Low-Temperature Solid State Synthesis and Characterization of Superconducting Vanadium Nitride

Superconducting vanadium nitride （VN） is successfully synthesized by a solid-state reaction of vanadium pentox- ide, sodium amide and sulfur in an autoclave at a relatively low temperature （240-400℃）. The obtained samples are characterized by x-ray diffraction, x-ray photoelectron spectroscopy and transmission electron microscopy. The result of the magnetization of the obtained VN product as a function of temperature indicates that the onset superconducting transition temperature is about 8.4K. Furthermore, the possible reaction mechanism is also discussed.

Strontium ferrite powders prepared from oily cold rolling mill sludge by solid-state reaction method

Oily cold rolling mill （CRM） sludge is one of the pollutants emitted by iron and steel plants. Recycling oily CRM sludge can not only reduce pollution but also bring social and environmental benefits. In this study, using oily CRM sludge as sources of iron oxide, the strontium ferrite powders were synthesized in multiple steps including vacuum distillation, magnetic separation, oxidizing roasting, and solidstate reaction. The optimal technological conditions of vacuum distillation and oxidizing roasting were studied carefully. To consider the effects of Fe203/ SrCO3 tool ratio, calcination temperature, milling time and calcination time on magnetic properties of prepared strontium ferrite powders, the orthogonal experimental method was adopted. The maximum saturation magneti- zation （62.6 mA-m2.g-1） of the synthesized strontium ferrite powders was achieved at the Fe203/SrCO3 mol ratio of 6, 5 h milling time, 1250 ~C calcination temperature, and 1 h calcination time. Strontium ferrite powders syn- thesis method not only provides a cheap, high quality raw material for the production of strontium ferrite powders, but also effectively prevents the environmental pollution.

Preparation of Li[Ni_(1/3)Co_(1/3)Mn_(1/3)]O_2 powders for cathode material in secondary battery by solid-state method

Employing Li2CO3, NiO, Co3O4, and MnCO3 powders as starting materials, Li[Ni1/3Co1/3Mn1/3]O2 was synthesized by solid-state reaction method. Various grinding aids were applied during milling in order to optimize the synthesis process. After successive heat treatments at 650 and 950 ℃, the prepared powders were characterized by X-ray diffraction (XRD) analysis, scanning electron microscopy, and transmission electron microscopy. The powders prepared by adding salt (NaCl) as grinding aid exhibit a clear R3m layer structure. The powders by other grinding aids like heptane show some impurity peaks in the XRD pattern. The former powders show a uniform particle size distribution of less than 1 μm average size while the latter shows a wide distribution ranging from 1 to 10 μm. Energy dispersive X-ray (EDX) analysiss show that the ratio of Ni, Co, and Mn content in the powder is approximately 1/3, 1/3, and 1/3, respecively. The EDX data indicate no incorporation of sodium or chlorine into the powders. Charge-discharge tests gave an initial discharge capacity of 160 mAh·g-1 for the powders with NaCl addition while 70 mAh·g-1 for the powders with heptane.

A Hybrid Backward Euler Control Volume Method to Solve the Concentration-Dependent Solid-State Diffusion Problem in Battery Modeling

Several efficient analytical methods have been developed to solve the solid-state diffusion problem, for constant diffusion coefficient problems. However, these methods cannot be applied for concentration-dependent diffusion coefficient problems and numerical methods are used instead. Herein, grid-based numerical methods derived from the control volume discretization are presented to resolve the characteristic nonlinear system of partial differential equations. A novel hybrid backward Euler control volume (HBECV) method is presented which requires only one iteration to reach an implicit solution. The HBECV results are shown to be stable and accurate for a moderate number of grid points. The computational speed and accuracy of the HBECV, justify its use in battery simulations, in which the solid-state diffusion coefficient is a strong function of the concentration.

The effect of agglomerate on micro-structural evolution in solid-state sintering

Discrete element method （DEM） is used in the present paper to simulate the microstructural evolution of a planar layer of copper particles during sintering. Formation of agglomerates and the effect of their rearrangement on densification are mainly focused on. Comparing to the existing experimental observations, we find that agglomerate can form spontaneously in sintering and its rearrangement could accelerate the densification of compacts. Snapshots of numerical simulations agree qualitatively well with experimental observations. The method could be readily extended to investigate the effect of agglomerate on sintering in a three- dimensional model, which should be very useful for understanding the evolution of microstructure of sintering systems.

