Abstract: A functionally graded carbide body (400) can include a group 5 metal carbide substrate having a bulk composition region (410) that contains at least 70 wt % of a rhombohedral ?-phase carbide. A ?-phase-rich region (420) having a ?-phase-rich composition can be at a surface (430) of the substrate, and a phase composition gradient region (440) can transition from the ?-phase-rich composition region at the surface to the bulk composition region at a gradient depth (450) below the surface.

Abstract: A functionally graded carbide body (400) can include a group 5 metal carbide substrate having a bulk composition region (410) that contains at least 70 wt % of a rhombohedral ?-phase carbide. A ?-phase-rich region (420) having a ?-phase-rich composition can be at a surface (430) of the substrate, and a phase composition gradient region (440) can transition from the ?-phase-rich composition region at the surface to the bulk composition region at a gradient depth (450) below the surface.

Abstract: A method of forming a sintered ?-phase tantalum carbide can include assembling a particulate mixture including a tantalum hydride powder and a carbon source powder. The particulate mixture can be sintered to form a tantalum carbide having at least 70 wt. % of a ?-phase with at least about 90% densification. After sintering, the tantalum carbide can be cooled to substantially retain the ?-phase.

Abstract: A method of forming a sintered ?-phase tantalum carbide can include assembling a particulate mixture including a tantalum hydride powder and a carbon source powder. The particulate mixture can be sintered to form a tantalum carbide having at least 70 wt. % of a ?-phase with at least about 90% densification. After sintering, the tantalum carbide can be cooled to substantially retain the ?-phase.

Abstract: A ceramic material having a high toughness can include carbon and a transition metal. The transition metal can have an elemental body centered cubic structure at room temperature. A substantial amount of the ceramic can be of a rhombohedral ? phase of the transition metal and carbon. These materials can have a high thermal shock resistance, high fracture toughness, and good high temperature performance. A particulate mixture of a carbon source and a transition metal source can be assembled (12) and reacted (14) under high pressure and high temperature. The transition metal source can include a transition metal of a metal which has an elemental BCC structure at room temperature. The particulate mixture carbon to transition metal ratio is chosen so as to achieve a zeta phase carbide and processing is affected in order to retain the zeta phase at a substantial weight percent of the material (i.e. greater than about 5 wt %).

Abstract: A ceramic material having a high toughness can include carbon and a transition metal. The transition metal can have an elemental body centered cubic structure at room temperature. A substantial amount of the ceramic can be of a rhombohedral ? phase of the transition metal and carbon. These materials can have a high thermal shock resistance, high fracture toughness, and good high temperature performance. A particulate mixture of a carbon source and a transition metal source can be assembled (12) and reacted (14) under high pressure and high temperature. The transition metal source can include a transition metal of a metal which has an elemental BCC structure at room temperature. The particulate mixture carbon to transition metal ratio is chosen so as to achieve a zeta phase carbide and processing is affected in order to retain the zeta phase at a substantial weight percent of the material (i.e. greater than about 5 wt %).

Abstract: A method of joining at least two sintered bodies to form a composite structure, includes: providing a joint material between joining surfaces of first and second sintered bodies; applying pressure from 1 kP to less than 5 MPa to provide an assembly; heating the assembly to a conforming temperature sufficient to allow the joint material to conform to the joining surfaces; and further heating the assembly to a joining temperature below a minimum sintering temperature of the first and second sintered bodies. The joint material includes organic component(s) and ceramic particles. The ceramic particles constitute 40-75 vol. % of the joint material, and include at least one element of the first and/or second sintered bodies. Composite structures produced by the method are also disclosed.

Abstract: Method of making an electrochemical device for the recovery of oxygen from an oxygen-containing feed gas comprising (a) preparing a green electrochemical device by assembling a green electrolyte layer, a green anode layer in contact with the green electrolyte layer, a green cathode layer in contact with the green electrolyte layer, a green anode-side gas collection interconnect layer in contact with the green anode layer, and a green cathode-side feed gas distribution interconnect layer in contact with the green cathode layer; and (b) sintering-the green electrochemical device by heating to yield a sintered electrochemical device comprising a plurality of sintered layers including a sintered anode-side gas collection interconnect layer in contact with the anode layer and adapted to collect oxygen permeate gas, wherein each sintered layer is bonded to an adjacent sintered layer during sintering.

