Mullite bodies and methods of forming mullite bodies
AssigneeDow Global Technologies LLC
InventorsChandan K. Saha, Aleksander J. Pyzik, Sten A. Wallin, Arthur R. Prunier, JR., Clifford S. Todd
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Abstract
A method of forming a porous mullite composition of acicular mullite grains having improved properties is described, where the mullite is formed at some time in the presence of a fluorine containing gas. For example, it has been discovered that improved properties may result from heating the mullite to a high temperature in an atmosphere selected from the group consisting of water vapor, oxygen, an inert gas or mixtures thereof or forming the mullite composition from precursors having an Al/Si ratio of at most 2.95.
Claims32
1-23. (canceled)
A method of forming a porous acicular mullite composition having improved strength comprising,
- a) forming a mixture of one or more precursor compounds having the elements present in mullite wherein one of the precursor compounds is clay, wherein the mixture has an Al/Si ratio of at most 2.95,
- b) shaping the mixture into a porous green shape and
- c) heating the porous green shape of step (b) under an atmosphere having a fluorine containing gas that is separately provided and to a temperature sufficient to form a porous mullite composition substantially of acicular mullite grains that are essentially chemically bound, wherein the mullite composition has a bulk Al/Si stoichiometry of at most 2.95 to at least 2 and the acicular mullite grains have an Al/Si stoichiometry of at least 2.95 and the mullite composition has at most 2 percent by volume of a crystalline silica phase.
A porous mullite composition comprised substantially of acicular mullite grains that are essentially chemically bound, wherein the mullite composition has a bulk Al/Si stoichiometry of at most 2.95 to at least 2 and the acicular mullite grains have an Al/Si ratio of at least 2.95 and the mullite composition has at most 2 percent by volume of a crystalline silica phase and a glassy phase distributed on at least a portion of the mullite grains wherein the glassy phase is comprised of silica magnesium and iron.
A mullite composition comprised substantially of acicular mullite grains that are essentially chemically bound, wherein the mullite composition has a glassy phase distributed on at least a portion of the acicular mullite grains, said glassy phase having iron and magnesium essentially incorporated into the glassy phase.
Dependencies are inferred from the claim text.