Abstract: Pressureless sintering of silicon carbide with fracture toughness in excess of about 4 MPa-m1/2 as measured by the single-edge precracked beam (SEPB) technique while maintaining a density greater than 3.1 g/cc for compositions with SiC greater than about 94 wt. % is made possible through the use of metallic Al to promote sintering and grain growth. Boron and carbon may be used as traditional sintering aids, with nitrogen to suppress grain growth, and additions of yttrium and/or lanthanide elements to promote intergranular fracture.

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: A gas sensor may include a sintered heating component which includes a ceramic insulating material, and a separately sintered sensing component which includes an ionically conductive material. The sensor may also include a bond attaching the sensing component to the heating component. The bond may be made of bonding material which is different from the insulating material and the ionically conductive material.

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: Pressureless sintering of silicon carbide with fracture toughness in excess of about 4 MPa-m1/2 as measured by the single-edge precracked beam (SEPB) technique while maintaining a density greater than 3.1 g/cc for compositions with SiC greater than about 94 wt. % is made possible through the use of metallic Al to promote sintering and grain growth. Boron and carbon may be used as traditional sintering aids, with nitrogen to suppress grain growth, and additions of yttrium and/or lanthanide elements to promote intergranular fracture.

Abstract: A method of joining at least two sintered bodies to form a composite structure, including providing a first multicomponent metallic oxide having a perovskitic or fluorite crystal structure; providing a second sintered body including a second multicomponent metallic oxide having a crystal structure of the same type as the first; and providing at an interface a joint material containing at least one metal oxide containing at least one metal identically contained in at least one of the first and second multicomponent metallic oxides. The joint material is free of cations of Si, Ge, Sn, Pb, P and Te and has a melting point below the sintering temperatures of both sintered bodies. The joint material is heated to a temperature above the melting point of the metal oxide(s) and below the sintering temperatures of the sintered bodies to form the joint. Structures containing such joints are also disclosed.

Abstract: A method of forming a composite structure includes: (1) providing first and second sintered bodies containing first and second multicomponent metallic oxides having first and second identical crystal structures that are perovskitic or fluoritic; (2) providing a joint material containing at least one metal oxide: (a) containing (i) at least one metal of an identical IUPAC Group as at least one sintered body metal in one of the multicomponent metallic oxides, (ii) a first row D-Block transition metal not contained in the multicomponent metallic oxides, and/or (iii) a lanthanide not contained in the multicomponent metallic oxides; (b) free of metals contained in the multicomponent metallic oxides; (c) free of cations of boron, silicon, germanium, tin, lead, arsenic, antimony, phosphorus and tellurium; and (d) having a melting point below the sintering temperatures of the sintered bodies; and (3) heating to a joining temperature above the melting point and below the sintering temperatures.

Abstract: A method of joining at least two sintered bodies to form a composite structure, including providing a first multicomponent metallic oxide having a perovskitic or fluorite crystal structure; providing a second sintered body including a second multicomponent metallic oxide having a crystal structure of the same type as the first; and providing at an interface a joint material containing at least one metal oxide containing at least one metal identically contained in at least one of the first and second multicomponent metallic oxides. The joint material is free of cations of Si, Ge, Sn, Pb, P and Te and has a melting point below the sintering temperatures of both sintered bodies. The joint material is heated to a temperature above the melting point of the metal oxide(s) and below the sintering temperatures of the sintered bodies to form the joint. Structures containing such joints are also disclosed.

Abstract: A method of forming a composite structure includes: (1) providing first and second sintered bodies containing first and second multicomponent metallic oxides having first and second identical crystal structures that are perovskitic or fluoritic; (2) providing a joint material containing at least one metal oxide: (a) containing (i) at least one metal of an identical IUPAC Group as at least one sintered body metal in one of the multicomponent metallic oxides, (ii) a first row D-Block transition metal not contained in the multicomponent metallic oxides, and/or (iii) a lanthanide not contained in the multicomponent metallic oxides; (b) free of metals contained in the multicomponent metallic oxides; (c) free of cations of boron, silicon, germanium, tin, lead, arsenic, antimony, phosphorus and tellurium; and (d) having a melting point below the sintering temperatures of the sintered bodies; and (3) heating to a joining temperature above the melting point and below the sintering temperatures.

