Effect of applied voltage on wetting and corrosion of corundum refractory by CaO–SiO2–MgO molten slag

The wetting and corrosion behavior of the corundum substrate anode by CaO–SiO₂–MgO molten slag was investigated via the joint application of the sessile drop method with applied voltage and SEM-EDS technique. The slag drop exhibited a good wettability on the corundum substrate. The apparent contact angle at zero voltage slightly exceeded that at a 1 V applied voltage but was lower than those at 1.5 V and 2 V ones. Low applied voltage of 1 V had little effect on the corundum substrate's direct dissolution corrosion processes; high ones of not less than 1.5 V caused the electrode reaction to occur. The stirring effect of O₂ bubbles from the anode reaction aggravated the substrate's direct dissolution and physical stripping. It was found that the applied voltage could inhibit the slag penetration, and the apparent contact angle had no obvious relation with the direct dissolution thickness and penetration depth. A thin but almost continuous MgO?Al₂O₃ (MA) layer could form at the slag/substrate interface at the applied voltage of 1.5 V. These results indicate the positive effect of applied voltage on the distribution of interfacial products and the molten slag penetration in reducing the corrosion of corundum anode under certain conditions. However, when the applied voltage was too high, the vigorous electrode reaction could aggravate the direct dissolution and physical stripping of the corundum anode, and damage the continuation of the formed interface product layer with a high melting point.     

Anodic Proton Injection in Glasses

Protons were injected into glasses at high temperatures using anodes such as molten NH₄HSO₄, Pt in forming gas, and graphite in an atmosphere containing H₂O vapor. Large electric fields develop near the anode surface of the glass and create an ion-depleted region beneath the anode. The electrical conduction characteristics are attributed mainly to the motion of protons in the high-field region. The ir absorption data indicate that injected protons exist in at least 3 bonding configurations in a proton-exchanged region beneath the depleted region. The proton concentration in the exchanged region is estimated to be ∼80 to 95% of the Na concentration in the normal glass.     

Current efficiency studies for graphite and SnO2-based anodes for the electro-deoxidation of metal oxides

Studies were performed investigating the electrochemical reduction of chromium oxide (Cr₂O₃) by electro-deoxidation by utilising either a graphite anode or a tin oxide (SnO₂) based anode. Potentiostatic electrolysis was performed at 3.0 V for both a graphite and for a SnO₂-based anode, and also 2.0 V for a graphite anode. The cathode reduction purity, anode mass change, anode potential relative to a glassy carbon pseudo-reference and current efficiency were measured and compared. The key observations are that substituting a SnO₂-based anode for a graphite anode led to greater current efficiencies for electro-deoxidation. This was attributed to the lack of contamination of the melt by carbon and the lower cathode potential due to the higher anodic potential when using tin oxide based anodes for the same applied voltage. The current efficiency was also found to decrease with both anode materials when higher anode surface areas or lower current densities were used. Again this was attributed to a decrease in anodic potentials and a corresponding increase in the cathodic potential resulting in a greater number of parasitic reactions occurring at the cathode.     

Athermal electric field-induced restructuring of glass during poling

Thermal poling is a widely used method for creating glass surfaces with modified structure and altered properties by application of DC voltage. The mechanism of structural change has remained controversial, especially as poling is performed well below the glass transition temperature. Specifically, the role of Joule heating in facilitating structural transformation has remained an open question, conceivably through local heating to temperatures approaching T_g. Here, we investigate this possibility directly by in situ measurements of the local glass temperature during poling using infrared imaging. Examination near the anode region reveals only a slight temperature increase (~10°C) above the furnace temperature at the start of poling, and remains a few hundred degrees below T_g throughout. SIMS analysis revealed a ~1-µm thick alkali depletion layer next to the anode. XPS analysis of the anode, cathode, and unpoled regions shows complex changes in structure and composition including migration of alkali ions, injection of hydrogen at the anode interface, removal of non-bridging oxygen, and polymerization of the network via electrolysis. All these changes arise as a result of high electric field (~10⁶ V/cm) produced across the highly resistive depletion layer, and refutes any significant increase in the temperature by Joule heating as the cause of their creation.     

