Effect of ZnF2 Coating on Performance of LiNi0.5Mn1.5O4 Cathode Material for Lithium-ion Batteries

采用溶胶-凝胶法制备了LiNi0.5Mn1.5O4正极材料，并利用Zn F2对其表面进行包覆改性。XRD、SEM和TEM测试表明，包覆处理不影响材料的晶体结构，2%(质量分数，以LiNi0.5Mn1.5O4质量计，下同)的Zn F2在LiNi0.5Mn1.5O4表面形成了约7 nm厚均匀包覆层。对未包覆的LiNi0.5Mn1.5O4和1%、2%、3%的Zn F2包覆后的LiNi0.5Mn1.5O4的电化学性能进行了考察，发现Zn F2包覆能够减弱电解液与LiNi0.5Mn1.5O4正极材料之间的相互作用，稳定电极表面，提高材料的电化学性能。其中，2%Zn F2包覆样品表现出最佳的循环性能和倍率性能，0.2C电流倍率下循环200圈后，其放电比容量维持在109.0 m A·h/g，保持率为79.7%；5 C电流倍率下循环500圈后，放电比容量维持在94.2 m A·h/g，保持率为85.6%

An Inverse Method for Supersonic Flowfield with Given Downstream Boundary

为了实现超声速流场出口参数的可控设计,借鉴特征线方法在古尔赛特与柯西问题两类边值条件中的应用,提出了一种根据下游边界条件求解其依赖域的逆柯西问题求解方法,并在此基础上发展了一种均匀来流条件下的超声速流场逆向求解方法。对轴对称内收缩流场、二维平面流场、轴对称外锥流场三个典型算例校核表明,逆向求解方法得到的计算结果与正向特征线方法一致,由此验证了该逆向求解方法的可行性,并有效拓展了超声速流场的设计思路。For the controllable design of exit parameters in supersonic flowfield,a new method of solving the inverse Cauchy problem,referring to the Method of Characteristics applied in the Goursat and Cauchy problems,is proposed to calculate the domain of dependence according to known downstream condition. On this basis,an inverse method for supersonic flowfield with the uniform flow condition is further developed. The validation of three typical cases(axisymmetric internal compression flowfield,two-dimensional planar flowfield and external conical flowfield) shows that results obtained by the inverse method agree well with those obtained by forward MOC,which verifies the feasibility of the inverse method and expands the thought of supersonic flowfield design effectively.国家自然科学基金(51276151;91441128);; 国防基础科研(B1420133058);; 中央高校基本科研业务费(20720140540

Conversion and Application of Streamline-Characteristic Coordinate System in Supersonic Flows

为了求解二维平面弯曲激波波后流场,讨论并发展了一系列基于流线-特征线坐标系变换的流场代数计算方法。该系列方法依据二维平面流场中气流角、静压沿特征; 线近似不变的特点,可快速求解平面弯曲激波波后流场。其中,等气流角近似法适合模拟流线轨迹,等静压近似法适合求解波后流场参数。在此基础上,又提出了一; 种改进的等气流角-等静压混合方法用于计算弯曲激波波后流场。和特征线法对比,等气流角-等静压混合法计算得到的流场基本特征与特征线法得到的结果相同,; 在来流马赫数Ma=6和Ma=4情况下误差分别仅为0.5%和0.15%,证实了该方法在求解二维平面弯曲激波流场中的适用性。In order to solve the two-dimensional planar flowfield behind the curved; shock,a series of algebraic methods are acquired at the; streamline-characteristic coordinate system. The main idea is that flow; angle and static pressure are approximately constant along each; characteristic line. In contrast to the Method of Characteristics,the; method of constant flow angle is good at calculating the streamline; trajectory while the method of constant static pressure is proper for; solving the flowfield parameters. A combined method named MCFP,Method of; Constant Flow-angle and Pressure,is afterwards proposed to better solve; the two-dimensional planar flowfield behind the curved shock. For a; relatively large Mach number range,the flowfield calculated by the MCFP; method is in good agreement with the MOC's. The error at incoming Mach; number 6 is 0.5% and the error at incoming Mach number 4 is 0.15%,which; demonstrates the applicability of the MCFP method.国家自然科学基金; 国防基础科研; 中央高校基本科研业务

微结构光纤的制造工艺研究

构建了基本的微结构光纤制造系统,初步形成了可行的微结构光纤制造技术路线。利用该工艺技术制造出了全内反射（TIR）型微结构光纤,该TIR型光纤纤芯为9.5μm,空气孔等效直径为9.8μm,孔间距为12.3μm,在1385nm的羟基吸收峰为0.106dB/m,1550nm的衰减为0.008dB/m;该微结构光纤经过显微镜放大和CCD采样到计算机得到的图片表明:光纤中空气孔基本均匀,并且微孔点阵基本呈现正六边形排列

我国掺稀土光纤的现状分析

掺稀土光纤作为激光增益介质在光纤通信、光纤激光器和传感器等领域有着广泛的应用,国内掺铒光纤、掺镱光纤的市场曾长期被Corn ing、Lucent等国外光纤制造厂商所垄断,近年来我国掺铒光纤、掺镱光纤的研究取得了很大进展,已部分替代国外进口。文章主要介绍国内掺铒光纤、掺镱光纤的研究现状和发展趋势

纳米bnioh2的制备及其储锂性能

以Ni(NO_3)_2·6H_2O和NaOH为原料采用化学沉淀法制备了Ni(OH)_2电极材料。采用X射线衍射(XRD)和场发射扫描电子显微镜(FESEM)表征了样品的微观结构,结果表明该样品是具有片状纳米次级结构的β-Ni(OH)_2。采用循环伏安(CV)和电化学充放电测试研究了该β-Ni(OH)_2样品的储锂性能,结果发现该样品作为锂离子电池负极材料具有非常高的储锂活性,在50 mA·g~(-1)电流密度下其第3次循环放电比容量高于1550 mA·h·g~(-1);样品电极中的碳含量对其循环性能和倍率性都有显著影响,通过交流阻抗(EIS)测试分析了样品电极中碳含量的作用机理

Preparation and lithium ion storage performance of nano-sized β-Ni（OH）_2

Ni（OH）2 sample is prepared by chemical precipitation method with Ni（NO3）2·6H2O and NaOH as raw materials. X-ray diffraction（XRD） and field emission scanning electron microscope（FESEM） analysis reveal that the sample is β-Ni（OH）2 with sheet-like hier

大模场宽频单模光子晶体光纤的设计与制备

文章对无尽单模光子晶体光纤进行了理论设计,并提出了微结构光纤的制造工艺技术和相应的光纤拉丝工艺参数,制造出了较大模场的宽频单模光子晶体光纤,该光纤的芯直径为13.1μm,微孔直径为3.2μm,孔间距为8.2μm,1 550 nm波长的模场直径为14.6μm,1 550 nm的衰减为0.6 dB/km,1 383 nm水峰为14.9 dB/km。截止波长测试和近场光强分布检验表明,该光子晶体光纤确实具备较宽的单模工作范围