This work presents a new synthesis of nano-sized lithium niobate particles by a low temperature three steps procedure. The complete protocol implies a LiH induced reduction of NbCl5 followed by in situ spontaneous oxidation into low valence niobium nano-oxides. These niobium oxides are exposed to air atmosphere leading to pure Nb2O5 formation. Finally, the stable Nb2O5 is converted into lithium niobate LiNbO3 nanoparticles during the controlled hydrolysis of the LiH excess. The nano-sized lithium niobate particles as well as their formation processes were characterized using X-ray photoelectron spectroscopy.

OATAO is an open access repository that collects the work of some Toulouse researchers and makes it freely available over the web where possible.

OATAO is an open access repository that collects the work of Toulouse researchers and makes it freely available over the web where possible. This is an author-deposited version published in : http://oatao.univ-toulouse.fr/ Eprints ID : 9567To link to this book section :

This is an author's version published in: http://oatao.univ-toulouse.fr/23772 ARTICLE INFO ABSTRACTKeywords: Three•polnt bendlng test Cross-eut test Adheslon mechanJsms Atmospherlc pressure plasma PEEKmatrlxOur study focuses on the use of a remote atmospheric pressure plasma process for the improvement of polymer surface reactivity. Indeed, surface activation of carbon-fiber-reinforced pol ym ers that use a poly etheretherketone matrix is required to achieve strong and long-term adhesion of paint on the composite. Emphasis 111,ill be placed on the contribution of gas plasma used on surface modification. We use two techniques to characterize adherence improvement: a qualitative and industrial approach with a cross-eut test and a quantitative approach with a three-point bending test. However, to provide a better understanding of the plasma-induced modifications ttsing air or nitrogen gas, diagnostics of the surface are also necessary. The wettability improvement, chemical surface modifications, and topography are analyzed by using contact angle measurement, X-ray photoelectron spectroscopy, and atomic force microscopy, respectively. The combination of these diagnostics highlights the capability of plasma treatrnent to tune the plasma/surface interactions de pending on gas plasma, which results in improved adhesion. E-mail address: nicolas.naude@laplace.univ-tlse.fr ( N . Naudé). https://doi.org/10.1016/j.surfcoat.2019.01.102 2.6. Interface characterization by three-point bending test 2. 6.1. Relevance of the test Among the wide variety of mechanical tests, three-point bending test according to ISO 14679:1997 [19] presents some advantages in the context of this study. The good repeatability of the results, as a result of the tensile machine, coupled with the numerous types of exploitable information that can be obtained, ma.kes this test useful for a better

Epoxy resins are ubiquitously encountered in industrial applications as in adhesives and composites. The properties of epoxy-amine networlcs are directly impacted by the presence of metal (bydr-oxidized) surfaces, leading to a modificati on of their glass transition temperature T 8 • We propose here an innovative experimental approach, investigating the interaction of DET A amine and DGEBA epoxy with Al and Cu powder substrates (partially (hydr)oxidized). We explored for the first tiine the formation of the amine-metal interphase by in situ mixing calorimetry to evaluate the energetics of interaction. While DGEBA interacted only sl ightly with Al-based surface, the reaction with OETA was associated with a high exothermic enthalpy of reaction. The enhancing role of surfaoe hydroxylation was also evidenced by comparing boehmited Al to a simply oxidired counterpart. An even larger exothermic effect was measured with copper, which was related to the high chelating power of Cu compared to Al. The possible underlying mechanism of amine-metal interphase formation was discussed with a generalized schematic.

International audiencePiezoelectric films were prepared by incorporation of lithium niobate (LiNbO3) nanoparticles into copolymer of vinylidene difluoride and trifluoroethylene. Nanoparticles of LiNbO3 with ferroelectric phase were successfully synthesized and dispersed homogenously by ultrasonication in the copolymer matrix without any surfactant or surface functionalization. The nanocomposites were fully characterized by electronic microscopy, X-ray diffraction, differential scanning calorimetry, dynamical mechanical analysis, and piezometer. Surprisingly, the copolymer matrix crystallinity and morphology were not affected by the incorporation of nanoparticles. Therefore the nanocomposites remained good mechanicals properties and high ferroelectricity coupled to nonlinear optical activity thanks to the noncentro symmetric space group of lithium niobate. This could be a novel approach to develop new multifunctional materials

No abstract

OATAO is an open access repository that collects the work of Toulouse researchers and makes it freely available over the web where possible. This is an author-deposited version published in : http://oatao.univ-toulouse.fr/ Eprints ID : 17849 A B S T R A C TThe increasing use of adhesives in industry has boosted the search for tests which allow the adherence level to be defined. These tests, depending on the type of load, examine different stresses, failure modes and mixed modes. Furthermore, these tests can be focused either on initiation or propagation of adhesive failure. The subject of this study is the initiation of adhesive failure. The initiation of failure can be determined with the 3-point bending test. Trials of 3-point bending tests were conducted on an aluminum 2024 substrate, with two different thicknesses, in order to understand the impact of the adherend thickness. The aluminum substrate received different types of surface pre-treatment: acetone cleaning, hydrochloric acid etching or aminopropyltriethoxysilane coating. Two adhesives were used: the first one was a mixture of epoxy pre-polymer DGEBA and DETA amine, whereas the second was a commercially formulated adhesive, ELECOLIT 6604. The initiation of adhesive failure was obtained by 3-point bending test and verified with SEM analysis. The failure loads measured enabled the effect of surface treatment on adhesive failure to be revealed: the results indicate that the surface treatment with silane is the most efficient in comparison to hydrochloric acid etching and of course to the simple acetone degreasing. It was assumed that the scatter of the results obtained for each series is due to the variation of the "intrinsic" adherence between the adhesive and the substrate. Furthermore, it was noted that the failure loads for different substrate thicknesses cannot be compared due to the effect of the thickness: it was therefore not possible to simply compare results obtained for different thicknesses of the same substrate for a given substrateadhesive system. The energy approach proposed in this study makes it possible. The energy requested to initiate the adhesive failure for a given system can then be known, whatever the initial geometry of the 3-point bending test is. However, it was also shown that the thickness of the substrate must be correctly chosen. A thick substrate increases the dispersion and a thin substrate may induce local unwelcome plastic strain. In conclusion, this study allows to define an energy criteria for adhesives failure initiation.