环氧/聚氨酯涂层在4种环境中失效行为的EIS

用电化学交流阻抗法(EIS)研究了环氧富锌底漆/环氧云铁中间漆/丙烯酸聚氨酯面漆这一涂层体系在3.5%NaCl溶液、3.5%NaCl溶液+紫外辐射、湿热和盐雾这4种环境中的失效行为,探讨了特征频率下的相位角和涂层电阻值之间对应的关系。结果表明:中频区10Hz处涂层相位角随时间的变化曲线和涂层电阻值随时间的变化曲线有良好的相似性,据此可以对所研究的涂层体系失效程度进行快速评价;所试验的4种腐蚀环境对所研究的涂层体系的破坏作用由小到大依次为:3.5%NaCl溶液盐雾湿热3.5%NaCl溶液+紫外辐射。     

电化学方法研究环氧防锈涂料实验室实验与实海环境实验的相关性

用电化学交流阻抗法(EIS)研究了环氧防锈涂料在实海浸泡实验和3.5%NaCl溶液浸泡实验、盐雾实验、湿热实验3种实验室加速实验中的失效行为,探讨了实海浸泡实验和3种实验室加速实验的|Z|_(0.01 Hz)对应关系。结果表明:4种腐蚀环境对所研究的涂层体系的破坏作用由小到大依次为:3.5%NaCl溶液实海浸泡湿热盐雾;相对实海浸泡实验,盐雾实验对环氧涂层腐蚀失效的加速因子约为2.3。     

利用EIS高频区参数评价两种环氧涂层的性能

利用10 kHz下的相位角、10 kHz下的相对介电常数和对应于45°相位角的特征频率这3种EIS高频区的参数对两种环氧涂层体系在盐水浸泡+紫外照射的腐蚀条件下的失效过程进行了表征,并与涂层阻抗值进行了对比。测量结果表明,上述3种高频区参数的结果一致,都能够反映涂层性能的变化及相对优劣。当频率10 kHz处的相位角下降到40°,相对介电常数增大到40,或特征频率接近10 kHz时,所研究的两种环氧涂层体系的阻抗值都对应降低到10⁶ Ω•cm²左右,涂层保护性能接近失效。由于这几种EIS高频区参数能够很快测得,因此可以利用这些参数快速评价该涂层的保护性能与失效程度。     

改性石墨烯/聚苯胺/环氧树脂复合材料的制备及防腐性能的研究

采用原位聚合法制备改性石墨烯/聚苯胺(PGO/PANI)复合材料,再通过共混的方式将PGO/PANI和环氧树脂复合制备PGO/PANI/EP复合涂层。利用电化学阻抗测试探究了PGO/PANI/EP的防腐能力,并模拟在3.5%NaCl溶液加速浸泡后复合涂层的防腐能力的变化。结果表明,当PGO含量为7%时,复合材料的防腐性能最佳,在3.5%NaCl溶液中浸泡24 h后复合涂层的涂层电阻为5.99×10~5Ω·cm~2,仍具有较好的阻隔性能。     

EIS法研究3种配套涂层体系的腐蚀电化学行为

采用电化学阻抗谱(EIS)研究了由水性无机富锌底漆、环氧中间漆和氯化橡胶面漆3种涂料配套而成的3种不同涂层体系在3.5%NaCl溶液中的电化学腐蚀行为,考察了氯化橡胶面漆、水性无机富锌底漆／氯化橡胶面漆、水性无机富锌底漆／环氧中间漆／氯化橡胶面漆这3种涂层体系的阻抗谱在浸泡过程中的演化并据此比较了3种涂层体系的防护性能。结果表明,两涂层体系的防护性能比单涂层的还要差,三复合涂层体系的防护性能最好。根据涂层腐蚀电化学阻抗谱特征推测,中间漆在三复合涂层体系中起到了使底漆和面漆结合更加紧密的桥梁作用。     

