Synthesis of ZnO nanoparticles by flame spray pyrolysis and characterisation protocol

There is uncertainty concerning the potential toxicity of zinc oxide (ZnO) nanoparticles, which may be attributed in part to a lack of understanding with regard to the physiochemical properties of the nanoparticles used in toxicological investigations. This paper reports the synthesis of a ZnO nanopowder by flame spray pyrolysis and demonstrates that the typically employed characterisation techniques such as specific surface area measurement and X-ray diffraction provide insufficient information on the sample, especially if it is intended for use in toxicity studies. Instead, a more elaborate characterisation protocol is proposed that includes particle morphology as well as detailed compositional analysis of the nanoparticle surface. Detailed transmission electron microscopy analysis illustrated the polydispersity within the sample: particles were elongated in the c-crystallographic direction, with average Ferret length ∼23 nm and Ferret width ∼14 nm. Dynamic light scattering (0.1 w/v% in deionised water, pH 7.4) revealed the particles were agglomerated with a modal secondary particle size of ∼1.5 μm. Fourier transform infrared spectroscopy and X-ray photoelectron spectroscopy indicated the presence of carbonate and hydroxide impurities on the surface of the ZnO nanoparticles and an increase of such impurities was observed as the sample was aged, which might influence the nanoparticle dissolution and/or cellular uptake behaviour. These data will be utilised, in order to facilitate the interpretation and understanding of results from toxicological investigations using in vitro cell lines

Tuning the sapphire EFG process to the growth of Al 2 O 3 /YAG/ZrO 2 :Y eutectic

International audienc

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

On the growth and structure of Al2O3-Y3Al5O12-ZrO2:Y solidified eutectic

International audienc

Formation of locked-lamellar grains in a slightly hypoeutectic Al-Al2Cu alloy during thin-sample directional solidification

We studied the formation and growth of locked-lamellar microstructures in a thin sample of a slightly hypoeutectic Al-Al2Cu alloy. The coupled-growth dynamics, including early stages and steady-state regimes, was observed optically in real time during directional solidification. The orientation of the a (Al) and q (Al2Cu) crystals was measured ex situ in a series of eutectic grains by X-ray Laue microdiffraction. A nucleation event of a q crystal on a pre-existing a crystal, and the subsequent growth of a eutectic grain with a type-C orientation relationship, that is, with a coincidence of {123}-a and {100}-q planes, were observed in situ. In type-C eutectic grains, lamellar locking occurred parallel to the low-energy coincidence plane. A regular (floating) coupled-growth dynamics was observed in misoriented eutectic grains

Investigation of liquid oxide interactions with refractory substrates via sessile drop method

International audienceThe wetting of refractory substrates by oxide alloys has been investigated using a high-temperature sessile drop bench. The aim of this study was to select the best crucible material for directional solidification processes such as the Bridgman, edge-defined film-fed growth or micro-pulling down methods. Contact angles and surface tension were determined via high-resolution imaging. The O2 partial pressure in the furnace atmosphere was also measured. Alumina and a eutectic ceramic called A/YAG/Z (Al2O3/Y3Al5O12/ZrO2) were studied by investigating the following systems: alumina/molybdenum, alumina/tungsten and alumina/iridium; A/YAG/Z–molybdenum, A/YAG/Z–tungsten and A/YAG/Z–iridium. The results show intermediate wetting for both oxides (30° < θ <50°). This is an original result for A/YAG/Z. Several previous studies reported good wetting (7° < θ <20°) for alumina. Accurate surface tension values could not be obtained by image processing. Therefore, the Wilhelmy method was used, giving γ = 0.63 ± 0.03 N m−1 for alumina, which is comparable to the value of 0.67 ± 0.03 N m−1 reported in the literature. The surface tension obtained for A/YAG/Z was 0.71 N m−1, but this value was influenced by the approximate density used. A metal-like layer was observed on the apex of the drops after solidification. According to an SEM–EDS analysis, most of these layers were composed of molybdenum, tungsten and oxygen. Based on thermodynamic calculations, a mechanism which takes into account the oxidation of Mo parts and the dissolution of oxides in the drop is proposed

