Abstract: Abrasive material with particularly high abrasive performance is obtained in that the ceramic material contains an additive of 0.01 to 15 percent by weight, preferably 0.1 to 3 percent by weight of a chromium compound.

Abstract: The invention relates to a method for producing fine grained, sintering active nitride and/or carbonitride powder of titanium as well as, optionally, of other metals of the IVA, VA and VIA group of the periodic table of elements. In order to achieve, without any considerable comminution, a grain of high purity with a low grain size, the following steps are performed:The introduction into the reactor of a reaction mixture consisting of oxides of titanium and, optionally, of other metals of the IVA, VA and VIA group of the periodic system and a carbonaceous material;providing a nitrogen atmosphere in the reactor at a decreased pressure;heating the content of the reactor to a temperature of between 800.degree. C. and 2000.degree. C., preferably between 1000.degree. C. and 1900.degree. C., and keeping the temperature within a range of between 1400.degree. C. and 1800.degree. C.

Abstract: Ceramic sintered body, in particular abrasive grain, based on .alpha.-Al.sub.2 O.sub.3, said body being arranged in such a manner that improved abrasive results are achieved, said body being bound into a structure by means of a glass-like ceramic binder and showing a drop in hardness from its center to its edge of less than 1800 N/mm.sup.2, preferably less than 1000 N/mm.sup.2, and, in particular, less than 500 N/mm.sup.2.

Abstract: Sintered microcrystalline ceramic material based on .alpha.-Al.sub.2 O.sub.3 with an addition of 0.01 to 2.0 weight percent of a cerium compound, consisting of a microcrystalline matrix and 0.1 to 30 volume percent whisker-like needles, whereby said cerium compound is mainly present in the needles. The whisker-like needles give this material a special tenacity combined with good abrasive results.

Abstract: Sintered microcrystalline ceramic material based on .alpha.-Al.sub.2 O.sub.3 with an addition of 0.01 to 2.0 weight percent of a cerium compound, consisting of a microcrystalline matrix and 0.1 to 30 volume percent whisker-like needles, whereby said cerium compound is mainly present in the needles. The whisker-like needles give this material a special tenacity combined with good abrasive results.

Abstract: A sintered, microcrystalline abrasive material consists of at least 99.5%, by weight, of .alpha.-Al.sub.2 O.sub.3 crystallites having a size of less than 2 .mu. and the material having a density of at least 97% of the theoretical density. This abrasive material has a very high abrasive property and can be used in grinding bands or discs.

Abstract: The invention relates to a process for the production of rare earth metals and alloys thereof. The process exploits the known advantages of metallothermal reduction techniques while decisively enhancing their reduction process. Rare earth halides and/or rare earth oxides are reduced in an electric arc furnace by means of one or several alkaline earth metals, preferably, calcium. Additives such as iron metals or other alloying elements, alkali- and/or alkaline earth metal salt, may be added to the electric arc furnace in a two-phase furnace operation. The reduction takes place in an atmosphere inert to rare earth metals, rare earth compounds, and alkaine earth metals. Agitation is produced in the metal in the furnace by eletromagnetic forces caused by a suitably selected current-to-voltage ratio for the electric arc, in order to achieve reduction in the shortest possible time and as completely as possible.

Abstract: An abrasive material of great hardness and high tenacity particularly suitable for high-pressure grinding consists essentially of a sintered, microcystalline .alpha.--Al.sub.2 O.sub.3 abrasive material having a purity of least 98.5% and a density of at least 95% of theoretical density, the .alpha.--Al.sub.2 O.sub.3 crystallites of the material being smaller than 4.mu., preferably smaller than 3.mu..

Abstract: Sodium percarbonate is prepared from a reaction mixture of an Mg.sup.++ containing hydrogen peroxide solution, sodium hexametaphosphate and an aqueous sodium carbonate suspension containing sodium chloride and/or sodium sulfate, wherein the initial reaction mixture contains only 3-50%, by weight, of the soda suspension while the remainder of the reactants are added subsequently. The mixture is continuously stirred until the level of peroxide remains constant, and the crystalline percarbonate is then separated.

Abstract: An abrasive material is prepared from a starting material comprised of a spent metallic catalyst on an alumina carrier by melting the starting material with a reducing agent to obtain a melt consisting of a melt component including the alumina on an alloy residue, cooling the melt at a speed correlated with a desired crystallite size of the abrasive material to be obtained, and mechanically separating the melt component from the alloy residue before or after solidification, the melt component constituting the abrasive material.

Abstract: Flint is produced from a mischmetal and iron melt by permitting the alloy melt to cool in a mold at a slow enough rate that, as the solidification point of the melt is approached, its temperature is maintained at 800.degree.-600.degree. C for at least 10 minutes. The alloy melt is subsequently extruded and the extrudate is subjected to a heat treatment at temperatures from 370.degree.-470.degree. C for 1/2 to 4 hours, the heat treatment being discontinued before the limit value of the thermodynamic equilibrium has been reached.

Abstract: Abrasive granules are produced from alumina or an alumina-zirconia mixture by melting the oxide material and rapidly cooling the melt. To control the solidification velocity, the melt is cast into a molten chloride of Na, Ca, Ba, Mg or mixtures thereof to cool the oxide material melt, the chloride is separated from the cooled and solidified oxide material, and thereafter abrasive granules are produced from the solidified oxide material.

Abstract: A rare earth metal salt containing fluorine ions is separated from an acidic solution of the salt in the presence of an amount of boric acid sufficient to sequester the fluorine ions whereby the fluorine ions are bound in the solution and fluorine-free rare earth metal salt is recovered from the solution.

Abstract: The brightness of a cerium oxide is improved by adding a boron compound to a cerium salt or a mixture of cerium salts, and the calcining the mixture in the presence of air in a conventional manner.

Abstract: Agglomerated vanadium oxides of the formula V.sub.2 O.sub.x, wherein x is between 3.8 and 4.6, are prepared by thermally decomposing ammonium polyvanadate at 600.degree.-900.degree. C and permitting the resultant solid decomposition products and reducing gases to react. The reducing gases displace the air and/or scavenging gas in the reaction zone.