X‐ray Diffraction Mapping for Cultural Heritage Science: a Review of Experimental Configurations and Applications

Abstract

X-ray diffraction (XRD) mapping consists in the acquisition of XRD patterns at each pixel (or voxel) of an area (or volume). The spatial resolution ranges from the micrometer (mXRD) to the millimeter (MA-XRD)s cale, making the technique relevant for tiny samples up to large objects. Although XRD is primarily used for the identification of different materials in (complex) mixtures, additional information regarding the crystallite size, their orientation, and their indepth distribution can also be obtained. Through mapping, these different types of information can be located on the studied sample/object. Cultural heritage objects are usually highly heterogeneous, and contain both original and later (degradation, conservation) materials. Their structural characterization is required both to determine ancient manufacturing processes and to evaluate their conservation state. Togetherw ith other mapping techniques, XRD mapping is increasingly used for these purposes. Here, the authors review applicationsa sw ell as the various configurations for XRD mapping (synchrotron/laboratory X-ray source, poly-/monochromatic beam,micro/macro beam, 2D/3D, transmission/reflectionm ode). On-going hardware and software developments will further establish the technique as ak ey tool in heritage science.[a] Dr.

High-resolution non-invasive X-ray diffraction analysis of artists’ paints

“…It is this factor that allows the use of a laboratory source despite the orders of magnitude reduction in brilliance, also reducing the risk of radiation damage. Simulations show that acquisition times can be shortened which is especially enabling for XRD mapping applications [23], particularly when combined with the use of a focusing polycapillary optic [95] to achieve a small beam spot on the sample. Implementation with microcalorimeters will also allow access to lower X-ray energies/larger d-spacings, subject to the limitations imposed by window and air absorption if samples are mounted in free-space.…”

“…Uneven surfaces, such as impasto on paintings, can present challenges to this type of instrument and adversely affects resolution and precision. Nevertheless, portable XRD instruments for non-invasive studies are becoming increasingly wellestablished [23] with some impressive results in recent years [5].…”

Synchrotron micro-XRD and micro-XRD-CT reveal newly formed lead–sulfur compounds in Old Master paintings

“…SR-m-XRD and SR-m-XRD-CT both rely on the use of a micrometric synchrotron beam to collect XRD patterns at each pixel (or voxel) of an area (or volume). 29 With SR-m-XRD, 2D distribution maps of the crystalline compounds present in the samples are obtained, revealing the build-up of various paint layers. SR-XRD-CT enables to "slice" through the sample, thus potentially revealing the three-dimensional buildup of the inorganic compounds present.…”

Detectors and Cultural Heritage: The INFN-CHNet Experience

“…Applications encompass paintings, manuscripts, ceramics, metallic alloys, fossils, studied to understand origin, counterfeiting, realization processes or degradation phenomena. A review on the application of XRD imaging for CH studies has recently been published by V. Gonzalezet al [113].…”