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ENGINEERING (1142 journals)            First | 2 3 4 5 6 7 8 9 | Last

International Journal of Innovation Science     Full-text available via subscription   (Followers: 6)
International Journal of Integrated Engineering     Open Access   (Followers: 1)
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  
International Journal of Machine Tools and Manufacture     Hybrid Journal   (Followers: 4)
International Journal of Manufacturing Research     Hybrid Journal   (Followers: 5)
International Journal of Manufacturing Technology and Management     Hybrid Journal   (Followers: 7)
International Journal of Materials and Product Technology     Hybrid Journal   (Followers: 4)
International Journal of Mathematical Education in Science and Technology     Hybrid Journal   (Followers: 7)
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: 4)
International Journal of Microwave and Wireless Technologies     Hybrid Journal   (Followers: 1)
International Journal of Microwave Science and Technology     Open Access   (Followers: 2)
International Journal of Mobile Network Design and Innovation     Hybrid Journal   (Followers: 3)
International Journal of Multiphase Flow     Hybrid Journal   (Followers: 2)
International Journal of Nanomanufacturing     Hybrid Journal   (Followers: 1)
International Journal of Nanoscience     Hybrid Journal   (Followers: 1)
International Journal of Nanotechnology     Hybrid Journal   (Followers: 5)
International Journal of Nanotechnology and Molecular Computation     Full-text available via subscription   (Followers: 3)
International Journal of Navigation and Observation     Open Access   (Followers: 6)
International Journal of Network Management     Hybrid Journal  
International Journal of Nonlinear Sciences and Numerical Simulation     Full-text available via subscription  
International Journal of Numerical Methods for Heat & Fluid Flow     Hybrid Journal   (Followers: 7)
International Journal of Optics     Open Access   (Followers: 1)
International Journal of Organisational Design and Engineering     Hybrid Journal   (Followers: 9)
International Journal of Pattern Recognition and Artificial Intelligence     Hybrid Journal   (Followers: 6)
International Journal of Pavement Engineering     Hybrid Journal   (Followers: 2)
International Journal of Physical Modelling in Geotechnics     Hybrid Journal   (Followers: 3)
International Journal of Plasticity     Hybrid Journal   (Followers: 6)
International Journal of Plastics Technology     Hybrid Journal  
International Journal of Polymer Analysis and Characterization     Hybrid Journal   (Followers: 5)
International Journal of Polymer Science     Open Access   (Followers: 16)
International Journal of Precision Engineering and Manufacturing     Hybrid Journal   (Followers: 5)
International Journal of Precision Technology     Hybrid Journal  
International Journal of Pressure Vessels and Piping     Hybrid Journal   (Followers: 3)
International Journal of Production Economics     Hybrid Journal   (Followers: 13)
International Journal of Quality and Innovation     Hybrid Journal   (Followers: 4)
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: 1)
International Journal of Reliability, Quality and Safety Engineering     Hybrid Journal   (Followers: 6)
International Journal of Renewable Energy Technology     Hybrid Journal   (Followers: 8)
International Journal of Robust and Nonlinear Control     Hybrid Journal   (Followers: 2)
International Journal of Science Engineering and Advance Technology     Open Access  
International Journal of Sediment Research     Full-text available via subscription   (Followers: 1)
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  
International Journal of Social Robotics     Hybrid Journal   (Followers: 1)
International Journal of Software Engineering and Knowledge Engineering     Hybrid Journal   (Followers: 1)
International Journal of Space Science and Engineering     Hybrid Journal   (Followers: 2)
International Journal of Speech Technology     Hybrid Journal   (Followers: 4)
International Journal of Spray and Combustion Dynamics     Full-text available via subscription   (Followers: 6)
