Study of Fe(II) sulphides in waterlogged archaeological wood

Abstract

Wet organic archaeological materials extracted from seawater may suffer damage as a result of degradation influenced by micro-organisms. One of the most common phenomena is indirectly induced by sulphate-reducing bacteria (SRB). Due to their metabolic activity in anoxic conditions, SRB generate hydrogen sulphide from sulphate ions present in seawater. When steel items are in contact with organic matter in presence of sulphides, corrosion of the metal leads to the precipitation of Fe(II) sulphides. These phases are responsible for dramatic post-excavation damage: their oxidation during storage or exhibition in museums leads to the formation of voluminous crystals, which may cause cracking and crumbling, and lead to the production of sulphuric acid. In order to characterize Fe(II) sulphides and their by-products, 13 waterlogged samples were analysed by environmental scanning electron microscopy, micro-Raman spectroscopy, and X-ray diffraction. Experiments were performed on untreated wood fragments, on a fragment of rope, and on mineral concretions scratched from the surface of wood remains, all extracted from different shipwrecks. Mackinawite was detected inside the fragments and between the fibres of the rope. Greigite was detected in scattered locations. Pyrite and sulphated phases, like gypsum and iron sulphates, were identified at the surface of the wood fragments and in the mineral concretions.     

钢筋混凝土桥梁在大气环境作用下的耐久性评估和剩余寿命预测

根据混凝土碳化及其引起的钢筋锈蚀的机理,建立了钢筋混凝土构件的劣化模型。利用Monte Carlo模拟方法分别研究了一般运营和密集运营两种荷载模型下钢筋混凝土桥梁的时变可靠性,讨论了保护层厚度、混凝土强度、钢筋锈蚀损失率对混凝土耐久性的影响。研究表明：在服役过程中,由于大气环境的作用,混凝土碳化、钢筋锈蚀、桥梁结构可靠指标不断降低,混凝土的耐久性能不断下降;混凝土保护层厚度和混凝土抗压强度对可靠度指标的影响明显,而钢筋腐蚀率的影响不是很明显。     

我国腐蚀成本及其防控策略

材料腐蚀是生产生活中的常见现象,严重的腐蚀不仅会造成材料失效,还可能诱发猝不及防的灾难性事故。了解与认识腐蚀问题,是保障人民群众生命财产安全的必然要求。为此,中国工程院针对我国腐蚀成本进行了调查研究。数据表明,2014年,我国腐蚀成本为21 278.2亿元人民币,约占当年国内生产总值的3.34%。腐蚀问题可防可控,通过实施防腐蚀顶层设计、加强腐蚀与防护研究、开发新型防腐蚀技术、推行防腐蚀经验标准、提高全民防腐蚀意识等方式,我国腐蚀防护水平将得以全面提升。     

注水点位置对空冷器腐蚀影响的实验研究

加氢裂化技术自投用以来,反应流出物空冷器（REAC）及其相联管道的腐蚀失效,便一直是制约其安全稳定运行的核心问题,设计制造、检测评估、腐蚀原因的评判、腐蚀垢物的分析等每一个相关环节的研究都成为国内外相关领域讨论的焦点。论文对加氢裂化装置中反应流出物空冷器的腐蚀问题进行了阐述,提出了研究注水点位置改变对腐蚀影响的方案,通过实验得出了结论,提出了下一步实验进行的方向和可行性。     

Fracture model for predicting concrete cover-cracking induced by steel corrosion based on interface bond state

Time-to-cracking of the concrete cover induced by the steel corrosion is one of the critical problems faced by engineers, operators and asset managers in making strategies for the maintenance and repairs of reinforced concrete (RC)structures affected by corrosion. In this paper, a theoretical model for predicting the time-to-cracking is derived by assuming the bond between the steel bar and the concrete as a linear combination of perfectly smooth and bonded. The model takes into account the characteristics of existing exiguous flaws and initial cracks in the concrete before the load acting on RC structures. The validity of the proposed model is preliminarily verified by comparing the obtained results with the available experimental results. A remarkable advantage of the proposed method is its application to the prediction of the service life of RC structures, made of the deformed steel bars as well as the round bars. By determining an experimental constant α, which is related to the interface bond state between the steel bar and the concrete, the service life of RC structures can be predicted using the proposed scheme. Analysis of major factors affecting the time-to-cracking demonstrates that the length of the initial crack affects the service life of RC structures significantly. Moreover, the larger cover thickness and the smaller diameter of the steel bar within a certain range are beneficial to prolonging the time-to-cracking.     

钢筋混凝土基础的腐蚀与防护措施

概括了钢筋混凝土结构的腐蚀机理,归纳了影响钢筋混凝土基础的主要腐蚀因素及其作用规律.最后,对基础腐蚀的防护提出一些措施及建议.     

油田地下管道的电化学保护研究

江苏油田有部分油井位于淮河入江的泄洪道内,由于泄洪道内油田地下管道所处的环境与陆上不同,造成比在陆上的腐蚀情况要严重。通过土壤腐蚀性和现场电化学保护研究,得到地下管道的保护电位和保护半径。     

钢筋混凝土基础的腐蚀与防护措施

概括了钢筋混凝土结构的腐蚀机理,归纳了影响钢筋混凝土基础的主要腐蚀因素及其作用规律.最后,对基础腐蚀的防护提出一些措施及建议.     

新型场发射器件中栅极的化学刻蚀制备

为了得到碳纳米管场发射器件的三极结构,设计了一种新型栅极.在电极的制作过程中使用普通的丝网印刷方法,然后运用化学刻蚀的手段进行双面刻蚀制备出带有小孔阵列的栅极.在栅极制作过程中通过改变酸液刻蚀的时间和浓度,可以腐蚀出不同形状的小孔.运用扫描电镜(SEM)和红外光谱(IR)分析,得到小孔的尺寸、形貌和刻蚀液的成份,然后在三极结构上加电压显示出孔的亮度图像,最后对器件结构进行模拟,算出在电场条件下的电子从阴极拉到阳极基板的轨迹.模拟结果和实验结果一致,从而实现了对场发射三极器件的优化.