氧化钇对高速CBN砂轮用陶瓷结合剂玻璃料性能的影响

在CaO-Al2O3-SiO2(CAS)系统微晶玻璃中引入稀土氧化物Y2O3,制备出用于高速CBN砂轮的微晶玻璃结合剂。结合DTA,XRD,SEM等检测手段,研究了Y2O3的加入对微晶玻璃结合剂微观结构及其性能的影响。结果表明:随Y2O3含量的增加,微晶玻璃结合剂的耐火度降低,流动性增大。当Y2O3含量为0.8%(质量分数)时,钙铝硅系微晶玻璃结合剂具有最佳的力学性能(显微硬度753.26 MPa,抗折强度167.50 MPa,磨耗比1∶8.23)。加入Y2O3会影响玻璃的析晶性能,当加入Y2O3为0.8%时,促进析出新晶相Li2Al2SiO10和β-石英,尺寸大小约为0.2～1μm,其具有致密的微观结构,利于用于作CBN砂轮的结合剂。     

A Dodecahedrane-like Molecule C_（12）H_（12）B_8 with Uncommon T_h Symmetry

The molecule with Th symmetry is rare.A dodecahedrane-like molecule C12H12B8 with uncommon Th symmetry has been reported here.Density functional calculations and minimization techniques have been employed to characterize its structural and electronic properties.Its geometry,electronic properties,vibrational frequencies and heat of formation have been calculated at the B3LYP/6-311+G(d,p) level of theory.The absence of imaginary vibrational frequency confirms that it corresponds to true minimum on the potential energy hypersurface.Its vibrational bands in the IR intensity have been discussed and compared with future experimental identification.At the B3LYP/6-311+G(d,p) level,the heat of formation has been calculated to be 720.9 kJ mol-1 using the isodesmic reaction.According to this value,it is a potential high energy density molecule.     

HCl处理后局部有序Y沸石的二次晶化

将商品 Y 型沸石用 HCl 处理后, 运用 X 射线粉末衍射, 透射电镜和扫描电镜、红外光谱及 27Al 和 29Si 魔角旋转核磁共振对其进行了表征. 结果表明, 酸处理后 Y 沸石接近无定形, 其长程有序性遭到破坏, 但还保留部分局部结构. 以不同浓度酸处理后的 Y 沸石为前驱体, 在 150 oC, 0.3 mol/L NaOH 条件下采用蒸汽辅助干胶转化法进行二次晶化, 可以获得丝光沸石, 其相纯度与前驱体的 Si/Al 密切相关. 随 Si/Al 比不同, 所得丝光沸石形貌由纳米针状堆积逐渐向微米单块状变化, 且其比表面积可达 400 m2/g 以上, 微孔孔容在 0.19 cm3/g.     

Synthesis and Crystal Structure of a New Complex [Cd（C20H14N4）2Cl2]

The title compound [Cd(C20H14N4)2Cl2] 1 was synthesized via the hydrothermal reaction of CdCl2·7H2O and NaOH with 1,3-bis(benzimidazol-2-yl)benzene (BMB), and characterized by elemental analysis and infrared spectra. The crystal of 1 crystallizes in monoclinic, space group C2/c with a = 21.021(6), b = 9.489(3), c = 18.302(6), β = 108.686(6)o, V = 3458.2(19)3, Z = 4, C40H28CdN8Cl2, Mr = 804.01, Dc = 1.544 g/cm3, F(000) = 1624 and μ(MoKα) = 0.829 mm-1. The final R = 0.0306 and wR = 0.0779 for 3334 observed reflections with I > 2σ(I) and R = 0.0796 and wR = 0.0360 for all data. The cadmium atom is four-coordinated by the BMB ligands and Cl atom with a tetrahedral geometry. The extensive N-H···N hydrogen bonding interactions are observed in the structure, which further extend the [Cd(C20H14N4)2Cl2] units into a 1D structure. The thermogravimetric analysis measurement showed that compound 1 has thermal stability as no strictly clean weight loss step occurred below 425 ℃.     

Synthesis and Crystal Structure of a Two-folded Interpenetrating Three-dimensional Network from Flexible Bisimidazolyl Ligands

The hydrothermal reaction of 1,2-bis(imidazol-1′-yl)ethane (Bime) and Ni(NO3)2·6H2O gave rise to a two-folded interpenetrating 3D coordination polymer, [Ni(Bime)3·(NO3)2]n. Singlecrystal X-ray diffraction analyses show that the complex crystallizes in rhombohedral space group R-3. Ni(II) lies on a crystallographic S6 centre and connects six bimes into a 3D porous network. Bime exhibits an anti conformation. NO3- locates as the void filler to balance the charge in the system. The framework is stable through the two-folded interpenetration among the building units.     

