Holographic Diffraction Grating Controlled by Means of Nematic Liquid Crystal

Results are reported on the investigations on an electrically controlled phase holographic grating. It has a nearly sinusoidal profile with 1,4.μm deep grooves spaced at 12,5μm. The control voltage applied to the nematic liquid crystal has an amplitude of 0-25V and frequency 1-10 kHz. A light beam from a He-Ne laser (0,633μm) with a palarization parallel, perpendicular and at 45° the grooves of the grating is used.     

微波水热法合成新型CZBO晶体的研究

本文报道了微波水热法生长晶体硼酸锌镉(CZBO)的研究,合成出新物质(Cd0.01Zn0.99)2BO3(OH).用多晶XRD粉末衍射、元素分析、扫描电镜、红外光谱、热分析等多种手段对产物进行了表征.所得的CZBO微米级晶体呈长条状,其粉末倍频效应是KDP微晶的1.25倍.     

ECR-PECVD制备n型微晶硅薄膜的研究

用电子回旋共振等离子体增强化学气相沉积(ECR-PECVD)的方法制备了磷掺杂微晶硅薄膜材料.通过Hall,Raman光谱和XRD的测试分析,研究了衬底温度和磷烷流量对掺杂薄膜组织结构和电学性能的影响.根据AFM照片分析了薄膜的表面形貌,进而推测了薄膜的内部组成.实验发现:衬底温度在250 ℃时,磷烷的加入会大大降低薄膜的晶化率.衬底温度提高到350 ℃后这种影响明显下降.薄膜的载流子浓度和电导率受薄膜晶化率影响明显,衬底温度的升高对薄膜电学性能提高有较大帮助.     

氧化锌微晶管制备及其表征

以H2O2活化的锌粉和活性炭为原料制备了氧化锌微晶管,并运用XRD、SEM、PL、Raman等技术对所制备的样品进行表征.结果表明,所制备的氧化锌微晶管外壁切面为六边形、管长/管径较大的一维管状结构.激发波长为380 nm时,晶体光致发光分别为紫外近带边(383 nm)和绿光发射峰(500 nm),但绿光发射峰强度远不如紫外近带边发射峰,制备的氧化锌微管晶体缺陷密度较低且晶体的质量较好.     

水热法合成Mnx Zn1-xO微晶体

本文采用水热法合成了MnxZn1-xO晶体,水热反应条件为3mol·L-1KOH作为矿化剂,填充度为35;,温度为430℃,在Zn(OH)2中添加一定量的MnO2为前驱物,反应时间为24h.通过X射线能谱仪测量了晶体中的Mn含量,随着前驱物中MnO2含量的增加,晶体中Mn的原子百分比随着增加,Mn最大原子百分比含量超过了2;,晶体的形貌具有纯ZnO晶体的六角柱形特征.显露柱面m{1010}、锥面p{1011}、负极面O面{0001}和正极面{0001}.晶体直径为50～200μm,高度为20～100μm.     

Determination of the Bone Mineral Crystallite Size and Lattice Strain from Diffraction Line Broadening

Diffraction line broadening observed for the biological apatite is ascribed to small crystallite dimensions and lattice imperfections. However, it is rather difficult to separate the individual contribution of each factor. Therefore in numerous works a total inverse width of a diffraction peak is only used as a size/strain parameter. Several authors determine the bioapatite crystallite size ignoring the lattice strain. As is shown in the present paper, this problem can be resolved for oriented specimens. The crystallite size and lattice strain were calculated by two independent methods: Fourier analysis and approximation with threefold convolution of X‐ray lines. The approach proposed can be useful in the investigations into structural aspects of the bone apatite and its synthetic analogues as the crystal size is related to surface defects and the lattice strain to lattice imperfections.     

X-Ray Diffraction by Liquid Crystals

Following a very brief historical review, x-ray diffraction by nematic and smectic liquid crystals is critically examined in terms of the data available and the structural models and molecular theories that have been proposed to explain it. Studiesof TBBA are used to illustrate some of the principal mesophases that have been distinguished. Other types of liquid crystals and their phase transitions are also briefly reviewed.

This analysis shows that careful experimental work is still needed to decide the kinds of models that best describe the various types of mesophases that have been shown to exist.     

染料吸附对氯化银微晶表面结构的影响

利用微波吸收相敏检测技术测量了纯氯化银微晶的光电子衰减曲线,再结合光电子衰减动力学方程,确定了微晶表面和内部的电子陷阱参数,并以此为基础分析了染料的吸附对微晶表面结构的影响。发现吸附不仅会在微晶表面产生填隙银离子同时会对表面陷阱产生修饰作用,且随着染料吸附量的减少,产生银离子的作用退化并最终消失,而修饰作用凸现并逐渐增强,直至填隙银离子不再产生,修饰作用也达到了最大,随后修饰作用将随染料吸附量的继续减少而变弱。     

溶剂热法制备翠玉状Fe3O4微晶及表征

采用溶剂热法合成粒径为1～2 μm的翠玉状的Fe3O4晶粒.样品物相用X射线衍射(XRD)仪表征,形貌通过电子扫描显微镜(SEM)观测.所得样品的磁性用振动样品磁强计(VSM)测试,结果显示出铁磁性:饱和磁化强度Ms为89.7 emu/g,剩余磁化强度Mr为6.7 emu/g,矫顽力Hc为107.1 Oe.     

