用于混凝土中钢筋腐蚀监测的固态Ag/AgCl参比电极的制作及其性能

为了制备可用于混凝土中钢筋腐蚀监测的参比电极,先在三电极体系下采用恒电流阳极氧化法获取Ag/Ag Cl探针,再通过凝胶电解质封装制备了固态Ag/Ag Cl参比电极。将其用于碱性混凝土孔隙液中,研究了其Nernst响应特性和电位稳定性,并探讨了其抗各种环境因素(p H值、SO2-4、温度、电化学极化)干扰的能力。结果表明:固态Ag/Ag Cl参比电极具有良好的Nernst响应;当p H值小于12时,p H值对参比电极电位影响较小,当p H值大于12时p H值每增加1,电极电位下降约50 m V;电极的温度响应特性与抗SO2-4干扰和抗极化能力较好,适用于混凝土中钢筋腐蚀的监测。     

二氧化锰参比电极的制作及其性能评定

参比电极对检测钢筋混凝土中钢筋的电位至关重要,而应用于混凝土中的进口高性能参比电极的成本极高.为此,仿制了一种二氧化锰参比电极,并用常规电化学方法对其电位稳定性能进行测试.结果表明:在17.8 ℃、pH值为13.98的模拟孔隙液[0 6 mol/L KOH 0.2 mol/L NaOH 饱和Ca(OH)2]中,二氧化锰电极的电位稳定在60～80 mV,单个电极的电位波动不超过±5 mV; 10 μA电流阴、阳极极化时,电位波动不超过10 mV;温度变化时,电极电位变化小,可恢复.仿制的电极与国外商业二氧化锰参比电极的性能基本接近.     

银/氯化银电极用于监测混凝土中氯离子含量的研究

采用干湿循环渗透法,通过实验室制备的银/氯化银电极来监测混凝土中的氯离子含量,测试了电极的响应性能和长期稳定性,研究了总氯离子含量与自由氯离子含量之间、总氯离子含量与电位之间的关系。结果表明:银/氯化银电极电位能比较好地监测到混凝土中氯离子含量变化的过程,具有良好的长期稳定性能。总氯离子含量随自由氯离子含量的增加而增加,两者之间呈现幂函数的规律。总氯离子含量随电位上升而下降,两者之间呈指数函数的规律。     

氯盐侵蚀下铜矿渣混凝土高温后内部钢筋锈蚀规律

为探究高温及铜矿渣细骨料对混凝土中钢筋锈蚀模式的影响规律,对不同铜矿渣置换率的混凝土试件进行高温试验,然后采用干湿循环浸泡法对试件进行人工加速氯离子侵蚀试验,并利用电化学方法测量自然电位值以监测混凝土内部钢筋的锈蚀情况,最后测量混凝土内部氯离子含量及钢筋锈蚀率。结果表明：自然电位法可以较好地反映试件内部钢筋的实际锈蚀情况;高温破坏了混凝土抗氯离子侵蚀性能,从而导致混凝土试件中的钢筋锈蚀程度随经历温度的升高而增大;此外,高温下铜矿渣自身较大的膨胀变形及冷却后与水泥净浆间不协调收缩的综合作用进一步破坏了混凝土微结构,使钢筋锈蚀率随着铜矿渣置换率的提高而增大;最后建立了氯盐侵蚀下铜矿渣混凝土高温后内部钢筋锈蚀深度拟合公式。     

全固态参比电极的制备及其在钢筋腐蚀监测中的应用

钢混结构中钢筋的腐蚀是影响结构耐久性的重要因素，腐蚀可以造成钢筋本身力学性能以及钢筋与混凝土粘结性能的劣化，这将严重影响钢混结构的承载力及服役寿命。基于电化学方法进行腐蚀监测的腐蚀传感器中通常需要应用参比电极为监测方法提供研究电极的电位，然而传统的参比电极由于其使用寿命有限从而限制了其在实际工程中的应用。制备了一种新的能够满足混凝土中钢筋腐蚀监测用的全固态参比电极。在水泥砂浆中应用动电位扫描的方法对钢筋的腐蚀进行了研究．研究结果表明，ASSRE的电位稳定，应用全固态参比电极能够得到理想的动电位扫描曲线。     

