E. Dooryhee

Making make-up in Ancient Egypt

The extensive use of green, white and black make-up has been known since the earliest periods of Egyptian history,. We have investigated cosmetic powders dating from between 2000 and 1200 BC that were preserved in their original containers. Quantitative crystallographic and chemical analysis of the organic and mineral components of the powders enabled us to identify two natural lead-based compounds: crushed ore of galena (PbS) and cerussite (PbCO3). We also found two unexpected constituents: laurionite (PbOHCl) and phosgenite (Pb2Cl2CO3). Because they are neither natural extracted ores nor products resulting from subsequent ageing or chemical modification, laurionite and phosgenite appear to be synthetic products manufactured by the Egyptians using ‘wet’ chemistry.

SYNTHESIS AND ACID RESISTANCE OF MAYA BLUE PIGMENT

Maya blue is an organo-clay artificial pigment composed of indigo and palygorskite. It was invented and frequently used in Mesoamerica in ancient times (eighth to 16th centuries). We analyse in this paper one of the characteristics of Maya blue that has attracted the attention of scientists since its rediscovery in 1931: its high stability against chemical aggression (acids, alkalis, solvents, etc.) and biodegradation, which has permitted the survival of many works of art for centuries in hostile environments, such as the tropical forest. We have reproduced the different methods proposed to produce a synthetic pigment with the characteristics of the ancient Maya blue. The stability of the pigments produced using either palygorskite or sepiolite has been analysed by performing acid attacks of different intensities. The results are analysed in terms of pigment decolouration and destruction of the clay lattice, revealed by X-ray diffraction. Palygorskite pigments are much more resistant than sepiolite pigments. It is shown that indigo does not protect the clay lattice against acid aggression. We show that Maya blue is an extremely resistant pigment, but it can be destroyed using very intense acid treatment under reflux.

Nanometric size effects on irradiation of tin oxide powder

A nanometric powder of tin oxide (SnO2) has been irradiated with lead ions. The same grains have been observed by Transmission Electron Microscopy (TEM) before and after irradiation at a fluence of 5×1012 Pb cm−2. The shape of largest grains strongly changes while the smallest ones disappear. This phenomenon has been explained by using the thermal spike model. It appears that the irradiation induces an increase of the internal pressure in the grains leading to their explosion. In the smallest grains, the calculated maximal temperatures exceed the boiling point so that these grains disappear.

Structural and electrical damage induced by high‐energy heavy ions in SiO2/Si structures

The structural and electrical properties of SiO2/Si structures irradiated by high‐energy (≳0.5 GeV) Xe and Ni ions have been investigated. Structural analysis of the irradiated SiO2 films, performed with infrared spectroscopy, points to atomic displacements and broken and strained Si—O bonds induced by the irradiation. Using ir data, the damage cross section of the Xe and Ni ions has been deduced. The values are of about 8×10−13 and 6×10−14 cm2 for, respectively, 762 MeV Xe and 551 MeV Ni ions. Electrical measurements of irradiated SiO2/Si structures show an increase of the interface‐state density Dit and of the oxide trapped‐charge density N0t with the ion fluence. These results are compared with defects induced by heavy‐ion irradiation in bulk silica and by light particle radiation in silicon dioxide. Electrically active point defects have been detected in irradiated silicon and are associated with vacancy complexes.  The structural and electrical properties of SiO2/Si structures irradiated by high‐energy (≳0.5 GeV) Xe and Ni ions have been investigated. Structural analysis of the irradiated SiO2 films, performed with infrared spectroscopy, points to atomic displacements and broken and strained Si—O bonds induced by the irradiation. Using ir data, the damage cross section of the Xe and Ni ions has been deduced. The values are of about 8×10−13 and 6×10−14 cm2 for, respectively, 762 MeV Xe and 551 MeV Ni ions. Electrical measurements of irradiated SiO2/Si structures show an increase of the interface‐state density Dit and of the oxide trapped‐charge density N0t with the ion fluence. These results are compared with defects induced by heavy‐ion irradiation in bulk silica and by light particle radiation in silicon dioxide. Electrically active point defects have been detected in irradiated silicon and are associated with vacancy complexes.

