交流阻抗技术在化学清洗中的应用

将阻抗概念引入化学清洗技术中,采用交流阻抗技术研究化学清洗过程中所涉及的电化学电池及其行为,建立了电极体系在清洗过程中的等效电路,推导了化学清洗电化学过程的交流阻抗复平面图,然后从这些模型中解析出相关的化学信息,并用于指导实际的生产工艺,为化学清洗技术的发展提供了新的思路.     

Electrochemical production of ferrate(vi) using sinusoidal alternating current superimposed on direct current. Pure iron electrode

The current yield for the anodic oxidation of a pure iron (99.95%) electrode to ferrate(VI) ions in 14 M NaOH between 30 and 60 °C using a sinusoidal alternating current (a.c.) at amplitudes in the range 38–88 mA cm–2 and frequencies in the range 0.5 mHz to 5 kHz superimposed on direct current (d.c.) of 16 mAcm–2 was measured under conditions of bubble induced convection in a batch cell. The current yield for ferrate(VI) synthesis exhibited a complex dependence on temperature and a.c. frequency, but generally a maximum was observed in a frequency range 2–50Hz depending on the a.c. amplitude. A global maximum current yield after 180 min of electrolysis of 33% was reached at the following conditions: a.c. amplitude of 88 mA cm–2, a.c. frequency of 50 Hz and temperature of 40 °C. At the optimum conditions the highest d.c. electrolysis yield was 23%. Thus, operation with the a.c. component leads to an increase in the yield by 43% with respect to d.c. electrolysis alone.     

交、直流交替氧化对3005铝合金电解着色的影响

采用交、直流交替氧化的方法,改变3005铝合金在硫酸介质中阳极氧化膜的结构与组成,探讨其对膜层电解着色性能的影响。结果表明,交、直流氧化的顺序及相关电解着色参数对电解着色膜性能产生明显的影响。最佳氧化及着色工艺条件为:直流氧化电流密度1～2A/dm2,交流氧化电压15～20V,着色电压5～7V,着色温度20～30℃,着色时间2～7min。由此可获得浅茶色、桃红色、朱红色、紫黑色等一系列具有高装饰性的铝阳极氧化着色膜。     

镁合金交流电氧化工艺研究

在氢氧化钠、硼酸盐、硅酸盐及有机胺的混合溶液中,用普通交流电对AZ91D镁合金进行电解氧化。研究了溶液组成、氧化电压、温度和时间等对镁合金电解氧化的影响。最佳工艺条件为:30g/LNaOH,25g/LNa2B4O7,50g/LNa2SiO3,40mL/L三乙醇胺,交流电压130～160V,时间10min。在最佳工艺条件下,镁合金表面形成了一层致密光滑的类陶瓷膜层,该膜层具有良好的耐蚀性能。     

Electrochemically deposited Ni + WC composite coatings obtained under constant and pulsating current regimes

A series of Ni + WC composite coatings were obtained by electrodeposition on a rotating disc electrode (RDE) from a commercially available Watts bath containing additives for brightness and smoothing and insoluble WC particles, using either constant or pulsating current. It was shown that the amount of WC embedded in the coating could vary from a few percent to over 80% depending on the rotation rate and the current density of deposition. Higher amounts (over 50 mass%) of embedded WC particles could be obtained only at rotation rates higher than 2000 rpm. It was also shown that the concentration of insoluble WC particles in the Watts bath has no significant influence on the amount of WC embedded in the coating, enabling the use of dilute mixtures (2 mass% of WC in the solution). At higher amounts of embedded WC particles, rough deposits were obtained with the WC particles being mostly incorporated in agglomerates of different sizes (from about 50 m to about 100 m). It was also shown that under the same conditions of electrodeposition, higher amounts of embedded WC particles could be obtained from solutions containing smaller particles.     

Synthesis of yttria precursor nano-powders using a symmetrical alternating current assisted precipitation method

Symmetrical alternating current (SAC) was applied during yttria precursor nano-powder precipitation. The effects of SAC on the morphology and grain size of the yttria precursor were investigated via scanning electron microscopy (SEM) and X-ray diffraction (XRD). It was found the precursor to be transformed from irregular platelets/spheres to uniform spheres due to the SAC vibration effect. High frequency and density of SAC exerted greater influence on the morphology and grain size of the yttria precursor than weaker one.     

IEC三相交流系统短路电流计算的使用（待续）

介绍ＩＥＣ三相交流系统短路电流计算方法的重点和短路电流热效应计算，并用例题介绍其具体使用情况。     

Electrochemical drilling using alternating current

The attraction of using a.c. compared with d.c. is the opportunity it offers to simply transform normal workshop power supply down to a sensible potential value for electrochemical machining without having to incorporate rectifying equipment. Its success will normally depend on the ability to find tool materials which are not affected by electrolytic action while at positive potential and on the normal 50/60 Hz mains frequency being satisfactory. However, the possible use of higher frequencies should not be ruled out for small area work where total current can be in 10 s rather than 100 or 1000 s of amps; a high frequency oscillator could then be a sensible source of power. This paper is based on experimental work carried out using easily obtained tool electrode materials and illustrates the practical feasibility of a.c. for industrial use.     

