A zirconia sintered body that suppresses discoloration due to porcelain. The zirconia sintered body contains at least one of a coloring agent A, which is erbium oxide and a coloring agent B, which is nickel oxide, and contains a composite oxide of zirconium and vanadium. A composition, containing zirconium oxide, yttrium oxide, and a coloring agent, where the coloring agent contains at least one of a coloring agent A, which is erbium oxide and a coloring agent B, which is nickel oxide, and contains a coloring agent C, which is a composite oxide of zirconium and vanadium.

A sintered molded article includes a ceramic of /-sialon having a grain boundary phase, the grain boundary phase containing at least one hard material formed in situ as an additional phase. A method for the production of the sintered molded article uses at least the following compounds as a starting material: Si.sub.3N.sub.4, AlN, and, if applicable, Al.sub.2O.sub.3, at least one oxide of the rare earths, and at least one oxide of the element titanium.

Methods for producing wavelength converters are described. The methods include sintering a mixture consisting essentially of first particles and second particles to form a sintered article. In embodiments the first particles consist essentially of particles of -SiAlON or precursors thereof, and the second particles consist essentially one or more sintering aids or precursors thereof. In embodiments the sintered article has a density that is greater than or equal to about 90% of a theoretical bulk density of the mixture, and is configured to convert primary light incident thereon to secondary light, wherein the secondary light exhibits a peak with a full width half maximum of greater than 0 to about 60 nanometers (nm) within a wavelength range of about 495 nm to about 600 nm.

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.

A frame integrated vacuum hot press comprises a frame chamber including a vacuum space having an opened side; a door installed to the frame chamber to open or close the opened side of the vacuum space; a heating chamber including a heating space and a heater heating an object to be formed which is loaded in the heating space; and a cylinder which is connected to the frame chamber to apply pressure to the object to be formed which is loaded in the heating space of the heating chamber.

A method for preparation of a high-density hexagonal boron nitride (hBN) ceramic material is disclosed. According to the method, the surface of hBN powder is coated with an evenly-dispersed SiO.sub.2 nanoparticle layer using tetraethyl orthosilicate as a precursor, and then the high-density hBN ceramic material is obtained by pressureless sintering. The relative density of the prepared hBN ceramic material is over 80%.

The present invention relates to a method for preparing a fully ceramic capsulated nuclear fuel material containing three-layer-structured isotropic nuclear fuel particles coated with a ceramic having a composition which has a higher shrinkage than a matrix in order to prevent cracking of ceramic nuclear fuel, wherein the three-layer-structured nuclear fuel particles before coating is included in the range of between 5 and 40 fractions by volume based on after sintering. More specifically, the present invention provides a composition for preparing a fully ceramic capsulated nuclear fuel containing three-layer-structured isotropic particles coated with the substance which includes, as a main ingredient, a silicon carbine derived from a precursor of the silicon carbide wherein a condition of L.sub.c>L.sub.m at normal pressure sintering is created, where the sintering shrinkage of the coating layer of the three-layer-structured isotropic nuclear fuel particles is L.sub.c and the sintering shrinkage of the silicon carbide matrix is L.sub.m; material produced therefrom; and a method for manufacturing the material. The residual porosity of the fully ceramic capsulated nuclear fuel material is 4% or less.

A zirconia sintered body is provided having a color tone equivalent to the color tone guides of various natural teeth and having the same aesthetics as a natural front tooth. The present invention provides a colored translucent zirconia sintered body comprising zirconia containing greater than 4.0 mol % and not greater than 6.5 mol % of yttria, less than 0.25 mol % of erbia, less than 2,000 ppm of iron oxide in terms of Fe.sub.2O.sub.3, less than 0.01 wt. % of cobalt oxide in terms of CoO, and less than 0.1 wt. % of alumina; the zirconia sintered body having a relative density of not less than 99.90%, a total light transmittance of not less than 25% and less than 40% for light having a wavelength of 600 nm at a sample thickness of 1.0 mm, and a strength of not less than 500 MPa.

Zirconia dental ceramics exhibiting opalescence and having a grain size in the range of 10 nm to 300 nm, a density of at least 99.5% of theoretical density, a visible light transmittance at or higher than 45% at 560 nm, and a strength of at least 800 MPa.

Disclosed is a method for fabricating a solid article from a boron carbide powder comprising boron carbide particles that are coated with a titanium compound. Further disclosed herein are the unique advantages of the combined use of titanium and graphite additives in the form of water soluble species to improve intimacy of mixing in the green state. The carbon facilitates sintering, whose concentration is then attenuated in the process of forming very hard, finely dispersed TiB.sub.2 phases. The further recognition of the merits of a narrow particle size distribution B.sub.4C powder and the use of sintering soak temperatures at the threshold of close porosity which achieve post-HIPed microstructures with average grain sizes approaching the original median particle size. The combination of interdependent factors has led to B.sub.4C-based articles of higher hardness than previously reported.