A seal system includes a ceramic component that has a non-core-gaspath surface region that defines a first surface roughness and a core gaspath surface region. A metallic component is situated adjacent the non-core-gaspath surface region. A coating system is disposed on the ceramic component. The coating system includes a silicon-containing layer on the non-core-gaspath surface region and a barrier layer that has a first section on the silicon-containing layer and a second section on the core-gaspath region and that is connected to the first section. The surface of the barrier layer has a second surface roughness that is less than the first surface roughness. The first section is in contact with the metallic component and the second section serves as an environmental barrier on the core-gaspath region.

Methods of forming a metallic-ceramic brazed joint are disclosed herein. The method of forming the brazed joint includes deoxidizing the surface of metallic components, assembling the joint, heating the joint to fuse the joint components, and cooling the joint. In certain embodiments, the brazed joint includes a conformal layer. In further embodiments, the brazed joint has features in order to reduce stress concentrations within the joint.

A dielectric ceramic composition including a first component and a second component. The first component comprises an oxide of Ca of 0.00 mol % to 35.85 mol % an oxide of Sr of 0.00 mol % to 47.12 mol %, an oxide of Ba of 0.00 mol % to 51.22 mol %, an oxide of Ti of 0.00 mol % to 17.36 mol %, an oxide of Zr of 0.00 mol % to 17.36 mol %, an oxide of Sn of 0.00 mol % to 2.60 mol %, an oxide of Nb of 0.00 mol % to 35.32 mol %, an oxide of Ta of 0.00 mol % to 35.32 mol %, and an oxide of V of 0.00 mol % to 2.65 mol %. The second component includes (by mass) at least (a) an oxide of Mn of 0.005% to 3.500% and (b) one or both of an oxide of Cu of 0.080% to 20.000% and an oxide of Ru of 0.300% to 45.000%.

A composite fiber composed of at least a metal sintered body and a ceramic sintered body. In the composite fiber, the metal sintered body and the ceramic sintered body are adjacent to each other. The composite fiber having the metal sintered body and the ceramic sintered body can have a tensile strength of 5 kgf/mm.sup.2 or more.

A seal system includes a ceramic component, a metallic component, a silicon-containing layer, and a barrier layer. The ceramic component has a first surface region that defines a first surface roughness. The metallic component is situated adjacent to the first surface region and has a second surface region facing the first surface region. The silicon-containing layer is on the first surface region of the ceramic component and has a contact surface that defines a second surface roughness which is less than the first surface roughness. The barrier layer is on the metallic component and in contact with the silicon-containing layer and serves to limit interaction between silicon of the silicon-containing layer and the metallic component. The barrier layer includes at least one of alumina or MCrAlY.

A seal system includes a ceramic component, a metallic component, a coating system. The ceramic component has a first surface region that defines a first surface roughness. The metallic component is situated adjacent to the first surface region and has a second surface region facing the first surface region. The coating system includes a silicon-containing layer on the surface region of the ceramic component and barrier layer on the silicon-containing layer. The silicon containing layer has a surface in contact with the barrier layer and the barrier layer has a surface in contact with the metallic component. The surface of the barrier layer has a second surface roughness that is less than the first surface roughness. The barrier layer serves to limit interaction between silicon of the silicon-containing layer and elements of the metallic component. The barrier layer includes at least one of mullite, zircon, or hafnon.

Methods of forming joinery between components formed from dissimilar materials, and assemblies utilizing the joinery. The components include interface surfaces having complementary peaks and valleys that interlock. A compliant interface is formed between the interface surfaces and the interface can be configured to provide functionality.

An electrode can include a functional layer having an Ln.sub.2MO.sub.4 phase, where Ln is at least one lanthanide optionally doped with a metal and M is at least one 3d transition metal, and a heavily-doped ceria phase. An electrochemical device or a sensor device can include the electrode.

A seal system includes a ceramic component, a metallic component, a silicon-containing layer, and a barrier layer. The ceramic component has a first surface region that defines a first surface roughness. The metallic component is situated adjacent to the first surface region and has a second surface region facing the first surface region. The silicon-containing layer is on the first surface region of the ceramic component and has a contact surface that defines a second surface roughness which is less than the first surface roughness. The barrier layer is on the metallic component and in contact with the silicon-containing layer and serves to limit interaction between silicon of the silicon-containing layer and the metallic component. The barrier layer includes at least one of alumina or MCrAlY.

An electrochemical cell is described, including an anodic chamber and a cathodic chamber separated by an electrolyte separator tube, all contained within a cell case. The cell also includes an electrically insulating ceramic collar positioned at an opening of the cathodic chamber, and defining an aperture in communication with the opening; along with a cathode current collector assembly; and at least one metallic ring that has a coefficient of thermal expansion (CTE) in the range of about 3 to about 7.5 ppm/° C., contacting at least a portion of a metallic component within the cell, and an adjacent ceramic component. An active braze alloy composition attaches and hermetically seals the ring to the metallic component and the collar. Sodium metal halide batteries that contain this type of cell are also described, along with methods for sealing structures within the cell.