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  Subjects -> ENGINEERING (Total: 2235 journals)
    - CHEMICAL ENGINEERING (188 journals)
    - CIVIL ENGINEERING (178 journals)
    - ELECTRICAL ENGINEERING (102 journals)
    - ENGINEERING (1194 journals)
    - ENGINEERING MECHANICS AND MATERIALS (374 journals)
    - HYDRAULIC ENGINEERING (54 journals)
    - INDUSTRIAL ENGINEERING (60 journals)
    - MECHANICAL ENGINEERING (85 journals)

ENGINEERING (1194 journals)            First | 2 3 4 5 6 7 8 9 | Last

International Journal of Environmental Engineering     Hybrid Journal   (Followers: 5)
International Journal of Experimental Design and Process Optimisation     Hybrid Journal   (Followers: 4)
International Journal of Fatigue     Hybrid Journal   (Followers: 36)
International Journal of Flow Control     Full-text available via subscription   (Followers: 4)
International Journal of Foresight and Innovation Policy     Hybrid Journal   (Followers: 8)
International Journal of Fracture     Hybrid Journal   (Followers: 9)
International Journal of Geotechnical Engineering     Full-text available via subscription   (Followers: 5)
International Journal of Grid and Utility Computing     Hybrid Journal   (Followers: 1)
International Journal of Heat and Fluid Flow     Hybrid Journal   (Followers: 24)
International Journal of Heat and Mass Transfer     Hybrid Journal   (Followers: 116)
International Journal of Heavy Vehicle Systems     Hybrid Journal   (Followers: 8)
International Journal of Hypersonics     Full-text available via subscription   (Followers: 4)
International Journal of Imaging Systems and Technology     Hybrid Journal   (Followers: 1)
International Journal of Impact Engineering     Hybrid Journal   (Followers: 9)
International Journal of Information Acquisition     Hybrid Journal   (Followers: 1)
International Journal of Innovation and Applied Studies     Open Access   (Followers: 5)
International Journal of Innovation Science     Full-text available via subscription   (Followers: 8)
International Journal of Innovative Technology and Research     Open Access   (Followers: 1)
International Journal of Integrated Engineering     Open Access  
International Journal of Intelligent Engineering Informatics     Hybrid Journal  
International Journal of Intelligent Systems and Applications in Engineering     Open Access   (Followers: 1)
International Journal of Lifecycle Performance Engineering     Hybrid Journal   (Followers: 1)
International Journal of Machine Tools and Manufacture     Hybrid Journal   (Followers: 6)
International Journal of Manufacturing Research     Hybrid Journal   (Followers: 7)
International Journal of Manufacturing Technology and Management     Hybrid Journal   (Followers: 9)
International Journal of Materials and Product Technology     Hybrid Journal   (Followers: 4)
International Journal of Mathematical Education in Science and Technology     Hybrid Journal   (Followers: 8)
International Journal of Mathematics in Operational Research     Hybrid Journal   (Followers: 1)
International Journal of Medical Engineering and Informatics     Hybrid Journal   (Followers: 5)
International Journal of Micro Air Vehicles     Full-text available via subscription   (Followers: 5)
International Journal of Microwave and Wireless Technologies     Hybrid Journal   (Followers: 1)
International Journal of Microwave Science and Technology     Open Access   (Followers: 4)
International Journal of Mobile Network Design and Innovation     Hybrid Journal   (Followers: 2)
International Journal of Multiphase Flow     Hybrid Journal   (Followers: 4)
International Journal of Nanomanufacturing     Hybrid Journal  
International Journal of Nanoscience     Hybrid Journal  
International Journal of Nanotechnology     Hybrid Journal   (Followers: 6)
International Journal of Nanotechnology and Molecular Computation     Full-text available via subscription   (Followers: 3)
International Journal of Navigation and Observation     Open Access   (Followers: 13)
International Journal of Network Management     Hybrid Journal   (Followers: 1)
International Journal of Nonlinear Sciences and Numerical Simulation     Hybrid Journal  
International Journal of Numerical Methods for Heat & Fluid Flow     Hybrid Journal   (Followers: 8)
International Journal of Optics     Open Access   (Followers: 1)
International Journal of Organisational Design and Engineering     Hybrid Journal   (Followers: 6)
International Journal of Pattern Recognition and Artificial Intelligence     Hybrid Journal   (Followers: 7)
International Journal of Pavement Engineering     Hybrid Journal   (Followers: 3)
International Journal of Physical Modelling in Geotechnics     Hybrid Journal   (Followers: 3)
