共查询到16条相似文献,搜索用时 62 毫秒
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热解柠檬酸镁或柠檬酸钡,制备了两种介孔炭(MgC或BaC),并将其用作双电层电容器电极材料。采用氮气吸附、扫描电子显微镜和傅里叶红外光谱对所制介孔炭进行表征。结果表明:所制介孔炭孔结构与柠檬酸盐所含金属阳离子有关。其中,BaC呈典型的双峰孔径分布,最可几孔径分别为3.8nm和15nm;而MgC的孔道主要是小尺寸的介孔或微孔。通过循环伏安、恒流充放电法测试所制介孔炭作为电化学电容器电极材料时的电化学性质。测试表明,在离子液体中MgC和BaC都具有很高的比电容值,分别达到180F.g-1和171F.g-1。其中,BaC的倍率性能良好,能量密度可达到53.3Wh.kg-1,最大功率密度为20kW.kg-1。BaC优良的电容特性主要归因于其孔径双峰分布的孔结构和亲水性表面化学性质。 相似文献
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以臭氧为活化剂,炭化的米糠为原料制备出活性炭。采用氮吸附、SEM-EDAX和FT-IR对样品进行表征。活性炭的比表面积由活化前的20 m2/g增加到380 m2/g。在臭氧活化过程中,吸附在炭材料上的二氧化硅变疏松,从而导致碳逸出。臭氧同时以氧分子和原子形式存在于炭表面。氧原子,作为强氧化剂,将炭表面氧化成酸性官能团如羧基、酮基和酚基。采用该活性炭吸附Cr(VI)离子,Cr(VI)离子的最大去除率(94%)的条件为:p H值2.0、浓度100 mg/L、吸附量0.2 g,时间2.5 h及转速300 r/min。采用吸附平衡和动力学模型探讨吸附机理,结果表明,吸附等温线符合Freundlich方程,吸附速率符合准二级动力学方程。吸附是自发的放热反应,可能与Na OH脱落而恢复Cr和碳有关。 相似文献
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采用溶胶-凝胶法成功地制备了双钙钛矿结构的Sr2Fe1-xNixMoO6(x=0.0~0.4)化合物.X射线衍射实验表明,Ni的掺入没有改变化合物的晶体结构和空间群,但晶格常数随Ni含量的增加而减小,同时B位阳离子的占位有序度随Ni含量的增多而增大.研究还表明,B位阳离子的占位有序度与样品的烧结温度也有很大的关系,烧结温度升高,有序度增大.扫描电镜分析表明,所制备的样品颗粒度均匀,界面清晰,Ni的掺入使颗粒细化. 相似文献
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碳量子点具有优异的光学性质,良好的水溶性、低毒性、原料来源广、成本低、生物相容性好等诸多优点,广泛应用于发光器件、生物检测、能源存储与转换领域,但在实际应用中还存在合成过程复杂、产率低等挑战。本文以煤为原料,以甲酸和双氧水为氧化剂,在室温下可大量合成煤基发光碳点,考查了氧化剂的添加量、反应时间对煤基发光碳点的产率及反光性质的影响,结果表明煤基发光碳点产率高达54%,且具有良好的水溶性、光稳定性、耐盐性和较高的发光量子效率。制备的煤基发光碳点可用于Fe3+离子的特异性检测,检测限低于600 n mol L-1。该合成方法为煤的高附加值利用和设计开发煤基新材料提供了新途径。 相似文献
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A. Mourachkine 《Journal of Superconductivity》2001,14(5):587-597
The main purpose of the paper is to present an overview of the current situation in the development of the understanding of the mechanism of high-T
c superconductivity which arises due to moderately strong, nonlinear electron–phonon interactions and due to spin fluctuations. The former are responsible for electron pairing, and the latter mediate the phase coherence. In addition, a key experiment for superconductivity in cuprates is proposed. 相似文献
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E. P. Stoll 《Journal of Superconductivity》2004,17(1):79-84
Hole suppliers like Sr in doped La2CuO4 are mainly randomly distributed. Assuming that the holes are dislocated over a few lattice constants away from the Sr atom, the conducting areas form randomly distributed circles in the CuO2 layer planes. Conductivity and also superconductivity can occur only when these circles touch each other and form percolation clusters. Mobile holes are accompanied by diffusing d-electrons. Their spin direction is no longer localized on distinct places, and antiferromagnetism breaks down. The phase diagram of high-T
c superconductors is discussed on the basis of a modified continuum percolation model for which the centers of each circle are located on lattice points. The inhomogeneities due to the random hole distributions lead to broad peaks instead of sharp singularities in the static and dynamic response functions. 相似文献
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Superconductivity and magnetism in 11-structure iron chalcogenides in relation to the iron pnictides
This is a review of the magnetism and superconductivity in ‘11’-type Fe chalcogenides, as compared to the Fe-pnictide materials. The chalcogenides show many differences from the pnictides, as might be anticipated from their very varied chemistries. These differences include stronger renormalizations that might imply stronger correlation effects as well as different magnetic ordering patterns. Nevertheless the superconducting state and mechanism for superconductivity are apparently similar for the two classes of materials. Unanswered questions and challenges to theory are emphasized. 相似文献
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Superconductivity and magnetism in 11-structure iron chalcogenides in relation to the iron pnictides
AbstractThis is a review of the magnetism and superconductivity in ‘11’-type Fe chalcogenides, as compared to the Fe-pnictide materials. The chalcogenides show many differences from the pnictides, as might be anticipated from their very varied chemistries. These differences include stronger renormalizations that might imply stronger correlation effects as well as different magnetic ordering patterns. Nevertheless the superconducting state and mechanism for superconductivity are apparently similar for the two classes of materials. Unanswered questions and challenges to theory are emphasized. 相似文献
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D. Mihailovic 《Journal of Superconductivity》2000,13(6):951-953
A brief overview of some of main highlights of the Symposium on Localised and Itinerant States (SILS) is presented. 相似文献
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Reentrant first-order transitions are observed in thin TiN films under the paramagnetic limitation of superconductivity when the tricritical point appears on the locus of the reentrant second-order transition. 相似文献
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AbstractWe investigate the localization and superconductivity in heavily doped semiconductors. The crossover from the superconductivity in the host band to that in the impurity band is described on the basis of the disordered three-dimensional attractive Hubbard model for binary alloys. The microscopic inhomogeneity and the thermal superconducting fluctuation are taken into account using the self-consistent 1-loop order theory. The superconductor-insulator transition accompanies the crossover from the host band to the impurity band. We point out an enhancement of the critical temperature Tc around the crossover. Further localization of electron wave functions leads to the localization of Cooper pairs and induces the pseudogap. We find that both the doping compensation by additional donors and the carrier increase by additional acceptors suppress the superconductivity. A theoretical interpretation is proposed for the superconductivity in the boron-doped diamond, SiC, and Si. 相似文献