Abstract: The present invention relates to compositions of matter represented by the general formula LnxLn′x′AyTizCe1−x−x′−y−zO2−&dgr; wherein Ln is selected from the group consisting of Sm, Gd, Y, Ln′ is selected from the group consisting of La, Pr, Nd, Pm, Eu, Tb, Dy, Ho, Er, Tm, Yb, Lu; A is selected from the group consisting of Mg, Ca, Sr and Ba, 0.05≦x≦0.25, 0≦x′≦0.25, 0≦y≦0.03, 0.001≦z≦0.03, 0.05≦x+x′≦0.25, 0.001≦y+z≦0.03, wherein &dgr; is a number which renders the composition of matter charge neutral. The compositions can be formed into sintered bodies suitable for use as solid electrolytes in devices including solid-state oxygen generators. Such sintered bodies have greater than 95% theoretical density at temperatures at or below 1600° C., and can be produced by a solid-state method.

Abstract: The present invention relates to compositions of matter represented by the general formula

Abstract: This invention presents a new class of multicomponent metallic oxides which are particularly suited toward use in fabricating components used in processes for producing syngas. The non-stoichiometric, A-site rich compositions of the present invention are represented by the formula (LnxCa1−x)y FeO3−&dgr;wherein Ln is La or a mixture of lanthanides comprising La, and wherein 1.0>x>0.5, 1.1≧y>1.0 and &dgr; is a number which renders the composition of matter charge neutral. Solid-state membranes formed from these compositions provide a favorable balance of oxygen permeance and resistance to degradation when employed in processes for producing syngas. This invention also presents a process for making syngas which utilizes such membranes.

Abstract: An electrochemical device for separating oxygen from an oxygen-containing gas comprises a plurality of planar ion-conductive solid electrolyte plates and electrically-conductive gas-impermeable interconnects assembled in a multi-cell stack. Electrically-conductive anode and cathode material is applied to opposite sides of each electrolyte plate. A gas-tight anode seal is bonded between the anode side of each electrolyte plate and the anode side of the adjacent interconnect. A biasing electrode, applied to the anode side of each electrolyte plate between the anode seal and the edge of the anode, eliminates anode seal failure by minimizing the electrical potential across the seal. The seal potential is maintained below about 40 mV and preferably below about 25 mV. A gas-tight seal is applied between the cathode sides of each electrolyte plate and the adjacent interconnect such that the anode and cathode seals are radially offset on opposite sides of the plate.

Abstract: An electrochemical device for separating oxygen from an oxygen-containing gas comprises a plurality of planar ion-conductive solid electrolyte plates and electrically-conductive gas-impermeable interconnects assembled in a multi-cell stack. Electrically-conductive anode and cathode material is applied to opposite sides of each electrolyte plate. A gas-tight anode seal is bonded between the anode side of each electrolyte plate and the anode side of the adjacent interconnect. A biasing electrode, applied to the anode side of each electrolyte plate between the anode seal and the edge of the anode, eliminates anode seal failure by minimizing the electrical potential across the seal. The seal potential is maintained below about 40 mV and preferably below about 25 mV. A gas-tight seal is applied between the cathode sides of each electrolyte plate and the adjacent interconnect such that the anode and cathode seals are radially offset on opposite sides of the plate.

Abstract: Planar solid-state membrane modules for separating oxygen from an oxygen-containing gaseous mixture which provide improved pneumatic and structural integrity and ease of manifolding. The modules are formed from a plurality of planar membrane units, each membrane unit which comprises a channel-free porous support having connected through porosity which is in contact with a contiguous dense mixed conducting oxide layer having no connected through porosity. The dense mixed conducting oxide layer is placed in flow communication with the oxygen-containing gaseous mixture to be separated and the channel-free porous support of each membrane unit is placed in flow communication with one or more manifolds or conduits for discharging oxygen which has been separated from the oxygen-containing gaseous mixture by permeation through the dense mixed conducting oxide layer of each membrane unit and passage into the manifolds or conduits via the channel-free porous support of each membrane unit.