摘要:
A low CTE metal-ceramic composite material featuring carbon fibers reinforcing a matrix featuring silicon metal or silicon alloy. The fibers have a low coefficient of thermal expansion (CTE) in the axial direction, and preferably negative. The principles of making Si/SiC composites can be adapted to produce the instant Si matrix composites. The CTE of the composite body depends not only upon the relative CTE's of the fibers and matrix, and their relative amounts (e.g., loadings), but also upon the relative elastic moduli of the fibers and matrix. Thus, Si/SiC matrices produced by a reaction-bonding process inherently possess low CTE, but the instant inventors prefer to make such composites having relatively large fractions of unreacted silicon, thereby driving composite CTE lower still. Here, the carbon fibers are protected from reaction with the silicon infiltrant with one or more materials disposed between the fibers and the infiltrant. Providing at least a degree of toughness or impact resistance can also be realized in these composites. Laminates produce Isotropic or quasi-isotropic properties in the composite body can be realized by, for example, providing the fibers in the form of cross-plied laminates featuring the fibers in parallel or woven arrays.
摘要:
A mirror having low density, low CTE, high thermal conductivity, high elastic modulus, and a reflective, polishable surface. The instant mirror features a silicon-based metal coating as the reflective surface, and a composite body as a support or substrate for the reflecting surface. The composite body features carbon fibers reinforcing a matrix containing silicon metal and optionally some silicon carbide. The metal coating can be elemental silicon metal, possibly in amorphous form, and can be applied by a vapor deposition process such as chemical vapor deposition (e.g., plasma enhanced CVD) or physical vapor deposition such as evaporation or electron beam PVD.
摘要:
A ceramic-containing armor tile exhibiting anisotropy exhibits different anti-ballistic performance compared to a uniform, isotropic tile. The ballistic performance has been quantified, and the results suggest that design can be optimized for even greater performance.
摘要:
Ceramic-containing bodies can be bonded to other ceramic-containing bodies, or to metals or metal-containing bodies, by way of an aluminum-silicon brazing alloy. Such alloys feature high thermal conductivity and a melting range intermediate to Cu—Sil and Au—Si. By depositing a layer of silicon or aluminum, e.g., by vapor deposition, onto a surface of the ceramic-containing body, the formation of deleterious intermetallic phases at the brazing interface is avoided. This technique is particularly useful for joining reaction-bonded silicon carbide (RBSC) composite bodies, and particularly such composite bodies that contain appreciable amounts of aluminum as a metallurgical modification of the residual silicon phase. When the RBSC body contains minor amounts of the aluminum alloying constituent, or none, the metallization layer is not required. The resulting bonded structures have utility as mirrors, as packaging for electronics, and in semiconductor lithography equipment, e.g., as electrostatic chucks for supporting a silicon wafer during the lithography process.
摘要:
A diamond-reinforced SiC ceramic composite material and shaped article. The addition of diamond to the microstructure greatly enhances properties such as hardness and Young's modulus. Such a composite material has considerable promise as an armor material. In particular, significant increases in ballistic performance can be achieved versus a non-diamond-containing composite, particularly versus the M993 threat. Reaction bonded silicon carbide (RBSC) ceramics with 7% diamond were shown to offer ballistic performance levels that matched the best commercial ceramics tested on the program.