Shortening the decomposition time for sintered alumina by high-temperature pressure acid decomposition

A high-temperature pressure acid decomposition was examined to shorten the, time required to decompose alumina for the analysis of impurities with ICP-AES. The sample and sulfuric acid were heated below 290 degreesC in a PTFE-15% graphite vessel. In the case of raw material powder samples, the decomposition time was not always shortened by applying high-temperature to the decomposition. The times required to decompose several products of sintered samples at 290 degreesC were reduced to 1/2 similar to 1/7 of those at 230 degreesC without any significant increase in the contamination, except. for Si. The analytical results of Si in the ICP-AES for solutions obtained with 290 degreesC decomposition were higher than those obtained with 230 degreesC decomposition. For the most part, the excess Si was attributed to Si from the quartz ICP torch being attacked by a higher concentration of fluoride ion produced from the PTFE vessels under high-temperature conditions.