Rémy Chapoulie

Laser-induced breakdown spectroscopy for elemental characterization of calcitic alterations on cave walls

Cave walls are affected by different kinds of alterations involving preservative issues in the case of ornate caves, in particular regarding the rock art covering the walls. In this context, coralloids correspond to a facies with popcorn-like aspect belonging to the speleothem family, mostly composed of calcium carbonate. The elemental characterization indicates the presence of elements that might be linked to the diagenesis and the expansion of the alterations as demonstrated by prior analyses on stalagmites. In this study, we report the use of laser-induced breakdown spectroscopy (LIBS) to characterize the elemental composition of one coralloid sample with a portable instrument allowing punctual measurements and a laboratory mapping setup delivering elemental images with spatial resolution at the micrometric scale, being particularly attentive to Mg, Sr, and Si identified as elements of interest. The complementarity of both instruments allows the determination of the internal structure of the coralloid. Although a validation based on a reference technique is necessary, LIBS data reveal that the external layer of the coralloid is composed of laminations correlated to variations of the LIBS signal of Si. In addition, an interstitial layer showing high LIBS signals for Fe, Al, and Si is interpreted to be a detrital clay interface between the external and the internal part of the coralloid. These preliminary results sustain a possible formation scenario of the coralloid by migration of the elements from the bedrock.

Characterization of unswept and swept quartz crystals for space applications

Unswept and vacuum-swept synthetic quartz crystals were investigated in order to determine the mechanisms responsible for the radiation sensitivity of this material. Results were obtained by means of infrared (IR) spectroscopy, dielectric relaxation spectroscopy (DRS), and thermoluminescence (TL). First, the effect of vacuum sweeping was clearly demonstrated in IR absorption by a significant decrease in the amount of hydroxyl ions and in DRS by the disappearance of the dielectric loss peak arising from the relaxation of alkali ions. Second, it was shown that swept quartz is less sensitive to irradiation than the unswept crystal. A sharp decrease in the TL sensitivity of the electrolyzed material was observed in the energy range corresponding to the recombination of alkaline-electronic defects. DRS results indicated that the dielectric signal is shifted toward a lower energy range for both types of crystals, suggesting that the irradiation greatly facilitates the relaxation of alkaline species by creating ...

Identification of the UV induced defects in Sr3Gd2Si6O18: Pb, Mn using thermostimulated luminescence (TL) and electron spin resonance (ESR)

Thermostimulated luminescence (TL) has been used to detect UV-induced defects in the green emitting phosphor Sr3Gd2Si6O18: Pb, Mn (SGS: Pb, Mn). Two defects have been revealed in the temperature range of 20 °C to 500 °C following a 185 nm irradiation, with respective activation energies of 0.97 ± 0.05 eV and 1.28 ± 0.06 eV. Identification has been partially achieved thanks to their TL emission spectra and with the aid of ESR measurements. One of the defects may imply an oxygen vacancy in association with an interstitial oxygen (i.e. a self-trapped exciton). The second one would involve the dopant lead linked to an oxygen ion in an interstitial position. Thus the luminescence process of SGS: Pb, Mn would be affected because of the absorption levels of these defects which coincide with the emission levels of the ions Pb2+ and Gd3+ and with the 254 nm mercury emission line. This methodological approach in characterizing defects can be extended to other silicate phosphors.

Detection by thermoluminescence of damages created by α desintegrations in radionuclear waste glass

Abstract Study of thermo-stimulated luminescence of an α irradiated natural glass has revealed the formation of a structural defect that cannot be annealed thermally and is therefore cumulative. This phenomenon was again encountered and analysed in synthetic borosilicate glass to be used as radionuclear waste glass. To detect this structural modification, the thermoluminescence signal of an α irradiated sample is traced under certain conditions. Two peak characteristics of a previous α irradiation appear at 230 °C and 320 °C. Their intensity increases at each new experiment, although the α irradiation dose administered remains constant. In other words, despite the successive thermal emptyings, the glass keeps the trace of previous irradiations and consequently gives an increasing signal for constant doses.

Towards High Resolution Ceramic Series for Production Site Studies: The Case of Loron Amphorae (Croatia, 1st?3rd C. A.D.)

