Exploration of bimetallic Pt-Pd/C nanoparticles as an electrocatalyst for oxygen reduction reaction

In this study, carbon supported Pt and Pt-Pd were synthesized as oxygen reduction reaction electrocatalysts for polymer electrolyte membrane fuel cells (PEMFCs). Pt and Pt-Pd nanoparticles have been synthesized by reduction of metal precursors in presence of NaBH₄. Various techniques such as X-ray diffraction (XRD), energy dispersive X-ray analysis (EDX) and scanning electron microscopy (SEM) were utilized to study the prepared samples. Furthermore, electrochemical properties of the prepared samples were evaluated from cyclic voltammetry (CV), linear sweep voltammetry (LSV), chronoamperometry and electrochemical impedance spectroscopy (EIS). The results showed, the crystallite size of electrocatalysts (Pt and Pt-Pd) is below 10 nm. The higher catalytic activity was detected for Pt-Pd/C electrocatalyst for oxygen reduction reaction (ORR). In addition, it is believed that the better performance of electrocatalyst is related to the synergic effect between Pt and Pd nanoparticles, weakening of the OO bond on Pd-modified Pt nanoparticles in ORR, uniform dispersion of Pd and Pt on the carbon support and higher electrochemical active surface area (EAS) of Pt-Pd/C electrocatalyst.     

The influence of compressive stress applied by hard coatings on the power loss of grain oriented electrical steel sheet

To reduce the core loss of electrical steel the vacuum arc ion plating technique has been used to deposit titanium nitride (TiN) layers on highly grain oriented electrical steel sheets. The layer thickness, the stresses of layers and coated sheets and the achieved reduction in core losses have been measured as functions of coating duration and applied bias voltage. Well adhered layers with high compressive stress up to 6.8 GPa have been produced. With increasing bias voltage the layer thickness decreases and the intrinsic stress of the layers increase. A further increase of bias voltage leads to a drop in stress due to thermal relaxation. In general, the tensile stress of the coated sheets rises with increasing layer thickness while the core loss of the coated material decreases with increasing tensile stress of the steel sheet and increasing bias voltage. The highest reduction of core loss has been found to be 28% (from P_1.7=0.86 W/kg for commercially coated HGO electrical steel sheet with glass film to 0.62 W/kg for TiN coated material) and is due to the reduction of excess loss only.     

Synthesis of nanocrystalline Co-Ni alloys by precursor approach and studies on their magnetic properties

Nanocrystalline Co-Ni alloys with different compositions were prepared by polyol reduction of mixed cobalt nickel hydroxides. The precursors (mixed cobalt nickel hydroxides) were prepared by co-precipitation. Powder X-ray diffraction analysis indicated the formation of fcc phase in the alloys and their crystallite size in the range 17-25 nm. Scanning electron microscopy and transmission electron microscopy studies revealed the morphology of the particles as being close to spherical, and the energy dispersive X-ray analysis showed the stoichiometry of the alloys. The magnetization as a function of field and temperature of the alloys, measured using a superconducting quantum interference device, showed superparamagnetic behavior with negligible coercivity and remanence values.     

基于布拉格光栅的边坡监测实验研究

提出了一种基于分布式光纤光栅的边坡监测与报警系统.根据强度折减法,利用ANSYS软件分析出边坡的软弱面及滑体所在的具体位置,从而在该处安装经过特殊封装的拉线式光纤光栅位移传感器.滑体的位移通过拉线转换为作用在光栅上的应力,而光纤光栅反射波长与应变具有良好的线性关系,因此通过检测光栅反射光的中心波长的偏移量,就可以解调出...     

Probabilistic Teleportation of a Three-Particle State

A scheme for teleporting a three-particle state is proposed when three pairs of entangled particles are used as quantum channels. Quantum teleportation can be successfully realized with a certain probability if the receiver adopts an appropriate unitary-reduction strategy. The probability of successful teleportation is determined by the smaller coetficients of the three entangled pairs.     

Growth and equilibrium morphology of metal precipitates formed inside an oxide matrix

Metal precipitation occuring during internal reduction of various mixed oxides, such as magnesia or alumina, doped with more noble transition metal oxides, is investigated for different doping contents, reaction temperature and driving forces. The precipitate morphology developing inside the solid oxide matrix and the corresponding orientation relationships between the metal and the oxide phase are analysed by transmission electron microscopy. The evolution of precipitate shape across the reduction scale is interpreted in terms of ageing of the metal inclusions; the various morphologies identified are ascribed to different stages of nucleation, diffusional growth and final equilibration.Precipitate morphology is analysed in terms of diffusion-controlled growth of small metal particles in their local and long range diffusion field. The influence of interfacial energy and related anisotropy is experimentally demonstrated for selected examples. The general role played by these parameters during growth and final equilibration is also discussed. The implications of the elastic strain fields building up during growth of the metal inside the oxide matrix are analysed in view of our experimental results. Shape changes taking place during the growth process are considered to be controlled by local matter transport properties. The influence of the reaction mechanism at an atomic scale and the relative fit of the crystallographic lattices are briefly summarised.     

NO分子A2Σ→X2Π双光子激光感生荧光光谱

以Nd∶YAG激光器抽运光学参变振荡器 /光学参变放大器做为激发源 ,得到了NO分子在 2 2 0～ 35 0nm波长范围内的双光子激光诱导荧光光谱 ,并将其归属于A2 Σ(ν′ =0 )→X2 Π(ν″ =1～ 8)跃迁 ,用最小二乘法拟合获得NO分子X2 Π态振动常量″ωe =(190 4 .7± 7.3)cm-1,″ωe ″xe =(14 .2± 1.2 )cm-1,″ωe″ye=- (0 .0 2 18± 0 .0 0 91)cm-1,及平衡位置的力常量k =(1.5 99± 0 .0 12 )× 10 3 N·m-1。计算了所得跃迁谱带的弗兰克康登因子及相对荧光强度 ,结果与实验观测值相符。这可为用激光诱导荧光光谱技术探测大气污染物NO分子提供理论及实验参考     

t—BuNO二聚体在不同溶剂中裂解机理的研究

本文利用＾１ＨＮＭＲ，ＵＶ－Ｖｉｓ方法，研究了ｔ－ＢｕＮＯ二聚体在有机溶剂及水溶液中的裂解反应产物，分析了其反应的动力学，提出了在非极性的有机相中ｔ－ＢｕＮＯ二聚体为均裂反应，而在极性的水相中为均裂和异裂同时进行的竞争反应。     

Cyclic integrals and reduction of rotational relativistic Birkhoffian system

The order reduction method of the rotational relativistic Birkhoffian is studied.For a rotational relativistic Birkhoffian system.the cyclic integrals can be found by using the perfect differential method.Through these cyclic integrals,the order of the system can be reduced.If the rotational relativistic Birkhoffian system has a cyclic integral,then the Birkhoffian equations can be reduced at least two degrees and the Birkhoffian form can be kept.An example is given to illustrate the application of the results.