Nano-compression of carbon micro-balloons on a xp-nanoindenter

Microballoons are thin hollow spheres that are bonded together with resins to form 'syntactic foam'. These foams exhibit very high specific compressive strength. Mechanical properties of the microballoons are integral to the mechanical properties of the syntactic foams and will also be useful in modeling of the system. This paper will present nano-compression results obtained for individual carbon microballoons (CMBs) tested between 5 and 50 mN on a XP nano-indentation device (MTS) customized with a special cylindrical tip. Details of the procedure will also be presented. CMBs ranging in diameter from 5 to 80 pm were randomly chosen for testing, which allowed for a statistical analysis (140 tests). Less than 25% of the CMBs were found to be nearly perfect spheres (from comparison between the 'horizontal' diameter measured with a microscope and the 'vertical' compressed diameter). CMBs smaller than 10 pm and greater than 50 pm were markedly ellipsoidal and about one third of the CMBs exhibited 'sequential' cracking, revealing the existence of flaws. SEM and optical microscopy of the foams revealed these flaws as either voids in the wall thickness or compartments in some CMBs. Conventional Berkovich nano-indentation was performed on segments of CMB walls after nanocompresseion and yielded a value of approximately 31 GPa for Young's modulus. The measured thickness was between 0.3 and 2.2 pm, showing no correlation with the diameter of the pristine CMBs

Ethics and social responsibility in practice: interpreters and translators engaging with and beyond the professions

Interpreting and translation are unregulated activities in most countries, yet interpreters and translators perform challenging work in sensitive domains, such as the law, medicine and social work. Other professionals working in these sectors must complete formal ethics training to qualify, then subscribe to Codes of Practice or Ethics. When they face ethical challenges in their work, they can access ongoing support. They must undertake regular refresher training in ethics. Interpreters and translators rarely have access to this sort of ethical infrastructure. This places the onus on interpreters and translators to reflect on ethical aspects of their practice, for reasons related to both professional performance and social responsibility. This contribution presents original UK-based research with one type of professional ‘clients’ who rely on interpreters and translators, social workers and social work students prior to their first work experience placement. Findings suggest that insufficient attention has been paid to such professional clients and that ethical aspects of professional communication can be compromised as a result. By framing ethics training and ongoing support in terms of social responsibility, we point to some ways in which the different professional groups might communicate and work more effectively with one another and with service users

Secondary crystalline phases identification in Cu2ZnSnSe4 thin films: contributions from Raman scattering and photoluminescence

In this work, we present the Raman peak positions of the quaternary pure selenide compound Cu2ZnSnSe4 (CZTSe) and related secondary phases that were grown and studied under the same conditions. A vast discussion about the position of the X-ray diffraction (XRD) reflections of these compounds is presented. It is known that by using XRD only, CZTSe can be identified but nothing can be said about the presence of some secondary phases. Thin films of CZTSe, Cu2SnSe3, ZnSe, SnSe, SnSe2, MoSe2 and a-Se were grown, which allowed their investigation by Raman spectroscopy (RS). Here we present all the Raman spectra of these phases and discuss the similarities with the spectra of CZTSe. The effective analysis depth for the common back-scattering geometry commonly used in RS measurements, as well as the laser penetration depth for photoluminescence (PL) were estimated for different wavelength values. The observed asymmetric PL band on a CZTSe film is compatible with the presence of CZTSe single-phase and is discussed in the scope of the fluctuating potentials’ model. The estimated bandgap energy is close to the values obtained from absorption measurements. In general, the phase identification of CZTSe benefits from the contributions of RS and PL along with the XRD discussion.info:eu-repo/semantics/publishedVersio

Diffraction techniques and vibrational spectroscopy opportunities to characterise bones

From a histological point of view, bones that allow body mobility and protection of internal organs consist not only of different organic and inorganic tissues but include vascular and nervous elements as well. Moreover, due to its ability to host different ions and cations, its mineral part represents an important reservoir, playing a key role in the metabolic activity of the organism. From a structural point of view, bones can be considered as a composite material displaying a hierarchical structure at different scales. At the nanometre scale, an organic part, i.e. collagen fibrils and an inorganic part, i.e. calcium phosphate nanocrystals are intimately mixed to assure particular mechanical properties

