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1991年5月,Bell实验室的A.F.Hebard等人首次在掺钾的C60中观察到高达18K的超导电性.于是,这项研究结果在全世界掀起广泛的研究热潮,成为近年高温超导研究领域中又一热点.本文扼要介绍C60掺杂实验的物性测量结果,引起C60超导的几种可能机制及对C60掺杂研究的意义.一、AxC60的掺杂实验及物性测量结果Hebard等人发现掺钾的C60高达18K的超导电性是在9GHz频率下,用微波损耗测量样品的电阻率随温度的变化时观察到的.当样品冷却到约20K时,电阻率略有增加,后又降低,直到5K时电阻率降为零.超导转变宽度为4.6K,4K时临界电流密度为40A/cm2.用SQUID磁强计测量证明了它的超导转变为18K. 相似文献
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铜(Ⅰ)基金属卤化物作为新一代环境友好的发光材料受到了研究者的广泛关注。本文采用溶剂辅助结晶法设计制备了一种新型零维金属卤化物发光材料(C12H24O6)NaCuBr2。在365 nm激发下,该化合物呈现出半峰宽为346 nm的超宽带橙红色发射,光致发光量子产率为42.6%。基于低温光谱、激发波长依赖的发射光谱和理论计算研究表明,峰值700 nm处的超宽带发射来自于Cu+离子3d轨道和Br-离子4p轨道间相互作用形成的简并能级。在低温下,(C12H24O6)NaCuBr2的晶格畸变导致能级的简并度降低,其荧光发射包含峰值为629 nm和735 nm的两个发射带。在高能激发下,电子跃迁到(C12H24O6)NaCuBr2的更高能级S3而带来的发射与77 K下观测到... 相似文献
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CF3I作为SF6最具潜力的新型环保绝缘气体,在电气设备出现局部放电、过热等缺陷故障时,会产生C2F6和C2F4等强温室气体,为确保电力设备稳定运行,有必要对CF3I典型分解组分吸附去除.本文基于密度泛函理论的第一性原理计算方法,通过吸附能、吸附距离、电荷转移和态密度等吸附指标,分别探究了不同数量Pt掺杂MoSe2对C2F6和C2F4气体分子的吸附性能.研究结果表明:不同数量Pt掺杂在MoSe2表面均存在稳定的掺杂结构,且相较本征MoSe2,Pt掺杂后的MoSe2导电性均得到了有效增强;Pt掺杂MoSe2对CF3I分解组分的吸附效果:Pt2-MoSe2>Pt-MoSe<... 相似文献
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在铜基金属卤化物Cs3Cu2I5中掺杂Mn2+是拓宽发光范围的重要途径,但是已报道的掺杂方法大多需要高温、惰性气氛、较长时间和专用设备等。本工作将CsI固体粉末直接投加至CuI和MnCl2的氢碘酸溶液中,在较低温度(60℃)、空气条件下快速(3 min)合成Mn2+掺杂Cs3Cu2I5微晶,并测试了其结构和发光性能。通过系列对比实验,提出一种由反应物溶解度控制的“缓释生长-掺杂”机制,证实CsI固体粉末在高浓度氢碘酸中的缓慢溶解能够降低Cs3Cu2I5晶体的生长速率,为Mn2+的低温、可控掺杂提供有利的动力学条件。该方法为全无机金属卤化物体系的掺杂发光和掺杂动力学研究提供了新的思路。 相似文献
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在200 keV重离子加速器上,用120—360 keV的H,N,Ar和Mo离子注入C60薄膜.对注入后薄膜的拉曼谱进行了分析.结果表明,不同离子注入C60薄膜后,C60的1469 cm-1特征峰随注入剂量的增加均呈指数式下降,同时在1300—1700 cm-1范围出现非晶碳峰,并逐渐增强,最终完全非晶化.而且1469 cm-1拉曼峰的强度及C60薄膜完全非晶化所对应的剂量与注入离子的种类和能量有关.进一步的分析表明,C60分子的损伤主要是由注入离子的核能量转移所造成,与电子能量转移无关.H离子注入C60薄膜后,1469 cm-1处特征拉曼峰向短波方向非对称展宽,这可能是注入的H离子通过电子能量转移使C60分子发生聚合的结果.
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Yu. V. Lavskaya A. V. Okotrub L. G. Bulusheva E. M. Pazhetnov A. I. Boronin N. I. Denisenko O. V. Boltalina 《Physics of the Solid State》2007,49(6):1195-1200
The structure of the fullerence fluoride C60F24 of the T h symmetry contains two types of chemically different carbon atoms, namely, atoms of isolated double bonds and atoms of CF groups. X-ray photoelectron and x-ray emission spectroscopic studies of C60F24 revealed a difference in the widths of the x-ray bands corresponding to these types of atoms. Nonempirical quantum-chemical calculations performed for C59NF 24 + ions with a hole in the C 1s core level of the fullerence fluoride showed that the difference in the bandwidths may be due to the fact that the vibrational states of the system are different when 1s electrons are removed from chemically nonequivalent atoms. 相似文献
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We report enhanced and broad-band photoluminescence (PL) behavior of C60 doped in porous silica glasses. By carrying out photoluminescence and photoluminescence-excitation spectroscopy of C60 doped in surface-unpassivated and -passivated porous glasses, we show that the interaction of C60 with the silica surface is quite strong and that the modified C60 molecules contribute only in the orange-red region (∼1.9 eV) of the observed PL spectrum. The PL intensity in the blue-green
region (∼2.3 eV) observed in doped glasses is found to originate in the porous glass itself.
