Color screens on celluloid films or coatings

Abstract

This chapter elaborates the formation, microstructural distribution, chemical composition, and functional microstructure of glassy phases in ceramics. The glassy phase is believed to be the uncrystallized remnant of a liquid phase present during densification. In cases where the volume fraction of glassy phase is high, as in certain refractories or only partially crystallized glass-ceramics, it can be readily seen by optical microscopy between grains and as pockets at three-grain junctions. Examination by electron microprobe reveals that the glassy phases are highly siliceous and contain elements, such as sodium, aluminum, calcium, and iron, known to be commonly present as impurities in the starting powders. The existence of glassy phases along grain boundaries, particularly along the three-grain junctions, implies that the glass phase is topologically continuous through the microstructure. The presence of intergranular glassy phases has little effect on room temperature mechanical properties. Selected-area diffraction patterns recorded in the transmission electron microscope from the pockets of glassy phase down to approximately 3 nm in size exhibit the symmetrical ring symmetry and spacings expected from bulk glasses.