超细Ni80Cr20合金丝冷拉拔烧头及穿模工艺

采用冷拉拔技术制备超细Ni80Cr20合金丝,探索了电化学法烧头和超景深显微镜辅助穿模方法,开展了直径25.60μm的超细丝拉拔至21.14μm的烧头和穿模工艺研究。实验结果表明:采用电解电压为5V,0.2mol/L的HCl溶液,烧头时间为1s,超景深显微镜200倍放大模式,成功拉制直径为21.14μm的微丝;电化学法可以精确控制烧头电压和时间,同时超景深显微镜可以放大金刚石模具孔径,解决了烧头时间控制不准确和人工穿模的难题,显著提高了穿模效率和成功率。     

低损耗NbTi线材制备技术研究

国内重离子加速器(HIAF)磁体服役在高速脉冲电流下,要求超导磁体用超导线具有较低的损耗,并具有高的临界电流,针对磁体的设计要求,本文研制了两种新型结构的NbTi/Cu0.5Mn超导线,通过两次组装、冷拉拔获得了线径Φ0.8mm、12960芯和10800芯、铜比2.0、芯丝小于5μm的高临界电流、低损耗超导线,系统研究了两种新型结构超导线的截面形貌、芯丝形貌、磁滞损耗及不同时效热处理次数超导线的临界电流密度(Jc)和n值,最后获得了线材芯丝直径和磁滞损耗的变化关系.研究结果表明,两种线材经过二次组装、挤压和冷拉拔后,单个亚组元成型良好,芯丝变形粗细均匀,尺寸大约4μm.随着时效热处理次数由3次增加到5次,线材芯丝表面有颗粒状的CuTi化合物生成,且5T、4.2K下临界电流密度由2295A/mm2增加到2958A/mm2,不同时效热处理次数的线材n值大小介于30~60之间,表明芯丝整体变形均匀.线径Φ0.8 mm、12960芯和10800芯线材在4.2K、±3T下的磁滞损耗分别为35.5mJ/cm3、42.8mJ/cm3,随着线材芯丝直径由4.6μm减小至2.8μm,磁滞损耗由42.8mJ/cm3降低至17.3 mJ/cm3.最后,通过优化工艺后获得了Jc(5T、4.2K)为2958 A/mm2,Qh(4.2K,±3T)为37.5mJ/cm3的千米级NbTi/Cu0.5Mn超导长线,并可实现批量化生产.     

铁磁材料对永磁体磁场分布的影响及悬浮测试

为了研究铁磁材料对永磁体磁场分布的影响，以纯铁与钕铁硼永磁体为研究对象，对添加纯铁后不同组合永磁体磁场进行了测试。结果表明：对直径为80 mm厚度为5 mm的纯铁及边长为10 mm的方形永磁体而言，当纯铁底部永磁体对称排列时，纯铁上表面磁场呈规律性的均匀分布。当永磁体数目为9,边缘距为0时，纯铁上表面中心磁场较大，分布均匀度较高；当纯铁侧面固定永磁体时，组合体表面磁场增强，但增幅不同，表面磁场值越大，磁场增幅越小，磁场均匀度降低；随着距组合体表面高度的增加，纯铁表面中心磁场逐渐减小，磁场均匀度先减小后增加。另外，利用超导样品对均匀区磁场进行了磁悬浮测试，表明该结构实现磁场均匀化的可行性，对后续超导块材平面运动控制的研究具有重要意义。     

挤压工艺制备19芯MgB_2超导线材及其性能研究

本文采用挤压工艺研制19芯结构的多芯MgB_2/Nb/Cu超导线材,通过单道次挤压工艺将多芯复合包套从Φ64mm挤压到Φ20mm。挤压后的复合线通过冷拉拔最终加工到Φ1.4mm,并在670℃,保温2h进行烧结热处理,成功地制备出百米量级长度的MgB_2超导线材。采用该工艺所制备MgB_2超导线材具有良好的晶粒连接性和芯丝结合强度;显微分析表明该多芯复合线材横截面及超导芯丝分布较为均匀;在20和35K,自场下测试了所研制线材的传输性能,其超导临界电流密度J_c分别为1.05×10~5和6.7×10~4A/cm~2。     