Received: 13 July 2000 / Revised version: 24 January 2001 / Published online: 9 May 2001 相似文献
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《Solid State Communications》2002,121(6-7):367-370
We report on 13C and 19F nuclear magnetic resonance study of acceptor doped fullerenes showing p-type semiconductor behavior. Room temperature 19F spectra are characteristic for rotating (MF6−) complexes, while the 13C spectra show that fullerene molecules are not mobile at temperatures up to 365 K. Reduction of the 13C chemical shielding anisotropy of (MF6)2C60 in comparison to solid C60 is assigned to the charge transfer between C60 and intercalated species. 相似文献
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A. M. Tan I. S. Sidorov S. É. Putilin I. Yu. Sapurina N. V. Kamanina 《Technical Physics》2007,52(11):1515-1518
The nonlinear transmission of the liquid crystal-conductive polymer (polyaniline)-fullerence (C60) system in the near-infrared spectral region at 1080 and 805 nm is considered for the first time. The output radiation intensity is studied as a function of the fullerence concentration and the energy density of the incident radiation in the nano- and femtosecond scales. The experimental results are explained by the formation of an organic donor-fullerene complex, as well as by possible absorption of fullerence C60 at the 1 6-eV transition, which is forbidden in pure fullerene structures. 相似文献
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Ch. Venkata Reddy Ch. Rama Krishna T. Raghavendra Rao D.V. Sathish P.S. Rao R.V.S.S.N. Ravikumar 《Journal of luminescence》2012,132(9):2325-2329
Co2+ and Ni2+ ions doped β-BaB2O4 nanopowders have been prepared by co-precipitation method and their structural properties are studied by spectroscopic techniques. Powder XRD data reveals that the crystal structure belongs to monoclinic and the average crystallite size is calculated. Optical absorption spectra data reveal octahedral site symmetry for Co2+ and Ni2+ ions. Crystal field (Dq) and inter-electron repulsion (B and C) parameters are evaluated for Co2+ doped β-BaB2O4 nanopowders as Dq=960, B=900 and C=3850 cm?1 and for Ni2+ doped β-BaB2O4 nanopowders, Dq=900, B=850 and C=3500 cm?1. FT-IR spectra showed the characteristic vibrational bands related to BO3 and BO4 molecules. Photoluminescence spectra contain the emission bands in ultraviolet and blue regions. 相似文献
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Sharad D. Bhagat 《Applied Surface Science》2006,252(12):4289-4297
The present paper describes the comparative studies on the hydrophobic and physical properties of the tetraethoxysilane (TEOS) based silica aerogels prepared by two step sol-gel process followed by supercritical drying. Silica alcogels were prepared by keeping the molar ratio of TEOS:methanol (MeOH):H2O (acidic):H2O (basic) constant at 1:33:3.5:3.5 with oxalic acid and ammonium hydroxide concentrations fixed at 0.001 and 1 M, respectively. In all, nine different co-precursors (CP) of the type RnSiX4 − n, have been used. The aerogels have been characterized by density, porosity, percentage of volume shrinkage, optical transmission, contact angle and thermal conductivity measurements. The surface chemical modification of silica aerogels was confirmed by the presence of CH and SiC peaks at 2900, 1450 and 840 cm−1, respectively, from the Fourier transform-infrared spectroscopy (FT-IR). The microstructure of the aerogels was studied using transmission electron microscopy (TEM) and scanning electron microscopy (SEM) techniques. In addition to these studies, the stability of the hydrophobic aerogels against an organic impurity (methanol, in the present studies) in water has also been studied. 相似文献
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H.A.A. Seed Ahmed O.M. Ntwaeaborwa M.A. Gusowski J.R. Botha R.E. Kroon 《Physica B: Condensed Matter》2012,407(10):1653-1655
Amorphous silica samples doped with 0.1 and 1 mol% of terbium (Tb) were synthesized by the sol–gel method. In addition to the green light associated with 5D4→7FJ transitions of Tb3+, the sample containing 0.1 mol% also emitted blue light as a result of 5D3→7FJ transitions during photoluminescence (PL) measurements. As a result of concentration quenching this blue emission was not observed for the samples doped with the higher concentration (1 mol%). However the blue 5D3 →7FJ emission was observed in the 1 mol% doped samples during cathodoluminescence (CL) measurements. Since a rough calculation indicated that the excitation rate in the CL system where the blue emission is observed may be similar to a laser PL system under conditions where the blue emission is not observed, the difference is attributed to the nature of the excitation sources. It is suggested that during the CL excitation incident electrons can reduce non-luminescent Tb4+ ions in the silica, substituting for Si4+ ions, to the excited (Tb3+)? state and that these are responsible for the blue emission, which does not occur during PL excitation. 相似文献
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采用改进化学汽相沉积结合溶液掺杂法制备了掺镱石英光纤预制棒,并研究了不同镱掺杂浓度下的吸收光谱和发光光谱.吸收光谱和发光光谱的强度随着YbCl3溶液浓度的增大而增强.在不产生失透的前提下,得到预制棒芯层能够掺杂的YbCl3溶液最大浓度为0.057 mol/L. 相似文献
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The charge transfer compound TDAE-C60 (TDAE — tetrakis-dimethylamino-ethylene) is so far the only known C60 based molecular ferromagnet. The ESR spectra of TDAE-C60 single crystals demonstrate that freshly grown regularly shaped single crystals show at first an AFM (antiferromagnetic)-like behavior which changes upon annealing at room temperature in vacuum to a FM (ferromagnetic) one. It thus seems that annealing induces a change in the relative orientation of the distorted C 60 ? ions resulting in a change in the sign of the effective magnetic interactions between neighboring C 60 ? ions. A structural transition in the TDAE methyl protons at 250 K seems to be connected with this process. Here we review the structure, the ESR spectra, the proton NMR spectra and the13C NMR spectra of TDAE-C60. 相似文献