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  Composite components for use in high temperature applicationsUSPTO Application #: 20060135344Title: Composite components for use in high temperature applications Abstract: Fibrous monolith composites suitable for use in high temperature environments and/or harsh chemical environments are provided, along with methods of preparation thereof. The fibrous monolith composites exhibit such beneficial properties as enhanced strength, corrosion resistance, thermal shock resistance and thermal cycling tolerance. (end of abstract) Agent: Banner & Witcoff, Ltd. - Chicago, IL, US Inventors: Mark J. Rigali, Manish P. Sutaria, Greg E. Hilmas, Anthony C. Mulligan, Marlene Platero-AllRunner, Mark M. Opeka USPTO Applicaton #: 20060135344 - Class: 501095100 (USPTO) Related Patent Categories: Compositions: Ceramic, Ceramic Compositions, Refractory, Fiber Or Fiber Containing The Patent Description & Claims data below is from USPTO Patent Application 20060135344. Brief Patent Description - Full Patent Description - Patent Application Claims
CROSS-REFERENCE TO RELATED APPLICATIONS [0001] This application is a continuation of co-pending U.S. patent application Ser. No. 10/013,601, filed on Dec. 4, 2001, and entitled "Composite Components for Use in High Temperature Applications," which is based on and claims the benefit of U.S. Provisional Application Ser. No. 60/251,170, filed on Dec. 4, 2000, and entitled "High Performance Fibrous Monolith X-Ray Target," and U.S. Provisional Application Ser. No. 60/251,133, filed on Dec. 4, 2000, and entitled "High Temperature Carbide, Oxide, Nitride, Silicide, And Boride Based Fibrous Monoliths For High Temperature Application." These applications are incorporated by reference in their entirety. FIELD OF THE INVENTION [0003] The present invention relates to multi-component composites, such as fibrous monolith ceramic composites, suitable for use in materials and structures that are subject to harsh environmental conditions, including extreme temperatures, chemical atmospheres and thermal shock, and methods of preparing the same. The high temperature FM composites have increased thermal shock resistance and increased thermal cycling tolerance. BACKGROUND OF THE INVENTION [0004] Certain carbides, nitrides, borides, oxides, phosphates and silicides exhibit enhanced mechanical properties, including enhanced strength, oxidation resistance, damage tolerance and wear resistance. As a result, these materials have found use in high temperature applications where the materials are subject to extreme temperatures (greater than 3000.degree. C.), as well as corrosive environments. For example, many of the carbides, nitrides, borides, oxides, phosphates and silicides of the elements from Groups IVb, Vb, and VIb of the periodic table, as well as carbides, nitrides, borides, oxides, and silicides of boron, aluminum, and silicon have been used in industrial and other applications where such conditions are likely to be encountered. Generally, structures formed of these materials exhibit improved strength and hardness at ambient and elevated temperatures, improved toughness and wear resistance, high melting points, thermal shock resistance, and oxidation resistance. [0005] Historically, ZrB.sub.2 and HfB.sub.2 based materials have been the choice for high-temperature ablation resistance in oxidizing environments. They have high melting points (about 3000.degree. C.), excellent oxidation resistance, elevated temperature creep resistance, and moderate resistance to thermal shock. The addition of SiC boosts their resistance to oxidation at intermediate temperatures to produce the best performing diboride material. Above 2200.degree. C. it is the high melting point carbides of Zr, Ta, and Hf (3540.degree. C., 3880.degree. C., and 3890.degree. C., respectively) and not the diborides that exhibit the best oxidation resistance. TaC-HfC solid solutions (e.g. 80% TaC-20% HfC) have high melting temperatures and even better oxidation resistance than the individual Hf and Ta carbides. However, the use of these monolithic materials has been limited due to their poor resistance to thermal shock. [0006] As a more specific application, materials capable of withstanding high temperatures are desired for use in X-ray system design, particularly for the X-ray target. The maximum X-ray power output from an X-ray tube is an important parameter in the operation and maintenance of a radiological system. The time period required to inspect an object is inversely proportional to the X-ray power output. For a given X-ray power output of the X-ray tube, the tube lifetime is directly proportional to its maximum power rating. Accordingly, higher values for the maximum X-ray power output are desirable to reduce the inspection times and the throughput of patients or objects examined with the radiological