Abstract: An article comprises a silicon based substrate, a bond layer and a protective top layer. The top layer is selected from the group consisting of rare earth disilicates, yttrium disilicates, rare earth monosilicates, yttrium monosilicates, silica and mixtures thereof. The protective layer described above is used in combination with a bond layer provided between the protective layer and the silicon based substrate which functions as oxygen getter and includes an oxygen gettering agent. By oxygen gettering agent is meant a refractory metal oxide former which forms an oxide at operational condition of (high temperature and aqueous environment) having a melting point of greater than 1500° C. wherein the negative free energy of formation of the refractory metal oxide from the refractory metal is more than 100 Kcal/mole. Suitable oxygen gettering agents include silicon and other refractory metals. An oxygen gettering agent may also be added to the protective layer.

Abstract: The present invention is a low density hybrid airfoil comprising a temperature resistant exterior layer and a tough, high impact resistant interior layer. Specifically, the airfoil comprises a monolithic ceramic exterior layer and a fiber reinforced ceramic matrix composite interior layer. Both the monolithic ceramic and fiber reinforced ceramic matrix composite are low density materials. Additionally, the monolithic ceramic is a high temperature resistant material, and the fiber reinforced ceramic matrix composite is a relatively high impact resistant structure. Encapsulating the airfoil with a temperature resistant exterior layer protects the airfoil in a high temperature environment, and supporting the airfoil with a high impact resistant, fiber reinforced ceramic matrix composite improves the overall impact resistance of the airfoil thereby resulting in a tough, high temperature resistant, low density airfoil.

Abstract: A barrier layer for a silicon containing substrate which inhibits the formation of gaseous species of silicon when exposed to a high temperature aqueous environment comprises a barium-strontium aluminosilicate includes an aluminosilicate of Group IIA and/or Group IIIB and a Group VB oxide.

Abstract: A barrier layer for a silicon containing substrate which inhibits the formation of gaseous species of silicon when exposed to a high temperature aqueous environment comprises a barium-strontium aluminosilicate includes an aluminosilicate of Group IIA and/or Group IIIB and a Group VB oxide.

Abstract: The present invention is a low density hybrid airfoil comprising a temperature resistant exterior layer and a tough, high impact resistant interior layer. Specifically, the airfoil comprises a monolithic ceramic exterior layer and a fiber reinforced ceramic matrix composite interior layer. Both the monolithic ceramic and fiber reinforced ceramic matrix composite are low density materials. Additionally, the monolithic ceramic is a high temperature resistant material, and the fiber reinforced ceramic matrix composite is a relatively high impact resistant structure. Encapsulating the airfoil with a temperature resistant exterior layer protects the airfoil in a high temperature environment, and supporting the airfoil with a high impact resistant, fiber reinforced ceramic matrix composite improves the overall impact resistance of the airfoil thereby resulting in a tough, high temperature resistant, low density airfoil.

Abstract: The present invention is a low density hybrid airfoil comprising a temperature resistant exterior layer and a tough, high impact resistant interior layer. Specifically, the airfoil comprises a monolithic ceramic exterior layer and a fiber reinforced ceramic matrix composite interior layer. Both the monolithic ceramic and fiber reinforced ceramic matrix composite are low density materials. Additionally, the monolithic ceramic is a high temperature resistant material, and the fiber reinforced ceramic matrix composite is a relatively high impact resistant structure. Encapsulating the airfoil with a temperature resistant exterior layer protects the airfoil in a high temperature environment, and supporting the airfoil with a high impact resistant, fiber reinforced ceramic matrix composite improves the overall impact resistance of the airfoil thereby resulting in a tough, high temperature resistant, low density airfoil.

Abstract: An erosion resistant ceramic component is synthesized from a silicon oxynitride precursor powder with a sintering aide. The sintering aide, preferably aluminum oxide and/or lutetium oxide are added to the silicon oxynitride precursor powder and ball milled. The composition is then decanted, dried and granulated. The composition is then formed into the shape of the desired component by hot pressing in a graphite die. A heat treatment process may also be applied after hot pressing to further improve erosion resistance by crystallizing amorphous grain boundary phases to provide a ceramic component having sand erosion characteristics superior to electro-formed nickel. The component provides a dielectric constant which is much lower than the dielectric constant of an electro-formed nickel component.