环境友好型AZ31B镁合金交流微弧氧化的表征(英文)

研究了一种新的AZ31B镁合金交流电微弧氧化(MAO)工艺,采用了对环境更加友好的含硅酸盐的稀碱溶液作为电解质。结果发现氧化过程分为2个阶段,膜厚与微弧氧化时间呈抛物线关系。形貌观察表明,微弧氧化膜由一个致密层和一个多孔层组成。致密层的厚度约占整个膜厚的40%,膜表面的20%均匀分布着直径1~3μm的孔。动电位极化测量显示,该新型微弧氧化膜的耐蚀性有明显提高,腐蚀电流降低了2个数量级,而自腐蚀电位正移了0.07V。盐雾试验结果同样证实微弧氧化膜的耐蚀性有大幅度提高。     

Effects of alternating and direct current in electrocoagulation process on the removal of fluoride from water

BACKGROUND: When direct current (DC) is used in electrocoagulation processes, an impermeable oxide layer may form on the cathode and corrosion of the anode may occur due to oxidation. This prevents effective current transfer between the anode and cathode, so the efficiency of the electrocoagulation process declines. These disadvantages of DC have been reduced by adopting alternating current (AC). The main objective of this study is to investigate the effects of AC and DC on the removal of fluoride from water using an aluminum alloy as anode and cathode. RESULTS: Results showed that removal efficiencies of 93 and 91.5% with energy consumption of 1.883 and 2.541 kWh kL^?1 was achieved at a current density of 1.0 A dm^?2 and pH 7.0 using an aluminum alloy as electrodes using AC and DC, respectively. For both AC and DC, the adsorption of fluoride fitted the Langmuir adsorption isotherm. The adsorption process follows second‐order kinetics and temperature studies showed that adsorption was exothermic and spontaneous in nature. CONCLUSIONS: The aluminum hydroxide generated in the cell removed the fluoride present in the water and reduced it to a permissible level thus making it drinkable. It is concluded that an alternating current prevents passivation of the aluminum anode during electrocoagulation and avoids the additional energy wasted due to the resistance of the aluminum oxide film formed on the anode surface. Copyright © 2010 Society of Chemical Industry     

Effects of alternating current (AC) and direct current (DC) in electrocoagulation process for the removal of iron from water

In practice, direct current (DC) is used in an electrocoagulation processes. In this case, an impermeable oxide layer may form on the cathode as well as corrosion formation on the anode due to oxidation. This prevents the effective current transfer between the anode and cathode, so the efficiency of electrocoagulation processes declines. These disadvantages of DC have been diminished by adopting alternating current (AC) in electrocoagulation processes. The main objective of this study is to investigate the effects of AC and DC on the removal of iron from water using zinc as anode and cathode. The results showed that the optimum removal efficiency of 99.6% and 99.1% with the energy consumption of 0.625 and 0.991 kWh kL^?1 was achieved at a current density of 0.06 A dm^?2, at pH of 7.0 using AC and DC, respectively. For both AC and DC, the adsorption of iron was preferably fitting Langmuir adsorption isotherm, the adsorption process follows second order kinetics and the temperature studies showed that adsorption was exothermic and spontaneous in nature. © 2011 Canadian Society for Chemical Engineering     

Electrochemical dissolution of mild steel by alternating current

The electrochemical dissolution of mild steel in hydrochloric acid and sulphuric acid by a.c. has been studied. It has been found that with sine wave a.c. (50 Hz) the dissolution efficiency increases with increase in concentrations of the acids and decreases with the progress of electrolysis. As current density increases an initial increase in the efficiency was noticed; but as current density increases further, the efficiency falls. With square wave a.c. of low frequency (0.5 Hz), the dissolution efficiency increases with increasing concentrations of the acids and also with increasing frequency. However the efficiency decreases with increasing current density and time of electrolysis.     

Fabrication of nano-In2O3 phase junction by pulse alternating current synthesis for enhanced photoelectrochemical performance: Unravelling the role of synthetic conditions

Rational design and controllable synthesis of materials with improved activity and stability remains one of the key challenges to be addressed in the field of photoelectrochemical water splitting. In this work, a series of nano-In₂O₃ (c- and c/rh-In₂O₃) with tunable cubic-to-rhombohedral phase ratios was obtained via pulse alternating current electrosynthesis followed by air annealing. The physicochemical characterization of In₂O₃ using XRD, FESEM, TEM, XPS, Raman, UV–vis DRS and BET techniques along with photoelectrochemical test indicate that synthetic conditions greatly influence on structural, morphological and optical properties. The c/rh-phase ratio was feasibly controlled by altering the nature of the electrolyte (LiCl, KCl, NaCl and Na₂SO₄) without adding any organic additives. The c/rh-In₂O₃ synthesized using NaCl aqueous electrolyte shows enhanced photoelectrochemical activity (0.35 mA/cm² at 1.23 V vs RHE) and photoconversion efficiency (0.09%) as well as excellent long-term stability (over 7 h). The improved performance of the c/rh-In₂O₃ results from the constructing the well-defined phase-junction with optimal phase ratio (72% c-/28% rh-) and the high oxygen deficiency providing a synergistic effect between rh-In₂O₃ and c-In₂O₃ for more efficient separation and transfer of photogenerated charges. These results lead to a better understanding of designing metal oxide phase-junctions for photoelectrochemical applications.     

