Silicon carbide whisker reinforced ceramic composites and method for making same
AssigneeThe United States of America as represented by the Department of Energy
InventorGeorge C. Wei
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Abstract
The present invention is directed to the fabrication of ceramic composites which possess improved mechanical properties especially increased fracture toughness. In the formation of these ceramic composites, the single crystal SiC whiskers are mixed with fine ceramic powders of a ceramic material such as Al.sub.2 O.sub.3, mullite, or B.sub.4 C. The mixtures which contain a homogeneous dispersion of the SiC whiskers are hot pressed at pressures in a range of about 28 to 70 MPa and temperatures in the range of about 1600.degree. to 1950.degree. C. with pressing times varying from about 0.75 to 2.5 hours. The resulting ceramic composites show an increase in fracture toughness of up to about 9 MPa.m.sup.1/2 which represents as much as a two-fold increase over that of the matrix material.
Claims11
A ceramic composite characterized by increased toughness and resistance to fracture, comprising a composite defined by a matrix of ceramic material having homogeneously dispersed therein about 5 to 60 vol. % of silicon carbide whiskers, with said silicon carbide whiskers having a monocrystalline structure and in a size range of about 0.6 .mu.m in diameter and a length of 10 to 80 .mu.m, said composite being of a density greater than about 99% of the theoretical density.
A method for preparing a ceramic composite having increased toughness and resistance to fracture, comprising the steps of forming a homogeneous mixture of particulate ceramic material with about 5 to 60 vol. % of silicon carbide whiskers having a monocrystalline structure and in a size range of about 0.6 .mu.m diameter and a length of about 10 to 80 .mu.m, and hot pressing the mixture at a pressure in the range of about 28 to 70 MPa and temperature in the range of about 1600.degree. to 1900.degree. C. for a duration of 0.75 to 2.5 hours to provide a composite with a density greater than about 99% of the theoretical density of the ceramic material.
Dependencies are inferred from the claim text.