Graphite resistive heated diamond anvil cell for simultaneous high-pressure and high-temperature diffraction experiments.

High-pressure and high-temperature experiments using a resistively heated diamond anvil cell have the advantage of heating samples homogeneously with precise temperature control. Here, we present the design and performance of a graphite resistive heated diamond anvil cell (GRHDAC) setup for powder and single-crystal x-ray diffraction experiments developed at the Extreme Conditions Beamline (P02.2) at PETRA III, Hamburg, Germany. In the GRHDAC, temperatures up to 2000 K can be generated at high pressures by placing it in a water-cooled vacuum chamber. Temperature estimates from thermocouple measurements are within +/-35 K at the sample position up to 800 K and within +90 K between 800 and 1400 K when using a standard seat combination of cBN and WC. Isothermal compression at high temperatures can be achieved by employing a remote membrane control system. The advantage of the GRHDAC is demonstrated through the study of geophysical processes in the Earth's crust and upper mantle region.

Synchrotron X-ray diffraction computed tomography to non-destructively study inorganic treatments for stone conservation.

The characterization of consolidating products formed by conservation treatments within Cultural Heritage (CH) materials is a burning issue and an analytical challenge, as non-destructive approaches, phase analysis, and volume distribution analysis are simultaneously required. This paper proposes the use of synchrotron X-ray diffraction computed tomography (XRDCT) to non-destructively study diammonium hydrogen phosphate (DAP) consolidating treatments for stone conservation. The mineralogical composition and localization of crystalline phases formed in a complex mixture have been explored and spatially resolved. The coexistence of hydroxyapatite and octacalcium phosphate has been finally demonstrated. The image analysis highlights the 3D distribution of calcium phosphates, their arrangement in a binding network down to the voxel scale, and their consolidating action. Above all, this study demonstrates the feasibility and high potential of XRDCT to investigate the interactions of conservation treatments with CH stone materials, and opens new analytical perspectives for XRDCT in conservation science and materials science.

Synchrotron radiation µ X-ray diffraction in transmission geometry for investigating the penetration depth of conservation treatments on cultural heritage stone materials.

The assessment of the penetration depth of conservation treatments applied to cultural heritage stone materials is a burning issue in conservation science. Several analytical approaches have been proposed but, at present, many of them are not fully exhaustive to define in a direct way the composition and location of the conservation products formed after inorganic mineral treatments. Here, we explored, for the first time, the analytical capability of synchrotron radiation µ X-ray diffraction in transmission geometry (SR-µTXRD) for the study of the crystal chemistry and penetration depth of the consolidating phases formed after the application of diammonium hydrogen phosphate (DAP) treatments on a porous carbonatic stone (Noto limestone). The SR-µTXRD approach provided unambiguous information on the nature of the newly formed calcium phosphates (hydroxyapatite, HAP, and octacalcium phosphate, OCP) with depth, supplying important indications of the diffusion mechanism and the reactivity of the substrate. Qualitative and semi-quantitative data were obtained at the microscale with a non-destructive protocol and an outstanding signal-to-noise ratio. The SR-µTXRD approach opens a new analytical scenario for the investigation of a wide range of cultural heritage materials, including natural and artificial stone materials, painted stratigraphies, metals, glasses and their decay products. Furthermore, it can potentially be used to characterize the penetration depth of a phase "A" (or more crystalline phases) in a matrix "B" also beyond the cultural heritage field, demonstrating the potential wide impact of the study.

What's underneath? A non-destructive depth profile of painted stratigraphies by synchrotron grazing incidence X-ray diffraction.

Many works of art are complex systems consisting of a core completed by the overlapping of several painted layers. In this work, we apply an innovative method based on grazing incidence X-ray diffraction (GIXRD) with synchrotron radiation (SR) to investigate polychrome stratigraphies with a completely non-destructive approach. The SR-GIXRD measurements provided direct and unambiguous compositional and stratigraphic information of the crystalline species lying in different layers. The investigations performed on a small fragment sampled from a painted terracotta statue allowed the identification of pigments, fillers, aggregates of the matrix and newly formed decay salts in micrometric-thin paint layers. Furthermore, the great potentiality of this study is the feasibility of depth profile investigations on multi-layered painted samples from cultural heritage objects without resorting to cross sectional analyses. Currently, the method is non-destructive but it can be potentially non-invasive in situations where small moveable artworks can be placed into the measurement chamber of the SR-XRD beamlines. The overall study paves the way to a new scenario of artwork investigations, shedding light on new unexplored approaches for non-destructive studies of cultural heritage objects, their conservation history and their interaction with the environment.

Synthesis of calcium oxalate trihydrate: New data by vibrational spectroscopy and synchrotron X-ray diffraction.

Calcium oxalate is found in nature in three different crystalline states determined by the number of H2O in the unit formula (whewellite CaC2O4·H2O, COM; weddellite CaC2O4·(2+x)H2O, COD and caoxite CaC2O4·3H2O, COT). The properties of these materials are relevant in the field of biomedicine, cultural heritage and mineralogy. In two previous papers, we have used X-ray diffraction and vibrational spectroscopy (infrared and Raman) to derive information on crystal and molecular structures of COM and COD. In this paper, we complete the synthesis and analysis on the third form, COT, and present a comparative study of the data collected from the three crystalline states. The experiments clearly highlight the role played by the H2O molecules linked within the structure by different kinds of hydrogen bonds. The vibrational assignment of the infrared and Raman bands are critically proposed. The fact relevant for the work in biomedicine, cultural heritage and crystallography is that a simple examination of the spectra allows quickly to determine the chemical nature of the material in an unknown sample even in a minute quantity or in awkward experimental conditions.

Single-crystal diffraction at the Extreme Conditions beamline P02.2: procedure for collecting and analyzing high-pressure single-crystal data.

Fast detectors employed at third-generation synchrotrons have reduced collection times significantly and require the optimization of commercial as well as customized software packages for data reduction and analysis. In this paper a procedure to collect, process and analyze single-crystal data sets collected at high pressure at the Extreme Conditions beamline (P02.2) at PETRA III, DESY, is presented. A new data image format called `Esperanto' is introduced that is supported by the commercial software package CrysAlis(Pro) (Agilent Technologies UK Ltd). The new format acts as a vehicle to transform the most common area-detector data formats via a translator software. Such a conversion tool has been developed and converts tiff data collected on a Perkin Elmer detector, as well as data collected on a MAR345/555, to be imported into the CrysAlis(Pro) software. In order to demonstrate the validity of the new approach, a complete structure refinement of boron-mullite (Al5BO9) collected at a pressure of 19.4 (2) GPa is presented. Details pertaining to the data collections and refinements of B-mullite are presented.

Stability and transformation mechanism of weddellite nanocrystals studied by X-ray diffraction and infrared spectroscopy.

This study is focused on the stability of weddellite, the dihydrate phase of calcium oxalate [CaC(2)O(4)·(2 + x)H(2)O], mainly detected in kidney stones and in oxalate films found on the surfaces of several ancient monuments. Its occurrence is a critical issue since, at environmental conditions, weddellite is unstable and quickly changes into whewellite, the monohydrate phase of calcium oxalate (CaC(2)O(4)·H(2)O). New single crystal X-ray diffraction experiments have been carried out, which confirm the structural model of weddellite previously published. Synthesised nanocrystals of weddellite have been kept under different hygrometric conditions in order to study, by X-ray powder diffraction, the influence of humidity on their stability. Moreover, the mechanism of transformation of weddellite nanocrystals has been investigated by infrared spectroscopy using D(2)O as a structural probe.