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利用电泳技术在高熔点金属基底Ta,Mo和W上制备MgB2 超导厚膜 .厚膜中的MgB2 晶粒结合紧密 ,粒度小于1μm ,呈随机取向生长 .电阻测量表明沉积在Ta ,Mo,W上的MgB2 厚膜的超导起始转变温度分别为 3 6.5K ,3 4.8K ,3 3 .4K ,对应的转变宽度为 0 .3K ,1.5K和 2 .0K .三种基底上制备的MgB2 厚膜的临界电流密度在不同温度下随外磁场的变化情况基本相同 ,MgB2 Mo厚膜的临界电流密度在 5K ,1T时可达 1.2× 10 5A cm2 .本工艺可以随意控制膜的厚度、形状、大小 ,也可进行双面沉积 ,且制备出的MgB2 厚膜的超导性能优良 ,为MgB2 超导体的实用化提供了可能 相似文献
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采用粉末管套法,在不锈钢、铜和铝非铁磁性金属管套中制备了MgB2超导带材。电阻温度特性测量表明,以不锈钢管为包套制备的MgB2超导带材具备较好的电输运性能:临界转变温度最高(Tc=33.7K)、转变宽度最窄(零电阻转变ΔTc=1.2K,完全抗磁转变Tm=1.9K)。XRD测量显示,三种管套都能够使MgB2良好成相,MgB2和MgO相的相含量比例R(SS、Cu、A l)分别为7.15、2.45、3.77,样品中MgO相应该是Mg和管套中残余的氧反应的结果,铜管和铝管中还分别检测到了Cu2Mg和A l3Mg2相。对不锈钢管套MgB2带材的热导率测量显示,在超导转变温度以下热输运能力单调下降,满足多晶导体内热运动随温度变化的理论结果。 相似文献
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本文报道了利用化学气相沉积技术制备MgB2超导薄膜.首先在MgO(111)基片上化学气相沉积一层B膜,然后在Mg蒸气环境下对B膜进行后退火处理.退火后得到的MgB2薄膜在MgO(111)基片上呈随即取向生长,Mg、B原子比接近于1∶2.4;薄膜表面光滑致密,晶粒粒度约为0.5μm.电阻测量和直流磁测量表明薄膜超导转变温度为38K,转变宽度仅为0.1K.毕恩公式计算结果显示MgB2薄膜的临界电流密度在0T、10K时高达2×107A/cm2. 相似文献
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报道了用两步法制备MgB2超导薄膜.首先利用脉冲激光沉积技术制备B膜,然后在Mg蒸气环境下对B膜进行后退火处理,通过扩散反应生成MgB2超导薄膜.采用扫描电子显微镜、x射线衍射、电阻测量和磁测量技术分析了前驱物B膜的制备温度对扩散产物MgB2薄膜的表面形貌、晶体结构、超导转变温度和临界电流密度的影响.结果表明,随着B膜制备温度的降低,MgB2薄膜中晶粒粒度减小、c取向的衍射线宽化、超导转变温度升高、临界电流密度增大.300℃时制备的MgB2超导薄膜的超导起始转变温度为395K,临界电流密度为13×107A
关键词:
MgB2超导薄膜
脉冲激光沉积
基片温度 相似文献
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电阻型超导限流器主要利用超导带材在失超后的电阻抑制故障电流值,目前一般采用不锈钢加强的ReBCO超导材料。由于涂层导体的银、铜稳定层对其电阻率的影响较大,尤其在低温段的影响尤为显著,成为影响超导带材在电流冲击后响应过程的主要因素。实验表明,超导带材可承载的冲击电流幅值随持续时间延长而迅速降低,不锈钢加强层厚度的增大有利于超导带材耐冲击电流水平的增加。因此,交流超导限流器应适当选用加强层较厚的超导带材,而直流超导限流器应选择具有铜稳定层及适当减小不锈钢加强层厚度的超导带材。 相似文献
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A review of schemes for multiple access in fiber optic networks shows that a hybrid of wavelength and code division multiple access (WCDMA) combines the best features of both. In particular, the hybrid scheme retains the large information carrying capacity of wavelength division multiple access (WDMA) and flexibility of code division multiple access (CDMA). In this paper WDMA, optical CDMA (OCDMA), and WCDMA networks are discussed. In OCDMA networks, concept of incoherent and coherent coding including inverse decoding and matched filter is introduced. The delay performance of both WDMA and WCDMA networks, under the simple suboptimum access protocols based on cyclic search, is computed. It has been shown quantitatively that tuning delay significantly affects the delay performance of both WDMA and WCDMA networks. Futhermore, delay performance of WCDMA networks is always better than the WDMA networks for the same tuning delay, load, and number of users. 相似文献
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Guided-Wave Two-Dimensional Acousto-Optic Scanner Using Proton-Exchanged Lithium Niobate Waveguide 总被引:1,自引:0,他引:1
Two-dimensional scanning of a 0.6328 mum guided-light beam has been realized using noncolinear acousto-optic (AO) coplanar Bragg diffraction together with colinear AO guided-mode to substrate radiation-mode conversion in a Z-cut Xpropagation LiNbO3 proton-exchanged (PE) waveguide. The two surface acoustic (SAW) waves utilized are at the center frequencies of 500 and 200 MHz, propagating in the Y and X axes, respectively. Two-dimensional scanning of approximately 720 resolvable light beam spots, namely, 18 40 (horizontal vertical) scanning, has been demonstrated using a light beam of 1.0 mm aperture. The total number of resolvable beam spots can be greatly increased from 720 by simply utilizing SAW transducers of larger bandwidth and a light beam of greater aperture. It should also be possible to significantly increase the diffraction efficiency from 3 % by optimizing the parameters of the PE waveguide and the SAWs. 相似文献
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A simple technique of pulse compression, based on the linear chirp compensation of self-phase modulation (SPM) spectra in dispersion shifted fibers, is demonstrated. The optimization procedure is carried out, for a short span of a single-mode fiber, using a parabolic law, which describes the behavior of the squared output pulse width versus the pump peak power in the case of Gaussian pulses. The experimental results give a minimum pulse duration of 233 fs, which is in good agreement with the model. Shorter and coherent pulses, down to 90 fs, have been obtained by inserting an interference filter at the optical output. 相似文献
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S. G. Nedel’ko M. A. Krysyuk A. L. Apanasenko L. N. Lymarenko Z. T. Moroz 《Journal of Applied Spectroscopy》1997,64(1):55-61
Results of a study of the effect of γ-radiation on the spectral luminescence properties of cadmium tungstate crystals doped
with silver, bismuth, and molybdenum cations are presented. Spectral characteristics of the nondnnnoped crystals are briefly
described. Absorption and photo and X-ray luminescence spectra of the crystals taken before and after exposure to γ-radiation
(5.5·104 Gy) are compared. It is found that the spectral characteristics of the crystals doped with silver, bismuth, and molybdenum
cations do not change markedly after the exposure. The relation between the type of impurity-induced defects, individual characteristics
of the impurity cations, and the character of the effect of γ-radiation on the spectral luminescence properties of impure
crystals is analyzed (preliminarily).
Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 64, No. 1, pp. 55–60, January–February, 1997. 相似文献
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References: 《声学学报:英文版》2008,27(1):23-33
The performance of port/starboard discrimination of dual-line array will be seriously degraded when the space between the two line arrays of the dual-line array is mismatched. The directivity function of the delay-sum and delay-subtract beamforming is deduced and the port/starboard discrimination of the delay-sum and delay-subtract beamforming is also studied both under the ideal status and the status under which the space between the two line arrays of the dual-line array is mismatched. Analysis results show the delay-subtract beamforming has better performance of port/starboard discrimination. At last, the sea trial results demonstrate the theoretical results. 相似文献
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The Shanghai Synchrotron Radiation Facility(SSRF)booster ring,a full energy injector for the storage ring,is deigned to accelerate the electron beam energy from 150MeV to 3.5GeV that demands high extraction efficiency at the extraction energy with low beam loss rate when electrons are ramping.Closed orbit distortion(COD)caused by bending magnet field uniformity errors which affects the machine performance harmfully could be effectively reduced by bending magnet location sorting.Considering the affections of random errors in measurement,both ideal sorting and realistic sorting are studied based on measured bending magnet field uniformity errors and one reasonable combination of bending magnets which can reduce the horizontal COD by a factor of 5is given as the final installation sequence of the booster bending magnets in this paper. 相似文献
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With a novel light-weight and absolutely calibrated ultraviolet (UV) spectrometer, UV skylight radiances and O3 slant column densities are measured by balloon-borne limb measurements in Xinjiang area, China. UV skylight radiances measured at the height of 31 km are compared with the results from Modtran in the wavelength range from 290 to 420 nm. O3 slant column densities are derived from radiance spectra in the Huggins bands (320 - 335 nm) using differential optical absorption spectroscopy method. And the parameter exhibits a good correlation with the same value simulated by radiative transfer model (Tracy). The O3 profile simultaneously measured by an O3 sonde is used as input in Tracy calculations. The O3 sonde is launched on the same balloon. 相似文献
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For breaking through the sensitivity limitation of conventional surface plasmon resonance (SPR) biosensors, novel highly sensitive SPR biosensors with Au nanoparticles and nanogratings enhancement have been proposed recently.But in practice, these structures have obvious disadvantages.In this study, a nanohole based sensitivity enhancement SPR biosensor is proposed and the influence of different structural parameters on the performance is investigated by using rigorous coupled wave analysis (RCWA).Electromagnetic field distributions around the nanohole are also given out to directly explain the performance difference for various structural parameters.The results indicate that significant sensitivity increase is associated with localized surface plasmons (LSPs) excitation mediated by nanoholes.Except to outcome the weakness of other LSP based biosensors, larger resonance angle shift, reflectance amplitude, and sharper SPR curves' width are obtained simultaneously under optimized structural parameters. 相似文献
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Novel polymer distributed feedback(DFB)gratings are fabricated based on photopolymerization to reduce lasing threshold of polymer lasers.A photopolymer formulation sensitive to 355-nm ultraviolet(UV)light is proposed for the fabrication of polymer gratings and it can be used to form polymer films by spin-coating process.A very low surface-relief depth ranging from 12.5 to about 1.0 nm has been demonstrated with a refractive-index modulation of about 0.012.The experimental results indicate that such polymer gratings have promising potentials for the fabrication of low-order DFB organic semiconductor lasers. 相似文献
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We propose a novel methodology based on the projector-camera (ProCam) system to address the photometric compensation issue for the projection display on the patterned screen.The patterned screen is treated as the combination of a perfect white screen and a color modulator.The perfect white screen is used to automatically and accurately characterize the ProCam system offline using the polynomial model,and the parameters of the color modulator can be efficiently recovered by employing only two gray images based on the linear reflectance model.The experimental results show that the color artifacts of the display image can be greatly improved with this methodology,which demonstrates its feasibility and validity in the photometric compensation. 相似文献