混凝土表面硅烷处理对冻融、氯离子侵蚀后钢筋锈蚀的影响

为研究冻融损伤环境下硅烷表面防护处理对钢筋混凝土内部钢筋锈蚀的影响,并为硅烷防护技术在恶劣环境下的应用提供参考,对带钢筋普通混凝土试件进行硅烷表面防护处理,通过冻融循环试验、氯离子侵蚀试验,在不同氯离子腐蚀龄期,利用半电池电位法测定钢筋半电池电位、利用线性极化法测定腐蚀电流密度,定量分析了不同冻融损伤下,不同硅烷表面涂覆量对混凝土内部钢筋锈蚀的影响。结果表明:冻融损伤后对混凝土进行硅烷防护处理可有效降低钢筋的半电池电位值和腐蚀电流密度,减小钢筋锈蚀概率,对混凝土有较好的防护作用。     

水泥基材料中钢筋脱钝临界氯离子浓度的加速测试装置及方法

本工作结合氯离子电迁移系统和电化学测试系统，研发了一种新型的水泥基材料中钢筋脱钝临界氯离子浓度的加速测试装置，分别测试了混凝土和砂浆中钢筋脱钝过程的开路电位、极化电阻和腐蚀电流密度的变化规律，提出了水泥基材料中钢筋脱钝的量化判别方法，并测试了混凝土和砂浆中钢筋脱钝的临界氯离子浓度。分析结果表明，利用所研发的临界氯离子测试装置不仅可以通过电迁移方式加速氯离子在水泥基材料中的传输、缩短试验测试周期，而且能够通过量化判别准则判别试件中钢筋测试端面是否发生脱钝，避免传统测试方法采用钢筋环面作为测试工作面、根据腐蚀电化学参数的特定取值或变化规律定性判断钢筋是否脱钝造成的测试误差。     

Ag/AgCl氯离子传感器在混凝土中的应用

尝试将试验室制作的Ag/AgCl氯离子传感器用于混凝土中测试,验证该传感器应用于混凝土结构中的可行性。测试了传感器在混凝土试件中的长期稳定性,建立了传感器在混凝土中的线性响应方程,并通过加速氯离子渗透的方式对建立的线性方程进行了验证。试验结果表明,传感器在混凝土试件中可以长期稳定有效地工作,85d电位波动25mV,传感器在氯离子掺量相同的试件中电位响应一致性良好;通过建立的线性方程计算得到的电位响应值与实测电位响应值符合得很好,所建立的方程与试件水胶比水平无关,与氯离子的引入方式无关,是适用于混凝土结构的比较准确的线性方程。通过该方程的建立即可实现使用该传感器监测混凝土结构中的氯离子分布,达到钢筋锈蚀提前预警的目的。     

热处理对碳纤维电极性能的影响

对碳纤维电极进行了热处理,探究其作为水下电场探测电极性能的变化。选择日本东丽公司生产的3K规格的T300碳纤维作为原料,选择445,465和485℃3个温度在马弗炉中进行热处理,获得获得具有活性的碳纤维电极。利用电化学工作站、低噪声微弱信号放大装置对电极的电化学性能及自噪声水平进行测量分析,讨论了不同温度热处理后电极电位稳定时间、极化性能以及电化学噪声达到最佳性能的速度。结果表明,热处理温度的提高能显著提高电极在海水中的电位稳定性、抗极化性能及电极自噪声稳定速度。为制备出可快速部署使用电场探测电极进行了有益的探索。     

