Laser glazing of lanthanum magnesium hexaaluminate

Lanthanum magnesium hexaalumminate (LMA) is an important candidate for thermal barrier coatings due to its thermal stability and low thermal conductivity. On the other hand, laser glazing method can potentially make thermal barrier coatings impermeable, resistant to corrosion on the surface and porous at bulk. LMA powder was synthesized at 1600 degrees C by solid-state reaction, pressed into tablet and laser glazed with a 5-kW continuous wave CO2 laser.

Rare Earth Fluorides Nanowires/Nanorods Derived from Hydroxides: Hydrothermal Synthesis and Luminescence Properties

In this paper, we reported the synthesis of nearly monodisperse and well-defined one-dimensional (1D) rare earth fluoride(beta-NaREF4) (RE = Y, Sm, Eu, Gd, Tb, Dy, and Ho) nanowires/nanorods by in situ acid corrosion and anion exchange approach using RE(OH)(3) as precursors via a facile hydrothermal route. X-ray diffraction (XRD), energy-dispersive X-ray (EDX) spectroscopy. scanning electron microscopy (SEM), transmission electron microscopy (TEM). high-resolution transmission electron microscopy (HRTEM), and photoluminescence(PL)spectroscopy were used to characterize the samples. The results show that the as-prepared rare earth fluoride (beta-NaREF4) nanowires/nanorods preserve the basic morphology of the initial RE(OH)(3) precursors.

Rotating minidisk-disk electrodes

Rotating minidisk-disk electrode (RMDDE) was developed by replacing ring electrode of rotating ring-disk electrode (RRDE) with a minidisk electrode. Its applications were demonstrated by studying electrochemical reactions of ferricyanide and divalent copper. The replacement of ring electrode by minidisk electrode results in following advantages. First, the fabrication of RMDDE is easier than that of RRDE with the same electrode material. Second, there is more freedom in choosing electrode materials and sizes, since it is difficult to make thin ring electrodes of RRDE with fragile materials. Third, the replacement of ring electrode by minidisk electrode saves electrode materials, especially rare materials. Finally, the substitution of minidisk electrode for ring electrode allows using multiple minidisks for simultaneous monitoring of multiple components. Therefore, RMDDE is a promising generator-collector system, especially when special generator-collector systems are not commercially available, such as corrosion study and electrocatalysis study of new electrode materials.

Structure and mechanical properties of Mg-Zn-RE system alloys

The lightest density of Mg has stimulated renewed interest in Mg based alloys for applications in the automotive, aerospace and communications industries. However, Mg in the pure form has relatively low strength, limited ductility and is susceptible to corrosion. Great efforts have been made to improve the mechanical properties of Mg alloys. Alloying Mg with other elements is one of the most important methods. An important class of Mg alloys is the Mg-Zn-RE system (RE = rare earth elements). In recent few decades, a series of new Mg-Zn-RE system alloys have been obtained, and detailed the structure and mechanical properties of the alloys. In this paper, the structure and mechanical properties of the Mg-Zn-RE alloys have been summarized. It showed that these alloys have high strength and they are prospected to be widely used in the future.

Electrostatic interaction hybrids from water-borne conductive polyaniline and inorganic precursor containing carboxyl group

Electrostatic interaction conductive hybrids were prepared in water/ethanol solution by the sol-gel process from inorganic sol containing carboxyl group and water-borne conductive polyaniline (cPANI). The electrostatic interaction hybrids film displayed 1-2 orders of magnitude higher electrical conductivity in comparison with common hybrids film, showing remarkable conductivity stability against water soaking. Most strikingly, it displayed ideal electrochemical activity even in a solution with pH = 14, which enlarged the conducting polyaniline application window to strong alkaline media.

