A method of forming a water resistant boundary on a fissile material for use in a water cooled nuclear reactor is described. The method comprises mixing a powdered fissile material selected from the group consisting of UN and U.sub.3Si.sub.2 with an additive selected from oxidation resistant materials having a melting or softening point lower than the sintering temperature of the fissile material, pressing the mixed fissile and additive materials into a pellet, sintering the pellet to a temperature greater than the melting point of the additive. Alternatively, if the melting point of the oxidation resistant particles is greater than the sintering temperature of UN or U.sub.3Si.sub.2, then the oxidation resistant particles can have a particle size distribution less than that of the UN or U.sub.3Si.sub.2.

A nanoparticle containing monoclinic lutetium oxide. A method of: dispersing a lutetium salt solution in a stream of oxygen gas to form droplets, and combusting the droplets to form nanoparticles containing lutetium oxide. The combustion occurs at a temperature sufficient to form monoclinic lutetium oxide in the nanoparticles. An article containing lutetium oxide and having an average grain size of at most 10 microns.

Provided are a transparent fluorescent sialon ceramic having fluorescence and optical transparency; and a method of producing the same. Such a transparent fluorescent sialon ceramic includes a sialon phosphor which contains a matrix formed of a silicon nitride compound represented by the formula M.sub.x(Si,Al).sub.y(N,O).sub.z (here, M represents at least one selected from the group consisting of Li, alkaline earth metals, and rare earth metals, 0≤x/z<3, and 0<y/z<1) and a luminescent center element.

Provided is a transparent spinel sintered body which is formed from an Mg—Al spinel powder having an Al/Mg ratio of from 1.97 to 2.03 or a mixed powder of an Mg oxide and an Al oxide, and wherein the total content of metal impurities excluding Al and Mg is less than 100 ppm. A sample of this transparent spinel sintered body having a thickness of 3 mm has a total light transmittance of 80% or more in the thickness direction for the wavelength range of from 190 nm to 400 nm; and this transparent spinel sintered body is usable as a medium that transmits light from an ultraviolet light emitting element.

Techniques and compositions are disclosed for three-dimensional printing with powder/binder systems including, but not limited to, metal injection molding powder materials, highly-filled polymer composites, and any other materials suitable for handling with various additive manufacturing techniques, and further suitable for subsequent debinding and thermal processing into a final object.

A sintered body includes a solid solution containing cobalt and iron, with the balance being zirconia. The total content of cobalt in terms of CoO and iron in terms of Fe.sub.2O.sub.3 is more than 0.1 wt % and less than 3.0 wt %, and the proportion of cobalt regions larger than 5.5 μm.sup.2 in an elemental map obtained using an electron probe microanalyzer is 25% or less.

A garnet-structure complex oxide powder having formula (1) is prepared by adding an aqueous solution containing (a) Tb ion, an aqueous solution containing (b) Al ion, and an aqueous solution containing (c) Sc ion to a co-precipitating aqueous solution, to induce a co-precipitate of components (a), (b) and (c), filtering, heat drying and firing the co-precipitate.
(R.sub.1-xSc.sub.x).sub.3(A.sub.1-ySc.sub.y).sub.5O.sub.12  (1)
R is yttrium or a lanthanoid element, typically Tb, A is a Group 13 element, typically Al, x and y are 0<x<0.08 and 0.004<y<0.16.

The friction stir welding tool member according to the present invention is made of a silicon nitride sintered body, wherein the silicon nitride sintered body contains 15% by mass or less of additive components except silicon nitride in such a manner that the additive components include at least one element selected from lanthanoid elements and at least one element selected from Mg, Ti, Hf, and Mo. In addition, it is preferable that the additive components further include at least one element selected from Al, Si, and C. According to the above-described configuration, a friction stir welding tool member having an excellent durability can be provided.

A method for sintering metallic and/or non-oxide components includes completely encapsulating, in a metal halide salt, a green body comprising at least one metallic and/or non-oxide powder, and compressing the encapsulated green body so as to be gastight. The method further includes heating, together with a metal halide salt in the presence of oxygen up to sintering temperatures, the compressed, encapsulated green body. The method additionally includes at least partially dissolving, after cooling, the metal halide salt in a liquid so that the sintered component can be removed.

The invention relates to a process for fabricating complex mechanical shapes from metal or ceramic, and in particular to fabricating complex mechanical shapes using a pressure-assisted sintering technique to address problems relating to variations in specimen thickness and tooling, or densification gradients, by 3-D printing of a sacrificial, self-destructing powder mold is created using e.g. alumina and swellable binders such as polysaccharides. The binder-free sintering powder that forms the manufactured item is injected into the mold, and high pressure is applied. The powder assembly can then be sintered by any pressure assisted technique to full densification and the self-destructing mold allows the release of the fully densified complex manufactured item.