桥梁钢结构防腐蚀涂层配套和涂层使用寿命

介绍了桥梁钢结构防腐涂层设计的相关依据:ISO12944-5:2007、BS EN ISO14713:1999和JT/T722-2008。从防腐方法的选择、钢结构设计、涂层配套方案及膜厚确定、涂装管理、涂装设计以及完善的涂层维护计划的建立等方面对影响桥梁钢结构防腐效果的因素进行了探讨。     

Dense-sintered and porous glass-ceramic dielectrics

Translated from Steklo i Keramika, No. 2, pp. 16–18, February, 1992.     

自洁净微晶玻璃的制备工艺研究

为了制备表面具有高疏水性的自洁净微晶玻璃,文中首先以高炉矿渣和钾长石为原料制成微晶玻璃坯体,然后利用溶胶-凝胶的工艺制备出硅溶胶/聚四氟乙烯(PTFE)有机/无机镀液,利用浸渍提拉法在微晶玻璃表面进行镀膜,最后通过热处理制成表面具有自洁净功能的微晶玻璃。分析了乙醇用量、加水量、pH值、陈化时间及温度对于溶胶形成的影响,以及硅溶胶/PTFE配比对于镀液性能和镀膜效果的影响。利用XRD、SEM、接触角测定仪等对样品进行性能检测。结果表明,制备的微晶玻璃的主晶相是镁黄长石,聚四氟乙烯对硅溶胶有良好的修饰作用,自洁净微晶玻璃的接触角已达到120°,具有较强的疏水性。     

Characterization and corrosion protection properties of epoxy powder coatings containing nanoclays

Two types of nanoclays, montmorillonite nanoflakes and halloysite nanotubes, at various concentrations were tested as nanofillers in epoxy powder coatings applied on an aluminum foil and a steel panel. The produced coatings were separated from the aluminum foil, enabling determination of peel strength, and mechanical properties and water permeability were determined for the obtained free films. Coated steel panels were characterized in terms of microstructure and corrosion protection properties in 0.5 M NaCl solution.     

Highly translucent nanostructured glass-ceramic

Transparent and translucent glass-ceramics (GCs) are found in an increasing number of domestic and high-technology applications. In this paper, we evaluated and optimized the effects of two-stage heat treatments on the resulting crystalline phases and microstructure of a glass of the SiO₂–Li₂O–P₂O₅–TiO₂–CaO–ZnO–Al₂O₃ system. The objective was to develop a transparent nanostructured glass-ceramic (GC). After numerous heat treatment trials, we found that a long nucleation period of 72 h at 455 °C followed by a crystal growth treatment at 660 °C for 2 h resulted in a highly translucent GC having homogenously distributed nanocrystals. The relatively high amount of P₂O₅ (2.5 mol%) induced the formation of lithium disilicate as the main crystal phase. We thus developed a GC having crystals under 50 nm, with a high crystallized fraction (52%vol. Li₂Si₂O₅ and 26% vol Li₂SiO₃), transmittance of approximately 80% in the visible spectrum for 1.2 mm thick specimens, nano hardness of 8.7 ± 0.1 GPa (load of 400 mN), a high elastic modulus of 138 ± 3 GPa as measured by nanoindentation, and good flexural strength (350 ± 40 MPa) as measured by ball-on-3 balls tests. Due to its high content of Li⁺, this GC has the potential to be chemically strengthened and can be further developed to be used in a number of applications, such as on displays of electronic devices.     

Chemical stability of photosensitive glass-ceramic

Glass and Ceramics -     

Alkali-free glass-ceramic rigid membranes

A process is proposed for the manufacture of alkali-free glass-ceramic rigid membranes of varying selectivity. The physicomechanical properties of the membranes are described. The membranes can remove microorganisms from polluted water with an efficiency of 95 to 98%. Translated from Steklo i Keramika, No. 6, pp. 10–12, June, 1997.     