International Journal of Surface Engineering and Interdisciplinary Materials Science     Full-text available via subscription   (Followers: 1)
International Journal of Surface Science and Engineering     Hybrid Journal   (Followers: 7)
International Journal of Sustainable Engineering     Hybrid Journal   (Followers: 7)
International Journal of Sustainable Manufacturing     Hybrid Journal   (Followers: 4)
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  
International Journal of Technology Management and Sustainable Development     Hybrid Journal   (Followers: 1)
International Journal of Technology Policy and Law     Hybrid Journal   (Followers: 4)
International Journal of Telemedicine and Applications     Open Access   (Followers: 2)
International Journal of Thermal Sciences     Hybrid Journal   (Followers: 7)
International Journal of Thermodynamics     Open Access   (Followers: 2)
International Journal of Turbo & Jet-Engines     Full-text available via subscription  
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: 6)
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: 2)
International Journal of Virtual Technology and Multimedia     Hybrid Journal   (Followers: 4)
International Journal of Wavelets, Multiresolution and Information Processing     Hybrid Journal  
International Journal on Artificial Intelligence Tools     Hybrid Journal   (Followers: 4)
International Nano Letters     Open Access   (Followers: 9)
International Review of Applied Sciences and Engineering     Full-text available via subscription  
Inverse Problems in Science and Engineering     Hybrid Journal   (Followers: 2)
Ionics     Hybrid Journal  
IPTEK The Journal for Technology and Science     Open Access  
IRBM News     Full-text available via subscription  
Irrigation and Drainage Systems     Hybrid Journal  
ISA Transactions     Full-text available via subscription   (Followers: 1)
ISRN - International Scholarly Research Notices     Open Access   (Followers: 68)
ISRN Nanotechnology     Open Access  
ISRN Signal Processing     Open Access  
ISRN Thermodynamics     Open Access  
IT Professional     Full-text available via subscription   (Followers: 3)
Journal of Biosensors & Bioelectronics     Open Access   (Followers: 2)
Journal of Advanced Manufacturing Systems     Hybrid Journal   (Followers: 6)
Journal of Aerosol Science     Hybrid Journal   (Followers: 1)
Journal of Aerospace Engineering     Full-text available via subscription   (Followers: 187)
Journal of Alloys and Compounds     Hybrid Journal   (Followers: 8)
Journal of Analytical and Applied Pyrolysis     Hybrid Journal   (Followers: 3)
Journal of Analytical Science & Technology     Open Access   (Followers: 4)

  First | 2 3 4 5 6 7 8 9 | Last

Journal Cover Ionics     [SJR: 0.522]   [H-I: 25]
   Hybrid Journal Hybrid journal (It can contain Open Access articles)
   ISSN (Print) 1862-0760 - ISSN (Online) 0947-7047
   Published by Springer-Verlag Homepage  [2210 journals]
  • Electrochemical properties of a poly(ethylene carbonate)-LiTFSI
           electrolyte containing a pyrrolidinium-based ionic liquid
    • Abstract: A novel polymer electrolyte membrane comprising poly(ethylene carbonate) (PEC), lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) salt, and N-n-butyl-N-methylpyrrolidinium bis(trifluoromethanesulfonyl)imide (Pyr14TFSI) ionic liquid is prepared by a solvent-free procedure, combining annealing and hot-pressing. The electrochemical properties of the electrolyte are investigated in terms of ionic conductivity, Li transference number (t Li+), and electrochemical stability by a combined study involving electrochemical impedance spectroscopy (EIS), chronoamperometry, and voltammetry. The thermal characteristics are assessed by differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA). The results reveal an ionic conductivity of a PEC-Pyr14TFSI-LiTFSI electrolyte of the order of 10−5 S cm−1 at 80 °C and t Li+ as high as 0.66 with the intrinsic amorphous nature of the PEC matrix. Furthermore, a Li polymer cell coupling LiFePO4 cathode and the electrolyte is assembled and galvanostatically cycled. The result of this charge-discharge test demonstrates a 3.5-V battery which can be used at 80 °C and a current rate of C/20, delivering a reversible capacity of the order of 150 mAh g−1.
