Abstract: A printed circuit board has a base made from fibers (e.g., ceramic) and an inorganic coating (e.g., silicon carbide) covering the fibers to provide the base with inorganic properties. The base may have a particular coefficient of thermal expansion (CTE) as by providing the fibers with particular characteristics in the plane of, and perpendicular to, the base. The base may be isotropic thermally as by disposing the fibers in two adjacent transverse layers. An inorganic material (e.g. copper) on the base provides a radio frequency barrier. An inorganic material (e.g., silicon dioxide) on the RF barrier constitutes a dielectric insulator. An electrically conductive layer (eg. copper) partially covers the dielectric layer in a pattern defining an electrical circuit. A dielectric material (eg., silicon dioxide) fills the remaining space in this layer in a flush relationship with the conductive layer.

Abstract: A fibrous substrate having a first coefficient of thermal expansion and having porous characteristics is formed from discrete elements, such as carbon fibers, having anisotropic properties. A matrix formed from a refractory material encases the discrete elements and has a second coefficient of thermal expansion different from the first coefficient. The matrix has minimal chemical or mechanical bonding to the discrete elements to provide for a displacement of the matrix relative to the substrate with mechanical shock or changes in temperature. The matrix includes a first element having refractory properties and selected from the group consisting of hafnium, zirconium, tantalum, tungsten and molybdenum and also includes a second element bound to the first element. The matrix is preferably formed by providing a mixture of a first gas containing the refractory element and a second gas containing the second element and by introducing the gases into a chamber containing the substrate.

Abstract: A porous substrate is formed from discrete elements preferably anisotropic and permeable to oxygen and preferably having a first coefficient of thermal expansion. A pyrolytic material permeable to oxygen may be deposited in a thin layer on the discrete elements. A barrier material (e.g. boron carbide or silicon carbide) may be deposited in a thin layer on the pyrolytic material to inhibit diffusion of elements into the pyrolytic material. A material impermeable to oxygen (e.g. boron nitride or silicon nitride) may be deposited in a thin layer on the barrier material. A refractory matrix permeable to oxygen may be deposited on the impermeable material. The matrix may include a metallic element (e.g. silicon, hafnium, tantalum or zirconium) and another element (e.g. oxygen, nitrogen, carbon or boron) chemically bonded to the metallic element. The matrix may have a second coefficient of thermal expansion different from the first coefficient and may have a minimal bond to the substrate.

Abstract: A composite structural ceramic article and method of fabrication thereof. The article of the invention is specifically designed for use in high temperature, corrosive and erosive environments such as those found in heat engines, heat exchangers, stationary power equipments and industrial process equipments. The article comprises a porous carbon fibrous substrate or other suitable high temperature fibrous substrate which may include: a pyrolytic carbon or appropriate chemical vapor deposited sheath formed about each fiber of the substrate; a chemically vapor deposited metallic carbide, oxide, boride or nitride coating over the coated fibers of the substrate; and an impermeable metallic carbide, oxide, boride or nitride outer protective layer formed about the entire periphery of the coated substrate.