for Journals by Title or ISSN for Articles by Keywords help
 Subjects -> ENGINEERING (Total: 2266 journals)     - CHEMICAL ENGINEERING (190 journals)    - CIVIL ENGINEERING (181 journals)    - ELECTRICAL ENGINEERING (100 journals)    - ENGINEERING (1197 journals)    - ENGINEERING MECHANICS AND MATERIALS (390 journals)    - HYDRAULIC ENGINEERING (55 journals)    - INDUSTRIAL ENGINEERING (64 journals)    - MECHANICAL ENGINEERING (89 journals) ENGINEERING (1197 journals)            First | 1 2 3 4 5 6 | Last
 Ionics   [SJR: 0.486]   [H-I: 36]   [2 followers]  Follow         Hybrid journal (It can contain Open Access articles)    ISSN (Print) 1862-0760 - ISSN (Online) 0947-7047    Published by Springer-Verlag  [2335 journals]
• Synthesis of x LiVPO 4 F· y Li 3 V 2 (PO 4 ) 3 /C composite as a
potential cathode material for Li-ion batteries
• Authors: Shengkui Zhong; Wei Hong; Xiaoping Zhang; Jiequn Liu; Yunxiang Li; Yanling Shi; Ling Wu
Pages: 813 - 819
Abstract: xLiVPO4F·yLi3V2(PO4)3/C cathode materials are prepared by a two-step carbon coating method. XRD results show that all the xLiVPO4F·yLi3V2(PO4)3/C composites (x:y ≠ 0) contain both LiVPO4F and Li3V2(PO4)3 phases, and no impurities are detected. SEM results show that the average primary size of the composites is 0.3–1 μm. All the composites show less aggregation than the single LiVPO4F/C and Li3V2(PO4)3/C samples. Electrochemical measurements show that the composites have better electrochemical performance than LiVPO4F/C. Among all the composites, 2LiVPO4F·Li3V2(PO4)3/C shows the optimal electrochemical properties. The sample possesses the specific capacities of 143.9 and 112.6 mAh g−1 at 0.1 C and 2 C rates, respectively, and shows flat discharge platforms around 4.2, 4.1, 3.7, and 3.6 V under low current rate. The sample also exhibits good cycle performance.
PubDate: 2017-04-01
DOI: 10.1007/s11581-016-1875-y
Issue No: Vol. 23, No. 4 (2017)

• Effect of calcination conditions on lithium conductivity in Li 1.3 Ti 1.7
Al 0.3 (PO 4 ) 3 prepared by sol-gel route
• Authors: K. G. Schell; E. C. Bucharsky; F. Lemke; M. J. Hoffmann
Pages: 821 - 827
Abstract: In order to study the influence of powder calcination temperature on lithium ion conductivity, synthesized Li1.3Ti1.7Al0.3(PO4)3 (LATP) was calcined at temperatures between 750 and 900 °C. The shape and size of the particles were characterized employing scanning electron microscopy (SEM), and specific surface area of the obtained powder was measured. The crystallinity grade of different heat-treated powders was calculated from XRD spectra. Posteriorly, all powders were sintered at 1100 °C employing field-assisted sintering (SPS), and the electrical properties were correlated to the calcination conditions. The highest ionic conductivity was observed for samples made out of powders calcined at 900 °C.
PubDate: 2017-04-01
DOI: 10.1007/s11581-016-1883-y
Issue No: Vol. 23, No. 4 (2017)

• Effect of Li content on the electrochemical performance of Li 1 + x (Mn
0.675 Ni 0.1625 Co 0.1625 ) 1 − x O 2 cathode materials for high-power
Li-ion batteries
• Authors: Linsen Zhang; Huan Wang; Lizhen Wang
Pages: 829 - 835
Abstract: Li-rich Li1 + x (Mn0.675Ni0.1625Co0.1625)1 − x O2 (x = 0.1, 0.2, 0.3, and 0.4) materials were prepared using MCO3 precursors through hydrothermal treatment with using urea as precipitator. X-ray diffraction (XRD), scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS), transmission electron microscope (TEM), X-ray photoelectron spectroscopy (XPS), cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS), and charge/discharge test are conducted to evaluate the physical and electrochemical properties of the spherical mesocrystal and resulting materials. Results show that the c/a ratio for the cathode material decreases and the layered structure deteriorates with increasing Li content. Li1.2Mn0.54Ni0.13Co0.13O2 (x = 0.2) exhibits the excellent electrochemical performance with an initial discharge capacity of 339 mAh g−1 at 20 mA g−1 and a capacity of 115 mAh g−1 at 400 mA g−1 after 50 cycles.
PubDate: 2017-04-01
DOI: 10.1007/s11581-016-1882-z
Issue No: Vol. 23, No. 4 (2017)

