High strength polycrystalline ceramic spheres
First Claim
1. A method for making hollow spheres of alumina or aluminate comprising:
- a) coating polymeric beads with an aqueous solution of an alumoxane;
b) drying the beads so as to form an alumoxane coating on the beads;
c) heating the beads to a first temperature, wherein the first temperature is sufficient to convert the alumoxane coating to an amorphous alumina or aluminate coating and is not sufficient to decompose the polymeric beads;
d) dissolving the polymeric bead in a solvent;
e) removing the dissolved polymer from the amorphous alumina or aluminate coating; and
f) heating the amorphous alumina or aluminate coating to a second temperature that is sufficient to form a hollow ceramic sphere of desired porosity and strength.
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Accused Products
Abstract
A method for making hollow spheres of alumina or aluminate comprises: coating polymeric beads with an aqueous solution of an alumoxane, drying the beads so as to form an alumoxane coating on the beads; heating the beads to a first temperature that is sufficient to convert the alumoxane coating to an amorphous alumina or aluminate coating and is not sufficient to decompose the polymeric beads; dissolving the polymeric bead in a solvent; removing the dissolved polymer from the amorphous alumina or aluminate coating; and heating the amorphous alumina or aluminate coating to a second temperature that is sufficient to form a hollow ceramic sphere of desired porosity and strength. The hollow spheres can be used as proppants or can be incorporated in porous membranes.
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Citations
20 Claims
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1. A method for making hollow spheres of alumina or aluminate comprising:
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a) coating polymeric beads with an aqueous solution of an alumoxane;
b) drying the beads so as to form an alumoxane coating on the beads;
c) heating the beads to a first temperature, wherein the first temperature is sufficient to convert the alumoxane coating to an amorphous alumina or aluminate coating and is not sufficient to decompose the polymeric beads;
d) dissolving the polymeric bead in a solvent;
e) removing the dissolved polymer from the amorphous alumina or aluminate coating; and
f) heating the amorphous alumina or aluminate coating to a second temperature that is sufficient to form a hollow ceramic sphere of desired porosity and strength. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12)
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13. A hollow sphere of alumina or aluminate wherein:
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the surface of the sphere is porous;
the hardness of the sphere is at least 750 kg/mm2 on the Vickers hardness scale; and
the diameter of the sphere is approximately 3 μ
m. - View Dependent Claims (14)
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15. A method for making a porous membrane, comprising:
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a) providing a colloidal suspension comprising hollow spheres of alumina or aluminate;
b) coating a porous refractory support with the colloidal suspension;
c) drying the coated support; and
d) firing the dried coated support to a temperature sufficient to achieve a desired porosity and hardness of the membrane. - View Dependent Claims (16, 17)
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18. A method for making a porous membrane, comprising:
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a) providing a colloidal suspension comprising colloidal polymeric beads suspended in an aqueous solution of an alumoxane;
b) coating a porous refractory support with the colloidal suspension;
c) drying the coated support; and
d) firing the dried coated support to a temperature sufficient to achieve a desired porosity and hardness of the membrane. - View Dependent Claims (19, 20)
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Specification