氧化还原引发乳液聚合单体水溶性与动力学之间的关系

本文研究了以过硫酸钾／焦亚硫酸钠为氧化还原引发体系，在苯乙烯、醋酸乙烯酯为具体单体的乳液聚合中，单体水溶性与动力学之间的关系。通过实验考察了聚合温度、搅拌速率、电解质浓度对聚合反应转化率～时间关系的影响，并讨论了单体水溶性、自由基水相反应和聚合速率等之间的内在联系。同时得出该氧化还原引发下苯乙烯和醋酸乙烯酯体系的表观活化能分别为４７．０６ｋｊ／ｍｏｌ和约７０ｋＪ／ｍｏｌ。     

长江特枯水情下青草沙水库供水潜能分析研究

根据长江流域新水情和长江北支新地形等有利条件,依据长江口咸潮严重入侵期氯化物过程线进行水量平衡精细化调算,提出以满足水库输水氯化物不超过250 mg/L为前提,利用青草沙水域氯化物过程的低谷低盐区域取水调度技术,解决长江特枯水情下的青草沙水库库容不能满足供水需求的难题.结合陈行水库实际运行经验,同时经数值模拟计算验证,采用该调度技术,可以解决目前青草沙水库有效库容不能满足设计供水规模要求的问题,进一步扩大青草沙水库的供水能力,有效提高水库利用效益和保证水源地安全运行,同时可以为国内外同类河口水库供水潜能的开发利用提供借鉴.     

VAc／MMA半连续乳液共聚合的研究：Ⅰ种子乳液共聚合

以过硫酸铵为引发剂，十二烷基硫酸钠为乳化剂，于７０℃下进行了ＶＡｃ＝ＭＭＡ种子乳液共聚合。试验考察了组分和操作条件对体系稳定性，聚合速度及组成分布等的影响，同时，从理论上给出了加料速率与体系稳定性因子间的关系。     

Round-Robin Test on methods for determining chloride transport parameters in concrete

This paper presents the results of a Round-Robin Test on methods for determining chloride transport parameters in concrete, carried out by the Technical Committee TC 178-TMC: “Testing and Modelling Chloride Penetration in Concrete” in which 27 different laboratories around the world have participated, using 13 different methods, in triplicate specimens, for 4 different mixes of concrete cast with different binders. Four different groups of methods have been tested: Natural diffusion methods (D), Migration methods (M), Resistivity methods (R) and Colourimetric methods (C). The statistical treatment of the data has been carried out according to the International Standard ISO 5725-2:1994 for the determination of the accuracy (trueness and precision) of measurement methods and results. Part 2: Basic method for the determination of the repeatability and reproducibility of a standard measurement method. In order to make an evaluation of these methods, four indicators have been identified and within each of them, several sub-indicators have been assigned. According to this system of classification, the methods have been classified following each indicator (trueness, precision, relevance and convenience), and also globally, by assigning different factors of importance, F.I., to the different indicators.     

Electrochemical corrosion behavior of carbon-based thin films in chloride ions containing electrolytes

Commercially available carbon-based thin films consisting of single layers of amorphous diamond-like carbon or multilayers of crystalline TiAlN or CrN with diamond-like carbon top coatings were evaluated in relation to their electrochemical corrosion behavior in chloride ions containing electrolytes. The hardened working steel (an alloy of 0.9% C, 4.1% Cr, 4.9% Mo, 1.8% V, 6.4% W) was used as a substrate material.The potentiodynamic corrosion behavior of coated samples was tested in 3.5 wt.% NaCl solution and Hank's balanced body solution, HBBS (0.89 wt.% NaCl, further chlorides, sulfates, carbonates and phosphates). The multi-layers TiAlN + a-C:H:W and CrN + a-C:H:W exhibited only a minor improvement in corrosion resistance. Single layers of amorphous diamond-like carbon coating without hydrogen (a-C) spall off during the corrosion tests in chloride containing media. A minor improvement of the corrosion resistance is possible. The a-C:H and the a-C:H:Si, which contain hydrogen, showed the best corrosion resistance with a 100 times lower corrosion current density.     

