RESUMEN
The development of low-cost RE-Fe-B sintered magnets with large La/Ce content is of great significance for the balanced utilization of rare earth (RE) resources, but it is limited by reduced magnetic properties. In this work, the coercivity (Hcj ), remanence (Br ), maximum energy product [(BH)max ], and temperature stability are simultaneously enhanced for magnets with LaCe accounting for 40 wt% of the total RE. The synergistic regulation of the REFe2 phase, Ce-valence, and grain boundaries (GBs) in RE-Fe-B sintered magnets is realized for the first time by introducing appropriate La elements. The La elements inhibit the generation of the REFe2 phase and tend to stay in the triple junctions, promoting the segregation of the RE/Cu/Ga elements and contributing to the formation of Ce/Nd/Cu/Ga-rich continuous thicker lamellar GBs, and as a result, weakening the detrimental effect on HA caused by La element substitution and enhancing Hcj . In addition, partial La atoms entering the RE2 Fe14 B phase are beneficial for improving the Br and temperature stability of the magnets and promoting the Ce3+ ion ratio, which also provides additional benefit for Br . The findings provide an effective and feasible way to co-enhance the remanence and coercivity of RE-Fe-B sintered magnets with high Ce content.
RESUMEN
The in situ Mg-sialon in low-carbon MgO-C refractories was studied with respect to its oxidation behavior and mechanism at 1500 °C. The results indicated that the oxidation index and rate constant of low-carbon MgO-C refractories with Mg-sialon were 26.2% and 0.51 × 10-3 cm2/min at 1500 °C for 2 h, respectively. The formation of a dense MgO-Mg2SiO4-MgAl2O4 protective layer contributed to considerable oxidation resistance, and the generation of this thicker layer was due to the combined volume effect of Mg2SiO4 and MgAl2O4. The reduced porosity and more complex pore structure were also found in the refractories with Mg-sialon. Therefore, further oxidation was restricted as the oxygen diffusion path was effectively blocked. This work proves the potential application of Mg-sialon in improving the oxidation resistance of low-carbon MgO-C refractories.