动力系统利用液化天然气冷能的节能减排分析

针对动力系统CO₂减排能耗过高的问题,将液化天然气（LNG）的冷能集成用于空气分离制氧和CO₂近零排放动力循环的CO₂捕集,提出了一种利用LNG冷能的CO₂近零排放动力系统设计方案。研究结果表明：空分装置利用LNG冷能生产高压氧气、液氮和液氩等产品,生产能耗比传统空分装置降低57.6％,CO₂近零排放动力循环的火用效率可从52%提高至55.9％。同时,建立了CO₂近零排放动力系统利用LNG冷能的节能减排效益的数学模型,并对动力系统参数进行了分析。以一个进口量为3.0×10⁶ t·a^-1的接收站为例,CO₂近零排放动力系统利用接收站的LNG冷能每年可节省用电2.78×10⁸ kW·h,减少排放CO₂约3.87×10⁵ t·a^-1,经济效益可达到2.19亿元·a^-1。     

Ni载体整体煤气化链式燃烧联合循环性能

本文将具有分离CO₂的链式燃烧技术与整体煤气化联合循环(IGCC)技术结合，构成整体煤气化链式燃烧联合循环系统，对系统性能进行了模拟研究。结果表明，采用德士古气化工艺、空气反应器出口温度1200℃，NiO/NiAl₂O₄作载氧体，压气机压比17、补燃后透平初温(TIT)1350℃、冷却空气量12％时，系统净效率39.61% HHV（41.55%LHV），CO₂排放量126 g·kW^-1·h^-1。补燃温度1350℃，空气反应器温度由1000℃升高到1200℃，CO₂的回收率提高约23％，系统效率由40.3%降低到39.61％；补燃温度由1200℃提高到1500℃，系统净效率由37.4%增加到40.8%，CO₂的排放量从3g·kW^-1·h^-1增加到202 g·kW^-1·h^-1；补燃温度一定，压比增大，系统比功减小，CO₂排放量增加，效率先增大后减小，存在最佳压比.     

UV/Fe3+/H2O2体系降解活性艳橙X-GN废水的动力学研究

在自制的光催化反应器中，采用UV/Fe³⁺/H₂O₂体系光解活性艳橙X-GN模拟废水，考察了X- GN、Fe³⁺和H₂O₂初始浓度、初始pH值及温度对光解过程的影响。结果表明，在8 W低压汞灯(λ＝254 nm)照射下，UV/Fe³⁺/H₂O₂能够有效地降解结构稳定的X-GN，在pH=3.0、温度50 ℃、时间120 min、Fe³⁺和H₂O₂初始浓度分别为2.5×10^－5 mol·L^－1和1.5×10^－4 mol·L^－1时，含200 mg·L^－1X GN模拟废水的色度去除率和TOC去除率分别达到100%和90.15%。在此基础上得到了该催化氧化反应的一级动力学模型，求得X-GN氧化和TOC降解动力学模型的表观活化能分别为867 kJ·mol^－1和25.38 kJ·mol^－1。同时依据离子色谱 (IC)、GC/MS对X-GN降解中间产物和最终产物的进行了鉴定，证实有导致X-GN氧化和TOC降解不同步的中间产物存在。     

等离子喷涂TiO2涂层的海水环境失效机制

运用电化学阻抗测试技术对不同腐蚀时间的涂层进行测试,参照等离子喷涂制备的TiO₂涂层的形貌结构特点,分析TiO₂涂层在海水介质中的腐蚀失效过程.研究表明：涂层的极化电阻在浸泡初期降低较快,后因腐蚀产物和污损物阻塞腐蚀通道,极化电阻又有所上升,趋于稳定.建立合适的等效电路分析涂层腐蚀的阻抗谱,考察各元件参数的变化,进一步分析涂层腐蚀的规律.     

