Electron Micrographs of Some Borosilicate Glasses and Their Internal Structure

Abstract

Many electron micrographs were obtained for borosilicate glass which had been subjected to chemical attack after heat‐treatment at various temperatures and durations in order to study changes in internal structure, the so‐called “phase separation.” Both replica and direct‐transmission methods were applied to Vycor‐type glass. The two kinds of picture showed good agreement with each other. The conclusions obtained are as follows: (1) So‐called quenched‐state glass contains a glassy microphase of alkali borate, with dimensions less than 100 a.u., which corresponds to the so‐called low‐melting component; (2) the longer the heat‐treatment time under constant temperature the larger the size of this glassy microphase becomes; (3) another kind of glassy microphase (SiO2‐rich) which corresponds to the so‐called high‐melting component is also enlarged with increasing heat‐treatment time; (4) the size of both glassy microphases shows different values with different heat‐treatment temperatures. Based on the experimental results described, a discussion of the relation between the internal structure and some physical properties of the glass is presented.