Macroscopic Alignment Control of Liquid Crystal Molecule in Optical Film for 3D Display

The optical film made of liquid crystal molecules can have useful anisotropic optical properties by controlling the alignment of molecules. In order to apply those films to commercial display, we have to know the way to control the thickness, appearance, refractive index, adhesion, and many properties in macroscopic scale. In this presentation, we show how can we control alignment of liquid crystal molecules in macroscopic scale and make the Film Patterned Retarder (FPR^TM) used in the polarization type stereoscopic 3D-displays.     

基于片状光束扫描的激光晶体内在缺陷表征方法

大尺寸激光晶体是高功率全固体激光器的关键组成部分,然而晶体生长过程中不可避免会产生气泡、包裹物等缺陷,影响激光器性能。为了快速、有效地评价晶体缺陷,本文搭建了基于片状光束扫描的晶体缺陷三维成像系统。系统中利用鲍威尔棱镜对532 nm的点状激光进行整形以获取片状激光,通过远心镜头和CMOS探测器获取晶体缺陷产生的散射光,从而获取晶体缺陷的面分布情况,同时利用高精度位移平台进行面阵的逐一扫描,完成晶体的三维立体分布扫描。进一步结合数字图像处理技术,表征晶体缺陷的面分布特征,并重构晶体缺陷的体分布特征。基于上述系统对尺寸约为50 mm×50 mm×100 mm的Yb∶YAG晶体内在缺陷进行测量,最小缺陷检测分辨率能够达到38.69 μm。本文为准确表征晶体的内在缺陷提供了新方法,同时也为晶体坯料的后期高精度加工提供了可视化的数据支撑。     

Liquid Crystals Nanocomposites for Photovoltaic Applications: Structural Properties

Nanocomposites consisting of liquid crystals and nanoparticles have been studied for their applications in devices, such as photovoltaics and to model biological devices. Understanding the structure the liquid crystal assumes in the vicinity of the nanoparticles, and how it compares to the bulk structure of the liquid crystals gives us an idea of how light, and electrons are transmitted from the liquid crystal to the nanoparticle and how sharp is this transmission. The structure depends on the functionalization (or lack of it) that the nanoparticle has and seems to reflect the faceting or the arrangement of the nanoparticle.     

3D printed models of small and large molecules,structures and morphologies of crystals,as well as their anisotropic physical properties

Three‐dimensional (3D) physical models of atomic structures of crystals, their anisotropic properties and morphologies as well as models of small and large molecules were printed with support from 3D Systems Corporation. Structural information in Crystallographic Information Framework (CIF) files from the Crystallography Open Database and the Protein Data Bank was utilized. Computer programs were either newly developed (Cif2VRML) or enhanced by 3D print file export functions (WinXMorph and WinTensor) in order to design most of these models. Current 3D printing technologies are briefly reviewed. The literature on the impact on students’ comprehension and retention of structural information with access to such models is assessed. Our taking of a historical perspective in this paper illustrates that the usage of models has for more than 200 years been an integral component of crystallography.     

零声表面波频率温度系数方向的硅酸镓镧晶体生长

采用提拉法生长了高质量、大尺寸、结构完整的声表面波零温度系数切向LGS晶体.XRD图谱显示,生长的晶体为单一相LGS晶体,晶格常数为a=0.816274 nm,c=0.509253 nm,密度为5.7463 g/cm3.压电常数、介电常数、热膨胀性能等与传统方向生长的晶体一致.用此方向生长的LGS晶体制作声表面波频率温度性能优化的切片,只需要垂直生长方向进行切割,可以大大简化晶体的加工工艺、提高LGS晶体的利用率,节省材料成本.     

