Colloids for Catalysts: A Concept for the Preparation of Superior Catalysts of Industrial Relevance

Compared to conventional preparation methods for supported heterogeneous catalysts, the use of colloidal nanoparticles (NPs) allows for a precise control over size, size distribution, and distribution/location of the NPs on the support. However, common colloidal syntheses have restrictions that limit their applicability for industrial catalyst preparation. We present a simple, surfactant‐free, and scalable preparation method for colloidal NPs to overcome these restrictions. We demonstrate how precious‐metal NPs are prepared in alkaline methanol, how the particle size can be tuned, and how supported catalysts are obtained. The potential of these colloids in the preparation of improved catalysts is demonstrated by two examples from heterogeneous catalysis and electrocatalysis.     

Adhesion in elastic-plastic spherical microcontact

An elastic-plastic adhesion model for a metallic deformable sphere pressed by a rigid flat is presented. Analytical dimensionless expressions for the local separation outside the contact area and for the adhesion force are provided covering a large range of interference values from a point contact to a fully plastic contact. Two main dimensionless parameters of the problem are identified and their effect on the adhesion is investigated. The significance of the adhesion in the elastic-plastic contact force balance is discussed and the regimes where adhesion is important or negligible are pointed out. A comparison of the present results with a previously published approximate elastic-plastic model shows substantial differences in the local separation and in the adhesion force.     

Différentiabilité de la composition et complétitude de certains espaces fonctionnels

Sans résumé Ce travail a été partiellement subventionné par le Fonds National Suisse pour la Recherche scientifique.