光纤光栅腐蚀传感器

提出了一种测量钢筋腐蚀的新型传感器.这种传感器将光纤光栅拉伸后固定在圆形钢筋的表面,在钢筋被腐蚀后,光纤光栅所受到的拉伸应变将被释放,光纤光栅的反射光波长发生变化,通过测量光纤光栅的波长就可以测得钢筋腐蚀程度.这种传感器测量准确度优于±0.1 μm,测量范围约12 μm,可用于混凝土结构中钢筋腐蚀的早期监测.     

一种监测钢筋腐蚀的光纤光栅传感器的研究

钢筋腐蚀是导致钢筋混凝土结构耐久性劣化的最重要因素之一。钢筋腐蚀将导致钢筋体积大大增加,混凝土保护层开裂、剥落,结构承载力下降,甚至倒塌。基于光纤布拉格光栅应变传感器的原理,根据钢筋腐蚀体积膨胀,提出了一种新的钢筋腐蚀光纤光栅传感器及温度补偿方法。传感器构造是在两根紧靠的钢筋中心附近粘贴光纤光栅,由于钢筋腐蚀体积膨胀,钢筋直径增加将转变成布拉格光纤光栅的应变,从而实现对钢筋腐蚀程度及速率的监测。传感器的监测原理是设置一个钢筋腐蚀光纤光栅传感器来监测由于钢筋腐蚀和温度变化引起的光栅应变,同时单独设置一个不锈钢光纤光栅传感器来测量温度引起的光栅应变。这两个光纤光栅传感器的应变监测,可分离出钢筋由于腐蚀所引起的体积变化。在混凝土结构中埋入封装的传感器,通过监测光纤光栅波长的漂移可以直接测量钢筋腐蚀程度,而且不受腐蚀因素的影响,可用于混凝土结构中钢筋腐蚀的早期监测。最后通过实验标定了钢筋腐蚀率与光栅波长位移的关系。     

基于掺铒光纤的微型光纤法布里-珀罗干涉传感器

提出了一种化学腐蚀掺铒光纤制作微型光纤法布里-珀罗干涉传感器的方法。通过对掺铒光纤进行化学腐蚀,形成凹槽,再与单模光纤直接熔接制作而成。实验制作的微型法布里-珀罗干涉传感器干涉条纹光滑,对比度达到15dB。对该微型光纤法布里珀罗干涉腔进行了应变和温度传感实验。实验结果表明,在0-600με￡内,波谷移动随应变改变的灵敏度达到1．7pm／με,线性度为0．9998,从73～23℃,波谷移动随温度改变的灵敏度3．9pm／℃,线性度为0．9982。该方法制作的微型光纤法布里-珀罗传感器具有操作简单,一次成型,制作成本低的优点。     

基于光谱特征分析的光纤光栅腐蚀传感器研究

针对航空航天领域铝合金结构服役过程腐蚀监测需求,提出了一种基于铝质细管结构的预载荷型光纤光栅腐蚀传感器。给出了铝合金结构腐蚀在役监测机理,得到光纤光栅反射光谱特征与铝质细管厚度变化之间的理论关系模型,构建了酸碱环境下的光纤光栅腐蚀监测试验系统。通过在细管内部配置不受力且仅感受温度变化的光纤光栅传感器,解决了被测目标的温度与应力交叉敏感问题。研究表明,这种铝质细管封装设计不仅可以感受腐蚀对其力学性能的影响,还能够屏蔽外界腐蚀因素对管内光纤感知器件的干扰。随着金属管腐蚀程度加深,其管壁逐渐变薄,光纤光栅反射光谱逐渐向短波长方向偏移,且管壁厚度变化与光栅中心波长偏移量之间呈较好单调关系。这些特性能够为进一步开展基于光纤感知器件的机械结构在役腐蚀监测研究提供有益帮助。     

基于光纤气泡级联的高灵敏度马赫曾德干涉液体折射率传感器

通过化学腐蚀方法制作了一种基于光纤气泡级联马赫曾德干涉液体折射率传感器.在细芯光纤两端熔接切割端面被腐蚀的单模光纤,构成气泡-细芯光纤-气泡结构,该结构中两个气泡耦合光场,细芯光纤作为传感臂,构成光纤马赫曾德干涉仪.对该传感器的干涉谱能量随折射率的变化规律进行了研究,结果表明:干涉谱的能量与环境折射率之间存在较好的线性关系,同时波长变化对环境折射率变化不敏感;当外界折射率变化范围在1.345~1.389时,传感器的灵敏度为-216.21dB/RIU.该传感器在生物化学领域有较好的应用前景.     

