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 ΔL.sub.c>ΔL.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 ΔL.sub.c and the sintering shrinkage of the silicon carbide matrix is ΔL.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.

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.

A SiC based sinterable powder mixture comprising, by dried weight of said powder: a) a mineral content comprisingsilicon carbide (SiC) particles, -mineral boron compound particles, the powder comprising at least 50% by weight of SiC and the total mineral content of the powder being at least 90% by weight, b) at least a water insoluble carbon-containing source, in particular a carbon containing resin, the powder comprising at least 1% by weight, and preferably less than 10% by weight,of said water insoluble carbon-containing source, wherein the average particle size of said sinterable powder is comprised between 0.5 to 2.0 micrometers.

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.

The invention relates to a porous multi-layered coloured zirconia dental mill blank comprising a bottom layer B having the composition COMP-B which comprises ceramic components CER-COMP-B, colouring components COL-COMP-B and stabilizing components STAB-COMP-B, a top layer E having the composition COMP-E which comprises ceramic components CER-COMP-E, colouring components COL-COMP-E stabilizing components STAB-COMP-E, at least one intermediate layer Ex having the composition COMP-E of top layer E, at least one intermediate layer Bx having the composition COMP-B of bottom layer B, x being an integer and indicating the number of intermediate layers, wherein the layers with compositions COMP-B and COMP-E are arranged in alternating order, and wherein the thickness of the individual layers B, Bx is decreasing from bottom to top and the thickness of the individual layers E, Ex is decreasing from top to bottom. The dental mill blank can be used for producing dental articles.

A transparent sintered body having fewer air bubble-derived defects is provided. More specifically, a method is provided of producing a ceramic molded product including at least a step of pressure-molding ceramic granules having a Hausner ratio, which is a quotient obtained by dividing a tapped bulk density by a loose bulk density, of 1.0 or more but not more than 1.2. Also provided is a method of producing a transparent sintered body including at least each of the steps of the above method to obtain a ceramic molded product and a step of heating and sintering the resulting ceramic molded product. The transparent sintered body has a linear transmittance of 78% or more at a wavelength of 600 nm to 2000 nm inclusive except for an element-derived characteristic absorption wavelength.

A zirconia sintered body contains aluminum, cobalt, and manganese and a remaining portion consisting of yttria-containing zirconia. In an oxide exchange, aluminum content is 5.0 wt % or more and 30.0 wt % or less, cobalt content is 0.1 wt % or more and 2.0 wt % or less, and manganese content is 0.5 wt % or more and 7.0 wt % or less.

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 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 MgF.sub.2 system fluoride sintered body for a radiation moderator having a compact polycrystalline structure excellent in radiation moderation performance, especially neutron moderation performance, contains CaF.sub.2 of 90% by weight at the maximum and has a relative density of 95.2% or more.