钆、镁共掺杂Y型钡铁氧体的磁介电耦合效应

采用固相烧结法合成了Ba_(2-x)Gd_(x)Zn_(2)Fe_(12-x)Mg_(x)O_(22)(x=0.0,0.1,0.2,0.3)陶瓷样品。X射线粉末衍射图谱表明钆、镁掺杂减小了样品的晶格参数,通过扫描电子显微镜观察到掺杂稍微改变了样品的微观形貌。介电性能分析表明,随掺杂量的增加,样品的介电常数提高,并在低温下产生介电色散现象。50 K以上的磁介电现象是电子跳跃运动、磁阻效应和Maxwell-Wagner效应等共同作用的结果。在掺杂x=0.1样品中,调制出非共线磁结构,产生本征磁介电效应。研究结果为磁介电提供了基础理论价值。

CaLa_(2)(WO_(4))4:Eu^(3+),Sm^(3+)新型白光LED用红色荧光粉的发光性能研究

本文采用高温固相法制备了CaLa_(2)(WO_(4))_(4)∶Eu^(3+)和CaLa_(2)(WO_(4))_(4)∶Eu^(3+),Sm^(3+)系列红色荧光粉。通过X射线衍射仪、扫描电子显微镜等对样品的晶体结构、光谱、热稳定性、荧光寿命及色度坐标进行表征与分析。结果表明,Eu^(3+)和Sm^(3+)的掺入没有改变CaLa_(2)(WO_(4))_(4)晶体结构,为单一纯相。在394 nm激发下,CaLa_(2)(WO_(4))_(4)∶Eu^(3+)荧光粉在615 nm处红光发射最强,源自Eu^(3+)的^(5)D0→7F_(2)电偶极跃迁,最佳掺杂量为0.09。Sm^(3+)掺入后,发射峰增强,荧光粉的寿命明显增加,Sm^(3+)对Eu^(3+)起到敏化作用,共掺杂体系中Sm^(3+)向Eu^(3+)进行能量传递。CaLa_(2)(WO_(4))_(4)∶Eu^(3+),Sm^(3+)随着温度的升高,Eu^(3+)的^(5)D0→^(7)F_(2)跃迁发射的积分面积逐渐减小,当温度升高到100℃时,发光强度变为初始温度的53%,出现温度猝灭。在共掺杂体系中,色度坐标随着Sm^(3+)掺杂量的增加,向红光区域移动,当Sm^(3+)的掺杂量为0.02时,对应的色度坐标为(0.6458,0.3538)。基于CaLa_(2)(WO_(4))_(4)∶Eu^(3+),Sm^(3+)荧光粉的特性,可以将其作为潜在的白光LED用红色荧光粉。

Hydrothermal Synthesis and Characterization of Ce_(1-x)Mn_xO_(2-δ) Solid Solutions

Nanocrystals of Ce1-xMnxO2-δ（x=0.00,0.05,0.10,0.15,and 0.20） were synthesized by a hydrothermal reaction route.The solid solutions crystallized in a cubic fluorite structure with a particle size in the range of 11～15 nm.The incorporation of Mn ions in CeO2 resulted in a lattice volume reduction.Mn ions showed a mixed valence state of ＋2,＋3 and ＋4 in CeO2 lattice.An obvious red-shift of the absorption threshold edge was observed from the UV-visible spectrum.Compared with the bulk CeO2,Ce1-xMnxO2-δ nanocrystals exhibited a lower releasing oxygen temperature as indicated by TPR technique.

