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1.
Fe-10Cr nanocrystalline (nc) coatings with a grain size of 20-30 nm were synthesized on glass substrates by magnetron sputtering. The corrosion behavior was investigated in 0.05 mol/L H2SO4 + 0.25 mol/L Na2SO4 and 0.05 mol/L H2SO4 + 0.5 mol/L NaCl solution by polarization curves, EIS and Mott-Schottky analysis. The results showed that compared to Fe-10Cr cast alloy, the active dissolution of the coating was accelerated; the passive film contained more Cr and therefore the coating was easier to passivate. The passive films formed on Fe-10Cr nc and cast alloy exhibited n-type semiconducting behavior in acidic solutions without Cl− and p-type semiconducting behavior in acidic solutions with Cl−. The lower breakdown potential for both materials in the solution with Cl− is related to the p-type passive film formed on them. For Fe-10Cr nc, lower donor density and increased Cr content were responsible for the chemical stability of the passive film. 相似文献
2.
Zn2SnO4 anode powders were successfully synthesized using supercritical water (SCW) and metal salt solutions with 10 min reaction time. Effect of NaOH concentration, Zn to Sn ratio, and synthesis temperature were studied with a SCW batch reactor. X-ray diffraction (XRD), scanning electron microscopy (SEM), and charge/discharge cycling tests were employed to characterize the physical properties and electrochemical performance of the as-prepared samples. Alkaline solution concentration and synthesis temperature played a key role in the production of single-phase Zn2SnO4 powders. At a solution concentration of 0.3 M NaOH and a molar ratio of Zn:Sn = 2:1 at 400 °C and 30 MPa, the average size range of the pure Zn2SnO4 powders was 0.5-1.0 μm, and the morphology was nearly uniform and cubic-like in shape. The initial specific discharge capacity of the Zn2SnO4 powders prepared at this condition was 1526 mAh/g at a current density of 0.75 mA/cm2 in 0.05-3.0 V, and their irreversible capacity loss was 433 mAh/g. The discharge capacities of the Zn2SnO4 powders decreased with cycling and remained at 856 mAh/g after 50 cycles, which was 56% of the initial capacity. 相似文献
3.
Characterization and performance of hydrous manganese oxide prepared by electrochemical method and its application for supercapacitors 总被引:1,自引:0,他引:1
Hydrous manganese oxide was deposited on graphite substrates at anodic potentials of 0.5-0.95 V versus saturated calomel electrode (SCE) in 0.25 M Mn(CH3COO)2 solution at 25 °C. Morphology of manganese oxide prepared was examined by scanning electron microscopy (SEM). Manganese oxide deposited at various anodic potentials was evaluated by cyclic voltammetry with various potential scan rates in different electrolytes. Results indicated that the pseudocapacitive behaviors of manganese oxide were excellent both in 2 M KCl and 2 M (NH4)2SO4 solutions at room temperature. Manganese oxide deposited at 0.5 V versus SCE showed better capacitive behaviors, the specific capacitances were 275 F/g in 2 M KCl solution and 310 F/g in 2 M (NH4)2SO4 solution, respectively. Besides, better electrochemical reversibility could be obtained in 2 M KCl solution. 相似文献
4.
Effect of limited artificial aeration on constructed wetland treatment of domestic wastewater 总被引:3,自引:0,他引:3
To study the effect of limited artificial aeration on domestic wastewater treatment in the constructed wetlands (CWs), four pilot-scale horizontal subsurface flow CWs were operated from October 2006 to September 2007. The types of the four units include aerated and planted CW (APCW), planted CW (PCW), aerated CW (ACW) and CW, and all the units have the identical dimensions of 3 m in length, 0.7 m in width and 1 m in depth. The automated aeration was activated when the oxygen concentrations in the units were lower than 0.2 mg/L and ceased when the oxygen concentrations in the CWs were higher than 0.6 mg/L. More stable alkaline pH values were found in aeration units than that in the non-aeration units. APCW, in which the removal efficiencies of BOD, NH4+-N and TN were 94.4% (16.7 g BOD d− 1 m− 2), 89.1% (4.54 g NH4+-N d− 1 m− 2), and 86.0%( 4.99 g TN d− 1 m− 2) respectively, was more effective at pollutant removal than the other three units. There were no significant differences in TP removal between the aeration units and non-aeration units. Less surface area is needed due to high removal efficiency in APCW and the additional cost of operation is quite little. The results from this experiment indicated that limited artificial aeration in constructed wetlands is a cost-effective method for treating domestic wastewater. 相似文献
5.
