CPC C04B 35/101 (2013.01) [C04B 35/6264 (2013.01); C04B 38/067 (2013.01); C04B 41/0072 (2013.01); C04B 2235/3217 (2013.01); C04B 2235/608 (2013.01); C04B 2235/658 (2013.01); C04B 2235/94 (2013.01); C04B 2237/343 (2013.01); C04B 2237/525 (2013.01); C04B 2237/765 (2013.01); C04B 2237/84 (2013.01)] | 24 Claims |
1. A dual density disc comprising:
a dense outer tube comprising alumina having a purity of greater than 96%; and
a porous core comprising alumina of a lower density than a density of the dense outer tube; wherein the porous core has an alumina purity of greater than 99%.
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