The effect of PT on phases and electrical properties in Ba-Y-Cu-O system

Several new phases containing platinum in Y-Ba-Cu-O system are reported in this paper. When Ba-Y-Cu-O system containing platinum is sintered at 950°C, two hexagonal phases YBa₂(Pt, Cu)₃O_9-δ and Ba₄Pt_1+x Cu_2-x Cu_2-x O_9-δ (x = 0.1 – 0.9) are found, respectively. The super-K₂NiF₄ structure Ba _x Y_2-x (Cu, Pt)O₄ is obtained above 1000°C in the Y-Ba-Cu-O system containing platinum. Electrical properties of these phases are also reported.     

Structure Evolution in the Even-Even (124—134)~Xe with IBM2

We have investigated the structure evolution of the124-134Xe isotopic chain in the framework of the proton-neutron interacting model IBM2. The positive parity spectra of the ground state, quasi-β and quasi-γ bands are reproduced well. The staggering in124-130Xe are almost completely removed and the γ band agree well with the experiment data, even for the high-spin quasi-γ states. The key quantities of the collective structure evolution, including level energies, the B(E2) transition branching ratios, and the M1 excitations to 1+1mixer-symmetry states are analyzed by comparing with the experimental data. The parameters for representation of the Oπν(6) and SU πν(3) features in isotopes are examined. Both experimental data and theoretical results show that the shape phase transition of124 134Xe isotopic chain is from the SU πν(3)(triaxial rotation) to the Uπν(5)(vibration motion) with a considerable constituent of the Oπν(6) symmetry(γ-unstable rotation), where the shape phase transition rapidly takes place between the neutron number N = 76 and N = 78.     

Structural, Spectroscopic and Vibrational Properties for Low-Lying Electronic States of LiCl

A multireference configuration interaction(MRCI) study has been carried out on the LiCl molecule. The potential energy has been calculated over a wide range of internuclear separation for the 21 low-lying electronic states of the LiCl molecule dissociating into Li(2S,2P,3S)+Cl(2P). The(4)1Σ+,(3)1Π, 1-33Σ+, 1-33Π,1,3,1,3Σ,(5)1Σ+,(4)3Σ+,(4)1Π,(4)3Π excited states are studied for the first time in theory. Molecular spectroscopic constants(Re, De,ωe, ωeχe, Be and αe) have been derived for the 9 bound states(X1Σ+,(3)1Σ+,(2)3Σ+,1,3,1,3Σ,(4)1Π,(4)3Π) with a regular shape, and the spectroscopic constants of ground states X1Σ+are in good agreement with available experimental and theoretical values. The relative diferences between experimental values and our values for Re, De, ωe, ωeχe, Be andαe are 1.02%, 0.60%, 1.72%, 9.46%, 2.0%, and 0.75%, respectively. Moreover, vibrational levels of 9 bound states, which have not been investigated experimentally, are computed.     

Influence of the photon beam position on incident SR intensity at the SXMCD endstation

A small fluctuation of the photon beam position will affect the intensity and polarization characteristics of synchrotron radiation （SR） when it enters an endstation through the related beamline. In this paper, by changing the electron orbit equilibrium position in the vertical direction, we have measured the corresponding changes in the absorption strength of the SR with a gold mesh in different chopper aperture positions. It is found that for three aperture positions, the absorption intensity of the gold mesh shows a good Gaussian distribution as the photon beam position moves, while the ratio of the SR intensity passing through the upper and lower apertures shows a monotonous variation. This suggests a new method for estimating the circular polarization degree of SR originating from the bending magnet based on our current measurement.     

Convergence of Nonlinear Schrödinger–Poisson Systems to the Compressible Euler Equations

Abstract

The combined semi-classical and quasineutral limit in the bipolar defocusing nonlinear Schrödinger–Poisson system in the whole space is proven. The electron and current densities, defined by the solution of the Schrödinger–Poisson system, converge to the solution of the compressible Euler equation with nonlinear pressure. The corresponding Wigner function of the Schrödinger–Poisson system converges to a solution of a nonlinear Vlasov equation. The proof of these results is based on estimates of a modulated energy functional and on the Wigner measure method.