A model based on dislocation glide controlled by the nucleation and propagation of kink pairs in a high Peierls stress crystal is revisited and modified to account for changes in dislocation densities and segment lengths with temperature and stress. It is applied to the critical resolved shear stress (CRSS) for basal and prism plane slip in sapphire (alpha-Al2O3). According to agreed-upon knowledge on dislocations in sapphire, basal slip and prism plane slip are modelled with undissociated and dissociated dislocations, respectively. In the latter case, partial dislocations move independently. Amongst a number of sets of fitting parameters, good fits between experimental and modelled CRSS9s are obtained in the long segment limit over the whole range of temperatures by making use of physically sound parameters, including a stress dependence of the dislocation density.

The plastic deformation of Cr3+ -doped a-Al2 O3 (ruby) with four distinct Cr concentrations has been studied at temperatures between 900 and 1500 ^∘C. The mechanical tests indicate that the processes of dislocation multiplication and the adjustments of the slip velocity of these dislocations to the imposed strain rate in undoped a-Al2 O3 are not significantly affected by the Cr concentra temperature and the hardening increases with the Cr concentration. The critical resolved shear stress (CRSS) is fixed to a model based on dislocation glide controlled by the nucleation and propagation of kink pairs, modified to include the hardening due to Cr. Satisfactory fits are achieved with adjustable parameters close to those employed for undoped a-Al2 O3 .

A multi-approach study has been designed to evaluate the mannerist-style masterpiece of the Christ of the Expiration (Museum Brotherhood, Seville, Spain), a polychrome wooden paste sculpture of the 16th Century that was restored in the Andalusian Historical Heritage Institute (IAPH). During its intervention, a combination of two non-destructive prototypes were used to evaluate the different color in its feet regarding its legs and torso and its cause. A portable equipment that combined X-ray diffraction (XRD) and X-ray fluorescence (XRF) was employed to analyze chemical composition and mineralogical characterization of pigments. This equipment allowed obtaining simultaneously XRF and XRD at the same point without sampling. X-ray techniques identified cerussite, hydrocerussite and barite in different layers. The presence of zinc oxide from a recent restoration was also detected. Additionally, laser induced fluorescence (LIF) was employed to assess the presence of different fluorescent compounds on the surface. This technique showed the use of acrylic products in the feet, loincloth and torso of Christ from previous restoration and allowed to detect spectral difference on the feet and a high ration of the acrylic product on feet, both could be the cause of the differential degradation between the feet and torso. This multi-approach study based on portable and non-destructive techniques allowed restoration monitoring and helped restorers to take decisions without sampling.

Le bore a été utilisé essentiellement à partir de la fin du xviiie siècle dans la formulation des verres et glaçures. Toutefois, sa présence en très faibles quantités dans certaines glaçures post-Renaissance, donc dès le xviie siècle, nous a incités à évoquer l’histoire de cet élément dans les matériaux vitreux. Nous tenterons de comprendre l’origine du bore dans ces glaçures et discuterons son impact sur les questions de datation et d’authentification des productions post-palisséennes.

The Alcazar Palace (Seville, Spain) is famous for its ceramic decorations; 16 th century wall tiles of different typologies have been analyzed in order to relate the manufacturing process of their colored glazes to the evolving technologies of the Renaissance. Chemical and mineralogical compositions have been determined in situ by non-destructive X-ray fluorescence (XRF) and X-ray diffraction (XRD) on arista ceramics in the Cenador de Carlos Quinto, and majolica ceramics in the Palacio Gotico and the Royal oratory. The arista style belongs to the local Hispano-Moresque ceramic tradition. Majolica tiles have the complex microstructures of glazes from Italy. The two types are clearly differentiated by their typology, morphology (curved vs flat surface), and also microstructure (single vs multilayers), glaze chemistry, and use of different coloring agents. Moreover, we found different glaze chemistries in the investigated majolicas, which correspond to different artists and/or practices.

Au début des années 2000, l'impulsion de contrats européens a entraîné le C2RMF dans la conception et la construction d'un appareil portable de fluorescence et diffraction des rayons X (FRX-DRX). Les choix techniques concernant la source et les détecteurs ont conduit à un appareil robuste, qui a été utilisé dans de nombreux pays d'Europe, à la source d'une trentaine de publications dans des revues scientifiques.

In the Hall of the Kings, along the east side of the Courtyard of Lions in the Alhambra (Granada), the vaulted ceilings are clad in painted leather depicting various Kings or Lords on their seats, the fountain of youth, and a Lady playing chess. These artworks are unique masterpieces because of the unusual medium used (leather) and the presence of human representation in 14th century Muslim art.The colour palette of the paints used was assessed without taking samples, using a prototype apparatus that simultaneously performs X-ray diffraction (XRD) and X-ray fluorescence (XRF), providing an elemental chemical and mineralogical characterization of the areas studied. The curvature of the vaulted ceiling and the size of device restricted analysis to the flattest parts and the most accessible areas.The results show that the red hues are made from cinnabar and/or hematite. The flesh colour is a mixture of cinnabar and hydrocerussite, while malachite was used for the greens. Blues were achieved using lazurite and azurite, and the ochre tones using clays. Furthermore, XRD detected the presence of red lead in the red-ochre and orange tones, while gold is present together with tin and iron. Moreover, strontium is associated with the plaster preparation, and a compound made with arsenic and sulphur was observed in the green areas. (C) 2015 Elsevier B.V. All rights reserved.

