ALKALINE GLASSES WITH MODIFIED GLASS SURFACES AND PROCESS FOR THE PRODUCTION

摘要

The invention concerns alkaline glasses with modified surfaces. The inventio n aims at stabilizing the modified surfaces so as to substantially prevent a sodium reverse diffusion from the volume even at high temperatures and, in particular in case of flame reprocessing. Quite unexpectedly, it has been observed that the modified surface of an alkaline glass is, at high temperatures, substantially resistant to sodium reverse diffusion from the volume if the internal chemism of the surface has an aluminium concentration much higher than that of the volume. This is due to the very high negative enthalpy of formation . The invention is characterized in that the surface o f such glasses is contacted with high aluminium concentrations and is heat- treated.