以含氟预聚物为助稳定剂的苯乙烯细乳液聚合

以苯乙烯(St)和甲基丙烯酸十二氟庚酯(G04)的无规共聚物(PSF)作为助稳定剂,进行St的细乳液聚合,考察了不同含氟量的PSF对转化率、聚合速率R_p、液滴粒径和成核粒子数的影响。结果表明,当含氟量由0增加到34.9%,转化率由67.5%增加到80.1%,R_p由0.75×10^-2 mol · L^-1·min^-1提高到1.74×10^-2 mol ·L^-1·min^-1;PSF的含氟量对细乳化后液滴粒径的影响较小,但对聚合过程中成核粒子数有较大影响。当含氟量由0增加到34.9%时,反应3 h后,体系成核粒子数由每升1.83×10^16个增加到2.07×10¹⁶个,并初步分析了PSF可以单独作为助稳定剂的作用机理。     

Enhanced corrosion resistance of layered double hydroxides/steam coating composite coating prepared by the hydrothermal method on LA43M magnesium–lithium alloy substrates

An excellent anticorrosion Mg–Al layered double hydroxide (LDH) composite coating was successfully fabricated on LA43M magnesium alloy substrates via an in situ steam coating (SC) process and a subsequent hydrothermal treatment at different temperatures. The microstructure, composition and phase formation of the composite coatings were studied via X-ray diffractometer, energy disperse spectroscopy, and scanning electron microscope, respectively. The corrosion resistance of composite coatings was further investigated using electrochemical measurements and corrosion test. The results showed that LDH/SC composite coating has typical nanosheets microstructure, which effectively seal the defects of SC. As the hydrothermal temperature increases, the thickness and density of nanosheets increases, and the corrosion resistance was significantly improved. Especially, the Mg–Al LDH/SC composite coating prepared at 100°C was the most dense and thickness, and exhibited the optimal and long-term anticorrosion resistance in 3.5 wt.% NaCl soultion. It has the lowest I_corr (1.767 × 10⁻⁸ A/cm²), which decreased by three and two orders of magnitude compared with the bare substrate and SC. Furthermore, it can maintain good chemical stability after immersion in the corrosion medium for 192 h and its hydrogen evolution rate (0.00416 mL·cm⁻²·h⁻¹) and weight lost rate (0.00266 mg·cm⁻²·h⁻¹) were the lowest compared with other samples.     

AIBA·2HCl-NaHSO3引发下DMDAAC-AM共聚物的合成与表征

采用偶氮二异丁脒二盐酸盐(AIBA·2HCl)和NaHSO₃(RH)组成的引发体系，研究了引发剂浓度、溶液的pH值、引发剂复配和加料方式等因素对二甲基二烯丙基氯化铵(DMDAAC)-丙烯酰胺(AM)共聚合反应规律的影响.结果表明：在30 ℃、n_AM∶n_DMDAAC=4∶1、ω(monomer) =30％和引发剂AIBA·2HCl-RH的浓度为1.0×10^-4 mol·L^-1的条件下， pH=7.0时， DMDAAC-AM共聚物的特性黏数达11.56 dl·g^-1;pH=10.0时，特性黏数最高达13.60 dl·g^-1.采取连续加料方式，可获得阳离子度38.8％，特性黏数达11.61 dl·g^-1的共聚物.进一步测得该引发体系30 ℃下，聚合反应的表观活化能为33.25 kJ·mol^-1，单体的竞聚率为γ_AM=6.800，γ_DMDAAC=0.174.     

Tribological and corrosion behaviors of fluorocarbon coating reinforced with sodium iron titanate platelets and whiskers

A series of sodium iron titanate (NFTO)–fluorocarbon composite coatings have been prepared with the liquid-phase blending method. The effects of two types of NFTO, NFTO platelets, and NFTO whiskers, on the tribological and corrosion behaviors of the composite coatings, are systematically studied. The results show that the addition of NFTO can significantly enhance the friction-reducing and wear resistance performances of the fluorocarbon coating. Under dry sliding, the minimum specific wear rate is 1.67 × 10⁻⁴ mm³/Nm for the platelet-filled composite coatings and 1.15 × 10⁻⁴ mm³/Nm for the whisker-filled composite coatings, respectively, showing a decrease of 83.5 and 88.6% than that of pure coating. Under a simulated seawater environment, the minimum specific wear rate is 5.44 × 10⁻⁵ mm³/Nm for the platelet-filled composite coatings and 0.84 × 10⁻⁵ mm³/Nm for the whisker-filled composite coatings, respectively, showing a decrease of 90.5 and 98.5% than that of pure coating. The morphologies of worn surfaces, wear debris, and transfer films are analyzed, and the corresponding wear resistance mechanisms are discussed. The electrochemical impedance spectroscopy certifies a remarkably improved corrosion resistance of the composite coatings which have been immersed in 3.5 wt % NaCl solution for 30 days. The composite coating reinforced with 7.5 wt % platelets shows the highest resistance of 256.3 × 10⁶ Ω·cm², approximately two orders of magnitude higher than that of pure coating. © 2020 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2020 , 137, 48936.     