熔锥型光纤耦合器拉制过程的仿真和实验研究

基于熔锥型光纤耦合器在拉锥过程中光纤锥形的渐变特性和光纤之间熔融度的变化特点,构建了光纤耦合器在拉制过程中波导结构的变化模型.利用光束传播法对耦合器的拉制过程进行数值模拟,得到耦合器输出光功率随拉伸长度的变化规律以及耦合器的能量分布图.理论模拟和实验结果表明,光纤间熔融度与制作耦合器时的氢气流量及拉伸速度有关,氢气流量大,拉伸速度小,熔融度就大;光纤之间的耦合作用与拉伸长度及熔融度有关,拉伸长度增加或熔融度增大,都会使光纤间的耦合更加显著;拉伸长度不大时,锥形区的耦合可以忽略;随着拉伸长度的增加,光纤变细,耦合作用逐渐增强,锥形区的耦合现象越明显,同时光场也逐渐由纤芯向外发散,产生附加损耗.     

多芯光纤及其在弯曲传感中的应用

采用纤芯间距为38.78 μm的国产多芯光纤设计了一种光纤弯曲传感器.该多芯光纤弯曲传感器由长度为1 m的七芯光纤与单模光纤拼接制成,多芯光纤弯曲时,相邻的纤芯发生模式耦合.在传感器一侧,将宽带光注入到位于多芯光纤中心的纤芯,用光谱分析仪测量带有曲率信息的频谱,获得弯曲传感器的透射谱波长偏移与弯曲曲率半径的关系,结果表明:多芯光纤弯曲半径越小,弯曲曲率越大,串扰越明显.     

“十”字形自驱单元形成寡聚体的动力学行为

探索自驱粒子形状对自组装结构和动力学的影响是软物质研究的前沿课题.组装基元形成的寡聚体及其动力学是大量粒子形成组装结构的基础.本文设计了一种“十”字形自驱粒子,发现其可以形成数种不同构型的寡聚体,计算了寡聚体(二、三、四聚体)的均方位移、角速度、角速度分布概率、轨迹曲率分布概率等.寡聚体的运动行为可分为两类:一类是合力为零但力矩不为零,寡聚体进行小半径的偏心旋转;另一类是合力不为零力矩也不为零,寡聚体呈现大半径的偏心旋转.寡聚体的平动动力学在短时间尺度(大致约为1—2 s,与其角速度有关)都呈现超扩散现象,但转动速度受寡聚体结构影响;力矩越大,转动惯量越小,角速度越大.对于三聚体,轨迹曲率与角速度有关,角速度越大,曲率也越大.     

电磁脉冲作用下自由空间线缆的感应开路电压

 运用时域有限差分法结合基于Kirchhoff积分的近／远场变换，计算了高功率微波（HPM）和超宽带（UWB）电磁脉冲作用下自由空间不同长度线缆上感应的开路电压，分析了感应电压峰值和线缆长度之间的变化关系以及入射波波形参数对其影响。计算结果表明，辐射场电场强度为50 kV·m^-1的HPM和UWB作用在线缆上可以感应出几百V到数十kV的脉冲电压；感应电压的峰值与线缆长度之间并不是单调线性增加的关系；HPM的载频越高，感应电压峰值越小；UWB的脉冲宽度越宽，感应电压峰值越大。     

半球壳准静态压缩下的变形行为研究

采用顶点及平板下压加载的加载方式对半球壳的准静态压缩进行了实验研究,获得了半球壳的变形模态及力-位移曲线。通过准静态压缩实验观察在不同加载方式下球壳变形模式随压缩深度的变化,发现半球壳出现了轴对称和非轴对称变形形式。利用ABAQUS有限元软件对球壳准静态压缩过程进行数值模拟,分析加载方式与球壳尺寸等对变形行为的影响。结果表明:球壳在压缩下的变形可分为加载点附近局部压平、轴对称凹陷以及形成非对称多边形3个阶段。其中,在压平向凹陷转变时,小截面平头加载的接触力-位移曲线产生了突跳现象,但在半球头与平板加载时未出现,且凹陷之后,半球头加载下接触力的增加速率减小,而平板加载下接触力的增加速率几乎保持不变。壳的径厚比越大,后期的变形程度越复杂;径厚比越小,由压平到凹陷转变时的临界荷载越大,球壳承载力越大。计算表明,在本研究范围内球壳凹陷前后接触力的大小以及增加速率只与厚度有关,而与半径的相关性则较小。     

