摘要:
This invention relates to a method for producing a self-supporting ceramic structure comprising an oxidation reaction product of a parent metal and a vapor-phase oxidant characterized by an altered microstructure attributable to the addition of one or more process modifiers relative to substantially the same oxidation reaction product produced without a process modifier.
摘要:
Organometallic ceramic precursor binders are used to fabricate shaped bodies by different techniques. Exemplary shape making techniques which utilize hardenable, liquid, organometallic, ceramic precursor binders include the fabrication of negatives of parts to be made (e.g., sand molds and sand cores for metalcasting, etc.), as well as utilizing ceramic precursor binders to make shapes directly (e.g., brake shoes, brake pads, clutch parts, grinding wheels, polymer concrete, refractory patches and liners, etc.). A preferred embodiment of the invention involves the fabrication of preforms used in the formation of composite articles.
摘要:
This invention relates to a self-supporting ceramic strucutre comprising an oxidation reaction product of a parent metal and a vapor-phase oxidant characterized by an altered microstructure attributable to the addition of one or more process modifiers relative to substantially the same oxidation reaction product produced without a process modifier.
摘要:
Composite bodies made by a silicon metal infiltration process that feature a silicon intermetallic, e.g., a metal silicide. Not only does this give the composite material engineer greater flexibility in designing or tailoring the physical properties of the resulting composite material, but the infiltrant also can be engineered compositionally to have much diminished amounts of expansion upon solidification, thereby enhancing net-shape-making capabilities. These and other consequences of engineering the metal component of composite bodies made by silicon infiltration permit the fabrication of large structures of complex shape.
摘要:
A composite body produced by a reactive infiltration process that possesses high mechanical strength, high hardness and high stiffness has applications in such diverse industries as precision equipment and ballistic armor. Specifically, the composite material features a boron carbide filler or reinforcement phase, and a silicon carbide matrix produced by the reactive infiltration of an infiltrant having a silicon component with a porous mass having a carbonaceous component. Potential deleterious reaction of the boron carbide with silicon during infiltration is suppressed by alloying or dissolving boron into the silicon prior to contact of the silicon infiltrant with the boron carbide. In a preferred embodiment of the invention related specifically to armor, good ballistic performance can be advanced by loading the porous mass or preform to be infiltrated to a high degree with one or more hard fillers such as boron carbide, and by limiting the size of the largest particles making up the mass. The instant reaction-bonded silicon carbide (RBSC) composite bodies surpass previous RBSC's as armor materials, and in this capacity approach the ballistic performance of current carbide armor ceramics but with potentially lower cost manufacturing methods, e.g., infiltration techniques.
摘要:
Techniques to bond two or more smaller bodies or subunits to produce a unitary SiC composite structure extend the capabilities of reaction-bonded silicon carbide, for example, by making possible the fabrication of complex shapes. In a first aspect of the present invention, two or more preforms are bonded together with a binder material that imparts at least strength sufficient for handling during subsequent thermal processing. In a second aspect of the present invention, instead of providing the subunits to be bonded in the form of preforms, the subunits may be dense, SiC composite bodies, e.g., RBSC bodies. In each of the above embodiments, a preferable means for bonding two or more subunits combines aspects of adhesive and mechanical locking characteristics. One way to accomplish this objective is to incorporate a mechanical locking feature to the joining means, e.g., a “keyway” feature. The mechanical locking feature thus substitutes for, or supplements the binder qualities of the adhesive, which is especially important when the adhesive itself may be or become weak due to, for example, thermal processing.
摘要:
Current top performing SAPI systems are B4C-containing (hot pressed B4C or reaction bonded B4C). These systems will not function well versus future WC/Co threats due to the inability of B4C to withstand high pressure impacts. New approaches will be needed for next generation SAPI ceramics. Three related concepts are disclosed herein, each of which will lead to improved reaction bonded ceramics for next generation SAPI applications. The first concept aims to reactively heat treat reaction bonded B4C, causing. SiC and SiB6 to form at the expense of B4C. The second approach will add Ti to the system, thus allowing TiC and TiB2 to form at the expense of B4C. Finally, the third concept will evaluate the use of finer particle sizes, thus improving the static properties of the ceramics (with the aim of enhancing multi-hit performance). In all cases, preliminary work has been conducted to demonstrate the viability of the concepts. This will lead to a new family of advanced armor ceramics. These new armor ceramics will allow the modern soldier to be better protected versus next generation, high level threats (e.g., high pressure WC/Co projectiles) with a more ergonomic package (lower weight, less bulk). Further, the results disclosed herein will yield improvement versus the current tool steel threats.
摘要:
Silicon infiltration technology is used to produce ceramic bodies having utility as ballistic armor. In a first aspect of the invention, the ballistic armor includes a reaction-bonded silicon carbide body (RBSC). Good ballistic performance can be advanced by loading the permeable mass or preform to be infiltrated to a high degree with one or more hard fillers, and by limiting the size of the largest particles making up the mass. In a second aspect, the silicon infiltration technology, e.g., siliconizing or reaction-bonding, is used to bond silicon carbide fibers to at least the back surface of a ceramic armor body, thereby enhancing ballistic stopping power. A third aspect of the invention pertains to the ability to engineer RBSC bodies such that there is little dimensional change during processing, thereby permitting high dimensional reproducibility in large-scale production.
摘要:
Improved silicon carbide composites made by an infiltration process feature a metal phase in addition to any residual silicon phase. Not only are properties such as mechanical toughness improved, but the infiltrant can be so engineered as to have much diminished amounts of expansion upon solidification, thereby enhancing net-shape-making capabilities. Further, multi-component infiltrant materials may have a lower liquidus temperature than pure silicon, thereby providing the practitioner greater control over the infiltration process. In particular, the infiltration may be conducted at the lower temperatures, where low-cost but effective bedding or barrier materials can terminate the infiltration process once the infiltrant has migrated through the permeable mass up to the boundary between the mass and the bedding material.
摘要:
Improved silicon carbide composites made by an infiltration process feature a metal phase in addition to any residual silicon phase. Not only are properties such as mechanical toughness improved, but the infiltrant can be so engineered as to have much diminished amounts of expansion upon solidification, thereby enhancing net-shape-making capabilities. Further, multi-component infiltrant materials may have a lower liquidus temperature than pure silicon, thereby providing the practitioner greater control over the infiltration process. In particular, the infiltration may be conducted at the lower temperatures, where low-cost but effective bedding or barrier materials can terminate the infiltration process once the infiltrant has migrated through the permeable mass up to the boundary between the mass and the bedding material.