Water-resistant conducting hybrids from electrostatic interactions

Conductive hybrids were prepared in a water/ethanol solution via the Solgel process from an inorganic sol containing carboxyl groups and water-borne conductive polyaniline (cPANI). The inorganic sol was prepared by the hydrolysis and condensation of methyltriethoxysilane with the condensed product of maleic anhydride and aminopropyltriethoxysilane as a catalyst, for which the carboxyl counterion along the cPANI backbone acted as an electrostatic-interaction moiety. The existence of this electrostatic interaction could improve the compatibility of the two components and contribute to the homogeneous dispersion of cPANI in the silica phase. The electrostaticinteraction hybrids displayed a conductivity percolation threshold as low as 1.1 wt % polyaniline in an emeraldine base, showing 2 orders of magnitude higher electrical conductivity than that without electrostatic interactions. The electrostatic-interaction hybrids also showed good water resistance; the electrical conductivity with a cPANI loading of 16 wt % underwent a slight change after 14 days of soaking in water.

Long-term anticorrosion behaviour of polyaniline on mild steel

Anticorrosion performances of polyaniline emeraldine base/epoxy resin (EB/ER) coating on mild steel in 3.5% NaCl solutions of various pH values were investigated by electrochemical impedance spectroscopy (EIS) for 150 days. In neutral solution (pH 6.1), EB/ER coating offered very efficient corrosion protection with respect to pure ER coating, especially when EB content was 5-10%. The impedance at 0.1 Hz of the coating increased in the first 1-40 immersion days and then remained constant above 10(9) Omega cm(2) until 150 days, which in combination with the observation of a Fe2O3/Fe3O4 passive film formed on steel confirmed that the protection of EB was mainly anodic. In acidic or basic solution (pH 1 or 13), EB/ER coating also performed much better than pure ER coating. However, these media weakened the corrosion resistance due to breakdown of the passive film or deterioration of the ER binder.

Synthesis and characterization of electroactive and biodegradable ABA block copolymer of polylactide and aniline pentamer

A triblock copolymer PLA-b-AP-b-PLA (PAP) of polylactide (PLA) and aniline pentamer (AP) with the unique properties of being both electroactive and biodegradable is synthesized by coupling an electroactive carboxyl-capped AP with two biodegradable bihydroxyl-capped PLAs via a condensation reaction. Three different molecule weight PAP copolymers are prepared. The PAP copolymers exhibit excellent electroactivity similar to the AP and polyaniline, which may stimulate cell proliferation and differentiation. The electrical conductivity of the PAP2 copolymer film (similar to 5 x 10(-6) S/cm) is in the semiconducting region. Transmission electron microscopic results suggest that there is microphase separation of the two block segments in the copolymer, which might contribute to the observed conductivity. The biodegradation and biocompatibility experiments in vitro prove the copolymer is biodegradable and biocompatible. Moreover, these new block copolymer shows good solubility in common organic solvents, leading to the system with excellent processibility. These biodegradable PAP copolymers with electroactive function thus possess the properties that would be potentially used as scaffold materials for neuronal or cardiovascular tissue engineering.

Ceramic materials for thermal barrier coatings

This paper summarizes the basic properties of ceramic materials for thermal barrier coatings. Ceramics, in contrast to metals, are often more resistant to oxidation, corrosion and wear, as well as being better thermal insulators. Except yttria stabilized zirconia, other materials such as lanthanum zirconate and rare earth oxides are also promising materials for thermal barrier coatings.

Conductive hybrids from water-borne conductive polyaniline and (3-glycidoxypropyl)trimethoxysilane

Free-standing conductive films of organic-inorganic hybrids were prepared employing the sol-gel process of (3-glycidoxypropyl)trimethoxysilane (GPTMS) and water-borne conductive polyaniline (cPANI) in water/ethanol solution. The hybrids displayed a percolation threshold for electrical conductivity at a volume fraction of 2.1% polyaniline (PANI); the maximum conductivity of the hybrids reached 0.6 S/cm. GPTMS showed good compatibility with water-borne cPANI during the sol-gel process, and freestanding conductive films were obtained at room temperature. Transmission electron microscopy images of the hybrids indicated that the cPANI was dispersed in the inorganic phase in nanoscale. Because of good confinement of cPANI chains in the inorganic network, water resistance of the hybrid films was significantly improved compared with that of pure cPANI; the electrical conductivity of the films kept stable for 6-7 days soaking in water, whereas it decreased sharply for 1 day soaking for the pure cPANI.