      PubDate: 2015-01-24
  • Investigation into the actuating properties of ionic polymer metal
           composites using various electrolytes
    • Abstract: With an increasing trend of ionic polymer metal composites (IPMC) applied in marine system surrounding with abundant K+ and Na+ ions, efforts of IPMC with different electrolytes on actuating properties were investigated. In this paper, different IPMC were prepared using Li+, Na+, and K+ as the electrolyte cations and water, ionic liquid, and ethylene glycol as the electrolyte solvent. Actuating parameters were measured based on a customized experimental setup under dynamic voltage and dynamic frequency. Results showed that electrolyte solvent can affect the working life cycle and displacement of IPMC under dynamic voltage and frequency signal, whereas the electrolyte cations can only influence the actuating properties under dynamic voltage. An initial increase in the strain rate of all IPMC samples was discovered following a decrease. Furthermore, it is visible from the results analysis that each group of IPMC had a constant solvent absorption content, although they obtained different contents of electrolyte solvent and cations. Moreover, a principle was observed in the voltage tolerance of IPMC with Li+, Na+, and K+ as increasing atomic weigh of electrolyte cations. In addition, a relationship between actuating properties and electrolytes was illuminated in this paper.
      PubDate: 2015-01-24
  • Influence of carbon content, particle size, and partial manganese
           substitution on the electrochemical performance of LiFe x Mn 1-x PO 4
           /carbon composites
    • Abstract: LiFePO4/C and LiFexMn1-xPO4/C (x = 0.7) nanocomposites were successfully synthesized via scalable spray-flame synthesis followed by solid-state reaction. A solution of iron (III) acetylacetonate and tributyl phosphate in toluene was used to produce amorphous, nanosized FePO4⋅H2O in a spray-flame reactor which was then milled with Li2CO3 and glucose to produce a LiFePO4/C composite material in a solid-state reaction. The influence of calcination temperature and carbon content on the properties of the resulting material was investigated using specific surface area measurements (BET), X-ray diffraction (XRD), electron microscopy, and electrochemical characterization. The impact of manganese addition on the electrochemical behavior was analyzed using cyclic voltammetry (CV) and constant-current (CC) measurements. XRD shows that the combination of gas-phase synthesis and subsequent solid-state reaction yields highly pure LiFePO4/C. BET measurement revealed that the particle size of LiFePO4 in the composite depends on the amount of glucose. A discharge capacity of more than 140 mAh/g at C/20 is achieved for LiFePO4/C with a carbon content of 6 wt%. This material supports high charge as well as discharge rates delivering more than 60 mAh/g at 16 C and sustains good cycle stability providing 115 mAh/g at 1 C. The energy density of the olivine increases about 10 % by substituting 30 mol% of iron by manganese while preserving the electrochemical performance of pure LiFePO4/C.
      PubDate: 2015-01-24
  • Studies of electric, dielectric, and conduction mechanism by OLPT model of
           Li 4 P 2 O 7
    • Abstract: The polycrystalline samples of Li4P2O7 were prepared by solid-state reaction technique. The formation of the compounds was checked by X-ray diffraction technique (XRD). Detailed dielectric and electrical properties of the compounds were analyzed as a function of frequency (200 Hz–5 MHz) and temperature (611–671 K). The impedance data were well fitted to two equivalent electrical circuits. The results of the modulus study reveal the presence of two distinct relaxation processes suggesting the presence of grains and grain boundaries in the sample. Analysis of the dielectric constants ε″ and loss tangent tan (δ) with frequency shows a distribution of relaxation times. The activation energy found from the Arrhenius plot confirms that the conduction process in the material is not due to simple hopping mechanism. The temperature dependence of frequency exponent s was investigated to understand the conduction mechanism in Li4P2O7. The overlapping large polaron tunneling (OLPT) model can explain the temperature dependence of the frequency exponent.
