LARGE STRUCTURES: WHICH SOLUTIONS FOR HEALTH MONITORING?

Whatever the age of a large structure (dam, viaduct, cooling tower, nuclear containment, tunnel, …) It has to be periodically monitored. It is a challenge to realise these services when the access is limited and difficult for Man. This paper introduces a global approach, developed by SITES, through examples of application on different concrete dams or cooling towers, and their results. This global method involves three techniques: the SCANSITES® (a visual inspection system), the LIDAR (3D laser scanning) and high resolution photogrammetry

Size-driven relaxation and polar states in PbMg1/3Nb2/303-based system

Nanocrystalline powders and ceramics with controlled grain size from 15 to 3000 nm of PbMg1∕3Nb2∕3O3(PMN) and (PMN)0.65−(PbTiO3)0.35(PMN−PT35) have been synthesized using the ball milling method. Dielectric experiments have revealed in PMN a disappearance of relaxation below ≈30nm grain size and combined x-ray and Raman experiments the vanishing of correlations between polar nanoregions (PNRs). A similar study in morphotropic compound PMN-PT35 has shown the appearance of a relaxor state below ≈200nm, associated to a destruction of the ferroelectric domains state towards PNRs in a paraelectric matrix. These phenomena are discussed in connection with pressure experiments from the literature and on the basis of polar states destabilization by both elastic and electric random fields changes associated with the size reduction

Polar and chemical order in relation with morphotropic phase boundaries and relaxor behaviour in bulk and nanostructured PSN-PT

We have recently evidenced the existence of a complex path of polarisation rotation via two monoclinic phases in the giant-piezoelectric materials PSN PT that is similar to the PMN-PT system. In this article we have presented the state of knowledge on the PSN-PT system and have given new results showing the close connection between the local inhomogeneous chemical order of Sc/Nb/Ti cations and the stability of different ferroelectric phases. The notion of morphotropic phase boundaries is discussed in relation with the gradual appearance of long-range polar order with increasing Ti content in PSN-PT. Comparison with the films and nanopowders/ceramics has also been made

Size effects on the macroscopic properties of the relaxor ferroelectric Pb(Mg1/3Nb2/3)O3-PbTiO3 solid solution

International audience[No abstract available

Low-Temperature Transport Properties of Bi-Substituted b-As2Te3 Compounds

International audienceβ-As2Te3 belongs to the family of Bi2Te3-based alloys, a well-known class of efficient thermoelectric materials around room temperature. As2Te3 exists in two allotropic configurations: α- and β-As2Te3, of which only the latter crystallizes in the same rhombohedral structure as Bi2Te3. Herein, we report on substitution of Bi for As in the As2−x Bi x Te3 system with x = 0.0, 0.015, 0.025, and 0.035. These samples have been characterized by x-ray diffraction and scanning electron microscopy. The transport properties have been measured at low temperatures (5 K to 300 K) in both directions, parallel and perpendicular to the pressing direction. The results are compared with those obtained in previous study on samples substituted by Sn. Compared with Sn, Bi allows for a clear decrease in electrical resistivity while maintaining the thermal conductivity below 1 W/(m K) over the whole temperature range. As a result, a comparable peak ZT value near 0.2 was obtained at room temperature

Scalable and Formable Tellurite-Based Transparent Ceramics for Near Infrared Applications

International audienceInnovative transparent tellurite polycrystalline ceramics are demonstrated to be simply elaborated by full and congruent crystallization of the 75TeO2–12.5Bi2O3–12.5Nb2O5 parent glass. The low temperature tellurite glass elaboration and its stability both enable the preparation of scalable tailor-shaped ceramics with high refractive index, transmission in the near infrared range up to 5.5 μm, and promising mechanical/thermal properties

Thermoelectric Properties of the alpha-As2Te3 Crystalline Phase

International audienceAs2Te3 exists in two crystallographic configurations: alpha- and beta-As2Te3, of which only the latter crystallizes in the same rhombohedral structure-type as Bi2Te3. While beta-As2Te3 shows interesting thermoelectric (TE) properties which can be adjusted through alloying, the transport properties of the monoclinic phase alpha-As2Te3, more thermodynamically stable than the beta-phase at room temperature, has not yet been studied thoroughly. We report here on the samples preparation by powder metallurgy, and on the microstructural characterization of polycrystalline alpha-As2Te3. Preliminary results on the electrical and thermal properties measured between 5 K and 523 K are also reported. Transport properties measurements were performed both along and perpendicular to the pressing direction indicating that the transport properties demonstrate some degree of anisotropy. Remarkably, low thermal conductivity values (below 1 W m-1 K-1 above 300 K) were measured suggesting that this compound may be an interesting platform to design novel TE materials with high efficiency