MECHANISM OF IRON INHIBITION BY STEARIC-ACID LANGMUIR-BLODGETT MONOLAYERS

Using the Langmuir-Blodgett (LB) technique, stearic acid (SA) monolayers were deposited onto the surface of an iron (Fe) electrode to study the inhibition effect and the mechanism of SA in a neutral medium. Molecular orientation and the number of deposited monolayers of SA were shown to have marked effects on inhibition of Fe corrosion. The inhibition mechanism depended mainly on blocking.

Electrochemical investigations of micro-droplets formed on metals during the deliquescence of salt particles in atmosphere

CORROSION; WATER; SPECTROSCOPY; CHLORIDE; ZINC; NUCLEATION; INTERFACE; ELECTRODE; SURFACES; GROWTH

Phenomenon of micro-droplets formation on metals during the deliquescence of salt particles in atmosphere

CORROSION; MECHANISM; WATER; ZINC

新型杂环化合物碳钢酸洗缓蚀剂的合成、评价及机理研究

缓蚀剂在金属防护工程中占有重要的地位，在国民经济建设中发挥着越来越重要的作用。从目前热力设备防腐及其他工业领域防腐情况来看，酸洗时使用缓蚀剂是一种行之有效、经济效益显著的防腐手段。虽然目前缓蚀剂从分子设计、合成路线与工艺，复配增效，应用性能等方面都取得了较大的发展，但是其理论进展仍远滞后于实践，对于不少缓蚀剂的缓蚀机理尚存争议，因此运用各种手段方法研究缓蚀剂的作用机理，发展和完善缓蚀剂理论，成为目前缓蚀剂研究领域的热门课题。本论文筛选或合成了三种类型十二种新型杂环化合物作为缓蚀剂，通过失重实验，电化学实验，量子化学计算及扫描电镜实验多种手段和方法测试了所选化合物在1mol/LHCl溶液中对碳钢的缓蚀性能，分析了它们对碳钢的缓蚀机理，从理论上探讨了缓蚀剂分子与金属表面的作用方式，总结归纳了分子结构与缓蚀效果之间的关系。 本论文中涉及的三类新型杂环化合物为：嘌呤类化合物，席夫碱-三唑类化合物和硫脲-三唑类化合物，针对不同类化合物的不同特点采用了不同的处理方法，研究的主要成果如下： 失重、电化学及扫描电镜实验结果表明，嘌呤类化合物对碳钢有较好的缓蚀效果和较高的缓蚀效率。针对嘌呤分子是平面型小分子的特点，结合实验现象及量子化学计算结果，推断了其吸附特点。在国内外缓蚀剂研究领域首次建立并使用了108个铁原子的碳钢表面模型，在此基础上，根据嘌呤类分子的吸附特点作了吸附曲线，证明嘌呤类分子的吸附机理为平面接近碳钢的物理吸附，嘌呤分子与碳钢表面的相互作用源于π-π超共轭作用。吸附曲线模型的创立和使用使得对缓蚀剂机理的研究不再仅仅局限于对缓蚀剂分子本身结构特点的分析与推测，而是可以在整个腐蚀体系的基础上对缓蚀剂分子在金属表面的作用机理进行研究，更重要的是，提供了一种在一定范围内从理论上筛选缓蚀剂的初步模型。 实验结果表明席夫碱-三唑类化合物对碳钢有很好的缓蚀效果以及很高的缓蚀效率，其中CMTT化合物，在10-3mol/L时对碳钢的缓蚀效率可达97%。针对席夫碱-三唑类化合物分子活性中心多，分子柔性刚性相结合的特点，量子化学计算中采用了富奎指数判断分子中起作用的活性吸附中心，推断了席夫碱-三唑类化合物的吸附为化学吸附。其机理为：通过巯基硫原子提供电子与碳钢表面铁原子成键，而碳钢表面多余的负电荷反馈至席夫碱的碳氮双键形成反馈键。新型席夫碱-三唑类化合物作为缓蚀剂的研究不但提供了新型高效无毒的酸洗缓蚀剂，而且碳氮双键与杂环的结合在提高了化合物缓蚀效率的前提下，还针对杂环化合物水溶性差的缺点提供了一种提高水溶性的解决方法，为更多新型化合物用于缓蚀剂领域提供了可行之道。 硫脲-三唑类化合物同样对碳钢有很好的缓蚀效果以及很高的缓蚀效率，尤其是TBU化合物，在10-3mol/L时对碳钢的缓蚀效率高达98%。针对硫脲-三唑类化合物分子缓蚀过程中硫原子的突出贡献，量子化学计算中将硫原子连接在碳钢表面上，然后对整个体系进行了结构优化，从理论上证明了该类化合物的吸附机理为：通过巯基硫原子提供电子与碳钢表面铁原子形成配位键，而硫脲-三唑类化合物分子中以苯环为主的共轭体系则以π-π超共轭作用覆盖在碳钢表面，是以化学作用为主物理-化学作用共存的吸附方式。而且在研究该类化合物的吸附机理中，发现了分子中小基团的立体位阻因素对化合物的缓蚀性能造成很大影响，目前关于此类的报道非常罕见。 值得一提的是，在各类缓蚀剂交流阻抗谱的测试与处理过程中，发现缓蚀剂分子的吸附过程对阻抗谱图有很大影响，本论文中采用了两种等效电路图相结合的方法对阻抗谱图进行了处理，体现了吸附过程的影响，得到更好的拟和结果。 新型杂环化合物作为缓蚀剂的研究，不但提供了多种具有潜在应用前景的高效低毒的新型酸洗缓蚀剂，对目前缓蚀剂领域存在的部分问题提出了解决方案，更重要的是，将新的模型和方法运用于对缓蚀剂机理的研究分析中，为缓蚀剂的筛选提供了一种新的理论模型，为新型缓蚀剂分子的设计合成提供了一定的科学依据，对缓蚀剂理论的发展与完善起到了一定的促进作用。