聚醋酸乙烯酯共聚胶液的改性研究

聚醋酸乙烯酯作为常用的胶粘剂之一,有明显的优点,但随着环保和绿色生活的要求,其有毒和耐水性等缺陷影响了其更好发展.本研究利用醋酸乙烯酯与其它烯类单体的共聚,制备出了无毒、快干、胶接强度高、耐水性好的高性能聚醋酸乙烯酯共聚改性胶液,并对其相关影响因素及工艺条件的确定进行了讨论.     

阴离子交换树脂吸附镉的动力学研究

研究了强碱性阴离子交换树脂吸附镉的主要动力学因素。通过实验找出了过程的限制环节，推算出交换反应的活化能、反应级数及动力学方程。     

Quantitative study of the kinetics of hydrogen evolution reaction on aluminum surface and the influence of chloride ion

The behaviors and kinetics of hydrogen evolution reaction (HER) on pure aluminum with passive film in the presence and absence of chloride ion are quantitatively investigated by using the tip generation/substrate collection mode of scanning electrochemical microscopy (SECM) with dual Al/Pt ultramicroelectrode (UME) as tip electrode and Pt UME as substrate electrode. The standard rate constants k⁰ and transfer coefficients α_H of HER in ClO₄⁻- and Cl⁻-containing solution are 6.9 × 10⁻⁷ cm/s and 0.22, 7.1 × 10⁻⁶ cm/s and 0.19, respectively. Results show that the kinetic of HER is slow and the destruction of Cl⁻ on passive film can significantly promote the HER on Al surface. Moreover, these α_H far less than commonly used 0.5 in corrosion research, can explain the great difference between theoretical Tafel slopes and experimental results. Besides, the existence of current plateau in Al electrode explains the large difference in corrosion potential during parallel testing.     

Stress corrosion cracking in 316L stainless steel bellows of a pressure safety valve

There were three consecutive occurrences of bellows failure in a particular pressure safety valve (PSV) of a petroleum refinery within a time span of one week. The bellows were made of 316L grade austenitic stainless steel, and the PSV was mounted on one of the vessels of vacuum gas oil service in a hydrocracker unit. Metallurgical analysis of the failed bellows revealed that the failure had occurred by stress corrosion cracking (SCC). It was found that the SCC was promoted in the bellows due to the presence of high amount of chloride ions in the operating environment. Studies confirmed that SCC had initiated from the outer surface of the bellows and propagated inwards, resulting in leakage of hydrocarbon from the PSV. The source of chlorine in the environment was identified. It was discovered that SCC in the bellows was caused due to a previous failure in the heavy polynuclear aromatics (HPNA) absorption bed located upstream the process flow line. This failure was due to the presence of high concentrations of chlorine in the granulated activated carbon that was used in the HPNA absorption bed. During the repair of the HPNA bed, there was deposition of carbon soot on the body of the PSV. This carbon soot was the source of chloride ions for SCC to occur in the bellows. Generally, in chloride SCC, crack propagation in 316L SS takes place by transgranular mode. In the present case, however, the crack propagation was predominantly by intergranular mode. The metallurgical factors responsible for this change in micro-mechanism of crack propagation during SCC have been discussed.     

Effect of fine crack width and water cement ratio of SHCC on chloride ingress and rebar corrosion

SHCC (Strain Hardening Cement-based Composite) is a material known for its strain-hardening behavior under tensile and bending stress and its characteristic numerous small cracks. SHCC is expected to show superior durability because of the fineness of the cracks. In this study, chloride ingress through cracks into SHCC and progress of rebar corrosion in three mixtures of SHCC with various water-cement ratios were investigated. Through a chloride solution immersion test, it was confirmed that chloride could penetrate through even very fine cracks. The resistivity of cracked SHCC against chloride ingress is mainly governed by the accumulated crack width and the water cement ratio. Chloride pre-mixed SHCC specimens were left in a high-temperature, high-humidity chamber for 11 months to promote rebar corrosion. While the accumulated crack width and the water cement ratio were both influential to an increase in corrosion area, only the water cement ratio had bearing on corrosion loss.