the CPE films
even at 100 °C (i.e., after crystalline melting), suggesting an active role of the filler particles in governing electrical
transport. Substantial enhancement in the voltage stability and mechanical properties of the CPE films has been noticed on
filler dispersion. The composite polymer films have been observed to be predominantly ionic in nature with t
ion ∼ 0.99 for 1–2 wt% SnO2. However, this value gets lowered on increasing addition of SnO2 with t
ion ∼ 0.90 for 25 wt% SnO2. A calculation of ionic and electronic conductivity for 25 wt% of SnO2 film works out to be ∼2.34 × 10−6 and 2.6 × 10−7 S/cm, respectively. 相似文献
8.
Thermally stimulated depolarization current studies of sulfonated polystyrene ionomers 总被引:1,自引:0,他引:1
Antonio José Felix Carvalho Vicente Galber Freitas Viana Roberto Mendon?a Faria 《Applied Physics A: Materials Science & Processing》2009,97(4):947-953
A detailed study of thermally stimulated depolarization current (TSDC) was carried out to investigate dipolar relaxation and
the charge storage phenomenon in films of sulfonated polystyrene (SPS) ionomers having lithium or potassium as counterions.
Differential scanning calorimetry measurements were also applied as a complementary technique, mainly to follow the change
of the glass transition temperature with the amount of sulfonated groups. It was observed that, since the glass transition
does not change significantly with the amount of sulfonated groups, a cluster of multiplets is expected not to be formed in
the range used in this work. TSDC of SPS samples polarized at temperatures higher than the glass transition temperature showed
three peaks: one at lower temperature (peak β), an intermediate peak (peak α), and a third that appeared at a temperature coincident with the polarization temperature (peak ρ). Quantitative information about trapping–detrapping and dipolar relaxation and their corresponding activation energies was
determined by fittings of the deconvoluted peaks with kinetic relaxation processes. 相似文献
9.
Amal Al-Kahlout Diogo Vieira César O. Avellaneda Edson R. Leite Michel A. Aegerter Agnieszka Pawlicka 《Ionics》2010,16(1):13-19
Proton-conducting gel polymer electrolytes based on gelatin plasticized with glycerol and containing acetic acid were investigated,
characterized, and applied to electrochromic window. For glycerol contents varying from 7% to 48%, the conductivity of the
uniform and predominantly amorphous gel electrolyte was found to follow a Vogel–Tamman–Fulcher behavior with the temperature.
Typically, for the electrolyte chosen to make 7 × 2 cm2 electrochromic smart window with the configuration: glass/fluor-doped tin oxide (FTO)/WO3/gelatin electrolyte/CeO2–TiO2/FTO/glass and containing 28% of glycerol, the conductivities were found to be of the order of 5 × 10−5 S/cm at room temperature and 3.6 × 10−4 S/cm at 80 °C. The device was characterized by spectroelectrochemical techniques and was tested up to 10,000 cycles showing
a fast coloring/bleaching behavior, where the coloring process was achieved in 10 s and the bleaching in 2 s. The transmission
variation at the wavelength of 550 nm was about 15%. The cyclic voltammograms showed a very good reversibility of the cathodic/anodic
processes, and the charge density was about 3.5 mC/cm2. The memory tests showed that the transmittance in the colored state increased by 8% in 90 min after removing the potential. 相似文献
10.
Dillip K. Pradhan R. N. P. Choudhary B. K. Samantaray Awalendra K. Thakur R. S. Katiyar 《Ionics》2009,15(3):345-352
Polymer–clay nanocomposites consisting of polymer (polyethylene oxide) and NaI as salt with different concentration of organically
modified Na+-montmorillonite (DMMT) have been fabricated and characterized. X-ray diffraction analysis shows that the polymer–salt complexes
have been intercalated into the nanometric silicate layers of DMMT. Fourier transform infrared analysis shows that the polymer
structure in the clay interlayer is similar to that of the polymer–salt complexes, and there is a strong interaction between
the polymer–salt complexes and clay layers. A study of surface morphology using scanning electron microscopy reveals that
microstructure of composites is affected by clay addition. Complex impedance analysis was used to calculate the bulk resistance
of the composites. An enhancement in the conductivity of about one order of magnitude has been observed on 5% clay addition
compared to that of the polymer–salt complexes, and it decreases monotonically for higher clay concentration. The effect of
clay concentration on the structural and physical properties of polymer nanocomposites is well correlated. 相似文献
11.