Formation of locked-lamellar grains in a slightly hypoeutectic Al-Al2Cu alloy during thin-sample directional solidification

We studied the formation and growth of locked-lamellar microstructures in a thin sample of a slightly hypoeutectic Al-Al2Cu alloy. The coupled-growth dynamics, including early stages and steady-state regimes, was observed optically in real time during directional solidification. The orientation of the a (Al) and q (Al2Cu) crystals was measured ex situ in a series of eutectic grains by X-ray Laue microdiffraction. A nucleation event of a q crystal on a pre-existing a crystal, and the subsequent growth of a eutectic grain with a type-C orientation relationship, that is, with a coincidence of {123}-a and {100}-q planes, were observed in situ. In type-C eutectic grains, lamellar locking occurred parallel to the low-energy coincidence plane. A regular (floating) coupled-growth dynamics was observed in misoriented eutectic grains

Formation of locked-lamellar grains in a slightly hypoeutectic Al-Al2Cu alloy during thin-sample directional solidification

We studied the formation and growth of locked-lamellar microstructures in a thin sample of a slightly hypoeutectic Al-Al2Cu alloy. The coupled-growth dynamics, including early stages and steady-state regimes, was observed optically in real time during directional solidification. The orientation of the a (Al) and q (Al2Cu) crystals was measured ex situ in a series of eutectic grains by X-ray Laue microdiffraction. A nucleation event of a q crystal on a pre-existing a crystal, and the subsequent growth of a eutectic grain with a type-C orientation relationship, that is, with a coincidence of {123}-a and {100}-q planes, were observed in situ. In type-C eutectic grains, lamellar locking occurred parallel to the low-energy coincidence plane. A regular (floating) coupled-growth dynamics was observed in misoriented eutectic grains

Leadless pacing using the transcatheter pacing system (Micra TPS) in the real world: initial Swiss experience from the Romandie region.

Leadless pacemakers are implanted in Switzerland since June 2015. Large worldwide registries have shown high implant success, low complication rates, and good electrical parameters up to 12 months' follow-up. However, data are scarce outside the investigational setting. The purpose of this study is to assess the real-world experience regarding clinical safety and efficacy of Micra TPS (transcatheter pacing system) leadless pacemakers. Retrospective observational, multi-centre study designed to assess initial safety and efficacy of the Micra TPS in the Swiss Romande region. A total of 92 patients were included from four different centres with an implantation success rate of 97.8% (90 of 92). Thresholds were overall low at implantation (median 0.38 V/0.24 ms, ranging from 0.13 to 2.88 V/0.24 ms) and remained stable over 1-year follow-up. The perioperative serious adverse event rate was 6.5% in six patients which lead to prolonged hospitalization in five patients and death in one patient. In addition, three further major events (3.3%) occurred during an average follow-up of 1 year, requiring implantation of a standard transvenous pacemaker in two patients, and surgical explantation of the Micra TPS in one patient due to intractable ventricular tachycardia. Leadless pacemakers are a valuable adjunct for treating selected patients requiring single-chamber pacing. However, in this initial experience, major complication rates were high (9.8%). The implant procedure requires proper training and should be performed in an adequate setting

Tissu adipeux épicardique et fibrillation auriculaire [Epicardial adipose tissue and atrial fibrillation]

Atrial fibrillation (AF) is the most common arrhythmia encountered in adults; it is associated with a significant morbidity and mortality. Obesity is a risk factor contributing to AF occurrence. Recently, interest has focused on epicardial adipose tissue (EAT), defined as a fatty deposit located between the epicardium and the visceral pericardium. Its characteristics are distinct from classic adipose deposits: it infiltrates the epicardial myocardium and secretes cytokines, which modulate cardiomyocyte electrophysiology and cardiac remodeling. Different studies show that EAT can be an independent risk factor for AF and that EAT thickness, as measured by CT or MRI, could predict the presence, severity and recurrence of AF