DC and AC Conductivity Study of Basalt Glasses Containing High Concentrations of Na+ Ions

Different glass samples prepared from Egyptian basalt with different Na₂O content according to the composition [(100-x) basalt + x Na₂O], where x = 10, 15, up to 35 mol%. The samples mixtures were melted at 1300 °C for 2 h. Each sample will be recognized from its sodium to basalt (S/B) ratio. The sample of 0.54 ratio exhibits a slight crystalline phase. As S/B ratio was increased, the density decreased gradually while the molar volume increased, and the pure amorphous nature was confirmed by comparing the experimental and the empirical density and molar volume values. The electrical conductivities, DC and AC, were found to increase as the (S/B) ratio was gradually increase up to 0.33, then the samples showed approximate stable value up to the sample of 0.54 ratio. While the activation energy showed gradual decrease up to 0.33 ratio, then it exhibits nearly a stable value. The activation energy values indicated that all the studied samples behave like semiconductors. It appeared also from the AC conductivity results that the relation of the s-factor with the sample temperature showed that the conduction mechanism of these samples obeys the correlated barrier hopping (CBH) model. The structure of the same samples was studied in our previous work by XRD, FTIR and Mössbauer spectrometer.

     

An approximate method for separated spectral analysis of connected buildings with added damping

The problem of determining maximum seismic responses, or spectral analysis, of connected adjacent structures is studied in this research. The goal of the study is twofold. First, determining when the dynamic coupling is important in such a problem and, second, establishing how to analyze each of the two structures separately when coupling is important. For tall buildings in many cases, the connecting link is intentionally accommodated with an added damping to suppress the lateral displacements. Therefore, effect of the localized damping is also accounted for in the analysis. Using essentials of modal analysis, a criterion is developed for estimation of the dynamic coupling of the two adjacent structures. Also, a procedure is developed for separated analysis of each structure incorporating the stiffness and inertial effects of the adjacent structures when coupling is important. The representative examples confirm good accuracy of the presented method.     

Chemical modification‐induced improvement in the electrical characteristics of radiation‐functionalized polypropylene sheets

The development of conducting or semiconducting polymers is a highly interesting area due to the urgent need for new materials that combine several unique properties to be applied in a great variety of electrochemical devices. Polypropylene sheets were functionalized by radiation‐induced grafting of acrylonitrile to import reactive nitrile groups into the inert polymer sheets. To improve the electrical characteristics, such as electrical conductivity, of the radiation‐grafted sheets, a conjugated structure was developed via the repetition of the two‐step condensation polymerization of p‐phenylenediamine and glyoxal using the grafted nitrile groups as starting point. The grafted and treated polypropylene sheets were characterized using Fourier transform infrared (FTIR) spectroscopy and thermogravimetric analysis (TGA). FTIR spectra confirmed the occurrence of the grafting as well as the treatment of the grafted cyanide groups with p‐phenylenediamine and reaction with glyoxal. TGA traces showed an improvement in the thermal stability of the grafted sheets by grafting and a reduction of such stability by chemical treatment. The electrical characteristics of the grafted and treated sheets were evaluated and compared with those of untreated polypropylene. The effects of degree of grafting and conjugated chain length on the electrical characteristics of the grafted sheets were also investigated. The results showed that the development of a conjugated chemical structure in the polypropylene sheets increases the conductivity by about five orders of magnitude. The electrical conductivity of polypropylene was significantly increased as a result of the chemical development of a conjugated double‐bond chain structure in the radiation‐functionalized form. Copyright © 2009 Society of Chemical Industry     

Digital holographic interferometry: Optomechanical properties of fibers

Studying polymer fiber's mechanical properties leads to an increased understanding of the behavior of polymeric structures. This will support the design of new synthetic fibers with improved properties. Thus, there is great interest in the exact knowledge of these properties. In this work, phase‐shifting digital holographic interferometry is used to investigate the variation of the optical properties of drawn polyvinylidene fluoride (PVDF) fiber. The study shows that the refractive index for light which is polarized in parallel direction to the fiber axis increases as the draw ratio increases. This implicates that the molecules become more oriented in this direction. However, the decrease in the values of the refractive index for light polarized perpendicular to the drawing direction reflects the reduced orientation of the molecules in this direction. This has been confirmed by studying the variation of the molecular orientation versus birefringence of the drawn PVDF fiber. Holograms and their relationship with the optomechanical parameters obtained are given for illustration. POLYM. ENG. SCI., 2011. © 2011 Society of Plastics Engineers     

Polymer complexes: LIX. Supramolecular structural,spectral and thermal analysis of N‐[2‐(6‐aminopyridino)] acrylamide polymer complexes

Novel ligand N‐[2‐(6‐aminopyridino)] acrylamide (APA) is prepared via amidation of 2,6‐diaminopyridine with acryloyl chloride in dry benzene as solvent. The ligand is characterized on the basis of elemental analysis, infra‐red (IR) analysis and ¹H nuclear magnetic resonance. Metal–polymer complexes are reported and characterized based on elemental analysis, molar conductance, magnetic susceptibility measurements, IR, ¹H nuclear magnetic resonance, electronic spectra and thermal analysis. The molar conductance of the polymer complexes in dimethylformamide corresponds to a 1:1/1:2 electrolyte, which is non‐electrolytic. IR spectra show that polyAPA is coordinated to the metal ions in a uni‐negatively bidentate manner with N, O donor sites of azomethine N and deprotonated enolic‐O. All the polymer complexes are of high spin type. On the basis of spectral studies an octahedral geometry may be assigned for Co(II) and Ni(II) polymer complexes. The thermal stabilities of the polymer complexes were studied and the activation energies of the degradation were calculated. Copyright © 2011 Society of Chemical Industry     

Using viscoelastic modeling and molecular dynamics based simulations to characterize polymer natural fiber composites

The potential for polymer natural fiber composites for manufacturing storage units for products with high ethanol content is explored. The influence of ethanol diffusion into the microstructure of the storage unit on its long-term mechanical (specifically creep compliance) and viscoelastic properties are measured. Burger's model for polymer viscoelasticity is used to predict durability and other fundamental properties of the composite based on the creep compliance trends. Properties such as the Maxwell moduli and Maxwell viscosities are then modeled as a function of net ethanol uptake and the concentration of natural fiber dispersed phase. Later, a combination of classical molecular dynamics (MD) and semi empirical modeling is used to predict the trends in ethanol diffusion coefficient as a function of temperature and natural fiber concentration. The most efficacious models for this purpose and the ways and means of further improving the simulation accuracy are discussed.     

Chromatographic separation of 65Zn from radioactive tellurium waste solution using alumina column

High-purity ⁶⁵Zn was separated from a mixture containing ^{121,121m,123m,127}Te, ⁶⁵Zn, ⁵⁴Mn, ⁶⁰Co, ^110m Ag, ¹²⁵Sb, and ¹³⁴Cs using a small chromatographic alumina column. Samples of aged radioactive tellurium waste were dissolved in alkali solutions (1 and 5 M NaOH) and fed into preconditioned 1.0 g alumina columns at ～50°C. The columns were washed with 1 M NaOH or successively with 5 and 1 M NaOH. ⁶⁵Zn was quantitatively retained in the alumina column in the course of feeding and washing the column with 1 M NaOH. Solutions of NH₄Cl-NH₃, NH₄Cl-HCl, and HCl were studied as eluents for ⁶⁵Zn from the alumina column. 2 M HCl ensured the highest elution yield (88.7 ± 1.7%) with the ⁶⁵Zn radionuclidic purity of 99.4 ± 0.02%.