      PubDate: 2015-01-22
  • Optimization of ionic conductivity of electrospun polyacrylonitrile/poly
           (vinylidene fluoride) (PAN/PVdF) electrolyte using the response surface
           method (RSM)
    • Abstract: Polyacrylonitrile/poly (vinylidene fluoride) fibrous membranes were prepared by electrospinning of PAN and PVdF solution and were soaked in 1 M lithium perchlorate (LiClO4) in ethylene carbonate (EC)/diethyle carbonate (DEC) (1:1 wt.%) solution in order to prepare polymer electrolyte membranes. Response surface method (RSM) was used to obtain a quantitative relationship between selected electrospinning parameters, i.e., applied voltage, solution concentration, and PVdF content. The measured response is ionic conductivity of electrolyte membranes. The Box–Behnken method was applied to design of experiments. Importance of parameters in the model was determined by analysis of variance (ANOVA). The model was used to find the maximum ionic conductivity of electrolyte membranes as optimum result. The morphology of fibers was investigated by field emission scanning electron microscopy (FESEM). FESEM results show that the PAN/PVdF membrane has interconnected multifibrous layers with ultrafine porous structure that leads to a high ionic conductivity and efficient lithium ion transport. Produced fibrious membranes show uniform morphology. Average fiber diameter lies between 116 and 379 nm, and membranes have high porosity of 48–90 % and electrolyte uptake of 303–493 %. The polymer electrolyte membranes show good ionic conductivity in the order of 10−3 S cm−1 at ambient temperature. Ionic conductivity decreases with increase of solution concentration and increases with increase of PVdF composition. Voltage has no significant effect on ionic conductivity of the membranes. The model predicted the maximum ionic conductivity of 7.98 mS cm−1 when the voltage was set at 21.57 kV, the solution concentration set at 14.02 wt.%, and the PVdF composition set at 69.48 wt.%.
      PubDate: 2015-01-21
  • Synthesis, characterization and analytical application of cellulose
           acetate-tin (IV) molybdate nanocomposite ion exchanger: binary separation
           of heavy metal ions and antimicrobial activity
    • Abstract: A novel cellulose acetate-tin (VI) molybdate nanocomposite (CA/TMNC) exchanger was synthesized by sol-gel method and characterized using techniques such as Fourier transform infrared spectroscopy, scanning electron microscopy, transmission electron microscopy, X-ray diffraction, and thermal analysis. Transmission electron microscopy (TEM) results indicated the formation of particles of nanodimensions. The ion exchange capacity, pH titration, elution behavior, and distribution coefficient were also investigated. CA/TMNC showed enhanced ion exchange capacity as compared to its inorganic counterpart. The distribution coefficient (K d ) values for different toxic heavy metal ion such as Pb+2, Cd+2, Mg+2, Zn+2, Co+2, Cu+2, Mn+2, Cr+3, Ni+2, and Fe+2 has been studied in double-distilled water by batch process. On the basis of K d values, four binary separation of the metal ions have been achieved on the column of CA/TMNC. The material is found to be selective for Pb2+ and Cd2+ ions; about more than 94 % of Pb2+ and 93 % of Cd2+ ions were recovered in each separation. The antibacterial activity of CA/TMNC was explored against Escherichia coli. The results confirmed the bacteriostatic nature of the CA/TMNC.
      PubDate: 2015-01-21
  • High-efficiency PdCu alloy nanocube catalyst supported on N-doped
           multiwalled carbon nanotubes for alcohol electrooxidation
    • Abstract: N-doped of the support is generally important to immobilize metal nanoparticles on the support, produce some active Me–N sites, and generate good electrocatalytic activity and stability. A facile and low-cost preparation of N-doped multiwalled carbon nanotube (N-MWCNTs)-supported hollow PdCu alloyed nanocube catalyst (H–PdCu/N-MWCNTs) was introduced in this paper. To increase the stability and utilization ratio of the noble metal, a two-step strategy was employed, which included the synthesis of N-MWCNTs using polypyrrole (ppy) as the source of nitrogen and the preparation of the hollow PdCu alloyed nanocubes. According to transmission electron microscopy (TEM) measurements, the as-prepared hollow PdCu alloyed nanocube catalyst has superior dispersibility, and the average diameter is about 50 nm. X-ray photoelectron spectroscopy (XPS) measurements reveal that N atoms have been doped in multiwalled carbon nanotubes (MWCNTs) and there is abundance of pyridinic N and graphitic N species on N-MWCNT surface. The electrochemical measurements indicate that the hollow PdCu alloyed nanocube catalyst has a better electrocatalytic activity and stability for the alcohol oxidation. It is concluded that the H–PdCu/N-MWCNTs would be a potential candidate as an anode electrocatalyst in direct alcohol fuel cell.