• A study of optical absorption and dielectric properties in lithium
chromium diphosphate compound
• Authors: M. Sassi; A. Oueslati; N. Moutia; K. Khirouni; M. Gargouri
Pages: 847 - 855
Abstract: The optical properties of diphosphate LiCrP2O7 compound prepared by the classic ceramic method were recorded at room temperature. Absorption spectrum shows the presence of five characteristics bands related to the octahedral transitions of Cr3+ from ground term 4A2g to excited terms. Crystal field strength and inter electronic repulsion Racah parameters were deduced. The calculated value of direct $${E}_g^{\mathrm{direct}}$$ =1.62 eV energy gap has been found using Tauc’s procedure. Besides, the dielectric properties were carried out by impedance spectroscopy at different temperatures (460–700 K). The frequency and temperature dependent of the real ε ′ and imaginary ε ″ parts of the dielectric constant were discussed. The variation of the frequency power law of the imaginary part of dielectric constant was analyzed in terms of two different conduction mechanisms. Furthermore, the modulus plots can be characterized by the empirical Kohlrausch–Williams–Watts (K.W.W.) function and the obtained values of activation energies deduced from relaxation frequency are in order of E a (I) = 0.49 eV and E a (II) = 0.87 eV. Graphical abstract Optical and dielectric proprieties of lithium chromium diphosphate
PubDate: 2017-04-01
DOI: 10.1007/s11581-016-1903-y
Issue No: Vol. 23, No. 4 (2017)

• Li + ion conductivity and transport properties of LiYP 2 O 7 compound
• Authors: A. Oueslati
Pages: 857 - 867
Abstract: A lithium yttrium diphosphate LiYP2O7 was prepared by a solid-state reaction method. Rietveld refinement of the X-ray diffraction pattern suggests the formation of the single phase desired compound with monoclinic structure at room temperature. The infrared and Raman spectrum of this compound was interpreted on the basis of P2O7 4− vibrations. The AC conductivity was measured in the frequency range from 100 to 106 Hz and temperatures between 473 and 673 K using impedance spectroscopy technique. The obtained results were analyzed by fitting the experimental data to the equivalent circuit model. The Cole–Cole diagram determined complex impedance for different temperatures. The angular frequency dependence of the AC conductivity is found to obey Jonscher’s relation. The temperature dependence of σ AC could be described in terms of Arrhenius relation with two activation energies, 0.87 eV in region I and 1.36 eV in region II. The study of temperature variation of the exponent(s) reveals two conduction models: the AC conduction dependence upon temperature is governed by the correlated barrier hopping (CBH) model in region I (T < 540 K) and non-overlapping small polaron tunneling (NSPT) model in region II (T > 540 K). The near value of activation energies obtained from the equivalent circuit and DC conductivity confirms that the transport is through ion hopping mechanism dominated by the motion of the Li+ ion in the structure of the investigated material.
PubDate: 2017-04-01
DOI: 10.1007/s11581-016-1878-8
Issue No: Vol. 23, No. 4 (2017)

