Zirconium oxide fibers and process for their preparation

Abstract

Improved silicone-free, continuous zirconia fibers have diameters greater than 5 micrometers and high tensile strengths. In another aspect, strong, flexible, zirconia fibers are prepared in a process involving the addition of colloidal ZrO2 particles to a fiber precursor solution.

What is claimed is: 
     
       1. A silicon-free green fiber comprising: (a) crystalline colloidal zirconia particles with diameters in the range of 5 to 200 nm,   (b) at least one water soluble zirconium compound, and   (c) residual solvent.   
     
     
       2. The green fiber according to claim 1 wherein said crystalline colloidal zirconia particles comprise 20 to 80 weight percent of the total zirconia equivalent present in said fiber. 
     
     
       3. The green fiber according to claim 1 wherein said soluble zirconia compound comprises 20 to 80 weight percent of the total zirconia equivalent present in said fiber. 
     
     
       4. The green fiber according to claim 1 wherein said soluble zirconium compound is zirconyl acetate. 
     
     
       5. The green fiber according to claim 1 wherein said solvent is water. 
     
     
       6. The green fiber according to claim 1 further comprising at least one of: (a) a water soluble compound or sol of metals whose oxides are phase change stabilizers for zirconium oxide wherein said metals comprise more than 0 and up to 20 mole percent of the total equivalent moles of zirconia present;   (b) at least one water soluble compound or sol of metals whose oxides are grain growth inhibitors for zirconium oxide and wherein said metals comprise more than 0 and up to 20 mole percent of the total equivalent moles of zirconia present;   (c) at least one water soluble catalyst or its precursor wherein said catalyst or precursor comprises more than 0 and up to 10 oxide equivalent mole percent of the total equivalent moles of zirconia present; and   (d) a water soluble organic polymer wherein said polymer comprises more than 0 and up to 50 wt. percent of the total zirconia mass content of the fiber.   
     
     
       7. The green fiber according to claim 6 wherein said phase change stabilizer for zirconium oxide is a compound or sol of a metal selected from the group consisting of yttrium, magnesium, calcium, and cerium. 
     
     
       8. The green fiber according to claim 6 wherein said grain growth inhibitor is aluminum. 
     
     
       9. The green fiber according to claim 6 wherein said water soluble catalyst or its precursor is selected from the group consisting of chromium, cobalt, copper, iron, nickel, palladium, platinum and vanadium; their respective oxides, and their respective soluble salts or sols. 
     
     
       10. The green fiber according to claim 6 wherein said water soluble organic polymer is selected from the group consisting of polyethyleneglycol, polyethylene oxide, polyvinylacetate, polyvinylalcohol, and polyvinylpyrrolidone. 
     
     
       11. The green fiber according to claim 6 wherein said s organic polymer comprises 20 to 40 weight percent of the total zirconia content of said fiber. .[.12. A ceramic fiber comprising crystalline zirconia grains having a grain size of at most 1.0 micrometer, said fiber having a diameter in the range of 10 to 60 micrometers and a tensile strength 
     
     
        greater than 0.5 GPa..]. 13. A yarn prepared from the fibers of claim 
     
     
        .[.12.]. .Iadd.21.Iaddend.. 14. A knitted fabric prepared from the fibers 
     
     
        of claim 13. 15. A woven or non-woven fabric prepared from the fibers of 
     
     
        claim .[.12.]. .Iadd.21.Iaddend.. 16. A process of making a ceramic fiber containing crystalline zirconia grains comprising the steps of: (a) mixing crystalline, colloidal zirconia particles, at least one soluble zirconia compound, and solvent;   (b) concentrating said mixture;   (c) extruding or blowing .[.said fiber to provide.]. a green fiber .Iadd.from said mixture.Iaddend.; and   (d) heating said green fiber to a temperature in the range of 400° to 2000° C. in an oxygen-containing atmosphere to provide said .Iadd.ceramic .Iaddend.fiber .[.containing crystalline colloidal zirconia   
     
     
        particles.].. 17. A process of making a ceramic fiber containing crystalline zirconia .[.particles.]. .Iadd.grains .Iaddend.comprising the steps of: (a) mixing crystalline, colloidal zirconia particles, at least one soluble zirconium compound, solvent, and at least one of: (1) a water soluble compound or sol of metals whose oxides are phase change stabilizers for zirconium oxide wherein said metals comprise more than 0 and up to 20 mole percent of the total equivalent moles of zirconia present;   (2) at least one water soluble compound or sol of metals whose oxides are grain growth inhibitors for zirconium oxide and wherein said metals comprise more than 0 and up to 20 mole percent of the total equivalent moles of zirconia present;   (3) at least one water soluble catalyst or its precursor wherein said catalyst or precursor comprises more than 0 and up to 10 oxide equivalent mole percent of the total equivalent moles of zirconia present; and   (4) a water soluble organic polymer wherein said polymer comprises more than 0 and up to 50 wt. percent of the total zirconia mass content of the fiber;     (b) concentrating said mixture;   (c) extruding or blowing .[.said fiber to provide.]. a green fiber .Iadd.from said mixture.Iaddend.; and   (d) heating said green fiber to a temperature in the range of 400° to 2000° C. in an oxygen-containing atmosphere to provide said ceramic fiber .[.containing crystalline colloidal zirconia particles.]..   
     
     
          . The ceramic fiber according to claim 16 which is a continuous fiber 
     
     
        made by the process having a length greater than 1 meter. 19. A continuous zirconia fiber prepared according to the process of claim 16, having a diameter in the range of 10 to 60 micrometers, and a tensile strength 
     
     
        greater than 0.5 GPa. 20. The ceramic fiber according to claim .[.12.]. .Iadd.21 .Iaddend.having a diameter in the range of 17 to 60 micrometers. 
     
     
        .Iadd.21.  The fiber prepared according to the process of claim 16, said fiber having a diameter in the range of 10 to 60 micrometers and a tensile strength greater than 0.5 GPa, said zirconia grains having a grain size of at most 1.0 micrometer, said fiber comprising at least 89.2 mole percent zirconia. .Iaddend.