Powders ferrites

E. G. Visser, M. T. Johnson and P. J. van der Zaag, Proceedings of the 6th International Conference on Ferrites (ICF-6), The Japanese Society of Powder and Powder Metallurgy, Tokyo, 1992. 

Oo, and Sr ferrites mixed sulfides such as Zn—OdS and Pb—OdS and coated particles such as Ee O with Al(OH)2 or Or(OH)2. OontroUed hydrolysis of alkoxides has also been used to produce submicrometer Ti02, doped Ti02, Zr02, doped Zr02, doped Si02, SrTiO, and even cordierite powders (1,3). 

Barium carbonate of finely controlled particle size reacts in the soHd state when heated with iron oxide to form barium ferrites. Magnetically aligned barium ferrite [11138-11-7] powder can be pressed and sintered into a hard-core permanent magnet which is used in many types of small motors. Alternatively, ground up magnetic powder can be compounded into plastic strips which are used in a variety of appHances as part of the closure mechanism. 

Two or more soHd catalyst components can be mixed to produce a composite that functions as a supported catalyst. The ingredients may be mixed as wet or dry powders and pressed into tablets, roUed into spheres, or pelletized, and then activated. The promoted potassium ferrite catalysts used to dehydrogenate ethylbenzene in the manufacture of styrene or to dehydrogenate butanes in the manufacture of butenes are examples of catalysts manufactured by pelletization and calcination of physically mixed soHd components. In this case a potassium salt, iron oxide, and other ingredients are mixed, extmded, and calcined to produce the iron oxide-supported potassium ferrite catalyst. 

Anisotropic powders of ferrites have excellent cost/performance ratio, limited service temperatures, and low electrical resistance. 

Preparation and Properties of Sodium Ferrite. Mix 2 g of an iron(III) oxide powder and 20 g of anhydrous sodium carbonate in an iron crucible. Fuse the mixture on the flame of a gas burner or in a muffle furnace at 800-900 °C. Pour out the hot melt onto a glazed tile. When it solidifies, grind pieces of the melt in a mortar and spill the powder into a beaker with water. What settles onto the bottom of the beaker Write the equations of the reactions. What type of oxides does iron(III) oxide belong to Which salts hydrolyze more strongly, iron(II) or iron(III) salts What does this depend on ... 

---