Mesurer nécessite d'évaluer les incertitudes de mesure. Une mesure scientifique n'a de sens qu'accompagnée de son incertitude, ce qui permet de fixer le nombre de chiffres significatifs de sa valeur numérique. Ceci permet par exemple de vérifier la conformité d'une série de pièces usinées à un cahier des charges qualité.Les méthodes de calcul des incertitudes-types conformes aux recommandations internationales sont présentées progressivement, après avoir distingué les erreurs des incertitudes.Des vidéos d'expérience, accompagnées de cours et de nombreux exercices, devraient vous permettre d'exprimer correctement vos résultats de mesure, quelle que soit la grandeur mesurée et les appareils utilisés.https://socles3.unisciel.fr/course/view.php?id=555

Monodispersed hollow periodic mesoporous organosilica nanoparticles (HPMO-NPs) with a controlled core cavity and a periodic mesoporous organosilica (PMO) shell are successfully synthesized using a dual templating approach. The PMO shell synthesized by the sol–gel route exhibits a hybrid organic-inorganic framework based on phenylene bridges. The HPMO spherical nanoparticles with a diameter above 500 nm were characterized using a multiscale approach through TEM, BET, SAXS, and FT-IR. They are shown to offer an open periodic mesoporosity, a hollow cavity with a size tailored by thediameter of the core template, and finally, a high surface area (833 m 2 · g−1 ). In addition, we demonstrate that, through the same approach, the size of these hollow spherical nanoparticles can be tuned. Indeed, sub-50-nm hollow nanoparticles with mesoporous shells have also been obtained. The differences observed in the textural properties of these two sizes of hollow mesoporous nano-objects are discussed.

The synthesis of multifunctional poly(amidoamine)(PAMAM)-based dendrimers containing a cleavable disulfide linkerwithin each armof the dendrimer, together with condensable triethoxysilyl groups on the periphery of the dendrimer, isdescribed. The dendrimers were mixed with bis(triethoxysilyl)benzene and subsequently transformed into silsesquioxanegels or periodic mesoporous organosilicas (PMOs) to generate materials with dendrimers covalently embedded within theinterior of the silsesquioxane networks. Subsequent treatment of the gels with dithiothreitol enabled the core of thedendrimers to be selectively cleaved at the disulfidesite, thus generating thiol functions localised within the pores.The effect of different dendrimer generations on the reactivity of the pendant thiol functions was probed by impregnationwith gold salts, which were reduced to obtain gold nanoparticleswithin the pore networks of the gels and PMOs. The gelsyielded polydisperse gold nanoparticles (2 to 70 nm) with dimensions modulated by the generation of thedendrimer,together with well-defined gold/thiolate clusters with Au...S distances of 2.3 Å. Suchclusters were also observed in the PMOsystem, together with monodispersed gold nanoparticles with diameters comparable to that of the organised pores in thePMO. The role of surface functionalisation in controlling the formation of gold clusters and/or nanoparticles is discusse

Downsizing electronic and electric equipment requires the optimization of electric field distributions in order to avoid localized dielectric breakdown (also called partial discharges). This paper presents a novel dielectric composite material aimed at grading electrical local surface stress. This functional material has a conductivity which increases by several orders with the applied electric field giving the ability to distribute the field by itself. It is prepared for the first time by dispersing graphite nanoplatelets in a polymer and may be used as a resistive or capacitive field grading material in electronic and electrical applications. Mechanisms at the origin of the nonlinear behavior are discussed.

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The variety of H bond (HB) interactions is a source of inspiration for bottom-up molecular engineering through self-aggregation. Non-conventional intermolecular HBs between N,N0disubstituted urea and thiourea are studied in detail by vibrational spectroscopies and ab initio calculations. Raman and IR mode assignments are given. We show that it is possible to study selectively the different intermolecular bifurcated intra-and inter-dimer HBs with the two types of HB acceptors. Through the ab initio calculation, the thioamide I mode, a specific marker of N-H … S=C HB interactions, is unambiguously identified.

The Raman modes of α-quartz-type boron phosphate were found to be extremely stable in frequency over a large temperature range from 300–1000 K. In order to determine the origin of this behavior, the material was also studied at high pressure up to 6 GPa. Upon compression, a classical behavior was observed with mode Grüneisen parameters ranging from −0.08(2) to 3.0(1). The present results indicate that the high temperature behavior in this material is an example of an unusual compensation effect between phonon–phonon interactions and implicit contributions due to thermal expansion. Phonon stability is of utmost importance for materials properties that are dependent on it such as dielectric and piezoelectric properties, for example. Boron phosphate belongs to the important class of α-quartz-type piezoelectric materials for which temperature stability is of primordial importance for resonator and sensor applications.