缺氧胁迫影响硝化污泥活性的机理

硝化过程是废水生物脱氮的关键环节。为了研究缺氧胁迫对硝化活性的影响及其机理，采用分批培养法分别测定了经0、12、24 h缺氧滞留处理的污泥硝化活性、过氧化氢酶活性和过氧化物酶活性，以及这些硝化污泥抗氧毒（过氧化氢）性能。经过12、24 h缺氧处理后，污泥平均比氨氧化活性分别从0.894 mg N·(g MLSS)^-1·h^-1降为0.453、0.387 mg N·(g MLSS)^-1·h^-1，下降了46.8％、49.8％，平均比亚硝酸氧化活性也从0.761 mg N·(g MLSS)^-1·h^-1降至0.485、0.459 mg N·(g MLSS)^-1·h^-1，下降了36.3％、39.7％。试验结果证明，缺氧胁迫可降低污泥硝化活性，缺氧胁迫时间越长，硝化活性降幅越大，缺氧胁迫对氨氧化的影响大于亚硝酸氧化。缺氧胁迫可抑制硝化污泥的抗氧化酶活性，POD、CAT活性分别下降了10％、17％（12 h）和24％、21％（24 h），缺氧胁迫时间越长，抗氧化酶活性越低。缺氧胁迫可削弱硝化细菌的抗氧毒能力，引起硝化活性降低。     

Electrochemical corrosion behavior of composite coatings of sealed MAO film on magnesium alloy AZ91D

Protective composite coatings were prepared on magnesium alloy AZ91D by micro-arc oxidation (MAO) treatment plus a top coating with sealing agent using multi-immersion technique under low-pressure conditions. The corrosion resistance of AZ91D alloy with composite coatings was superior evidently to that with merely MAO film. SEM observations revealed that the sealing agent was integrated with MAO film by physically interlocking; therewith covered uniformly the surface as well as penetrated into pores and micro-cracks of MAO film. The anti-corrosion properties in 3.5% NaCl solution of the composite coatings were evaluated by using electrochemical impedance spectroscopy (EIS) and potentiodynamic polarization measurements. Based on the results of chronopotentiometric (E ∼ t) and EIS measurements for long time immersion in 3.5% NaCl solution, appropriate equivalent circuits for the composite coatings system were proposed. It follows that due to the blocking effect of the sealing agent in pores and cracks in MAO film, the composite coatings can suppress the corrosion process by holding back the transfer or diffusion of electrolyte and corrosion products between the composite coatings and solution during immersion.     

Study on electrochemical behavior of Nano‐ZnO modified alkyd‐based waterborne coatings

A nano‐composite coating was formed using nano‐ZnO as pigment in different concentrations, to a specially developed alkyd‐based waterborne coating. The nano‐ZnO modified composite coatings were applied on mild steel substrate by dipping. The dispersion of nano‐ZnO particles in coating system was investigated by scanning electron microscopic and atomic force microscopic techniques. The effect of the addition of these nano‐pigments on the electrochemical behavior of the coating was investigated in 3.5% NaCl solution, using electrochemical impedance spectroscopy. Coating modified with higher concentration of nano‐ZnO particles showed comparatively better performance as was evident from the pore resistance (R_po) and coating capacitance (C_c) values after 30 days of exposure. In general, the study showed an improvement in the corrosion resistance of the nano‐particle modified coatings as compared with the neat coating, confirming the positive effect of nano‐particle addition in coatings. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