Spinel compound LiNi0.5Mn1.5O4 was synthesized by a chemical wet method. Mn(NO3)2, Ni(NO3)2·6H2O, NH4HCO3 and LiOH·H2O were used as the starting materials. At first, Mn(NO3)2 and Ni(NO3)2·6H2O reacted with NH4HCO3 to produce a precursor, then the precursor reacted with LiOH·H2O to synthesize product LiNi0.5Mn1.5O4. The product showed a single spinel phase under appropriate calcination conditions, and exhibited a high voltage plateau at about 4.6-4.8 V in the charge/discharge process. The LiNi0.5Mn1.5O4 had a discharge specific capacity of 118 mAh/g at about 4.6 V and 126 mAh/g in total in the first cycle at a discharge current density of 2 mA/cm2. After 50 cycles, the total discharge capacity was above 118 mAh/g. 相似文献
6.
M.F.Z. Kadir 《Electrochimica acta》2010,55(4):1475-1482
This paper focused on the transport studies of PVA-chitosan blended electrolyte system and application in proton batteries. The electrolytes were prepared by the solution cast technique. In this work, 36 wt.% PVA and 24 wt.% chitosan blend doped with 40 wt.% NH4NO3 exhibited the highest room temperature conductivity. The conductivity value obtained was 2.07 × 10−5 S cm−1. EC was then added in various quantities to the 60 wt.% [60 wt.% PVA-40 wt.% chitosan]-40 wt.% NH4NO3 composition in order to enhance the conductivity of the sample. The highest conductivity obtained was 1.60 × 10−3 S cm−1 for the sample containing 70 wt.% EC. The Rice and Roth model was applied to analyze the conductivity enhancement. The highest conducting sample in the plasticized system was used to fabricate several batteries with configuration Zn//MnO2. The open circuit potential (OCP) of the fabricated batteries was between 1.6 and 1.7 V. 相似文献
7.
Poly 3,4-ethylenedioxythiophene (PEDOT)-based NiFe2O4 conducting nanocomposites were synthesized and their electrochemical properties were studied in order to find out their suitability as electrode materials for supercapacitor. Nanocrystalline nickel ferrites (5-20 nm) have been synthesized by sol-gel method. Reverse microemulsion polymerization in n-hexane medium for PEDOT nanotube and aqueous miceller dispersion polymerization for bulk PEDOT formation using different surfactants have been adopted. Structural morphology and characterization were studied using XRD, SEM, TEM and IR spectroscopy. Electrochemical performances of these electrode materials were carried out using cyclic voltammetry at different scan rates (2-20 mV/s) and galvanostatic charge-discharge at different constant current densities (0.5-10 mA/cm2) in acetonitrile solvent containing 1 M LiClO4 electrolyte. Nanocomposite electrode material shows high specific capacitance (251 F/g) in comparison to its constituents viz NiFe2O4 (127 F/g) and PEDOT (156 F/g) where morphology of the pore structure plays a significant role over the total surface area. Contribution of pseudocapacitance (CFS) arising from the redox reactions over the electrical double layer capacitance (CDL) in the composite materials have also been investigated through the measurement of AC impedance in the frequency range 10 kHz-10 mHz with a potential amplitude of 5 mV. The small attenuation (∼16%) in capacitance of PEDOT-NiFe2O4 composite over 500 continuous charging/discharging cycles suggests its excellent electrochemical stability. 相似文献
8.
A milling process to reduce kaolin to amorphous phase in the presence of KH2PO4 or NH4H2PO4 and allow mechanochemical (MC) reaction for incorporation of KH2PO4 and NH4H2PO4 into the kaolin structure was investigated in this work. Mixtures of kaolin and KH2PO4 and NH4H2PO4 in separate systems were prepared by milling in a planetary ball mill. Tests with kaolin contents ranging from 25 to 75 wt.% and mill rotational speeds from 200 to 700 rpm were performed to evaluate incorporation of KH2PO4 and NH4H2PO4 and release of K+, NH4+ and PO43− ions into solution. Analyses by XRD, DTA and ion chromatography indicated that the MC process was successfully applied to incorporate both KH2PO4 and NH4H2PO4 into the amorphous kaolin structure. Release of K+ and PO43− ions from the system (kaolin-KH2PO4) when dispersed in water for 24 h reached only up to 10%. Under similar conditions for the system (kaolin-NH4H2PO4), release of NH4+ and PO43− ions reached between 25 and 40%. These results indicated that the MC process can be developed to allow amorphous kaolin to act as a carrier of K+, NH4+ and PO43− nutrients to be released slowly for use as fertilizer. 相似文献
9.