• Effects of Li + co-doping on the concentration quenching threshold and
luminescence of GdVO 4 :Eu 3+ nanophosphors
• Authors: Yinglin Yan; Wei Zhang; Bing Ren; Lisheng Zhong; Yunhua Xu
Pages: 869 - 875
Abstract: Europium ions (Eu3+) and Lithium ions (Li+) codoped gadolinium orthovanadate with a tetragonal phase had been successfully synthesized by an efficient hydrothermal method. X-ray diffraction (XRD), scanning electron microscopy (SEM), and photoluminescence (PL) were utilized to characterize the microstructure, morphology, and luminescent properties of as-prepared samples. The various concentrations (0∼14 at.%) of Li ions were applied to investigate the effect of Li+ co-doping concentration on the crystalline structure, microstructure, and emission intensity of GdVO4:Eu3+, Li+ nanophosphors. The results demonstrated that Li+ ion co-doping changes the lattice parameters in two different ways. Moreover, the optical photoluminescent property was obtained when the Li+ co-doping concentration is 10 at.%. The influence of Li+ co-doping on the concentration quenching effect of Eu3+ was discussed as well. The concentration quenching threshold of Eu3+ was increased distinguishably. The potential mechanism was proposed in this paper.
PubDate: 2017-04-01
DOI: 10.1007/s11581-016-1879-7
Issue No: Vol. 23, No. 4 (2017)

• Investigation of N-doped carbon-coated lithium zinc titanate using chitin
as a carbon source for lithium-ion batteries
• Authors: Xinyi Liu; Chi Chen; Yuanxin Wu
Pages: 889 - 896
Abstract: Nitrogen-doped carbon-coated Li2ZnTi3O8 (NC-LZTO) anode material was fabricated with chitin as a carbon source by precoating process via a facile solid-state reaction method. The effects of nitrogen-doped carbon layer on the crystal structure, surface morphology, and electrochemical performances were studied. The NC-LZTO samples show the significant improvement in rate capability compared with carbon-coated Li2ZnTi3O8 (C-LZTO) sample derived from glucose and naked Li2ZnTi3O8 (LZTO) sample. At the current rates of 0.5, 1, 2, 5, and 10 C, the discharge-specific capacities of the NC-LZTO sample are 275.6, 262.8, 244.8, 217, and 190.6 mAh g−1, respectively. After 200 cycles at 2 C, its capacity retention is 98.7%. The increased electrochemical performance of NC-LZTO can be ascribed to the larger specific surface, smaller particle size, and better electronic conductivity.
PubDate: 2017-04-01
DOI: 10.1007/s11581-016-1890-z
Issue No: Vol. 23, No. 4 (2017)

• Design and synthesis of a novel 3D hierarchical mesocarbon microbead as
anodes for lithium ion batteries and sodium ion batteries
• Authors: Doudou Zhao; Qiang Ru; Shejun Hu; Xianhua Hou
Pages: 897 - 905
Abstract: This work presents a feasible route for the facile synthesis of three-dimensional (3D) hierarchical mesocarbon microbead (MCMB) as anodes for lithium ion batteries (LIBs) and sodium ion batteries (SIBs). The MCMB is oxidized by modified hummers method, and then the precursor is treated by hydrogen reduction to form the HMCMB. The HMCMB with graphene-like architecture has high specific surface, sufficient pore volume, and increased interlayer spacing, which can provide more active insertion/extraction sites and reduce the Li+/Na+ diffusion resistance. When employed as anode materials for LIBs and SIBs, HMCMB anodes exhibit improved lithium and sodium storage capability. The HMCMB delivers a higher reversible capacity (471.1 and 177.5 mAh g−1 at 100 mA g−1 after 100 cycles) and a good rate performance (250 and 121 mAh g−1 even at 1000 mA g−1) for LIBs and SIBs, respectively.
PubDate: 2017-04-01
DOI: 10.1007/s11581-016-1884-x
Issue No: Vol. 23, No. 4 (2017)

• Effects of carbon content on the electrochemical properties of spherical
pyrrhotine/carbon nanocomposites
• Authors: Xiaodong Zheng
Pages: 907 - 915
Abstract: Spherical pyrrhotine/carbon nanocomposites with different carbon contents were synthesized by a solvothermal method followed by heat treatment. The carbon content of the nanocomposites was controlled by changing the amount of the carbon precursor. The samples were characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM); the influence of carbon layer thickness on the electrochemical performance was analyzed by charge/discharge cycling and X-ray photoelectron spectroscopy (XPS). Results show that the moderate carbon layer displays a positive effect in improving reversible capacity and the rate capability. The optimal carbon content in the pyrrhotine/carbon nanocomposites was about 15 wt.%, which can retain a high reversible capacity of 689.5 mAh/g even after 50 cycles at 0.1 C and an excellent rate capability of 393.4 mAh/g at 5 C. The synthesized nanocomposites show a promising potential as a novel anode material for lithium-ion batteries.
PubDate: 2017-04-01
DOI: 10.1007/s11581-016-1881-0
Issue No: Vol. 23, No. 4 (2017)