BackgroundFrom the 1st to the 3rd centuries A.D., the territory of Istria (present-day Croatia) was a prominent area of olive oil production. Archaeologists have identified the so-called Dressel 6B amphora as the main container used in the transport and trade of this oil. So far archaeology and epigraphy have helped identify probable sources of production and two workshops in Istria, and have also allowed the reconstruction of main trade routes through the identification of stamped amphorae. However, much less is known about the organization of the production of these ceramic containers, which may have been conducted on an almost industrial scale. This preliminary study demonstrates how chemical analysis using energy-dispersive X-ray fluorescence spectrometry (EDXRF) may address this question and provide new answers and avenues of inquiry.ResultsOur study of 53 amphorae, produced during two important periods in the history of the workshop of Loron, has evidenced that even in chronologically closely related contexts of production chemical analysis could significantly separate samples according to production groups.ConclusionsThis result constitutes a very important first step towards a thorough study of the entire production history of the workshop, involving the creation of a comprehensive geochemical reference group comprising several hundred samples. This in turn will enable us to address an array of hypotheses concerning the economy and ecology of this production site, which are briefly presented in the article. The application of this methodology to the whole corpus of Istrian amphorae is then advocated in light of this study.

Evolução das cores RGB : uma ferramenta digital para monitorar mudanças visuais em pigmentos irradiados por pulsos de laser infravermelho.

Oxidos de ferro (goethita e hematita) pulverizados foram irradiados com pulsos laser objetivando verificar o resultado da interacao desses pos com a radiacao infravermelha concentrada em pulsos de curta duracao e altamente energeticos. Esses experimentos se justificam diante da utilizacao desses pos, em obras de arte, como pigmentos, desde as epocas mais remotas. Na atualidade, tornou-se frequente recorrer a pulsos laser como ferramenta de limpeza de obras de arte, o que justifica a necessidade do desenvolvimento de conhecimentos relacionados a interacao laser-pigmentos. Evitar danos as obras de arte, recentes ou nao, e uma exigencia inevitavel. Os resultados mostraram que os pulsos laser Nd:YAG fornecem energia suficiente para promover, instantaneamente, mudancas quimicas e estruturais nos pigmentos minerais estudados. Material vitrificado (amorfo) foi identificado nas amostras irradiadas e sua formacao deveu-se a solidificacao ultra-rapida ocorrida no locais onde a energia disponibilizada pelos pulsos laser foi suficiente para fundir as particulas do po. Em consequencia das mudancas quimicas e estruturais induzidas, houve alteracao da cor original do material irradiado. Essas alteracoes cromaticas foram quantificadas por intermedio de um metodo desenvolvido para tal finalidade e que e baseado na variacao da intensidade das componentes RGB das cores digitais.

Probing some organic ukiyo-e Japanese pigments and mixtures using non-invasive and mobile infrared spectroscopies

Non-invasive identification of organic colourants in paintings still remains a challenging issue, especially in the case of extremely thin layers of paint on printed paper such as Japanese ukiyo-e prints. Because prints are fragile artworks, various non-invasive analytical methods need to be employed. The present work focuses on results obtained by combining fibre optic reflectance spectroscopy in the near-infrared range (FORS NIR) with mid-infrared (MIR) spectroscopy. The first step consists of identifying spectroscopic marker bands typical of some organic pigments (indigo, gamboge, cochineal, turmeric, safflower, dragon’s blood). Some reference printouts involving paper substrate, binder and pigments (seldom used or as mixtures) were then investigated in order to establish a straightforward way to extract the marker bands of the pigments. Some data post-treatments were applied to the spectra, such as spectral subtraction, in order to abstract the signal from overlapping bands originating from both substrate and binder, and second derivative calculation to emphasise the pigment marker bands’ frequency positions. These data treatments turned out to be relevant to extract information on the organic pigments of interest, even within complex mixtures.

Art and cultural heritage—where analytical sciences contribute to preserve our heritage