International Journal of Plasticity     Hybrid Journal   (Followers: 7)
International Journal of Plastics Technology     Hybrid Journal   (Followers: 1)
International Journal of Polymer Analysis and Characterization     Hybrid Journal   (Followers: 6)
International Journal of Polymer Science     Open Access   (Followers: 22)
International Journal of Precision Engineering and Manufacturing     Hybrid Journal   (Followers: 6)
International Journal of Precision Engineering and Manufacturing-Green Technology     Hybrid Journal  
International Journal of Precision Technology     Hybrid Journal  
International Journal of Pressure Vessels and Piping     Hybrid Journal   (Followers: 4)
International Journal of Production Economics     Hybrid Journal   (Followers: 14)
International Journal of Quality and Innovation     Hybrid Journal   (Followers: 5)
International Journal of Quality Assurance in Engineering and Technology Education     Full-text available via subscription   (Followers: 2)
International Journal of Quality Engineering and Technology     Hybrid Journal   (Followers: 2)
International Journal of Quantum Information     Hybrid Journal  
International Journal of Rapid Manufacturing     Hybrid Journal   (Followers: 4)
International Journal of Reliability, Quality and Safety Engineering     Hybrid Journal   (Followers: 9)
International Journal of Renewable Energy Technology     Hybrid Journal   (Followers: 10)
International Journal of Robust and Nonlinear Control     Hybrid Journal   (Followers: 3)
International Journal of Science Engineering and Advance Technology     Open Access  
International Journal of Sediment Research     Full-text available via subscription   (Followers: 2)
International Journal of Self-Propagating High-Temperature Synthesis     Hybrid Journal   (Followers: 2)
International Journal of Signal and Imaging Systems Engineering     Hybrid Journal  
International Journal of Six Sigma and Competitive Advantage     Hybrid Journal   (Followers: 1)
International Journal of Social Robotics     Hybrid Journal   (Followers: 2)
International Journal of Software Engineering and Knowledge Engineering     Hybrid Journal   (Followers: 2)
International Journal of Space Science and Engineering     Hybrid Journal   (Followers: 2)
International Journal of Speech Technology     Hybrid Journal   (Followers: 6)
International Journal of Spray and Combustion Dynamics     Full-text available via subscription   (Followers: 7)
International Journal of Surface Engineering and Interdisciplinary Materials Science     Full-text available via subscription   (Followers: 3)
International Journal of Surface Science and Engineering     Hybrid Journal   (Followers: 8)
International Journal of Sustainable Engineering     Hybrid Journal   (Followers: 7)
International Journal of Sustainable Manufacturing     Hybrid Journal   (Followers: 5)
International Journal of Systems and Service-Oriented Engineering     Full-text available via subscription  
International Journal of Systems Assurance Engineering and Management     Hybrid Journal  
International Journal of Systems, Control and Communications     Hybrid Journal   (Followers: 2)
International Journal of Technoethics     Full-text available via subscription   (Followers: 1)
International Journal of Technology Management and Sustainable Development     Hybrid Journal   (Followers: 1)
International Journal of Technology Policy and Law     Hybrid Journal   (Followers: 6)
International Journal of Telemedicine and Applications     Open Access   (Followers: 2)
International Journal of Thermal Sciences     Hybrid Journal   (Followers: 8)
International Journal of Thermodynamics     Open Access   (Followers: 4)
International Journal of Turbo & Jet-Engines     Hybrid Journal   (Followers: 2)
International Journal of Ultra Wideband Communications and Systems     Hybrid Journal  
International Journal of Vehicle Autonomous Systems     Hybrid Journal   (Followers: 1)
International Journal of Vehicle Design     Hybrid Journal   (Followers: 8)
International Journal of Vehicle Information and Communication Systems     Hybrid Journal   (Followers: 2)
International Journal of Vehicle Noise and Vibration     Hybrid Journal   (Followers: 3)
International Journal of Vehicle Safety     Hybrid Journal   (Followers: 5)
International Journal of Vehicular Technology     Open Access   (Followers: 5)
International Journal of Virtual Technology and Multimedia     Hybrid Journal   (Followers: 3)
International Journal of Wavelets, Multiresolution and Information Processing     Hybrid Journal  
International Journal on Artificial Intelligence Tools     Hybrid Journal   (Followers: 5)
International Nano Letters     Open Access   (Followers: 6)
International Review of Applied Sciences     Open Access  

