Sol-Gel Processing of Organic-Inorganic Nanocomposite Protective Coatings

Organic-inorganic nanocomposite protective coatings are prepared on aluminum substrates by the spinning technique with the concept of incorporating homogeneously nanosized particles (of AlOOH, Al2O3, ZrO2, SiC) into molecular organic-inorganic hybrid matrices. The hybrid matrices are prepared from epoxysilane and bisphenol A with imidazol as catalyst. The AlOOH particles are derived from aluminum isoprooxide and introduced into the hybrid sols directly, and Al2O3, ZrO2, SiC particles are first surface-modified with Si–OH from hydrolyzed TEOS. The coatings are dense, smooth and flexible and inhibit corrosion.     

Lithium intercalation into amorphous-silicon thin films: An electrochemical-impedance study

Lithium intercalation into 0.25-μm-thick films of amorphous silicon is studied using the electrochemical-impedance technique. An equivalent circuit, proposed for such electrodes, comprises the electrolyte resistance and three units connected in series, each unit being a parallel combination of a resistance and a constant-phase element. The units relate to the charge transfer processes at the silicon/electrolyte interface, charge transfer though the passive film on the silicon, and the lithium diffusion into the silicon bulk. During potential cycling, changes occur largely in the unit related to the passive film. The lithium diffusion coefficient in the amorphous silicon is estimated as ～ 10^?13 cm² s^?1.     

A New Approach to Characterization of Barrier Properties of ORMOCER Protective Coatings

The Radiometric Emanation Method (REM) was used for the characterization of barrier properties of protective coatings. Radon diffusion parameters of the hardened protective layers prepared from ORMOCER lacquers of varying compositions were examined. The differences in the barrier properties of non weathered and weathered ORMOCER coatings, as well as of INCRALAC coatings, were compared. REM is recommended for the characterization of barrier properties of protective coatings submitted to weathering at varying conditions and time.     

钌镧氧化物涂层在NaCl 溶液中的电化学阻抗谱(EIS)研究

测量了钌镧氧化物涂层的电化学阻抗谱(EIS), 结合循环伏安(CV)及扫描电子显微镜形貌分析, 研究了钌镧氧化物涂层阳极在3.5% NaCl 溶液中电化学表面结构及电化学行为. 在非析氯反应区间, 该涂层EIS 数据的最佳拟合等效电路是R_s(R_ctQ_dl), 在析氯反应区间, 其等效电路为R_s(R_fQ_f)(R_ctWQ_dl). 高频段阻抗行为对应涂层的物理阻抗, 低频段对应涂层与溶液界面的电化学反应阻抗. 实验结果表明, 随着La 浓度增加, 氧化膜及双电层的伪电容增大, 且在La 含量30mol%时达到最大值, 与CV实验结果一致, 证明了加入La 能提高RuO₂涂层的电催化活性. 但在析氯反应区间, 涂层氧化膜的导电性在含La 大于30 mol%之后迅速下降, 在低频段产生Warburg 阻抗, 与其表面钝化和特性吸附现象有关,这是导致含La 70 mol%时电催化活性急剧下降的原因.     

Synthesis and Characterization of Flexible Hydrogel Electrodes for Electrochemical Impedance Measurements of Protective Coatings on Metal Sculptures

A novel conductive anionic hydrogel was synthesized for use as a solid electrolyte for electrochemical impedance spectroscopy (EIS) characterization of the barrier properties of protective coatings on outdoor metalworks, such as bronze sculptures. The AMPS‐co‐PAA hydrogel was soaked in a variety of aqueous salt solutions and characterized by swelling capacity and conductivity in order to determine the most appropriate gel/liquid electrolyte combination for use on culturally significant objects. K₂PIPES‐equilibrated hydrogels were selected as the preferred electrodes for this particular application and were used to measure the impedance of a coated substrate, yielding spectra similar to those from standard liquid cells.     

Potentiometric Method for Evaluation of Protective Properties of Polymeric Coatings

A new method is proposed for evaluation of protective properties of polymeric coatings. The method allows evaluation of the corrosion rate of a coated metal by means of potentiometric indication.     

