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Non-stoichiometric Nd-Co substituted hexaferrites of composition Sr1−xNdxFe12(1−x)CoxO19 (x=0-0.4) were prepared by the self-propagating combustion method and subsequent heat treatments. Structural characterization of samples showed that the M-type hexagonal structure can be maintained for substitutions x<0.4 without the segregation of secondary phases on samples calcined at 1100 °C. The crystallites sizes range between 50 and 70 nm. Mössbauer spectroscopy results indicate that the iron vacancies are not evenly distributed over the lattice and that Co/Fe substitution mainly takes place in site 4f2. Magnetic measurements reveal that values of saturation magnetization MS increased from 72 to 76 Am2/kg (x=0-0.2), while coercivity Hc increased from 26.40 to 58.70 A/m (x=0-0.3). Nd-Co substitutions enhance magnetic properties in deficient iron Sr hexaferrites. 相似文献
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掺加Nd和K改性对CoO催化分解NO活性的影响 《燃料化学学报》2019,47(9):1120-1128
用水热法和共沉淀法分别制备了Nd-Co3O4催化剂,催化分解N2O。其中,水热法制备的Nd-Co3O4催化活性较高。在不同组成的Nd-Co3O4中,优化出了较高活性的0.01Nd-Co3O4催化剂,在其表面浸渍K2CO3溶液制备K改性催化剂(K/Nd-Co3O4)。用X射线衍射(XRD)、N2物理吸附、扫描电镜(SEM)、X射线光电子谱(XPS)、程序升温还原(H2-TPR)、O2程序升温脱附(O2-TPD)等技术表征催化剂结构。结果表明,Nd-Co3O4和K改性催化剂均为尖晶石结构;K改性弱化了催化剂表面Co-O键,有利于表面氧的脱除,提高了催化剂活性。有氧有水气氛350 ℃连续反应40 h,K/Nd-Co3O4催化剂上的N2O分解率超过90%,稳定性较好。 相似文献
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