Utilization of alumosiliceous waste products for production of finishing materials

Microstructures of alkoxide-derived barium osumilite (BaMg2Al6Si9O30) glass ceramics

“…The microstructures observed in PAR and AAR Baosumilite glass ceramics are similar to those observed by Winter [8,9] and Varshal [10] in their crystallisation studies of melt-derived osumilite. The only obvious difference is in the formation of the first precursor phases which give rise to regions of Ba-rich residual glass from which barium osumilite nucleates and grows.…”

“…The close values of a according to Winter and Berger [8] explain the formation of cordierite in the crystallisation of osumilite. The presence of cordierite as a secondary phase has also been reported in other studies on melted aluminosilicate systems with osumilite compositions [9,10].…”

“…This glass would be expected to be Ba and Mg rich in PAR and only Mg rich in AAR because the formation of mullite and hexacelsian as the main precursor phases in PAR and AAR respectively would draw some A1 in PAR and Ba plus A1 in AAR from the surrounding glass, from which according to Winter and Berger [8] Ba-osumilite crystals nucleate and grow. Varshal and Levitina [10] reported that metastable crystal phases formed in the initial stages of the crystallisation of aluminosilicate glasses containing Ba and Mg, interact with Ba and Mg phases to form osumilite. This was associated with the formation of an inhomogeneous glass structure with regions rich in both Mg-aluminate and Ba-aluminate complexes.…”

“…Crystallisation studies were performed using a Philips 1710 X-ray powder diffractometer operating at 50 kV and 30 mA. Qualitative analysis of the concentrations of the various crystallising phases appearing after 1 hour heat treatments of the gel powders at various temperatures was done by estimating the intensities of the main peaks in the XRD patterns [10]. The microstructures were examined in heat treated pellets which were made from fine gel powders (<63/zm) and uniaxially pressed at 250 MPa.…”