1. Scientific Foundations Of Hollow Glass Microspheres 1.one Composition and Microstructure one.1.1 Chemical Composition: Borosilicate Dominance Hollow glass microspheres (HGMs) are mostly made up of borosilicate glass, a material renowned for its very low thermal expansion coefficient and chemical inertness. The chemical make-up usually features silica (SiO₂, 50-90%), alumina (Al₂O₃, https://friendstrs.com/post/167844_metallic-boride-powders-are-very-unique-but-functional-new-ceramic-materials-the.html