OXYCARBIDE GLASSES IN THE MG-AL-SI-O-C SYSTEM

Oxycarbide glasses in the Mg-Al-Si-O-C system were produced at initial carbon levels of 0. 0, 0. 5, 1. 0, 1. 5, 2. 0, and 2. 5 wt%. Carbon was incorporated into the glass melts by means of SiC additions. The glasses were melted between 1750 degree and 1800 degree C under nitrogen atmospheres. The limit of carbon incorporation was reached at the 2. 5% carbon level, as these glasses crystallized (predominantly cordierite, 2MgO multiplied by (times) 2Al//2O//3 multiplied by (times) 5SiO//2) upon gradual cooling from the melt. Glasses containing less than 2. 5% carbon were amorphous according to standard X-ray diffraction methods. Further examination of these oxycarbide glasses by transmission electron microscopy indicated the lack of microcrystalline phases and the potential for producing clear inclusion-free glasses. The Mg-Al-Si-O-C glasses showed significant increases in density, Young's elastic modulus, shear modulus, Vickers hardness, and fracture toughness with increasing carbon content.