立方体弹高速侵彻防护液舱剩余特性的数值模拟

针对高速破片侵彻液舱后的剩余特性问题,利用有限元分析软件ANSYS/LS-DYNA开展了数值模拟研究,对比分析破片侵彻垂直和倾斜液舱后速度的衰减规律以及侵彻深度的变化规律,探讨了舰艇中液舱的较优斜置角度。结果表明:液舱壁面倾斜角的存在有利于降低破片入水的瞬时速度;破片入水瞬时速度越大,在水中运动时速度衰减越快;在冲击及空泡阶段,破片侵彻深度迅速增加,且破片入水瞬时速度越大,侵彻深度增加越明显,该阶段侵彻深度仅相当于破片最终静止时侵深的10%左右。根据弹体速度衰减速率及侵彻深度的增加速率,认为倾斜60°的液舱能够达到较好的防护效果。     

超细Ni80Cr20合金丝的冷拉拔制备及表征

开展特定直径超细Ni80Cr20合金丝的冷拉拔制备研究,并通过扫描电子显微镜(SEM)、X射线衍射仪(XRD)和金属丝强力仪等对超细合金丝进行了表征。研究结果表明:烧头过程最佳电解液浓度为0.05mol/L,时间为3s;制备的镍铬合金丝直径为24.54μm,表面光滑,尺寸精准;拉拔后晶粒尺寸减小,退火后晶粒尺寸长大;拉拔态镍铬丝由于加工硬化,其伸长率由16%降低至1.88%;退火可改善镍铬丝性能,其断裂强度降低,伸长率增大,合金塑性增强,氮气退火丝的断裂强度大于真空退火丝的断裂强度,伸长率则相反。     

Field emission properties of carbon nanotubes film grown on NiCr alloy films

Carbon nanotubes (CNTs) are prepared on NiCr alloy films by low pressure thermal chemical vapor deposition at 600 °C. NiCr alloy films are deposited by magnetic co-sputtering method, and the various thickness and Ni/NiCr ratios are controlled by sputtering power. The diameter and length of CNTs, as well as the roughness of the CNTs films, mainly depend on the Ni/NiCr ratio. The field emission current density of the CNTs film increases with the increasing Ni/NiCr ratio from 65 wt% to 83 wt%, and decreases when the Ni/NiCr ratio is more than 87 wt% in the alloy film.     

Antiferromagnetic Mn50Fe50 wire with large magnetostriction

This work presents a study on the relation between the fiber texture and the magnetostrictive performance in an antiferromagnetic Mn₅₀Fe₅₀ alloy wire, which was prepared through the combining process of hot rolling and cold drawing. The face-centered cubic (fcc) crystal structure can be retained during the plastic deformation process. Mixed fiber textures consisting of both 1 1 0 and 1 0 0 components were formed along the drawing direction (DD) in the wire. A large magnetostriction of 750 ppm was obtained along DD under 1.2 T, which can be ascribed to the single γ phase and the formation of preferred crystal orientation.     

微结构光纤制备过程中不同位置空气孔的形变量分析

根据热传导原理，在拉制微结构光纤(MSF)时，在高温区中，MSF预制棒的包层内不同位置加热的温度也不一样，且由表面往中心方向温度逐渐下降，温度梯度随MSF预制棒下棒速度的加快或包层空气填充率的减少而增大.由于材料的表面张力和黏度系数都是温度的函数，因此将MSF预制棒拉细成MSF时，实际所得到的MSF结构，并非是预制棒等比例的缩小，而是温度越高的空气孔形变量越大.为得到符合设计要求的MSF，就必须将MSF预制棒包层空气孔尺寸按温度变化规律设计，从而消除由于加热温度的非均匀性对拉制的MSF包层空气孔所产生的影响.     