• Effect of drying temperature on a thin PVDF-HFP/PET composite nonwoven
separator for lithium-ion batteries
• Authors: Weibiao Li; Xiaozhe Li; Xiaohua Xie; Anbao Yuan; Baojia Xia
Pages: 929 - 935
Abstract: A thin composite separator with polyethylene terephthalate nonwoven membrane as the structural support and polyvinylidene fluoride-hexafluoropropylene as the coating layer for lithium-ion batteries was prepared by a simple dip-coating process. The effect of different drying temperatures on the performance of the composite separator was investigated. The results indicate that 80 °C is the optimal drying temperature, preventing leakage current problems and providing a well-developed porous structure. The drying of the composite separator at 80 °C provides a superior thermal stability, better wettability with electrolyte, higher electrolyte uptake, and ionic conductivity compared to commercially available polypropylene (PP) separator. Furthermore, the electrochemical performance consisting of electrochemical stability, self-discharge, cycle performance, rate performance of the composite separator, and PP were determined. The drying of the composite separator at 80 °C shows almost the same oxidation stability and self-discharge performance, but a better cycling and rate performance than the PP separator.
PubDate: 2017-04-01
DOI: 10.1007/s11581-016-1891-y
Issue No: Vol. 23, No. 4 (2017)

• Acid-base high temperature proton exchange membranes prepared from
phosphonic acid functionalized siloxane
• Authors: Jingluan Xiang; Chunhui Shen; Shanjun Gao; Wei Qian
Pages: 949 - 958
Abstract: One kind of acid-base high temperature proton exchange membranes has been prepared from amino trimethylene phosphonic acid (ATMP), epoxycyclohexyethyltrimethoxysilane (EHTMS), and 3-aminopropyltriethoxysilane (APTES) by sol-gel process. The structural characteristics of these membranes with different amount of APTES were investigated by FT-IR, XRD, and SEM. These membranes showed excellent dimensional stability in water with the contribution of flexible ionic network structure and were thermally stable up to about 200 °C. In addition, the proton conductivity of the membranes increased with increasing temperature over the range of 20 to 140 °C, up to a maximum of 2.63 × 10−2 S cm−1 at 140 °C under anhydrous condition. The high proton conductivity was attributed to the formation of hydrogen bond network through the synergistic effect of N and P. The activation energy value of membranes became lower from 0.46 to 0.30 eV because of the acid-base pairs. The variable-temperature FT-IR further proved the formation of hydrogen bond network in the membrane.
PubDate: 2017-04-01
DOI: 10.1007/s11581-016-1900-1
Issue No: Vol. 23, No. 4 (2017)

• Effects of lithium bis(oxalato)borate on electrochemical stability of
[Emim][Al 2 Cl 7 ] ionic liquid for aluminum electrolysis
• Authors: Haiyan Lang; Junling Zhang; Yanhong Kang; Shimou Chen; Suojiang Zhang
Pages: 959 - 966
Abstract: Electrodeposition of aluminum from ionic liquids has been considered a promising approach to low-temperature aluminum electrolysis. In this study, we first investigated the electrochemical stability of 1-ethyl-3-methylimidazolium chloride ([Emim][Al2Cl7]) electrolyte, which is a typically used electrolyte for aluminum electrodeposition. It was found that part of imidazole ions decomposed on the cathode during the electrolysis process, especially when the temperature was at or over 353 K. In order to enhance the stability of the electrolyte, we further studied the effects of lithium salt and lithium bis(oxalato)borate (LiBOB), on the electrochemical stability of the [Emim][Al2Cl7] ionic liquid system. It was found that the electrochemical window of the electrolyte was broadened from 2.59 to 2.74 V at 373 K by addition of 1 mol% LiBOB. With the existence of LiBOB, the reduction current density of Al2Cl7 - increased before −0.58 V and the electrodissolution of Al was more complete. The possible mechanism on the LiBOB increases the stability of the electrolyte systems also discussed based on our theoretical calculations.
PubDate: 2017-04-01
DOI: 10.1007/s11581-016-1889-5
Issue No: Vol. 23, No. 4 (2017)

