“伏-安”法测量电阻实验教学研究

简要介绍"伏-安"法测量电阻实验中存在的缺陷,提出了解决的办法,并经过严谨的数学推导,给出了更合理的计算公式.

Electrochemical behavior of Fe(Ⅲ)in Na_(2)SiO_(3)-SiO_(2)-Fe_(2)O_(3)molten salt

The high-temperature requirement for liquid iron smelting via molten oxide electrolysis presents significant challenges.This study investigates the electrochemical reduction of Fe(Ⅲ)in a novel low-temperature electrolyte,Na_(2)SiO_(3)-SiO_(2)-Fe_(2)O_(3),utilizing cyclic voltammetry and square wave voltammetry techniques.The results show that Fe(Ⅲ)reduction occurs in two steps:Fe(Ⅲ)+e^(−)→Fe(Ⅱ),Fe(Ⅱ)+2e^(−)→Fe,and that the redox process of Fe(Ⅲ)/Fe(Ⅱ)at the tungsten electrode is an irreversible reaction controlled by diffusion.The diffusion coefficients of Fe(Ⅲ)in the molten Na_(2)SiO_(3)-SiO_(2)-Fe_(2)O_(3)in the temperature range of 1248–1278 K are between 1.86×10^(−6)cm^(2)/s and 1.58×10^(−4)cm^(2)/s.The diffusion activation energy of Fe(Ⅲ)in the molten salt is 1825.41 kJ/mol.As confirmed by XRD analysis,potentiostatic electrolysis at−0.857 V(vs.O_(2)/O_(complex)^(2-))for 6 h produces metallic iron on the cathode.

On-line detection of Cu(II) in bioleaching system by anodic stripping differential pulse voltammetry

On-line Cu （II） ion concentration detection in bioleaching system was achieved by anodic stripping differential pulse voltammetry （ASDPV）. Good linearity between Cu （II） concentration and oxidation peak current was obtained when Cu （II） existed in 0K media in the concentration range of 1μmol/L （64μg/L） to 1 mmol/L （64 mg/L）. Moreover, when 0.2 mol/L KCl was added into this media, the linear detection range could be extended from 1 mmol/L to 100 mmol/L （6.4 g/L）. The reduction of Cu （II） to metallic copper was shown to proceed as two successive single-electron transfer reactions involving an intermediate chemical step where the cuprous ion （Cu＋） was complexed by chloride to form the dichlorocuprous anion （CuCl-）. In addition, interference effect was also investigated when Fe3＋existed in the media, which was the common situation in the copper bioleaching system. The results showed no interference effect once the concentration of Fe3＋was less than 100 mmol/L （5.6 g/L）.

Growth and crystallization behaviors of anodic oxide films on sputter-deposited titanium at very low potentials

Growth and crystallization of titanium anodized films were studied by performing the anodization of the sputter-deposited titanium samples under cyclic voltammetry （CV） mode at very low potentials. The surface features, crystalline behaviors and chemical compositions of the formed anodic oxide layers were detected by AFM, SE and XPS. It was found that the structure of the titanium anodized films is crystalline, even though the maximum oxidation potential （（Pmax） is very low （as low as 1000 mY）. Both enlarging the applied voltage and reducing the potential scanning rate are beneficial for the growth and crystallization of titanium oxide films. It was thought that the internal compressive stress, other than the local joule heating accepted for many researchers, is the main force of stimulating the crystallization of anodic titanium oxide films at very low potentials.

Effects of MK-801 and Schizandrol A on DA/DOPAC Measured by Voltammetry in Ischemic Rat Striatum

The time course of changes in the levels of extracellular DA/DOPAC in rat striatum during brain ischemia and reperfusion was measured by the method ofin vivo differential normal pulse voltammetry(DNPV).Acute cerebral ischemia of rats was pro- duced by four—vessel occlusion.The effects of(+)MK-801 and schizandrol A on the change of DA/DOPAC were investigated.The results showed that the DA/DOPAC peak in- creased markedly during 6 min of ischemia and,after reperfusion,the peak height decreased gradually.Both(+)-MK-801 and schizandrol A significantly inhibited the DA release after ischemia jn the striatum.

