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International audience; Wetting of polymer-grafted nanoparticles (NPs) in a polymer nanocomposite (PNC) film is driven by a difference in surface energy between components as well as bulk thermodynamics, namely, the value of the interaction parameter, χ. The interplay between these contributions is investigated in a PNC containing 25 wt % polymethyl methacrylate (PMMA)-grafted silica NPs (PMMA-NPs) in poly(styrene-ran-acrylonitrile) (SAN) upon annealing above the lower critical solution temperature (LCST, 160 °C). Atomic force microscopy (AFM) studies show that the areal density of particles increases rapidly and then approaches 80% of that expected for random close-packed hard spheres. A slightly greater areal density is observed at 190 °C compared to 170 °C. The PMMA-NPs are also shown to prevent dewetting of PNC films under conditions where the analogous polymer blend is unstable. Transmission electron microscopy (TEM) imaging shows that PMMANPs symmetrically wet both interfaces and form columns that span the free surface and substrate interface. Using grazingincidence Rutherford backscattering spectrometry (GI-RBS), the PMMA-NP surface excess (Z*) initially increases rapidly with time and then approaches a constant value at longer times. Consistent with the areal density, Z* is slightly greater at deeper quench depths, which is attributed to the more unfavorable interactions between the PMMA brush and SAN segments. The Z* values at early times are used to determine the PMMA-NP diffusion coefficients, which are significantly larger than theoretical predictions. These studies provide insights into the interplay between wetting and phase separation in PNCs and can be utilized in nanotechnology applications where surface-dependent properties, such as wettability, durability, and friction, are important.

Predictive and quantitative understanding of ion and mass transport in liquid and polymeric electrolytes is at the heart of electrochemistry. Here, the goal is to accurately simulate the performance of an electrochemical cell, for which the temperature- and concentration-dependent transport coefficients of a given electrolyte, as well as the thermodynamic mean salt molal activity coefficient, must be known. These are the conductivity, σ, the salt diffusion coefficient, D, and the cation transference number, t+. The transport coefficients must hence be extracted with high accuracy from experimental measurements. The transference number is defined as the ratio of current carried by the cation to the total electric current. Its importance with regards to energy density and power density was recognized in the early 1990s by Doyle, Fuller and Newman (1). Nevertheless, researchers still argue about transference number values, even in baseline systems such as lithium bistrifluoromethanesulfonimidate (LiTFSI) in Poly(ethylene oxide) (PEO) (2). The transference number can be measured via the steady-state Bruce-Vincent polarization method (3, 4), the Balsara-Newman method (5), as well as pulsed field gradients NMR (pfg-NMR) (6) and pulsed field gradients electrophoretic NMR (e-NMR) (2). Despite extensive efforts towards unified results of these approaches, in particular as a function of ion concentration, a clear picture has not yet emerged. Towards this end, we developed an alternative approach towards determining the ion transport properties. Specifically, we directly and operando measured precise microscopic and macroscopic physical properties of the electrolyte upon cell polarization in a Li/electrolyte/Li cell, combined this with calculations via concentrated solution theory continuum modelling (CM), and rationalized our findings with microscopic insight from molecular dynamics (MD) simulations. We utilized a well-studied benchmark model system electrolyte consisting of PEO and LiTFSI at Li+ to EO molar ratio of r = 0.1. Under constant voltage polarization, we directly measured the velocity associated with electrolyte and ions via heterodyne synchrotron X-ray photon correlation spectroscopy (XPCS), and the TFSI- concentration gradient from electrode to electrode via X-ray absorption microscopy (XAM). The significance of our results lies in the unification of microscopic and macroscopic predictions from simulation with experimental measurements as well as the self-consistent determination of a concentration-independent transference numbers of approximately 0.2. Our study paves the way for further length- and time-scale bridging understanding of ion transport. 1. M. Doyle, T. F. Fuller, J. Newman, The Importance of the Lithium Ion Transference Number in Lithium Polymer Cells. Electrochimica Acta 39, 2073-2081 (1994). 2. M. P. Rosenwinkel, M. Schönhoff, Lithium Transference Numbers in PEO/LiTFSA Electrolytes Determined by Electrophoretic NMR. Journal of The Electrochemical Society 166, A1977-A1983 (2019). 3. J. Evans, C. A. Vincent, P. G. Bruce, Electrochemical Measurement of Transference Numbers in Polymer Electrolytes. Polymer 28, 2324-2328 (1987). 4. P. G. BRUCE, C. A. VINCENT, STEADY STATE CURRENT FLOW IN SOLID BINARY ELECTROLYTE CELLS. J. Electroanal. Chem. 225, 1-17 (1987). 5. D. M. Pesko, S. Sawhney, J. Newman, N. P. Balsara, Comparing Two Electrochemical Approaches for Measuring Transference Numbers in Concentrated Electrolytes. Journal of The Electrochemical Society 165, A3014-A3021 (2018). 6. D. M. Pesko et al., Negative transference numbers in poly(ethylene oxide)-based electrolytes. Journal of the Electrochemical Society 164, E3569-E3575 (2017).

Zirconium nitride (ZrN) thin films were deposited by reactive RF magnetron sputtering on Ti-6Al-4V and Si (100) substrates for potential use in biomedical applications. The tribological behaviour was evaluated against bovine bone in dry condition using a pin-on-disc apparatus. Abrasion is the primary wear mechanism observed in ZrN/bone contact. The corrosion properties were determined through two electrochemical techniques: potentiodynamic polarization and electrochemical impedance spectroscopy. The coatings with reduced oxygen content provided: (i) good resistance against corrosion when exposed to physiological solution and (ii) better anti-bioadhesion against Staphylococcus aureus bacteria. Bourse PNE Ministère algérien

We report on the properties of high quality HVPE InN and on successful subsequent MBE growth of InN layers with improved characteristics on HVPE InN template substrates. InN layers were grown by HVPE on GaN/sapphire HVPE templates. The (00.2) XRD rocking curve of the best InN layer (RC) had the FWHM of about 375 arc sec, being the narrowest XRD RCs ever reported for HVPE InN. Transmission Electron Microscopy (TEM) revealed that at the GaN/InN interface, the threading dislocations that come from GaN were transmitted into the InN layer. We estimated the dislocation density in HVPE grown InN to be in the low 109 cm–2 range. Reflection high energy electron diffraction (RHEED) confirmed monocrystalline structure of the InN layers surface. Layers photoluminescence (PL) showed edge emission around 0.8 eV. Hall measured free electron concentration was in the range of 1019 -1020 cm–3 and electron mobility was ∼200 cm2/V s. MBE growth of InN was performed on the HVPE grown InN template substrate demonstrating the improvement of material quality in the case of homo-epitaxial growth of InN. Demonstration of the high quality HVPE InN materials opens a new way for InN substrate development. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)