对乙酰基偶氮胂吸光光度法测定微量铜

在pH5.0的(CH2)6N4-HCl缓冲介质中,Cu(Ⅱ)与对乙酰基偶氮胂(ASApA)形成1比2络合物,λmax＝598nm,εmax=1.30×104L·mol-l·cm-1,铜浓度在0～2.0mg·L-1范围内遵从比耳定律。方法用于粮食、食品、水、树叶及人发等试样中铜的测定,结果满意。     

The role of heterogeneous deformation on damage nucleation at grain boundaries in single phase metals

The mechanical response of engineering materials evaluated through continuum fracture mechanics typically assumes that a crack or void initially exists, but it does not provide information about the nucleation of such flaws in an otherwise flawless microstructure. How such flaws originate, particularly at grain (or phase) boundaries is less clear. Experimentally, “good” vs. “bad” grain boundaries are often invoked as the reasons for critical damage nucleation, but without any quantification. The state of knowledge about deformation at or near grain boundaries, including slip transfer and heterogeneous deformation, is reviewed to show that little work has been done to examine how slip interactions can lead to damage nucleation. A fracture initiation parameter developed recently for a low ductility model material with limited slip systems provides a new definition of grain boundary character based upon operating slip and twin systems (rather than an interfacial energy based definition). This provides a way to predict damage nucleation density on a physical and local (rather than a statistical) basis. The parameter assesses the way that highly activated twin systems are aligned with principal stresses and slip system Burgers vectors. A crystal plasticity-finite element method (CP-FEM) based model of an extensively characterized microstructural region has been used to determine if the stress–strain history provides any additional insights about the relationship between shear and damage nucleation. This analysis shows that a combination of a CP-FEM model augmented with the fracture initiation parameter shows promise for becoming a predictive tool for identifying damage-prone boundaries.     

Grain Growth Kinetics of BaTiO3 Nanocrystals During Calcining Process

BaTiO3 nanocrystals were synthesized by sol-gel method using barium acetate (Ba(CH3COO)2) and tetrabutyl titanate (Ti(OC4H9)4) as raw materials. Xerogel precursors and products were characterized by means of thermogravimetric/differential scanning calorimetry (TG/DSC), X-ray diffraction (XRD) and transmission electron microscope (TEM). The influence of the calcination temperature and duration on the lattice constant, the lattice distortion, and the grain size of BaTiO3 nanocrystals was discussed based on the XRD results. The grain growth kinetics of BaTiO3 nanocrystals during the calcination process were simulated with a conventional grain growth model which only takes into account diffusion, and an isothermal model proposed by Qu and Song, which takes into account both diffusion and surface reactions. Using these models, the pre-exponential factor and the activation energy of the rate constant were estimated. The simulation results indicate that the isothermal model is superior to the conventional one in describing the grain growth process, implying that both diffusion and surface reactions play important roles in the grain growth process.     

异步轧制取向硅钢织构的模拟研究

本文系统地阐述了异步轧制剪切变形条件下板材冷轧织构的模拟计算理论;采用矢量法根据实测的ＯＤＦ构造板材的原始组织、在假设临界滑移系开动几率均等的条件下,运用Ｔａｙｌｏｒ模型对取向硅钢的亚表层和中心层的冷轧织构进行电算模拟;在此基础上,对剪切变形条件一些轧制因素的影响进行了讨论。     

Influence of thermal-decomposition temperatures on structures and properties of V2O5 as cathode materials for lithium ion battery

Submicron spherical V2O5 particles with a uniform size and a lower crystallinity were successfully synthesized by a chemical precipitationthermal decomposition technique using the commercial V2O5 powders as starting material. The crystal structure and grain morphology of samples were characterized by X-ray diffraction(XRD) and scanning electron microscopy(SEM), respectively. Electrochemical testing such as discharge–charge cycling(CD) and cyclic voltammetry(CV) were employed in evaluating their electrochemical properties as cathode materials for lithium ion battery. Results reveal that the crystallinity and crystalline size of V2O5 particles increased when the thermal-decomposition temperature increased from 400 ℃ to 500 ℃, and their adhesiveness was also synchronously increased. This indicate that the thermaldecomposition temperature palyed a significant influence on electrochemical properties of V2O5 cathodes. The V2O5 sample obtained at 400 ℃ delivered not only a high initial discharge capacity of 330 m A h g-1and also the good cycle stability during 50 cycles due to its higher values ofα in crystal structure and better dispersity in grain morphology.     