  First | 2 3 4 5 6 7 8 9 | Last

Journal Cover Ionics
  [SJR: 0.497]   [H-I: 27]   [0 followers]  Follow
    
   Hybrid Journal Hybrid journal (It can contain Open Access articles)
   ISSN (Print) 1862-0760 - ISSN (Online) 0947-7047
   Published by Springer-Verlag Homepage  [2280 journals]
  • ZnO-coated LiMn 2 O 4 cathode material for lithium-ion batteries
           synthesized by a combustion method
    • Abstract: Abstract ZnO-coated LiMn2O4 cathode materials were prepared by a combustion method using glucose as fuel. The phase structures, size of particles, morphology, and electrochemical performance of pristine and ZnO-coated LiMn2O4 powders are studied in detail by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS), galvanostatic charge-discharge test, and X-ray photoelectron spectroscopy (XPS). XRD patterns indicated that surface-modified ZnO have no obvious effect on the bulk structure of the LiMn2O4. TEM and XPS proved ZnO formation on the surface of the LiMn2O4 particles. Galvanostatic charge/discharge test and rate performance showed that the ZnO coating could improve the capacity and cycling performance of LiMn2O4. The 2 wt% ZnO-coated LiMn2O4 sample exhibited an initial discharge capacity of 112.8 mAh g−1 with a capacity retention of 84.1 % after 500 cycles at 0.5 C. Besides, a good rate capability at different current densities from 0.5 to 5.0 C can be acquired. CV and EIS measurements showed that the ZnO coating effectively reduced the impacts of polarization and charge transfer resistance upon cycling.
      PubDate: 2016-02-06
       
  • NiCo 2 O 4 polyhedra with controllable particle size as high-performance
           anode for lithium-ion battery
    • Abstract: Abstract Different particle sizes of dodecahedron precursors are synthesized by controlling the polarity of the solution. Through the results of scanning electron microscope (SEM) images, it can be found that different particle sizes of precursors present obvious edge angles and their morphology can be well retained after annealing. X-ray diffraction (XRD) measurements suggest that the annealed polyhedral products are pure single-phase NiCo2O4. When tested as lithium-ion battery anode, 0.5 μm NiCo2O4 polyhedra exhibits a specific capacity of 1050 mAh g−1 at 0.1 C at the 60th cycle, which was higher than theoretical capacity of single metal oxide (NiO 718 mAh g−1 and Co3O4 890 mAh g−1). It also exhibits the highest rate capability with an average discharge capacity of 890, 700, 490, 330, and 300 mAh g−1 at 0.5, 2, 4, 8, and 10 C, respectively. Those advantages are attributed to that small-sized particle with great surface areas decrease the actual current density at the surface and inner of the prepared electrode.
      PubDate: 2016-02-01
       
