溶胶-凝胶法制备Sr2FeMoO6纳米晶

本文应用溶胶-凝胶法制备了双钙钛矿结构巨磁电阻(colossal magnetoresistance)材料Sr2FeMoO6。用X射线粉晶衍射对其进行了物相鉴定,表明在1473K已经得到较好的Sr2FeMoO6产物,分析结果证明得到的产物为纳米粉末态晶体,平均粒径为39nm。磁测量表明该样品Tc高于室温且具有较大的磁电阻。     

AAO模板法自组装磁性纳米线阵列及其超顺磁性

高纯铝片在草酸溶液中经直流2次阳极氧化,得到多孔氧化铝(AAO)模板。通过扩孔、缩孔和脱模实现对模板的性能优化。通过交流沉积的方法,在AAO模板内自组装Fe磁性纳米线,形成Fe纳米点阵。扫描电子显微镜(SEM)和透射电子显微镜(TEM)图像分析表明,纳米线粗细均匀,长径比约为100。单根Fe纳米线的TEM衍射花样表明其具有单晶结构。振动样品磁强计(VSM)对纳米线的宏观磁性测量可知Fe纳米线的易磁化方向均沿线长轴方向,Fe的退磁场计算表明阵列中纳米线之间存在着磁相互作用减小了退磁场的作用。Fe纳米线阵列的Mossbauer谱表现出超顺磁性,可能是来源于组成纳米线的小晶粒的超顺磁性。     

液相还原法制备的Fe纳米颗粒-膨胀石墨电磁屏蔽材料

用液相还原法制备了Fe纳米颗粒植入膨胀石墨的抗信息泄露(电磁屏蔽)复合材料;制备过程中,膨胀石墨增强层面上生成的Fe颗粒的结晶度;络合剂酒石酸钾钠增强生成颗粒的抗氧化性,产物中铁氧化物和非晶FeB成分比例减少,复合材料铁磁性增强。其中Fe含量为30wt%时屏蔽效能最好,面密度仅为0.096 g/cm2,在300 kHz～1 GHz内可达到63～102 dB,在低频端相对纯膨胀石墨提升了8.5 dB。     

INVESTIGATION OF THE SOLID- SOLID SURFACE ADSORPTION OF Eu_2O_3 ON AMORPHOUS Al_2O_3

Solid-solid surface adsorption of Eu2O3 on amorphous Al2O3 have been investigated by Mossbauer spectroscopy, X- ray diffraction analysis and laser Raman spectra (LRS). No X-ray diffraction peak of crystalline Eu2O3 can be found for all samples studied. The LRS show that two peaks at 998 and 1051 cm-1 assigned to two-dimensional surface europium-oxygen species appear at Eu2O3 content of 18.7 wt%. The peak at 1068 cm-1 due to the surface species and another peak at 342cm-1 due to crystalline Eu2O3 content start to appear for the sample with an Eu2O3 content of 36.5 wt%. The dispersity of Eu2O3 on the surface of amorphous Al2O3 were compared with that of α-Al2O3,η-Al2O3 and SiO2 gel. The results of these studies indicate that the structure of Eu2O3 dispersed onto the support surface depend on the structure of support and that there is an inductive effect of support on the structure of the Eu2O3.     

Bi掺杂对La0.67Ca0.33MnO3化合物磁性和导电特性的影响

与La的离子半径基本相同的Bi掺杂对钙钛矿锰氧化物La0.67Ca0.33MnO3的磁性和电输运性质有显著影响。掺杂使居里温度和磁化强度单调降低，电阻率和磁电阻随掺杂量增加先得到加强，然后又随着掺杂量的继续增加而降低。掺杂量达x=0.2时，试样在5－300K温度范围内表现为半导体特性，在ρ（T）及M（T）曲线上有两个以上相变，认为是铁磁相互作用与电荷有序转变竞争的结果。     

氮化铁/膨胀石墨的穆斯堡尔谱研究

用气氛还原氮化法成功将氮化铁纳米颗粒植入膨胀石墨,制备出具有优良磁性和射频屏蔽效能的材料。XRD测量表明不同温度氮化反应,制备的材料中含铁物相有变化。用57Fe的穆斯堡尔谱,详细分析了不同反应温度下反应产物的相组分。结果表明,随着温度的上升,在400°C之前,Fe颗粒逐渐被氮化直至完全,400°C以后氮化铁中的γ-Fe4N逐渐向ε-FexN(2相似文献   

用多孔氧化铝膜为模板制备Fe磁性纳米线

铝在0．3mol／L草酸或硫酸介质中经过阳极氧化,得到不同孔径的多孔氧化铝模板,在此模板中电解沉积的Fe纳米线排布规则、有序,长径比约为150。根据测量的磁滞回线,可以看到制备的铁纳米线具有较大的磁各向异性,其垂直方向具有较高的矫顽力。     

ZnAl2O4：Cu,Mn纳米晶的光学性能研究

采用溶胶凝胶法制备了铜锰共掺的ZnAl2O4纳米晶,使用X射线衍射和光致发光对晶体的结构和光学性能进行了研究。结果表明样品具有单一的尖晶石结构,在309 nm波长光的激发下,具有438 nm、511 nm、530 nm和617nm的光发射。随退火温度的升高,红光发射强度变强,蓝光发射随Cu2＋掺杂浓的增加而变强,CIE坐标显示纳米晶的发光在白光区域。     

High Temperature LFMR in Yttrium Doped Perovskite Manganites

Porous ceramic samples of Y doped perovskite manganites were prepared. In these samples, the transition from high temperature paramagnetic insulator to low temperature ferromagnetic metal as well as the low field magnetoresistance (LFMR) effect at the low temperature is similar to that in dense samples. Opposite to that in dense samples, LFMR effect in porous sample is observed at the high temperature close to the peak of MR-T curves. The results suggest that the high temperature LFMR effect and the applicable colossal magnetoresistance (CMR) materials could be obtained by controlling the microstructures of this class of perovskite manganites.     

单晶钴颗粒的合成和磁性研究

采用水合肼还原法制备出钴纳米颗粒的团簇,通过对钴颗粒形貌及结构的分析发现钴为单晶颗粒,并存在六角和面心立方两种密排结构;探讨了溶液中钴团簇的形成机制,并对其磁性质进行了初步的研究。