Smart Polymeric Cathode Material with Intrinsic Overcharge Protection Based on a 2,5‐Di‐tert‐butyl‐ 1,4‐dimethoxybenzene Core Structure

Polymer‐based electroactive materials have been studied and applied in energy storage systems as a valid replacement for transition metal oxides. As early as 1999, Hass et al. proposed an interesting concept on the possible incorporation of both charge storage and overcharge protection functionality into a single material. However, there are virtually no examples of polymeric materials that can not only store the charge, but also consume the overcharge current. Herein, a new material based on a cross‐linked polymer ( I ) with 2,5‐di‐tert‐butyl‐1,4‐dimethoxybenzene as the core structure is reported. The cyclic voltammogram of the synthesized polymer shows a single oxidation/reduction peak at 3.9–4.0 V. At 1C rate (56 mA/g), polymer I shows stable cycling up to 200 cycles with <10% capacity loss. The redox shuttle mechanism remarkably can be activated when cell voltage is elevated to 4.3 V and the overcharge plateau at 4.2 V (2^nd plateau) is persistent for more than 100 hours. The overcharge protection was due to the release of a chemical redox shuttle species in the electrolyte during the initial charging process. Both DFT calculations and NMR analysis of the aromatic signals in the ¹H‐NMR spectrum of electrolytes from “overcharged” cells provide evidence for this hypothesis.     

Optimized Dispersive Liquid–Liquid Microextraction and Determination of Sorbic Acid and Benzoic Acid in Beverage Samples by Gas Chromatography

A new rapid method for direct determination of trace levels of sorbic and benzoic acids was developed by dispersive liquid–liquid microextraction and gas chromatography with flame ionization detection. In the proposed approach, the separation procedure of sorbic and benzoic acids was performed on a general chromatographic column without any prior derivatization processes. Some effective parameters on the microextraction recovery were studied and optimized utilizing multilevel factorial and central composite experimental designs. The best concurrent extraction efficiency acquired using ethanol and chloroform as dispersive and extraction solvents. Central composite design (CCD) resulted in the optimized values of microextraction parameters as follows: 1.0 mL of dispersive and 0.1 mL of extraction solvents, ionic salt concentration of 50 g?L^?1 at pH 4. Under optimum conditions, the calibration curve was linear over the range 0.5–20 mg L^?1. Relative standard deviation was 11% and 13% for five repeated determinations for sorbic and benzoic acids, respectively. Limits of detection were acquired as 0.2 mg L^?1 for sorbic acid and 0.5 mg L^?1 for benzoic acid. The average recoveries were 31% and 39% for sorbic and benzoic acids, respectively. The method was successfully applied to the determination of sorbic and benzoic acids as preservatives in beverage samples.     

Development of a silver ion source using nanosecond pulses of a Nd:YAG laser at different wavelengths

A silver ion source was designed by focusing the fundamental and harmonics of Q-switched Nd:YAG laser pulses onto a silver target and simultaneously applying an electric potential in an argon environment. The silver ions were detected at a distance of 2 cm from the target surface using a Faraday cup ion probe after letting them pass through a retarding mesh grid (copper electrode). We aim to produce and characterize the silver ions generated by the laser radiation of different wavelengths and pulse energy, ambient gas pressure and the electrode spacing under applied electric field. In addition to this, the effect of laser radiation on plasma under vacuum and at different argon gas pressures was investigated. The velocity distribution function of the plasma emitted from the silver target was investigated under argon discharge. These measurements demonstrated clearly that the velocity distribution function and current signals depend on laser power, laser wavelength and argon pressure. We observed a ten fold increase in the plume current with increase in the applied voltage and ion velocity in the presence of a laser field. The surface morphology of the laser irradiated samples was investigated using reflection optical microscopy.     

The use of Jacobi polynomials in the numerical solution of coupled system of fractional differential equations

In this paper, we study shifted Jacobi polynomials and develop a simple but highly accurate scheme for the numerical solution of coupled system of fractional differential equations. We derive some operational matrices of integration and differentiation of fractional order. By the application of these matrices we provide a theoretical treatment to approximate the solutions of the corresponding system. We use Matlab to perform necessary operations. The applicability of the technique is shown with some examples and the results are displayed graphically.     

Agro‐wastes: Mechanical and physical properties of resin impregnated oil palm trunk core lumber

Agro‐wastes, oil palm trunk core or sap was utilized for the production of new palm‐wood material using phenol formaldehyde resin as a matrix. The kiln‐dried (moisture content 10%) oil palm trunk was impregnated with phenol formaldehyde resin using a high power vacuum pump. The oil palm trunk core lumber (OPTCL) was loaded with different percentages of phenol formaldehyde (PF) resin. The mechanical properties (tensile, flexural, and impact) and physical properties (water absorption and density) were studied and compared with rubberwood. Testing of mechanical and physical properties was done according to the ASTM standard. The morphology of the resin loaded OPTCL was analyzed by using Scanning Electron Microscopy (SEM). In general, the result showed that impregnated OPTCL exhibited good mechanical and physical properties when compared with untreated oil palm trunk core (OPTCL with 0% resin content) and rubberwood. Tensile and flexural strength of OPTCL increased with the increase in the resin content up to 15% and showed a decreasing trend with the increase in the loading percentage beyond 15%.The impact strength also increased with the increase in the resin content from 5% to 15%. However, impregnated OPTCL with 15% resin loading showed lower water absorption uptake as compared with the other composite materials and rubberwood. SEM micrograph confirmed that the resin was impregnated efficiently within the pores of OPTCL fibers. POLYM. COMPOS., 2010. © 2009 Society of Plastics Engineers     

