TiO2悬浮体系光催化降解反应动力学模型的建立

以纳米材料TiO     

一种基于新型插值单元的稳态传热边界元法

为了提高边界元法在求解稳态热问题时的计算精度,通过使用一种新型单元插值方法(称为扩展单元插值法),实现对稳态传热问题的求解。扩展单元是在传统不连续单元的边界配置虚拟节点,把原非连续单元变成高阶的连续单元,并将其作为新型的插值单元。利用虚拟节点和内部源节点构造出的插值函数,可以精确插值边界上的连续和不连续物理场,插值精度要比原始不连续单元高两阶。另外,边界积分方程只在传统的不连续单元的内部节点处建立,只包含内部源节点的自由度,而虚拟节点的自由度可通过与内部源节点之间的关系消除掉,因此最终系统方程的求解规模不会增加。这种新型的插值单元继承了传统连续和不连续单元的优点,克服了它们的缺点。数值结果表明,此种单元插值方法用于求解稳态传热问题时可获得较高的计算精度和收敛性。     

Synthesis of large FeSe superconductor crystals via ion release/introduction and property characterization

Large superconducting Fe Se crystals of(001) orientation have been prepared via a hydrothermal ion release/introduction route for the first time. The hydrothermally derived Fe Se crystals are up to 10 mm×5 mm×0.3 mm in dimension. The pure tetragonal FeSe phase has been confirmed by x-ray diffraction(XRD) and the composition determined by both inductively coupled plasma atomic emission spectroscopy(ICP-AES) and energy dispersive x-ray spectroscopy(EDX). The superconducting transition of the Fe Se samples has been characterized by magnetic and transport measurements. The zero-temperature upper critical field H_(c2) is calculated to be 13.2–16.7 T from a two-band model. The normal-state cooperative paramagnetism is found to be predominated by strong spin frustrations below the characteristic temperature T_(sn), where the Ising spin nematicity has been discerned in the FeSe superconductor crystals as reported elsewhere.     

Single crystal growth and characterizations of iron arsenide superconductor BaFe2-xNixAs2（0.0≤x≤0.12）

A series of big single crystals of BaFeFe_2-xNi_xAs₂ have been prepared by the FeAs self-flux method, with nominal nickel doping x = 0--0.12. The dimensions of the cleaved crystals are over 10~mm along ab plane and ～ 2~mm in maximum along the c direction. The measurements of x-ray diffraction, electrical resistance and magnetic property are carried out on the crystals. For the undoped parent compound BaFe₂As₂, both resistance and magnetization data display an anomaly associated with spin density wave and/or structural phase transition, with the transition temperatures at ～ 138~K. For Ni-doped BaFe_2-xNi_xAs₂ crystals, the superconducting critical temperature T_c ranges from 4.3~K for x=0.06 sample to 20~K for the optimally doped x=0.10 crystal.     

Doping effects of transition metals on the superconductivity of (Li,Fe)OHFeSe films

The doping effects of transition metals(TMs = Mn, Co, Ni, and Cu) on the superconducting critical parameters are investigated in the films of iron selenide(Li,Fe)OHFe Se. The samples are grown via a matrix-assisted hydrothermal epitaxy method. Among the TMs, the elements of Mn and Co adjacent to Fe are observed to be incorporated into the crystal lattice more easily. It is suggested that the doped TMs mainly occupy the iron sites of the intercalated(Li,Fe)OH layers rather than those of the superconducting Fe Se layers. We find that the critical current density J_c can be enhanced much more strongly by the Mn dopant than the other TMs, while the critical temperature T_c is weakly affected by the TM doping.     

TiO2悬浮体系光催化降解反应动力学模型的建立

以纳米材料TiO2作为光催化剂,乙酰甲胺磷（DMAPT）作为目标化合物,在DGF－1型多功能光化学反应仪上研究了悬浮体系TiO2光催化降解反应的动力学模型,模型中的主要参数有：TiO2用量、入射光强、反应器的几何半径、反应器的经验参数、反应物初始浓度、羟基自由基二级速率常数及已知化合物的物理性质（分子的摩尔体积和溶解度）。模型较好地预测了其他化合物（如三氯乙烯（TCE)、四氯乙烯（PCE0、对－二氯苯（DCB）和四氯化碳（CTC）的光催化降解,对C0（TCE）＝22.1mg/L,C0(PCE)=20mg/L和C0(PCE)=40mg/L的反应物,完全降解所需的时间分别为3,4和5min,入射光强在1.38－6.05W/cm^2范围时,反应速率与光强的0.5次方成正比,催化剂最佳用量随着入射光的增强而增加。     

