Bi4Si3O(12)晶列结构中的晶粒变化趋势和相关性分析

在常压下用烧结法制备了具有高有序晶列结构的Bi4Si3O12微晶。利用X射线衍射(X-ray diffraction,XRD)和环境扫描电镜(Environmental Scanning Electron Microscopy,ESEM)分析了生成晶体的物相和微观形貌。结果表明:生成的是纯的立方相Bi4Si3O12晶体。Bi4Si3O12晶粒总是成对分布,且排列成行,从而形成高有序的晶列结构。其晶粒尺寸变化趋势有两种,一种是逐渐增大或者减小,另一种是晶粒尺寸在某一区域值内基本保持不变。在大多数情况下,每个晶行两侧的晶粒变化趋势具有一致性,每行两侧的晶粒尺寸具有高度的正相关特性。如果某行两侧的晶粒尺寸变化趋势不一致,而且晶粒尺寸不相关,则该行两侧晶粒应该属于两种不同的变化趋势。

硅酸铋(Bi_4Si_3O_(12))晶列结构中的晶粒尺寸和晶粒夹角分布

在常压下使用烧结法制备了高有序的Bi4Si3O12晶体。利用X射线衍射(XRD)分析了生成晶体的物相,通过环境扫描电镜(ESEM)观察了Bi4Si3O12晶体的微观形貌。用单样本Kolmogorov-Smirnov(K-S)法分别对晶粒的尺寸和夹角进行了统计学检验。结果显示:生成物为eulytite结构的Bi4Si3O12晶相。Bi4Si3O12晶粒总是成对分布,并且排列成行,形成高度有序的晶列结构。每行每侧的晶粒尺寸分布都遵循正态分布。每行成对晶粒取向之间的夹角遵循正态分布,而且所有行中的成对晶粒取向之夹角也服从正态分布,其总体夹角的平均值为122.3°,标准差为11.1°。

高有序Bi_4Si_3O_(12)微晶列结构特征分析

在常压下使用烧结法制备了具有高有序结构的Bi4Si3O12微晶。利用X射线衍射分析了生成样品的物相,通过环境扫描电镜观察了Bi4Si3O12晶体微观形貌。用单样本Kolmogorov-Smirnov法分别对晶粒夹角进行了统计学检验。结果显示:在一个稳定的硅酸铋晶列中晶粒成对分布。在一个晶行的一侧,晶粒取向和该晶行发育方向之间的夹角服从正态分布。晶行一侧的晶粒取向夹角的大小范围为53.9°～68.9°。一个稳定晶行一侧的平均晶粒夹角和晶粒尺寸之间具有高度的正相关性。如果稳定晶行一侧的平均晶粒夹角超过稳定晶列中晶粒夹角范围的最大值(68.9°),对应侧的高有序的晶列结构将会被破坏。然而,一侧有序结构的局部湮灭过程不会对晶行另一侧的高有序结构产生任何影响。

立方晶系中同指数晶列与晶面的空间取向关系

本文利用正倒格子关系分别在原胞基矢和晶胞轴矢坐标系下推证立方晶系中同指数晶列与晶面的空间取向关系.结果表明,在轴矢坐标系下立方晶系中同指数晶列与晶面垂直,在原胞基矢坐标系下同指数晶列与晶面的空间取向关系与具体的晶格结构相关.

合金凝固列状晶/等轴晶转变

在考虑合金组元局部线性叠加的基础上,结合计算相图,对多元合金凝固枝晶列状/等轴生长特性进行了系统的研究,通过考虑枝晶生长界面前沿的形核生长及竞争,发展了一个适用于多元合金凝固列状晶/等轴晶转变的理论模型,其与实验结果能很好的吻合。

一道理解倒格子概念的好例题

一道理解倒格子概念的好例题曾祥斌，卢望娣固体物理学中的倒格子概念是一个十分抽象、难学难懂、不易接受而又十分重要的基本概念。在多年的教学实践中，笔者深感要让学生正确理解倒格子概念，必须加强实践环节，使学生在实践中加深对概念的理解和认识。以下列出倒格子概...

Precipitation sequence of η phase along low-angle grain boundaries in Al-Zn-Mg-Cu alloy during artificial aging

The precipitation sequence of η（MgZn2） phase along low-angle grain boundaries in Al-Zn-Mg-Cu alloy was investigated by examining samples aged at 135 ℃ for various times from 5 min to 6 h. High resolution transmission electron microscopy （HRTEM） observations and energy dispersive X-ray spectroscopy （EDX） analysis indicate that the precipitation sequence of η phase along low-angle grain boundaries should be supersaturated solid solution （SSS）→vacancy-rich clusters （VRC）→GP Ⅱ zones→η＇→η. Based on the theory of non-equilibrium grain boundary segregation （NGS） and non-equilibrium grain boundary co-segregation （NGCS）, the excessive solute elements gradually segregate to the grain boundaries by the diffusion of the solute-vacancy complex during aging treatment. The grain boundary segregation plays an important role in the nucleation and growth of VRC, GP Ⅱ zones, η＇ phase as well as η phase.