Some polyanionic compounds, e.g. TiP2O7 and LiTi2(PO4)3 with 3D framework structure were proposed to be used as anodes of lithium ion battery with aqueous electrolyte. The cyclic voltammetry properties TiP2O7 and LiTi2(PO4)3 suggested that Li-ion de/intercalation reaction can occur without serious hydrogen evolution in 5 M LiNO3 aqueous solution. The TiP2O7 and LiTi2(PO4)3 give capacities of about 80 mAh/g between potentials of −0.50 V and 0 V (versus SHE) and 90 mAh/g between −0.65 V and −0.10 V (versus SHE), respectively. A test cell consisting of TiP2O7/5 M LiNO3/LiMn2O4 delivers approximately 42 mAh/g (weight of cathode and anode) at average voltage of 1.40 V, and LiTi2(PO4)3/5 M LiNO3/LiMn2O4 delivers approximately 45 mAh/g at average voltage of 1.50 V. Both as-assembled cells suffered from short cycle life. The capacity fading may be related to deterioration of anode material. 相似文献
10.
The protein poly-l-leucine has been used as a model compound for the nitrogen in biomass fuels. It was pyrolysed in a fluidised bed at 700 and 800 °C and the pyrolysis gases were analysed with a FT-IR spectrometer. HCN, NH3 and HNCO were identified as the main nitrogen-containing species, while neither NO nor N2O were found among the pyrolysis gases. At 700 °C, as much as 58% of the nitrogen content was converted into HCN and 31% into NH3. The HCN/NH3 ratio increased from about 1.9 at 700 °C to above 2.2 at 800 °C. Pyrolysis of another protein, poly-l-proline, at 800 °C gave a HCN/NH3 ratio close to 10. This revealed that the protein's amino acid composition has a marked impact on the composition of the pyrolysate. 相似文献
11.
In situ electrochemical-scanning tunneling microcopy (EC-STM) was employed to investigate the etching dynamics of the moderately doped n-Si(1 1 1) electrode during cyclic voltammetric perturbation and at the seven different potentials including the open circuit potential (OCP) in 40% NH4F solution at pH 10, which was prepared from 40% NH4F and concentrated NH4OH solution. The etching rate was significant at OCP and showed an exponential dependence on the potential applied to the silicon substrate electrode. Although some triangular pits were generated at the Si(1 1 1) surface, at the potentials more negative than OCP the site dependence in the removal of surface silicon atoms prevailed and led to the atomically flat Si(1 1 1):H surfaces with sharply defined steps of the step height 3.1 Å, where the interatomic distance of 3.8 Å was observed with a three-fold symmetry. At the potentials sufficiently more positive than OCP, macroporous hole was formed to limit further in situ EC-STM study. The results were compared with in situ EC-STM studies of the etching reaction of n-Si(1 1 1):H in the aqueous solution of dilute ammonium fluoride at pH 5, 40% NH4F at pH 8, and 1 M NaOH reported in the literature. 相似文献
12.
Chang-Mao Hung 《Powder Technology》2009,196(1):56-61
This work considers the oxidation of ammonia (NH3) by selective catalytic oxidation (SCO) over a CuO/La2O3 composite catalyst at temperatures between 150 and 400 °C. A CuO/La2O3 composite catalyst was prepared by co-precipitation of copper nitrate and lanthanum nitrate at various molar concentrations. This study also considers how the concentration of influent NH3 (C0 = 1000 ppm), the space velocity (GHSV = 92,000 l/h), the relative humidity (RH = 12%) and the concentration of oxygen (O2 = 4%) affect the operational stability and the capacity for removing NH3. The catalysts that were characterized using FTIR, XRD, UV-Vis, BET and PSA, have shown that the catalytic behavior is related to the copper (II) oxide, while lanthanum (III) oxide may serve only to provide active sites for the reaction during a catalyzed oxidation run. The experimental results show that the extent of conversion of ammonia by SCO in the presence of the CuO/La2O3 composite catalyst was a function of the molar ratio. The ammonia was removed by oxidation in the absence of CuO/La2O3 composite catalyst, and around 93.0% NH3 reduction was achieved during catalytic oxidation over the CuO/La2O3 (8:2, molar/molar) catalyst at 400 °C with an oxygen content of 4.0%. Moreover, the effect of the reaction temperature on the removal of NH3 in the gaseous phase was also monitored at a gas hourly space velocity of under 92,000 h− 1. 相似文献
13.
