Mullite composites physical properties

Selected composite materials and their basic physical properties are summarized in Table 2. The GE GEN-IV all-oxide fiber composites have a relatively low volume fraction (30%) of Nextel 610 fiber and a matrix composed of alumina and silica with approximately 35% porosity [12, 30, 37]. COI produces a number of aluminosilicate matrix materials with a selection of different Nextel oxide fibers, but with higher fiber loading and matrix porosity than the GE materials [140, 141]. Two examples of nominally silica-free porous composites (Table 2) with improved thermal stabilities are the mullite-alumina formulation developed at UCSB [4,44,142,143] and the all-alumina COI N720/A-1 [75, 79, 141, 144],... 

Also known as bauxitland cement. Kurlbaum Method. A method for the determination of flame temperature by means of an optical pyrometer (F. Kurlbaum, Phys. Z., 3,187,1902). Kyanite. A mineral having the same composition (Al2SiOs) as sillimanite and andalusite, but with different physical properties. The chief sources are Virginia and S Carolina (USA), and India. When fired, kyanite breaks down at 1300°C into mullite and cristobalite with a volume expansion of about 10% it is therefore calcined before use. Calcined kyanite is used in making aluminous refractories. 

Sillimanite. A mineral having the same composition (Al2Si05) as kyanite and andalusite but with different physical properties. The chief sources are S. Africa and India. Sillimanite changes into a mixture of mullite and cristobalite when fired at a high temperature (1550°C) this change occurs without any significant alteration in volume (cf. kyanite). The mineral is used as a refractory. 

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