Method of making selected phases of nanocrystalline ceramic materials. Various methods of controlling the production of nanocrystalline alpha alumina and titanium oxygen phases are described. Control of the gas atmosphere and use of particular oxidation treatments give rise to the ability to control the particular phases provided in the aluminum/oxygen and titanium/oxygen system.
A new transition alumina is made by heating substantially pure diaspore in a vacuum to an elevated temperature of about 300-1000.degree. C. The new transition alumina has increased surface area compared with alpha-alumina formed by heating diaspore in air.
A process for producing multi-component and multiphase nanophase materials is provided wherein a plurality of elements are vaporized in a controlled atmosphere, so as to facilitate thorough mixing, and then condensing and consolidating the elements. The invention also provides for a multicomponent and multiphase nanocrystalline material of specified elemental and phase composition having component grain sizes of between approximately 1 nm and 100 nm. This material is a single element in combination with a binary compound. In more specific embodiments, the single element in this material can be a transition metal element, a non-transition metal element, a semiconductor, or a semi-metal, and the binary compound in this material can be an intermetallic, an oxide, a nitride, a hydride, a chloride, or other compound.
A method and system for synthesizing nanocrystalline material. A system includes a chamber, a nonconsumable cathode shielded against chemical reaction by a working gas not including an oxidizing gas, but including an inert gas, a consumable anode vaporizable by an arc formed between the cathode and the anode, and a nozzle for injecting at least one of a quench and reaction gas in the boundaries of the arc.
A method and apparatus for reacting sodium vapor with gaseous chlorides in a flame to produce nanoscale particles of un-oxidized metals, composites and ceramics. The flame is operated under conditions which lead to condensation of a NaCl by-product onto the particles. The condensate encapsulates the particles and aids in controlling desired particle size and preventing undesirable agglomeration among the particles during synthesis. Following synthesis, oxidation of the particles is inhibited by the encapsulation and handling character of the products is greatly enhanced. Electron microscopy has revealed that synthesized products are composed of discrete nanoparticles in a NaCl matrix. The NaCl encapsulate has been effectively removed from the particles by both washing and known sublimation technique at 800.degree. C. under low pressure.
Quasi-crystalline aluminum alloy ultrafine particles are produced by a gas-phase reaction and consist of at least one alloy element from the group of V, Cr, Mn, Fe, Co, Ni, Cu and Pd, for example palladium (Pd) in an amount represented by 20 atomic %.ltoreq.Pd.ltoreq.30 atomic %, and the balance of aluminum. Palladium has a catalyst power, and the ultrafine particles have a large specific surface area, because they have a particle size d.ltoreq.200 nm. Such ultrafine particles have a high catalytic activity in a methanol decomposing reaction and also have a good retention of catalytic activity.