• Effect of sintering temperature on the elemental diffusion and electrical
conductivity of SrTiO 3 /YSZ composite ceramic
• Authors: Q. Q. Yang; B. Meng; Z. L. Lin; X. K. Zhu; F. Yang; S. Wu
Pages: 967 - 975
Abstract: The 50 vol% SrTiO3/yttria-stabilized zirconia (YSZ) composite ceramic was prepared through powder sintering route in 1400∼1500 °C. Only the cubic YSZ and SrTiO3 phases are detected in all the sintered ceramics, and the typical XRD peak positions of both phases have varied dramatically. The grain sizes and relative densities of all specimens increase evidently with the sintering temperature. The width of the SrTiO3/YSZ interfacial region increases from 100.4 to 468.8 nm as the sintering temperature rises from 1400 to 1500 °C. The total electrical conductivities of the sample sintered at 1500 °C are remarkably higher than those at 1400 and 1450 °C, while the ion transference numbers drop from 0.837 to 0.731 with sintering temperature from 1400 to 1500 °C. The variations in the electrical properties above can be interpreted based on the effects of sintering temperature on the elemental diffusions during the sintering process.
PubDate: 2017-04-01
DOI: 10.1007/s11581-016-1866-z
Issue No: Vol. 23, No. 4 (2017)

• Hexagonal-like NiCo 2 O 4 nanostructure based high-performance
supercapacitor electrodes
• Authors: V. Venkatachalam; A. Alsalme; A. Alghamdi; R. Jayavel
Pages: 977 - 984
Abstract: A novel approach of double hydroxide-mediated synthesis of nickel cobaltite (NiCo2O4) electro-active material by the hydrothermal method is reported. The obtained NiCo2O4 electro-active material displays the spinel cubic phase and hexagonal-like morphology. Thermogravimetry analysis confirms the thermal stability of the electrode material. The functional groups and phase formation of NiCo2O4 have been confirmed by FT-IR and Raman spectral analysis. The modified NiCo2O4 electrode exhibits the highest specific capacitance of 767.5 F g−1 at a current density of 0.5 A g−1 in 3 M KOH electrolyte and excellent cyclic stability (94 % capacitance retention after 1000 cycles at a high current density of 5 A g−1). The excellent electrochemical performance of the electrode is attributed to the hexagonal-like morphology, which contributes to the rich surface electro-active sites and easy transport pathway for the ions during the electrochemical reaction. The attractive Faradic behavior of NiCo2O4 electrode has been ascribed to the redox contribution of Ni2+/Ni3+ and Co2+/Co3+ metal species in the alkaline medium. The symmetrical two-electrode cell has been fabricated using the NiCo2O4 electro-active material with excellent electrochemical properties for supercapacitor applications.
PubDate: 2017-04-01
DOI: 10.1007/s11581-016-1868-x
Issue No: Vol. 23, No. 4 (2017)

• Gold nanoclusters doped poly(3,4-ethylenedioxythiophene) for highly
sensitive electrochemical sensing of nitrite
• Authors: Xiaojian Fan; Peipei Lin; Shaoping Liang; Ni Hui; Ruiqiao Zhang; Jiuju Feng; Guiyun Xu
Pages: 997 - 1003
Abstract: Poly(3,4-ethylenedioxythiophene) (PEDOT) doped with bovine serum albumin-stabilized Au nanoclusters (AuNCs) was successfully synthesized through electrochemical polymerization in a solution containing EDOT monomer and AuNCs. The obtained PEDOT/AuNCs composite possessed a microstructure with AuNCs evenly distributed within the PEDOT film as dopants. The PEDOT/AuNCs modified electrode exhibited high electrocatalytic activity toward nitrite oxidation, and it was further developed into an amperometric sensor for nitrite. If operated at 0.80 V (vs. SCE), the linear range of the sensor was from 0.05 to 2600 μM, with a very low limit of detection of 17 nM (S/N = 3).
PubDate: 2017-04-01
DOI: 10.1007/s11581-016-1865-0
Issue No: Vol. 23, No. 4 (2017)

