Das Atomgewicht des Aluminiums

Ohne Zusammenfassung     

Sur les groupes de transformations des équations différentielles linéaires

Sans résuméAus den Comptes rendus des séances de l'Académie des Sciences, t. 119, Sitzung vom 8. Oktober 1894.     

Ternary MgTiX-alloys: a promising route towards low-temperature, high-capacity, hydrogen-storage materials

In the search for hydrogen-storage materials with a high gravimetric capacity, Mg(y)Ti((1-y)) alloys, which exhibit excellent kinetic properties, form the basis for more advanced compounds. The plateau pressure of the Mg--Ti--H system is very low (approximately 10(-6) bar at room temperature). A way to increase this pressure is by destabilizing the metal hydride. The foremost effect of incorporating an additional element in the binary Mg--Ti system is, therefore, to decrease the stability of the metal hydride. A model to calculate the effect on the thermodynamic stability of alloying metals was developed by Miedema and co-workers. Adopting this model offers the possibility to select promising elements beforehand. Thin films consisting of Mg and Ti with Al or Si were prepared by means of e-beam deposition. The electrochemical galvanostatic intermittent titration technique was used to obtain pressure-composition isotherms for these ternary materials and these isotherms reveal a reversible hydrogen-storage capacity of more than 6 wt. %. In line with the calculations, substitution of Mg and Ti by Al or Si indeed shifts the plateau pressure of a significant part of the isotherms to higher pressures, while remaining at room temperature. It has been proven that, by controlling the chemistry of the metal alloy, the thermodynamic properties of Mg-based hydrides can be regulated over a wide range. Hence, the possibility to increase the partial hydrogen pressure, while maintaining a high gravimetric capacity creates promising opportunities in the field of hydrogen-storage materials, which are essential for the future of the hydrogen economy.     

Gradient estimates for some diffusion semigroups

 Consider the semigroup $P_t$ of an elliptic diffusion; we describe a simple stochastic method providing gradient estimates on $P_tf$. If $N$ is a manifold endowed with a connection, the method can also be applied to the associated nonlinear semigroup $Q_t$ acting on $N$-valued maps. With a localization technique, we deduce gradient estimates for real harmonic functions or $N$-valued harmonic maps. Moreover, the results are extended to a class of hypoelliptic diffusions. Received: 31 July 2000 / Revised version: 20 September 2001 / Published online: 15 March 2002     

Assessing crystalline lamellae orientation impact on the properties of semi‐crystalline polymer‐clay nanocomposites

Semi‐crystalline polymer‐clay nanocomposite properties are often considered only by their clay dispersion state. The purpose of this work is to highlight texture effects on semi crystalline polymer‐clay properties. Maleic anhydride‐grafted polyethylene nanocomposites with two different processing techniques (Blown Extrusion and Compression) were studied. The processing was shown to induce different crystalline lamellae orientation in the films but with no significant changes in the crystalline lamellae long period, degree of crystallinity, clay particle orientation morphology and dispersion. The impact of these specific textures on the nanocomposites barrier and tensile properties were reported. © 2008 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 46: 1966–1975, 2008     

Etude en Spectrometrie de Masse: VI—Evaluation de l'Induction de la Fragmentation dans les amines β Fonctionnelles

Mass spectra of 22 β-function amines are compared with those of corresponding non-substited amines. Spectral analysis shows that fragmentation is not induceed by the lone-nitrogen atom: keto, ester, amide or nitrile groups also induce this fragmentation and the ratio was evaluated. This very elementary approach, supported by the kinetics of unimolecular reaction is in good agreement with results based on ionisation potential measurements.