Elaboration, by tape casting, of an SOFC half cell for low temperature applications

International audienceThese last past years, a major interest has been devoted to decrease the working temperature of solid oxide fuel cells (SOFCs) down to about 700°C. In this respect, materials with a high ionic conductivity at low temperature have to be found and the rpocess to elaborate fuel cells, using these new materials, has to be developed .....

A new subunit vaccine based on nucleoprotein nanoparticles confers partial clinical and virological protection in calves against bovine respiratory syncytial virus

Human and bovine respiratory syncytial viruses (HRSV and BRSV) are two closely related, worldwide prevalent viruses that are the leading cause of severe airway disease in children and calves, respectively. Efficacy of commercial bovine vaccines needs improvement and no human vaccine is licensed yet. We reported that nasal vaccination with the HRSV nucleoprotein produced as recombinant ringshaped nanoparticles (NSRS) protects mice against a viral challenge with HRSV. The aim of this work was to evaluate this new vaccine that uses a conserved viral antigen, in calves, natural hosts for BRSV. Calves, free of colostral or natural anti-BRSV antibodies, were vaccinated with NSRS either intramuscularly, or both intramuscularly and intranasally using MontanideTM ISA71 and IMS4132 as adjuvants and challenged with BRSV. All vaccinated calves developed anti-N antibodies in blood and nasal secretions and N-specific cellular immunity in local lymph nodes. Clinical monitoring post-challenge demonstrated moderate respiratory pathology with local lung tissue consolidations for the non vaccinated calves that were significantly reduced in the vaccinated calves. Vaccinated calves had lower viral loads than the nonvaccinated control calves. Thus NSRS vaccination in calves provided cross-protective immunity against BRSV infection without adverse inflammatory reaction

Processing of functional fine scale ceramic structures by ink-jet printing

International audienceThis review illustrates the potentiality of ink-jet printing for the fabrication of functional fine scale ceramic structures corresponding to two different kinds of micro-pillar arrays i.e. (i) PZT skeletons, etc..

Stick Slip Motion in Grain Grain Friction in a Humid Atmosphere

International audienceWe set up an original apparatus to measure the grain grain friction stress inside a granular medium composed of sodo-silicate-glass beads surrounded by a water vapor atmosphere. We analyze here the influence of the physico chemistry of water on our glass beads and its consequences on our shear experiment. We found two scales in the analysis of the shear stress signal. On the microscopic scale of one bead, the experimental results show a dependence on the size of beads, on the shear rate and on humidity for the resulting stick slip signal. On the macroscopic scale of the whole assembly of beads, the behavior of the total amplitude of the shear stress depends on the size of the beads and is humidity dependent only for relative humidity larger than 80%. For high degrees of humidity, on the microscopic scale, water lubricates the surface of the beads leading to a decrease in the microscopic resistance to shear while on the macroscopic scale the resistance to shear is increased: the assembly of very humid grains behaves as a rheothickening flui

Textural evolution of polyhedral olivine experiency rapid cooling rates

International audienceDynamic crystallization experiments in the CaO-MgO-Al2O3-SiO2 (CMAS) system have been used to investigate the change in crystal shape when pre-existing polyhedral olivine crystals are cooled rapidly (1,639-2,182 degrees C/h). Polyhedral olivines are crystallized initially in a first step using a slow cooling rate (2 degrees C/h), then skeletal and dendritic overgrowths develop on the polyhedral crystals during a subsequent fast cooling event. During this second episode small dendritic olivines also nucleate within the liquid phase. Observation of the experimental sample by optical microscopy shows that the polyhedral olivine shape progressively changes to a skeletal and then to a dendritic morphology in the following sequence: polyhedral double right arrow hopper polyhedral double right arrow dendritic polyhedral. This evolutional sequence is discussed in terms of changes in the crystal growth conditions during cooling and a general relation between these olivine dynamic crystallization experiments and the integrated model of crystal growth by Sunagawa (Bull Miner 104:81-87, 1981, Morphology of crystals, Terra Scientific Publishing Company, 1987) is proposed

Two dimensional versus three dimensional post deposition grain growth in epitaxial oxide thin films influence of the substrate surface roughness

Epitaxial thin films made of nanosized yttria-stabilized zirconia islands deposited on (0001) sapphire substrates are synthesized by sol–gel dip-coating followed by a high-temperature post-deposition thermal annealing procedure. At high temperatures, a competitive growth process takes place that allows to obtain thin films made of atomically flat islands with an in-plane diameter typically ten times higher than the thickness or on the contrary inducing the formation of dome-shaped islands. Apart from having a different shape, these islands are also characterized by a different crystallographic orientation with respect to the substrates respectively (001) and (111). In this paper, we investigate the influence of the substrate surface roughness on this competitive grain growth process. The deposition on epi-polished substrates results in a two-dimensional (2D) island growth, whereas the deposition on rough substrates results in a three-dimensional (3D) growth of dome-shaped nanosized islands. The films have been characterized by atomic force microscopy and high-resolution X-ray diffraction using the reciprocal space mapping techniqu

Sintering kinetics and oxide ion conduction in Sr-doped apatite-type lanthanum silicates, La9Sr1Si6O26.5

International audienceThese last past years, a major interest has been devoted to decrease the working temperature of solid oxide fuel cells (SOFCs) down to about 700 °C. Apatite materials (La10−xSrxSi6O27−x/2) are attractive candidates for solid electrolytes, with a high ionic conductivity at these intermediate temperatures. An apatite powder (x=1) with a 0.75 μm mean particle size, produced by solid state reaction, was tape cast to obtain green sheets with a thickness of about 260 μm. On one hand, the densification mechanism of the apatite ceramic during the intermediate solid state sintering has been approached. It appeared from the kinetical tests performed under isothermal conditions between 1250 and 1550 °C, that densification could be controlled by the diffusion at grain boundaries of the rare-earth element, La, with an activation energy of 470 kJ/mol. On the other hand, conductivity measurements were performed on apatite samples sintered at 1400 and 1500 °C. The ionic conductivity was mainly sensitive to the presence of secondary phases at 1400 °C. The ionic conductivity of the apatite sintered at 1500 °C (mean grain size=3.9 μm) is equal to 1.2×10−2S/cm at 700 °C