Preparation of BaCe_(0.5)Zr_(0.4)Y_(0.1)O_(3-α) by Sol-Gel Method and Its Electrical Properties

A precursor of BaCe0.5Zr0.4Y0. 1O3-α electrolytes was synthesized by the sol-gel method and sintered at temperature which were 150 - 250 ℃ lower than by solid state reaction. The AC impedance spectrums of electrolytes were measured by AUTOLAB PGSTA30 electrochemical measuring device at different temperatures. The conductivities of the electrolytes are 1.62×10^-4 - 6.43×10^-3, 2.52×10^-5 - 3.73×10^-3S·cm^-1 in the temperature range of 350-800℃. The activity energies are 0.54 and 0.84 eV. At the same time BaCe0.9Y0.1O3-α was prepared by direct solid state reaction. The conductivity of BaCe0.9Y0.1O3-α is 1 × 10^-4- 4×10^-3 S·cm^-1 and the activation energy is 0.50 eV at the same condition. The results show that conduction of electrolyte prepared by sol-gel method is higher than the one by solid state reaction. As far as BaCe0.9Y0.1O3-α concerned, its conductivity of the Zr-substituted specimens is decreased.

Transport diffuse interface model for simulation of solid-fluid interaction

For solid-fluid interaction, one of the phase-density equations in diffuse interface models is degenerated to a "0 = 0" equation when the volume fraction of a certain phase takes the value of zero or unity. This is because the conservative variables in phasedensity equations include volume fractions. The degeneracy can be avoided by adding an artificial quantity of another material into the pure phase. However, nonphysical waves,such as shear waves in fluids, are introduced by the artificial treatment. In this paper,a transport diffuse interface model, which is able to treat zero/unity volume fractions, is presented for solid-fluid interaction. In the proposed model, a new formulation for phase densities is derived, which is unrelated to volume fractions. Consequently, the new model is able to handle zero/unity volume fractions, and nonphysical waves caused by artificial volume fractions are prevented. One-dimensional and two-dimensional numerical tests demonstrate that more accurate results can be obtained by the proposed model.

Asymptotic analysis on weakly forced vibration of axially moving viscoelastic beam constituted by standard linear solid model

The weakly forced vibration of an axially moving viscoelastic beam is inves- tigated. The viscoelastic material of the beam is constituted by the standard linear solid model with the material time derivative involved. The nonlinear equations governing the transverse vibration are derived from the dynamical, constitutive, and geometrical relations. The method of multiple scales is used to determine the steady-state response. The modulation equation is derived from the solvability condition of eliminating secular terms. Closed-form expressions of the amplitude and existence condition of nontrivial steady-state response are derived from the modulation equation. The stability of non- trivial steady-state response is examined via the Routh-Hurwitz criterion.

NaYSiO_(4)∶Ce^(3+)蓝色荧光粉的发光性质及其在白光发光二极管上的应用

采用高温固相法合成了NaYSiO_(4)∶xCe^(3+)(0.01≤x≤0.05)系列蓝色荧光粉。NaYSiO_(4)∶xCe^(3+)荧光粉在250~360 nm之间的宽带吸收能与紫外LED芯片很好地匹配。NaYSiO_(4)∶xCe^(3+)荧光粉中存在多个Ce^(3+)离子荧光中心,且在紫外光激发下表现出峰值波长位于414 nm附近的宽带蓝光发射。NaYSiO_(4)∶0.02Ce^(3+)荧光粉在300~350 nm紫外光激发下量子效率在25%以上。NaYSiO_(4)∶0.02Ce^(3+)荧光粉表现出优良的化学稳定性,在水中浸泡14 d后荧光强度和量子效率几乎不变。将NaYSiO_(4)∶0.02Ce^(3+)蓝色荧光粉、商用(Sr,Ba)_2SiO_(4)∶Eu^(2+)绿色荧光粉和商用(Ca,Sr)AlSiN_(3)∶Eu^(2+)红色荧光粉涂覆于310 nm紫外LED芯片上制备得到了显色指数高达95的LED器件。当驱动电流从50 mA逐渐增大到300 mA时,制备的LED器件表现出稳定的暖白光发射,其色坐标几乎不变。上述结果说明,本研究报道的NaYSiO_(4)∶0.02Ce^(3+)蓝色荧光粉在紫外LED芯片驱动的白光发光二极管照明上有着潜在应用价值。

