Nb_3Sn CICC导体接头电阻测试

介绍了用于测试大电流Nb3Sn管内电缆导体接头电阻的超导变压器系统。该超导变压器包括初级线圈和次级线圈,其中初级线圈采用Nb Ti超导股线绕制;次级线圈采用Nb3Sn CICC导体绕制。初级线圈和次级线圈均浸泡在液氦中冷却。利用超导变压器对Nb3Sn CICC导体超导接头的测试结果表明,所设计的超导接头电阻满足设计要求。     

压痕对低温和高温超导股线临界性能影响研究

低温超导股线Nb Ti和Nb3Sn用于核聚变装置用的CICC导体结构,由于绞缆的作用及导体生产过程中的挤压作用,将会导致Nb Ti和Nb3Sn超导股线的表面产生不同形式的压痕,过大的压痕将会影响股线的临界性能;高温超导股线Bi-2212和Mg B2是未来可用于核聚变装置中制成CICC导体潜在的高温超导材料,由于高温超导材料的脆性,在电缆制备及导体制造过程中也会导致股线的表面产生压痕影响股线的性能。文中主要开展对于低温超导股线Nb Ti,Nb3Sn及高温超导股线Bi-2212和Mg B2的临界性能随压痕深度的变化规律,从而为导体制造的改进及未来高温超导导体的制造提供理论依据。     

Nb_3Sn超导股线残余应力分析

Nb3Sn超导股线在900K形成,而工作环境是在4.2K,从高温到低温会在Nb3Sn超导股线内部产生残余应力与应变,Nb3Sn超导股线对应力应变十分敏感,过大的应力会使股线的性能严重退化。通过理论计算和数值模拟的方法来计算Nb3Sn超导股线的残余应力与应变。     

Nb_3Sn超导线弯曲应变对临界电流影响研究

Nb3Sn超导线现为大型工程科研项目如国际热核聚变反应堆(ITER),强磁场项目等磁体的基本材料之一.由于A15相的脆性,受力作用下Nb3Sn超导体超导性能会发生严重退化.在ITER用管内电缆导体(CICC)中,股线受到电磁力作用时会产生弯曲应变.为研究弯曲应变对超导线的临界电流影响,我们对ITER标准临界电流测试骨架中间部位开槽,使股线在通电过程中产生循环的弯曲应变,并测试得到其临界电流.结合Nb3Sn超导线偏应变临界电流定标律,分析在两种极限假设情况(低丝间电阻和高丝间电阻)下超导线弯曲应变对临界电流的影响,并与骨架开槽实验结果进行比较.     

核聚变用内Sn法Nb3Sn股线的制备与性能

采用内Sn法工艺研究了ITER用Nb3Sn股线的制备与性能.我们已成功的研究出了批量生产股线的制备技术,股线具有优异的特性.股线非Cu区的临界电流密度Jcn在12T、4.2K、0.1μV/cm判据下达到1087A/mm2;在±3T的磁场变化范围,磁滞损耗为540 kJ/m3(4.2K);股线的n值在12T、4.2K下为20.此外我们也研究了Nb3Sn层的显微结构和Nb/Sn比.     

富Sn法制备多芯Nb_(3)Sn超导复合线的研究

采用Nb管和富Sn的铜锡合金之间的内扩散法制备了33和55芯的多芯Nb_3 Sn超导复合线.研究了Nb_3Sn反应扩散热处理(600—850℃,1—250hr)和添加元素In对Nb_3Sn反应扩散层的厚度、晶粒大小和超导性能的影响.结果表明:阶梯升温扩散热处理有利于晶粒细化,添加元素In提高了Nb_3Sn反应扩散层平均生长速率与Nb_3Sn晶粒长大速率之比值.55芯Nb_3(SnIn)复合线全电流密度J_c(4.2K,6T)约为7.3×10~4 Acm~(-2)     