The synthesis and detailed characterization of gold nanoparticles (AuNPs) inside human hair has been achieved by treatment of hair with HAuCl4 in alkaline medium. The AuNPs, which show a strong red fluorescence under blue light, are generated inside the fiber and are arranged in the cortex in a remarkably regular pattern of whorls based on concentric circles, like a fingerprint. It opens an area of genuine nanocomposites with novel properties due to AuNPs inside the hair shaft.

La Grotte de Rouffignac (Dordogne, France) est un site d'art paléolithique qui renferme de nombreux dessins réalisés au trait noir (mammouths, bisons, rhinocéros laineux, chevaux, bouquetins...). Bien qu'aucune datation directe n'ait été réalisée à ce jour, les œuvres graphiques de cette caverne sont en général rattachées au Magdalénien.

Cet article est consacré à l’analyse des pigments employés par Rembrandt sur l’Autoportrait au chevalet et Les Pèlerins d’Emmaüs. Les méthodes employées ont été majoritairement non invasives : fluorescence et diffraction de rayons X. Elles ont été complétées par l’étude de deux petits prélèvements qui ont permis de préciser la stratigraphie des couches préparatoires. On a ainsi pu noter que les pigments employés sur Les Pèlerins d’Emmaüs sont assez habituels chez Rembrandt, alors qu’ils sont beaucoup plus restreints en nombre sur l’Autoportrait au chevalet, et correspondent aux pigments représentés sur la palette.

In cultural heritage science, compositional data is traditionally obtained from works of art through the analysis of samples by means of various bench-top instruments (scanning electron microscope, Raman spectrometer, etc.). Alternatively, the object can be transported to a laboratory where it may be examined, usually by spectroscopic methods working in reflection mode. However, this paper describes how a complementary set of mobile and portable instruments was deployed in situ to gain a comprehensive view on the materials and related ageing compounds of an (almost) unmovable 15th-C polyptych, prior to and in preparation of the extraction of a limited number of samples. In line with the methodological approach discussed, PXRF was first employed as an efficient screening tool. The ensuing elemental data was supplemented by more specific information on both organic as inorganic materials supplied by reflection near- and mid-FTIR spectroscopy and fluorimetry. In completion, a limited number of diffraction patterns were collected with a mobile XRD instrument in order to identify the constituent crystalline phases in pigments, grounding materials and degradation products. In this way, it could be demonstrated how a rich array of colours was obtained by means of a limited palette of pigments: lead white, lead tin yellow, azurite, natural ultramarine, bone black, vermillion, madder lake, and a green copper-organo complex were detected and situated on the panels. Remarkably, next to chalk also gypsum was found in the ground layer(s) of this Western European easel painting. The relatively large surface of the background was covered with gold leaf; the analyses seem to point towards the labour-intensive water gilding technique. The versatility of this combination of analytical techniques was further illustrated by the accurate characterisation of degradation products affecting the readability and conservation of the painting: the overall presence of a calcium oxalate-based film of variable thickness was established. Nevertheless, further analysis of cross-sectioned samples was considered desirable in order to study the stratigraphy, to gain direct access to altered and sub-imposed layers and to allow highly detailed analysis of micrometric degradation products by state-of-the art techniques (i.e. synchrotron radiation).

A portable X-ray fluorescence/X-ray diffraction (XRF/XRD) system for artwork studies has been designed constructed and tested. It is based on Debye Scherrer XRD in reflection that takes advantage of many recent improvements in the handling of X-rays (polycapillary optics; advanced two-dimensional detection). The apparatus is based on a copper anode air cooled X-ray source, and the XRD analysis is performed on a 5-20 μm thick layer from the object surface. Energy dispersive XRF elemental analysis can be performed at the same point as XRD, giving elemental compositions that support the interpretation of XRD diagrams. XRF and XRD analyses were tested to explore the quality and the limits of the analytical technique. The XRD diagrams are comparable in quality with diagrams obtained with conventional laboratory equipment. The mineral identification of materials in artwork is routinely performed with the portable XRF-XRD system. Examples are given for ceramic glazes containing crystals and for paintings where the determination of pigments is still a challenge for nondestructive analysis. For instance, lead compounds that provide a variety of color pigments can be easily identified as well as a pigment such as lapis lazuli that is difficult to identify by XRF alone. More than 70 works of art have been studied in situ in museums, monuments, etc. In addition to ceramics and paintings, these works include bronzes, manuscripts, etc., which permit improvement in the comprehension of ancient artistic techniques.

A bicrystal slightly deviated from the rhombohedral twin orientation is deformed by creep so as to activate two basal slip systems in each grain. The tilt deviation in the starting bicrystal is accommodated by two parallel arrays of disconnections with the smallest twin Burgers vectors and large associated steps. Dislocations from both grains interact with the grain boundary (GB) and the tilt deviation increases by 3.6°, giving rise to an array of pure edge disconnections with no associated steps. Interfacial defects are interpreted by reactions between incoming dislocations and GB disconnections. Decompositions of dislocations into GB disconnections are followed by glide and climb of products that can annihilate or interact to give a perfect wall of edge disconnections superimposed to the twin boundary perfect structure. Owing to their large Burgers vectors, the final disconnections are always dissociated.

It is rare that the analyses of materials in paintings can be carried out by taking micro-samples. Valuable works of art are best studied in situ by non-invasive techniques. For that purpose, a portable X-ray diffraction and fluorescence apparatus has been designed and constructed at the C2RMF. This apparatus has been used for paintings of Rembrandt, Leonardo da Vinci, Van Gogh, Mantegna, etc. Results are given to illustrate the performance of X-ray diffraction, especially when X-ray fluorescence does not bring sufficient information to conclude.