Band 234, Heft 3

In this paper, the effect of the crystalline microstructures of polyvinylidene fluoride (PVDF), as cathode binder, on mechanical and electrochemical properties of the cathode, and on the cell performance is investigated. The crystalline phases of the PVDF films prepared at different temperatures are determined by X-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FT-IR) and also mechanical strength of PVDF films evaluated by a tensile test. The cathodes were prepared at altered temperatures to achieve different PVDF phases. The effect of various crystalline phases on the cathode performance was studied. The obtained cathodes were analyzed by scanning electron microscope (SEM), contact angle measurement, and adhesion test. The electrochemical performance of the cathodes was evaluated by charge-discharge cycling test and AC impedance spectroscopy. Mechanical tests results showed that the cathode which is prepared at 60 °C has the best adhesion and mechanical stability. In addition, the charge-discharge cycling studies showed that this cathode has the highest capacity efficiency. AC impedance spectroscopy illustrated that this electrode has the lowest charge transfer resistance and SEI resistance.

The paper reports the results of the measurement of surface tension in binary liquid mixtures containing choline chloride, ethylene glycol and water and ternary mixtures of ethaline (a eutectic mixture of ethylene glycol and choline chloride, the so-called deep eutectic solvent) with water. The surface tension is determined in a wide range of components’ concentration for the temperatures of 25, 30, 40, 50, 60 and 70 °C. The dependences of surface tension on the concentration of liquids are treated by means of Gibbs adsorption isotherm and linear form of Langmuir adsorption isotherms. The values of the equilibrium constant of adsorption at the interface liquid solution/air as well as the standard adsorption Gibbs energy, enthalpy and entropy are calculated for the binary and ternary mixtures under consideration. The obtained results are interpreted in the light of intermolecular interactions in fluids. Our findings show that ethylene glycol and choline cation interact with each other in the adsorbed surface layer formed at the interface between air and diluted solutions of ethaline.

Raman (3700–100 cm −1 ) and infrared (4000–400 cm −1 ) spectra of 2,5-Dimercapto-1,3,4-thiadiazol (DMTD) were recorded in the solid phase. Six structures ( 1 – 6 ) were initially proposed for DMTD as a result of thiol-thione tautomerism and internal rotation(s) of thiol group(s) around the C–S bond. Quantum chemical calculations were carried out for an isolated molecule ( 1 – 6 ) using density functional theory (B3LYP) and ab initio MP2(full) methods utilizing 6-31G(d) and 6-311++G(d,p) basis sets which favor thiol-thione tautomerism (structure 4 ). Relaxed potential energy surface scans of structure 4 revealed an additional conformer (the thiol group is out-of-plane, structure 7 ) using the aforementioned methods at 6-311++G(d,p) basis set. For additional verification, plane-wave solid state calculations were carried out at PW91 and PBEsol came out in favor of conformer 7 . This is in agreement with the computed/observed SH in-plane bending of S-7 (959/941 cm −1 ) rather than the one estimated at (880 cm −1 ) for S-4 . Moreover, the observed split IR/Raman bands were found consistent with solid state calculated frequencies of S-7 assuming two molecules per unit cell bonded via H-bonding intermolecular interactions. Aided by vibrational frequency calculations, normal coordinate analysis, force constants and potential energy distributions (PEDs), a complete vibrational assignment for the observed IR and Raman bands is proposed herein. Furthermore, we have estimated the frontier molecular orbitals and atomic charges to account for the corrosion inhibition efficiency of DMTD along with its binding sites to the metal surface. Our results are discussed herein and compared to similar molecules whenever appropriate.

Transition metals have unique efficacy in catalyzing various industrial reactions and also in living system, the redox reaction and redox changes in the metal ions catalyzed valence changes in the substrate molecule. The survey of the existing literature revealed that the binding of Molybdenum, Vanadium, Zinc, Cadmium, Copper, Nickel and Cobalt with the protein is well known but no binding studies of copper metal with egg protein are reported. With a view to extend the existing knowledge of ecological nature of metal-protein system, it was thought of interest to investigate the properties of metal-protein mixture. Investigations on the aspects of these binding problems were planned and their bindings constants have been determined using suitable physico-chemical methods. The pH metric, diffusion current measurements, spectrophotometric methods have been used on the binding of copper ions with albumin. The effect of physico-chemical factors on interaction between divalent metal ion i.e. copper with albumin has been discussed. On the basis of observed results, it is found that the binding data were dependent on pH and temperature. From scatchard plots, the intrinsic association constants (k) and the number of binding sites (n) were calculated and found high at lower pH and temperatures. Therefore, a lower temperature and lower pH offered more sites in the protein molecule for interaction with copper (II) ions. The enthalpy (ΔH), entropy (ΔS) changes, free energy change (ΔG°) have been calculated.

The activated carbon was made of carbonized chest nut shell (CCS) and used as low cost adsorbent for 2,4-D (2,4-dichlorophenoxyacetic acid) removal. The experiments were conducted at different temperatures such as 35, 45 and 55 °C and this system represents as L type adsorption behavior. The experimental data were modelled using several isotherm models such as Langmuir, Freundlich, Temkin and Dubinin Radushkevich. The adsorption dynamics were searched by applying pseudo first, pseudo second and intra particle diffusion models. The thermodynamic approach was conducted for determining the thermodynamic values of ΔH°, ΔS° and ΔG°.