聚三氟氯乙烯氟碳涂料在紫铜表面的耐蚀阻垢性能

面临世界上严重的淡水资源紧缺，海水淡化和海水利用技术是可行的解决方案之一。铜及其合金因其良好的机械性能、可成型性、导热性以及在海洋环境中优良的耐腐蚀性能成为海水冷凝器的首选材料，但由于海水成分的多样性和复杂性，对铜及其合金还是造成了一定的腐蚀和结垢问题，因而制约着海水利用技术的发展和应用。 氟碳涂料是一种新型的高科技功能性涂料，其聚合物分子间的作用力低，决定着它具有非常低的表面自由能。因此，氟碳涂料具有不可润湿性、防沾污性和自润滑性。而它本身所特有的螺旋结构则决定了它具有一般涂料所难以比拟的优异的物理性能，在防腐蚀领域特别是复杂苛刻的海洋环境中有着广阔的应用前景。 本文选择了性能优异的聚三氟氯乙烯这种氟碳涂料，涂覆在紫铜上，研究了其阻垢能力和耐海水腐蚀性能。实验首先是通过配制超硬度的实验用水，测试了不同温度下，试样上所结水垢的量，然后通过SEM-EDX做了样品表面成分分析，结果表明涂料在样品表面附着均匀、致密，与基底金属结合紧密，可以有效地防止水垢的生成，并且还防止了金属铜的腐蚀问题。为进一步研究涂层的耐蚀性能，做了中性盐雾试验和电化学实验。在经过3000h的盐雾试验后，样品表面几乎没有变化，腐蚀增重率很小，金属腐蚀可以忽略不计；在为期90d的交流阻抗实验过程中，刚开始时阻抗弧不稳定，到第十天达到最大，然后慢慢减小，但始终为单弧容抗，只有一个时间常数。而且，在90d以后，极化电阻值仍然在10000Ω以上，因此，在实验期间，腐蚀介质不能到达涂层/基底金属界面，基底金属受到了良好的保护。