Characterization of Porous Cellular Materials Fabricated by Chemical Vapor Deposition

Abstract

AbstractThe flexibility of chemical vapor deposition (CVD) permits the fabrication of a large number of materials in various geometric forms, one of which is the porous cellular structure. CVD fabrication of such a structure begins with the pyrolysis of a resin-impregnated thermosetting foam to obtain a reticulated carbon foam skeleton. The foam ligaments can then be coated with a variety of materials (metals, oxides, nitrides, carbides, borides, silicides, etc.), either singly or as hybrid, layered, alloyed, or graded structures. During this process, 10 to 1000 microns of the desired material(s) are deposited onto the foam ligaments by a variation of CVD known as chemical vapor infiltration (CVI). The thermomechanical properties of the resultant structure are dominated by the properties of the deposit, becoming independent of the carbon properties at very small material loadings. With precise control over the variables available, it is possible to obtain the simultaneous optimization of stiffness, strength, thermal conductivity, overall weight, and environmental resistance. This paper discusses the fabrication and properties of various CVD foam materials investigated to date.