Abstract
Magnesium aluminate (MA) spinel is synthesized by reaction sintering from alumina and magnesia. The effects of mechanical activation of Al2O3 on reaction sintering were investigated. Non-milled a - Al2O3 and a - Al2O3 high-energy ball milled for 12h, 24h and 36h were mixed with a MgO analytical reagent according to the stoichiometric MA ratio, respectively and pressed into billets with diameters of 20mm and height of 15mm. The green-body billets were then sintered at high temperature in an air atmosphere. The results show that bulk density, relative content of MA and grain size of MA increase with increasing high-energy ball milling time of Al2O3. However prolonged milling time over 24h has a small beneficial effect on the densification of MA. Bulk density and grain size of a sample of a- Al2O3 milled for 24h are 3.30g/cm3 and 4-5 mm, respectively.
Highlights
Magnesium aluminate spinel (MA), which is the only stable compound in the MgOAl2O3 system, possesses a high melting point (2135oC), good mechanical strength and excellent chemical resistance etc. [1,2,3]
The milling time of α- Al2O3 had a great effect on the densification of MA
The grain size of MA increases with increasing milling time of Al2O3 but prolonged milling time over 24h had little beneficial effect on the growth of MA
Summary
Magnesium aluminate spinel (MA), which is the only stable compound in the MgOAl2O3 system, possesses a high melting point (2135oC), good mechanical strength and excellent chemical resistance etc. [1,2,3]. To obtain a dense reaction sintered body, researchers have studied several other processes such as freeze drying [7], sol-gel of metal alkoxides or inorganic [8], hydroxide coprecipitation [9] etc. These chemical processes have some intrinsic disadvantages. Some authors report that some systems can react during high-energy ball milling [16] At present, this method has been successfully used to synthesize a wide range of nano-sized ceramic powders and has become one of the most promising methods of promotion of multi-component system reactions. We will study the synthesis and densification of MA from MgO and Al2O3 that was treated by a high-energy ball milling process for different times
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