  • Voltammetric behavior of bupirimate fungicide and its square wave
           voltammetric determination
    • Abstract: Abstract The voltammeric behavior of bupirimate fungicide has been studied by square wave stripping voltammetry (SWSV). The insoluble R–HgS salt (where R is the bupirimate frame excluding sulfur) formed on the static hanging mercury drop electrode (SHMDE) was electrochemically reduced by giving a fairly well defined cathodic peak within the pH range of 1.0 to 8.0. The peak potentials (E p) were shifted toward more negative values with increasing pH, and a maximum peak response appeared at −1320 mV (vs. Ag/AgCl) at a pH 6.0. The calibration plot was a straight line in the range of 0.013 to 9.43 mg L−1. The detection limit at pH 6.0 was measured as 4.0 μg L−1 under the conditions of E acc = −700 mV and t acc = 10 s. The validity of the recommended method was assessed from the recoveries of spiked tap water, natural peach juice, and commercial peach juice.
      PubDate: 2016-02-01
       
  • Porous WO 3 /reduced graphene oxide composite film with enhanced
           electrochromic properties
    • Abstract: Abstract The porous WO3/reduced graphene oxide (rGO) composite films are prepared on indium–tin oxide (ITO) glass by sol-gel method. The mixture sol combines peroxotungstic acid solution with rGO dispersion reduced by ethylene glycol (EG). The excessive EG and other organic additives are subsequently removed by annealing, which leads to the formation of porous structure. Compared with pure WO3 film, WO3/rGO composite film shows improved electrochromic performance because of enhanced double insertion/extraction of ions and electrons. It realizes a large optical modulation (64.2 % at 633 nm), fast switching speed (9.5 s for coloration and 4.5 s for bleaching), good cycling stability as well as reversibility.
      PubDate: 2016-02-01
       
  • Improved cycling performances with high sulfur loading enabled by
           pre-treating lithium anode
    • Abstract: Abstract Lithium nitrate (LiNO3) is reported as an effective additive to protect lithium anode in rechargeable lithium-sulfur battery. However, for its strong oxidation, cells containing LiNO3 still suffer from safety problems and poor cycle performance since LiNO3 can be reduced on cathode to form some irreversible products. In this study, a facile and effective method to pre-passivate lithium anode is proposed by simply immersing lithium plates in LiNO3 solution. The electrochemical properties show that the pretreatment is favorable for the construction of a protection layer on the surface of lithium anode. Cells with pretreated lithium show the coulombic efficiency of 80.6 % in the first cycle and 87.2 % after 100 cycles, far higher than the one with pure lithium. The discharge capacity is retained at 702 mA h g−1 after 100 cycles, and the result is better than those directly adding LiNO3 in electrolyte. It is believed that these improvements result from the high stability of surface film during the charge and discharge process, which can stabilize the structure of anode and suppress the shuttle effect.
      PubDate: 2016-02-01
       
  • Distinctive slit-shaped porous carbon encapsulating phosphorus as a
           promising anode material for lithium batteries
    • Abstract: Abstract A distinctive structure of carbon materials for Li-ion batteries is proposed for the preparation of red phosphorus-carbon composites. The slit-shaped porous carbon is observed with aggregation of plate-like particles, whose isotherm belongs to the H3 of type IV. The density functional theory (DFT) method reveals the presence of micro-mesopores in the 0.5–5 nm size range. The unique size distribution plays an important role in adsorbing phosphorus and electrochemical performance. The phosphorus-slit-shaped porous carbon composite shows initial capacity of 2588 mAh g−1, reversible capacity of 1359 mAh g−1 at a current density of 100 mA g−1. It shows an excellent coulombic efficiency of ∼99 % after 50 cycles.
      PubDate: 2016-02-01
       