海洋环境下混凝土中钢筋锈蚀机理及监测技术概述

2014年我国由于腐蚀产生的损失约为21 278亿元,占国家GDP的3.34%。海洋环境中氯离子渗透至混凝土内部导致钢筋锈蚀是海洋环境下混凝土结构损伤的重要原因。海洋不同腐蚀区域的离子浓度、氧气浓度及海水干湿循环作用时间各不相同,这使得海洋不同腐蚀区域中暴露混凝土的氯离子传输速度和分布规律、钢筋锈蚀产物及锈蚀模式、钢筋锈蚀速率存在显著差异。其中海洋浪溅区和高潮位区域因氧气充足、海水干湿循环作用剧烈及浪溅作用导致钢筋混凝土更易破坏。钢筋锈蚀产物体积是原始体积的2~6倍,持续增加的锈蚀产物将导致混凝土开裂、保护层剥落并进一步加速钢筋锈蚀;考虑钢筋非均匀锈蚀、锈蚀产物填充效应、钢筋及混凝土性能的钢筋混凝土锈胀开裂模型将更加精确。根据海洋不同腐蚀区带特点、钢筋混凝土性能及受荷情况,建立不同腐蚀区域中混凝土的氯离子传输模型,钢筋锈蚀速率模型和混凝土锈胀开裂模型有助于准确预测海洋环境下钢筋混凝土的服役寿命。 通过对混凝土中钢筋锈蚀的检测与监测有助于实时了解混凝土的服役状态。采用线性极化、电化学噪声和电化学阻抗谱等电化学方法可以较好地检测钢筋锈蚀状态、获得混凝土中钢筋的锈蚀速率。基于电化学原理开发的阳极梯和环形电极、基于钢筋锈胀应力测试的光纤监测技术以及基于数字图像技术获得混凝土中钢筋锈蚀应力应变场,有助于实现对混凝土中钢筋锈蚀的监测,并且部分已应用于海洋工程。相比于普通钢筋,锈蚀钢筋的导电率和导磁率均显著降低,采用电磁感应原理开发钢筋锈蚀装置实现了暴露在海水中的普通钢筋和耐蚀钢筋磁通量变化值与钢筋质量损失线性关系的建立。这也为更精确监测混凝土中钢筋锈蚀全过程、实现混凝土中钢筋锈蚀源定位及损伤程度识别提供可能。因此,综合利用氯离子、pH微电极等实现混凝土内部微环境监测,开发先进的钢筋锈蚀监测传感器实现混凝土中钢筋锈蚀源和锈蚀速率监测,通过图像监测技术实现钢筋锈蚀诱导混凝土开裂过程监测。综合上述措施将实现对钢筋混凝土结构腐蚀的全过程监测,并为海洋钢筋混凝土服役寿命预测模型的验证与修正提供依据,同时为海洋环境混凝土的耐久性评估系统提供预警机制。     

In situ measurement of Cl- concentrations and pH at the reinforcing steel/concrete interface by combination sensors

This paper presents an in situ, nondestructive method of monitoring Cl- concentrations and pH values at the steel/concrete interface. The Ag/AgCl electrodes prepared by the electrochemical anodization and the Ir/IrO2 electrodes prepared by thermal oxidation in carbonate served as Cl- concentration and pH sensors, respectively. The potentiometric response of the Ag/AgCl electrode to the logarithm of Cl- concentrations ranging from 1 x 10(-4) to 2 M in saturated Ca(OH)2 solution simulating the inner electrolytic medium of concrete shows good linearity. The Ir/IrO2 electrode also exhibits an ideal Nernstian response in the range of pH 1-14. The Ag/AgCl and Ir/IrO2 electrodes were combined into a multiplex Cl-/pH sensor, and the sensor was embedded in concrete close to the steel/concrete interface to realize an in situ and long-term measurement of Cl- concentrations and pH values. The results indicate that the combined sensor is robust and sensitive enough to in situ measure Cl- concentrations and pH quantitatively at the steel/concrete interface, which is of indispensable importance to the study of corrosion and protection of the steel in concrete.     

