Magnesium oxide sintering

Two methods are available for the preparation of the powder (Smith, 1969). In one, zinc oxide is ignited at 900 to 1000 °C for 12 to 24 hours until activity is reduced to the desired level. This oxide powder is yellow, presumably because zinc is in excess of that required for stoichiometry. Alternatively, a blend of zinc oxide and magnesium oxide in the ratio of 9 1 is heated for 8 to 12 hours to form a sintered mass. This mass is ground and reheated for another 8 to 12 hours. The powder is white. Altogether the powder is similar to that used in zinc phosphate cements. 

Magnesium oxide is always blended with the zinc oxide prior to ignition. Magnesium oxide promotes densification of the zinc oxide, preserves its whiteness and renders the sintered powder easier to pulverize (Crowell, 1929). The sintered mixed oxide has been shown to contain zinc oxide and a solid solution of zinc oxide in magnesium oxide (Zhuravlev, Volfson Sheveleva, 1950). Specific surface area is reduced compared with that of pure zinc oxide and cements prepared from the mixed oxides are stronger (Crowell, 1929 Zhuravlev, Volfson Sheveleva, 1950). 

Emissions from sinter plants are generated from raw material handling, windbox exhaust, sinter discharge (associated sinter crushers and hot screens), and from the cooler and cold screen. The primary source of particulate emissions, mainly irons oxides, magnesium oxide, sulfur oxides, carbonaceous compounds, aliphatic hydrocarbons, and chlorides, are due to the windbox exhaust. Contaminants such as fluorides, ammonia, and arsenic may also be present. At the discharge end,... 

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... 

While the ball mills provide mechanical porphyrization of the magnesium oxide and zirconia particles, it is difficult to get particles with a smaller size than 1 mm. This prohibits sintering at lower temperatures. 

Few data are available on the hydrolysis of simple metal alkoxides of these elements. Alkoxides of alkaline and alkaline earth metals are mostly used as precursors for the preparation of complex oxides or solid oxide solutions. Commercial production of pure magnesium oxide by hydrolysis of Mg(OMe)2 with formation of transparent gel has been described [715], as well as hydrolysis of Mg(OC5H11i)2 with the following thermal treatment to produce a fine MgO powderthat sinters at low temperatures [1766]. Solutions prepared by dissolving magnesium in methoxyethanol are by far the most convenient precursors for preparation of magnesium oxide films. 

Itatani, K., Nomura, M., Kishioka, A. and Kinoshita, M., Sinterability of various high-purity magnesium oxide powders ,/. Mat. Sci., 1986 21 1429-35. 

Pure sintered magnesium oxide ceramics have little importance compared with magnesium oxide-containing refractory products. They are used as high temperature materials. 

Basic products contain varying quantities of magnesium oxide. Naturally occurring magnesite (MgC03) is used as the raw material and upon firing is converted into sintered magnesia ... 

It is well known that alumina, titania [10,11,12] and magnesium oxide [13,14] dissolve in acidic aqueous solutions and even at pH values close to the isoelectric point [15,16], In this study, it will be shown that these support surfaces were modified with promoters to increase the inertness thereof to acidic/aqueous environments, and not to stabilise the support against sintering and loss in surface area at high temperatures [17,18], This paper will deal with the modification of alumina and titania supports for cobalt based slurry phase Fischer-Tropsch catalysts to ensure the successful operation of slurry phase bubble column reactors on commercial scale,... 

Stage 4, Sintering If all of the magnesite has decomposed to magnesium oxide before it leaves the calcination zone, then the process of sintering begins. For further discussion of sintering see Section 9.2.1. 

As heated alkalies readily attack stainless steel, it was found necessary to use liners or crucibles in the above bombs. Borosilicate glass was found satisfactory up to about 450 °C. for short periods of time, but it could not be used above this temperature. Various ceramic materials were tried for possible use as containers for the sodium peroxide-superoxide mixtures. Sintered aluminum oxide and magnesium oxide were satisfactory up to 450 °C., but above this temperature the sodium oxides penetrated the sintered material and corroded the stainless steel bomb. Commercial ceramic coatings containing (as the principal components) alumina, magnesia, and titania were also tried without success at a temperature above 450 C. 

Magnesia magma. See Magnesium hydroxide Magnesia oxide fume Magnesia, sintered Magnesia usta. See Magnesium oxide... 

The working temperature of molten carbonate fuel cells is around 600-650°C. Mixed carbonate melts containing 62-70 mol% of lithium carbonate and 30-38 mol% of potassium carbonate, with compositions close to the eutectic point, are used in molten carbonate fuel cells as an electrolyte. Sometimes, sodium carbonate and other salts are added to the melts. This liquid melt is immobilized in the pores of a ceramic fine-pore matrix, made of sintered magnesium oxide or lithium aluminate powders. 

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