  • Synthesis and electrochemical properties of Li 1.2 Mn 0.54 Ni 0.13 Co 0.13
           O 2 cathode material for lithium-ion battery
    • Abstract: Abstract The layered Li1.2Mn0.54Ni0.13Co0.13O2 lithium-rich manganese-based solid solution cathode material has been synthesized by a simple solid-state method. The as-prepared material has a typical layered structure with R-3m and C2/m space group. The synthesized Li1.2Mn0.54Ni0.13Co0.13O2 has an irregular shape with the size range from 200 to 500 nm, and the primary particle of Li1.2Mn0.54Ni0.13Co0.13O2 has regular sphere morphology with a diameter of 320 nm. Electrochemical performances also have been investigated. The results show that the cathode material Li1.2Mn0.54Ni0.13Co0.13O2 prepared at 900 °C for 12 h has a good electrochemical performance, which can deliver a high initial discharge capacity of 233.5, 214.2, 199.3, and 168.1 mAh g−1 at 0.1, 0.2, 0.5, and 1 C, respectively. After 50 cycles, the capacity retains 178.0, 166.3, 162.1, and 155.9 mAh g−1 at 0.1, 0.2, 0.5, and 1 C, respectively. The results indicate that the simple method has a great potential in synthesizing manganese-based cathode materials for Li-ion batteries.
      PubDate: 2016-02-01
       
  • A novel carbon source coated on C-LiFePO 4 as a cathode material for
           lithium-ion batteries
    • Abstract: Abstract The poor electronic conductivity and low lithium-ion diffusion are the two major obstacles to the largely commercial application of LiFePO4 cathode material in power batteries. In order to improve the defects of LiFePO4, a novel carbon source polyacrylonitrile (PAN), which would form the hierarchical porous structure after carbonization, is fabricated and used. This work comes up with a simple and facile carbothermal reduction method to prepare porous-carbon-coated LiFePO4 (C-LiFePO4-PC) composite and to study the effect of carbon-coated temperature on ameliorating the electrochemical performance. The obtained C-LiFePO4-PC composite shows a high initial discharge capacity of 164.1 mA h g−1 at 0.1 C and good cycling stability as well as excellent rate capacity (49.0 mA h g−1 at 50 C). The most possible factors that improve the electrochemical performance could be related to the enhancement of electronic conductivity and the existence of porous carbon layers. In a word, the C-LiFePO4-PC material would become an excellent candidate for application in the fields of lithium-ion batteries.
      PubDate: 2016-02-01
       
  • Conductivity behavior of the new pyrophosphate NaNi 1.5 P 2 O 7
    • Abstract: Abstract NaNi1.5P2O7 compound was obtained by the classic ceramic method at high temperature and was characterized by XRD. It was found to crystallize in the triclinic symmetry with the P-1 space group. The electrical conductivity and modulus characteristics of the system have been investigated in the temperature and the frequency range 586–723 K and 200 Hz–1 MHz, respectively, by means of impedance spectroscopy. The ac conductivity for grain contribution was interpreted using the universal Jonscher’s power law. The exponent s decreased with increasing temperature revealing that the conduction inside the studied material is insured by the correlated barrier hopping (CBH) model. The conduction mechanism was explained with the help of Elliot’s theory, and the Elliot’s parameters were determined. Thermodynamic parameters such as the free energy for dipole relaxation ΔG, the enthalpy ΔH, and the change in entropy ΔS have been calculated.
      PubDate: 2016-02-01
       
  • Synthesis and characterization of spinel LiMn 2 O 4 nanoparticles prepared
           by high-energy milling and hydrothermal method
    • Abstract: Abstract Spinel LiMn2O4 has been known to be a technologically important, environmental-friendly, and low-cost cathode material used in Li-based rechargeable batteries, and it is also widely available. Nanoparticle spinel LiMn2O4 has been synthesized by the top-down, high-energy milling, and hydrothermal methods. SEM images, X-ray diffraction patterns, and neutron high-resolution powder diffraction patterns have confirmed the nanocrystalline nature of the spinel LiMn2O4 samples. Raman and Fourier transform infrared (FTIR) measurements show typical absorption and vibration spectra typical for the spinel LiMn2O4 showing the formation of various metallic bonds in the sample. The strongest Raman and FTIR signals come from the higher frequency region, with weaker signals appearing in the lower frequency range.
      PubDate: 2016-02-01
       