The anodized crystalline WO(3) nanoporous network with enhanced electrochromic properties

We demonstrate that a three dimensional (3D) crystalline tungsten trioxide (WO(3)) nanoporous network, directly grown on a transparent conductive oxide (TCO) substrate, is a suitable working electrode material for high performance electrochromic devices. This nanostructure, with achievable thicknesses of up to 2 μm, is prepared at room temperature by the electrochemical anodization of a RF-sputtered tungsten film deposited on a fluoride doped tin oxide (FTO) conductive glass, under low applied anodic voltages and mild chemical dissolution conditions. For the crystalline nanoporous network with thicknesses ranging from 0.6 to 1 μm, impressive coloration efficiencies of up to 141.5 cm(2) C(-1) are achieved by applying a low coloration voltage of -0.25 V. It is also observed that there is no significant degradation of the electrochromic properties of the porous film after 2000 continuous coloration-bleaching cycles. The remarkable electrochromic characteristics of this crystalline and nanoporous WO(3) are mainly ascribed to the combination of a large surface area, facilitating increased intercalation of protons, as well as excellent continuous and directional paths for charge transfer and proton migration in the highly crystalline material.     

Electrochemical durability of single-wall carbon nanotube electrode against anodic oxidation in water

The electrochemical capability of single-wall carbon nanotube (SWCNT) electrodes is investigated to establish their reliability in practical applications. Direct current (DC) voltage of +10 V is applied across the SWCNT anode and Pt cathode in water, and the electrochemical fracturing behavior of SWCNTs is analyzed using transmission electron microscopy and atomic force microscopy. A considerable number of short SWCNTs, with lengths of less than 200 nm, are observed to be electrochemically generated. This result suggests that the anodic corrosion of SWCNTs occurs even in water, a non-electrolyte liquid. Raman spectroscopy and a comparison study of the anodization behavior of SWCNTs with narrow (0.9 nm) and wide (1.8 nm) diameters indicate that the durability of narrow SWCNTs is lower than that of the wide SWCNTs.     

Advances in the control of electrophoretic process parameters to tune the ytterbium disilicate coatings microstructure

Suspensions of ytterbium disilicate in isopropanol were prepared using iodine dispersant. Their zeta potential, electrical conductivity, and pH dependence with iodine concentration is detailed. Electrophoretic deposition was performed on silicon substrates at various voltages (100-200 V) and times (until 10 minutes) and the growth dynamic was investigated. It was observed that the deposited mass reaches a maximum value for [I₂] = 0.2 g/L, and the coating microstructure becomes porous at higher iodine concentrations. Current density and voltage measurements allowed to correlate this behavior to the increase of free protons concentration in the suspension. In these conditions, it was proved that porosity increases with the increase in applied voltage, and a compaction occurs as the deposition time increases. This has been related to the coating resistance increase and subsequent decrease in effective voltage in the suspension. The denser coatings (20% of porosity) were obtained in the case of suspension without iodine, at the minimum applied voltage and for the longest deposition times.     

Pulsed electrokinetic removal of Cd and Zn from fine-grained soil

Pulsed electrokinetics studies were carried out to optimize the removal of Zn and Cd from fine-grained soils and to observe the effects of varying the pulse frequency, pulse time ratio (on/off), and DC voltage gradient. Existing forms of heavy metals in the soil matrix were determined using a sequential extraction method. The strongly bound fraction (bound to organic matter and residuals) that is difficult to remove from the soil matrix comprised 74 and 62% of the total Zn and Cd, respectively. In the electrokinetic remediation experiments, MgSO₄ was employed to increase the ionic strength of the soil for 2 weeks. Transportation of heavy metals was influenced by the frequency, pulse ratio, and the voltage gradient of the pulsed electric field. Extraction efficiency of Zn and Cd near the anode was correlated positively with the voltage gradient at a given pulse and ratio. A high pulse frequency (1,800 cycles/h) enhanced the removal efficiency of the heavy metals compared to a low pulse frequency (1,200 cycles/h) at a supplied voltage gradient of 1 V/cm. Although pulsed electrokinetics was more effective in extracting and desorbing ions near the anode than conventional electrokinetics, its ability to transport heavy metals from the anode to the cathode was relatively small. Total removals with pulsed electrokinetics were 21–31% for Zn and 18–24% for Cd. In summary, pulsed electrokinetics can enhance removal efficiency of heavy metals and is beneficial with regard to electrical energy consumption.     

