A method for the joining of ceramic pieces with a hermetically sealed joint comprising brazing a continuous layer of joining material between the two pieces. The wetting and flow of the joining material is controlled by the selection of the joining material, the joining temperature, the time at temperature, the joining atmosphere, and other factors. The ceramic pieces may be aluminum nitride and the pieces may be brazed with an aluminum alloy under controlled atmosphere. The joint material is adapted to later withstand both the environments within a process chamber during substrate processing, and the oxygenated atmosphere which may be seen within the shaft of a heater or electrostatic chuck.

The invention relates to a copper-ceramic composite comprising: a ceramic substrate containing alumina; a copper or copper alloy coating on the ceramic substrate; the alumina has a mean grain shape factor R.sub.a(Al.sub.2O.sub.3), defined as the arithmetic mean of the shape factors R of the alumina grains, of at least 0.4.

A cBN sintered material cutting tool is provided. The cBN cutting tool includes a cutting tool body, which is a sintered material including cBN grains and a binder phase, wherein the sintered material comprises: the cubic boron nitride grains in a range of 40 volume % or more and less than 60 volume %; and Al in a range from a lower limit of 2 mass % to an upper limit Y, satisfying a relationship, Y=0.1X+10, Y and X being an Al content in mass % and a content of the cubic boron nitride grains in volume %, respectively, the binder phase comprises: at least a Ti compound; Al.sub.2O.sub.3; and inevitable impurities, the Al.sub.2O.sub.3 includes fine Al.sub.2O.sub.3 grains with a diameter of 10 nm to 100 nm dispersedly formed in the binder phase, and there are 30 or more of the fine Al.sub.2O.sub.3 grains generated in an area of 1 m1 m in a cross section of the binder phase.

A ceramic composite can include a first ceramic phase and a second ceramic phase. The first ceramic phase can include a silicon carbide. The second phase can include a boron carbide. In an embodiment, the silicon carbide in the first ceramic phase can have a grain size in a range of 0.8 to 200 microns. The first phase, the second phase, or both can further include a carbon. In another embodiment, at least one of the first ceramic phase and the second ceramic phase can have a median minimum width of at least 5 microns.

The present invention provides a gallium nitride sintered body and a gallium nitride molded article which have high density and low oxygen content without using a special apparatus. According to the first embodiment, a gallium nitride sintered body, which is characterized by having density of 2.5 g/cm.sup.3 to less than 5.0 g/cm.sup.3 and an intensity ratio of the gallium oxide peak of the (002) plane to the gallium nitride peak of the (002) plane of less than 3%, which is determined by X-ray diffraction analysis, can be obtained. According to the second embodiment, a metal gallium-impregnated gallium nitride molded article, which is characterized by comprising a gallium nitride phase and a metal gallium phase that exist as separate phases and having a molar ratio, Ga/(Ga+N), of 55% to 80%, can be obtained.

Methods of forming a polycrystalline table may involve disposing a plurality of particles comprising a superabrasive material, a substrate comprising a hard material, and a catalyst material in a mold. The plurality of particles may be partially sintered in the presence of the catalyst material to form a brown polycrystalline table having a first permeability attached to an end of the substrate. The substrate may be removed from the brown polycrystalline table and catalyst material may be removed from the brown polycrystalline table. The brown polycrystalline table may then be fully sintered to form a polycrystalline table having a reduced, second permeability. Intermediate structures formed during a process of attaching a polycrystalline table to a substrate may include a substantially fully leached brown polycrystalline table. The substantially fully leached brown polycrystalline table may include a plurality of interbonded grains of a superabrasive material.

A composite includes a component and a glass or glass ceramic material. The component has a first coefficient of expansion .sub.1 and the glass or the glass ceramic material has a second coefficient of expansion .sub.2. The glass or the glass ceramic material has a surface with a thickness and thickness differences (TTV) within the surface, and thickness fluctuations (LTV). The composite has a residual stress in the glass or the glass ceramic material (WARP), and a geometric and material-physical degree of compatibility KG4.

A ceramic matrix composite laminate comprises a ceramic matrix that encapsulates a plurality of layers. Each layer comprises fibers. Each layer comprises a plurality of fill fibers and a plurality of warp fibers or a plurality of bias fibers. The outermost layer contains a different concentration of fibers per unit volume than a layer located near an interior of the ceramic matrix composite laminate. A gradient in the number of fibers exists between the outermost layer and the layer located at the interior of the ceramic matrix composite laminate, or a combination thereof. A combined ceramic matrix composite comprises a plurality of composite laminates; wherein each laminate has a different fiber concentration gradient from another laminate that it is in contact with.

A ceramic-copper composite having a flat plate shape, including: a ceramic layer; a copper layer; and a brazing material layer present between the ceramic layer and the copper layer. When a region having a length of 1,700 ?m in a long-side direction is a region P on a cut surface of the ceramic-copper composite obtained when the ceramic-copper composite is cut with a plane perpendicular to a main surface of the ceramic-copper composite, an average crystal grain size D1 of copper crystals at least partially present in a region P1 within 50 ?m on a side of the copper layer from an interface between the ceramic layer and the brazing material layer in the region P is 30 ?m or more and 100 ?m or less.

According to a method set forth herein a plurality of preform plies having first and second preform plies can be associated together to define a preform. The preform can be subject to chemical vapor infiltration (CVI) processing to define a ceramic matrix composite (CMC) structure.