  • Hierarchical LiMn 0.5 Fe 0.5 PO 4 /C nanorods with excellent
           electrochemical performance synthesized by rheological phase method as
           cathode for lithium ion battery
    • Abstract: Abstract The hierarchical LiMn0.5Fe0.5PO4/C (LMFP) nanorods were first successfully synthesized by rheological phase method using polyethylene glycol 4000 (PEG 4000) as a template reagent. The physical and electrochemical properties of the LiMn0.5Fe0.5PO4/C were characterized by TG-DTG, XRD, FTIR, SEM, TEM, EIS and galvanostatic charge-discharge measurements. The results reveal that the PEG-LMFP/C synthesized with the assistance of PEG 4000 shows unique bundle-type shape assembled of nanorods, while the LMFP/C synthesized without PEG 4000 presents a platelet-like shape with some agglomeration. Besides, a uniformly carbon layer coating on the surface of the PEG-LMFP/C can be seen from TEM images. The PEG-LMFP/C exhibits high specific capacity and superior rate performance with discharge capacities of 162, 133, 108, 95, and 78 mAh · g−1 at 0.1, 1, 5, 10, and 20 C rates, respectively. It is demonstrated that the synthesis of LMFP/C with PEG 4000 can significantly decrease the characteristic sizes of the crystals, resulting in improved electrochemical performance.
      PubDate: 2016-02-01
       
  • A study of the capacity fade of porous NiO/Ni foam as negative electrode
           for lithium-ion batteries
    • Abstract: Abstract High energy density materials such as NiO that undergoes conversion reaction hold promise for lithium (Li)-ion batteries (LIBs). However, porous NiO experiences substantial volume change due to the diffusion-induced stress during electrochemical operation, which causes mechanical fractures and morphological changes of porous NiO electrodes, leading to capacity fade through internal short circuit (ISCr). In this study, both non-destructive and destructive operations were used to visualize and quantify the origins and evolutions of the capacity fading of porous NiO/Ni foam electrodes. Results indicated that charge transfer resistance was dominant among all the internal resistances before ISCr, whereas solid electrolyte interface (SEI) resistance was dominant after ISCr of LIBs. The generation of the large amount of heat and pressure during ISCr caused the volume expansion and the formation of the micro-cracks in the struts of the porous NiO/Ni foam electrodes. Together with the electrolyte decomposition, this led to capacity fade. The results of this study provide insights for developing of NiO/Ni electrode for LIBs.
      PubDate: 2016-02-01
       
  • The physical and electrochemical properties of poly(vinylidene
           chloride-co-acrylonitrile)-based polymer electrolytes prepared with
           different plasticizers
    • Abstract: Abstract Lithium ion-conducting membranes with poly(ethylene oxide) (PEO)/poly(vinylidene chloride-co-acrylonitrile) (PVdC-co-AN)/lithium perchlorate (LiClO4) were prepared by solution casting method. Different plasticizers ethylene carbonate (EC), propylene carbonate (PC), gamma butyrolactone (gBL), diethyl carbonate (DEC), dimethyl carbonate (DMC), and dibutyl phthalate (DBP) were complexed with the fixed ratio of PEO/PVdC-co-AN/LiClO4. The preparation and physical and electrochemical properties of the gel polymer electrolytes have been briefly elucidated in this paper. The maximum ionic conductivity value computed from the ac impedance spectroscopy is found to be 3 × 10−4 S cm−1 for the EC-based system. From DBP-based system down to EC-based system, a decrease of crystallinity and an increase of amorphousity are depicted by X-ray diffraction technique, the decrease of band gap energy is picturized through UV–visible analysis, the decrease of glass transition temperature is perceived from differential scanning calorimetry plots, and the reduction of photoluminescence intensity is described through photoluminescence spectroscopy study at an excitation wavelength of 280 nm. Atomic force microscopic images of EC-based polymer electrolyte film show the escalation of micropores. Fourier transform infrared spectroscopy study supports the complex formation and the interaction between the polymers, salt, and plasticizer. The maximum thermal stability is obtained from thermogravimetry/differential thermal analysis, which is found to be 222 °C for the sample complexed with EC. The cyclic voltagram of the sample having a maximum ionic conductivity shows a small redox current at the anode, and cathode and the chemical stability is confirmed by linear sweep voltammetry.
      PubDate: 2016-02-01
       