Low-Temperature Electrochemical Synthesis of ZrO2 Films on Zirconium Substrates: Deposition of Thick Amorphous Films and in situ Crystallization on Zirconium Anode

The feasibility of synthesizing crystalline ZrO₂ films at low temperatures was evaluated using an electrochemical method. Anodization of zirconium-metal substrates in tetraethyl ammonium hydroxide (TEAOH) solutions under constant applied voltage conditions at ∼25° and ∼100°C was investigated. The chemistry and microstructure of the anodic oxide films deposited on the zirconium-metal substrates under the above conditions were characterized using X-ray diffractometry and scanning electron microscopy. The results indicated that, with sufficiently high applied voltages (in the range of 300 V) at pH ∼9.5, the initial dissolution of the zirconium anode resulted in the local saturation of the electrolyte solution with Zr⁴⁺, forming Zr(OH)⁻₅, which deposited electrophoretically on the anode as a thick, gelatinous film at 25°C. Similar treatments at 100°C resulted in an in situ crystallization of Zr(OH)₄ gel to monoclinic ZrO₂.     

降温速率对浮法硼硅酸盐玻璃下表面渗锡的影响

研究锡槽中降温速率对浮法硼硅酸盐玻璃下表面渗锡的影响.采用不同降温速率制备浮法硼硅酸盐玻璃,用电子探针测试浮法硼硅酸盐玻璃在1 250～650℃温度范围内不同降温速率情况下表面渗锡分布情况.研究结果表明:浮法成形过程中硼硅酸盐玻璃渗锡的深度可达到40.0μm左右,并且在1 050℃以上的高温段锡离子以深度方向扩散为主,在1 050℃以下的低温阶段锡离子主要在玻璃的近表面富集.随着时间的延长浮法硼硅酸盐玻璃近表面的渗锡量增加,而深度大于7.0μm以上的内部的渗锡量不会由于时间的延长而累加,只与温度有关.在浮法成形过程中渗锡曲线会在1 050℃左右,距玻璃表面15.0μm处出现卫星峰,但最终在低温时该卫星峰会由于逆扩散而消失.     

浮法玻璃下表面渗锡的X射线光电子谱

利用X射线光电子谱仪（X-ray photoelectron spectroscopy,XPS）对国内外浮法玻璃样品（样品A和样品B）下表面渗锡情况进行了对比分析。结果表明：在浮法玻璃下表面900nm范围内,2种样品中的锡离子在渗锡面均以Sn^0,Sn^2＋,Sn^4＋ 3种价态存在,Sn^2＋在整个渗锡量中均占最大比例。在近表面区,渗锡均以Sn^2＋态为主,Sn^0和Sn^2＋含量之和均占到总渗锡量的90％以上,且样品A渗锡量远远高于样品B的渗锡量。样品A的不同锡离子相对含量沿深度变化较大,而样品B的不同锡离子相对含量沿深度变化小于1％。结合扫描电子显微镜形貌观察可知：钢化虹彩现象是由钢化处理中,Sn^2＋转变为Sn^4＋的氧化反应导致的体积膨胀引起的。在该反应过程中单胞体积增大3％。综合XPS与钢化虹彩实验结果可知,XPS分析可以有效而精确地提供浮法玻璃中锡的价态以及含量信息。     

Preparation of nanoporous tin oxide by electrochemical anodization in alkaline electrolytes

This paper reports the creation of a porous tin oxide structure by means of anodization of pure tin foil in alkaline NaOH solutions. The tin oxide film formed is polycrystalline and possesses an irregular nanoporous structure with a porosity of ∼50%. The average pore size is ∼37 nm with a size distribution from 10 to 60 nm irrespective of anodization conditions, including the applied voltage (5–15 V) and NaOH concentration (0.125–1 M). The BET specific surface area of this porous structure is 79.6 m²/g. Linear relationships are observed for the dependence of tin oxide layer thickness on anodization time, applied voltage, and NaOH concentration. A thermodynamic model is established to explain the pore growth mechanism in the anodization process.     

