电位滴定法测定啤酒中氯离子含量

本文讨论了用银电极电位滴定法测定啤酒中氯离子含量。在20ml啤酒样品,0.5ml 6mol/LHNO_3和2.0ml 0.1g/mlKNO_3组成的体系中,测得滴定终点电位值为270±2mv。三种不同标准添加量的方法回收率都大于98.6％。方法精密度:同一样品连续测定12次,标准偏差为0.74,变异系数0.65％。同时测得三种国产啤酒中氯离子含量为114～152mg/L。     

焙烧还原条件下硬脂酸钠改性水滑石的制备及应用

以镁铝碳酸根型水滑石MgAl-CO₃-LDHs(LDHs)为前驱体,硬脂酸钠(NaSt)为改性剂,通过焙烧还原法在硬脂酸钠的溶液中制备硬脂酸钠改性水滑石LDHs-NaSt,采用X射线衍射仪(XRD)、傅里叶转变红外光谱仪(FTIR)和扫描电镜(SEM)对结构进行表征,并研究不同改性剂加入量条件下得到的改性水滑石对聚氯乙烯(PVC)热稳定性能的影响。结果表明,在氮气保护下,焙烧后的水滑石可以成功复原,硬脂酸钠对LDHs的改性为表面改性,但影响复原水滑石的结晶度。改性水滑石可以改善PVC的初期着色性和长期热稳定性,随着改性剂浓度的增大,当NaSt与LDHs质量比为1∶4时,静态热老化时间可以达到370 min,比未改性水滑石热稳定性能提升了61%。     

模网混凝土耐久性问题及防护措施

模网混凝土在使用过程中出现面层砂浆开裂、钢模网锈蚀的现象。主要通过材料复合的方法，在普通水泥砂浆中加入聚合物形成聚合物水泥砂浆，提高普通砂浆的柔韧性和抗渗能力，并将改性砂浆作为模网混凝土的保护层保护内部钢模网不受锈蚀。     

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.     

Sensitivity of uncertainties in performance prediction of deteriorating concrete structures

Deterioration models for the condition and reliability prediction of civil infrastructure facilities involve numerous assumptions and simplifications. Furthermore, input parameters of these models are fraught with uncertainties. A Bayesian methodology has been developed by the authors, which uses information obtained through health monitoring to improve the quality of prediction. The sensitivity of prior and posterior predicted performance to different input parameters of the deterioration models, and the effect of instrument and measurement uncertainty, is investigated in this paper. The results quantify the influence of these uncertainties and highlight the efficacy of the updating methodology based on integrating monitoring data. It has been found that the probabilistic posterior performance predictions are significantly less sensitive to most of the input uncertainties. Furthermore, updating the performance distribution based on ‘event’ outcomes is likely to be more beneficial than monitoring and updating of the input parameters on an individual basis.     

2,2'-亚甲基双(4-叔丁基苯基)磷酰氯的制备及表征

以2,2'-亚甲基-双(4-叔丁基苯)酚和三氯氧磷为原料,通过滴加缚酸剂和催化剂三乙胺,反应生成了2,2'-亚甲基双(4-叔丁基苯基)磷酰氯。主要研究了加料顺序、时间、温度和溶剂量对反应产物和收率的影响。当滴加三乙胺,加入25 mL溶剂,反应时间2 h和反应温度为45℃时收率可以达到68%。对产物进行了傅里叶红外变换光谱仪(FTIR)、核磁共振仪(NMR)、质谱仪(MS)和差式扫描量热分析(DSC)表征,各项检测表明,合成的产物为2,2'-亚甲基双(4-叔丁基苯基)磷酰氯。     

4A分子筛对EVA/APP/PETA复合材料阻燃性能的影响

以聚磷酸铵(APP)和聚对苯二甲酰乙二胺(PETA)复配制备了无卤阻燃乙烯-醋酸乙烯共聚物(EVA)/膨胀型阻燃体系(IFR)复合材料,通过极限氧指数仪、热失重分析仪(TG)和扫描电镜(SEM)分析了4A分子筛对复合材料的阻燃性能、热稳定性能和复合材料残炭表面形貌的影响。结果表明,当4A分子筛添加量为2%时,复合材料的极限氧指数达39%,比未添加4A分子筛的提高了4%,垂直燃烧达到V-0级。SEM表明,4A分子筛的加入提高了样品残炭表面致密度。     

含磷化合物改性氢氧化镁及其在EVA中应用研究

采用钛酸酯偶联剂201、311和含磷有机阻燃剂磷酸甲酚二苯酯、亚磷酸二甲酯对氢氧化镁进行表面改性,以红外光谱、热重、电镜和粒度分析为表征手段考察不同种类的改性剂对氢氧化镁表面改性的影响.结果表明,磷酸甲酚二苯酯改性氢氧化镁能提高10℃分解温度,增加高温下质量保持率;钛酸酯偶联剂311改性氢氧化镁能降低平均粒度,使粒径分...