Substituent Effects on Reduction Potentials of Meta-substituted and Para-substituted Benzylideneanilines

Effects of meta-substituent of 3,4＇/4,3＇/3,3＇-substituted benzylideneanilines （XBAYs） on the electrochemical reduction potentials （E（Red）） were investigated, in which 49 samples of target compounds were synthesized, and their reduction potentials were measured by cyclic voltammetry. The substituent effects on the E（Red） of target compounds were analyzed and an optimality equation with four parameters （Hammett constant a of X, Hammett constant a of Y, excited-state substituent constant σexCC of X, and the substituent specific cross-interaction effect △σexCC2 between X and Y） was obtained. The results show that the factors affecting the E（Red） of 3,4＇/4,31/3,3P-substituted XBAYs are different from those of 4,4＇-substituted XBAYs. For 3,4＇/4,3＇/3,3＇-substituted XBAYs, σ（X） and σ（Y） must be employed, and the contribution of △σexCC2 is important and not negligible. Compared with 4,4＇-substituted XBAYs, X group contributes less to 3,4＇/4,3＇/3,3＇-substituted XBAYs, while Y group contributes more to them. Additionally, it was observed that either para-substituted XBAYs or meta-substituted XBAYs, the substituent effects of X are larger than those of Y on the E（Red） of substituted XBAYs.

Microemulsion synthesis of ZnMn2O4/Mn3O4 sub-microrods for Li-ion batteries and their conversion reaction mechanism

The hierarchical ZnMn2O4/Mn3O4 composite sub-microrods were synthesized via a water-in-oil microemulsion method followed by calcination.The ZnMn2O4/Mn3O4 electrode displays an intriguing capacity increasing from 440 to 910 mA·h/g at 500 mA/g during 550 consecutive discharge/charge cycles,and delivers an ultrahigh capacity of 1276 mA·h/g at 100 mA/g,which is much greater than the theoretical capacity of either ZnMn2O4 or Mn3O4 electrode.To investigate the underlying mechanism of this phenomenon,cyclic voltammetry and differential capacity analysis were applied,both of which reveal the emergence and the growth of new reversible redox reactions upon charge/discharge cycling.The new reversible conversions are probably the results of an activation process of the electrode material during the cycling process,leading to the climbing charge storage.However,the capacity exceeding the theoretical value indicates that there are still other factors contributing to the increasing capacity.

Physicochemical properties of 1,3-dimethyl-2-imidazolinone−ZnCl_(2)solvated ionic liquid and its application in zinc electrodeposition

Zinc chloride(ZnCl_(2))was dissolved in the 1,3-dimethyl-2-imidazolinone(DMI)solvent,and the metallic zinc coatings were obtained by electrodeposition in room-temperature ambient air.The conductivity(σ),viscosity(η),and density(ρ)of the DMI−ZnCl_(2)solvated ionic liquid at various temperatures(T)were measured and fitted.Furthermore,cyclic voltammetry was used to study the electrochemical behavior of Zn(II)in the DMI−ZnCl_(2)solvated ionic liquid,indicating that the reduction of Zn(II)on the tungsten electrode was a one-step two-electron transfer irreversible process.XRD and SEM−EDS analysis of the cathode product confirmed that the deposited coating was metallic zinc.Finally,the effects of deposition potential,temperature and duration on the morphology of zinc coatings were investigated.The results showed that a dense and uniform zinc coating was obtained by potentiostatic electrodeposition at−2 V(vs Pt)and 353 K for 1 h.