Spectroscopic ellipsometry and polarimetry for materials and systems analysis at the nanometer scale: state-of-the-art, potential, and perspectives

This paper discusses the fundamentals, applications, potential, limitations, and future perspectives of polarized light reflection techniques for the characterization of materials and related systems and devices at the nanoscale. These techniques include spectroscopic ellipsometry, polarimetry, and reflectance anisotropy. We give an overview of the various ellipsometry strategies for the measurement and analysis of nanometric films, metal nanoparticles and nanowires, semiconductor nanocrystals, and submicron periodic structures. We show that ellipsometry is capable of more than the determination of thickness and optical properties, and it can be exploited to gain information about process control, geometry factors, anisotropy, defects, and quantum confinement effects of nanostructures

De l'analyse micro/nanostructurale et micromécanique à l'imagerie des fibres de renfort d'un composite à matrice métallique

L'amélioration des propriétés thermomécaniques des alliages de titane par incorporation de fibres céramiques rend possible leur utilisation dans certaines pièces tournantes chaudes. Les fibres de renfort étant elles-mêmes des matériaux composites, une évolution de leur état métastable peut conduire à une dégradation des propriétés thermomécaniques. Or, l'état physico-chimique et mécanique de ces fibres est fonction de l'histoire thermique mais aussi des réactions qui se produisent à l'interface fibre-matrice ou au sein même des fibres, sous l'effet des gradients thermiques et chimiques imposés par l'élaboration, puis par l'utilisation du composite. La microspectrométrie Raman est la seule méthode applicable aux matériaux composites qui permette une analyse conjointe des états micro/nanostructural et mécanique (tension, compression) de fibres amorphes ou nanocristallines. Le travail présenté analyse les modifications physico-chimiques et micromécaniques induites par les matrices Ti 6242 sur des fibres SCS-6 (Textron) dans des composites préparés soit par forgeage de feuilles entre lesquelles des fibres sont prises en sandwich, soit par frittage des mêmes fibres revêtues, par CVD, d'une gaine de matrice

Synthesis of chiral 4-alkyl 4-hydroxy cyclopentenones via a diastereoselective tandem aza-Cope/Mannich cyclization reaction from aldehydosugar

A convenient construction of chiral 4-hydroxy 2-cyclopentenones from α-alkoxy aldehyde 6 derived from sugar is reported. A mechanism is proposed involving imine-enamine equilibrium, then alkylation with 2-alkoxypropenyl iodide followed by a tandem 3-aza-Cope/intramolecular Mannich reaction in a one-pot process. © 1995

In situ Raman microscopy study of ceramic fibres in ceramic matrix composites

Communication to : 4th international conference on composites engineering - ICCE/4, Big Island, Hawaii (USA), July 6-11, 1997SIGLEAvailable from INIST (FR), Document Supply Service, under shelf-number : 22419, issue : a.1997 n.217 / INIST-CNRS - Institut de l'Information Scientifique et TechniqueFRFranc

Effective elastic properties and residual stresses in directionally solidified eutectic Al2O3/YAG/ZrO2 ceramics estimated by finite element analysis

International audienceEffective elastic properties and residual stresses were assessed in directionally solidified ternary eutectic ceramic, Al2O3/YAG/ZrO2, by finite element analyses. A 3D finite element model was generated from a CT scan, representative of the microstructure and with a similar volume fraction. Effective elastic properties were calculated by numerical homogenisation. They highlight a quasi-isotropic behaviour of the ternary eutectic ceramics. Despite the difficulties to measure the strain, the dispersion observed in the results and the limited reliability of the materials properties, the results constitute a step towards a better understanding of the material behaviour. Thermal residual stresses induced by the manufacturing were also evaluated. Tensile residual stresses in yttria-stabilised zirconia and compressive residual stresses in YAG and alumina were highlighted. This evaluation also shed light on the influence of the phase morphology in the microstructure. Indeed, the computed spatial distribution of the residual stresses showed that they are different from one position to another due to the variation in phase morphology and also to material properties variability. Therefore, it is important when numerically assessing the thermomechanical properties to take into account the microstructure morphology as well as the variability of material properties