添Ti或添Mg铌管富Sn法Nb3Sn导体的超导性能

采用 Nb 管富 Sn 法制备 Nb_3Sn 导体母材中添加适量合金元素 Ti 或 Mg 分别显著提高导体在≥12T 或≤12T 磁场区域的载流能力.由于 Ti 和 Mg 改善 Nb_3Sn 材料载流能力的机制不同,同时,Ti 进入 A15型(Nb,Ti)_3Sn 化合物晶格,并占据 Nb 原子的结晶学位置,而进入 Nb_3Sn 反应层的 Mg 则以 Mg-Nb-O 化合物沉淀相微粒弥散分布在 Cu-Sn-Mg 母材侧的 Nb_3Sn 晶粒中,因此,若在母材中同时添加合金元素 Ti 和 Mg 将可能明显提高导体在8—20T 整个实用磁场区域的载流能力.使用(Nb,Ti)_3Sn 导体(0.99mm~(?)×1.69mm~ω)制造的超导磁体(2a_1×2a_2×2b=31.5mm×70mm×99.5mm)在10.4T NbTi-Nb_3Sn 背景磁场下,磁体工作电流 I_a=392A(未失超)时,磁体中心场强 H_(?)=14.2T,此时,导体的工作电流密度 Ja(non cu)(14.2T,4.2K)=5.2×10~4Acm~(-2).     

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介绍了Pacman装置的设计原理,用Pacman装置测量了OST公司通过内锡法工艺制备的Nb3Sn超导股线在12T,4.2K条件下单轴方向的临界电流与应变的关系,应变的范围在-0.8%～+0.6%。用偏量比例模型模拟了临界电流与轴向应变之间的规律,分析了随应变的改变n值的变化,得出了Nb3Sn超导股线对应变的敏感程度。     

Nb_3Sn超导股线受压弹塑性有限元分析

运用ANSYS软件建立Nb3Sn超导股线的二维截面简单模型,采用有限元方法研究平板压缩和凹面板压缩方式对Nb3Sn超导股线在4.2K低温下受不同的压力下弹塑性应变的影响。通过分析得出:两种不同的压缩方式使Nb3Sn股线中超导区域的中间位置的应变比靠近外层位置的应变要大;受同样压力作用下,平板压缩导致的超导区域的平均应变要比凹面板平均应变大。采用该有限元模型,研究了Nb3Sn超导股线三个不同位置上产生的空隙在压力作用下对超导股线的弹塑性应变的影响。通过分析可得出:空隙会使股线中的超导区域的平均应变增大,并且越靠近施力点的空隙对平均应变影响越大;在具有相同位置的空隙下,平板压缩导致的超导区域的平均应变要比凹面板平均应变大。     

CFETR中心螺管模型线圈稳定性分析

中国聚变工程试验堆(CFETR)中心螺管模型线圈,内部磁体为Nb3Sn线圈,外部磁体为Nb Ti线圈。模型线圈最高磁场可以达到12.0T。针对提出的内部线圈方案,借助一维失超分析软件Gandalf,对Nb3Sn线圈的温度裕度、稳定裕度做了计算。在49k A,12T运行条件下,温度裕度为1.9K,稳定性裕度421.2m J/cm3~426.6m J/cm3。结果表明,温度裕度和稳定性裕度均不低于ITER导体设计要求。     

堆叠型REBCO超导股线的横向抗压特性研究

采用2mm宽REBCO超导带材，通过堆叠、圆化和拉拔等成型技术制备了多种规格的堆叠型股线，并利用试验手段研究了不同结构股线的横向抗压性能。经研究发现，超导股线在带面方向的抗压性能最好，侧面方向最差。而对比测试表明，股线带材和铜带的分布对其抗压性能影响不大，增加包壳壁厚可提高股线的抗压性能，而增大股线直径，可部分改善抗压能力，但股线扭转则会降低其抗压效果。     

