共查询到16条相似文献,搜索用时 62 毫秒
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测量了Cu Al混合粉末经过不同时间球磨后的27Al核磁共振(NMR)谱,分析了27AlNMR谱的特征参量随球磨时间的变化.根据27AlNMR谱所提供的信息,研究了Cu Al混合粉末机械合金化反应的微观过程.Cu Al混合粉末的27AlKnight位移随球磨时间的增加而减小.对于Cu Al混合粉末,球磨不仅改变了27Al附近的化学短程序,而且也直接地影响了27Al的外层电子态,后者使传导电子的s态成分减小.实验结果表明,Cu Al混合粉末在球磨过程中发生了真正的合金化反应;经过90h球磨完成了合金化反应;
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对射频共溅射法制备的FeAl2O3颗粒膜的隧道巨磁电阻效应进行了研究.当Fe体积百分比为45%时,样品的室温磁电阻的变化率(MR)在1T的平行膜面的磁场下可达44%.磁测量表明在室温时样品呈超顺磁态.另外,从MR随温度的变化关系曲线可以看出,当温度低于50K时,MR随着温度的下降而显著增加,MR在20K时达到149%,42K时可达26%,大大超过理论的预期值,这可能与低温下由库仑抑制效应引起的自旋相关隧穿的高阶效应有关. 相似文献
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E. Paparazzo J.L. Dormann D. Fiorani 《Journal of Electron Spectroscopy and Related Phenomena》1985,36(1):77-91
X-ray photoemission Spectroscopy (XPS) results are presented which have given a direct insight into the surface composition of Fe-Al2 O3 “granular” thin films consisting of fine iron particles (φ ~ 40–150 Å) dispersed in an insulating alumina matrix. The data are mainly discussed in relation to: (i) the bulk iron content in the sample, (ii) the sample preparation procedure (e.g., by rotation of the sample target) and (iii) the mean iron particle size.At the surface, the iron is in a fully oxidized 3+ state within an alumina-rich partly hydrated region. Depth analysis, achieved by an Ar+ etching procedure, provides evidence of metallic iron and iron aluminate forms. In general, the metallic iron percentage increases with depth and with increasing iron bulk content.Good agreement is found between X-ray photoemission spectroscopy and Mössbauer Spectroscopy data. Fe2+ aluminate forms, which indicate an interaction between the metal particle and the alumina matrix, show increasing percentages with decreasing mean particle sizes.Particular attention is paid to evaluating the accuracy of XPS quantitative results, obtained by use of a first-principles model, and to assessing the importance of the artefacts associated with the Ar+ etching procedure. 相似文献
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Lin Zhu Jining HeDianran Yan Yanchun DongJianxin Zhang Xiangzhi LiHanlin Liao 《Applied Surface Science》2011,257(23):10282-10288
In the present study, Fe-Al2O3-FeAl2O4 composite coatings were successfully deposited by reactive plasma sprayed Al/Fe2O3 agglomerated powder. Phase composition and microstructure of the coatings were determined by XRD and SEM. The results indicated that the composite coatings were principally composed of three different phases, i.e. FeAl2O4 phase as main framework, dispersed ball-like Fe-rich phase, and small splats of Al2O3 phase, and it was thought that the in situ synthesized metal phase was helpful to toughen the coating matrix. According to the results of the indentation and frictional wear tests, the composite coating exhibited excellent toughness and anti-friction properties in comparison with conventional Al2O3 monophase coating, though its microhardness value was a little lower than that of Al2O3 coating. The formation mechanism and the toughening mechanism of the composite coating were clarified in detail. 相似文献
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通过制备(YBa2Cu3O7)1-x(V2O5)x(0≤x≤0.15)复合材料,获得了一系列典型的弱连接的颗粒超导体,其中以dR/dT-T关系中呈现出双峰转变为主要特征。第一峰代表晶粒的超导转变,第二峰代表颗粒系统超导长程序的形成。对于具有双峰转变的样品,其临界电流密度一致地符合ic~(1-t)n,n=1.6.这一行为与三维Josephson结网络系统的渗流行为相一致;对于不具有双峰转变的系统,临界电流密度随温度的变化尽管也可以用jc~(1-t)n描述,但是幂指数n明显地大于1.6,且随样品的不同而离散地分布。本文还对产生这种离散的原因进行探索和分析。
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A method for determination of the oxygen content (y) in YBa2Cu3O7-y films has been established, in which the lattice conetant difference (b-a) of the films was measured and used to fit the function of (b-a) vs y for the experimental data of bulk YBaaCuaO?-y given in the literature. It is suggested that the function of (b-a) vs y can indeed be used in the case of film. In this process the twin structure of the YBa2Cu3O7-y films was used. 相似文献