POTENTIAL OF SEM-EDX FOR THE ANALYSIS AND CHARACTERIZATION OF DIFFERENT MATERIAL BELONGING TO HISTORIC BUILDINGS

Chemical and biological agents are responsible of our cultural heritage deterioration. Before the intervention it is necessary to know very well the causes of decay. After a visual examination now it is possible to use nondestructive techniques of diagnosis, which can indicate very well the surface status of monuments, historical buildings, or other artworks, and offer very useful complementary data for the restoration interventions. Scanning electron microscopy (SEM) has been extensively used for the material characterization of objects of artistic and archaeological importance, especially in combination with energy dispersive X-ray microanalysis (SEM/EDX) examines a sample surface with a finely focused electron beam. The electron bombardment leads to the emission of secondary electrons, to backscattering of high energy primary electrons and creation of element specific X-rays. The low energy secondary electrons originates from the top nanometers of the sample. The corresponding images clarify the distribution of different materials (Z-contrast images). In this mode, the information depth is in the range of 1 μm. A big advantage of SEM compared with optical microscopy besides high magnitudes is the depth of focus. With SEM a particular surface can be inspected using angled view while the surface is in focus. EDX (or EDS) analysis coupled with SEM provides elemental analysis on an area as small as nanometers in diameter. The impact of the electron beam on the sample produces X-rays that are characteristic of the elements found on the sample. The measured intensities yield quantitative information on the element composition and distribution. The depth from where the X-rays originate depends on the material and the used primary electron energy. In this paper, the current possibilities and future potential of SEM-EDX for the analysis and characterization of different material belonging to historic buildings have been illustrated with a number of selected examples (Château d'If, Metapontum tombs, Bagnoli Thermae) having the aim to answer one or more questions derived from human history or the history of art. This research confirmed the versatility of these techniques and the importance to preserve the cultural heritage as complex reality, fruit of manifold exchanges between cultures and civilizations.