The present invention relates to a method of manufacturing a ceramic article (3) from a metal or metal matrix composite preform (1) provided by 3D-printing or by 3D-weaving. The preform (1) is placed in a heating chamber (2), and a predetermined time-temperature profile is applied in order to controllably react the preform (1) with a gas introduced into the heating chamber (2). The metal, the gas and the time-temperature profile are chosen so as to induce a metal-gas reaction resulting in at least a part of the preform (1) transforming into a ceramic. Preferred embodiments of the invention comprises a first oxidation stage involving a metal-gas reaction in order to form a supporting oxide layer (5) at the surface of the metal, followed by a second stage in which the heating chamber (2) is heated to a temperature above the melting point of the metal to increase the kinetics of the chemical reaction. The invention also relates to a number of advantageous uses of a ceramic article manufactured as described.

A castable refractory composition may include from 5% to 95% by weight of alumina, aluminosilicate, or mixtures thereof; from 0.5% to 1.5% by weight alkaline earth metal oxide and/or hydroxide, and 0.1% to 5% by weight of silica having a surface area of at least about 10 m.sup.2/g. The refractory composition may include no more than 0.5% by weight of cementitious binder. The refractory composition may release less than 25 cm.sup.3 of hydrogen gas per kilogram of castable refractory composition upon addition of water. The refractory compositions may set on addition of water.

The object of the present invention is to provide a large-sized gallium nitride-based sintered body having a small oxygen amount and high strength, a large-sized gallium nitride-based sintered body having a small oxygen amount and containing a dopant, to obtain a highly crystalline gallium nitride thin film which has become a n-type or p-type semiconductor by a dopant, and methods for producing them. A gallium nitride-based sintered body, which has an oxygen content of at most 1 atm % and an average particle size (D50) of at least 1 m and at most 150 m.

A dielectric material includes a main component represented by (Ba.sub.1-xCa.sub.x)(Ti.sub.1-y(Zr, Sn, Hf).sub.y)O.sub.3 (0x1 and 0y0.5); a first subcomponent including at least one of elements among Y, Dy, Ho, Er, Gd, Ce, Nd, Nb, Sm, Tb, Eu, Tm, La, Lu, and Yb; a second subcomponent including Si and/or Al; and a third subcomponent including Ba and/or Ca.

This invention relates to a ceramic module for assembly into a therapeutic device for treating a human or animal body with irradiation of far infrared. More specifically, said ceramic module can simultaneously emit blackbody-like thermal radiation and stimulated FIR-photons radiation in 3-16 m wavelength spectrum, while the overall radiation in 8-14 m wavelength range is measured to be an approximated blackbody radiation at a temperature that is at least 1 K (or 1 C.) higher than the actual body temperature of said ceramic module, signifying an effective emissivity greater than 1.0. Said ceramic module may be used alone or serve as components of a therapeutic device for increasing physiologic performance, immune competence, health, and mean lifespan of human or animal.