Issue 37

Q. Like et alii, Frattura ed Integrità Strutturale, 37 (2016) 342-351; DOI: 10.3221/IGF-ESIS.37.45 349 of galena at different irradiation times are similar; however, the number of microcracks in circular galena is smaller after 0.004 s. The relation curves between the number of microcracks in calcite and boundary damage rate and irradiation time under different shapes of galena are shown in Figs. 13 and 14. The growth of boundary damage rate and the number of microcracks in calcite can be divided into two stages. The first stage is from 0 s to 0.0035 s when the number of cracks in calcite increases quickly (ranging 490–512), and the boundary damage rate varies within 51%–55%. This rapid increase reflects the insignificance of galena shape. The second stage starts from 0.0035 s when the number of microcracks in calcite remains the same, indicating that the microcracks in minerals after 0.0035 s occur mainly in the galena, causing the useful minerals to become too broken against mineral separation. Figure 11 : Relation curves between the total number of microcracks and irradiation time. Figure 12 : Relation curves between the number of microcracks in galena and irradiation time. Figure 13 : Relation curves between the number of microcracks in calcite and irradiation time. Figure 14 : Relation curves between boundary damage rate and irradiation time. The first stage under high-power microwave irradiation can be used as the optimum irradiation time. The number of microcracks in calcite and boundary damage rate increase quickly within the optimum irradiation time. The total numbers of microcracks are similar for different shapes of galena, indicating that mineral shape will not affect mineral dissociation. However, once irradiation time exceeds the optimum range, microcracks in useful minerals will continue to increase, whereas the number of microcracks in calcite and the boundary damage rate remain the same. Thus, long irradiation time is disadvantageous for mineral dissociation.