纳米MnO2离子筛的锂吸附性能

通过控制水热合成反应条件制备了不同晶相的一维纳米MnO₂，进一步用浸渍法制备了Li-Mn-O三元氧化物前驱体，并经酸处理后得到对锂离子具有特殊选择性的离子筛。用XRD、TEM、吸附等温线及反应动力学等手段对产物的晶相结构和锂吸附性能进行了研究。实验结果表明，反应物浓度对MnO₂不同晶面的生长速率有不同的影响；从TEM图像中可以清楚地看到，水热合成法制备出了尺寸为φ5nm×400nm的一维MnO₂纳米线；在pH＝9.19时每克离子筛的单分子层锂离子饱和吸附量Q_m为2.43mmol·g^-1；吸附速率常数为2.17×10^-6 s^-1；吸附量随溶液pH值的增加而增加，当pH=12.5时，相应的吸附量为3.47mmol·g^-1。     

中性体系中MoO42-对碳钢垢下局部腐蚀的抑制作用

设计了一种能够模拟垢下局部腐蚀自催化过程的闭塞电池,采用极化曲线和电化学阻抗方法研究了MoO₄^2-对N80钢在近中性NaCl溶液中闭塞区内化学及电化学状态变化的影响。结果表明,MoO₄^2-能有效地减缓闭塞区内pH值降低及Cl^-浓集、减弱酸化自催化效应、抑制垢下局部腐蚀。MoO₄^2-的作用机制在于使水合氧化铁腐蚀膜由阴离子选择性变为阳离子选择性,H⁺可以从膜下扩散出去,而Cl^-难以扩散到膜下富集,抑制了腐蚀反应的阴极过程;同时MoO₄^2-迁入闭塞区后增大了电极表面膜层阻抗,抑制了腐蚀反应的阳极过程。     

Designing of corrosion resistant epoxy coatings embedded with polypyrrole/SiO2 composite

Polypyrrole/SiO₂ composite was synthesized by chemical oxidative polymerization of pyrrole using FeCl₃. The synthesized polymer composite was loaded in epoxy resin to develop coatings for mild steel substrates using powder coating technique. SEM and TEM images reveal homogenous dispersion of SiO₂ particles in polypyrrole matrix. TGA analysis confirms good thermal stability of the polymer composite. Tafel polarization and electrochemical impedance spectroscopy (EIS) results exhibit remarkably high corrosion protection efficiency of epoxy coatings with polymer composite in 3.5% NaCl solution. Corrosion studies of coatings with an artificial defect reveal the passivation of defect by the polymer composite present in the epoxy coatings. Salt spray test results revealed superior corrosion resistance offered by the polymer composite.     

丙酮酸分批发酵的供氧控制模式

以一株光滑球拟酵母的多重维生素营养缺陷型为研究菌株,考察了分批发酵中不同体积传氧系数(KL_a)对其产丙酮酸性能的影响.高KL_a(450 h^-1)下,丙酮酸产率较高(0.797 g·g^-1),但葡萄糖消耗速度较慢(1.14 g·L^-1·h^-1);低KL_a(200 h^-1)下,葡萄糖消耗速度快(1.97 g·L^-1·h^-1),然而丙酮酸产率(0.483 g·g^-1)却明显下降.根据发酵过程主要参数和碳流分配的变化特性提出了发酵前16h控制KL_a为450h^-1、16h后控制KL_a为200 h^-1的分阶段供氧控制模式,结果实现了高产量(69.4 g·L^-1)、高产率(0.636 g·g^-1)和高葡萄糖消耗速度(1.95g·L^-1·h^-1)的相对统一,丙酮酸生产强度(1.24g·L^-1·h^-1)比控制KL_a恒定为450、300和200h^-1的过程分别提高了36％、23％和31％.实验数据表明,供氧良好状态下细胞产丙酮酸性能出现的差异可能是由维生素处于亚适量水平时酵解产生的NADH去路不同,导致细胞处于不同的能量水平而引起的.