Characterization of corrosion processes by current noise wavelet-based fractal and correlation analysis

Electrochemical noise data in the presence of pitting, general corrosion and passivity were analyzed using the discrete wavelet transform. The registered current noise was decomposed into a set of band-limited details, which contain information about corrosion events occurring at a determined time-scale. It has been observed that the signal variance and variances of details depend on the intensity of processes. Distribution of the signal energy among different details was characteristic for the particular type of corrosion. The characterization of corrosion processes on the basis of in the wavelet domain calculated Hurst parameter H and fractal dimension, D, of electrochemical noise signals has been established. It is concluded that general corrosion is a stationary random process with a weak persistence and D = 2.14, whereas pitting corrosion is a non-stationary process with a long memory effect and D = 1.07. Passivity is a non-stationary process near to the Brownian motion with D = 1.56. The persistence features of electrochemical noise signals were explained also by correlation coefficients calculated between signals obtained by discrete wavelet multiresolution decomposition.     

Sintering behaviour of nanostructured glass-ceramic glazes

The thermal behaviour of a glass-ceramic glaze based on the system SiO₂–CaO–ZnO–Al₂O₃ has been evaluated. Frit and kaolin were ball milling using dispersants and binders, and deposited on a green clay based ceramic support. The evolution of the glaze during the sintering step was observed that consisted of a glassy matrix, particles from kaolin and particles from frit. Particles from frit formed a nanostructure of interconnected nanoparticles. Pyroxenes devitrified from the glassy matrix and at higher temperatures they were dissolved in the glassy matrix. Both successes contributed to the final observed nanostructure produced by a spinodal decomposition process in which the crystalline phase had a pyroxene composition.     

Characterization of corrosion resistant clay/epoxy ester composite coatings and thin films

The processibility and corrosion resistance of epoxy ester coatings was improved by the addition of cloisite 15A clay. The weight percent of clay was increased from 1% to 10% of clay. The presence of clay in the coatings was confirmed by using the Fourier transformed infrared spectroscopy, FTIR. The effect of clay on the contact angle of the coatings was determined by using the video contact angle analyzer. The surface contact angle of the coatings decreased with increasing weight percent of clay. The surface roughness as measured by atomic force microscope, AFM decreased with the addition of clay up to 1 wt.% loading. The dynamic mechanical property of the coatings was determined by using the Seiko Dynamic Mechanical Spectrometer, DMS. The reinforcement of epoxy ester with organoclay resulted in a significant increase in the glass transition temperature, Tg. However, there was no significant change in the height of the tangent of the loss angle, tan δ with variation in the clay concentration, indicating that there was no significant change in the damping behavior of the epoxy ester coatings as a result of reinforcement by organoclay.     

Characterization of the glass-ceramic material prepared upon vitrification of an iron-containing surrogate of high-level wastes in a cold crucible

Vitreous materials are prepared by cold crucible induction melting of a surrogate of high-level wastes (from the Savannah River Site, United States) and a borosilicate glass frit taken in mass ratios from 45: 55 to 60: 40. According to the X-ray diffraction and electron microscopic data, the vitreous materials thus produced consist of a glass matrix and a magnetite-type spinel enriched in transition elements. The degree of crystallinity of the materials increases with an increase in the waste oxide content from 6 to 18–20 vol %. The vitreous materials are characterized by a high chemical durability, which decreases only at high contents of the waste oxides (55 wt % and higher) due to the formation of an additional nepheline phase.     

建筑用高炉渣微晶石材的成分、结构和性能研究

对高炉渣微晶石材的组分、性能和微观结构进行研究。采用差热分析、X射线衍射、扫描电镜对材料的热学性能、晶相组成和微观结构进行测试,对成分中的F、S挥发及对析晶的影响进行分析。     

Thermal expansion investigation of iron rich glass-ceramic

A theoretical procedure was developed with the aim of obtaining an estimation of the crystallisation fraction in glass-ceramics by means of thermal expansion measurements. The theoretical model was applied to the crystallisation of an iron rich glass composition yielding magnetite and pyroxene as crystalline phases.The crystallisation mechanism was investigated by means of DTA, XRD, FTIR, TEM; the thermal expansion by Differential Dilatometer. A relationship between the weight fraction of crystal phase and the linear thermal expansion coefficient was obtained. The values of the fraction of crystal phase, evaluated by means of dilatometric measurements, showed a good agreement with the results obtained by means of density variation and XRD analyses.The crystallisation kinetic of the iron rich glass, at 630 and 700 °C, was also investigated by dilatometry and the variation of CTE as a function of the crystallisation time explained in terms of increasing of the apparent viscosity of the residual glass.