Physicochemical properties of DMI-LiNO_(3) solvated ionic liquid and its application in electrodeposition of neodymium at room temperature

The density,conductivity,and viscosity of the 1,3-dimethyl-2-imidazolinone and lithium nitrate(DMILiNO_(3))solvated ionic liquid were measured as a function of temperature.Additionally,the electrochemical mechanism and electrodeposition of neodymium from the DMI-LiNO_(3) solvated ionic liquid were investigated.Cyclic voltammetry results indicate that the electrochemical reduction of Nd(Ⅲ)is irreversible and proceeds via one-step with three-electron transfer,which is controlled by diffusion with a diffusion coefficient of 5.08×10^(-8) cm^(2)/s.Energydispersive X-ray spectrometry and X-ray photoelectron spectroscopy data confirm that the electrodeposit obtained after electrodeposition at-4 V(vs Ag)using the DMI-LiNO_(3)-Nd(CF_(3)SO_(3))_(3) solvated ionic liquid contains metallic neodymium.

Electrochemical Performance of Zn（002） and Zn（100） Single Crystals in 6.0mol·L^-1 KOH

In this article, the electrochemical performance of the electrodes of zinc polycrystal, Zn（002） and Zn（100） single crystals were studied by the Tafel line extrapolation of the potentio-dynamic polarization curves, the cyclic voltammetry and the charge/discharge experiment. The results shows that in 6.0 mol·L^-1 KOH solution the corrosion rate of Zn polycrystal, Zn（100） and Zn（002） single crystals decreases in turn; and the reversibility and the charge/discharge performance of Zn single crystal was superior to Zn polycrystal. The dendrite growth of the surface of Zn polycrvstal was easier than Zn single crystal during the stages of charge/discharge.

Layer by layer synthesis of Sn-Co-C microcomposites and their application in lithium ion batteries

Alloy anodes were studied for pursuing Sn-based microcomposite synthesis, assembly and performance for lithium ion batteries. The self-assembled Sn-Co-C composites with nano-scaled microstructures were prepared via solution method and carbothermal technology. The morphology and physical structure were investigated with scanning electron microscope (SEM) and X-ray diffraction (XRD). The as-prepared materials were assembled to half cell coin for the purpose of discussing the galvanostatic cycling, cyclic voltammetry and rate-capability performance. Results reveal that nanoscaled CoSn 2 alloys covered with Sn and C layer by layer are wrapped by cross-linked porous carbon network to form spherical microstructure. This distinguishing feature of Sn-Co-C composites provides a possible solution to the problems of Sn particle aggregation and poor electron transport, and has strong effect on improving electrochemical performance.

Electrodeposition mechanism of Ni-Al composite coating

Ni-Al composite coatings were electrodeposited from a modified Watts solution. The electrochemical behavior of the coatings was studied by means of zeta potential analysis, voltammetry and electrochemical impedance spectroscopy（EIS）. It was found that the zeta potential of Al particles was-4 m V which is very close to that of Al2O3. Moreover, addition of conductive Al particles into the electrolyte shifted the polarization curve to more negative potentials and loop size of EIS curve increased. It was also demonstrated that the co-deposition behavior of Ni-Al composite coatings obeys the Guglielmi’s model. The results indicate that conductive Al particles behave as the inert particles and confirm the existence of a thin aluminum oxide layer on the surface of aluminum particles.

Electropolymerization of O-Phenylenediamine in an Ionic Liquid

Ionic liquid like 1-ethyl-3-methylimidazolium bromine ([EMIM]Br) has been used as electrolyte for the electropolymerization of O-phenylenediamine at glassy carbon electrode by cyclic voltammetry. It is found that poly (O-phenylenediamine) film modified electrode has favorable electrochemical activity in acid solution.

