Glass-ceramics from a zinc-electroplating solid waste: Devitrification promoted further crystallization of parent glass upon heat treatment

A solid waste from a zinc electroplating production line was successfully used as a main raw material for synthesizing glass-ceramics with a fine microstructure. X-ray fluorescence spectroscopy analysis on dried solid waste shows that the waste mainly contains iron and zinc oxides. X-ray diffraction (XRD) analysis identifies Fe3O4 and ZnO phases in calcined waste samples. Based on the above results, silica sand, lime stone and potassium feldspar were proportionally added to make parent glasses by melting the batches at 1450 °C for 2 h. The as-synthesized products show typical DSC and thermal expansion curves with obvious glass transition phenomenon. However, XRD patterns reveal that they had devitrified to form ZnFe2O4 phase during the shaping and cooling of the melts. The devitrification became weaker when more potassium feldspar was added. It is interesting to find that the pre-crystallization of ZnFe2O4 in the devitrified sample was beneficial to its further crystallization during the following heat-treatment. The result implies that the devitrification of parent glasses is not necessarily a detriment to the preparation of glass-ceramics via controlled crystallization process.