超小晶粒锡掺杂CsPbBr3蓝光量子点的合成及其光学性能研究

近年来,铅卤钙钛矿CsPbX₃ (X=Cl,Br或I)因其具有荧光波段可调、荧光量子产率高(Photoluminescence quantum yield,PLQY)以及荧光半峰宽窄等优点而被广泛应用于光电器件领域.然而,与PLQY接近于100%的绿光和红光相比,蓝光卤素钙钛矿的PLQY仍比较低.在此,采用过饱和结晶的方法在室温下合成了粒径低于4 nm的超小晶粒锡(Sn)掺杂CsPbBr₃量子点,并对其结构特性和光学特性进行了研究.结果表明:随着SnBr₂添加量的增大,量子点晶粒的粒径略微减小,荧光发射峰发生蓝移,粒径由3.33 nm (SnBr₂为0.03 mmol)减小到2.23 nm(SnBr₂为0.06 mmol时),对应的荧光发射峰由490 nm蓝移至472 nm.当SnBr₂添加量为0.05 mmol时合成的超小晶粒锡掺杂CsPbBr₃量子点显示出最优的光学性能,其粒径约为2.91 nm,对应的XRD各晶面衍射峰强度最强,...     

Transient stability of AC multi-strand superconducting cables

AC application, it is necessary to estimate the stability of multi-strand superconducting cable. Therefore, we have been studying the transient stability of non-insulated multi-strand cable when one strand in a cable turns into the normal state locally. In the quench process, local temperature rise produced by current redistribution among strands is not desirable for stability. In a previous work, we discussed the effect of Cu matrix allocated to each strand on the transient stability and showed that the Cu matrix allocation can improve the stability of non-insulated multi-strand cable through mainly numerical simulations. In this paper, we carried out experiments on three kinds of non-insulated three-strand cables; one consists of NbTi/CuNi strands and the others consist of NbTi/Cu/CuNi strands having different cross-sectional arrangement. These sample strands have almost the same diameter, the same matrix to superconductor ratio and the same B–J characteristics to evaluate the effect of Cu allocation quantitatively. We choose to define the transient stability in terms of the minimum quench energy (MQE) at each DC transport current. We also investigated the transient stability of sample cables when quench is initiated in two or three (all) strands simultaneously.     

冷拉拔超细Ni80Cr20合金丝卷曲因素分析

Ni80Cr20超细丝经冷加工后呈规则的三维螺旋卷曲状态。实验研究了拉拔角度、变形量、拉拔速度和模具定径区长度对超细丝材曲率的影响，制定了NiCr合金丝单模冷拉拔工艺。结果表明:随拉拔角度的增加，丝材曲率逐渐增加；变形量增加，拉拔角度为17时，丝材曲率没有明显规律，基本在0.56 mm-1左右，但拉拔角度为0时，丝材曲率逐渐增加；拉拔速度小于10 mmin-1时，曲率逐渐增加，大于10 mmin-1时，曲率增加趋势变缓，大于30 mmin-1曲率又有所下降；定径区长度越长丝材曲率越小。分析认为，NiCr丝材表面产生的附加切变形及切变层的流动速度的不一致性是丝材产生卷曲的原因，且曲率越大残余应力越大。为减小不均匀变形，冷拉拔工艺采用0拉拔、拉拔速度10 mmin-1、模具定径区长度为模具定径区直径的60%。     

Drawing parameters optimization for birefringence reduction in optical fibers

The impact of the drawing process on the stress-induced birefringence in optical fiber is experimentally analyzed. By means of the photoelastic tomographic technique, residual internal stresses are measured in fiber samples drawn under different conditions of temperature, drawing tension and speed. From measured residual stress distributions, the stress-induced birefringence and beatlength are mathematically derived and compared, proving that an effective birefringence reduction can be obtained by a proper choice of drawing parameters.     