system, as well as to reduce the maintenance and operating costs as a result, in part, of the longer tube lifetimes. Because of the inefficiencies related to X-ray sources, storage and movement of waste heat from the radiation source is an important consideration in the design of X-ray systems. The thermal expansion match between the substrate and the target material and the ability of the target material to contribute to the high voltage stability are important material characteristics to be considered when designing an X-ray target. [0007] Target materials for X-rays have been made of Cu or similar materials and cooled with circulating oil or water. Other targets utilize standard carbon backed metal targets, which provide improved performance compared to Cu-based targets by eliminating the required cooling but have the disadvantage of an inability of the braze composition to withstand the temperature profiles that are experienced during operation. Where Cu or similar targets with low melting temperatures are used, active target cooling is required to withstand the high temperature during operation, thereby increasing the complexity. [0008] There remains a need for materials exhibiting improved strength, hardness, thermal shock resistance, oxidation resistance and fracture toughness, as compared to presently known materials, for use in high temperature applications and/or harsh chemical environments. SUMMARY OF THE INVENTION [0009] The present invention relates to structures that utilize fibrous monolith ("FM") composites to provide the structures with excellent thermal shock resistance, excellent erosion and oxidation/corrosion resistance, enhanced thermal cycling tolerance, enhanced strength at elevated temperatures, and graceful, non-catastrophic failure at room and elevated temperatures. The present invention also relates to methods of preparing such composites and structures. [0010] The composites of the present invention may be used as coatings or external surface component materials in combination with existing structures or with particular substrate structures to impart the benefits of the composites to the structures. Additionally, a more substantial portion of, or even a complete, structure may be formed from the FM composites. [0011] Applications for the fibrous monolith composite materials of the present invention include use in structures such as flat plates, solid hot gas containment tubes, radiant burner tubes, radiant burner panels, rocket nozzles, body armor panels, X-ray targets for CT scanner X-ray tubes, high temperature furnace equipment, antimatter containment vessels, furnace furniture, solar-thermal-propulsion components, internal combustion engine components, turbine engine, turbomachinery components and steering vanes for vectored thrust control, which can all be readily formed from the green material. BRIEF DESCRIPTION OF THE DRAWINGS [0012] FIG. 1 is a perspective cross-sectional view of a uniaxial fibrous monolith composite in accordance with the present invention; [0013] FIG. 2 is a graphical illustration of flexural stress as a function of displacement for a fibrous monolith composite in accordance with the present invention; [0014] FIG. 3 is a schematic flow diagram showing a process of preparing filaments in accordance with the present invention; [0015] FIG. 4 is a photomicrograph of an axial cross-section of an FM composite in accordance with the present invention; [0016] FIG. 5 is a photograph showing preparation of a structure using green fibrous monolith filaments in accordance with the present invention; [0017] FIG. 6 is a schematic illustration of an X-ray target including a FM composite in accordance with the present invention; and [0018] FIG. 7 is a photomicrograph of an axial cross-section of a second FM composite in accordance with the present invention. DETAILED DESCRIPTION OF THE INVENTION [0019] The present invention is directed to the application of FM composites in high temperature and/or harsh chemical environments and to methods of preparing FM composites and structures for use in such environments. The FM composites exhibit mechanical properties including excellent thermal shock resistance, excellent erosion and oxidation/corrosion resistance, enhanced thermal cycling tolerance, enhanced strength at elevated temperatures, and graceful, non-catastrophic failure at room and elevated temperatures. More particularly, the structures of the present invention include fibrous monolithic ceramic and/or metallic composites that include a plurality of filaments having a core surrounded by a shell. The composites may be formed into structures and/or provided as a coating for or layered onto a surface of structures subject to high temperature and/or harsh environments to impart the desired characteristics to the structure. 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