mA Cm-2 Current Density Research Articles

Direct Electrosynthesis of Polyaniline–Fe2O3 Nanocomposite Coating on Aluminum Alloy 5052 and Its Corrosion Protection Performance

The synthesis of polyaniline- Fe2O3 nanocomposite coating on aluminum Alloy 5052 (AA5052) surface has been investigated by using the galvanostatic method. The anticorrosion performance of polyaniline-Fe2O3 coating was investigated in 3.5% NaCl solution by the open- circuit potential (OCP), Tafel polarization technique and Electrochemical Impedance Spectroscopy (EIS). The corrosion rate of polyaniline-Fe2O3 nanocomposite coating AA5052 was found about140 times lower than bare AA5052. Corrosion potential also decreased from -0.710 V to -0.735 V versus Ag/AgCl for uncoated AA5052 and polyaniline-Fe2O3 nanocomposite coated on AA5052 electrodes, respectively. Electrochemical measurements show that polyaniline-Fe2O3 nanocomposite coated has good inhibitive properties with PE% of ~97.3% at 25 mA cm-2 current density applied on AA5052 corrosion in a chloride media. The results of this study clearly find out that the polyaniline-Fe2O3 nanocomposite has an outstanding possible to protect AA5052 against corrosion in a chloride environment.

Rapid Polyol-Assisted Microwave Synthesis of Nanocrystalline LiFePO4/C Cathode for Lithium-Ion Batteries.

Nanocrystalline LiFePO4/C has been synthesized under a very short period of time (90 sec) using a polyol-assisted microwave heating synthesis technique. The X-ray diffraction (XRD) data indicates that the rapidly synthesized materials correspond to phase pure olivine. Post-annealing of the as-prepared sample at 600 °C in argon atmosphere yields highly crystalline LiFePO4/C. The morphology of the samples studied using scanning electron microscopy (SEM) reveals the presence of secondary particles formed from aggregation of primary particles in the range of 30-50 nm. Transmission electron microscopy (TEM) images reveal a thin carbon layer coating on the surface of the primary particle. The charge/discharge studies indicate that the as-prepared and annealed LiFePO4/C samples delivered initial discharge capacities of 126 and 160 mA h g-1, respectively, with good capacity retentions at 0.05 mA cm-2 current densities. The post-annealing process indeed improves the crystallinity of the LiFePO4 nanocrystals, which enhances the electrode performance of LiFePO4/C.

The porosity and roughness of electrodeposited calcium phosphate coatings in simulated body fluid

Calcium phosphate coatings were electrochemically deposited on titanium from the aqueous solution of Ca(NO3)2 and NH4H2PO4 with the current density of 10 mA cm-2 for deposition time of 15 min. The obtained brushite coatings, (CaHPO4?2H2O), were converted to hydroxyapatite (HA) by soaking in simulated body fluid (SBF) for 2, 7 and 14 days. The brushite and hydroxyapatite coatings were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM) and atomic force microscopy (AFM). It was shown that the increase in soaking time increases the porosity, roughness and crystallite domain size of HA coatings and decreases the unit cell parameters and unit cell volume, while does not affect the HA mean pore area. The calcium and phosphorus ions concentrations in SBF were determined by atomic absorption spectroscopy (AAS) and UV-Vis spectroscopy, respectively and the mechanism of HA growth based on dissolution-precipitation was proposed.