Abstract: A method for rapidly forming a cast tool adapted for plastic molding includes preparing a uniform mixture of a castable material. A pattern is provided for a desired object to be formed by molding. The castable mixture is applied to the pattern. A continuous structure is cast within the castable material. The castable material is then cured to form a tool.

Abstract: A heat exchanger for use as a condensing heat exchanger in a gas-fired hot air furnace has a ceramic pipe forming an initial portion of a fluid flow path through the heat exchanger. The ceramic pipe receives the combustion gases from a primary heat exchanger and reduces the temperature of the combustion gases to below a certain temperature. A polymer-based structure is connected to the ceramic pipe and forms the remaining portion of the fluid flow path through the heat exchanger. The geometry and orientation of the ceramic pipe is selected so that the certain temperature of the combustion gases exiting the ceramic pipe is less than the softening temperature of the polymer-based structure. The resultant heat exchanger combines the high temperature and corrosion resistance of ceramic materials with the low cost and high corrosion resistance of polymer materials.

Abstract: An engineered ceramic component for the leading edge of a rotor blade provides enhanced erosion protection therefor. In one embodiment, the engineered ceramic component includes a strain isolator member, an aerodynamic ceramic member, a first adhesive bond layer, and a second adhesive bond layer. The strain isolator member, which is operative to minimize strain transfer between the rotor blade infrastructure and the aerodynamic ceramic member, is configured so that inner mold line surface thereof is complementary to outer mold line surface of the rotor blade infrastructure. The aerodynamic ceramic member, which is operative to provide enhanced erosion protection for the respective leading edge of the rotor blade, is configured so that the outer mold line surface thereof defines the aerodynamic configuration of the respective leading edge and the inner mold line surface is complementary to the outer mold line surface of the strain isolator member.

Abstract: A method of joining adjacent, non-coplanar, fiber reinforced composite structures includes machining a plurality of serrations (4) into an edge (6) of a consolidated first fiber reinforced composite structure (2) such that reinforcing fibers continue from a main body (14) of the first fiber reinforced composite structure (2) into the serrations (4). One or more reinforcing fiber plies (16) are then laid up around the serrations (4) to form an unconsolidated second structure such that the serrations (4) protrude through at least one reinforcing fiber ply (16). In addition to the one or more reinforcing fiber plies (16), the unconsolidated second structure also includes a matrix precursor. Sufficient heat and pressure are applied to the unconsolidated second structure and the serrations (4) to consolidate the second structure into a fiber reinforced composite structure (8).

Abstract: A method of joining adjacent, non-coplanar, fiber reinforced composite structures includes machining a plurality of serrations (4) into an edge (6) of a consolidated first fiber reinforced composite structure (2) such that reinforcing fibers continue from a main body (14) of the first fiber reinforced composite structure (2) into the serrations (4). One or more reinforcing fiber plies (16) are then laid up around the serrations (4) to form an unconsolidated second structure such that the serrations (4) protrude through at least one reinforcing fiber ply (16). In addition to the one or more reinforcing fiber plies (16), the unconsolidated second structure also includes a matrix precursor. Sufficient heat and pressure are applied to the unconsolidated second structure and the serrations (4) to consolidate the second structure into a fiber reinforced composite structure (8).

Abstract: A heating unit (14) includes a flame holder (2) that has a plurality of randomly distributed pores and comprises at least about 50 wt % ceramic particles that have an emissivity of at least about 0.7. The heating unit (14) also has means for conveying a fuel/air mixture to the flame holder (2), means (18) for igniting the fuel/air mixture so it forms a flame in proximity to the flame holder, means (20) for transferring heat from the flame to a heat transfer medium, and means (26) for exhausting combustion products from the heating unit. A fuel/air mixture may be directed through the flame holder (2) and burned to form a flame in proximity to the flame holder such that the flame and flame holder interact to produce emissions of less than about 10 ng/J NO.sub.x.