基于腐蚀光纤的温度及葡萄糖溶液浓度传感器

提出并制备了一种基于本征倏逝波原理的温度及葡萄糖溶液浓度传感器.通过研究腐蚀包层厚度与透射光谱之间的关系,确定较为合适的腐蚀厚度.将标准单模光纤包层腐蚀至2.4μm,利用光纤倏逝波对外界介质变化敏感的原理,通过测量输出光功率的变化量实现温度及葡萄糖溶液浓度传感.实验结果表明:传感器在1070℃的温度范围内具有9.58×10~(-3) dBm/℃的灵敏度,线性度达到99.36%;在葡萄糖溶液03%的浓度范围内具有0.126dBm/(g/L)的灵敏度,线性度达到97.95%.该传感器的响应时间小于30s,具有操作简便、测量准确度高、重复性好、适用范围广等优点,具备良好的应用价值.     

钢筋腐蚀监测的光波导传感方法原理探索

本文提出了一种用于混凝土结构钢筋腐蚀监测的光波导传感方法,该方法利用金属膜层局部取代光波导的介质包层,构成腐蚀敏感膜,从而获取金属腐蚀信息.本文依据波导理论讨论了该方法的原理,利用电化学方法在721比色皿的石英玻璃上证实了平面光波导腐蚀传感方案的可行性,并进一步用电镀方法制备出了光纤腐蚀传感器(FOCS)实验样品,取得了预期实验结果.     

基于微加工工艺的光纤消逝场传感器及其长度特性研究

用硅光刻工艺和二氧化硅湿法腐蚀工艺制作了针状封装结构的光纤消逝场传感器.该结构的传感器体积小、试剂消耗量少,减轻了测量过程中光纤的变形,密封的结构可以有效地防止传感器受到污染.从理论和实验角度研究了不同长度的光纤消逝场传感器的测量结果,分析了传感光纤长度对传感器吸光度的影响,指出随着传感器传感光纤长度的继续增加,会使后续增加的传感光纤对传感器灵敏度的贡献越来越小. 关键词： 硅光刻工艺 针状封装 光纤消逝场传感器 传感光纤长度     

基于光纤微腔的温度及折射率同时测量型传感器

基于多光束干涉原理,设计了一种基于光纤微腔的温度及折射率同时测量的反射型光纤传感器.该传感器将渐变折射率多模光纤的一端用氢氟酸腐蚀形成一个空气腔,带空气腔的渐变折射率多模光纤一端和单模光纤熔接,另一端切平构成传感头.实验选取渐变折射率多模光纤的长度为538.1μm,空气腔长度为40.8μm.结果表明:光纤微腔结构所形成的多光束干涉光谱条纹对比度与光纤微腔外的溶液折射率相关,干涉波峰移动与环境温度相关,通过监测条纹对比度和干涉波峰的移动,可以实现对折射率和温度的同时测量.当折射率在1.341 5~1.432 0RIU变化时,反射强度对折射率的灵敏度为57.24dB/RIU;当温度在30℃~70℃之间变化时,谐振波长对温度的灵敏度为12.3pm/℃,可检测到的最小温度变化为1.2℃,测得最小折射率变化为3.4×10-4.该传感器也可应用于其他参量的测量,具有良好的应用前景.     

氧化石墨烯集成腐蚀型81°倾斜光栅生物传感器

为了改善普通81°倾斜光纤光栅在生化检测中灵敏度低、检测极限不理想等问题,提出一种基于氧化石墨烯修饰腐蚀型81°倾斜光纤光栅的牛血清蛋白生物传感器,分析了该传感器的原理与传感特性。使用氢氟酸溶液腐蚀减小光栅直径,提高其对折射率的灵敏度,并用氧化石墨烯修饰光栅,然后将牛血清蛋白单克隆抗体固定于光栅表面,用于对牛血清蛋白的特异性检测。实验结果表明,氧化石墨烯集成腐蚀型81°倾斜光纤光栅生物传感器对牛血清蛋白的检测范围为0.15～15nmol/L,检测极限为～0.165nmol/L,其线性响应区域的灵敏度为～182pm/(nmol·L~(-1)),传感器的检测范围较氧化石墨烯集成标准直径81°倾斜光纤光栅有所降低,但其灵敏度提高了5.3倍,且检测极限有较大的改善。     

NiCrBSi涂层在酸性介质中耐腐蚀性能

研究了NiCrBSi涂层在沸腾的H2SO4和HCl溶液中的耐腐蚀性能,分析了其腐蚀过程.实验结果表明,NiCrBSi涂层具有良好的耐腐蚀性能,腐蚀过程主要为腐蚀剂通过涂层中的通孔进入涂层,引起腐蚀,腐蚀一定时间后,在涂层与基体之间产生腐蚀产物,涂层鼓泡.     

