Study of surface changes on industrial glasses with AFM,FE-SEM,EDX,SNMS and LM:Part 1.Glass skin and corrosion

摘要

By combining different analytical techniques,including modern high resolution imaging tools such as field emission scanning electron microscopy(FE-SEM)and atomic force microscopy(AFM),new phenomena in the surface,near surface and bulk structure of various industrial glasses(without any cleaning process)have been discovered.Investigations of soda-lime-silica container glass and lead silicate glass tubings exposed to atmospheric and to dried air are presented.The results of the first part of this paper can be explained with an SiO_2-rich skin on the glass,which can protect the glass against the attack of external media.If the skin was mechanically injured,inhomogeneous corrosion products on mum scale grew around the injured site after exposure to humid air for times between days up to one year.Microchannels were formed through the injured site due to restricted ion exchange,followed by a local increase of the pH value and consequently the dissolution of the glass network.Finally some stress in the glass,yielded during manufacture,can be partially released and the cutting behaviour is improved.Faster cooling results in a thinner skin and the ions in the glass are able to migrate to the surface more easily when surrounded by some reactive media.Slower cooling results in thicker skin and wax-like droplets instead of crystallites are formed on the surface at a later stage in humid air.The wax-like droplets can etch the glass skin locally,followed by the growth of inhomogeneous corrosion products similar to the injury induced corrosion.If the fresh glass surface was hot-end treated,the quality of the adjacent coating layer depended strongly on the thickness of the skin.