The crystallization and glass transition kinetics using differential scanning calorimetry (DSC) in 50AgI–33.33Ag2O–16.67[(V2O5)1−x
–(MoO3)
x
] superionic glassy system is discussed. Thermal stability of glass, studied using various criteria, does not vary significantly
with glass former variation. However, the activation energies for structural relaxation (E
s) at glass transition temperature and crystallization (E
c) obtained using Moynihan and Kissinger, Matusita-Sakka formulations found to exhibit interesting trends with MoO3 substitution in the glass matrix. It is noticed that the electrical conductivity (σ)–temperature (T) cycles obtained at a typical heating rate of 1 °C/min do exhibit significant thermal events. The conductivity after first
heating cycle at room temperature is found to be increasing with MoO3 content and maximum for x = 0.3 (~10−3 Ω−1 cm−1 at 30 °C) which is comparable to that of the host 50AgI–33.33Ag2O–16.67V2O5 glassy system. The parameters obtained from σ–T plots and DSC scans do complement each other in a particular range of composition. 相似文献
12.
Determination of the optimal parameters for the fabrication of ZnO thin films prepared by spray pyrolysis method 总被引:1,自引:0,他引:1
In this work, ZnO thin films have been prepared by spray pyrolysis deposition method on the glass substrates. The effect of
deposition parameters, such as deposition rate, substrate temperature and solution volume has been studied by X-ray diffraction
(XRD) method, UV–Vis–NIR spectroscopy, scanning electron microscopy (SEM), and electrical measurements. The XRD patterns indicate
polycrystalline wurtzite structure with preferred direction along (0 0 2) planes. Thin films have transparency around 90%
in the visible range. The optical band gap was determined at 3.27 eV which did not change significantly. Evolution of electrical
results containing the carriers’ density, sheet resistance and resistivity are in agreement with structural results. All the
results suggest the best deposition parameters are: deposition rate, R = 3 ml/min, substrate temperature, T
s = 450°C and thickness of the thin films t = 110–130 nm. 相似文献
13.
Hartmann L Gorbatschow W Hauwede J Kremer F 《The European physical journal. E, Soft matter》2002,8(2):145-154
The molecular dynamics in thin films (18 nm-137 nm) of isotactic poly(methyl methacrylate) (i-PMMA) of two molecular weights
embedded between aluminium electrodes are measured by means of dielectric spectroscopy in the frequency range from 50 mHz
to 10 MHz at temperatures between 273 K and 392 K. The observed dynamics is characterized by two relaxation processes: the
dynamic glass transition (α-relaxation) and a (local) secondary β-relaxation. While the latter does not depend on the dimensions
of the sample, the dynamic glass transition becomes faster (≤2 decades) with decreasing film thickness. This results in a
shift of the glass transition temperature T
g to lower values compared to the bulk. With decreasing film thickness a broadening of the relaxation time distribution and
a decrease of the dielectric strength is observed for the α-relaxation. This enables to deduce a model based on immobilized
boundary layers and on a region displaying a dynamics faster than in the bulk. Additionally, T
g was determined by temperature-dependent ellipsometric measurements of the thickness of films prepared on silica. These measurements
yield a gradual increase of T
g with decreasing film thickness. The findings concerning the different thickness dependences of T
g are explained by changes of the interaction between the polymer and the substrates. A quantitative analysis of the T
g shifts incorporates recently developed models to describe the glass transition in thin polymer films.
Received 12 August 2001 and Received in final form 16 November 2001 相似文献
14.
We present a comprehensive study of gold nanoparticle embedding into polystyrene (PS) surfaces at temperatures ranging from
T
g
+ 8 K to T
g
− 83 K and times as long as 105 minutes. This range in times and temperatures allows the first concurrent observation of and differentiation between surface
and bulk behavior in the 20nm region nearest the free surface of the polymer film. Of particular importance is the temperature
region near the bulk glass transition temperature where both surface and bulk processes can be measured. The results indicate
that for the case of PS, enhanced surface mobility only exists at temperatures near or below the bulk T
g
value. The surface relaxation times are only weakly temperature dependent and near T
g
, the enhanced mobility extends less than 10nm into the bulk of the film. The results suggest that both the concept of a “surface
glass transition” and the use of glass transition temperatures to measure local mobility near interfaces may not universally
apply to all polymers. The results can also be used to make a quantitative connection to molecular dynamics simulations of
polymer films and surfaces. 相似文献
15.
S. Guha D. Adil N. B. Ukah R. K. Gupta K. Ghosh 《Applied Physics A: Materials Science & Processing》2011,105(3):547-554
Matrix-assisted pulsed-laser evaporation (MAPLE) provides a mechanism for layer-by-layer growth to control the polymer–dielectric
interface in organic metal–insulator–semiconductor (MIS) diodes and field-effect transistors (FETs). MAPLE-deposited copolymers
of polyfluorene (PF) and polythiophene maintain their structural and optical properties, as determined by Raman spectroscopy,
absorption, and photoluminescence. These films are further utilized in MIS and FET structures with SiO2 and other polymer dielectrics. Since common polymer dielectrics prevent spin coating of solution processable polymers due
to solubility effects, MAPLE is one of the only deposition techniques for investigating all polymer semiconductor-insulator
interfaces. In this paper we present optical and electrical studies of MAPLE-deposited PF and polythiophene films in FETs
and MIS structures. The FET carrier mobilities of these devices compare well with spin-coated devices. Capacitance–voltage
and conductance–voltage from MIS structures with MAPLE-deposited PF copolymer films yield interface trap densities in the
low 1012 eV−1 cm−2 range. 相似文献
16.