SYNTHESIS AND CHARAOTERIZATION OF NOVEL THERMOTROPIO LIQUID ORYSTALLINE POLYESTERS BEARING NONLINEAR OPTICAL AZOBENZENE SIDE GROUP

A series of novel thermotropic liquid crystalline polyesters bearing nonlinear optical azobenzene side group were synthesized by high temperature solution polycondensation and their structures,thermal stability, phase transition behavior and crystallinity were characterized by IR,elemental analysis, TG-DTA, polarizing optical microscope (POM) equipped with a hot stage and X-ray diffraction techniques. The results demonstrate that all the synthesized polyesters exhibit nematic liquid crystalline phases and show relatively high glass transition temperatures and good thermal stability.

Design and construction of a film of mesoporous single-crystal rutile TiO_2 rod arrays for photoelectrochemical water oxidation

A film of mesoporous single-crystal rutile TiO2 rod arrays supported on a transparent conductive glass substrate was synthesized with the assistance of a template layer of closely packed silica nanospheres. This film was used as a photoanode and showed significant improvement for photoelectrochemical water oxidation compared with a reference film of nonporous single-crystal rutile TiO2rod arrays.

Flexoelectric-Induced Voltage Shift in Hybrid Aligned Nematic Liquid Crystal Cell

Flexoelectric-induced voltage shift in a weak anchoring hybrid aligned nematic fiquid crystai cell is investigated theoretically. Based on the elastic theory of liquid crystal and the variation method, the equations for the bulk and the boundary of the cell are derived. By computer simulation, the dependence of the shift voltage on the sum of the ttexoelectric coefficients and the anchoring energy strength is obtained. As a result, a novel method to determine the sum of the flexoelectric coefficients by measuring the shift voltage is put forward.

Two-Dimensional Spatial Solitons in Nematic Liquid Crystals

We study the propagation of spatial solitons in nematic liquid crystals, using the self-similar method. Analytical solutions in the form of self-similar solitons are obtained exactly. We confirm the stability of these solutions by direct numerical simulation, and find that the stable spatial solitons can exist in various forms, such as Oaussian solitons, radially symmetric solitons, multipole solitons, and soliton vortices.

Lattice Boltzmann Simulation of 3D Nematic Liquid Crystal near Phase Transition

Phase transition between nematic and isotropic liquid crystal is a very weak first order phase transition.We avoid to use the normal Landau-de Gennes's free energy that reduces a strong first order transition, and set up adata base of free energy calculated by means of Tao-Sheng Lin's extended molecular field theory that can explain theexperiments of the equilibrium properties of nematic liquid crystal very well. Then we use the free energy method oflattice Boltzmann developed by Oxford group to study the phase decomposition, pattern formation in the flow of theliquid crystal near transition temperature.

Extracting useful high-frequency information from wide-field electromagnetic data using time-domain signal reconstruction

The wide-field electromagnetic method is widely used in hydrocarbon exploration,mineral deposit detection,and geological disaster prediction.However,apparent resistivity and normalized field amplitude exceeding 2048 Hz often exhibit upward warping in data,making geophysical inversion and interpretation challenging.The cumulative error of the crystal oscillator in signal transmission and acquisition contributes to an upturned apparent resistivity curve.To address this,a high-frequency information extraction method is proposed based on time-domain signal reconstruction,which helps to record a complete current data sequence;moreover,it helps estimate the crystal oscillator error for the transmitted signal.Considering the recorded error,a received signal was corrected using a set of reconstruction algorithms.After processing,the high-frequency component of the wide-field electromagnetic data was not upturned,while accurate high-frequency information was extracted from the signal.Therefore,the proposed method helped effectively extract high-frequency components of all wide-field electromagnetic data.

Effect of 0.3% Sc on microstructure, phase composition and hardening of Al-Ca-Si eutectic alloys

The phase composition,microstructure and hardening of aluminum-based experimental alloys containing0.3%Sc,0?14%Si and0?10%Ca(mass fraction)were studied.The experimental study(electron microscopy,thermal analysis and hardnessmeasurements)was combined with Thermo-Calc software simulation for the optimization of the alloy composition.It wasdetermined that the maximum hardening corresponded to the annealing at300?350°С,which was due to the precipitation of Al3Scnanoparticles with their further coarsening.The alloys falling into the phase region(Al)+Al4Ca+Al2Si2Ca have demonstrated asignificant hardening effect.The ternary eutectic(Al)+Al4Ca+Al2Si2Ca had a much finer microstructure as compared to the Al?Sieutectic,which suggests a possibility of reaching higher mechanical properties as compared to commercial alloys of the A356type.Unlike commercial alloys of the A356type,the model alloy does not require quenching,as hardening particles are formed in thecourse of annealing of castings.