Abstract: A binderless coarse-grained WC substrate is coated with a chemical vapor deposition ("CVD") diamond layer in order to give a coating with improved adherence relative to WC--Co-based substrates and high compressive residual stress relative to Si.sub.3 N.sub.4 -based substrates. The elimination of Co from the WC improves the adherence of the diamond coating, allowing thicker coatings to be produced than for WC--Co substrates. Thin coatings (<30 .mu.m) are acceptable for applications where the coating is under low applied stress. Thicker coatings (>30 .mu.m) are used to give enhanced damage resistance for stresses localized at the surface of the diamond-coated component. Applying the diamond coating to a WC/WC--Al.sub.2 O.sub.3 /WC graded composite allows materials with high damage resistance to be fabricated. Deposition of a substantially continuous diamond film may be accomplished by CVD and PVD techniques.

Abstract: A ceramic comprising a matrix of Al.sub.2 O.sub.3, ZrO.sub.2 (partially or fully stabilized) or mixtures of Al.sub.2 O.sub.3 and ZrO.sub.2 with strontium aluminate plate-shaped grains distributed throughout the matrix results in a ceramic with high toughness, high strength and good hardness. SrO/Al.sub.2 O.sub.3 molar ratios between 0.02 and 0.20 result in in-situ formation of plate-shaped grains approximately 0.5 .mu.m in thickness and 5.0 .mu.m in breadth in tetragonal zirconia polycrystalline ceramic matrices. The in-situ formation of strontium aluminates allows high volume loading of platelets to occur and high toughness is achieved without the loss of strength. High alumina compositions have the added benefit of higher strength, lower thermal expansion, higher modulus and higher thermal conductivity than zirconia ceramics with comparable toughness.

Abstract: High surface area, submicron ceramic powders are synthesized by reducing an oxide in the presence of another metal (i.e., Mg, Al, Ca, and the like) and a source of carbon, nitrogen or boron to form a new oxide and a carbide, nitride (or carbonitride). or boride. The oxide phase can be leached out to leave submicron carbides, nitrides or borides. Alternatively milling of reacted powders allows intimate mixtures of uniform, fine grained ceramic powders to be prepared inexpensively. These multiple-phase composite powders can be formed into a body and densified using conventional techniques to form dense, fine-grained ceramic bodies. Alternatively, containment of unreacted powders and subsequent heating results in multiple-phase dense ceramics with unique microstures. Transformation toughening of composites is possible by adding zirconia or hafnia either before or after the powder synthesis step.

Abstract: A tungsten carbide ceramic material which cuts titanium alloys four to five times faster than cemented carbide, ceramic-coated cemented carbides, or state-of-the-art ceramic cutting tools can be densified with or without applied pressure at temperatures below 1700.degree. C. Grain growth inhibitors or sintering aids can be added to control grain size in the final product. The polycrystalline tungsten carbode ceramic can be formed into wear components having improved performance in comparison to cemented tungsten carbides in a variety of drilling, cutting, milling, and other wear applications.

Abstract: Liquid phase sintering is used to densify silicon carbide based ceramics using a compound comprising a rare earth oxide and aluminum oxide to form liquids at temperatures in excess of 1600.degree. C. The resulting sintered ceramic body has a density greater than 95% of its theoretical density and hardness in excess of 23 GPa. Boron and carbon are not needed to promote densification and silicon carbide powder with an average particle size of greater than one micron can be densified via the liquid phase process. The sintered ceramic bodies made by the present invention are fine grained and have secondary phases resulting from the liquid phase.

Abstract: Hollow, fine-grained ceramic proppants are less expensive and improve fracture control when compared to conventional proppants (dense alumina, mullite, bauxite, zirconia, etc.). Hollow proppants of the present invention have been fabricated by spray drying, followed by sintering in order to obtain a dense case and a hollow core. These proppants generally have high sphericity and roundness (Krumbein sphericity and roundness greater than 0.8), have diameters on average between 2250 and 125 .mu.m, depending on proppant size required, and have strength equal to or greater than that of sand. The hollow core, the size of which can be controlled, permits better fracture control in hydraulic fracturing treatments since the proppant can be transported in lower viscosity fluids. Hollow proppants produced at the same cost/weight as conventional proppants also provide for lower costs, since less weight is required to fill the same volume. The fine-grained (preferably less than 5 .mu.