Near zero coefficient of thermal expansion of beta-eucryptite without microcracking
OwnerIvar Reimanis, Subramanian Ramalingaminventors
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Abstract
The present invention is drawn to a lithia alumina silica material that exhibits a low CTE over a broad temperature range and a method of making the same. The low CTE of the material allows for a decrease in microcracking within the material.
Claims20
A method for producing a doped low thermal expansion lithia alumina silica material, comprising:
- mixing a source of silica comprising an orthosilicate with an alcohol and a water to produce a first mixture comprising a first volumetric ratio of about 0.5 to about 1.5 parts of the orthosilicate to about 1.0 parts of the alcohol, and a second volumetric ratio of about 0.1 to about 1.0 parts of the water to about 1.0 part of the orthosilicate;
- adjusting the pH of the first mixture to between about 0.5 and about 4.0 by addition of an acid to produce a pH adjusted mixture;
- modifying the pH adjusted mixture by adding a source of alumina comprising an aluminum salt, adding a source of lithia comprising a lithium salt, and adding a metal salt, wherein the metal salt comprises a metal and a counter-ion, to produce a suspension comprising an elemental ratio of about 1 part of aluminum to about 1 part silicon to about 1 part lithium, and a metal concentration in the range of about 0.01 mole % to about 10 mole % of the metal, wherein the metal concentration is relative to the total amounts of the lithium in the suspension;
- and processing the suspension to produce the doped low thermal expansion lithia alumina silica material.
A method for producing a zinc doped low thermal expansion lithia alumina silica material, comprising:
- mixing for a time period between about 30 minutes to about 60 minutes a silica source comprising tetraethylorthosilicate with ethanol and distilled water to produce a mixture comprising a first volumetric ratio of about 1.0 parts of the tetraethylorthosilicate to about 1.0 parts of the ethanol, and a second volumetric ratio of about 0.5 parts of the distilled water to about 1.0 parts of the tetraethylorthosilicate;
- adjusting the pH of the mixture to between about 0.5 and about 4.0 by addition of nitric acid to produce a pH adjusted mixture;
- modifying the pH adjusted mixture by adding a source of aluminum comprising aluminum nitrate, adding a source of lithium comprising lithium nitrate, and adding a source of zinc comprising zinc nitrate, to produce a suspension comprising an elemental ratio of about 1 part of aluminum to about 1 part silicon to about 1 part lithium, and a zinc concentration of between about 0.01 mole % to about 10 mole % of zinc, wherein the zinc concentration is relative to the total amounts of the alumina, the lithia, the silica, and the zinc in the suspension;
- forming a gel by adding aqueous ammonia to the suspension;
- drying the gel at a temperature between about 60° C. to about 100° C. for a period of time between about 24 hours to about 48 hours to produce a powder;
- calcining the powder at a temperature between about 900° C. to about 1200° C. for a period of time between about 10 hours to about 36 hours to form a calcined powder;
- grinding the calcined powder to form a ground powder comprising a nominal particle size of about between about 1 μm to about 2 μm;
- and
- sintering the ground powder at a temperature between about 1100° C. and about 1300° C. for between about 1 hour to about 4 hours, under an applied load of between about 20 MPa to about 40 MPa, in a vacuum hot press to produce the zinc doped low thermal expansion lithia alumina silica material.
A doped low thermal expansion lithia alumina silica material, comprising a first elemental ratio of about 1 part of aluminum to about 1 part silicon to about 1 part lithium, and a metal dopant concentration in the range of about 0.01 mole % to about 10 mole %, wherein the metal dopant concentration is relative to the total amount of the lithium.
Dependencies are inferred from the claim text.