共掺La^(3+)和过量Sr^(2+)对荧光粉Sr_(1.96)Eu_(0.04)SiO_4发光性质的影响

采用高温固相法制备了荧光粉Sr_(1.96-x)Eu_(0.04)SiO_(4)∶xLa^(3+)(x=0、0.01、0.02、0.03、0.04、0.05)和Sr_(1.94+y)Eu_(0.04)La_(0.02)SiO_(4)∶ySr^(2+)(y=0、0.05、0.10、0.20、0.30).使用X射线粉末衍射仪、荧光分光光度计表征了荧光粉的物质结构和发光性质.结果表明:荧光粉的XRD均与Sr_(2)SiO_(4)标准卡片PDF 39-1256对应,没有杂质相产生.荧光粉Sr_(1.96)Eu_(0.04)SiO_(4)中掺入La^(3+)能增强其发光强度,且发射峰的位置不变.当La^(3+)掺杂量为2%(摩尔分数)时,荧光粉Sr_(1.94)Eu_(0.04)La_(0.02)SiO_(4)的发光强度最强.在Sr_(1.94)Eu_(0.04)La_(0.02)SiO_(4)中掺入一系列过量浓度Sr^(2+),能增强其发光强度,且不改变发射峰的位置和形状.当Sr^(2+)过量10%时,荧光粉的发光强度最强.荧光粉的宽带发射光谱可以拟合为2个独立的发射峰,对应Eu^(2+)的4f~65d~1→4f~7跃迁,2个发射峰的强度随着通气量的增大有规律变化,使得荧光粉的发光颜色从绿光区过渡到黄光区.

长循环型固态电池电性能参数试验方法研究

针对长循环型固态电池电性能参数试验方法缺失的情况,通过开展重量比能量、2 C放电容量保持率、循环寿命、低温放电容量、高温放电容量试验验证,分析了重量比能量、容量保持率等关键电性能参数的变化,研制形成长循环型固态电池电性能参数要求和试验方法,填补了试验方法的缺失,满足了应用发展需求。

高温固相修复再生磷酸铁锂正极材料研究进展

磷酸铁锂电池作为广泛应用的锂离子电池之一,其关键电极材料的高效回收循环利用在资源、环境、经济等方面具有重要的战略意义。高温固相修复技术能够实现磷酸铁锂正极材料短流程、低成本、高效率、绿色环保的循环利用,获得了广泛的关注和研究。针对高温固相修复再生磷酸铁锂正极材料,介绍了此类材料的电化学性能失效机理,从锂补充、缺陷修复和强化锂的迁移等方面对磷酸铁锂正极材料的修复机理进行了分析;阐述了焙烧温度、保温时间、补锂量等修复再生工艺参数对高温固相法修复磷酸铁锂正极材料的影响;分析了表面包覆和离子掺杂对提升磷酸铁锂正极材料电化学性能的影响和机理;并对高温固相修复法修复磷酸铁锂正极材料的可控制备、杂质控制和材料改性等方面的未来前景进行了展望。

固相反应合成MgAl_(2)O_(4)多孔纤维的研究

MgAl_(2)O_(4)纤维的主要制备方法为气相法,但该方法存在反应温度高、制备成本高以及产率低等问题。将碱式硫酸镁晶须作为模板,分别与铝溶胶或α-Al_(2)O_(3)微粉混合,通过固相反应制备了MgAl_(2)O_(4)多孔纤维,研究了热处理温度(1000、1100和1300℃)和保温时间(3、10 h)以及铝源(铝溶胶和α-Al_(2)O_(3)微粉)对MgAl_(2)O_(4)多孔纤维合成的影响。结果表明:1)与α-Al_(2)O_(3)微粉相比,以铝溶胶为铝源时,纤维中MgAl_(2)O_(4)生成量更高;2)随着热处理温度的升高,Al_(2)O_(3)与MgO逐渐反应完全,MgAl_(2)O_(4)的生成量不断增加,MgAl_(2)O_(4)多孔纤维上有小而均匀的纳米孔;3)最佳制备工艺是以铝溶胶为铝源,在1300℃保温3 h。

