Density and solubility of nafion: recast, annealed, and commercial films

The density of Nafion membranes wetted in water and acetonitrile and the solubility of Nafion in a 50:50 ethanol/water mixture are reported. Commercially available membranes, solution recast membranes, and recast membranes thermally processed for varying lengths of time were examined. Unheated recast membranes were found to be ～20% less dense in water than both commercial membranes and recast membranes heated at 140 °C for 40, 50, and 60 min. For heating times of ≥40 min, the density of recast membranes in water was invariant and equal to the density of commercial films. Similarly, in acetonitrile, commercial membranes and films heated for 1 h had the same density; unheated recast films were ～25% less dense. Nafion density in acetonitrile was ～15% less than that in water. Acid pretreatment reduced Nafion film density by ～15%. Unheated recast films were 22-100% soluble in a sonicated ethanol/water mixture. Commercial membranes and recast films heated for as little as 10 min were insoluble under the same conditions.     

Protective coatings – purpose,role, and design

Abstract

A wide range of coatings and coating processes is now available for protecting components in gas turbines operating in a variety of conditions. Coated aerofoils are less likely to fragment, and they keep their original shape – and hence their aerodynamic efficiency – for longer. Aluminide diffusion coatings perform well in relatively clean environments, especially on alloy bases which have a moderate resistance to the many forms of hot corrosion, and with additions of chromium or platinum they provide resistance to sulphate–induced hot corrosion. In hotter or more aggressive corrosive environments, overlay coatings based on MCrAlY (M = Fe,Co, Ni), CoCr, and MCrSi(Al), applied by electron beam evaporation or plasma spraying, are suitable for a wide variety of applications. It is not yet possible to design coatings from first principles for particular applications. Development still proceeds by repeated selection and testing, but modern technology has made this approach more effective than it was in the 1960s. The future is likely to see the rate of progress slow down; advances are expected to take the form of more efficient and flexible processes rather than a broadening of the range of applications.

MST/280     

Dilute Solution Behavior of Dendrimers and Polysaccharides: SEC, ESI-MS, and Computer Modeling

Dendrimers, the most highly branched structures achievable, have found numerous uses in the chemical, biological, and pharmaceutical fields. We have employed size exclusion chromatography (SEC) with universal calibration to determine molecular weight averages, distributions, intrinsic viscosities, and structural parameters of Starburst dendrimers, dextrans, and the starch degradation polysaccharides known as maltodextrins. Comparisons have been made in the dilute solution behavior of dendrimers and polysaccharides with equivalent weight-average molecular weights. Intrinsic viscosities decreased in the order [η](dextran) > [η](dextrin) > [η](dendrimer). While the difference between dendrimer and polysaccharides may be attributed to the higher branching of the former, which leads to a higher chain density in solution, the difference between dextran and dextrin is likely a result of the variation in solution behavior of α-(1→6) vs α-(1→4) linked carbohydrates. The solution behavior of the maltodextrins studied indicates that debranching in their manufacture appears to have been more thorough than in that of β-limiting dextrins studied by other groups. Comparison of molecular radii obtained from SEC data to radii from molecular dynamics studies show Starburst dendrimers behave as θ-stars with functionality between 1 and 4. Additionally, electrospray ionization mass spectrometry was employed to determine M(w), M(n), and PD of Astramol dendrimers.     

Half-Lives and Intensities of X-ray and γ-Ray Emission of 113Sn, 117mSn,and 119mSn

The nuclear-physical properties of ¹¹³Sn, ^117mSn, and ^119mSn were studied by semiconductor X-ray and -ray spectrometry. The following energies (keV) and intensities (rel. units, in parentheses) of X-ray and -emission were obtained. ¹¹³Sn: 255 (3.2), 392 (100); ^117mSn: 156 [2.4(1)], 158 (100); ^119mSn: 23.8 [71.6(15)], KX 25 (100), intensity ratio 0.716(15). The K K ratios for ¹¹³Sn, ^117mSn, and ^119mSn are 4.5(1), 4.6(2), and 4.4(2), and the half-lives T _1/2 of these nuclides (days) are 115±1, 13.98±0.07, and 285±9, respectively (the errors are given for the confidence level of 0.95). The results are compared to the published data.     

Where, and how, does a nanowire break?

Using molecular dynamics (MD) simulation, we studied the structural transformation and breaking mechanism of a single crystalline copper nanowire under continuous strain. At a certain strain rate, an ensemble of relaxed initial states of the nanowire can preferentially go through one or more paths of deformation. In each deformation path, disordered atoms can be generated at the specific positions of the nanowire, where necking and breaking take place afterward. Such a breaking position is not predetermined; multiple initial states lead to a strain-rate-dependent, statistical distribution of breaking positions.     

