Mines ParisTech

About: Mines ParisTech is a education organization based out in Paris, France. It is known for research contribution in the topics: Finite element method & Microstructure. The organization has 6564 authors who have published 11676 publications receiving 359898 citations. The organization is also known as: École nationale supérieure des mines de Paris & École des mines de Paris.

Strengthening of silica gels and aerogels by washing and aging processes

Abstract: Gels were prepared from a polyethoxydisiloxane precursor by using HF as a catalyst. During washing in water solution a significant increase in the permeability of the gels was observed, showing that dissolution-reprecipitation occurs. After washing, the gels were further soaked in a solution of polyethoxydisiloxane precursor to strengthen and stiffen the gel. As expected, a significant enhancement of the mechanical properties of the wet gels was observed. It is also interesting to note, however, that the permeability does not decrease below the value for the as-prepared gels. Hence, a promising process has been developed where both the stiffness and the strength have been increased as well as the permeability. The increase in permeability is of importance to facilitate the supercritical drying process. Reasonably successful scaling up of the supercritical drying of these gels to laboratory scale has been achieved, and monolithic and transparent gels are obtained. Optical properties have been measured on laboratory scale aerogels. The corresponding results have been correlated with structural characteristics measured by small-angle X-ray scattering (SAXS).

Recent α decay half-lives and analytic expression predictions including superheavy nuclei

Abstract: New recent experimental \ensuremath{\alpha} decay half-lives have been compared with the results obtained from previously proposed formulas depending only on the mass and charge numbers of the \ensuremath{\alpha} emitter and the ${Q}_{\ensuremath{\alpha}}$ value. For the heaviest nuclei they are also compared with calculations using the Density-Dependent M3Y (DDM3Y) effective interaction and the Viola-Seaborg-Sobiczewski (VSS) formulas. The correct agreement allows us to make predictions for the \ensuremath{\alpha} decay half-lives of other still unknown superheavy nuclei from these analytic formulas using the extrapolated ${Q}_{\ensuremath{\alpha}}$ of G. Audi, A. H. Wapstra, and C. Thibault [Nucl. Phys. A729, 337 (2003)].