EuroAnalysis 2015, the XVIII Scientific Meeting of the Euroanalysis series, was held at the Congress Center, Bordeaux, France, from September 6 to 10, 2015. A session devoted to the topic of cultural heritage studies was organized at the occasion of this international meeting. The intense and fruitful exchanges between the conference attendees engaged during the tenue of the session Bart and cultural heritage^ clearly showed the concern in common that analytical scientists address to the problem of our cultural heritage preservation. If each case addressed by the question of artwork preservation can be specific to a material engaged in the observed degradation processes, the variety of expertise and techniques proposed to preserve artworks demonstrated that the scientific community feels in charge of bringing solutions for our cultural heritage protection. For this special issue of ESPR, entitled BArt and cultural heritage—where analytical sciences contribute to preserve our heritage^, contributions were solicited from those participants, who had made an oral or poster presentation at the Euroanalysis 2015. This compilation of application studies is addressed to the broader scientific community interested in cultural heritage issues. We formulate the wish that the publication of this issue will give raise to an increased interest among the heritage scientist community for application of their works to ESPR. In this special issue, two published articles refer directly to the fundamental question of corrosion processes to which metal artefacts are unavoidably faced. As a matter of fact, the presence of oxygen and water in the environment, the climatic conditions, the temperature, and the precipitation are responsible for the advent of moisture and oxidation processes initiating the formation of corrosion products with, in fine, deleterious effects in term of conservation. In this aspect, controlling the corrosion of ferrous metal objects presents a real challenge to conservators as exposed byWatkinson and Emmerson in their evaluation on the impact of aqueous washing on the ability of akaganéite (β-FeOOH) to corrode iron. Indeed, the versatility of use of iron alloys makes iron one of the most reactive and unstable species for heritage ironworks in many environments. Particularly, chloride reveals as a major accelerator for iron artefact corrosion when present and its presence may favour the occurrence of β-FeOOH, known as an effective corrosion products for iron archaeological objects. Thus, it is of outmost interest to determine how the washing of β-FeOOH can affect its ability to corrode iron under relatively high humidity conditions for the development of adapted methods in conservation practice when chloride andβ-FeOOH interact in the corrosion process. Similarly, the corrosion of outdoor bronze monuments is depending on the presence of oxygen and water to favour the formation of copper corrosion layers. The induced protection of these corrosion layers of different composition in correlation with the environmental conditions (e.g. through the formation of copper chlorides, copper sulphates) is controversial in their effectiveness. However, so far, conservation and restoration treatments used for copper-based alloys are mostly based on the application of protective organic coatings. Responsible editor: Philippe Garrigues

Characterization of pre-Columbian artefacts in situ through handheld portable X-ray fluorescence spectrometry: the case of ceramics from the Mochica site of San José de Moro (Peru)

The famous archaeological site of San José de Moro (SJM) located in the Jequetepeque Valley (JV) represents one of the best-preserved pre-Columbian Mochica cemeteries uncovered along the north coast of Peru. SJM was a regional ritual centre where elites and the general population of all JV met to celebrate ceremonial events. Its role as a place of regional integration and coordination continued long after the disappearance of the Mochica and SJM was continuously occupied throughout the Late Mochica Period (8th–9th c. AD) and into the Transitional Period (9th–10th c. AD). Even though the abandonment of Mochica traditions in SJM (funerary practices and ceramic styles) appears quite rapid, SJM was constantly occupied whereby local traditions were being reshaped. During this time various styles of ritual ceramics from different traditions (Mochica, Cajamarca and Wari) were buried within ceremonial and funerary contexts. This research involves archaeometric studies of excavated painted diagnostic ceramic sherds representing four distinctive pre-Columbian typologies present at this site—Mochica fineline bichrome, Mochica fineline polychrome, coastal Cajamarca and Highland Cajamarca ceramics. For this study handheld portable X-ray fluorescence spectrometer (HHpXRF) instrumentation was operated in situ in order to (1) perform non-destructive trace element analysis (2) to assess if Cajamarca ceramics were further elaborated using the same raw materials employed by the Mochica potters of SJM, and (3) to establish whether or not Mochica and Cajamarca ceramics were truly technological markers in the lower part of the Jequetepeque valley.ResultsThe chemical elements detected in the ceramic bodies by the portable technique and used for this analysis were: K, Ca, Mn, Fe, Zn, Ga, As, Rb, Sr and Y. All sherds that were identified as aesthetically different also differed chemically with the exception of the Mochica fineline bichrome and the Mochica fineline polychrome, which were produced in a coastal workshop using the same local raw materials. In addition, these sherds were not elaborated employing the same recipe used in the Coastal and Highland Cajamarca productions.ConclusionsMochica ceramic productions are stylistically and chemically different from both Coastal and Highland Cajamarca productions. Ceramics from San José de Moro are technological markers of two cultures (Mochica and Cajamarca) in the lower part of the Jequetepeque Valley that interacted during Late Mochica and through the Transitional periods.

Silicate Glasses In Nuclear Harsh Environment: Application Of Thermostimulated Luminescence To Radiation Damage Study

It is well known that when a silica optical fiber is irradiated by neutrons or heavy ions, there is an attenuation of the transmission of the signal which is due to the creation of specific radiation damage. We have been able to show the creation of alpha radiation damage in borosilicate glass and glass used for radioactive waste confining in studying their properties of thermostimulated luminescence after high alpha irradiation. We have been able to correlate these radiation damages with interatomic bond break which implies oxygen. To extend this research to all silica optical fiber, the thermostimulated luminescence mechanisms of vitreous silica have been analysed. To exalt its properties in thermostimulated luminescence it has been doped with aluminium. Then, the creation of alpha radiation damage has been searched in this vitreous silica doped with aluminium. The next step of the study is an extending of this method to detect the effect of neutronic or heavy ions irradiation on vitreous silica samples which constitutes the basic material of optical fiber used in nuclear harsh environment.