陶瓷3D打印技术综述

本文介绍了陶瓷3D打印技术目前的发展状况、主要的成型技术和重要的应用领域,重点介绍3D打印技术在陶瓷方向的应用。回顾了可适用于直接三维打印和立体光固化法打印的氧化物( Al2 O3、ZrO2)和非氧化物( Si3 N4、SiC)陶瓷浆料的最新研究成果及成型技术对制品性能的影响,并展望了陶瓷3D打印技术未来的发展方向。     

三维生长温度对非故意掺杂GaN外延层性能的影响

利用金属有机化学气相沉积(MOCVD)技术在蓝宝石(0001)面上生长GaN外延层,并系统研究了三维生长温度对外延层晶体质量和残余应力的影响机理.利用高分辨X射线衍射仪(HRXRD)、原子力显微镜(AFM)、光致发光光谱仪(PL)和拉曼光谱仪(Raman)分别对外延层的位错密度、表面形貌、发光性能和应力情况进行了分析.当三维生长温度分别为1060℃、1070℃和1080℃时,外延层刃位错密度分别为5.09×108/cm3、3.58×108/cm3和5.56×108/cm3,呈现先减小后增大的现象,而螺位错密度变化不显著,分别为1.06×108/cm3、0.98×108/cm3和1.01×108/cm3,同时外延层残余应力分别为0.86 GPa、0.81 GPa和0.65 GPa,呈现逐渐减小的趋势.这可能是由于三维生长温度不同时,外延层生长模式和弛豫程度发生改变所致.     

3D direct ink writing fabrication of high-performance all-solid-state micro-supercapacitors

Abstract

We present the fabrication of flexible all-solid-state micro-supercapacitors (MSCs) by using 3D direct-ink-writing (DIW) technique. The conductive poly(3,4-ethylenedioxythiophene)-poly(styrenesulfonate) (PEDOT:PSS) ink was printed by layer-by-layer fashion on flexible substrates. The MSC electrodes exhibit smooth surface and low sheet resistance. The flexible MSC fabricated by 3D DIW exhibits the areal capacitance per electrode of 31.6 mF cm^?2, gravimetric capacitance of 15.6?F g^?1, an energy density of 0.36 µWh cm^?2, and power density of 80?µW cm^?2. The flexible MSC shows high cyclic and bending stability. We believed that the optimized 3D DIW fabrication has potential for roll-to-roll 3D printing flexible all-solid-state MSCs.     

Growth,Ferroelectric Properties,and Phonon Modes of YMnO3 Single Crystal

YMnO₃ single crystals were grown by flux method and plate‐like single crystals with the c‐axis perpendicular to the surfaces were obtained. The maximum size of these crystals was about 2 × 2 × 0.07 mm³. Ferroelectric properties were measured at various frequencies and abnormal behavior at the low frequencies were observed and discussed using non‐linear current‐voltage behavior. Raman and IR spectra were obtained, and those results were compared with previous work.     

3D Solid-State Network from Hierarchical Supramolecular Self-Assembly of Transition Metal Complexes of Pyridine Based Ligand

Abstract  The crystal structures of [Cu(py)₄(ClO₄)](ClO₄) (1), [V(pic)₂(OH)](NO₃)₂ · H₂O (2) and [Ni(H₂O)₆][Ni(dpa)₂] · 2H₂O (3) [py = Pyridine, picH = Pyridine-2-carboxylic acid, dpaH₂ = Pyridine-2,6-dicarboxylic acid] was determined by single-crystal X-ray diffraction techniques. Solid-state structural analysis shows that all these complexes from extensive 3D network structure via supramolecular self-assembly. The crystal structures are stabilized by extended hydrogen bonding interactions. The complex 2 forms orange V₂O₅ micro spheroids when heated at ~400 °C for 6 h. Graphical Abstract  Hierarchical supramolecular self-assembly of transition metal complexes of pyridine based ligands in crystal. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

3m点群晶体纵向压电性能的研究

本文详细地介绍了通过坐标变换研究晶体压电性能随空间变化的方法.在以前的工作基础上,对LiNbO3、LiTaO3和PZT60/40等3m点群晶体纵向压电系数d33及机电耦合系数k33在空间分布的共同规律进行了归纳总结,发现它们在空间中的分布具有明显的各向异性,并存在着一些特殊方向,沿这些方向,晶体的压电性能有较大幅度的提高.在此基础上,本文还根据不同文献中报道,对另一著名的3m点群晶体β-BaB2O4的压电系数数据进行了比较和分析.     