Cohesive zone modelling of anodic dissolution stress corrosion cracking induced by corrosion product films

Damage mechanics based on the cohesive zone model were applied to study the anodic dissolution stress corrosion cracking (SCC) in flat and U-shaped edge-notched specimens. The simulation results show that corrosion product films (CPFs) facilitate crack initiation in SCC due to the CPF-induced stress and CPF rupture. In the flat specimen, SCC susceptibility increases with the CPF thickness and CPF Young’s modulus, while it decreases with CPF fracture strength. For the U-shaped edge-notched specimen, the normalised threshold stress intensity factor K_ISCC/K_IC decreases with the CPF thickness and notch depth.     

Corrosion behaviour of AISI 304 stainless steel with Cu coatings in H2SO4

The work addresses the influence of cementation and electrodeposition of copper coatings on the corrosion resistance of AISI 304 stainless steel immersed in 30 wt.% H₂SO₄ at temperatures of 25 and 50 °C. Corrosion process was evaluated by gravimetric tests, DC measurements and electrochemical impedance spectroscopy (EIS). The specimen surfaces were analysed by scanning electron microscopy, X-ray photoelectron spectroscopy (XPS) and X-ray diffraction. The corrosion performance of AISI 304 stainless steel in sulphuric acid solution was greatly improved by copper coatings. The amount of copper deposited by the cementation process was sufficient to protect the stainless steel of corrosion. A greater amount of copper obtained by electrodeposition treatments does not supply further improvement in the corrosion behaviour. The improved corrosion resistance is related to copper dissolution at the initial stages of immersion tests and the presence of Cu²⁺ in the solution, which makes the medium more oxidizing, increasing the stability of the passive layer. In addition, the presence of copper at the surface reduces the overpotential of cathodic reaction, enabling the transition from an active region to the passive one.     

Raman study of a deuterated iron hydroxycarbonate to assess long‐term corrosion mechanisms in anoxic soils

In several contexts such as cultural heritage, oil and gas or nuclear waste disposal, the long‐term corrosion mechanisms of iron in anoxic soils are studied. For this purpose, corrosion layers formed on ferrous archaeological artefacts from the site of Glinet (16th century, Normandy, France) were characterised. The main phases identified are siderite (FeCO₃), chukanovite (iron hydroxycarbonate: Fe₂(OH)₂CO₃ and magnetite (Fe₃O₄). In order to provide reliable Raman references for further studies on carbonated systems, the iron hydroxycarbonate (chukanovite) was synthesised on iron discs. The corrosion mechanisms were investigated by re‐corroding the archaeological samples in a deuterated solution. Raman characterisation on cross sections inside the layer revealed the presence of deuterated chukanovite, allowing the deuterium tracing of the spreading of the corrosion. A set of chukanovite samples was synthesised with various D/H ratios. Using these reference data, the proportion of deuterated chukanovite in re‐corroded artefacts was evaluated, and the corrosion rate was estimated as less than 1.6 µm/year. Copyright © 2010 John Wiley & Sons, Ltd.     

Electrochemical corrosion behavior,Vickers microhardness,and microstructure of Co–Cr and Ni–Cr dental alloys

Electrochemical corrosion behaviors, Vickers microhardness, microstructure, and electrical properties of Magnum H50 (Co=64.5%, Cr=29%, Mo=6.5% ) and Nikkeli–Kromi–Polttosekoitus (Ni=65.2%, Cr=22.5%, Mo=9.5%, X=2.8% Nb, Si, Fe, and Mn) dental alloys have been investigated. The corrosion potential for the Co_64.5Cr₂₉Mo_6.5 alloy in HCl was higher than that of the Ni_65.2Cr_22.5Mo_9.5X_2.8 alloy. The corrosion rate with 0.5 M HCl for the Ni_65.2Cr_22.5Mo_9.5X_2.8 alloy was measured as being high and the corrosion resistance as being small as compared with the values for the Co_64.5Cr₂₉Mo_6.5 alloy. Vickers hardness of the Co_64.5Cr₂₉Mo_6.5 alloy was higher than that of the Ni_65.2Cr_22.5Mo_9.5X_2.8 alloy. Also Vickers hardness values of the used alloys were decreased by increasing indentation load. The thermal conductivity and minimum shear stress values of the used alloys are calculated.     

Corrosion Products Formed on Mild Steel Samples Submerged in Various Aqueous Solutions

Corroded samples, from the steel shell of an industrial evaporator system were investigated. A protective magnetite layer had formed, which subsequently dissolved in localised areas, resulting in failure of the shell. To clarify the mechanisms involved, mild steel samples of similar composition to the steel shell were submerged in the condensate and experiments were performed at room temperature and at 90°C under both static and dynamic conditions for exposure times up to 30 days. Control samples were submerged in deionised water under similar conditions. The dynamic corrosion rates in the industrial condensate were a factor of 2 higher than the rates for the deionised water, whilst static corrosion rates, measured in both media, were lower by a factor of 3 to 4 found for the dynamic experiments. The corrosion products were identified by means of CEMS analyses. The main components were magnetite and oxyhydroxides of iron. Additional to the species mentioned, -Fe₂O₃, goethite and hematite formed.     