Formation of Protective Coatings on Graphite by a Microspark Oxidation Method

Models, mechanisms, and criteria of formation of protective coatings on graphite by a microspark oxidation method (MSO) are considered. It is established that a prerequisite for the graphite MSO is the deposition of a barrier film of a valve metal oxide at the graphite surface. Optimum regimes of the graphite MSO in aqueous solutions of sodium aluminate are determined. Protective coatings on graphite comprising α-phase aluminum oxide are obtained. It is concluded that the graphite MSO should be viewed as a version of MSO of metals, which involves the electrochemical deposition (at high voltages that cause the anode to microspark) of oxide films consisting of electrolyte components on graphite, as opposed to a version of MSO of metals, which involves the formation of an anodic film consisting of electrolyte components and the intrinsic oxide.     

Impedance spectroscopy of reactive polymers. 4. An improved experimental procedure for measurement of effective resistivity

Impedance spectroscopy of reactive systems, polymer-forming and non-polymer-forming alike, has been under active investigation in our laboratory for several years. In this article we describe an improved experimental procedure for the determination of fundamental dielectric properties during reaction. A series of experimental steps was established and is recommended in order to generate reproducible and reliable results. © 1996 John Wiley & Sons, Inc.     

复阻抗法分析聚吡咯材料的湿敏特性

通过延长聚合时间到96 h合成了一种对湿度敏感的聚吡咯材料. 采用红外(IR)光谱, X射线衍射(XRD)和扫描电子显微镜(SEM)的方法对合成的材料进行了表征. 测量了基于该材料的湿敏元件的湿度特性, 并且得到了在20 Hz-100 kHz频率范围内的复阻抗谱图. 基于测量结果讨论了该材料制备的湿敏元件的湿度敏感机制. 通过对复阻抗谱的分析研究了该湿敏元件的工作机理并且分析了参与导电的粒子.     

WBE联合EIS技术研究缺陷涂层下金属腐蚀

用电化学阻抗谱(EIS)结合丝束电极(WBE)技术研究了缺陷涂层浸泡在3.5%(质量分数)NaCl溶液中的劣化过程.从浸泡开始到完好涂层鼓泡失效,缺陷涂层丝束电极阻抗响应一直是缺陷区电极腐蚀反应过程特征,而完好涂层的劣化过程和涂层下的腐蚀反应过程特征被"平均掉".根据电极表面的电流分布,结合阻抗谱技术实现了对表面任意局部阴极和阳极区阻抗测试.研究发现,浸泡开始时,缺陷涂层阴极电流和阳极电流均出现在缺陷区,随着腐蚀过程的发展,阳极电流仍然保持在缺陷区,但阴极电流逐渐向完好涂层下扩展.根据实验结果,对缺陷处和涂层下金属腐蚀反应发生发展的机理进行了深入讨论.     

三聚磷酸铝缓蚀性能的EIS研究(英文)

利用电化学阻抗谱研究了方解石及三聚磷酸铝环氧涂层的耐蚀性能 ,并提出了它们的作用机理 .结果表明 ,方解石只起体质颜料作用 ,不具备缓蚀性能 ;而三聚磷酸铝因在钢基表面作用形成致密的保护膜则表现出优良的缓蚀性能 .     

Structure,adsorption and rheological properties of composites based on biocomplexes of natural origin and modified coal

The structure, adsorption and rheological properties have been studied of new composites based on biocomplexes of natural origin and modified coal with various relative compositions. Values of the fractal dimensionality of the composite sorbents have been calculated: they range from 2.26-2.78 as they do also in natural clay minerals. The rheological characteristics of the composites and the influence of their composition on structural-mechanical properties (viscosity) were calculated. Translated from Teoreticheskaya i éksperimental’naya Khimiya, Vol. 45, No. 2, pp. 125-129, March-April, 2009.     

电化学阻抗谱测定环氧涂膜吸水率

The amount of water sorption of an epoxy coating can be determined approximately by measuring the electrochemical impedance spectra of both an Al electrode coated with the epoxy film and a preliminary wetted Al electrode covered tightly with the epoxy film. By comparing the double layer capacity of these two electrodes, the amount of water sorption can be estimated. The resistivity of the electrolytic solution in the film may by thousands times larger than that of the bulk solution. This is due to the fact that the cross-section area of the water passages in the film is of molecular size. The short-distance interaction between the ions and the wall of the water passage retards the transport of the ions seriously. The structure of the water passages is discussed.     

