Abstract: Apparatus is disclosed for reacting a powder with a gas comprising a shroud consisting of a first section having a peripheral cylindrical wall with inner surface and outer surface. Inner surface defines a cavity which serves as reaction chamber in which powder and gas react. First section is detatchably mounted at top end to exit nozzle of high temperature source. First section has powder inlet opening(s) extending through peripheral wall from outer surface to inner surface, thereby connecting the outside with reaction chamber through which powder enters the chamber. Powder inlet opening(s) are positioned sufficiently close to exit nozzle to allow powder to melt and react with gas in the molten state. Second section forms cylindrical jacket skirting lower part of first section at a point below powder inlet openings. Jacket has outer peripheral wall, inner wall one and same with peripheral wall of first section, and top and bottom ring plates forming top and bottom walls respectively of second section.

Abstract: A disc is disclosed which comprises a top layer, a middle layer, and a bottom layer. The top layer is placed proximate to a high temperature reactor and at least the outer surface of the top layer is made of a material which allows it to act as a substrate against which molten particles are impacted to microatomize the particles. The layers are positioned one above the other with a first space between the bottom surface of the top layer and the top surface of the middle layer, and a second space between the bottom surface of the middle layer and the top surface of the bottom layer. The top and bottom layers are joined together and stabilized by a peripheral wall around the circumferential edge of the top and bottom layer. The middle layer is fixedly mounted to the bottom layer. The middle layer is smaller in diameter than the diameters of the top and bottom layers so that a third space is defined between the inner surface of the peripheral wall and the circumferential edge of the middle layer.

Abstract: A process is disclosed for producing discontinuous metal foils. The process involves entraining metal powder particles in a carrier gas and passing the powder particles through a high temperature zone at a temperature above the melting point of the powder particles to melt at least about 50% by weight of the powder particles and thereafter resolidifying the resulting high temperature treated material by impacting the material against a substrate to form the foils.

Abstract: A process is disclosed for producing metal flakes. The process involves entraining the metal powder particles in a carrier gas and passing the powder particles through a high temperature zone at a temperature above the melting point of the powder particles to melt at least about 50% of the powder particles, resolidifying the resulting high temperature treated material by impacting the material against a substrate, and thereafter contacting the material with a non-oxidizing gas which can be nitrogen, argon, hydrogen, helium or combinations of these to remove the material from the substrate in the form of flakes.

Abstract: Si.sub.3 N.sub.4 ceramics exhibiting densities and modulus of rupture values heretofore obtainable only by hot pressing are produced by pressureless sintering of powder compacts of partly amorphours, partly crystalline Si.sub.3 N.sub.4 powder containing between 5 and 60 percent by weight of crystalline material.