      PubDate: 2015-01-16
  • Graphene/TiO 2 /polyaniline nanocomposite based sensor for the
           electrochemical investigation of aripiprazole in pharmaceutical
    • Abstract: A highly sensitive and selective sensor is fabricated based on graphene/titanium dioxide/polyaniline modified glassy carbon electrode (GRP/TiO2/PANI/GCE). It is demonstrated that this sensor can be used for determination of a pharmaceutically important compound aripiprazole (ARP) using square wave voltammetry and cyclic voltammetry (SWV & CV). Scanning electron microscope (SEM) was used to investigate the assembly process of the nanocomposite modifier. The electrochemical investigation of ARP at (GRP/TiO2/PANI/GCE) was found to be the function of pH of the supporting electrolyte, and variation in scan rate and concentration. Electro-oxidation of ARP showed irreversible and adsorption-controlled behaviour at GRP/TiO2/PANI/GCE. Charge transfer coefficient and number of electrons and protons involved in the electrode mechanism were calculated. SWV of different concentrations of ARP showed a linear dynamic range from 5 to 40 ng/mL with the detection limit of 0.99 ng/mL. The analytical performance of this sensor has been evaluated for the detection of ARP in pharmaceutical formulation with satisfactory results.
      PubDate: 2015-01-14
  • Surface modification of Mg-doped spinel with different Li-containing
           manganese oxides
    • Abstract: Mg-doped spinel LiMg0.05Mn1.95O4 was synthesized and coated with three types of Li-containing manganese oxides (Li2Mn4O9, Li4Mn5O12, and LiNi0.5Mn1.5O4) to improve the cycling properties at room temperature and at 50 °C via a coprecipitation method. The as-prepared spinels were characterized by X-ray diffraction (XRD), scanning electron microscope (SEM), inductively coupled plasma (ICP), and electrochemical tests. The results indicate that all the coated samples show enhanced electrochemical performance including higher initial charge-discharge capacities and more stable cycling properties as well as improved coulombic efficiency. Especially, the LiNi0.5Mn1.5O4-coated sample delivers the highest initial discharge capacity of 129 mAh/g with capacity retention of 82.5 % as well as the best coulombic efficiency of 92.1 %. This improved performance could be attributed to the enhanced electrochemical kinetics by successful surface modification of spinels with Li-containing manganese oxides via coprecipitation method.
      PubDate: 2015-01-14
  • AC conductivity and dielectric behavior of high-temperature form of copper
           silver phosphate
    • Abstract: The high-temperature form of AgCuPO4 (i.e., β-AgCuPO4) was obtained by conventional solid-state reaction. The sample was characterized by X-ray powder diffraction, Raman, and electrical impedance spectroscopy. Electrical properties were investigated using impedance measurements in the frequency range from 209 Hz to 1 MHz and the temperature range 603 to 719 K. Z′ and Z″ versus frequency plots were well fitted to an equivalent circuit model. It was found that the data of the ac measurements follow the correlated barrier hopping (CBH) model and the model’s parameters were determined.