环氧树脂涂覆LY12铝合金在NaCl溶液中的阻抗模型

分别研究了裸LY12铝合金及涂覆环氧树脂涂层后合金在3.5％NaCl溶液中的电化学阻抗谱（EIS）.结果表明,LY12铝合金在点蚀电位以下阻抗谱上出现两个容抗弧,高频段对应Cl－参与的成膜阻抗,低频段对应铝阳极溶解的电化学反应阻抗.合金发生点蚀后出现低频感抗弧.合金/电极在NaCl溶液中先发生涂层吸水,当水及O2抵达基体后建立起电化学反应界面,合金遭受腐蚀；受涂层阻挡的影响,腐蚀产物的扩散逐渐成为控制步骤；当扩散速度较慢的Cl－抵达涂层/金属界面后,与界面处聚集的腐蚀产物间发生化学反应,完成成膜过程,阻抗谱上出现盐膜的阻抗,而扩散阻抗消失.提出了不同浸泡失效阶段涂层电极体系的阻抗模型.     

Evaluation of the Anticorrosive Behaviour of Organic Coatings by Using a Variant of Electrochemical Impedance Spectroscopy

 Electrochemical impedance spectroscopy (EIS) has been acknowledged as a modern and efficient method in the evaluation of the anticorrosive behaviour of coatings. However, difficulties in the interpretation of the complex experimental data present a significant drawback in the use of the method in field studies where quick results are required. The breakpoint frequency method is an extension of the basic EIS method, which allows rapid qualitative assessment of the condition of a coating. By the breakpoint frequency method, the behaviour of epoxy coatings containing various types of reinforcement and applied on steel specimens has been examined after long-term (up to 300 days) exposure to a corrosive environment. The parameter values obtained by the breakpoint frequency method, such as the delaminated area, have been compared with those obtained from fitting the experimental EIS data to a suitable equivalent circuit. These results have also been compared with those of the water permeability of free membranes and the diffusion coefficient determined by standard test methods (e.g. the cup test).     

AC Impedance Studies on the Relationship between the Fractal Characteristics and Electrochemical Properties of Poly(Para‐Phenylene) Film

The effects of experimental conditions on the fractal structure of electrosynthetic polyparaphenylene films were studied by electrochemical impedance spectroscopy. The results indicate that, at the potential range (0‐0.6 V), the film surface fractal dimension rises while the corresponding charge transfer resistances R_ct decrease as charge increases. This is consistent with the oxidized behavior of the conducting polymer. As for the degradation of electrolytes, scanning electron microscopy observations of poly(para‐pheneylene) (PPP) film provide evidence of the close relationship between the degradation of electrolytes and the film morphology, also in good agreement with the electrochemical impedance results interpretation. The X‐ray photoelectron spectroscopic analysis results present that the relative oxygen content ratio (O/C) of the films increases with the times the electrolyte is used, which reveals that the degradation of the electrolyte may result in a compact and passivation PPP film.     

基于丝网印刷电极的阻抗型免疫传感器用于检测烯效唑

采用循环伏安法在丝网印刷碳电极表面电聚合聚苯胺/壳聚糖复合膜,利用静电吸附作用固定烯效唑抗体,制备了检测烯效唑的阻抗型免疫传感器.采用循环伏安法和电化学阻抗谱对电极修饰过程进行了表征,并考察了缓冲溶液pH值、温育温度及时间对免疫反应的影响.在优化的条件下研究了免疫传感器的性能.此免疫传感器具有灵敏度高、特异性强、重现性和稳定性好的特点,对烯效唑的线性检测范围为0.01 ～100 mg/L,相关系数为0.999,检出限为8μg/L(3σ).白菜样品中添加0.05,0.10和1.0 mg/kg烯效唑,平均回收率为98.5％ ～ 104.6％,相对标准偏差为3.3％ ～4.3％,检测结果与气相色谱法的检测结果相符.     

Impedance Response of a Thin Film on an Electrode: Deciphering the Influence of the Double Layer Capacitance

The different contributions of the interfacial capacitance are identified in the case of passive materials or thin protective coatings deposited on the electrode surface. The method is based on a graphical analysis of the EIS results to determine both the passive-film capacitance in the high-frequency domain and the double-layer capacitance in the low-frequency domain. The proposed analysis is shown to be independent of the physicochemical origins of the frequency dispersion of the interfacial capacitances which results, from an analysis point of view of the experimental results, in the use of a constant-phase element However, for a correct evaluation of the thin-film properties such as its thickness, the high-frequency data must be corrected for the double-layer contribution. In particular, it is shown that if the double-layer capacitance gives a frequency-dispersed response, it is necessary to correct the high-frequency part for the double-layer constant-phase elements. This is first demonstrated on synthetic data and then used for the determination of the thickness of thin oxide film formed on Al in neutral pH solution.