A novel process for the deposition of a hydroxyapatite (HA) coating on a smooth implant surface has been developed. Specimens were firstly subjected to electrodeposition at −1.8 V (versus Ag/AgCl) in a mixed solution of 0.042 M Ca(NO3)2·4H2O and 0.025 M NH4H2PO4 at 85 °C for 5 s, and then post-treated in 1 M NaOH solution for 30 min. The experimental results showed the specimens prepared by the designed process to have better adhesion properties than those prepared by the traditional electrodeposition process. 相似文献
14.
The electrochemical behavior of a commercial LiCoO2 with spherical shape in a saturated Li2SO4 aqueous solution was investigated with cyclic voltammetry and electrochemical impedance spectroscopy. Three redox couples at ESCE = 0.87/0.71, 0.95/0.90 and 1.06/1.01 V corresponding to those found at ELi/Li+=4.08/3.83, 4.13/4.03 and 4.21/4.14 V in organic electrolyte solutions were observed. The diffusion coefficient of lithium ions is 1.649 × 10−10 cm2 s−1, close to the value in organic electrolyte solutions. The results indicate that the intercalation and deintercalation behavior of lithium ions in the Li2SO4 solution is similar to that in the organic electrolyte solutions. However, due to the higher ionic conductivity of the aqueous solution, current response and reversibility of redox behavior in the aqueous solution are better than in the organic electrolyte solutions, suggesting that the aqueous solution is favorable for high rate capability. The charge transfer resistance, the exchange current and the capacitance of the double layer vary with the charge voltage during the deintercalation process. At the peak of the oxidation (0.87 V), the charge transfer resistance is the lowest. These fundamental results provide a good base for exploring new safe power sources for large scale energy storage. 相似文献
15.
Porous Si3N4 ceramics prepared via slip casting of Si and reaction bonded silicon nitride 总被引:1,自引:0,他引:1
Dongxu Yao Yongfeng XiaYu-Ping Zeng Kai-hui ZuoDongliang Jiang 《Ceramics International》2011,37(8):3071-3076
Slip casting process combined with reaction bonded silicon nitride (RBSN) was used to prepare porous Si3N4 ceramic with near-net and complex shape. A butyl stearate (BS) coated process was introduced to restrain the hydrolysis of Si, and ammonium polyacrylate (NH4PAA) was used to enhance the dispersion of coated Si. The measured oxygen content showed that the hydrolysis of Si was strongly prohibited by BS coating, and relatively low viscosity was obtained with the addition of 0.25-1.5 wt% NH4PAA to the 60 wt% solid load slurry. 40-60 wt% solid load slurries were used for slip casting in the experiment. After vacuum degassing, slip casting, debindering and nitridation, a density of 1.57-1.92 g/cm3 (porosity 50.9-40%) and a flexural strength of 47-108 MPa were obtained. The samples without vacuum degassing showed a large number of nanowires grown in the large pores. 相似文献
16.
To improve the cathodic performance of olivine-type LiMnPO4, we investigated the optimal annealing conditions for a composite of carbon with cation doping. Nanocrystalline and the cation-doped LiMn1−xMxPO4 (M = Ti, Mg, Zr and x = 0, 0.01, 0.05 and 0.10) was synthesized in aqueous solution using a planetary ball mill. The synthesis was performed at the fairly low temperature of 350 °C to limit particle size. The obtained samples except for the Zr doped one consisted of uniform and nano-sized particles. The performance of LiMnPO4 was much improved by an annealing treatment between 500 and 550 °C with carbon in an inert atmosphere. A small amount of metal-rich phosphide (Mn2P) was detected in the sample annealed at 900 °C. In addition, 1 at.% Mg doping for Fe enhanced the rate capability in our doped samples. The discharge capacity of LiMn0.99Mg0.01PO4/C was 146 mAh/g at 0.1 mA/cm2 and 125 mAh/g even at 2.0 mA/cm2. 相似文献
17.