Influence of gamma radiation on morphology structure,electrochemical corrosion behavior and hardness of Ni–Cr based alloys

This study evaluates the effects of gamma radiation on structure, electrochemical corrosion behavior and Vickers hardness of commercial dental Nikkeli–Kromi–Polttosekoitus [Ni_65.2Cr_22.5Mo_9.5X_2.8 (X=Nb, Si, Fe and Mn)] alloy. The corrosion rate of Ni_65.2Cr_22.5Mo_9.5X_2.8 (X=Nb, Si, Fe and Mn) alloy with 0.5 M HCl is increased with increasing the exposure rate of gamma radiation. The corrosion resistance of Ni_65.2Cr_22.5Mo_9.5X_2.8 (X=Nb, Si, Fe and Mn) is varied and reaches a minimum value at 30 KGy. The corrosion potential value also is varied and reaches its highest value at 30 KGy. The Vickers hardness value of Ni_65.2Cr_22.5Mo_9.5X_2.8 (X=Nb, Si, Fe and Mn) alloy is decreased by increasing the gamma radiation dose. Also it is obvious from our results that the effects of gamma radiation at the surface are much higher as compared with deeper parts and the structure of the alloy is changed due to its exposure to gamma radiation.     

A model for the initiation of reaction sites during the uranium–hydrogen reaction assuming enhanced hydrogen transport through linear oxide discontinuities

A model for the initiation of hydride sites on uranium metal is described for hydride attack in the region of linear discontinuities in the surface oxide film. The model considers the effect of variations in hydrogen permeation through such discontinuities due to intrinsic oxide and metal parameters and operational variables. Expressions are derived for the time dependence of the hydrogen concentration in the metal and the maximum attained hydrogen concentration in terms of these parameters. The derived expressions therefore relate hydride precipitation time in the metal underlying any oxide discontinuity to the physical width of the discontinuity, its length, the hydrogen diffusion coefficient down the oxide discontinuity, the hydrogen diffusion coefficient in the underlying metal lattice and the hydrogen concentration in the oxide discontinuity at the gas-oxide interface. The model can therefore account for how changes in operational conditions such as hydrogen pressure may change hydride attack times in the region of such oxide discontinuities. The model can also explain why, after any given time, hydride attack may occur at some but not all of the oxide discontinuities surrounding any individual metal grain. The model also considers how hydride attack times may, or may not, be modified by the intersection of linear discontinuities in the surface oxide film. Finally, the model is able to explain the reported experimental observation that oxide discontinuities having only a short rather than a long length are less preferred sites of hydride attack.     

Ce conversion and electrolysis surface treatments applied to A3xx.x alloys and A3xx.x/SiCp composites

The influence of different variables (stirring, degreasing, oxidant additions, pH, Ce concentration, anion type, time and temperature of immersion) on the optimization of Ce conversion and electrolysis coatings on both A3xx.x alloys and aluminium metal matrix composites A3xx.x/SiCp was evaluated in 3.5 wt% NaCl at 22 °C using potentiodynamic polarization. Ce treated surfaces presented better corrosion behaviour in chloride media than original material surfaces without treatment. Both treatments preferentially covered the intermetallic compounds and SiCp. The electrolysis afforded a higher degree of protection than conversion treatment because the coating was more extensive. Coating microstructure was analysed by scanning electron microscopy (SEM), atomic force microscopy (AFM) and X-ray photoelectron spectroscopy (XPS).     

Detection of stress corrosion cracking of high-strength steel used in prestressed concrete structures by acoustic emission technique

The stress corrosion cracking (SCC) of high-strength steel used in prestressed concrete structures was studied by acoustic emission technique (AE). A simulated concrete pore (SCP) solution at high-alkaline (pH ≈ 12) contaminated by sulphate, chloride, and thiocyanate ions was used. The evolution of the acoustic activity recorded during the tests shows the presence of several stages related respectively to cracks initiation due to the local corrosion imposed by corrosives species, cracks propagation and steel failure. Microscopic examinations pointed out that the wires exhibited a brittle fracture mode. The cracking was found to propagate in the transgranular mode. The role of corrosives species and hydrogen in the rupture mechanism of high-strength steel was also investigated. This study shows promising results for an potential use in situ of AE for real-time health monitoring of eutectoid steel cables used in prestressed concrete structures.