A method of making a hot surface igniter is described. A silicon carbide composition that includes both fines fraction and a coarse fraction is sintered in a nitrogen and argon reducing atmosphere in a manner that controls the incorporation of nitrogen with in the lattice of recrystallized silicon carbide. The controlled incorporation of nitrogen in the lattice provides enhanced control over heating and electrical properties, while simultaneously achieving a lower surface area fully recrystallized structure for oxidation resistance and long service life.

In a diamond polycrystal, a value of a ratio (a′/a) of a′ to a is less than or equal to 0.99 in a Knoop hardness test performed under a condition defined in JIS Z 2251:2009, where the a represents a length of a longer diagonal line of a first Knoop indentation formed in a surface of the diamond polycrystal when a Knoop indenter with a test load of 4.9 N is pressed onto the surface of the diamond polycrystal, and the a′ represents a length of a longer diagonal line of a second Knoop indentation remaining in the surface of the diamond polycrystal after releasing the test load.

A silicide-based composite material is disclosed, comprising a silicide of Mo, B, W, Nb, Ta, Ti, Cr, Co, Y, or a combination thereof, Si3N4, and at least an oxide, as well as and a process for producing the same.

A sintered material comprises cubic boron nitride and a first material that is a partially stabilized ZrO.sub.2 with Al.sub.2O.sub.3 dispersed therein at crystal grain boundaries and/or in crystal grains, the sintered material comprising 20% by volume or more and 80% by volume or less of the cubic boron nitride, the sintered material comprising 0.001% by mass or more and 1% by mass or less of nitrogen in the first material when the first material is measured through secondary ion mass spectrometry.

A method and a fugitive mold for producing a cast-metal part are provided. In some embodiments, the fugitive mold may be formed by three-dimensionally (3D) printing a preceramic resin in the shape of a fugitive mold; curing the preceramic resin to form a preceramic polymer, and pyrolyzing the fugitive mold to convert the preceramic polymer to a metastable ceramic material. The metastable ceramic material may include an amorphous silicon oxycarbide ceramic. A cast-metal part may be formed by filling the fugitive mold with a liquid metal or alloy, and allowing the liquid metal or alloy to solidify over a first length of time. The cast-metal part may then be retrieved by heating the fugitive mold at a temperature lower than the melting point of the cast-metal part for a second length of time longer than the first length of time to disintegrate the metastable ceramic material.

A silicon carbide-graphite composite is described, including (i) interior bulk graphite material and (ii) exterior silicon carbide matrix material, wherein the interior bulk graphite material and exterior silicon carbide matrix material inter-penetrate one another at an interfacial region therebetween, and wherein graphite is present in inclusions in the exterior silicon carbide matrix material. Such material may be formed by contacting a precursor graphite article with silicon monoxide (SiO) gas under chemical reaction conditions that are effective to convert an exterior portion of the precursor graphite article to a silicon carbide matrix material in which graphite is present in inclusions therein, and wherein the silicon carbide matrix material and interior bulk graphite material interpenetrate one another at an interfacial region therebetween. Such silicon carbide-graphite composite is usefully employed in applications such as implant hard masks in manufacturing solar cells or other optical, optoelectronic, photonic, semiconductor and microelectronic products, as well as in ion implantation system materials, components, and assemblies, such as beam line assemblies, beam steering lenses, ionization chamber liners, beam stops, and ion source chambers.

A cBN sintered material cutting tool includes a cutting tool body that is made of a sintered material including cubic boron nitride particles and a binder phase, in which: an average particle size of the cBN particles is 0.5 μm or less and a content ratio of the cBN particles in the sintered material is 35 vol % to 80 vol %; and the binder phase includes 1.0 vol % to 20 vol % of an Al compound, an average particle size of the Al compound present in the binder phase is 300 nm or less, and a value of a ratio (a value of S.sub.N/S.sub.O; area ratio) of a content S.sub.N of nitrogen (N) included in the Al compound to a content S.sub.O of oxygen (O) included in the Al compound is 1.1 to 5.

A method of making a hot surface igniter is described. A silicon carbide composition that includes both fines fraction and a coarse fraction is sintered in a nitrogen and argon reducing atmosphere in a manner that controls the incorporation of nitrogen with in the lattice of recrystallized silicon carbide. The controlled incorporation of nitrogen in the lattice provides enhanced control over heating and electrical properties, while simultaneously achieving a lower surface area fully recrystallized structure for oxidation resistance and long service life.

A sintered material comprises cubic boron nitride and a first material that is a partially stabilized ZrO.sub.2 with Al.sub.2O.sub.3 dispersed therein at crystal grain boundaries and/or in crystal grains, the sintered material comprising 20% by volume or more and 80% by volume or less of the cubic boron nitride, the sintered material comprising 0.001% by mass or more and 1% by mass or less of nitrogen in the first material when the first material is measured through secondary ion mass spectrometry.

The present disclosure generally relates to silicon carbide crystals which may be used in optical applications, and to methods for producing the same. In one form, a composition includes an aluminum doped silicon carbide crystal having residual nitrogen and boron impurities. The concentration of aluminum in the silicon carbide crystal is greater than the combined concentrations of nitrogen and boron in the silicon carbide crystal, and the silicon carbide crystal includes an optical absorption coefficient of less than about 0.4 cm.sup.−1 at a wavelength in a range between about 400 nm to about 800 nm.