SYNCHROTRON INFRARED NANO-SPECTROSCOPY FOR NANO-SPECIATION OF METAL CORROSION PRODUCTS

The understanding of chemical and physical behavior of materials, especially metals and their alloys, is of utmost importance for industrial and technological applications, development of new materials and preservation of cultural heritage. The use of complementary analytical techniques has allowed a better understanding of corrosion mechanisms, and results obtained by Raman micro-spectroscopy, for example, have been complemented by FTIR and XRD. When focusing on the development of new materials and proposition of preservation strategies, the understanding of corrosion processes and of their very initial steps (nanometric scale) is fundamental. SERS reaches such lateral resolution if TERS is used, however, it cannot be universally applied and needs to be complemented by other techniques. In this work it is presented the potentials of a recent installed technique at the Brazilian Synchrotron Light Laboratory (LNLS), which can be used for nano-speciation of corrosion products, complementing investigation carried out by, for example, Raman micro-spectroscopy and TERS. It is Synchrotron Infrared Nano-Spectroscopy (SINS), which allows the investigation of both chemical nature and physical distribution of corrosion products. The infrastructure presented at LNLS is one of the few available in the world. As a model system, thin films of Pb exposed to formic acid were used.

深入理解材料（尤其是金属及其合金）的化学与物理行为，对于工业与技术应用、新材料开发以及文化遗产保护均具有至关重要的意义。采用互补式分析技术可进一步深化对腐蚀机理的认知，例如通过拉曼显微光谱（Raman micro-spectroscopy）获取的研究结果，可借助傅里叶变换红外光谱（Fourier Transform Infrared Spectroscopy，FTIR）与X射线衍射（X-ray Diffraction，XRD）进行补充完善。当聚焦于新材料开发与保护策略制定时，掌握腐蚀过程及其初始阶段（纳米尺度）的相关信息是核心前提。若采用针尖增强拉曼光谱（Tip-Enhanced Raman Spectroscopy，TERS），表面增强拉曼散射（Surface-Enhanced Raman Scattering，SERS）可实现该类横向分辨率，但该方法无法普适性应用，仍需依托其他技术进行补充。本研究介绍了巴西同步辐射光实验室（Laboratório Nacional de Luz Síncrotron，LNLS）新近安装的一项技术的应用潜力，该技术可用于腐蚀产物的纳米形态表征，能够补充拉曼显微光谱与针尖增强拉曼光谱等手段的研究结果。该技术即为同步辐射红外纳米光谱（Synchrotron Infrared Nano-Spectroscopy，SINS），可同时实现腐蚀产物的化学性质与物理分布表征。LNLS所配备的该类设施为全球少数可用的同类装置之一。本研究采用暴露于甲酸中的铅薄膜作为模型体系。