Migration regularities of impurities C,O,Fe,Co and Ni and effect of crystal transition on C,O and Fe in purification of metal La by solid-state electrotransport

Migration regularities of impurities C,O,Fe,Co and Ni and the effect of crystal transition on C,O and Fe in purification of metal La by solid-state electrotransport(SSE)were studied.The impurity migration direction,removal extent and difficulty were intuitively judged by impurity residual rate distribution curve.It is indicated that major impurities Fe,Co,Ni,C and O in metal La are found to significantly migrate to anode and migration effects are much better with the increase in temperature and prolongation of time in purification of La by SSE.Impurities Fe,Co and Ni in La may be fast diffusion elements,which are very extreme to be removed,and removal difficulty is in the order of Fe<Co<Ni<O<C.When La was migrated for 100 h at 800℃by SSE,the residual rates of impurity Fe,Co,Ni,O and C are 0.25%,10.10%,40.04%,64.00%and 70.04%,respectively.The crystal transition of La,transformed from fcc crystal to bcc crystal,has significant effect on migration of interstitial impurities,and removal effect of interstitial impurities C and O can be significantly improved when purification was performed above crystal transition temperature of 865℃of La.However,there is little effect on Fe.When La was migrated at 880℃for 100 h,residual rates of impurities C and O are,respectively,19.90%and 32.67%lower than those at 820℃for 100 h,while that of Fe is lower than0.25%in both situations.Therefore,more pure metal La can be obtained through further increasing temperature,especially above crystal transition temperature of 865℃of La.

Removal and occurrence state transformation of Ti impurity in Gd metal

The interaction mechanism of B and Ti in liquid Gd metal was theoretically analyzed,and the occurrence state transformation and removal of Ti impurity were experimentally analyzed in this study.The research results indicated that the B additive reacted with the Ti impurity in liquid Gd metal to form the high-melting-point TiB_(2)at 1673 K.Owing to the low density of TiB_(2)that is far lower than that of Gd,TiB_(2)floated up to the liquid surface,and then,the Ti impurity could be effectively removed from Gd metal.Prolonging melting time and increasing B additive amount could increase Ti removal rate,but the increase in the rate slows beyond a certain duration and B content.The recommended operating parameter,melting time of 60 min and B additive content of 0.1394 wt%could reduce Ti content from 0.1534 wt%to 0.0433 wt%,and the removal rate was 71.9%.