The use of indigenous natural materials and their modification toward fruitful application is one of the important subjects. Thermal modification of Rice Husk at 400 o C resulted into Rice Husk Char (RHC) which was chemically modified with KOH and was labeled as KOH Modified Rice Husk Char (KMRHC). Both RHC and KMRHC were characterized by using, Fourier transformed infrared (FTIR), scanning electron microscopy (SEM), energy dispersive X-rays (EDX) and X-ray diffraction (XRD) before and after their use as adsorbents. The prepared material was applied for the removal of toxic dyes, Direct Blue (DB) and Titan Yellow (TY) from aqueous media. The maximum adsorption capacity of DB and TY dyes on KMRHC were inspected as 30.9 mg/g and 28.6 mg/g, respectively at pH 4 using initial dye concentrations of 80 mg/L containing 2500 mg/L of the adsorbent dose with agitation speed of 240 rpm at 303 K. At the same experimental conditions the highest percentage removal of DB and TY on the adsorbent were observed as 96.6% and 89.3%, respectively. Thermodynamics studies of the adsorption of DB and TY dyes on KMRHC inferred for exothermic and spontaneous process. The value of ΔS is negative which suggested that randomness decreases at the interface of adsorbent-adsorbate during the adsorption. The kinetics study indicated that the experimental data of the adsorption process for both dyes, best fits to pseudo-second order kinetic model. The equilibrium data was tested on Langmuir, Freundlich and Temkin adsorption isotherm models. It was observed that the data are best fit to the Langmuir isotherm model (R 2 > 0.99), which suggested that the adsorption process is dominated by chemisorption approach. The overall results suggest that various parameters of the adsorption process were not only affected by the variation in experimental conditions but also by the chemical structure of the adsorbate molecules for the same adsorbent.

The 50 nm thickness Zn-doped polyvinyl alcohol (PVA) was deposited on n -4H-SiC semiconductor as interlayer by electro-spinning method and so Au/Zn-doped PVA/ n -4H-SiC metal-polymer-semiconductor (MPS) structure were fabricated. The real and imaginary parts of the complex dielectric constant ( ε ′, ε ′′), loss-tangent (tan δ ), the real and imaginary parts of the complex electric modulus ( M′ , M′′ ) and ac electrical conductivity ( σ ac ) behavior of this structure were examined using impedance spectroscopy method in a wide range of frequency (1 kHz–400 kHz) and voltage (−1 V)–(+6 V) at room temperature. The values of ε ′, ε ′′, tan δ , M′ , M′′ and σ ac are determined sensitive to the frequency and voltage in depletion and accumulation regions. The values of ε ′ and ε ′′ decrease with increasing frequency while the values of M′ and σ ac increase. The peak behavior in the tan δ and M′′ vs. frequency curves was attributed to the dielectric relaxation processes and surface states ( N ss ). The plots of ln ( σ ac ) vs. ln ( f ) at enough high forward bias voltage (+6 V) have three linear regions with different slopes which correspond to low, intermediate and high frequencies, respectively. The dc conductivity is effective at low frequencies whereas the ac conductivity effective at high frequencies. According to experimental results, the surface/dipole polarizations can occur more easily occur at low frequencies and the majority of N ss between Zn-doped PVA and n -4H-SiC contributes to the deviation of dielectric behavior of this structure.

The solvent finding step has always been a time-consuming job in chemical-involved processes. The source of difficulty mainly comes from the trial-and-errors, as a repetitive process of chosing solvents and mixing them in different proportions. Computers are good at doing repetitive processes; however, they can only deal with numerical values, rather than qulitative scales. Numerification of qualitative parameters (like solubility) has already been introduced. The most recent one is the Hansen solubility parameters (HSPs). Using the HSPs could provide a solvent or solvent-mixture. In our previous study, we introduced a computer-aided model and a software to find a solvent mixture. In this study, we have used the computer-aided solvent selection model to find some solvent mixtures for polyamide 11, a biobased polymer which has attracted enormous attention recently. Using this numerical model significantly diminished the time of solvent development experimentation by decreasing the possible/necessary trials.

In this work, green synthesis of silver nanoparticles is described by phytochemical reducing silver nitrate aqueous solution using Anthemis nobilis. For this purpose, Anthemis nobilis extract was used for the synthesis of silver nanoparticles as both surfactant and reducing agent. Green synthesis method is a good alternative to physical and chemical methods, since it is fast, simple, environmentally-friendly and economic. The produced nanoparticles are identified using FE-SEM, EDX, and FT-IR and Uv/Vis techniques. Formation of silver nanoparticles is verified in 430–420 nm range. Reduction of silver ions by hydroxyl functional group is also confirmed by FT-IR device. EDX device confirms the presence of a peak for Ag element without any impurity peak. Silver nanoparticles are identified by FE-SEM device and found to have average size between 17 and 42 nm. Also, the antibacterial activity of the synthesized nanoparticles is compared with that of staphyloccusaureus and pseudomonasa aeruginosa and the maximum inhibitory activity against the bacteria is obtained using 1 mM nitrate solution.