Polyimide molecular composites containing a stiff‐chain polymer derived from 1,5‐diaminonaphathalene and pyromellitic dianhydride

Polyimide molecular composite (MC) films were prepared by embedding a stiff‐chain polyimide (PI_S) in the ductile matrix of a flexible‐chain polyimide (PI_F) by blending their respective poly(amic acid) precursor solutions, followed by casting, drying, and thermal imidization upto 300°C. The PI_S was prepared from pyromellitic dianhydride (PMDA) and 1,5‐diaminonaphathalene (DAN), whereas the PI_F was prepared from the same dianhydride and 4,4′‐oxydianiline (ODA). Transparent, tough, and creasable MC films were obtained with 2.5–40 wt% of PI_S content. The disruption of crystalline order of PI_S in the MC films evidenced its fine dispersion in the matrix. Visco‐elastic measurements showed a single and enhanced value of the glass transition temperature for MC films indicating miscibility of this polyimide pair. Furthermore, the variation of charge transfer (CT) fluorescence intensity with the PI_S content in the blends verified complete miscibility upto 30 wt% of PI_S loading. These MCs showed a notable enhancement in the mechanical properties. Among all, the blend containing 30 wt% of stiff‐chain molecules gave the best combination of properties when compared with the matrix polyimide: a 50% higher value of tensile modulus, a 17°C rise in the glass transition temperature, and better thermal stability. POLYM. COMPOS., 2010. © 2009 Society of Plastics Engineers     

Dihydroxyaluminum Carboxylate Nanoparticles With Narrow Size Distribution: Synthesis,Characterization and Use for High Optical Transparency Protective Polymeric Coatings

Nano‐sized bis(dihydroxyaluminum)maleate particles (ALMAL) were prepared via a high‐temperature precipitation reaction from different Al‐alkoxides and maleic acid in different solvents. Variations in the reactants were carried out to identify the optimum reaction conditions that lead to particles <30 nm in diameter with narrow particle size distributions and without formation of a secondary amorphous phase. A disc centrifuge was used to characterize the particles in terms of particle size distribution. ALMAL‐containing, epoxy‐based nanocomposites were prepared with ALMAL‐loadings up to 30 wt.‐% and thermally cured. The cured coatings possessed excellent scratch and abrasion resistance, surface hardness and were highly transparent (T>95%). In order to study the effect of the nature of nanoparticles on the final properties of the coatings, aluminum malate (ALMALAT), and aluminum terephthalate (ALTEREPHTHAL) nanoparticles as well as the corresponding composite coatings were prepared and characterized. For comparison, surface‐modified silica nanoparticles were used to evaluate the mechanical and optical behavior of the produced nanocomposite coatings.

     

Preparation,Infra-red,MAS-NMR and Structural Characterization of a New Copper Based Inorganic–Organic Hybrid Compound: [C<Subscript>5</Subscript>H<Subscript>6</Subscript>N<Subscript>2</Subscript>Cl]<Subscript>2</Subscript>CuCl<Subscript>4</Subscript>

The ionic salt [2(C₅H₆N₂Cl)⁺], [CuCl₄]^2? complex of copper(II) has been synthesized and characterized. The X-ray diffraction analysis with a single crystal of this compound showed that the title compound (4-amino-2-chloropyridinium)₂CuCl₄ [(CAP)₂CuCl₄], crystallized at room temperature in the monoclinic system, space group C_2/c (N°.15) and the following : a = 16.0064 (2) Å; b = 7.7964 (10) Å; c = 14.7240 (2) Å; β = 102.497 (10)°; V = 1793.91 (4) ų and Z = 4. The structure was solved by using 1,589 independent reflections down to R value of 0.021. The unit cell is made up of tetrachlorocuprate(II) anions and 4-amino-2-chloropyridinium cations linked together by an extensive hydrogen bond network of types N–H···Cl (N: pyridinium) and N–H···Cl (N: amine), and cation-lone pair of nitrogen element interactions. Solid state NMR spectra showed one and five isotropic resonances, ⁶³Cu and ¹³C, respectively, confirming the solid state structure determined by X-ray diffraction. Impedance spectroscopy study, reported for single crystal, revealed that the conduction in the material was due to a hopping process. This work aims to reveal the thermal properties of a new copper(II) based organic–inorganic hybrid and the conductivity properties that these compounds exhibit.