      PubDate: 2015-01-13
  • Enhancement of the electrochemical performance of LiFePO 4 /carbon
           nanotubes composite electrode for Li-ion batteries
    • Abstract: LiFePO4 is very good potential cathode materials for the power lithium-ion batteries because of its high theoretical capacity and high voltage, but its electrochemical performance suffers from the low electronic conductivity. In this paper, the multi-walled carbon nanotubes (MWCNTs)/LiFePO4 composites cathode materials are prepared by ball milling. With high conductivity and the network structure existing in the LiFePO4 electrode, carbon nanotubes can reduce internal resistance and increase practical capacity and cycle stability of LiFePO4. As electrodes of lithium battery, the charge–discharge capacity, cyclic voltammetry, cycle life, alternating current impedance, and discharge temperatures characteristic of LiFePO4/MWCNTs (the loading of MWCNTs from 0 to 20 %) are investigated. The resistances of LiFePO4/MWCNTs decrease with the increase of MWCNTs loading and reach a minimal value of 56 Ω in the 10 % loading of MWCNTs, and result in the improvement of electrochemical performance. It is found that the composite electrode with 10 % loading of MWCNTs exhibits a best charge–discharge performance, and has initial charge capacities of 148 mAhg−1 and discharge capacities of 145 mAhg−1, respectively at 0.1 °C rate and the capacity retention is 98 %. The result of the pure LiFePO4 shows that the discharge capacity is 131 mAhg−1 at the rate of 0.5 °C, which means the increase in capacity of the LiFePO4/MWCNTs electrode achieves 16 %. The LiFePO4/MWCNTs composites also have perfectly high temperature performance due to the excellent thermal stability of the MWCNTs, and the discharge capacity of the composite electrode is 164 mAhg−1 at 0.1 °C rate in the temperature of 60 °C. After 30 cycles, the capacity still maintains as 163 mAhg−1 and the capacity retention is 99 %. The excellent cycle performance of the LiFePO4/MWCNTs electrode may attribute to the netlike-structure mechanical and electrical performance of MWCNTs.
      PubDate: 2015-01-11
  • Electric double-layer capacitors with corn starch-based biopolymer
           electrolytes incorporating silica as filler
    • Abstract: Solid-state electric double-layer capacitors (EDLCs) based on corn starch biodegradable polymer electrolytes are fabricated. Silica is added into the corn starch polymer electrolytes to improve the ionic conductivity and capacitance of the EDLCs. The ionic conductivity as a function of temperature obeys the Arrhenius equation indicating ionic hopping mechanism in the polymer electrolytes. Linear sweep voltammetry shows that the prepared corn starch-based biopolymer electrolyte is stable in the range from −2.5 to 2.5 V. Electrical capacitance performances of these capacitors are studied by cyclic voltammetry, galvanostatic charge–discharge, and AC impedance spectroscopy. The discharge characteristics have been found to be almost linear, which confirms the capacitive behavior of the EDLC cell. The fabricated EDLC cells perform good cyclability up to 500 cycles with more than 90 % of coulombic efficiency.
      PubDate: 2015-01-10
  • Hierarchical porous carbons fabricated from silica via flame synthesis as
           anode materials for high-performance lithium-ion batteries
    • Abstract: A convenient and cost-effective flame approach to produce a silica template with a unique structure was proposed. The hierarchical porous carbon materials (PCMs) fabricated employing presently prepared silica provide a high specific surface area for the diffusion of Li ions and transportation of electrons. Analysis of nitrogen absorption-desorption and pore size distribution (PSD) shows that PCMs possess plenty of micropores, mesopores, and macropores. Benefiting from the cooperation of various-sized pores, the PCMs-700 as anode material for lithium-ion batteries (LIBs) exhibits outstanding reversible capacities of 1332 mAh g−1 at current density of 37.2 mA g−1 (0.1 C) and 834 mAh g−1 at 372 mA g−1 (1 C). And when the current density is increased to 3.72 A g−1 (10 C), it could still retain reversible capacity of 430 mAh g−1. This result suggests that the hierarchical porous carbon material would be a promising anode material in the LIBs.
