PHASE TRANSFORMATIONS IN CALCINATION OF NITRATES OF ALUMINUM, STAINLESS STEEL, AND NICHROME

Earlier studies showed that low concentrations of boric acid inhibit the formation of alpha alumina in the fluidized calcination of aluminum nitrate wastes. Studies designed to determine the optimum concentration of boric acid and the relative effectiveness of phosphoric acid were performed by heating synthetic mixtures at moderate pressure; results indicared that they were equally effective at the same molal concentration. Differential thermal analysis of mixtures showed that the boric acid reacted with alumina below 183 deg C. Extraction of boric acid from selected samples indicated that the B was bonded (probably in a random manner, as in glasses) to the alumina rather than to Na, Additlon of fission products was studied, and no unusual effects were found. Transformation studies on calcination of stainless steel nitrates indicate that alpha iron oxide is formed even with the addition of moderate amounts of addltives such as boric acid, phosphoric acid, aluminum nitrate, or combinations of these. Rare earths are the most effective additive found. Similar studies on nichrome wastes indicate that nickel oxide (crystalline) is formed even with additives. The studies include heating of synthetic mixtures at moderate pressure, differential thermal analysis, and use of a laboratory fluidized calciner. (auth