Refractory foams are a new class of open cell, low density materials which Ultramet has developed to produce lightweight refractory structures for a variety of aerospace and industrial applications including thermal insulation, lightweight, precision mirrors, impact absorption, catalyst support, and metal and gas filtration. By pyrolyzing a polymer foam, a reticulated vitreous carbon (RVC) foam is created which has substantial mechanical and thermal properties. By further CVI processing, ceramic (e.g. silicon carbide [SiC]) and/or metal or mixed material foams can be fabricated.
These cellular materials can be simultaneously optimized for stiffness, strength, thermal conductivity, active surface area, and gas permeability. They are thermally stable, low in weight and density, chemically pure, resistant to thermal stress and shock, and are relatively inexpensive.
Refractory foams can be fabricated from any material or materials combination (either homogeneously combined or layered) which can be deposited by CVD/CVI. Among the materials that can be deposited are the refactory metals (e.g. niobium, tantalum, tungsten, rhenium) and their ceramic compounds (e.g. the oxides, nitrides, carbides, borides, and silicides). Deposited material densities of up to 50% of theoretical values can be readily achieved. These materials can be furnished in various sizes and configurations, and are easy to machine. Face sheets of either the same of different material can be applied to enhance the flexural and tensile properties.