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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

Additional file 1. Table S1. Comparison of the major symptoms of the 37 test-retested IBD patients (16 with CD and 21 with UC).

In view of the previous studies on the migrations of impurity aluminum (Al) and copper (Cu) in purification of rare earth metal by solid-state electrotransport (SSE), there are still some questions about that which direction they migrate to and whether there are significant migrations or not. The metal lanthanum (La) was used as research object, and the effects of migration temperature and time on the distributions and migration regularities of impurity Al and Cu were investigated in the present study by increasing concentration of impurity Al and Cu in raw metal La. The impurity migration direction and removal difficulty were intuitively judged by the residual rate distribution curve of impurity. It is indicated that metal impurity Al and Cu in metal La at 800 °C with direct current are found to significantly migrate to anode and their residual rates near cathode decrease with the increase in migration temperature and prolongation of migration time. The relatively large vapor pressure of Al and Cu makes their residual rate distribution curves being low in middle and high in ends. When metal La was continuously purified for 100 h at 800 °C by SSE, the residual rates of impurity Al and Cu at 20 mm from cathode are 68.43% and 57.43%, respectively, showing that Cu is much easier to be removed than Al.

In order to solve the problem of large temperature difference between the center and ends of the metallic rod in the purification process of solid-state electrotransport (SSE), three types of electrode connections of tantalum and the corresponding rods of metallic lanthanum were designed, the temperature distributions of three kinds of rod were measured, and the influence of temperature difference on the purification effect of solid-state electrotransport was investigated. The results indicate that the maximum temperature difference of the rod will be significantly reduced through decreasing the cross section of electrode connection to make its unit length resistance close to that of rod, or increasing the unit length resistance of the section at both ends of the rod. When these two measures are adopted at the same time, the effect of decreasing rod temperature difference is the best in the present study, and the maximum temperature difference of the rod can be reduced to 29 °C when the maximum temperature of the rod is 820 °C. The migration velocity of the impurities at rod ends can be obviously improved after the rod temperature difference is reduced, which enables the purification effect and efficiency of solid-state electrotransport to be greatly raised; it is also found that the major impurities iron in metallic lanthanum migrates more easily than oxygen and carbon during the purification of metal lanthanum with solid-state electrotransport.

The high purity erbium (Er) with purity ≥ 99.9% was rolled with accumulated deformation of 80%, and the deformed high purity Er was annealed at different temperatures. The microstructure and properties of deformed high purity Er during annealing were studied by means of electron back-scatter diffraction (EBSD) and microhardness tester, respectively. Experimental results showed that after annealing, the deformed microstructure was replaced by fine equiaxed grains. The microstructure and grain orientation distributed were most homogeneously when annealing temperature was 570 °C. And the recrystallization grains component increased with the annealing temperatures increased until 570 °C. After annealing progress, there was a progressive reduction of Low-Angle Grain Boundaries (LAGBs) fraction and a subsequent increase in High-Angle Grain Boundaries (HAGBs). The microhardness of rolled samples was higher than annealed samples, and decreased with increase of the temperatures due to the recovery, recrystallization and grain growth of the Er metal when the annealing temperature less than 570 °C. The microhardness increased a little after annealing at 620 °C. The optimum annealing temperature was 570 °C for high purity Er metal with 80% rolling deformation.