N. Sharma 《Electrochimica acta》2005,50(27):5305-5312
Carbon-coated CaWO4 nano-crystalline phases have been synthesized by ambient temperature solution precipitation method, characterized by X-ray diffraction, SEM and thermogravimetry and their electrochemical properties were studied versus Li metal. Galvanostatic cycling at a current of 60 mA/g in the voltage range 0.005-3.0 V on the 5 wt.% C-coated CaWO4 gave a reversible capacity of 230 ± 5 mAh/g corresponding to 2.5 mol of Li, which is almost stable from 20 to 50 cycles. Under the same conditions, the 10 wt.% C-coated CaWO4 showed a capacity of 355 ± 5 mAh/g (3.8 mol of Li) during the initial cycles, but the capacity degraded at a rate of 1.6 mAh/g per cycle in the range 5-100 cycles. A good operating voltage range was found to be 0.005-3.0 V with average discharge and charge potentials being 0.6 and 1.3 V, respectively. Coulombic efficiency in all cases was 96-98%. Cyclic voltammograms compliment the galvanostatic results. Impedance spectral data on the 10 wt.% C-coated CaWO4 at different voltages during the first and 20th discharge-charge cycle have been interpreted in terms of the variations in the bulk and charge-transfer resistances of the composite electrode. A reaction mechanism involving the formation/decomposition of the oxide bronze, ‘LixWOy’ has been proposed to explain the electrochemical cycling. 相似文献
18.
S. Manandhar 《Electrochimica acta》2007,52(15):5010-5017
X-ray photoelectron spectroscopy (XPS) was used to study the spontaneous deposition of Pt and Ir on Ru(0 0 0 1). The spontaneous deposition experiments were performed in a combined ultra high vacuum/electrochemistry (UHV-EC) system allowing sample transport between UHV and electrochemical environments under controlled conditions. The Ru(0 0 0 1) electrode surface was cleaned in UHV and then brought into contact with either a Pt-containing solution(10 mM K2PtCl6 + 0.1 M H2SO4 or 10 mM (NH4)2PtCl4 + DI water) or with solutions containing 10 mM (NH4)2IrCl6 in varying concentrations of H2SO4 corresponding to pH values of 0.5, 1 and 7 in the electrochemistry chamber for 30 min without an externally applied potential. XPS data acquired after rinsing in DI water indicated that each metal is present in intermediate oxidation states. Pt is found spontaneously deposited as Pt(II) on Ru(0 0 0 1) at pH 1. Similarly, intermediate states of Ir are observed, with higher binding energies, characteristic of higher oxidation states, observed at higher pH values. Annealing the spontaneously deposited adlayer in UHV to >500 K in each case results in the reduction of the Pt or Ir adsorbate to the metallic state. Typical metal surface coverages, determined by XPS, varied with number of immersions and solution conditions, but in all cases was observed to be <0.3 monolayers average thickness. 相似文献
19.
In this study, model flue gas was bubbled into 0.25 L tribasic sodium citrate (TSC) solution being in 0.5 L glass absorber to remove its SO2 content. Size of gas bubbles, absorption temperature, gas flow rate, solution concentration and stirring rate were taken as working parameters to investigate their effect on SO2 removal from flue gas. The Taguchi's experimental design method was used to obtain optimum values of working parameters for SO2 saturation time of the TSC solution selected as a quality characteristic. The optimum levels of parameters to maximize the SO2 saturation time of TSC solution were coarse bubbles for gas delivery, 35 °C for absorption temperature, 1.5 slm for gas flow rate, 0.5 M for TSC solution concentration and 500 rpm for stirring rate. Under these conditions, the SO2 saturation time of the TSC solution was achieved as 511 min in average. The most effective parameters on the absorption of SO2 in TSC solutions were ranked to the least as solution concentration, gas flow rate, size of gas bubbles, absorption temperature and stirring rate. 相似文献
20.
Deyu Wang 《Electrochimica acta》2005,50(14):2955-2958
LiFePO4 doped by bivalent cation in Fe-sites show improved rate performance and cyclic stability. Under 10 C rate at room temperature, the capacities of LiFe0.9M0.1PO4 (M = Ni, Co, Mg) maintain at 81.7, 90.4 and 88.7 mAh/g, respectively, in comparison with 53.7 mAh/g for undoped LiFePO4 and 54.8 mAh/g for carbon-coated LiFePO4 (LiFePO4/C). The capacity retention is 95% after 100 cycles for doped samples while this value is only 70% for LiFePO4 and LiFePO4/C. Such a significant improvement in electrochemical performance should be partially related to the enhanced electronic conductivities (from 2.2 × 10−9 to <2.5 × 10−7 S cm−1) and probably the mobility of Li+ ions in the doped samples. 相似文献