DCMFC两腔液量变化与产电性能的关系

随着DCMFC产电周期的增加,阴阳极间的液位差明显增加。为解析此现象,从蒸发、渗透压、生物代谢及电场角度考察了质子和水的传递行为,研究了产水与电池性能的关系。结果表明：360 h内蒸发、渗透压引起的液量变化少于0.50 ml（液面降低0.5 mm）;断路312 h,阳极代谢气体使PEM形变凸向阴极,阳极液减少6.20 ml（下降6.5 mm）,阴极液增加10.75 ml（上升11.2 mm）,两腔液位差达17.7 mm;通路下,除膜的形变,水合质子被电渗透到阴极并还原成水,312 h内阳极液减少10.70 ml（下降11.1 mm）,阴极液增加17.00 ml（上升17.7 mm）,两腔液位差达28.8 mm,且产水量随电压的增大而增加。研究表明,生物代谢及电渗透对两腔液量影响较大,产水量可表征质子传递率。经计算该系统质子传递率大于54%,为评判产电效率提供了简便依据。     

Enhancement of COD-Nutrients Removals and Filterability of Secondary Clarifier Municipal Wastewater Influent Using Electrocoagulation Technique

The present work studied experimentally the variations of some characteristics of the mixed liquor solution in wastewater treatment plants (WWTPs) under the effect of electrocoagulation (EC) technique. Unlike conventional methods, electrocoagulation was performed using cylindrical perforated iron electrodes to achieve a good distribution of the applied DC field onto the municipal wastewater. Effects of electrocoagulation time, applied voltage gradient, and aeration on the mixed liquor characteristics were considered. The study figured out the dependency of the local pH and oxidation potential reduction (OPR) values, near anode and cathode on these operational conditions. It was found that electrocoagulation process reached steady state conditions in no more than 60 minutes. At high voltage gradient (6 V/cm), the steady removal efficiencies of COD and nutrients exceeded 89%. While aeration showed moderate influence on removal efficiencies and wastewater sludge filterability, it significantly affected the pH and ORP near the electrodes especially at the low voltage gradient. Results also indicated that the sludge filterability was improved notably by increasing the voltage gradient to have minimal levels of specific-resistance to filtration (SRF).     

Desulfurization of gasoline by a new method of electrochemical catalytic oxidation

A new deep desulfurization process for gasoline was obtained by means of electrochemical catalytic oxidation with an electrochemical fluidized-bed reactor on particle group anode. The particle group anode was activated carbon-supported cerium dioxide (CeO₂/C), and the electrolyte was aqueous cerium nitrate solution, and copper pillar was cathode in the electrochemical reactions. The CeO₂/C particle group anode could remarkably accelerate the electrochemical reaction rate and promote the electrochemical catalysis performance for the electrochemical desulfurization reaction. Thermodynamics feasibility analysis clarified that the theoretical decomposition voltage ranged from 0.1–0.5 V in pure acid electrolyte system and desulfurization reactions could not spontaneously carry out, but the reactions were spontaneous when aqueous cerium nitrate solution serves as electrolyte. And the rule of the gasoline desulfurization by the means of electrochemical catalytic oxidation was investigated. The experimental results indicated that the optimal desulfurization conditions were as follows: the cell voltage, concentration of the Ce³⁺ ions, feed volume flow rate and the CeO₂ percentage by weight were 3.2 V, 0.08 mol l⁻¹, 300 ml min⁻¹ and 5.0 wt%, respectively. Under these conditions the concentration of sulfur in gasoline was reduced from 310 to 50 parts per million by weight (ppmw). Based on these experimental results, a mechanism of indirect electrochemical oxidation was also proposed.     

HCJY98-6型浮法玻璃虹彩检验装置及技术

浮法玻璃钢化虹彩是普遍存在的质量问题.HCJY98-6型浮法玻璃虹彩检验装置能现场快速检测,以便及时对锡槽工况和窑封状况进行调整,保证浮法玻璃的质量,避免虹彩的产生.对生产高质量浮法玻璃有指导意义.     