Electrodeposition Behavior of Nickel from a Low Temperature Urea-molten Salt

The electrodeposition behavior of nickel at glassy carbon(GC)and stainless steel(SS)electrodes in low temperature urea-acetamide-NaBr-KBr melt was investigated using cyclic voltammetry,chrono-amperometric current-time transients and scanning electron microscopy.Cyclic voltammograms and dimensionless chronoamperometric current-time transients analysis show that the electrodeposition of nickel is an irreversible process and proceeds via three-dimensional progressive nucleation with diffusion-controlled growth on both GC and SS substrates.Scanning electron microscopic analysis indicates the nickel deposits obtained on SS electrode are generally uniform,dense,and adherent to the substrate with rounded crystallites in the nanometer size regime.It is also found that the crystal structure of the electrodeposited nickel is independent on the deposition potential.The nickel deposits produced from the melt at higher cathodic potential exhibit larger grain size.

Effect of iron transformation on Acidithiobacillus ferrooxidans bio-leaching of clay vanadium residue

The acid bio-leaching process of vanadium extraction from clay vanadium water-leached residue was studied and the effect of the performance of iron transformation was investigated.Acidithiobacillus ferrooxidans affects the dissolution of vanadium through the catalytic effect on Fe^3+/Fe^2+couple and material exchange.The passivation of iron settling correlates with ferrous ion content in bio-leaching solution.In medium containing A.ferrooxidans and Fe(Ⅲ),the increment in Fe(Ⅱ)concentration leads to the formation of jarosite,generating a decline in vanadium extraction efficiency.Analysis of cyclic voltammetry shows that Fe(Ⅱ)ion is apt to be oxidized and translated into precipitate by A.ferrooxidans,which strongly adsorbed to the surface of the residue.Fe(Ⅲ)ion promotes the vanadium extraction due to its oxidizing activity.Admixing A.ferrooxidans to Fe(Ⅲ)medium elevates the reduction of low valence state vanadium and facilitates the exchange of substance between minerals and solution.This motivates 3.8%and 21.8%increments in recovery ratio and leaching rate of vanadium compared to the Fe(Ⅲ)exclusive use,respectively.Moreover,Fe(Ⅱ)ion impacts vanadium extraction slightly in sterile medium but negatively influences vanadium leaching in the presence of bacteria.

Preparation and Electrochemical Application of Praseodymium Modified TiO2-NTs/SnO2-Sb Anode by Cyclic Voltammetry Method

A Pr-doped TiO2-NTs/SnO2-Sb electrode was prepared by a simple method, cyclic voltarnmetry （CV）. The methyl orange （MO）aqueous solution was selected as a simulated wastewater. The ordered microstructural TiO2-NTs substrate was synthesized by an electrochemical method to obtain large specific surface area and high space utilization. The phase structure, electrode surface morphology and electrochemical properties of electrodes were characterized by XRD, SEM and electrochemical technology, respectively. The results showed that praseo- dymium oxide was successfully doped into the SnOz-Sb film by CV method. Due to the doped Pr, the oxygen evo- lution potential increased from 2.25 V to 2.40 V. The degradation of MO was investigated by UV-vis. The Ct/C0（φ） was studied as a function to obtain the optimal parameters, such as the amount of doped Pr, current density and initial dye concentration. In addition, the degradation process followed pseudo-first-order reaction kinetics and the rate constant was 0.099 3 min-1. The result indicated that the introduction of Pr reduced the formation of oxygen vacancies or enhanced the formation of adsorbed hydroxyl radical groups on the surface, thus leading to better activity and stability.