X射线衍射双峰的Voigt峰形函数拟合

给出了Voigt函数的一种计算方法,同时给出了一种用Voigt峰形函数拟合由Kα1、Kα2引起的晶体X射线双峰衍射谱的一种算法,此算法可同时对多个衍射双峰进行拟合和分峰,从而给出较准确的衍射峰宽度,用于计算晶体颗粒尺寸和应力等.用此算法计算了纳米GSGG的颗粒度,结果表明:在低角度,双峰叠加对衍射峰的半高全宽的影响可忽略,而在高角度双峰的衍射间隔加宽,使计算获得的粒度明显偏小.     

Investigation of the Cholesteryl Oleate Mesophases by X-Ray Diffraction

The following phase transitions occurring in the cholesteryl oleate were investigated by X-ray diffraction: solid-isotropic liquid, isotropic liquid-cholesteric, cholesteric-smectic.

The sample purity was 98%. Strong pretransitional effects were observed at the solid-isotropic liquid phase transition and at the cholesteric-smectic phase transition.

At this last transition the longitudinal coherence length ξ_∥ appears to diverge as the critical temperature is approached in the cholesteric phase, whereas the transversal coherence length ξ_τ increases at the critical temperature in the smectic phase in an abrupt way. It seems from the temperature dependence analysis of the angular position of the low angle peak that the smectic phase is a smectic A phase and that a progressive melting of chains occurs at the temperature increases.     

硫增感AgBrCl立方体微晶中光电子衰减行为的研究

利用微波吸收相敏检测技术并结合短脉冲激光曝光,测量了硫增感条件下AgBrCl立方体微晶感光材料的光电子时间衰减谱.分析了光电子一级衰减区域与增感温度的关系,确定了硫增感的陷阱效应对光电子衰减时间和光电子不同一级衰减区域的影响,并获得了增感过程中生成浅电子陷阱效果的最佳增感条件.     

Crystal Structure of Fibrillar Sodium Trimolybdate Hydrate by Powder Diffraction Method

The crystal structure of polycrystalline fibrillar sodium trimolybdate Na₂Mo₃O₁₀. 3 H₂O, has been solved ab initio by Powder Diffraction – Direct Methods package POWSIM. The structure was refined by the Rietveld method with final discrepancy factors R_F = 6.9 and R_wp = 17.1%. The structure consists of polymeric chains of Mo-O polyhedra parallel to the b axis. The space group is C2/m (12), a = 17.179(1), b = 3.7757(3), c = 10.8571(8) Å, β = 115.417(6)°, V = 636.06(6) ų, Z = 2.     

Diffraction reflection of a focused X-ray wave by a multilayer crystal

The Bragg diffraction of a narrow X-ray beam in a multilayer crystal is studied in the reflection geometry. It is shown by computer simulation of the experiment that strong integrated kinematic reflection occurs at any boundary of a multilayer crystal at the point of intersection of a narrow beam with the boundary. In contrast to the dynamic diffraction of a plane wave, attenuation of a narrow incident beam due to the reflection is small in comparison with the conventional absorption. As an example of a multilayer crystal, a Fabry-Perot interferometer is considered, which consists of two 70-μm-thick crystal Si layers separated by a 100-μm-thick air layer. The 12 4 0 reflection is studied at a photon energy of 15 keV. Three methods of formation of a narrow beam are considered: wavefront limitation by a slit, focusing with a parabolic lens, and focusing with a zone plate. It is shown that, for a local analysis of the thickness of layers and scattering parameters, the method of parabolic lens focusing has some advantages in comparison with the other methods.     

Change of the X‐Ray Polarisation State by Diffraction

An introduction to polarisation phenomena observed at X‐ray diffraction is given. Using an arrangement being analogous to optics of visible light, the polarisation state of the diffracted beam has been investigated using quarter wave plates. Depolarisation phenomena at the excitation of a noncoplanar many‐beam geometry are shown for lithium fluoride samples. The results are explained in terms of incoherent diffraction, as known from light optics.     

Reconstruction of Dislocation Potential Relief by Means of Self-Blocking Effect

The effect of dislocation self-blocking in intermetallic compounds with an anomalous temperature dependence of yield stress has been theoretically and experimentally analyzed. In essence, this effect is a dislocation self-immersion in a deep potential relief valley (without external stress). The possibility of reconstructing the relief shape (from one-valley to two-valley) is shown and the relief parameters are reported. The allowed and forbidden regions for self-blocking are revealed. The method for determining the ratio of the valley depths by measuring the self-blocking limiting angles between the dislocation segments is proposed. Transmission electron microscopy images of the dislocation structure can be used to this end. As an example, this ratio is estimated for a superpartial dislocation sliding in the cube plane in Ni₃Ge.     

Study of Cholesteric Textures in Phase Change Devices by Laser Light Diffraction

Photographic-recording and photomultiplier-recording laser light diffractometers have been constructed and used to study the cholesteric textures in phase change devices as a function of applied voltage and device parameters. The focal conic texture formed with increasing voltage gives diffraction peaks corresponding to 2π rotations of the director, whereas the texture formed by slow nucleation with decreasing voltage also gives “superlattice” lines corresponding to a 4π repeat, due to the different local structures of the textures combined possibly with tilting of the director. The repeat distances obtained by indexing the diffraction patterns agree well with microscopical and infra-red reflectance observations. Laser light diffraction appears to be a powerful technique for quantitative study of the non-uniform unwinding and re-forming of cholesteric twist in an electric field.