HoneySiC: a new optomechanical material for low-areal cost and density

摘要

One of the major problems perceived for deposited silicon carbide mirrors and structures is the cost associated with machining and lightweighting the material to the specifications of a drawing. Molded pedigrees of silicon carbide address these concerns by casting or molding a slurry and prefiring the slurry to make a consolidated and porous greenbody which is relatively soft and not very difficult to machine. The machined greenbody is then infiltrated with molten silicon in an exothermic process that yields a two phase reaction bonded silicon carbide material that must undergo a final machining step. Converted silicon carbide pedigrees machine a graphite or carbon/carbon precursor material to near net shape and then infiltrate the part with gaseous silicon monoxide or molten silicon to convert most or all of the carbon to silicon carbide. Some pedigrees are highly porous, while others may be dense and containing 2 or 3 different phases of material. We have created and demonstrated a new fiber reinforced silicon carbide material that combines the benefits of molding, infiltration and conversion processes. The resulting HoneySiC material requires a minimal amount of machining. HoneySiC material achieves lightweighting of 92% relative to bulk material and net production cost on the order of $38K per square meter (unpolished), less than half of NASA's goal of $100K per square meter.