James M. Buchanan: An appreciation

A review on magnesium aluminate (MgAl2O4) spinel: synthesis, processing and applications

“…MgAl 2 O 4 spinel ceramics with ∼95% of the TD were considered to be suitable for certain applications, qualifying DP, GD and GCHAS as promising powder processing routes for MAS ceramics. 24 Table 4 confirms that the MAS ceramics consolidated by the present colloidal processing routes exhibit better mechanical properties (hardness and three point bend strength) in comparison to those prepared by the other shaping techniques. 194 The LS upon sintering of these MAS ceramics did not exceed 18·5%, being within the safety range for net shaped fabrication of thin wall components devoid of any defect.…”

“…Since natural occurrence is little, MAS is synthesised artificially. 24 There are several soft solution chemistry routes, such as coprecipitation, spray drying, freeze drying and spray pyrolysis by which MAS can be synthesised at par low temperatures. However, none of these processes is suitable for manufacturing of MAS in bulk quantity for applications such as refractories.…”

“…Alternatively, a single stage firing process called electrofusion technique is also employed to prepare high purity MAS. 24,63 In this process, the mixture of calcined alumina and natural magnesite is melted in an electric arc furnace. High temperature generated in this process volatilises impurities.…”

“…Nevertheless, this process is quite energy intensive and not viable to practice by many of the countries where electricity is expensive for many of the refractory applications. 24 In another alternative single stage firing process, Sarkar et al 47 prepared dense MAS grains with a theoretical density (TD) of 99·5% at 1600°C. In this process, an attritor milling was utilised for 6 h to reduce the particle size of starting raw materials mixtures.…”

“…23 Given its high melting point and high chemical inertness, MAS has been employed to replace traditional chromite based refractories in cement rotary kilns and steel ladles, since the latter refractories contain Cr(VI) species, which create both environmental and health hazards. 1,24 Thin films of MAS exhibited potential utility in thermal barrier coatings (TBCs) for the blades and vanes in the hot section components of gas turbines. 25 Furthermore, MAS has also been employed as an alternative material to replace the conventional carbon anode in aluminium electrolytic cells.…”