Upon consideration of the SiO2???Al2O3 phase diagram, Figure, for each pair of the following list of compositions, which would you judge to be the more desirable refractory? Justify your choices.

(a) 20 wt% Al2O3-80 wt% SiO2 and 25 wt% Al2O3-75 wt% SiO2

(b) 70 wt% Al2O3-30 wt% SiO2 and 80 wt% Al2O3-20 wt%SiO2

Transcribed Image Text:

Composition (mol % Al203) 80 20 40 60 2200 4000 3800 2000 Liquid Liquid 3600 Alumina 3400 1890 + 10°C 1800 Mullite (s) Cristobalite 3200 Mullite (ss) Liquid Liquid Alumina 3000 Mullite (ss) 1587 : 10°C 1600 Mulite (ss) 2800 Cristobalite 2600 1400 20 100 40 60 80 (SIO,) (Al203) Composition (wt % Al;03) Temperature ("C) Temperature ("F)