Weiran Zhu,Nan Hao,Chen Chen,Yu Qiu,Yanli Zuo,Jie Wei,Jing Qian,Kun Wang
The performance-enhancing strategy of a single pathway for perovskite has been widely studied. In this work, the dual-pathway strategy of A-site Ce substitution and nitric acid selective dissolution was proposed. The catalytic oxidation performance of LaMnO3 exhibits the characteristic of hierarchical regulation, that is, a steplike improvement, which avoids the limitation of performance improvement of the single pathway. The B-site Mn with catalytic activity was in situ reconstituted on the surface to build a Mn-rich surface. The obtained sdLa0.7Ce0.3MnO3 has the advantages of good oxygen mobility, high Mn4+/Mn3+ molar ratio, and large specific surface area, and this material showed excellent catalytic oxidation performance for organics, which can realize colorimetric chemical oxygen demand detection at room temperature. Here, Ce substitution improved the oxidation capacity by improving the oxygen mobility and the ratio of Mn4+/Mn3+, and further nitric acid treatment not only accelerated the in situ reconstruction of B-site Mn but also increased the specific surface area.
Xiaoyun Shang,Xiangming Wang,Min Chen,Haoran Tu,Hongguo Zhang,Ming Yue,Xiaobo Du
To balance the utilization of rare-earth resources and reduce the preparation cost, the La and Ce substituted Nd 2 Fe 14 C hard magnetic alloys were prepared by a facile mechanochemical method for the first time. A two-step process is typically employed: 1) Decomposition of hydrocarbon and disproportionation of (Nd 1-x RE x ) 2.5 Fe 14 B 0.08 (RE=La or Ce, x=0–0.3) alloys during high-energy ball milling, Nd+Nd 2 Fe 17 +n-hexane→NdH 2+δ +α-Fe+Fe 7 C 3 ; 2) (Nd, RE) 2 Fe 14 C hard magnetic powders were obtained via the vacuum annealing at 800 °C for 2 min. The phase relation, magnetic properties and microstructural evolution of (Nd, RE) 2 Fe 14 B 0.08 C 0.92 (named Nd-RE-Fe-C-based) alloys were systematically investigated. Substitution of La for x=0.1 Nd in the Nd-RE-Fe-C-based alloy increase the coercivity from 15.6 kOe to 18.6 kOe without reducing the remanence. First-principles calculation was performed to study the mechanism of magnetic properties La and Ce substituted samples. The results showed that La tends to be expelled from 2:14:1 phase to form more minor phases which act as the domain wall pinning center, increasing the coercivity. However, Ce prefers to enter the 2:14:1 phase, diminishing the permanent magnetic properties due to the poor intrinsic magnetic properties. This paper provides a novel viewpoint for the effective utilization of high abundant rare earth and the investigation of low cost Nd 2 Fe 14 C permanent magnet materials.
危险品化学品经营许可证（带存储）