Densities, Excess Molar Volumes, Ultrasonic Speeds, and Isentropic Compressibilities of Hexan-1-ol with 1,2-Dichloroethane, 1,2-Dibromoethane, and 1,1,2,2-Tetrachloroethene at (293.15 and 298.15) K

Densities, ρ, and ultrasonic speeds, u, of binary mixtures of hexan-1-ol with 1,2-dichloroethane, 1,2-dibromoethane, and 1,1,2,2-tetrachloroethene have been measured over the entire range of composition at (293.15 and 298.15) K and atmospheric pressure. From these data, the excess molar volumes, V ^E, deviations of ultrasonic speed, u ^D, from the ultrasonic speed of an ideal mixture, excess molar isentropic compressibilities, ${\kappa_{S,{\rm m}}^{\rm E}}$ , intermolecular free lengths, L _f, mean molecular radii, r, and thermal expansion coefficients, α, have been calculated. The experimental ultrasonic speeds have been analyzed in terms of Nomoto’s, Van Dael’s ideal mixture, and Junjie relations; Jacobson’s free length and Schaaffs’ collision factor theories; and thermoacoustical parameters.     

Synthesis,characterization, thermal,electrical and electrochemical studies of oligo nitrobenzimidazoles and their p–n diode applications

Three novel nitro oligobenzimidazoles, oligo-2-(6-nitro-1H-benzo[d]imidazol-2-yl)phenol (OBINP2), oligo-3-(6-nitro-1H-benzo[d]imidazol-2-yl)phenol (OBINP3) and oligo-4-(6-nitro-1H-benzo[d]imidazol-2-yl)phenol (OBINP4) were synthesized by oxidative polycondensation of benzimidazole monomers with NaOCl in aqueous alkaline medium. The structure of the monomers and oligomers were confirmed by FT-IR, UV–Vis, ¹H and ¹³C NMR spectroscopic techniques. The monomer BINP2 and its oligomer are showing dual emission through excited state intramolecular proton transfer process. The band gap values of monomers and oligomers were calculated from both UV–Vis spectroscopic and cyclic voltammetric data. Theoretical band gap values of monomers obtained from DFT were compared with experimentally calculated band gap values. The electrical conductivity of I₂ doped and undoped oligomers were measured using two point probe technique and are showing good correlation with the charge densities on imidazole nitrogen obtained from Huckel method. The conductivity of oligomers increases with increase in iodine vapour contact time up to 144 h. The variation of dielectric properties of oligomers has been investigated at different frequency and temperature. Among the oligomers, OBINP3 is having greater thermal stability as evidenced by its high carbine residue of around 65% at 600 °C in thermogravimetric analysis.     

Cluster and Condensed Phase Properties of Light Elements (especially B, C, N, Na and Si)

Amorphous forms of C will first be compared and contrasted with amorphous Si, the differences in chemical bonding being emphasized in relation to atomic structure. After a brief discussion of ordered layers of graphite and of BN, some attention will be focused on BN cages and polymers and on C nanotubes. Finally properties of Na metal clusters will be discussed, including fission of such charged clusters     

Synthesis,Temperature Behavior,and Hydrolytic Stability of Na–Zr and Ca–Zr Phosphate Molybdates and Phosphate Tungstates

Inorganic Materials - We have synthesized Na1 – xZr2(PO4)3 – x(ХO4)x and Сa0.5 – xZr2(PO4)3 – x(ХO4)x (X = Mo, W; 0 ≤ x ≤...     

Cork Embedded Internal Features and Contrast Mechanisms with Dei Using 18, 20, 30, 36, and 40 keV Synchrotron X-Rays

Images of the cork used for wine and other bottles are visualized with the use of diffraction-enhanced imaging (DEI) technique. Present experimental studies allowed us to identify the cracks, holes, porosity, and importance of soft-matter (soft-material) and associated biology by visualization of the embedded internal complex features of the biological material such as cork and its microstructure. Highlighted the contrast mechanisms above and below the K-absorption edge of iodine and studied the attenuation through a combination of weakly and strongly attenuating materials.     

How Do Packaging Material,Colour and Environmental Claim Influence Package,Brand and Product Evaluations?

The success of environment‐friendly packages is highly dependent on consumers' understanding and acceptance of these packages. In an experiment using a 3 × 2 between‐subject design, this study tests how style elements (i.e. the material and the colour) influence perceptions of packaging environment‐friendliness when an environmental claim is either absent from or displayed on the package. Next, the study tests the effects of the style elements and environmental claim on the evaluation of the social responsibility of the brand as well as on the inferences about product environment‐friendliness. Based on the responses of 207 participants from a Dutch consumer panel, the results show that the style elements and environmental claim influenced both the evaluations of packaging eco‐friendliness and the social responsibility of the brand. When an environmental claim about the package was displayed on the package, the results show that the material is worth a thousand words as the credibility of the claim was always significantly higher when the package was made of a fibre‐based material. Finally, the effect of the material on the inferences about product environment‐friendliness is underlined and implications for designers, managers and policy‐makers are highlighted. Copyright © 2017 John Wiley & Sons, Ltd.     

Smarter bridges,why and how?

