Oxide gels are amorphous and porous materials. The main recent challenge in the investigations of these materials is to reduce and even eliminate their porosity while keeping their starting amorphous nature. In this paper, we describe how, during the last few years, the understanding of both their structural and textural evolutions with temperature allowed to fully densify gels at temperatures as low as the glass-transition temperature corresponding to the parent glass. Regarding their structure, glasses are very peculiar materials. And regarding their technological applications, glasses are conventionally produced in a variety of shapes. Working of glasses may also be achieved using gels as starting materials. And for several applications, scientists use gels to synthesise specific compositions, materials having peculiar functions or shapes that are difficult to obtain using traditional melting processes.
Les gels d'oxydes sont des materiaux amorphes et poreux. Un concept recent consiste a tenter d eliminer la porosite, tout en maintenant le caractere amorphe du compose de depart. Au cours de ces dernieres annees, la comprehension des evolutions structurales et texturales des gels en fonction de la temperature a permis de les densifier totalement a des temperatures voisines de celle de la temperature de transition vitreuse du verre correspondant. Au-dela de sa structure particuliere, le verre est aussi un materiau qui, technologiquement, se presente sous des formes variees. Ces formes diverses sont aussi realisables a partir de gels. Dans des cas tres precis, les gels permettent de concevoir des compositions, des fonctions ou des formes difficiles a obtenir par les methodes d'elaboration classiques.