• A novel electrochemical sensor based on magneto LDH/Fe 3 O 4 nanoparticles
@ glassy carbon electrode for voltammetric determination of tramadol in
real samples
Pages: 1005 - 1015
Abstract: The electrochemical behavior of tramadol (TRA) on magneto layer double hydroxide (LDH)/Fe3O4@glassy carbon electrode (LDH/Fe3O4@GCE) was evaluated. Some theoretical thermodynamic and kinetic parameters were also determined using chronoamperometric and voltammetric methods. The ability of the modified electrode to determine trace amounts of TRA was studied using differential pulse voltammetry (DPV) as a sensitive electrochemical method. For characterizing and investigating the performance of LDH/Fe3O4@GCE, various methods including scanning electron microscopy (SEM), X-ray diffraction (XRD), cyclic voltammetry (CV), and DPV were used. The effect of pH, scan rate, and time on the voltammetric response of TRA were investigated. Under the optimized conditions, the anodic peak current was linear for the concentration of TRA in the range 1.0–200.0 μmol L−1 with the detection limit of 3.0 × 10−1 μmol L−1. This method was also successfully used to detect the concentration of TRA in human serum and urine samples.
PubDate: 2017-04-01
DOI: 10.1007/s11581-016-1871-2
Issue No: Vol. 23, No. 4 (2017)

• Electrochemical deposition of carbon materials incorporated nickel sulfide
composite as counter electrode for dye-sensitized solar cells
• Authors: J. Theerthagiri; R. A. Senthil; Prabhakarn Arunachalam; K. Amarsingh Bhabu; A. Selvi; J. Madhavan; K. Murugan; A. K. Arof
Pages: 1017 - 1025
Abstract: The various carbon-based materials incorporated nickel sulfide (NiS) composites have been electrochemically deposited on fluorine-doped tin oxide (FTO) glass substrate. The structure, surface morphology, and elemental composition of the electrodeposited NiS composite materials were characterized by XRD, HR-SEM, and EDS. The electrochemically deposited various NiS composites such as NiS/AB (acetylene black), NiS/VC (Vulcan carbon), and NiS/MWCNT (multi walled carbon nanotubes) have been served as an efficient, low-cost counter electrode (CE) materials for dye-sensitized solar cells (DSSCs). Electrochemical impedance spectroscopy and cyclic voltammetry of NiS/AB CE composite materials exhibits a good conductivity and superior electrocatalytic performance over other various carbon incorporated materials. The positive synergistic effects, which increase the active catalytic sites and improved interfacial charge transfer, may be accountable for the superior electrocatalytic performance of NiS/AB composite materials The fabricated DSSC with NiS/AB CE reached a power conversion efficiency of 6.75%, which is equivalent with platinum electrode (7.20%). These results validate that the electrochemically deposited NiS/AB composite film is an auspicious alternative for low-cost and high efficient DSSCs.
PubDate: 2017-04-01
DOI: 10.1007/s11581-016-1885-9
Issue No: Vol. 23, No. 4 (2017)