涂敷法制备Ag-AgCl参比电极及其性能

目前制备Ag-AgCl参比电极的方法复杂,电极性能也不稳定。首次用涂敷法制备了Ag-AgCl参比电极：分别以水溶性的丙烯酸乳液和乙烯-聚醋酸乙烯乳液作为粘合剂,将AgCl微粒粘结在Ag电极表面制成Ag-AgCl参比电极。结果表明：2种Ag-AgCl参比电极的稳定性良好,使用寿命较长,均能满足使用要求;其中,以乙烯-聚醋...     

Fabrication of a planar-form screen-printed solid electrolyte modified Ag/AgCl reference electrode for application in a potentiometric biosensor

This study features the fabrication of a planar-form, solid electrolyte modified, (PSEM) Ag/AgCl reference electrode using a screen-printing method. The PSEM Ag/AgCl reference electrode uses agar gel as the inner electrolyte and chloroprene rubber for the liquid junction and insulator. These common low-cost materials and the simple fabrication processes involved render the proposed reference electrode an ideal candidate for cost-efficient mass production. It is shown that the developed reference electrode is insensitive to most of the physiologically important ionic species, including Na+, K+, Li+, Ca2+, NH4+, and Cl-, under continuous measurement conditions. Moreover, as with conventional commercial reference electrodes, the proposed reference electrode exhibits a reversible response, which is maintained until the agar gel dries out. The PSEM Ag/AgCl reference electrode is integrated with an iridium oxide modified Pt-based pH indicator electrode to form a chip-type pH biosensor. The performance of this biosensor is consistent with that obtained from a pH meter based on a macroscopic commercial Ag/AgCl reference electrode. The experimental results confirm that the proposed biosensor is capable of providing precise pH measurements of various real samples. Accordingly, the PSEM Ag/AgCl reference electrode presented in this study provides a viable alternative to the macroscopic Ag/AgCl reference electrode used in many conventional chip-based pH sensors.     

Multiprobe chloride sensor for in situ monitoring of reinforced concrete structures

In situ monitoring of the chloride content is one of the most important procedures in preventing and controlling chloride-induced corrosion in reinforced concrete structures. Thus, the development of chloride sensors is of paramount importance for the continuous monitoring of concrete structures. The sensors must present long lifetime and reliability and operate in a wide range of chloride concentrations.The present work aims at developing and testing a sensor based on Ag/AgCl electrodes for in situ monitoring of chloride ions in reinforced concrete structures. Although these electrodes are widely used in analytical experiments due to their sensitivity to the chloride ion, little is known on their behaviour during exposure to alkaline environments, such as those existing in concrete.The multiprobe sensor presented in this work was tested in mortar and concrete specimens, revealing good stability. The results reveal that the Ag/AgCl sensor presents good sensitivity in a wide range of chloride concentrations.     

New class of Ag/AgCl electrodes based on hydrophobic ionic liquid saturated with AgCl

A new type of Ag/AgCl electrodes based on a hydrophobic ionic liquid has been proposed. The electrode consists of a Ag/AgCl electrode immersed in or coated with a AgCl-saturated ionic liquid, 1-methyl-3-octylimidazolium bis(trifluoromethylsulfonyl)imide ([C(8)mim+][C(1)C(1)N-]), instead of the internal aqueous solution. The [C(8)mim+][C(1)C(1)N-] phase plays dual roles, that is, as a medium dissolving AgCl and an ionic-liquid-type salt bridge upon contact with an aqueous solution. The gelation of the [C(8)mim+][C(1)C(1)N-] phase allows us to prepare coated-wire-type solid-state reference electrodes with a well-defined thermodynamic basis for the electrode potential. Both gelled and nongelled types show stable electrode potentials against the change in the concentration of KCl between 0.05 mmol dm(-3) and 2 mol dm(-3). This new class of reference electrodes opens the way for a variety of miniaturized and solid-state reference electrodes.     