Electrochemical dissolution of nickel in sulphuric acid by alternating current

The electrochemical dissolution of nickel in sulphuric acid by alternating current has been studied. Experiments with sine wave a.c. (50 cps) have shown that the dissolution efficiency increases with increase in concentration of sulphuric acid as well as current density. However, the dissolution efficiency increases with increase in concentration of sulphuric acid but decreases with increase in current density when square wave type a.c. of low frequency (0.5 cps) is used. Increase of frequency of square wave a.c. increases the dissolution efficiency.     

脉动热管技术研究进展

脉动热管作为一种新型热管技术,具有结构简单、成本低廉和传热性能好,适应性强的优点,尤其在微电子散热、冷冻技术以及航空航天热控技术中郝极具应用潜力.本文介绍了脉动热管的结构及其工作原理,在综述有关脉动热管实验、数值模拟、实际应用的基础上,指出其今后的研究方向是脉动热管的多样化、微小化、实用化.     

The effects of alternating current electrocoagulation on dye removal from aqueous solutions

The main goal of this study is to investigate the effects of alternating current (AC) on dye removal from aqueous solutions by electrocoagulation (EC). An EC system with parallel-connected aluminium electrodes was operated in batch mode. Two different aqueous dye solutions were used: one was obtained from Dianix Yellow CC (DY) and the other was obtained using Procion Yellow (PY). The experiments employing direct current (DC) were carried out using a DC power supply. The AC experiments were conducted using rectangular wave, which is produced with an adjustable time relay connected to the output of DC power supply. This current is called alternating pulse current (APC) in order to refer AC system in this study. Total organic carbon (TOC) and dye removal efficiencies were measured to assess treatment efficiency. Operating cost was calculated for both power supply systems and alternating pulse current was found superior to direct current for the treatment of reactive and disperse dyes used in this study.     

不锈钢电化学着蓝色膜工艺研究

使用直流电源,研究了0Cr18Ni9不锈钢表面电化学着蓝色膜工艺。探讨了电流密度、着色时间和温度对着色膜色彩的影响。使用擦拭法测试了膜的耐擦拭性。试验了如何提高色彩的稳定性的方法。结果表明,蓝色膜的最佳电流密度控制在0.2 A/dm-2比较合适。温度和时间范围分别为40～50℃和5～15 min。着色膜具有较好的耐擦拭性和很好的附着性能。可通过调节着色液温度和成分来提高色彩的重复性。     

Electrochemical dissolution of metals of the platinum group by alternating current

The electrochemical dissolution of metals of the platinum group in acid solutions using an alternating current is investigated. It is shown that this is an efficient and promising method for the production of pure noble metal salts, and for the analysis and extraction of small amounts of noble metals from waste and poor ores. The production of pure bromides and chlorides of gold and rhodium is particularly efficient because their rates of dissolution are high. The mechanism of the influence of the alternating current on the metal/electrolyte interface is also discussed.     

New opportunities for the study of organic films applied on metals for corrosion protection by means of alternating current scanning electrochemical microscopy

A new method for the investigation of the inhibition efficiency against corrosion by organic films adsorbed on metals based on the measurement of Z-approach curves by AC-SECM is proposed. Preliminary measurements conducted on four copper-inhibitor systems exposed to aqueous solutions support that a characteristic frequency can be defined, which corresponds to the frequency of the AC potential signal applied to the SECM tip for which a transition between negative- and positive-feedback behaviours is observed in the approach curves. From the shift of this characteristic frequency towards higher values, the enhancement of the corrosion protection efficiency of the inhibitor system can be established. Furthermore, the effects of inhibitor nature, concentration, and pre-treatment duration for the formation of the surface films, can be readily investigated.     

Simplified model to predict the effect of the leakage current on primary and secondary current distributions in electrochemical reactors with a bipolar electrode

A simplified mathematical model to calculate the current distributions in bipolar electrochemical reactors is proposed. The current distributions are deduced from a combination of the voltage balance in the reactor with a voltage balance including the electrolyte inlet and outlet. Thus, equations to predict the effect of geometric and operational variables on the current distributions at the electrodes are reported. The parameters acting upon the current distributions were lumped into two dimensionless variables and their effects on the current distributions are discussed. The primary current distributions are obtained as a limiting case. Comparisons between calculated and experimental primary current distributions are reported.