The investigation of ZnO：Al2O3/metal composite back reflectors in amorphous silicon germanium thin film solar cells

Different aluminum-doped ZnO （AZO）/metal composite thin films, including AZO/Ag/Al, AZO/Ag/nickelchromium alloy （NiCr）, and AZO/Ag/NiCr/Al, are utilized as the back reflectors of p-i-n amorphous silicon germanium thin film solar cells. NiCr is used as diffusion barrier layer between Ag and Al to prevent mutual diffusion, which increases the short circuit current density of solar cell. NiCr and NiCr/AI layers are used as protective layers of Ag layer against oxidation and sulfurization, the higher efficiency of solar cell is achieved. The experimental results show that the performance of a-SiGe solar cell with AZO/Ag/NiCr/Al back reflector is best. The initial conversion efficiency is achieved to be 8.05%.     

硅晶格微区结构特征与Raman谱线宽

本文主要讨论半导体器件的晶格质量问题，检测评估工艺过程对基质晶格所造成的损伤程度。文中得出Ｒａｍａｎ线宽与格位扭曲角＜θ＞＿（ｒｍｓ）的关系，一个良好的器件，Ｒａｍａｎ谱半高宽应控制在３一６ｃｍ￣（－１）以内，对应的＜θ＞ｒｍｓ约为１～３     

Electrons in a curvilinear quantum wire

The adiabatic motion of electrons in curvilinear quantum wires was studied. It was assumed that the cross section of a wire was constant along its length. The potential that limited electron motion across a wire and the shape of the cross section of the wire were considered arbitrary, while the curvature and the torsion (defined as the derivative of the cross section rotation angle with respect to the length) were assumed to be small. An effective nonrelativistic Hamiltonian for the motion of electrons along a wire with the conservation of transverse quantum numbers was obtained. The spin-orbit coupling Hamiltonian related to the curvature and torsion of a wire was found. Particular cases of a rectilinear twisted quantum wire with a noncircular cross section and a curvilinear quantum wire on a plane were studied. Various transverse potential models limiting the motion of electrons were considered. In particular, the coefficients of the effective Hamiltonian for quantum wires with rectangular and circular cross sections and hard walls and for wires with a parabolic potential were found.     

Change in the Form of Cementite in High Carbon Steel Wires

The change of carbides in 0.97 wt% carbon steel wires induced by cold drawing has been investigated by using Mössbauer spectroscopy and X-ray diffraction. The specimen wires have been drawn from 5mm down to 0.2mm in diameter. The carbide is confirmed to be cementite by the X-ray diffraction. Typical ⁵⁷Fe Mössbauer spectra obtained from the particles extracted from the wires show the superposition of a typical ferromagnetic cementite pattern and a rather broad paramagnetic doublet The relative intensity of the paramagnetic doublets increases as an increase in the degree of drawing. The cementite particles extracted from the outer parts of the wire behave as paramagnetic at 300K while the particles from the interior parts of the wire behave as an ordinary ferromagnetic cementite. The amount of the ferromagnetic cementite in the wire decreases with an increase in the degree of drawing. This means that the cementite has decomposed and dissolved into the matrix during the heavy deformation.     

偏心激励聚合物光纤横截面的光功率分布

研究了偏心激励多模聚合物光纤横截面的光功率分布。用光线追迹法计算了不同的激励源偏心距离和光纤长度时,光纤出射端横截面的光功率分布,并用二维CMOS图像探测器阵列进行了测量。数值计算和实验测量的结果均表明随着激励源偏心距的增加,光功率分布由光纤轴心向外偏移并形成环状;光功率分布在圆周方向的均匀性随着光纤长度的增加而趋于均匀。对中心激励的弯曲光纤光功率分布的测量结果表明,当弯曲曲率半径远大于临界曲率半径时,光功率分布无显著展宽,光功率分布随曲率半径的减小而向曲率外侧偏移;当光纤弯曲半径接近于临界曲率半径时,光功率分布显著展宽。