  • Simultaneous determination of amlodipine besylate and rosuvastatin calcium
           in binary mixtures by voltammetric and chromatographic techniques
    • Abstract: Abstract Voltammetric and liquid chromatographic (LC) methods have been developed for the simultaneous determination of amlodipine besylate (AML) and rosuvastatin calcium (ROS) for the first time. Detailed electrochemical behavior and simultaneous voltammetric determination of AML and ROS were investigated in detail using glassy carbon electrode (GCE). High-performance liquid chromatography (HPLC) and ultra-performance liquid chromatography (UPLC) were also developed for the comparison. Voltammetric method exhibited linear dynamic responses for the simultaneous assay of AML and ROS in the concentration range between 0.006 and 2.85 μg/mL and between 0.01 and 5.00 μg/mL, with detection limits of 0.001 and 0.003 μg/mL, respectively. On the other hand, LC methods presented a wider linearity range than that of the SWV method between 0.5 and 100 μg/mL with the detection limits of 0.011 and 0.027 μg/mL for AML and 0.034 and 0.042 μg/mL for ROS by UPLC and HPLC techniques, respectively.
      PubDate: 2016-02-01
       
  • Conductivity enhancement in carbonate-based composite electrolytes: an
           ongoing illusion
    • Abstract: Abstract The recently claimed conductivity enhancement in alkali carbonate-based composite electrolytes and the conductivity enhancement ascribed to heterogeneous-phase mixtures of solid alkali carbonates are unreasonable and violate established knowledge.
      PubDate: 2016-02-01
       
  • Vinyl ethylene carbonate as an electrolyte additive for high-voltage LiNi
           0.4 Mn 0.4 Co 0.2 O 2 /graphite Li-ion batteries
    • Abstract: Abstract Vinyl ethylene carbonate (VEC) is investigated as an electrolyte additive to improve the electrochemical performance of LiNi0.4Mn0.4Co0.2O2/graphite lithium-ion battery at higher voltage operation (3.0–4.5 V) than the conventional voltage (3.0–4.25 V). In the voltage range of 3.0–4.5 V, it is shown that the performances of the cells with VEC-containing electrolyte are greatly improved than the cells without additive. With 2.0 wt.% VEC addition in the electrolyte, the capacity retention of the cell is increased from 62.5 to 74.5 % after 300 cycles. The effects of VEC on the cell performance are investigated by cyclic voltammetry(CV), electrochemical impedance spectroscopy(EIS), x-ray powder diffraction (XRD), energy dispersive x-ray spectrometry (EDS), scanning electron microscopy (SEM), and attenuated total reflectance-Fourier transform infrared (ATR-FTIR). The results show that the films electrochemically formed on both anode and cathode, derived from the in situ decomposition of VEC at the initial charge–discharge cycles, are the main reasons for the improved cell performance.
      PubDate: 2016-02-01
       
  • Preparation and application of a simple electrochemical sensor for the
           determination of copper in some real and standard samples
    • Abstract: In this study, anodic stripping voltammetry was optimized and used for the trace determination of copper ions using modified carbon paste electrode with dicyclohexyl-18-crown-6 and multi-walled carbon nanotubes. The important and critical parameters such as pH, electrolyte type, electrode composition, deposition time, and reduction potential was studied and optimized. Copper shows a sharp peak at +0.095 V that was used for its determination from 4.0 to 200 ng mL−1. With the application of the suggested method, the detection limit and relative standard deviation were obtained as 1.1 ng mL−1 and ±2.3 %, respectively. This electrochemical sensor has several advantages such as simple and low cost preparation, good reproducibility, low LOD, and high speed. The suggested sensor was applied successfully for the determination of copper ions in environmental, biological, and standard samples. Graphical abstract The complex formation of copper ion with dicyclohexyl-18-crown-6 at the surface of modified carbon paste electrode
      PubDate: 2016-02-01
       