      PubDate: 2015-01-10
  • Sulfonated graphene oxide with improved ionic performances
    • Abstract: Graphene oxide is well known as a new kind of functional materials because of its super-high specie surface area, mechanical strength, as well as excellent amphipathicity. In this article, graphene oxide was further sulfonated via substitution reaction with diazo salt of sulfanilic in order to endow graphene oxide with better ion exchange capacity and proton conductivity. The microstructure and morphology of the obtained sulfonated graphene oxide were characterized by X-ray diffraction (XRD), Raman spectra, and TEM, while the sulfonation of graphene oxide was confirmed by energy-dispersive X-ray (EDX) and Fourier transform infrared spectroscopy (FTIR) spectra. As expected, ion exchange capacity and proton conductivity of sulfonated graphene oxide increased by about 0.589 and 33.6 times than those of graphene oxide, respectively.
      PubDate: 2015-01-10
  • Carbon nanotube electrochemical sensor based on and benzofuran derivative
           as a mediator for the determination of levodopa, acetaminophen, and
    • Abstract: In this research, a (7,8-dihydroxy-3,3,6-trimethyl-3,4-dihydrodibenzo[b,d]furan-1(2H)-one] (DTDF) multi-walled carbon nanotube modified carbon paste electrode was constructed and used as an excellent electrocatalyst in the oxidation of levodopa (LD) in the presence of acetaminophen (AC) and tryptophan (TRP). In the first part of the work, we synthesized DTDF by electrochemically oxidizing the catechol derivative in the presence of dimedone as a nucleophile in an aqueous solution. A modified carbon paste electrode based on this electrosynthesised compound (DTDF) and carbon nanotubes (CNTs) was prepared. Cyclic voltammetry was used to investigate the redox properties of this modified electrode at various scan rates. Next, the mediated oxidation of LD at the modified electrode was described. At the optimum pH of 7.0, the oxidation of LD occurs at a potential about 330 mV less positive than that of an unmodified carbon paste electrode. Based on differential pulse voltammetry (DPV), the oxidation of LD exhibited a dynamic range between 1.0 and 1000.0 μM and a detection limit of 0.46 μM. DPV was used for simultaneous determination of LD, AC, and TRP at the modified electrode and quantitation of LD, AC, and TRP in some real samples by the standard addition method.
      PubDate: 2015-01-09
  • A glassy carbon electrode modified with MCM-41/nickel hydroxide
           nanoparticle/multiwalled carbon nanotube composite as a sensor for the
           simultaneous determination of dopamine, piroxicam, and cefixime
    • Abstract: The present work demonstrates that simultaneous determination of dopamine (DA), piroxicam (PRX), and cefixime (CEF) can be performed on the composite of multiwalled carbon nanotubes (MWCNTs), nickel hydroxide nanoparticles (NHNPs), and MCM-41 modified glassy carbon electrode (MWCNTs-NHNPs-MCM-41/GCE). The effect of the composition of MWCNTs, NHNPs, and MCM-41 for the modification of GCE was tested, and the mixture of 5 % NHNPs, 10 % MCM-41, and 85 % MWCNTs was chosen for the fabrication of the sensor. The MWCNTs-NHNPs-MCM-41 composite was characterized by Fourier transform infrared (FTIR), scanning electron microscopy (SEM), and energy-dispersive X-ray (EDX) analysis. Under optimum conditions, the application of differential pulse voltammetry method showed the linear relationship between oxidation peak currents, and the corresponding concentrations of DA, PRX, and CEF were 0.2–85, 0.1–70, and 0.1–200 μM with detection limits of 0.07, 0.04, and 0.05 μM, respectively. The proposed method was used in the determination of these compounds in human urine and blood serum samples with satisfactory results. Graphical abstract ᅟ
      PubDate: 2015-01-09
  • Unmodified screen-printed silver electrode for facile detection of
           organophosphorus pesticide
    • Abstract: An uncomplicated method for the detection of organophosphorous pesticide characterized by a thione moiety (P = S) was developed, and chlorpyrifos was used as an example. It was based on the detection of thiocholine generated by acetylcholinesterase. Organophosphorothionates slightly inhibited acetylcholinesterase, and P = S in chlorpyrifos was oxidized into P = O to improve the toxicity. Optimized amount of n-bromosuccinimide (4 ppm) and ascorbic acid (20 ppm) were used for the conversion. The influence of the excessive ascorbic acid and the high overpotential of the thiocholine was addressed by using a screen-printed silver electrode. According to cyclic voltammetry and amperometry, oxidization of thiocholine occurred on the electrode at a low potential while the ascorbic acid was not oxidized. The working potential was minimized to 0 V, and a detection limit of 2.5 ppb for chlorpyrifos was obtained. This method was further used to detect chlorpyrifos in Fuji apple and cucumber.
