Effect of starting materials of nucleation agents on crystallization of CaO-Al2O3-SiO2 glass

The effect of the starting materials of the nucleation agents for glass-ceramics (GCs) was explored. The number of hexagonal platy particles of metastable-CaAl2Si2O8 in CaO-Al2O3-SiO2 (CAS) GCs was increased by changing the sizes of molybdenum oxide (MoO3) and carbon particles used as starting materials of the nucleation agents. X-ray diffraction patterns indicated that all of GC specimens display reflections attributed to metastable-CaAl2Si2O8 solely. In addition, scanning electron microscopy (SEM) revealed that, compared with the CAS GC with precipitated hexagonal platy particles of metastable-CaAl2Si2O8 (CAS GC-H) prepared using MoO3 particles with a Brunauer-Emmett-Teller (BET) surface area of 3.5 m(2)/g and 10-50 mu m carbon particles, CAS GC-Hs prepared using MoO3 particles with a BET surface area of 1.2 m(2)/g or carbon fibers 10-50 mu m in length and similar to 5 mu m in diameter resulted in approximately a twofold increase in the number of platy particles of metastable-CaAl2Si2O8 and a decrease in the average particle size from 13 to 11 mu m. The microstructures of the CAS GC-Hs are closer looks. In addition, no major differences in volume fractions estimated using the binarized SEM images are observed between those GC specimens. These results indicated that the starting materials of nucleation agents affect the crystallization of CAS GCs.