1. Scientific Foundations of Hollow Glass Microspheres one.1 Composition and Microstructure 1.one.one Chemical Composition: Borosilicate Dominance Hollow glass microspheres (HGMs) are mainly made up of borosilicate glass, a material renowned for its very low thermal expansion coefficient and chemical inertness. The chemical makeup usually includes silica (SiO₂, 50-90%), alumina (Al₂O₃, https://500px.com/photo/1117584688/boride-powder-by-okok-okok