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Abnormal variation of magnetic properties with Ce content in(PrNdCe)_2Fe_(14)B sintered magnets prepared by dual alloy method 下载免费PDF全文
Resource-saving(PrNdCe)_2Fe_(14)B sintered magnets with nominal composition(PrNd)_(15-x)Ce_xFe_(77)B_8(x=0–10)were prepared using a dual alloy method by mixing(PrNd)_5Ce_(10)Fe_(77)B_8 with(PrNd)_(15)Fe_(77)B_8 powders. For Ce atomic percent of 1% and 2%, coercivity decreases dramatically. With further increase of Ce atomic percent, the coercivity increases, peaks at 6.38 kOe in(PrNd)_(11)Ce_4Fe_(77)B_8, and then declines gradually. The abnormal dependence of coercivity is likely related to the inhomogeneity of rare earth chemical composition in the intergranular phase, where Pr Nd concentration is strongly dependent on the additive amount of(PrNd)_5Ce_(10)Fe_(77)B_8 powders. In addition, for Ce atomic percent of 8%,7%, and 6% the coercivity is higher than that of magnets prepared by the conventional method, which shows the advantage of the dual alloy method in preparing high abundant rare earth magnets. 相似文献
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锰掺杂六铝酸镧催化剂上甲苯催化燃烧净化研究 总被引:1,自引:0,他引:1
采用共沉淀法制备了系列锰掺杂六铝酸镧LaMnxAl12-xO19催化剂。XRD表征发现,只有在锰掺杂量为2.0~2.5时,经1200 ℃焙烧处理得到的催化剂中才有完整的六铝酸盐晶相。由UV-vis漫反射、H2-TPR和BET比表面积分析表明,掺杂的锰离子主要以Mn3+形式取代六铝酸盐八面体位置的Al;同时随锰掺杂量增多,催化剂中Mn3+/Mn2+比例变大,而比表面积却相应减小。O2-TPD表征也进一步发现,随锰掺杂量增多,催化剂上化学吸附晶格氧量增加,而物理吸附氧分子量减少。在甲苯催化燃烧净化反应中,锰掺杂六铝酸镧催化剂表现出良好的低温催化活性,且锰掺杂量为2.0~2.5时活性最优。推测该反应是遵循Mars-van Krevelen机理,由Mn3+和Mn2+的协同作用共同促进晶格氧的流动性。 相似文献
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The magnetic properties of two-dimensional antiferromagnet NiGa2S4have attracted much attention and yet some problems are far from being solved. We investigate the magnetic properties of NiGa2S4by Monte Carlo simulations. A new spin-interacting model is proposed to describe the system, and the specific heat together with the doping effect of nonmagnetic impurity is studied by simulations. The double peaks of the specific heat as well as other behaviors are well reproduced. We also compare our results with those of other models, and the underlying physics is discussed. 相似文献
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实验测量了0.75 MeV的O5+离子穿过一定长度不同原子数密度H2靶后的电荷态分布;理论模拟了出射离子的平均电荷态以及达到平衡后的平均电荷态,得到了与实验吻合较好的结果。研究表明,随着靶原子数密度的增大,离子在碰撞过程中俘获电子的几率随之增加,平均电荷态降低;当靶原子数密度达到或超过1014 cm-3,入射离子俘获电子和被碰撞电离的两个作用过程达到平衡,出射离子的平衡平均电荷态约为1.2。 相似文献