Phase transformation of polycrystalline Y2O3 under irradiation with swift heavy ions

Abstract The effects of swift heavy ions in bulk solid targets have been extensively studied. Some effects are specifically related with the large densities of energy absorbed by the target electron gas in the projectile wake. One remarkable effect observed in the present work is the crystalline solid state phase transition of Y 2 O 3 as a result of ionizing irradiation by GeV heavy ions. Our X-ray diffraction measurements give the first evidence of the cubic to monoclinic transformation of Y 2 O 3 under high energy heavy ion irradiation.

Observations by X-ray diffraction of structural changes in mica irradiated by swift heavy ions

Abstract The descriptions of high-energy ion irradiation damage in mica by small-angle X-ray/neutron scattering and electron microscopy are used to support some models of track formation in dielectric solids. More recently heavy ion tracks in mica could be observed by atomic force microscopy and the dependence of the track radius on the particle energy loss is in contradiction with previous results. This discrepancy as well as the structural modifications (i.e. amorphization, dilatation, distortions) of ion-irradiated mica are discussed using the technique of wide-angle X-ray diffraction.

Effect of tensile and compressive strains on the transport properties of SmNiO3 layers epitaxially grown on (001) SrTiO3 and LaAlO3 substrates

This paper deals with the role of epitaxial strain on the structure and electronic transport properties of metastable SmNiO3 layers grown by metal-organic chemical vapor deposition onto SrTiO3 and LaAlO3 substrates. The characterization of these layers is carried out by high resolution x-ray diffraction and four-probe resistivity measurements. It is found that the SmNiO3 phase is stabilized by in-plane compressive strain whereas in-plane tensile strain induces the creation of oxygen vacancies that induces an annihilation of the metal-insulator transition and a huge increase of the resistivity.

The effect of the octahedral cations on the dimensions of the palygorskite cell

Abstract High-resolution synchrotron X-ray diffraction recorded on a collection of palygorskites with different chemical compositions (obtained by analytical electron microscopy) permits unambiguous correlation of the crystallographic parameters a (or a sin β if a monoclinic phase is considered) with the nature of the octahedral sheet, i.e. with both the number of octahedral positions that are occupied and the type of octahedral cation. No significant changes in the lattice parameters b and c are observed. The unit cell modification consists essentially of an expansion in a as the number of cations with larger ionic radii (Mg2+ and Fe3+) predominates over smaller cations (Al3+). A linear dependency of a (or a sin β) on the chemical composition of the octahedral sheet was obtained that can be used for classifying palygorskite into compositional groups, using only conventional diffraction data, without the need for chemical analyses.

Formation of Si nanocrystals by heavy ion irradiation of amorphous SiO films

Abstract We studied the structural transformations of a-SiO thin films caused by swift heavy ion irradiation at room temperature. Rutherford backscattering spectroscopy, nuclear reaction analysis, transmission electron microscopy and infrared absorption spectrometry have been used in combination to investigate the changes induced by ion irradiation. We show that the homogeneous monoxide is transformed according to the macroscopic reaction: 2SiO → Si + SiO 2 . Each ion perturbs a large area (approximately 10–30 nm diameter). 2–3 nm diameter Si clusters are formed inside the track core. A broad photoluminescence at ∼ 600 nm is also detected in the irradiated films. This visible light emission is associated with the formation of the perturbed zone.

TEM study of irradiation effects on tin oxide nanopowder

Abstract The effects of swift heavy ions in bulk materials have now long been studied and some models — such as the thermal spike — have been developed in order to explain the observed phenomena. Nevertheless, some questions remain debatable, among which the following ones: i) What is the spatial extension of the huge energy deposited by the swift heavy ions on the target electrons? ii) Can we evidence a pressure effect in some materials due to the lattice temperature increase? In most cases, we are able to predict whether a bulk material may be sensitive or not to the electronic energy loss S e of the incident ion. According to the thermal spike, a given material could be all the more sensitive to S e as the energy density deposited on the electrons is high. Therefore, an interesting way to increase this energy density is to confine the electrons in small target grains (i.e. submicrometric grains). This work reports the first experimental results obtained on irradiated tin oxide (SnO 2 ) nanopowders. The same grains have been observed by TEM and HREM before and after lead ion irradiation at several fluences (from 0.3 to 7.5 × 10 12 Pb cm −2 ). A modification gradually appears as the fluence increases up to a critical fluence above which the grains split into nanodomains. A possible explanation is given through the thermal properties of SnO 2 .