Abstract: An optical article, which is a preform for an optical lens, which is isotropic, consisting essentially of silicon oxide or silicon oxide in combination with one or more oxides of elements belonging to Groups III to VI of the Periodic Table, the article having a dimensional precision which has tolerance to surface roughness and profilometric accuracy required in the spectral interval of 200-800 nm of the electromagnetic spectrum, the tolerance being between one-half and one-tenth wavelength corresponding to the range of about 0.350-0.02 &mgr;m.

Abstract: An optical article, which is a preform for an optical lens, which is an isotropically miniaturized, amorphous monolithic aerogel, consisting essentially of silicon oxide or silicon oxide in combination with one or more oxides of elements belonging to Groups III to VI of the Periodic Table, the article having a surface having a dimensional precision which has tolerance to surface roughness and profilometric accuracy required in the spectral interval of 200-800 nm of the electromagnetic spectrum, the tolerance being between one-half and one-tenth wavelength corresponding to the range of about 0.350-0.02 &mgr;m.

Abstract: A process for producing a linearly-miniaturized, densified optical product, which entails a) cold filling a mould with a liquid colloidal dispersion formed from a chemical precursor; b) polycondensing the liquid colloidal dispersion to obtain a gel; c) supercritically drying the gel to form an amorphous aerogel having dimensions corresponding to the mould; and d) isotropically miniaturizing the amorphous monolithic aerogel obtained.

Abstract: The preparation of objects, in particular optical components and/or devices, is described using, as precursors of optical materials, amorphous monolithic aerogels for high-precision mechanical machining.

Abstract: The present invention relates to a process for the preparation of mixed porous oxides with a spherical morphology and the oxides themselves thus obtained.This process consists in emulsifying, in an acid environment, a mixed sol with a dispersing medium, gelifying the microemulsion thus formed by contact with an alkaline solution and subjecting the gel obtained to thermal aging in the presence of the emulsifying liquid and gelation base of the sol or in a water medium, under controlled conditions of pH and temperature.The above mixed oxides can be widely applied as carriers for catalysts or as precursors of ceramic materials.