Anodic passivation of Pb-Ag-Nd anode in fluoride-containing H_2SO_4 solution

An attempt was made to build up a thick and compact oxide layer rapidly by pre-treating the Pb-Ag-Nd anode in fluoride-containing H2SO4 solution. The passivation reaction of Pb-Ag-Nd anode during pre-treatment process was investigated using cyclic voltammetry, linear scanning voltammetry, environmental scanning electron microscopy and X-ray diffraction analysis. The results show that Pb F2 and PbSO4 are formed near the potential of Pb/PbSO4 couple. The pre-treatment in fluoride-containing H2SO4 solution contributes to the formation of a thick, compact and adherent passive film. Furthermore, pre-treatment in fluoride-containing H2SO4 solution also facilitates the formation of PbO2 on the anodic layer, and the reason could be attributed to the formation of more PbF2 and PbSO4 during the pre-treatment which tend to transform to PbO2 during the following electrowinning process. In addition, the anodic layer on anode with pre-treatment in fluoride-containing H2SO4 solution is thick and compact, and its predominant composition is β-PbO2. In summary, the pre-treatment in fluoride-containing H2SO4 solution benefits the formation of a desirable protective layer in a short time.

Electrocatalytic behaviour of Ni and NiCu alloy modified glassy carbon electrode in electro-oxidation of contraflam

The electrocatalytic oxidation of contraflam was investigated in alkaline solution on nickel and nickel–copper alloy modified glassy carbon electrodes(GC/Ni and GC/NiCu). We prepared these electrodes by galvanostatic deposition and the surface morphologies and compositions of electrodes were determined by energy-dispersive X-ray(EDX) and scanning electron microscopy(SEM). Cyclic voltammetry and chronoamperometric methods were employed to characterize the oxidation process and its kinetics. Voltammetric studies exhibit one pair of well-defined redox peaks, which is ascribed to the redox process of the nickel and followed by the greatly enhanced current response of the anodic peak in the presence of contraflam and a decrease in the corresponding cathodic current peak. This indicates that the immobilized redox mediator on the electrode surface was oxidized contraflam via an electrocatalytic mechanism. The catalytic currents increased linearly with the concentration of contraflam in the range of 0.25– 1.5 mmol/L. The anodic peak currents were linearly proportional to the square root of scan rate. This behaviour is the characteristic of a diffusion-controlled process. The determination of contraflam in capsules is applied satisfactorily by modified electrode.

Electrochemical behavior of CoCl_2 in ionic liquid 1-butyl-3-methylimidazolium hexafluorophosphate

The electrochemical behavior of CoCl2 in 1-butyl-3-methylimidazolium hexafluorophosphate (bmim]PF6) was investigated by cyclic voltammetry. The cyclic voltammograms were obtained from electrochemical measurement under different temperatures, and the reversible behavior for Co2+/Co3+ redox couple on glassy carbon electrode in bmim]PF6 was confirmed by the characteristic of the peak currents. The diffusion coefficients (about 10-11 m2/s) of Co2+ in bmim]PF6 under different temperatures were evaluated from the dependence of the peak current density on the potential scan rates in cyclic voltammograms. It is found that the diffusion coefficient increases with increasing temperature. Diffusion activation energy of Co2+ in bmim]PF6 is also calculated to be 23.4 kJ/mol according to the relationship between diffusion coefficient and temperature.

Study on Water-Soluble Organic Reducing Substances. I. Determination of Organic Reducing Substances by Differential Pulse Voltammetry

A new method was proposed for study of organic reducing substances in soils. According to the theoretical relationship between the voltammetric behaviors and reduction-oxidation reaction of reducing substances, the working conditions of differential pulse voltammetry (d.p. v.) for determining the organic reducing substances produced during the processes of the anaerobic decomposition of plant materials were established with a glass carbon electrode as working electrode, 1 M Ag-AgCl electrode with large area as reference electrode, 0.2 M NH4AC as supporting electrolyte and pH buffer solution, pulse amplitude (AE) of 25 mV, scan rate at 2 mV·S-1and scan potential ranging from -0.5 to +1.2 voltage(vs. M Ag-AgCl). The peak current proportional to the concentration of reducing substances, and the characteristic peak potential of each organic reducing substance were regarded as the quantitative and qualitative base, respectively. These results obtained under the conditions mentioned above directly reflect both the reducing intensity and capacity of the organic reducing system in soils.