• Electrodeposition of Cu–Ga precursor layer for CuGaS 2 solar energy thin
film from alcohol solution
• Authors: Zhou Cao; Sui Yang; Mang Wang; Xiaopan Huang; Hongxing Li; Jie Yi; Jianxin Zhong
Pages: 1027 - 1033
Abstract: CuGaS2 thin film is fabricated with electrochemical deposition of Cu–Ga alloys from alcohol solution to eliminate the interference of hydrogen evolution reaction (HER). The process involves electrodeposition of Cu–Ga precursor on molybdenum substrate and subsequential annealing in sulfur vapor. The formation of CuGa2 alloy in precursor is observed and pure ternary chalcopyrite CuGaS2 phase in good polycrystalline structure without secondary phase is obtained after thermal treatment. The influence of the applied deposition potential on the crystalline phase, morphology, compositions, and carrier concentration of the films were investigated. The results show that an optimum choice of electrodeposition potential is necessary to obtain a pure crystallized CuGaS2 thin film. A lower absolute deposition potential results in a higher Cu/Ga ratio and the emergence of CuS secondary phase after annealing in sulfur atmosphere. The crystal size of the formed CuGaS2 phase with thermal annealing process increases with the positive shift of deposition potential. Impedance spectroscopy test demonstrates the semiconductor property of the synthesized CuGaS2 polycrystalline thin films are all p-type. The carrier density of the obtained CuGaS2 thin films increases with the negative shift of deposited potential.
PubDate: 2017-04-01
DOI: 10.1007/s11581-016-1888-6
Issue No: Vol. 23, No. 4 (2017)

• Phthalonitrile-terminated sulfonated poly(arylene ether nitrile)s for
direct methanol fuel cells (DMFCs) application
• Authors: Penglun Zheng; Mingzhen Xu; Xiaobo Liu
Pages: 1035 - 1041
Abstract: To improve the dimensional stability and methanol resistance, a novel phthalonitrile-terminated sulfonated poly(arylene ether nitrile)s (SPENs) to prepare cross-linked membranes for direct methanol fuel cells (DMFCs) application has been successfully implemented. Compared with SPENs, cross-linked membranes exhibited lower water uptake, swelling ratio, and methanol permeability coefficient. For example, the water uptake and swelling ratio of SPEN-70 were 50.3 wt.% and 17.0% as the values of cross-linked sulfonated poly(arylene ether nitrile)s (CSPEN)-70 were merely 15.4 wt.% and 3.2% at 20 °C. The methanol permeability of SPEN-70 was 6.7 × 10−7 cm2 s−1 as the values of CSPEN-70 were merely 1.4 × 10−7 cm2 s−1, which were all much lower than that of Nafion 117 (1.41 × 10−6 cm2 s−1) as expected. Although the proton conductivity of CSPEN slightly decreased by the introduction of cross-linked structure, it possessed higher selectivity than the SPEN and Nafion 117 due to their lower methanol permeability. The cross-linked SPEN-50 (CSPEN-50) membrane exhibited the highest selectivity, which about 30.7 times higher compared with that of Nafion 117.
PubDate: 2017-04-01
DOI: 10.1007/s11581-016-1969-6
Issue No: Vol. 23, No. 4 (2017)

• Entropic crossovers in superionic fluorites from specific heat
• Authors: Jacob Eapen; Ajay Annamareddy
Pages: 1043 - 1047
Abstract: Neutron scattering/diffraction experiments and atomistic simulations reveal that anions in fluorite superionic conductors show rapid disordering at a characteristic temperature T α, which is distinct from the superionic or λ transition temperature T λ that is associated with a quasi-divergent behavior of the thermodynamic response functions. We demonstrate that both crossovers are unmistakably captured by the variation of the ratio of specific heat to the temperature (c/T)—a surprisingly seldom-used thermodynamic metric representing the rate of change of entropy with temperature (ds/dT). With increasing temperature, c/T decreases and portrays a minimum near T α; it then increases and depicts a maximum near T λ. The minimum in c/T corresponds to the onset of superionic state characterized by a rapid increase in the ionic conductivity while the maximum represents a quasi-second-order thermodynamic phase transition. The simple c/T metric appears to be a useful experimental indicator for entropic crossovers that arise from complex disordering in a wider class of superionic conductors.
PubDate: 2017-04-01
DOI: 10.1007/s11581-017-2007-z
Issue No: Vol. 23, No. 4 (2017)

JournalTOCs
School of Mathematical and Computer Sciences
Heriot-Watt University
Edinburgh, EH14 4AS, UK
Email: journaltocs@hw.ac.uk
Tel: +00 44 (0)131 4513762
Fax: +00 44 (0)131 4513327

Home (Search)
Subjects A-Z
Publishers A-Z
Customise
APIs