      PubDate: 2015-01-07
  • Preparation and performance of a composite polyimide/poly(vinylidene
           fluoride- co -hexafluoropropylene)/nano-Al 2 O 3 polymer electrolyte for
           lithium-sulfur cell
    • Abstract: A novel gel polymer electrolyte (GPE) based on an electrospun polymer membrane of polyimide (PI) activating with poly(vinylidene fluoride-co-hexafluoropropylene) (PVDF-HFP) and further coating with nano-Al2O3 was prepared, and its performance for lithium-sulfur (Li-S) cell was investigated. It is found that the Li-S cell using the new GPE enabled achieving a stable discharge capacity of 820 mAh g−1 after more than 100 cycles. This new GPE system with activating with PVDF-HFP and further coating with nano-Al2O3 was capable of upholding the electrolyte solution and can suppress the dissolution of the intermediate products generated during the discharge process and thus improves the performance of Li-S cell.
      PubDate: 2015-01-06
  • Electrochemical properties of citric acid-assisted combustion synthesis of
           Li 4 Ti 5 O 12 adopting Cr by the solid-state reaction process
    • Abstract: The effects of Cr3+ doping and citric acid combustion on the electrochemical properties of Li4Ti5O12 were systematically investigated. The solid-state reaction process was used to synthesize four samples marked as LTO, C-LTO, LT-Cr-O, and C-LT-Cr-O, respectively. X-ray diffraction (XRD) analysis and scanning electron microscopy (SEM) techniques were employed to study their structures and morphologies. The cyclic voltammetry (CV) tests, electrochemical impedance spectroscopy (EIS) analysis, and charge–discharge cycling were performed to study their electrochemical performance. The experimental results showed that the C-LT-Cr-O sample exhibited the advantages both of the Cr3+ doping and the citric acid combustion, presented high ordered morphology and high phase purity, and displayed a discharge capacity of 101.3 mAh g−1 with about 91.8 % capacity retention after 1000 cycles at 10C discharge rate. Therefore, the C-LT-Cr-O material is a promising anode material to be used in lithium ion batteries. Graphical abstract Li4Ti4.7Cr0.3O12 with high ordered morphology and high phase purity presented excellent electrochemical performance, which still displayed a discharge capacity of 101.3 mAh g−1 with about 91.8 % capacity retention even after 1000 cycles at 10C.
      PubDate: 2015-01-06
  • Synthesis of single-crystalline LiFePO 4 with rhombus-like morphology
    • Abstract: In this investigation, carbon-coated LiFePO4 cathode materials were synthesized with a facile hydrothermal method. The structure and electrochemical properties of the materials were investigated by X-ray diffraction (XRD), Roman, transmission electron microscopy-energy dispersive spectroscopy (TEM-EDS), and electrochemical impedance spectroscopy (EIS). By adjusting the mixing concentration of starting materials, a single-crystalline LiFePO4 with an anisotropic rhombus morphology (Space Group: Pmnb No. 62) were successfully synthesized. In addition, the carbon coated on the surface of LiFePO4 material prepared has a lower ID/IG (0.80), which indicates an optimized carbon structure with an increased amount of sp2-type carbon. Electrochemical performance test shows that the carbon-coated LiFePO4 cathode materials have an initial discharge capacity of 146 mAh g−1 at 0.2C.
      PubDate: 2015-01-01
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