Bridge safety, especially during extreme events, is enhanced by measurement and monitoring of critical bridge components. Enhanced safety, reliability and efficient maintenance can result from improved incident detection and assessment enabled by ‘smarter’ bridges. This article considers the problems, and discusses some solutions being investigated by the US Federal Highway Administration.     

Reticular chemistry at the atomic,molecular,and framework scales

"There's plenty of room at the bottom."Feynmans talk has been frequently quoted for the advent of nanoscience,which gives profound perspectives of arranging atoms in the way we want[1].With the same bottom-up manner,reticular chemistry is concerned with linking of molecular building blocks by strong bonds to make crystalline open frameworks[2].The most im portant category practicing this bottom-up strategy at framework scale is m etal-organic frameworks(MOFs)coined in 1995[3],which leads to synthetic crystals featuring ultrahigh surface areas,fine-tuned pore metrics,and multivariate functionalities[4-16].The same strategy has also been successfully extended to crystalline covalent organic frameworks(COFs)from entirely organic building blocks through strong covalent bonds[17-19],whose crystal structures are now possible to be determ ined by 3D electron diffraction[20]and even X-ray diffraction[21].Recently,molecular weaving adds exotic flavors to reticular chemistry enabling the interlacing,knitting,and crocheting with molecular threads to make resilient nanotextiles[22].We envision the future of this field lays on the anisotropic reticular chem istry[23],where the components can be precisely arranged and manipulated along a specific direction.The atomic arrangement of various metals in the structures can be eventually read.     

A High-Voltage,Dendrite-Free,and Durable Zn–Graphite Battery

The intrinsic advantages of metallic Zn, like high theoretical capacity (820 mAh g⁻¹), high abundance, low toxicity, and high safety have driven the recent booming development of rechargeable Zn batteries. However, the lack of high-voltage electrolyte and cathode materials restricts the cell voltage mostly to below 2 V. Moreover, dendrite formation and the poor rechargeability of the Zn anode hinder the long-term operation of Zn batteries. Here a high-voltage and durable Zn–graphite battery, which is enabled by a LiPF₆-containing hybrid electrolyte, is reported. The presence of LiPF₆ efficiently suppresses the anodic oxidation of Zn electrolyte and leads to a super-wide electrochemical stability window of 4 V (vs Zn/Zn²⁺). Both dendrite-free Zn plating/stripping and reversible dual-anion intercalation into the graphite cathode are realized in the hybrid electrolyte. The resultant Zn–graphite battery performs stably at a high voltage of 2.8 V with a record midpoint discharge voltage of 2.2 V. After 2000 cycles at a high charge–discharge rate, high capacity retention of 97.5% is achieved with ≈100% Coulombic efficiency.     

Density of α-pinene, Β-pinene,limonene, and essence of turpentine

Densities of ga-pinene, -pinene, limonene, and essence of turpentine have been measured at 293.15, 298.15, 303.15, 308.15, and 313.15 K, at atmospheric pressure, with a mechanical oscillator densimeter. Benzene and cyclohexane were used as calibration fluids. The precision is of the order of 0.01 kg · m^–3, while the accuracy is estimated to be 0.1%. A linear representation of the variation of the density with temperature reproduces the experimental data within 0.2%.     

Physicochemical Properties of Sb, Sn, Zn, and Sb–Sn System

The physicochemical properties, viscosity, density, and surface tension, were measured using the discharge crucible method (DC) on five alloys of Sb–Sn. The performance of the DC method was demonstrated with measurements on pure metals Sb, Sn, Zn, and comparisons with the corresponding literature data. The results reported in this study are for Sb–Sn alloys containing (10, 20, 25, 50, and 75) at% of Sb at 550 K to 850 K. The results show that all the physicochemical properties decrease with decreasing temperature and increase with increasing Sb content in the alloy. The experimentally measured surface-tension values are compared with the Butler model. Several models for viscosity are compared and discussed.     

Nonuniform Impurity and Electric-Field Distributions in High-Resistivity Si〈W,Au〉, Bi12GeO20, and CdS Crystals

The impurity and electric-field distributions in high-resistivity SiW,Au, Bi₁₂GeO₂₀, and CdS semiconductors are studied by the local PC method. The applicability of this method to assessing impurity and field distributions is analyzed. For n-SiW,Au, with the Au dopant completely compensated by shallow donors, the distribution of empty gold centers along the sample is obtained. At low temperature, the electric-field distribution is nonuniform, which is probably due to exclusion at the semiconductor contacts. Both the field and impurity distributions along the Bi₁₂GeO₂₀ and CdS crystals are found to be nonuniform.     

Simulations and experiments of open hole tension tests – Assessment of intra-ply plasticity,damage, and localization

Laminated composites with various layups of unidirectional carbon fiber reinforced epoxy are investigated by numerical modeling and experimental testing. Open hole tension configurations are studied with special considerations of the non-linear behavior of the plies. Computational predictions are based on an anisotropic constitutive material law which includes plasticity and damage, the latter comprise hardening as well as softening. Experimental evaluations include a 3D image correlation photogrammetry system for capturing the strain fields of the sample surfaces.