Ceramic articles and methods for preparing ceramic articles and for sintering
AssigneeEastman Kodak Company
InventorsDilip K. Chatterjee, Debasis Majumdar, Syamal K. Ghosh, Jose M. Mir
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Abstract
A method for preparing a ceramic article comprising compacting a particulate including a primary oxide and a secondary oxide to form a blank. The primary oxide is ZRO.sub.2 and the secondary oxide is MgO, CaO, Y.sub.2 O.sub.3, Sc.sub.2 O.sub.3, rare earth oxides or a combination thereof. The blank is sintered in contact with MgO, CaO, Y.sub.2 O.sub.3, Sc.sub.2 O.sub.3, rare earth oxides or a combination thereof. The zirconia alloy ceramic articles produced have a cubic phase case and a tetragonal phase core.
Claims14
A method for preparing a net shape ceramic article having a tetragonal crystal structure core and a cubic crystal structure case, said method comprising the steps of
- compacting a particulate alloy of ZrO.sub.2 and a secondary oxide selected from the group consisting of MgO, CaO, Y.sub.2 O.sub.3, Sc.sub.2 O.sub.3, rare earth oxides and combinations thereof, to form a blank, said particulate alloy having a molar ratio of secondary oxide to ZrO.sub.2 of from about 2:98 to about 5:95, a grain size from about 0.1 to about 0.6 micrometers, an agglomerate size of from about 30 to about 60 micrometers, said blank having a density of from about 40 to about 65 percent of the density of said tetragonal crystal structure core of said ceramic article;
- heating said blank from room temperature to a sintering temperature from about 1400.degree. C. to about 1600.degree. C.;
- maintaining said blank at said sintering temperature from about 1 hour to about 3 hours;
- contacting said blank with oxide selected from the group consisting of MgO, CaO, Y.sub.2 O.sub.3, Sc.sub.2 O.sub.3, rare earth oxides and combinations thereof during said maintaining step;
- and
- cooling said blank from said sintering temperature to room temperature;
- said heating and cooling steps having temperature ramps of less than 2.degree. C./minute and
- wherein dimensional shrinkage of said blank during said heating, maintaining and cooling steps is uniform to within 0.001 percent.
A method for preparing a ceramic article having a tetragonal crystal structure core and a cubic crystal structure case, said method comprising the steps of
- compacting a particulate alloy of ZrO.sub.2 and a secondary oxide selected from the group consisting of MgO, CaO, Y.sub.2 O.sub.3, Sc.sub.2 O.sub.3, rare earth oxides and combinations thereof, to form a blank, said particulate alloy having a molar ratio of secondary oxide to ZrO.sub.2 of from about 2:98 to about 5:95, a grain size from about 0.1 to about 0.6 micrometers, an average grain size of 0.3 micrometers, an agglomerate size of from about 30 to about 60 micrometers, an average agglomerate size of 50 micrometers, and a moisture content of from about 0.2 to 1.0 percent, said blank having a density of from about 40 to about 65 percent of the density of said tetragonal crystal structure core of said ceramic article;
- heating said blank from room temperature to 300.degree. C. at a rate of 0.3.degree. C./minute, from 300.degree. C. to 400.degree. C. at a rate of 0.1.degree. C./minute, from 400.degree. C. to 600.degree. C. at a rate of 0.4.degree. C./minute, from 600.degree. C. to 1500.degree. C. at a rate of 1.5.degree. C./minute;
- maintaining said blank at 1500.degree. C. for 2 hours;
- and
- contacting said blank with oxide selected from the group consisting of MgO, CaO, Y.sub.2 O.sub.3, Sc.sub.2 O.sub.3, rare earth oxides and combinations thereof during said maintaining step;
- and
- cooling said blank from 1500.degree. C. to 800.degree. C. at a rate of 2.degree. C./minute, from 800.degree. C. to room temperature at a rate of 1.6.degree. C./minute;
- wherein dimensional shrinkage of said blank during said heating, maintaining, and cooling steps is uniform to within 0.001 percent.
Dependencies are inferred from the claim text.