Application of a new Cl-plasma-treated Ag/AgCl reference electrode to micromachined glucose sensor

Micromachined glucose sensors were fabricated and integrated with the plasma-treated Ag/AgCl reference electrodes for the first time. The surface of the Cl-plasma exposed AgCl layers was of granule-shaped morphology and showed the favorable long-term stability with a 13-mV potential drift after 5 h over a commercial liquid-junction Ag/AgCl reference electrode in phosphate buffered saline. The fabricated devices showed a typical behavior of an amperometric glucose sensor and a successful operation as a three-electrode system. Due to the integrability of the reference electrode and the use of low-temperature steps only, the new micromachined process can allow easy mass production of the device and the monolithic integration of signal processing circuitry in the future.     

Metal/polypyrrole quasi-reference electrode for voltammetry in nonaqueous and aqueous solutions

As an alternative to the usual commercial reference and quasi-reference electrodes (QREs), we propose metal (Pt, stainless steel) coated with partially oxidized polypyrrole as a QRE. The electrode is easily fabricated by cyclic voltammetry (CV) with the metal electrode in an acetonitrile or CH2Cl2 solution of 10 mM pyrrole containing 0.1 M Bu4NPF6. These QREs were more stable than the widely used metal (e.g., Ag, Pt) wire QRE as demonstrated by testing in several aqueous and organic media, with the stability checked by CV with ferrocenemethanol as the redox species. The results obtained demonstrate good stability of these QREs over a period of 1 day and relatively reproducible potential in a given solvent and supporting electrolyte. This electrode has the advantage that it does not contaminate the test solution with ions or solvent from a usual liquid electrolyte (e.g., the KCl in an Ag/AgCl). It is also simple to fabricate very small electrodes for use in nanocells, e.g., in scanning tunneling and electrochemical microscopy.     

Automatic electrochemical micro-pH-stat for biomicrosystems

A microelectrochemical pH-stat with an automatic feedback function was fabricated. The operation of the device is based on the nonstandard use of an electrochemical three-electrode system with a pH-sensitive reference electrode, a Ag/AgCl working electrode, and an iridium auxiliary electrode that functions as an actuator to adjust the solution pH. The combination of the electrodes caused a negative feedback in response to a pH change. The shift of the potential of the pH-sensitive reference electrode caused an overpotential on the Ag/AgCl working electrode, which then caused a significant current increase. This led to the electrolysis of water on the auxiliary electrode and the rapid recovery of the pH. The negative feedback function to stabilize the initial state could be confirmed for changes to both the acidic and basic directions. The performance of the pH-stat was characterized in the titration of acetic acid or ammonia. The charge generated in the feedback process changed linearly with respect to the concentration. The pH-stat was also used in the determination of urea by urease and that of the activities of trypsin and pepsin while maintaining the optimum pH for the enzymes. The pH to be fixed could be changed by changing the working electrode potential. Moreover, the two pH-stats could be used to form a pH gradient in a microflow channel by fixing the pH values at two positions.     

Ti/NiCu/Ag and Al/NiCu/Ag thin film deposited on positive temperature coefficient (PTC) thermistor by direct current magnetron sputtering

Metallization of positive temperature coefficient (PTC) thermistors deposited by direct current magnetron sputtering has been investigated. Two kinds of multilayer thin films, namely Ti/NiCu/Ag and Al/NiCu/Ag, are proposed as electrode materials. Conventional NiCr/Ag thin film serves as reference electrode in the experiment. Experimental results show that the newly proposed electrodes exhibit good performance including low ohmic contact, firm adhesion, fine solderability and stability. The surface resistances at room temperature of Ti/NiCu/Ag and Al/NiCu/Ag PTC range from 4.3 to 6.2 Ω, and they change little in moisture condition. The average tensile strength is 6.3 Mpa, which provides firm adhesion between electrode and substrate. At solderability test, the new electrodes can withstand the soakage of lead-free solder at 350 °C for 5 s and the properties remain stable after high temperature treatment.