Electrocatalytic oxidation of cyclohexanol on a nickel oxyhydroxide modified nickel electrode in alkaline solutions

Electrocatalytic oxidation of cyclohexanol was investigated with cyclic voltammograms, linear galvanic voltammograms and chronoamperometric responses on a nickel oxyhydroxide modified nickel (NOMN) electrode prepared by cycling the potential of a nickel electrode in the potential range of 0.1 V to 0.6 V (vs SCE) in alkaline solutions. It was found that cyclohexanol was oxidized by NiOOH generated with further electrochemical oxidation of nickel hydroxide during the anodic potential sweep. One of the products of the reaction between cyclohexanol and NiOOH was Ni(OH)₂ which was subsequently oxidized to NiOOH on the anode. This resulted in the appearance of a new anodic peak in cyclic voltammograms compared with the absence of cyclohexanol and this anodic peak strongly depends upon potential scan rates and cyclohexanol concentrations. In addition, the presence of cyclohexanol in NaOH solutions also lead to the decrease of anodic potentials in linear galvanic voltammetric responses and the increase of current densities in chronoamperometric curves. Results showed that the oxidation of cyclohexanol on the NOMN electrode follows the catalytic reaction mechanism.     

Electrophoretic deposition studies of Ba(Zr-Ce-Y)O3 ceramic coating

Electrophoretic deposition (EPD) is now a well established colloidal processing technique which uses electrophoresis mechanism for the movement of suspended charged particles in a suspension in the presence of an electric field. In this work, electrophoretic deposition of BaZr_0.4Ce_0.4Y_0.2O_3-δ (BZCY) in ethanol medium was performed under different conditions on both conducting and non-conducting (porous anode) substrate without using any external additives in a suspension bath. Process parameters such as deposition time, voltage, and rate of deposition of suspended particles were studied under various conditions. Green coating deposited under different potential (30, 50, and 70V) was uniform and crack free, even at extended time of deposition. Surface roughnesses have also been evaluated to correlate it with deposition conditions. It is also found that the rate of deposition on conducting substrate was higher as compared to that on non-conducting substrate (anode). XRD studies of the calcined powder and coating exhibit an expected simple cubic perovskite structure. The deposition yield increases linearly with voltage for each deposition time for both conducting and non-conducting substrates. The coating on non-conducting porous anode heat treated at 1500°C for 2 hours was dense and well adherent to the anode substrate. A film thickness of about 13 μm was obtained at 70V. Such dense BZCY electrolyte coating on BZCY+NiO anode (Half cell) could be well utilized for fabrication of proton conducting SOFC single cell by applying suitable cathode layer on electrolyte film.     

Electrical properties of soda lime silica glass using electrolysis at 600°C between molten tin and lead electrodes

The electrolysis of a soda lime silicate glass has been studied using liquid metal electrodes of lead and tin at 600°C and voltages up to 300 V in a N₂/10% H₂ atmosphere. The behaviour observed was dependent upon the applied voltage. At less than 2.5 V, the square of the current was inversely proportional to the electrolysis time but at higher voltages, up to 100 V, the current was inversely proportional to the time for periods up to 300 ms. At voltages greater than 100 V, the behaviour could not be expressed by a simple equation, the currents passing were high and finally, electrical breakdown occurred at 300 V.It is proposed that in the range 2.5 to 100 V the glass behaves as a dielectric with charge separation in a thin surface layer. At higher voltages, near breakdown, the heat liberated at the surface is sufficient to disrupt the surface layer and then the conduction is governed by the electrical properties of the bulk glass.     

A new modified multiwalled carbon nanotube paste electrode for quantification of tin in fruit juice and bottled water samples

In this paper, a new modified multiwalled carbon nanotube electrode is reported for anodic stripping voltammetry quantification of tin. The electrode is based on the use of N-Nitrozo-N-Phenylhydroxylamine (cupferron) and multiwalled carbon nanotube. The influence of supporting electrolytes, deposition time, and applied potential on the sensitivity of electrode were investigated. The detection limit was 0.12 ng/ml and the RSD at a concentration level of 50 ng/ml, was 1.5%. The electrode has been applied for the determination of tin in fruit juice and bottled water with the satisfactory results.