Influence of Surface Geometry of Grating Substrate on Director in Nematic Liquid Crystal Cell

The director in nematic liquid crystal cell with a weak anchoring grating substrate and a strong anchoring planar substrate is relative to the coordinates x and z.The influence of the surface geometry of the grating substrate in the cell on the director profile is numerically simulated using the two-dimensional finite-difference iterative method under the condition of one elastic constant approximation and zero driven voltage.The deepness of groove and the cell gap affect the distribution of director.For the relatively shallow groove and the relatively thick cell gap,the director is only dependent on the coordinate z.For the relatively deep groove and the relatively thin cell gap,the director must be dependent on the two coordinates x and z because of the increased elastic strain energy induced by the grating surface.

Computational Determination of the Binding Mode of α-Conotoxin to Nicotinic Acetylcholine Receptor

Abstract Conotoxins belong to the large families of disulfide-rich peptide toxins from cone snail venom, and can act on a broad spectrum of ion channels and receptors. They are classified into different subtypes based on their targets. The a-conotoxins selectively inhibit the current of the nicotinic acetylcholine receptors. Because of their unique selectivity towards distinct nAChR subtypes, a-conotoxins become valuable tools in nAChR study. In addition to the X-ray structures of a-conotoxins in complex with acetyleholine-binding protein, a homolog of the nAChR ligand-binding domain, the high-resolution crystal structures of the extracellular domain of the al and a9 subunits are also obtained. Such structures not only revealed the details of the configuration of nAChR, but also provided higher sequence identity templates for modeling the binding modes of a-conotoxins to nAChR. This mini-review summarizes recent modeling studies for the determination of the binding modes of a-conotoxins to nAChR. As there are not crystal structures of the nAChR in complex with conotoxins, computational modeling in combination of mutagenesis data is expected to reveal the molecular recognition mechanisms that govern the interactions between a-conotoxins and nAChR at molecular level. An accurate determination of the binding modes of a-conotoxins on AChRs allows rational design of a-conotoxin analogues with improved potency or selectivity to nAChRs.

Optical-field-induced memory effect of nematic liquid crystal doped with zinc porphyrin dimers

In this paper, the optical-field-induced reorientation ofnematic liquid crystal （5CB） doped with a volume fraction of 1.0% of zinc porphyrin dimers ο, ο-C2-（L-Thr）-C2-（TPP）2Zn（II）2 has been studied. Excited by 1.06 lain, YAG laser pulse with 10 ns pulse duration and 100 mJ pulse energy, both of the doped 5CB and pure 5CB perform the reorientation. When the exciting laser pulse withdraws, the doped 5CB retains the reorientation and without back to the initial orientation, and the memory effect is formed accordingly, whereas the pure 5CB relax to the initial orientation. A model considering the intermolecular coupling change between the dopant and host 5CB, and together with the aligning surface adsorption process of deformed dopant are present to explain this memory effect. In order to prove this mechanism, 5CB doped with another dopant （zinc porphyrin, ZnTPP） was used for contrast, which induces no such memory effect. This phenomenon is very useful to study the optical data storage and memory display.

P-channel Ge/Si Hetero-nanocrystal Based MOSFET Memory

The charge storage characteristics of P-channel Ge/Si hetero-nanocrystal based MOSFET memory has been investigated and a logical array has been constructed using this memory cell. In the case of the thickness of tunneling oxide Tox = 2 nm and the dimensions of Si- and Ge-nanocrystal Dsi = DGe = 5 nm, the retention time of this device can reach ten years(～1 × 108 s) while the programming and erasing time achieve the orders of microsecond and millisecond at the control gate voltage | Vg | = 3 V with respect to N-wells,respectively. Therefore, this novel device, as an excellent nonvolatile memory operating at room temperature,is desired to obtain application in future VLSI.

Phase Diagram of XY Model with Nematic Coupling on the Simple Cubic Lattice

Using cluster Monte Carlo method, we numerically investigate the coupling on the simple cubic lattice. We determine critical lines belong to the criticality in the XY model with nematic three-dimensional XY universality class in variable of θ （2θ） between the XY-ferromagnetic （nematic） and disordered states. Fhrthermore, the phase transition between the XY-ferromagnetic and the nematie states is found to be in the three-dimensional Ising universality class. The critical points are determined from the intersections of Binder ratios for various system sizes. With two sets of critical points obtained, we finally construct the phase diagram on the A-J plane.