Studies of EPR g factors for tetragonal and rhombic Cr5+ centers in ferroelectric PbTiO3

The anisotropic g factors (g_x, g_y, g_z) at low temperature and the motionally averaged isotropic g factor at high temperature for two Cr⁵⁺ centers, the tetragonal t‐Cr⁵⁺ center and the rhombic O‐Cr⁵⁺ center, in ferroelectric PbTiO₃ are calculated from the high‐order perturbation formulas based on a two‐mechanism model. In the model, the contributions to g factors from both the crystal‐field (CF) mechanism concerning the CF excited states and the charge‐transfer (CT) mechanism (which is neglected in CF theory) concerning the CT excited states are contained. The calculated results are in reasonable agreement with the experimental values. From the calculations, the defect models of t‐Cr⁵⁺ center (which is attributed to Cr⁵⁺ in the tetragonally‐compressed octahedron caused by Jahn‐Teller effect rather than in the tetragonally‐elongated octahedron in the host PbTiO₃) and O‐Cr⁵⁺ center (which is due to the t‐Cr⁵⁺ center perturbated by the electrical polarization perpendicular to the C₄ axis) are confirmed, and the defect structure of t‐Cr⁵⁺ center is obtained. It is found that in the precise calculations of g factors for the high valence state d¹ ions in crystals, both the contributions due to CF and CT mechanisms should be taken into account. (© 2012 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Synthesis and crystal structure of a novel 3D supramolecular complex [Na(DC18C6-B)][Ni(mnt)<Subscript>2</Subscript>]

A supramolecular complex [Na(DC18C6-B)][Ni(mnt)₂] (1) (DC18C6-B = cis-anti-cis-dicyclohexyl-18-crown-6, isomer B; mnt = maleonitriledithiolate) has been prepared and characterized by elementary analysis, FT-IR spectroscopy and X-ray single crystal diffraction. It crystallizes in triclinic, space group P1 with crystallographic data: a = 7.974(4) Å, b = 14.343(7) Å, c = 15.559(8) Å, α = 96.230(8)^∘, β = 100.361(8)^∘, γ = 93.849(9)^∘, V = 1733.2(15) ų, Z = 2, D_calcd = 1.408 g/cm³, F(000) = 766, R₁ = 0.0491, wR₂ = 0.1018. The formula unit contains one [Na(DC18C6-B)]⁺ complex cation and one [Ni(mnt)₂]⁻ complex anion, which are constructed into an infinite chain-like structure through Na–N bonds. The resulting chains crisscross on the [Ni(mnt)₂]⁻ complex anions and further assemble into an unusual 3D supramolecular framework via the weak interactions.     

零维钙钛矿结构Cs3Cu2Br5单晶的生长和X射线探测性能

金属卤化物低维钙钛矿具有高效的发光性能,并且作为闪烁体在辐射探测领域表现出极大的潜力。本文采用布里奇曼坩埚下降法生长出全无机零维钙钛矿结构Cs₃Cu₂Br₅单晶。研究了Cs₃Cu₂Br₅的光学吸收、光致激发和发射,时间分辨光致发光和以及X射线探测性能。Cs₃Cu₂Br₅晶体结构为正交晶系,空间群为Pnma。在X射线激发下,Cs₃Cu₂Br₅晶体具有峰值约为467 nm的宽带发射,该发射来自自陷激子发射。Cs₃Cu₂Br₅的稳态光产额约为4 000 ph./MeV,且X射线余辉性能表现与BGO晶体相当。     

MEMS用Si台面及SiO2/Si衬底上3C-SiC的LPCVD生长

本文报道用在Si台面及热氧化SiO2衬底上3C-SiC薄膜的LPCVD生长,反应生长使用的气体为SiH4和C2H4,载气为H2,采用光学显微镜、X射线衍射（XRD）、X射线光电子能谱（XPS）、扫描电镜（SEM）、以及室温Hall测试对所生长的3C—SiC材料进行了测试与分析,结果表明在3C-SiC和SiO2之间没有明显的坑洞形成。     