多弧离子镀制备的耐事故燃料包壳铬涂层晶粒结构研究

本文通过从几十微米到几埃的多尺度表征展示了多弧离子镀制备铬涂层的详细结构.经XRD, SEM, FIB, TEM和HRTEM表征,结果显示该涂层是一种多重结构,包括表面上的微米级颗粒、缺陷带钉扎的微米或次微米级液滴、以堆垛层错为晶界的柱状晶、以刃位错和螺型位错为区分的微晶、位错末端的原子畸变以及原子排列无序化的区域.这些结构通过改变涂层的结晶度,影响了晶格常数、表面粗化和FIB溅射裂纹.此外,通过分析HTEM照片,确定了这些堆垛层错和位错的类型.最后,讨论了沉积参数对这些晶粒结构的影响.     

基于MATLAB编程的碎屑岩粒度计算对比：以江西省会昌盆地上白垩统周田组为例

本文通过MATLAB编程语言对会昌盆地上白垩统周田组样品进行灰度化、二值化、自适应中值滤波、彩色标注等图像处理方式,准确测量出其粒度参数。结果显示：（1）MATLAB直接计算法与图解法所求得平均粒径分别为4.008φ和3.103φ;标准偏差分别为0.8φ和0.803φ;偏度分别为-0.195φ和-0.041φ;峰度分别为0.911φ和0.916φ。两种计算方式中标准偏差和峰度误差较小,可以互相替代,而标准偏差和偏度误差程度较大,不可互相替代。（2）MATLAB直接计算方法与镜下岩矿鉴定均显示周田组整体磨圆度较差,碎屑颗粒呈棱角状-次棱角状,通过沉积环境判别公式反映周田组形成于河流相沉积环境中,与地质背景及显微观测结果一致。（3）通过MATLAB编程语言,能够精准识别碎屑岩中颗粒轮廓及统计各项参数,对沉积物粒度研究提供了极大的便利,避免了人为主观因素干扰,提高了工作效率。     

Effect of the RE ionic size on the REBa2Cu3O7−δ ceramics oxygenated at 250 bar

REBa₂Cu₃O_7−δ (RE=Ho, Y, Dy, Gd, Sm, Nd) ceramics have been oxygenated at 1 bar pressure (LP) and, subsequently, at 250 bar (HP). Despite the noticed slight uptake of oxygen (up to the value of 0.07), after the HP processing, the electrical resistivity (ρ) of all samples increased, what was attributed to the deterioration of the grain boundaries. The increase of ρ was much more pronounced and also accompanied by a change of ρ(T) characteristics into a semiconducting-like one in the case of 123 compounds based on REs which ionic size is large enough to form solid solutions of RE_1+xBa_2−xCu₃O_y type (i.e., RE=Gd, Sm, Nd). As shown in the literature, such 123s usually contain more structural defects. Thus, the observed effect may be attributed to the migration of the defects induced by the elevated pressure oxygenation. The defects could be trapped near the grain boundaries resulting in the deterioration of their electrical properties. The possible role of the oxygen-pressure-induced modifications of the impurity phases has been also discussed. The materials obtained in the HP process may be regarded as 3D arrays of superconducting grains coupled by the Josephson junction or weak links only, as was shown in a tunneling experiment.     

加Nb中锰钢晶粒细化机理的研究

用扫描电镜,透射电镜及热力学计算相结合的方法,研究中锰钢晶粒细化机理的结果表明:在中锰钢中加入0.232％Nb和0.048％N,钢中可形成NbN和Nb_2C等化合物,它们可作为非自发结晶核心。这些晶核满足热力学及晶面条件,并在电镜下得到证实,从而使钢的晶粒度由原来的1～2级细化到6～7级,机械性能也大大提高。     

Ellipse detection and phase demodulation for wood grain orientation measurement based on the tracheid effect

The methods of ellipse detection and phase demodulation for determining wood grain orientation are proposed. These methods are based on the tracheid effect—laser beam impinging upon a wood surface forms an elongated laser spot with its direction indicative of the grain orientation. Experimental results show that the method of ellipse detection is suitable for the grain orientation measurement on planed softwood surfaces, while the method of phase demodulation is capable of extracting the grain orientation precisely from laser images with low signal-to-noise ratio, such as the images on the surfaces of hardwood species or roughsawn materials.