M. M. Gafurov K. Sh. Rabadanov M. B. Ataev A. R. Aliev I. R. Ahmedov M. G. Kakagasanov S. P. Kraminin 《Journal of Applied Spectroscopy》2012,79(2):184-188
Raman and IR absorption spectra were studied and molecular relaxation characteristics of vibrations of the anion and solvent were calculated for an xLiNO3–(1 – x)(CH3)2SO2 system (x = 0.1, 0.2, 0.3, 0.4 M). It was found that it is impossible to increase the concentration of free ions involved in charge transfer in such a system by either increasing the temperature or changing the concentration composition in the studied range of x. 相似文献
17.
A new proton-conductive membrane (PCM) based on poly (vinyl alcohol) and ammonium sulfate (NH4)2SO4 complexed with sulfuric acid and plasticized with ethylene carbonate (EC) at different weight percent were prepared by casting
technique. The structural properties of these electrolyte films were examined by XRD studies. The XRD patterns of all the
prepared polymer electrolytes reveal the amorphous nature of the films. ac conductivity and dielectric spectra of the electrolyte
were studied with changing EC content from weight 0.00 to 0.75 g. A maximum conductivity of 7.3 × 10−5 S cm−1 has been achieved at ambient temperature for PCM containing 0.25 g of ethylene carbonate. The electrical conductivity σ, dielectric constant ε′ and dielectric loss ε″ of PCM in frequency range (100 Hz to 100 KHz), and temperature range (300–400 K) were carried out. Measurement of transference
number was carried out to investigate the nature of charge transport in these polymer electrolyte films using Wagner’s polarization
technique. Transport number data showed that the charge transport in these polymer electrolyte systems was predominantly due
to ions. The electrolyte with the highest electrical conductivity was used in the fabrication of a solid-state electrochemical
cell with the configuration (Mg/PCM/PbO2). Various cell parameters ldensity, and current density were determined. The fabricated cells gave capacity of 650 μAh and
have an internal resistance of 11.6 kΩ. 相似文献
18.
MG30 is natural rubber grafted with 30% poly(methyl methacrylate). Gel polymer electrolytes containing MG30–LiCF3SO3–X (X = propylene carbonate, ethylene carbonate) are prepared by solution casting technique. The polymer–salt complexes were investigated using Fourier-transformed infrared. The ionic conductivity of the electrolytes are determined by the ac impedance studies over the temperature range of 303–383 K and is observed to obey the Vogel–Tamman–Fulcher (VTF) rule. The Li+ transference number obtained using the Bruce and Vincent method is <0.3. The Li/Li+ interface stability is established and the electrolytes were found to be able to withstand a voltage of more than 4.2 V. 相似文献
19.
The dielectric properties of the ceramics of (1 − x)BiFeO3 − x(KBi)1/2TiO3 (0.40 < x < 0.85) solid solutions with an orthorhombic structure have been studied using impedance spectroscopy in the frequency range
25–106 Hz at different temperatures. It has been shown that these solid solutions undergo a diffuse ferroelectric phase transition.
The Curie temperature is found to be in the range 620–640 K. The activation energies of dielectric polarization relaxation
(δE
M
) and dc charge carriers (ΔE
dc) are determined. It has been established that, in the vicinity of 460 K, ΔE
dc increases jumpwise as the temperature increases. 相似文献
20.
H. Huth A. A. Minakov A. Serghei F. Kremer C. Schick 《The European physical journal. Special topics》2007,141(1):153-160
A differential AC-chip calorimeter capable to measure the
glass transition in nanometer thin films is described. Due to the
differential setup pJ/K sensitivity is achieved. Heat capacity can
be measured for sample masses below one nanogram even above room
temperature as needed for the study of the glass transition in
nanometer thin polymeric films. The calorimeter allows for the
frequency dependent measurement of complex heat capacity in the
frequency range from 1 Hz to 1 kHz. The glass transition in thin
films of polystyrene (PS) (100–4 nm) and polymethylmethacrylate
(PMMA) (400–10 nm) was determined at well defined experimental
time scales. No thickness dependency of the glass transition
temperature was observed within the error limits (±3 K) -
neither at constant frequency nor for the traces in the activation
diagrams (1 Hz–1 kHz). 相似文献