Sintered oxides

The matte can be treated in different ways, depending on the copper content and on the desired product. In some cases, the copper content of the Bessemer matte is low enough to allow the material to be cast directly into sulfide anodes for electrolytic refining. Usually it is necessary first to separate the nickel and copper sulfides. The copper—nickel matte is cooled slowly for ca 4 d to faciUtate grain growth of mineral crystals of copper sulfide, nickel—sulfide, and a nickel—copper alloy. This matte is pulverized, the nickel and copper sulfides isolated by flotation, and the alloy extracted magnetically and refined electrolyticaHy. The nickel sulfide is cast into anodes for electrolysis or, more commonly, is roasted to nickel oxide and further reduced to metal for refining by electrolysis or by the carbonyl method. Alternatively, the nickel sulfide may be roasted to provide a nickel oxide sinter that is suitable for direct use by the steel industry. 

Uses. The sinter oxide form is used as charge nickel in the manufacture of alloy steels and stainless steels (see Steel). The oxide furnishes oxygen to the melt for decarburization and slagging. In 1993, >100, 000 metric tons of nickel contained in sinter oxide was shipped to the world s steel industry. Nickel oxide sinter is charged as a granular material to an electric furnace with steel scrap and ferrochrome the mixture is melted and blown with air to remove carbon as CO2. The melt is slagged, pouted into a ladle, the composition is adjusted, and the melt is cast into appropriate shapes. A modification of the use of sinter oxide is its injection directiy into the molten metal (33). 

Nickel Oxide Sinter 75, Product Data Sheet A-789, International Nickel Co., Inc., New York, 1977. 

Deactivation is a common and important phenomenon in FTS. Deactivation effects of water are recorded on all commonly used supports. The suggested mechanisms include oxidation, sintering and solid state reactions rendering cobalt inactive. 

Sieber KD, Sanchez, C, Turner JE, Somorjai GA (1985) Preparation, electrical and photoelectrochemical properties of magnesium doped iron oxide sintered discs. Mat Res Bull 20 153-162... 

Sulfide ores are processed by a number of pyrometallurgical processes roasting, smelting, and converting. During these processes, sulfur and iron are removed to deld a sulfur-deficient copper-nickel matte. Especially after roasting and converting, the nickel in the matte may consist primarily of nickel subsulfide. After physical separation of the copper and nickel sulfides, the nickel is refined electrochemically or by the carbonyl process. The treatment of the matte depends on the end use of the nickel. Alternatively, the sulfide can be roasted to form a nickel oxide sinter that is used directly in steel production. 

In 1994, the United States imported 140,693 tons of nickel, including 109,187 tons of unwrought metal, 1,015 tons of powder, 6,339 tons of nickel waste and scrap, 4,973 tons of oxide and oxide sinter,... 

The atmosphere is also important in sintering. Gas trapped in closed pores will limit pore shrinkage unless the gas is soluble in the grain boundary and can diffuse from the pore. Alumina doped with MgO can be sintered to essentially zero porosity in hydrogen or oxygen atmospheres, which are soluble, but not in air, which contains insoluble nitrogen. The density of oxides sintered in air is commonly less than 98% and often only 92-96%. The sintering atmosphere is also important in that it may influence the sublimation or the stoichiometry of the principal particles or dopants. 

Melnick (11) has made the most extensive study of the slow photoconductive response. Using zinc oxide sintered in air, he has studied responses in the time range from 0.3 to 10 sec. 

Manufactured abrasives include silicon carbide, fused aluminum oxide, sintered aluminum oxide, sol-gel sintered aluminum oxide, fused zirco-nia-alumina, synthetic diamond, cubic boron nitride, boron carbide, slags, steel shot, and grit. 

Di-m-xylyl tellurium oxide, [(CH3)2C6H3]2TeO.—The corresponding dibromide is converted to the oxide by warming with sodium hydroxide on the water-bath. The oxide sinters at 212° C., melts at... 

The extraction of zinc by carbothermic reduction of zinc oxide sinter at 1,100°C can be represented by the reaction... 

Metal powders Metal oxides Sintered metal reinforcement Mica Asbestos (obsolete) Sintered bronze matrix PTFE fibres... 

Other oxides. Sintered MgO has a high melting point (2826 "C) but has found no wider application. Transparent plates have recently been prepared from polycrystalline MgO by hot pressing with LiF or NaF additions (Rice, 1971). 

The uranium(IV) oxide produced by the above-described processes is used for the manufacture of uranium(IV) oxide sintered pellets. The uranium(IV) oxide is ground, pressed in e.g. hydraulic presses, then sintered at ca. 1700°C in the presence of hydrogen and thereby shrink to the desired... 

Giovanoli et al. [23] conclude that there is a structural relationship between y-Zn(OH)2.0.5H2O and P-Zn(OH)2, into which it is converted topotactically on dehydration. These hydroxides and y-Zn(OH)2 all decompose in an electron beam to yield highly-oriented ZnO. The crystal structure of the original hydroxide appears to exert a strong influence on the rate of oxide sintering at about 1070 K. 

Perovskites such as LaCo03 and Sr-doped LaCoOa have been investigated extensively as combustion catalysts [17] but, as can be seen from Table 1, these oxides sinter rapidly at 1000 °C giving low-surface-area materials with a low activity on a per gram basis. 

Black nickel oxide Bunsenite C.l. 77777 CCRIS 431 Cl 77777 EINECS 215-215-7 Green nickel oxide HSOB 1664 Mononickel oxide Nickel (II) oxide Nickel monoxide Nickel oxide Nickel oxide (NiO) Nickel oxide sinter 76 Nickel protoxide Nickel(2+) oxide Nickel(ll) oxide Nickelous oxide. Used in preparation of nickel salts, in porcelain painting and fuel cell electrodes. Green powder mp = 1960" d = 6.6700 insoluble in H2O soluble in acids. Atomergic Chemetals Cerac Nihon Kagaku Sangyo Noah Chem. 

Sintering of the Acid Function.- The most important factors that produce oxide sintering are temperature, time, and the presence... 

The Au/y-AbOa catalysts can be deactivated both thermally and by CO oxidation. Sintering of Au particles has been suggested often as the cause of deactivation. In the case of thermal deactivation, since the catalyst had experienced 350 C calcination during preparation, it is unlikely that mild heating to 100°C would cause severe sintering of the Au particles. Moreover, it is unlikely that exposure to water vapor at room temperature could cause fragmentation of Au particles into smaller ones to recover the lost activity. 

Figure 6.21. Thermodesorption spectrum of nickel oxide sinters exposed to air...

H. Bjorklund, L. K. Falk, K. Rundgren and J. Wasen, a-Si3N4 Grain Growth, Part I Effect of Metal Oxide Sintering Additives Journal of the European Ceramic Society, 17,1997,1285-1299. 

Source of Gas KIVCET Oxidation Sinter Machine Sinter Machine Sinter Machine 1 QSL-Converter... 

Borgwardt RH (1989) Calcium oxide sintering in atmospheres containing water and carbon dioxide. Ind Eng Chem Res 28 493-500... 

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