  • Ionic-protonic conduction analysis and dielectric relaxation behavior of
           the rubidium ammonium arsenate tellurate
    • Abstract: Abstract The rubidium ammonium arsenate tellurate Rb2.42(NH4)0.58H2AsO4HAsO4.Te(OH)6 compound was obtained by slow evaporation at room temperature. The differential scanning calorimetry (DSC) has shown three phase transitions at 453, 483, and 491 K, confirmed by the differential thermal analysis (D.T.A). As for the differential thermogravimetric analysis (TG) curve, it has revealed that no mass loss was detected before 475 K. So, the phase transition observed at 453 K does not correspond to the decomposition of this material. Rb2.42(NH4)0.58H2AsO4HAsO4.Te(OH)6 was characterized by impedance spectroscopy technique measured in the 1 KHz–9.91 MHz frequency range from 298 to 483 K. Besides, the cole-cole (z” versus z’) plots were well fitted to an equivalent circuit built up by a parallel combination of resistance (R), fractal capacitance (CPE), and Warburg element (W). Furthermore, the conductivity evolution versus temperature has shown the presence of the ionic-protonic superconduction phase transition. The dielectric properties’ dependence on both temperature and frequencies of the compound has been reported. The ionic-protonic conductivity and conductivity relaxation calculated from the impedance and modulus spectra, respectively, were found to be thermally activated.
      PubDate: 2016-02-01
       
  • TiO 2 modified carbon paste sensor for voltammetric analysis and
           
    • Abstract: Abstract A new square wave adsorptive stripping voltammetric (SWAdSV) approach using experimental design and optimization methodology was developed for the quantitative estimation of amlodipine (AMP) in pharmaceutical tablets. To this end, a new carbon paste electrode (CPE) system was fabricated using titanium dioxide (TiO2) nanoparticles to get very well-defined oxidation peak current of AMP under the optimized conditions. Optimal electrochemical conditions for three factor variables, the pH, the accumulation potential, and the accumulation time, were obtained by applying a 33 full factorial design and optimization technique to the oxidation of AMP on the TiO2 modified CPE (TiO2-CPE) system. The numerical values of the optimal voltammetric parameters consisting of the pH, accumulation potential, and accumulation time were found to be 5.69, 562.30 mV, and 64.30 s for the analysis of AMP in samples, respectively. The newly developed voltammetric method for the determination of AMP offers a linear relationship between the peak current and concentration in the range of 1.0 × 10−8 − 1.0 × 10−6 M with the correlation coefficient (r = 0.9990) and the detection limit (LOD = 2.97 × 10−9 M). The lifetime of prepared electrode was also tested, and the current intensity of AMP was nearly stable at least 2 months by using TiO2-CPE. The validity of the method was tested by analyzing standard samples containing the analyzed compound. Under optimized and validated experimental conditions, the proposed method was successfully applied for the quantitative analysis of AMP in commercial tablets.
      PubDate: 2016-01-30
       
  • Influence of K 2 Ti 6 O 13 on dielectric and barrier properties of polymer
    • Abstract: Abstract Polymer composite comprising polyvinylidene fluoride (PVDF) and potassium hexatitante (K2Ti6O13) was synthesized by solution casting. The effect of K2Ti6O13 on surface, thermal, and electrical properties of polymer composite were investigated. The addition of K2Ti6O13 with polymer leads to thermal degradation and transition of polymer composite from semi-crystalline to amorphous phase. The optimum results of contact angle for different loading wt% of K2Ti6O13 were directly correlated with the surface morphology. Our experimental results confirmed the incorporation of K2Ti6O13 in polymer by SEM micrographs. The evaluated dielectric properties (ε' = 424; tan δ = 2.14 at 130 °C and 100 Hz frequency for 20 wt% loading of K2Ti6O13) for polymer composite are higher in compared to pure polymer. The enhancement in dielectric constant and changing the surface properties of polymer composite can be used for the development of electrochemical storage device applications.
      PubDate: 2016-01-29
       
 
 
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