Al2O3:V2+晶体自旋哈密顿参量的理论解释

在考虑微小磁相互作用(包括SS、SOO和OO作用)的基础上,采用全组态完全对角化方法,建立了A l2O3晶体中V2 离子的局域结构与自旋哈密顿参量定量关系,对A l2O3:V2 晶体基态和激发态零场分裂以及基态g因子等自旋哈密顿(SH)参量给出了统一的解释。结果表明,V2 离子进入A l2O3晶体后,上下配体氧平面分别沿C3轴向远离三角中心的方向移动了0.0021nm和0.0020nm。理论计算结果与实验值符合甚好。     

Spin‐Hamiltonian parameters for Dy3+ ion at the trigonal 12‐fold coordinated La3+ site of La2Mg3(NO3)12·24H2O

The spin‐Hamiltonian parameters (g factors g_‖, g_⊥ and hyperfine structure constants ¹⁶¹A_‖, ¹⁶¹A_⊥, ¹⁶³A_‖, ¹⁶³A_⊥) for ¹⁶¹Dy³⁺ and ¹⁶¹Dy³⁺ isotopes in the trigonal 12‐fold coordinated La³⁺ site of La₂Mg₃(NO₃)₁₂·24H₂O crystal are calculated from a diagonalization (of energy matrix) method. In the method, the Zeeman and hyperfine interaction terms are added to the conventional Hamiltonian used in the studies of crystal‐field energy levels, and a 66×66 energy matrix concerning the ground multiplet ⁶H_15/2 and the first to fifth excited multiplets ⁶H_13/2, ⁶H_11/2, ⁶H_9/2, ⁶H_7/2 and ⁶H_5/2 are applied. The calculated results are discussed. (© 2010 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

熔体法制备无机钙钛矿半导体核辐射探测晶体与器件的研究进展

钙钛矿材料在太阳能电池和光电探测等领域的快速发展,带动了其在核辐射探测领域的应用研究。钙钛矿晶体结构拥有多样化的结构容忍性,如何设计组分并挖掘材料的相关特性具有很大的科学挑战。其次,针对新型钙钛矿材料特性,需要根据应用场景来优化半导体器件设计,才能最大限度地发挥其辐射探测性能。鉴于此,本文从熔体法晶体生长及半导体器件设计等角度,探讨了不同维度钙钛矿结构的材料特性及辐射探测器件性能,以期为该材料在核辐射探测领域的发展提供参考。     

太赫兹声子极化激元在LiNbO3微结构中的衍射和干涉动态过程的时间分辨成像

利用飞秒激光脉冲,在50μm厚的铌酸锂晶体薄片中产生了太赫兹声子极化激元波.使用飞秒加工技术在铌酸锂晶体薄片上刻制了针对太赫兹声子极化激元波的衍射和干涉微结构.利用已经构建的偏振门探测成像系统实时动态地记录了太赫兹声子极化激元波的时间和空间传播过程.对不同频率的声子极化激元波在不同尺寸狭缝的动态衍射和干涉的过程进行了时间分辨的二维成像探测和分析,直观地展示了其衍射和干涉的时空特性.     

Investigations of spin‐Hamiltonian parameters and defect structures for two tetragonal Cu2+ centers in KTaO3 crystal

Based on the defect models that the two tetragonal Cu²⁺ centers in KTaO₃ are due to Cu²⁺ ions at Ta⁵⁺ sites associated, respectively, with one and two oxygen vacancies (V₀) along C₄ axis because of charge compensation, the spin‐Hamiltonian parameters (g factors g_‖, g_⊥and hyperfine structure constants A_‖, A_⊥) of both Cu²⁺ centers in KTaO₃ are calculated from the perturbation theory method (PTM) and the complete diagonalization (of energy matrix) method (CDM). The calculated results from both theoretical methods are not only close to each other, but also in reasonable agreement with the experimental values. This suggests that both methods are effective in the explanations of spin‐Hamiltonian parameters for 3d⁹ ions in tetragonal symmetry. From the calculations, the defect models are confirmed and the defect structural data are obtained for both Cu²⁺ centers in KTaO₃. (© 2010 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)