Structural and physical properties of undoped and nickel-doped BaFe2-xNixAs2（x = 0,0.04） single crystals

<正>Single crystals of undoped and nickel-doped BaFe_(2-x)Ni_xAs_2(x=0,0.04) have been grown by FeAs self-flux method.The maximum dimension of the crystal is as large as ~ 1 cm along the ab plane.The crystalline topography of a cleaved crystal surface is examined by scanning electron microscope(SEM).By x-ray powder diffraction(XRD) experiments using pure silicon as an internal standard,precise unit cell parameters(tetragonal at room temperature) are determined:a = 3.9606(4) A(1 A=0.1 nm),c = 13.015(2) A for BaFe_(1.96)Ni_(0.04)As_2 and a = 3.9590(5) A,c = 13.024(1) A for BaFe_2As_2.DC magnetization and transport measurements are performed to check superconducting transition(T_c=15 K for x=0.04) and other subtle anomalies.For BaFe_(0.96)Ni_(0.04)As_2 crystal,the resistance curve at normal state shows two distinct anomalies associated with spin and structure transitions,and its magnetization data above ~ 91 K exhibit a linear temperature dependence due to spin density wave(SDW) instability.     

Floating-zone growth and property characterizations of high-quality La2-хSrхCuO4 superconductor crystals

We have grown underdoped(x=0.11,0.12) and optimally doped(x=0.16) La2 x SrxCuO4 single crystals by the traveling-solvent floating-zone technique.In order to prepare good quality cuprate crystals,we have made much effort to optimize the preparation procedures.For example,we haveadopted the sol-gel route to prepare a highly fine and homogeneous La2xSrxCuO4 precursor powder for fabricating a very dense ceramic feed rod used for the floating-zone growth,and we have also used quite a slow growth rate.The high quality of the grown crystals has been verified by double-crystal x-ray rocking curves,with the full-width-at-half-maximum being only 113-150 arcseconds,which are the best data reported so far for La2xSrxCuO4 crystals.The superconducting critical temperatures of the grown crystals are 30,31 and 38.5 K for x=0.11,0.12 and 0.16 samples,respectively,according to magnetic measurements.     

(Na0.5Bi0.5)TiO3结晶学表征及其固溶体的X射线研究

(Na_0.5Bi_0.5)TiO₃-BaTiO₃系统在一定组成范围内是性能优良而独特的超声换能器陶瓷新材料。本文工作用X射线粉末衍射方法精确测定了单组分(Na_0.5Bi_0.5)TiO₃的晶胞参数,提出与前所报道不同的新的晶胞类型;在此基础上给出该系统不同组成点的晶格参数,并对性能、晶格参数和组成之间关系和相关系作初步讨论。 关键词：     

Doping Mn into(Li_(1-x)Fe_x)OHFe_(1-y)Se superconducting crystals via ion-exchange and ion-release/introduction syntheses

We report the success in introducing Mn into(Li_(1-_x)Fe_x)OHFe_(1-y) Se superconducting crystals by applying two different hydrothermal routes, ion e_xchange(1-step) and ion release/introduction(2-step). The micro-region _x-ray diffraction and energy dispersive _x-ray spectroscopy analyses indicate that Mn has been doped into the lattice, and its content in the 1-step fabricated sample is higher than that in the 2-step one. Magnetic susceptibility and electric transport properties reveal that Mn doping influences little on the superconducting transition, regardless of 1-step or 2-step routes. By contrast, the characteristic temperature T*, at which the negative Hall coefficient reaches its minimum, is significantly reduced by Mn doping.This implies that the hole carriers contribution is obviously modified, and hence the hole band might have no direct relationship with the superconductivity in(Li_(1-_x)Fe_x)OHFe_(1-y) Se superconductors. Our present hydrothermal methods of ion e_xchange and ion release/introduction provide an efficient way for elements substitution/doping into(Li_(1-_x)Fe_x)OHFe_(1-y) Se superconductors, which will promote the in-depth investigations on the role of multiple electron and hole bands and their interplay with the high-temperature superconductivity in the FeSe-based superconductors.