Ionic Conductivity

The polymer electrolytes comprising blend of poly(vinyl acetate) (PVAc) and poly(methylmethacrylate) (PMMA) as a host polymer and LiClO4 as a dopant are prepared by solution casting technique. The amorphous nature of the polymer–salt complex has been confirmed by XRD analysis. The DSC thermograms show two Tg's for PVAc–PMMA blend. A decrease in Tg with the LiClO4 content reveals the increase of segmental motion. Conductance spectra results are found to obey the Jonscher's power law and the maximum dc conductivity value is found to be 1.76 × 10− 3 S cm− 1 at 303 K for the blend polymer complex with 20 wt.% LiClO4, which is suitable for the Li rechargeable batteries. The conductivity–temperature plots are found to follow an Arrhenius nature. The dc conductivity is found to increase with increase of salt concentration in the blend polymer complexes.

Ceramic solid solutions Bi4MnxV2–xO11–(x/2)–δ in the composition range 0.07 ≤ x ≤ 0.30 were obtained by solid state synthesis. Structural investigations were carried out by using a combination of FT-IR and powder X-ray diffraction technique. Polymorphic transitions (β↔γ and γ′↔γ) were detected by DTA and variation in the Arrhenius plots of conductivity. The solid solutions with composition 0.07 ≤ x ≤ 0.17 are isostructural with the orthorhombic β-phase, and those with x ≤ 0.30 represent tetragonal γ-phase. With increasing Mn concentration, the conductivity of solid solutions increases from 3.684×10-6 (x = 0.07) to 2.467×10-5 (x = 0.17). AC impedance plots show that the conductivity is mainly due to the grain contribution which is evident in the enhanced short range diffusion of oxide ion vacancy in the grains with increasing temperature.

Gel Polymer Electrolytes (GPE) based on agar and containing LiClO4 have been prepared, characterized and applied to electrochromic devices. The ionic conductivity revealed the best result of 6.5 × 10−5 S/cm for the sample with 17 wt.% of LiClO4, which increased to 5.4 × 10−4 S/cm at 72°C. The GPE have been used in electrochromic devices (ECD) with K-glass/WO3/GPE/CeO2-TiO2/K-glass configuration. The ECD changed transmittance values up to 30% between the colored and transparent states. The charge density measurements revealed an increase of 5.5 to 7.5 mC/cm2 from the first to 500th cycles and then a decrease to 4.4 mC/cm2 during the next 4500 cycles. Coloration efficiency (η) of 25 cm2/C was obtained.

The perspective of hydrogen utilization as a clean fuel, mainly produced from renewable energy sources, compels the refinement of the water electrolysis process, thus reducing hydrogen generation costs. This paper presents the research now in progress at the Laboratório de Hidrogênio ...

New techniques for cleaning acrylic emulsion paint surfaces continue to emerge in the practice of contemporary conservation. The discipline is currently in the process of identifying problematic first-generation practices, pursuing improved and alternative treatments, and framing a dialogue to guide future innovations. This paper will present four case studies that illustrate a new aqueous cleaning system for acrylic paint films on paper supports. It will also address this system’s potential to treat discolored paper and board. Driving this evolution in practice is acrylic works’ sensitivity to aqueous cleaning methods. Paint film swelling and surfactant or pigment disruption are two primary risks conservators regularly face when cleaning acrylic works of art on paper. The aqueous cleaning system discussed in this paper mitigates these risks by using pH and conductivity meters to test acrylic paint surfaces and to create customized aqueous cleaning solutions—a technique demonstrated...

A conductivity relaxation experiment has been conducted on an SrFeCo0.5Ox sample by abruptly changing the oxygen partial pressure in the atmosphere and monitoring the change of conductivity as a function of time. The re-equilibrium process obeys Fick's second law. By fitting the relaxation data to the solution of the diffusion equation with appropriate boundary conditions, we could determine the oxygen chemical diffusion coefficient and the activation energy. The oxygen diffusion coefficient is 8.9 × 10−7 cm2/s at 900 °C and it increases with increase in temperature. Measured activation energy is 0.92 eV, which is slightly lower than that of other oxides in the system SrFe1 − xCoxOy.

The single-layered microporous polyethylene
separator is prepared by dry process and has been
stretched in uni-axial direction to two different ratios
namely 180 and 300 % in order to create highperformance
and cost-effective separator for practical application
in lithium-ion batteries. In this study, the structures
of the microporous polyethylene separator prepared
by dry process and uni-axially stretched to two different
ratios of 180 and 300 % were characterized. The physical
structure of the stretched separator is characterized by key
factors such as thickness, mean pore size, porosity, Gurley
value, ionic resistivity, MacMullin number and tortuosity.
The thermal behavior of the stretched separator is
explained by using differential scanning calorimeter
(DSC). DSC explains the melting and shutdown behavior
of the separator. Electrochemical property is studied by
linear sweep voltammetry, electrochemical impedance
spectroscopy (EIS) and cyclic performance. EIS is performed
to explain, in elaborate, the resistance of separator
and the specific discharge capacity is observed using the
cyclic performance. Three hundred percent stretched separator is observed to have comparatively less resistance
and higher discharge capacity than the 180 % stretched
separator.