Fluorenyl-containing sulfonated poly(aryl ether ether ketone ketone)s (SPFEEKK) for fuel cell applications

A series of fluorenyl-containing sulfonated poly(aryl ether ether ketone ketone)s (SPFEEKK) were synthesized via aromatic nucleophilic substitution polymerization. The sulfonation content (SC) was controlled by the feed ratios of sulfonated and nonsulfonated monomers. Flexible and strong membranes in the sulfonic acid form were obtained from cast membranes in the sodium salt forms by treatment with acid. The thermal properties, water uptake, swelling ratio, water state, oxidative stability, proton conductivity and methanol permeability were investigated. All the polymers had proton conductivities greater than 1 × 10⁻² S/cm at room temperature, and the conductivity values of m-SPFEEKK-80 and p-SPFEEKK-80 were up to 1.86 × 10⁻¹ and 1.78 × 10⁻¹ S/cm at 100 °C. This series of polymers also possessed good dimensional stability in water and low methanol crossover.     

Optimisation of ICPMS collision/reaction cell conditions for the simultaneous removal of argon based interferences of arsenic and selenium in water samples

The optimisation of ICPMS collision/reaction cell conditions for the simultaneous analysis of arsenic and selenium is described. A mixture of 3.8 mL min⁻¹ of H₂ and 0.5 mL min⁻¹ of He was found to be suitable for the removal of both ArAr⁺ and ArCl⁺ interferences. Detection limits down to 30 ng (element) L⁻¹ in total analysis, and between 81 and 230 ng (element) L⁻¹ in speciation analysis were achieved in chloride matrix (1 g L⁻¹ NaCl). After validation, the method was applied to commercially available mineral waters.     

A finite volume cell‐centered Lagrangian hydrodynamics approach for solids in general unstructured grids

A finite volume cell‐centered Lagrangian hydrodynamics approach, formulated in Cartesian frame, is presented for solving elasto‐plastic response of solids in general unstructured grids. Because solid materials can sustain significant shear deformation, evolution equations for stress and strain fields are solved in addition to mass, momentum, and energy conservation laws. The total stress is split into deviatoric shear stress and dilatational components. The dilatational response of the material is modeled using the Mie‐Grüneisen equation of state. A predicted trial elastic deviatoric stress state is evolved assuming a pure elastic deformation in accordance with the hypo‐elastic stress‐strain relation. The evolution equations are advanced in time by constructing vertex velocity and corner traction force vectors using multi‐dimensional Riemann solutions erected at mesh vertices. Conservation of momentum and total energy along with the increase in entropy principle are invoked for computing these quantities at the vertices. Final state of deviatoric stress is effected via radial return algorithm based on the J‐2 von Mises yield condition. The scheme presented in this work is second‐order accurate both in space and time. The suitability of the scheme is evinced by solving one‐ and two‐dimensional benchmark problems both in structured grids and in unstructured grids with polygonal cells. Copyright © 2013 John Wiley & Sons, Ltd.     

Investigation of proton conductivity of anhydrous proton exchange membranes prepared via grafting vinyltriazole onto alkaline‐treated PVDF

This work uses a simple “grafting through” approach in the preparation of anhydrous poly(vinylidene fluoride) (PVDF)‐g‐PVTri polymer electrolyte membranes (PEMs). Alkaline‐treated PVDF was used as a macromolecule in conjunction with vinyltriazole in the graft copolymerization. The obtained polymer was subsequently doped with triflic acid (TA) at different stoichiometric ratios with respect to triazole units and the anhydrous PEMs (PVDF‐g‐PVTri‐(TA)_x) were prepared. All samples were characterized by FTIR and ¹H NMR. The composition of PVDF‐g‐PVTri was determined by energy dispersive spectroscopy. Thermal properties of the membranes were examined by thermogravimetric analysis and differential scanning calorimetry. The surface roughness and morphology of the membranes were studied using atomic force microscopy, X‐ray diffraction, and scanning electron microscopy. PVDF‐g‐PVTri‐(TA)₃ (C3‐TA₃) with a degree of grafting of 47.22% showed a maximum proton conductivity of 0.09 S cm^?1 at 150 °C and anhydrous conditions. © 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2014 , 52, 1885–1897     

Polyol-mediated synthesis of Cu2ZnSn(S,Se)4 kesterite nanoparticles and their use in thin-film solar cells

Cu₂ZnSnS₄ kesterite nanoparticles (CZTS) with a particle diameter of 10–20 nm are prepared by a polyol-mediated synthesis with diethylene glycol as the liquid phase. The polyol – a high-boiling multidentate alcohol − allows controlling the particle size and agglomeration as well as preparing readily crystalline nanoparticles. The as-prepared kesterite nanoparticles exhibit an overall composition of Cu_1.56Zn_1.29Sn_1.16S_4.59 and a band gap of 1.37 eV. As a first test, thin-film solar cells are manufactured after layer deposition of the as-prepared CZTS nanoparticles and conversion to Cu₂ZnSn(S,Se)₄ (CZTSSe) via gas-phase selenization. The volume increase of about 15% due to the CZTS-to-CZTSSe conversion supports the formation of a dense layer, reduces the interparticulate surfaces and leads to a reduction of the band gap to 1.14 eV. The chemical composition of the as-prepared CZTS nanoparticles and of the deposited CZTSSe thin film prior and after selenization are studied in detail by energy-dispersive X-ray spectroscopy, Raman spectroscopy and X-ray fluorescence analysis. All these methods confirm the intended copper-poor and zinc-/tin-rich CZTS/CZTSSe composition. The resulting thin-film solar cells show an open-circuit voltage of 247.3 mV, a short-circuit current density of 21.3 mA/cm², a fill factor of 41.1% and a power-conversion efficiency of 2.2%.     

A new direction in design and manufacture of co-sensitized dye solar cells: Toward concurrent optimization of power conversion efficiency and durability

A novel methodology was implemented in the present study to concurrently control power conversion efficiency (η) and durability (D) of co-sensitized dye solar cells. Applying response surface methodology (RSM) and Desirability Function (DF), the main influential assembling (dye volume ratio and anti-aggregation agent concentration) and operational (performance temperature) parameters were systematically changed to probe their main and interactive effects on the η and D responses. Individual optimization based on RSM elucidated that D can be solely controlled by changing the ratio of vat-based organic photosensitizers, whereas η takes both effects of dye volume ratio and anti-aggregation concentration into account. Among the studied factors, the performance temperature played the most vital role in η and D regulation. In particular, however, multi-objective optimization by DF explored the degree to which one should be careful about manipulation of assembling and operational parameters in the way maximization of performance of a co-sensitized dye solar cell.     

Homogeneous liquid crystal alignment on poly(vinylidene fluoride-trifluoroethylene) films subjected to ion-beam irradiation

We demonstrate homogeneous and uniform liquid crystal (LC) alignment on poly(vinylidene fluoride-trifluoroethylene) [PVDF-TrFE] films using ion-beam (IB) irradiation and a performance improvement of twisted nematic (TN) cells using IB-irradiated PVDF-TrFE films. Spontaneous ferroelectricity of the PVDF-TrFE films was modified by IB irradiation, which affected the LC alignment properties. The variation in the pre-tilt angles of the LC molecules on the IB-irradiated PVDF films is attributed to surface reformation, including defluorination and oxidation because the pre-tilt angles of LC molecules can be controlled by adjusting the fluorine content. The results of contact angle measurements supported this phenomenon. A 58% reduction in the switching voltage was observed for TN cells, indicating that the IB-irradiated PVDF-TrFE films are a promising candidate for use as an alignment layer.