Closed loop direct metal deposition: art to part

The direct metal deposition (DMD) process is drawing considerable contemporary interest due to its capability to deliver “Art to Part”. DMD can reduce the lead time for a concept to product by eliminating several intermediate steps. The most attractive feature of the process is that not only can it produce functional parts but it can also be interfaced with the homogenization design method, heterogeneous solid model and computer aided design software to produce “Designed Material” with desired properties generally not observed in nature. Closed loop DMD is a synthesis of multiple technologies including lasers, sensors, computer numerical controlled work handling stage, CAD/CAM software and cladding metallurgy. This paper describes the methodology used to produce a designed macro- and microstructure and reviews the state of the art for closed loop DMD.     

掺Tm3+石英光纤中频率上转换产生可见光的实验研究

报道了实验研究连续锁模1053nmNd:YLF激光泵浦的掺Tm³⁺石英光纤中可见光区的频率上转换过程.测量了可见荧光光谱,并用Tm离子的分步三光子吸收过程解释了可见光频率上转换现象.     

Determining the opto-mechanical and geometrical properties of high-density polyethylene fibres

A method is described to determine the opto-mechanical and geometrical properties of high-density polyethylene, HDPE, fibres at the same time for the same region from the fibre. Variations of the transverse sectional shapes, areas, optical and mechanical properties of fibres during the cold drawing process were investigated. A rotator-mechanical drawing device was used for rotating the fibre around its longitudinal axis during the cold drawing process. The Pluta polarizing two-beam interference microscope was attached with the rotator-mechanical drawing device for detecting these variations under the interferometer. The rotator-mechanical drawing device permits determining the tensile stress–strain curve, Poisson's ratio and strain optical coefficient for HDPE fibres. Also, it permits determining the refractive index profile of the drawn fibres taking into considering the transverse sectional area and the enclosed area under the fringe shift. The optical orientation factor and orientation angle was calculated for HDPE fibre to clarify the orientation of molecules during the cold drawing process. Microinterferograms are utilized for illustrations.     

纳米硅薄膜复合阳极的绿色微腔式OLED的研究

采用甚高频增强型等离子体化学气相沉积技术,通过优化薄膜的沉积条件制备出高性能的P nc Si∶H薄膜材料(σ=5.86 S/cm、Eopt>2.0 eV).通过XRD测量计算出薄膜<111>、<220>和<311>三个晶向上的晶粒大小分别为15 nm、17 nm和21 nm;通过Raman测量,计算出其晶化率为35％左右.实验中,将P型纳米硅薄膜与氧化铟锡一起构成有机电致发光器件的复合阳极,研究了他们的发光特性,结果表明：由于P nc Si∶H薄膜材料具有近似半反半透的光学特性,它与高反射率的阴极Al使有机电致发光器件产生了微腔效应,使其发光光谱窄化,半宽高由126 nm窄化到33 nm;发光光亮明显增强,最大亮度为47 130 cd/m2,最大发光效率为9.543 83 cd/A,与以ITO为阴极的无腔器件相比,提高了约127%.     

A hybrid helical structure of hard-sphere packing from sequential deposition

Abstract

A hybrid helical structure of equal-sized hard spheres in cylindrical confinement was discovered as a ‘by-product’ of the recently developed sequential deposition approach [Physical Review E 84, 050302(R) (2011)] for constructing the densest possible packings of such systems. Unlike the conventional triple-helix structure where its three strands of spheres are packed densely to form triads of close-packed, mutually touching spheres, in this novel helical phase, only two of its three strands of spheres are packed in this densest arrangement and the overall structure resembles a hybrid of the single and the double helix. This article explains how this previously unknown structure can be constructed via the abovementioned sequential deposition of spheres, which involves manipulating the positions of a few spheres to create a template for the deposition process. The findings show that it is possible to discover new structures through varying only the configuration of the few spheres that form the template, where this approach relies on a sensitive dependence of the deposition-generated structures on the template.