Thermal Expansion of (Ba1-xLax))Ti1-x/4 O 3 Solid Solutions

Deformation and the thermal expansion coefficient of ceramic samples of (Ba1−xLax)Ti1−x /4 O 3 solid solutions (x= 0, 0.026, 0.036, 0.054) were studied in the temperature range 120–700 K. Based on an analysis of the data obtained, the temperature–composition phase diagram is refined, and the temperature dependence of the polarization is calculated. The results are discussed in combination with the dielectric measurement data

Full-Field Transmission X-ray Microspectroscopy (FF-XANES) Applied to Cultural Heritage Materials: The Case of Ancient Ceramics

Synchrotrons provide more and more significant analytical techniques to investigate ancient materials from cultural heritages. New ways to visualize the complex structure of these materials are developed on the basis of elemental, density, and refraction contrasts. The tunability of synchrotron beams owing to the high flux and high spectral resolution of photon sources is at the origin of the main chemical speciation capabilities of synchrotron-based techniques. Among them the full-field X-ray absorption near-edge structure (XANES) imaging technique using hard X-rays is particularly efficient. It allows investigating a significant volume of material with a very good spatial resolution, which is invaluable for ancient material because of their heterogeneity and complexity. After presenting the technique and its variants, we will show its ability to study cultural heritage materials through a few examples

TEM characterization of the fine scale microstructure of a Roman ferrous nail

This paper describes the microstructure of a Roman ferrous nail through its observation by transmission electron microscopy. The morphologies of pearlitic colonies and ferritic grains are detailed and the relationship between pearlitic colonies and ferrite in Roman nails is explicitly demonstrated for the first time. Observations also confirm the presence of dislocations in ferritic grains and attest to the existence of very small carbide precipitates that have not been pointed out previously in standard archaeometric studies

Reverse engineering the ancient ceramic technology based on X-ray fluorescence spectromicroscopy

We present results of X-ray fluorescence (XRF) microprobe analyses of ancient ceramic cross-sections aiming at deciphering the different firing protocols used for their production. Micro-focused XRF elemental mapping, Fe chemical mapping and Fe K-edge X-ray absorption near edge structure spectroscopy were performed on pre-sigillata ceramics from southern Gaul, and terra Sigillata vessels from Italy and southern Gaul. Pieces from the different workshops and regions showed significant difference in the starting clay material, clay conditioning and kiln firing condition. By contrast, sherds from the same workshop exhibited more subtle differences and possible misfirings. Understanding the precise firing conditions and protocols would allow recreation of kilns for various productions. Furthermore, evolution and modification of kiln design would shed some light on how ancient potters devised solutions to diverse technological problems they encountered

Les glaçures de céramiques chinoises colorées au fer : un matériau historique à fort potentiel en science de la matière ?

Les potiers chinois ont été des plus imaginatifs dans l’utilisation du fer comme élément colorant de glaçures. Ils ont su en tirer une riche palette de couleurs en jouant non seulement sur son degré d’oxydation (Fe3+, Fe2+), mais également sur sa spéciation. Dans cet article, nous présenterons les apports des dernières études archéométriques et nous montrerons que la découverte d’une forme rare d’oxyde ferrique (ε-Fe2O3) dans glaçures ouvre d’intéressantes perspectives non seulement en histoire des techniques, mais également en science des matériaux.Chinese potters were highly imaginative in their use of iron as a colouring for glazes. Playing not only on its level of oxidation (Fe3+, Fe2+), but also on its chemical speciation, they succeeded in producing a rich palette of colours. In this paper we shall present the latest archeometric research findings and show that the discovery of a rare form of ferric oxide (ε-Fe2O3) in these glazes opens up interesting perspectives in both the history of techniques and materials science

Thenature of marbled Terra Sigillata slips: a combined mu XRF and mu XRD investigation

In addition to the red terra sigillata production, the largest Gallic workshop (La Graufesenque) made a special type of terra sigillata, called 'marbled' by the archaeologists. Produced exclusively on this site, this pottery is characterized by a surface finish made of a mixture of yellow and red slips. Because the two slips are intimately mixed, it is difficult to obtain the precise composition of one of the two constituents without contamination by the other. In order to obtain very precise correlation at the appropriate scale between the color aspect and the element and mineralogical phase distributions in the slip, combined electron microprobe, x-ray micro spectroscopies and micro diffraction on cross sectional samples were performed. The aim is to discover how potters were able to produce this unique type of terra sigillata and especially this slip showing an intense yellow color. Results show that the yellow component of marbled sigillata was made from a titanium-rich clay preparation. The color is related to the formation of a pseudobrookite (TiFe2O5) phase in the yellow part of the slip, the main characteristics of that structure being considered nowadays as essential for the fabrication of stable yellow ceramic pigments. Its physical properties such as high refractive indices and a melting point higher than that of most silicates widely used as ceramic colorants are indeed determinant for this kind of applications. Finally, the red parts have a similar composition (elementary and mineralogical) to the one of standard red slip

Thermal expansion, polarization and phase diagrams of Ba1−yBi2y/3Ti1−xZrxO3 and Ba1−yLayTi1−y/4O3 compounds

The thermal expansion properties of the ceramic compositions Ba1−yLayTi1−y/4O3 (y = 0.0, 0.026, 0.036, 0.054) and Ba1−yBi2y/3Ti1−xZrxO3 (y = 0.10; x = 0.0, 0.04, 0.05, 0.10, 0.15) were determined in the temperature range 120–700 K. We report the temperature-dependent measurements of the strain, thermal expansion coefficient and the magnitude of root mean square polarization. The results obtained are discussed together with the data on the structure and dielectric properties

Precipitation in original Duralumin A-U4G versus modern 2017A alloy

Precipitation in Duralumin, a historic quaternary alloy of the type: Al–Cu–Mg–Si, was never fully studied nor observed by current electron microscopy techniques. This article presents the full characterization and comparison of two alloys: a Duralumin (A-U4G) from the 1950s collected on a vintage aircraft and its modern equivalent: a 2017A alloy. The as-received and peak-aging states were analysed with DSC, SAXS and TEM advanced techniques. It is shown that old Duralumin and modern 2017A present a similar nanoprecipitation in the as-received state and behave similarly upon artificial aging. As opposed to what has been reported in the past, three types of precipitates participating in hardening were found upon aging: θ’-Al2Cu, Q’(Q)-AlCuMgSi and Ω-Al2Cu

Transmission Electron Microscopy Emerging Investigations for Cultural Heritage Materials

cited By 1International audienceTransmission electron microscopy (TEM), with its various imaging modes and analytical abilities, is now an indispensable tool for chemical and structural characterization at the nanoscale of all types of materials. Cultural heritage materials do not differ fundamentally from other materials except that they are more heterogeneous, with a more complex and imperfect structure. In addition, many of them contain nanoparticles or have a nanoscale structuration, which plays a significant role in their physical properties or is rich in information concerning their manufacture. TEM techniques are thus well suited to investigate them, especially because the developments of these last decades afford both a more efficient sample preparation and faster data recording