高热稳定CaGdAlO_(4)∶Er^(3+)/Yb^(3+)荧光粉的上转换发光及其温度传感性能

获得具有良好热稳定性和发光性能的非接触式光学温度传感材料是目前的研究热点之一,本工作通过高温固相法制备了Er^(3+)/Yb^(3+)共掺CaGdAlO_(4)∶Er_(x),Yb_(0.10)(x=0.006、0.008、0.010、0.012、0.014)荧光粉,尺寸大小分布在0.6~4.2μm。在980 nm激光激发下,该荧光粉在500~700 nm发射谱由两个发射带组成,528和550 nm处两个较强的绿光发射带,归属于Er^(3+)的^(2)H_(11/2)→^(4)I_(15/2)、^(4)S_(3/2)→^(4)I_(15/2)能级跃迁,663 nm处较弱的红光发射带,归属于Er^(3+)的^(4)F_(9/2)→^(4)I_(15/2)能级跃迁。上转换发光强度最大组分为CaGdAlO_(4)∶Er_(0.010),Yb_(0.10)。300~573 K变温发射谱表明,基于荧光强度比FIR_(528/550)参数,温度传感绝对灵敏度S_(A)从44.4×10^(-4) K^(-1)(@300 K)先增大到52.0×10^(-4) K^(-1)(@445 K)随后减小到49.0×10^(-4) K^(-1)(@573 K)。相对灵敏度S_(R)则从0.95×10^(-2) K^(-1)(@300 K)单调减小到0.27×10^(-2) K^(-1)(@573 K)。冷热循环实验表明该材料的热重复性优于98%。结果表明,CaGdAlO_(4)∶Er_(0.010),Yb_(0.10)荧光粉在光学温度传感领域具有潜在的应用前景。

全固态锂离子电池用硫化物电解质研究进展

全固态锂离子电池用硫化物电解质体系具有离子导电率高、制备方法简易、延展性良好和电化学性能稳定等优点,但距离大规模应用仍有一定难度。综述全固态锂离子电池硫化物电解质的研究现状,介绍包含玻璃态、玻璃陶瓷态和晶态等类型的电解质种类,列举硫化物固态电解质的常见制备方法,总结现有的正极与电解质界面、负极与电解质界面以及电解质自身稳定性等问题及相关解决方案。对硫化物电解质在全固态锂离子电池的应用前景作出展望。

Sm^(3+)掺杂Na_(5)Y(MoO_(4))_(4-y)(WO_(4))_(y)高热稳定性荧光粉的制备及发光性能研究

本文采用高温固相法合成了一系列Na_(5)Y_(1-x)(MoO_(4))_(4-y)(WO_(4))y∶xSm^(3+)(x=0~0.10,y=0~4)橙红色荧光粉。通过粉末衍射、透射电镜、常温/变温荧光发射谱、荧光激发谱、荧光动态衰减曲线和CIE色度坐标等光谱手段对荧光粉样品的光谱性能进行了研究。粉末衍射结果表明,合成的样品相位与Na_(5)Y(MoO_(4))_(4)的标准相一致,Sm^(3+)掺杂与引入(WO_(4))2-均未改变材料的相结构。在波长为406 nm光源的激发下,Na_(5)Y0.92(MoO_(4))3WO_(4)∶0.08Sm^(3+)荧光粉在643 nm附近橙红色荧光发射强度最高,继续增加Sm^(3+)的掺杂浓度,存在荧光猝灭现象,浓度猝灭的主要原因归为电偶极-电偶极相互作用。研究发现,Na_(5)Y(MoO_(4))_(4)基质中掺杂Sm^(3+)会引起电负性改变和晶格畸变,在Na_(5)Y_(1-x)(MoO_(4))_(4)∶xSm^(3+)中引入(WO_(4))2-阴离子基团,可以弥补因掺杂Sm^(3+)出现的缺陷,改善Na_(5)Y(MoO_(4))_(4)∶xSm^(3+)荧光粉的发光性能。在300~440 K,样品具有优异的热稳定性,荧光发射强度均超过室温时的96%;其CIE色度坐标均位于橙红光区域。以上结果表明新型Na_(5)Y_(1-x)(MoO_(4))_(4-y)(WO_(4))y∶xSm^(3+)橙红色荧光粉在WLED应用上有潜在价值。

压缩空气点火的无电烟火泵浦激光技术

为了解决传统固体烟火泵浦激光器点火效率低和电能依赖的问题,根据绝热压缩原理,设计使用了完全无电的压缩空气点燃烟火药泵浦Nd:YAG激光介质,提高了点火同步性和烟火药燃烧效率,实现了激光输出阈值药剂量10 mg,使用30 mg KClO4/Zr药剂,获得了30.2 mJ的激光能量,脉冲宽度10 ms,为小型无电高能激光器提供了一条新的实现路径。