ELECTROLYSIS OF SWINE MANURE EFFLUENTS USING THREE DIFFERENT ELECTRODES Fe-Fe, Al-Al AND Fe-Al

Swine effluent with high organic strength need to be treated to make it suitable for applying to crop/pasture fields, or discharging to any waterways. Electrocoagulation is a relatively simpler and cheaper technique over biological and chemical treatment methods currently used to treat high-strength industrial and municipal wastewater. The performance of an electrocoagulation system mainly depends on the pH, Electrical Conductivity (EC) of the medium, Chemical Oxygen Demand (COD) loading rates and catalytic activity of the electrodes used. In this research, a study was conducted to compare the pollutant removal efficiencies of three electrodes (Fe-Fe, Al-Al and Fe-Al) with three electric current levels (500, 1000 and 2000 mA) while treating swine manure effluents. The electrochemical cell consisted of two parallel rectangular plates (90×25×1.5 mm) of Iron (Fe-Fe), Aluminum (Al-Al) and Iron-Aluminum (Fe-Al, later on described as hybrid) electrodes; immersed in a beaker with 550 mL swine effluents and powered by a Direct Current (DC) supply. All studies were conducted in batches at room temperature. In general, removal efficiencies were increased with increasing current densities and electrolysis times for electrodes evaluated. Aluminum electrodes outperformed iron and hybrid (iron-aluminum electrodes) in removing Total Phosphorus (TP) at all current density levels tested. Overall, use of hybrid electrodes resulted in better COD removal. For the same treatment times (1200 s) at higher current density (21 mA cm-2), hybrid electrodes removed about 100% COD, which are about 1.9 and 1.3 times higher than those of aluminum and iron electrodes, respectively. Iron electrodes showed the highest removal efficiency (85%) for Total Organic Carbon (TOC) at 21 mA cm-2 current density and 1200 s treatment time. Overall, lower Specific Electrical Energy Consumptions (SEECs) per kg of Pollutants (TP, COD and TOC) were estimated for the aluminum electrodes than the other electrodes combination.

Generation of Hydrogen Peroxide in DMFC

The novel process of H2O2 generation in the direct methanol fuel cell (DMFC) composed from the "Black Pearls 2000" gas-diffusion cathode (GDE), washed by sodium chloride brine or sea water for O2 electro-reduction and the half-membrane-electrode assembly (MEA) with the Nafion 115® cation-exchange membrane (CEM), hot pressed on one side with the carbonic gas-diffusion anode impregnated by Pt/Ru catalyst for methanol oxidation, has been developed. The effect of NaCl concentration in the catholyte, methanol and the KOH concentration in the anolyte, electrolyte temperature and circulation flow rate on the generated cell voltage, current and H2O2 current efficiency have been studied in 2 hour trials. 87-95 % current efficiency for H2O2 generation with a 5.286 -9.44 mg h-1 cm-2 rate and at 15 mA cm-2 current density was achieved in the DMFC with 1 M CH3OH +7M KOH in the anolyte and 30 g L-1 NaCl in the catholyte.

On the Relationship between the Characteristics of Bilirubin Oxidases and O2 Cathodes Based on Their “Wiring”

The characteristics of a novel cathode on which O2 is electroreduced to water under physiological conditions (pH 7.4, 0.15 M NaCl, 37.5 °C) are reported. The cathode was made by electrically connecting (“wiring”) redox centers of bilirubin oxidase (BOD) from Trachyderma tsunodae (Tt) to carbon electrodes through a redox polymer. The cathode was more stable than that made by wiring BOD from Myrothecium verrucaria (Mv) (N. Mano et al., J. Am. Chem. Soc. 2002, 124, 6480−6486) (5% loss of current per day of operation vs 10%), and its operating potential at 3 mA cm-2 current density was −140 mV vs the potential of the reversible O2/H2O electrode, 50 mV higher than that of the Mv-BOD cathode. The improved stability is attributed to stronger electrostatic bonding in the adduct of Tt-BOD with the “wiring” redox polymer, and the higher operating potential to the replacement of methionine by phenylalanine in the axial position of the type 1 Cu+/2+ center, which upshifts the center's potential.

Direct comparison of electric field measurement byfluorescence and optogalvanic Stark spectroscopies

Electric field in the cathode fall region of a 2.2 Torr heliumdc discharge with 0.8 mA cm-2 current density has beenmeasured from the Stark splittings of 11 1P (unperturbed)Rydberg transition by simultaneous optogalvanic (OG) andfluorescence techniques. The LIF Stark spectra showed narrowerlinewidths compared to the OG spectra for higher parabolicquantum number states; LIF data also showed broader linewidthsfor higher parabolic quantum number states compared to the linesin the centre of the manifold. However, the electric fieldsobtained from the two methods were in agreement with each otherwithin three per cent for all the measured locations in thesheath. A comparison of the OG spectrum with the off-axis LIF datashows a combination of signal gain in the high-field regionalong with the Stark intensity distribution permits the line-of-sight-averaged OG spectrum to obtain accurate field values in adischarge with modest radial field gradients.