快速生长大尺寸KDP单晶

用传统降温法生长了大尺寸KDP单晶,生长速度一般在1～2 mm/d,周期长,风险大.本文采用"点籽晶"快速生长法多次成功生长出了200 mm级的大尺寸KDP单晶,晶体生长速度达到20 mm/d,晶体生长正常.同时,摇摆曲线表明快速生长的晶体有着很好的结构完整性.     

连续铸造铜单晶的晶体取向与竞争生长

本文采用自制单晶连铸设备和X射线衍射方法研究连铸铜单晶的晶体取向与竞争生长.结果表明,在晶体演化过程中逐渐淘汰的晶面为(311)、(200)和(111),最后单晶生长的晶面为(200),连铸铜单晶的晶体生长方向为[100],晶体取向[100]与晶轴的偏离度小于10°.单晶生长时固液界面向熔体呈凸出形状,这有利于晶体生长过程中的竞争和淘汰.还发现了连铸铜单晶取向在一定范围内,并不是唯一取向的单晶.     

用数学模型计算生长大尺寸光学晶体加热系统结构第2部分-在Ф400mm CaF2晶体生长中计算辐射-传导热交换的方法和结果

大尺寸氟化物晶体的生长是基于对晶体炉热交换的实验研究和计算结果,在晶体生长过程的不同阶段解决了复杂结构生长容器的边界条件和温场的二维计算任务.我们在这里给出了晶体生长过程中温场设置和转变的具体数据.所有的计算都是根据晶体、熔体,容器材料的光学特性与光谱和温度的关系以及它们的热物理值与温度的关系做出的.这些结果包括了迄今有关氟化物晶体生长系统和过程的最精确的数据,可用于生长技术工艺的发展以及晶体生长炉和容器的设计.     

用数学模型计算生长大尺寸光学晶体加热系统结构第1部分-对φ400mmCaF2晶体生长加热系统计算的方法和结果

本文的计算方法是根据对晶体生长炉中温场和热交换状态的实验研究提出的.用这种计算已成功地生长出大尺寸的CaF2和BaF2晶体(直径φ400mm),计算方法的准确性已为实验所证实,在许多新建或现有的生长系统中,结果都证明这种计算方法对于解决一些生长和退火问题是有效的.这种方法被广泛地用于估计各种复杂结晶容器的边界条件和在大晶体生长各个阶段的连续温场处理模型.这一点非常重要,因为迄今除了计算以外还没有其它方法可用于分析碱卤化合物材料的熔体-晶体系统的热状态,在用Stockbarger技术中,这些实验结果被成功地用于发展生长设备.     

坩埚下降法生长CaF2单晶的研究

采用坩埚下降法生长了CaF2单晶体,研究了不同条件生长的单晶缺陷和光谱性能.结果表明:当晶体生长过程中进入水等含氧杂质时,所生长的晶体不仅在1500nm附近产生非常宽的OH-两倍振动吸收带,而且在可见-紫外波段也形成强烈的色心吸收带.同时,杂质离子Ce3+的存在也导致晶体出现306nm的吸收带.     

半导体单晶生长过程中的位错研究

阐述了现有的半导体单晶位错模型,即临界切应力模型和粘塑性模型的基本理论及应用状况.分析了熔体法单晶生长过程中影响位错产生、增殖的各种因素,以及抑制位错增殖的措施.与熔体不润湿、与晶体热膨胀系数相近的坩埚材料,低位错密度的籽晶可有效地抑制生长晶体的位错密度;固液界面的形状及晶体内的温度梯度是降低位错密度的关键控制因素,而两因素又受到炉膛温度梯度、长晶速率、气体和熔体对流等晶体生长工艺参数的影响.最后,对熔体单晶生长过程的位错研究进行了展望.     

红外LED用掺硅HB-GaAs单晶纵向载流子浓度分布研究

GaAs单晶作为一种重要的LED衬底材料在光电器件中应用十分广泛,但载流子浓度(C.C.)分布不均、杂质浓度过高等缺陷会严重影响相关器件的性能.为制备纵向载流子浓度分布均匀的掺硅HB-GaAs单晶,本文探讨了单晶生长过程中熔区长度对纵向载流子浓度分布的影响.以高纯GaAs多晶为原料,设定不同的拉晶温度曲线,采用窄熔区技术进行晶体生长研究,最终生长出C.C.值分布更均匀、位错密度低(EPD≤10 000 cm-2)的<111>向N型掺硅GaAs单晶.利用辉光放电质谱法(GDMS)和范德堡法霍尔效应测试对晶体进行了表征,单晶纯度达到5N且无硼杂质沾污.     

熔体分层对BaBiBO4晶体生长的影响

研究在用助熔剂法生长BaBiBO4晶体的过程中,熔体分层对晶体生长的影响.以Li2Mo3O10作为助熔剂,采用自发成核和顶部籽晶两种方法来生长晶体.对于这两种方法得到的晶体,用X射线粉末衍射及拉曼光谱进行了表征,结果显示,在晶体生长过程中,由于熔体分层,导致通过自发成核和顶部籽晶分别得到BaMoO4多晶和LiBaB9O15单晶两种不同的物相.     

微下拉法生长炉研制及其在BGSO混晶生长上的应用

基于垂直凝固原理设计并研制了适合中低温晶体生长的微下拉法生长炉.采用该生长设备成功生长出不同掺杂浓度的锗硅酸铋纤维晶体,讨论了工艺参数以及掺杂浓度对晶体生长的影响,所得纤维晶体的最大长度达到195 mm.测试了晶体XRD和发射光谱.结果表明,随着SiO2含量增加,Bi4(Ge1-xSix)3O12单晶的晶胞参数随着Si含量增加而减小,而Si掺杂使晶体主发射峰轻微地向短波方向移动.     

浸没籽晶法生长La2CaB10O19单晶的研究

采用浸没籽晶法以CaO-Li2O-B2O3为助熔剂生长出La2CaB10O19单晶.籽晶的方向对晶体质量有较大的影响.晶体结构导致生长出的晶体均呈现板状外形,并且容易沿(001)面解理;捆绑晶体的铂丝嵌入晶体加剧了晶体的解理.然而解理和铂丝嵌入对不同方向籽晶生长出晶体的质量影响各不相同,对于晶体生长过程溶质输运的影响也不相同,实验发现,[101]方向为本实验条件下最佳的晶体生长方向.     

CsI-LiCl共晶材料的坩埚下降法生长与闪烁性能研究

本文采用坩埚下降法,在真空密封的石英坩埚中成功生长出CsI-LiCl与CsI-LiCl:Na共晶闪烁体。通过扫描电子显微镜(SEM)观察晶体微结构表明该共晶中LiCl相与CsI相存在周期性的层状排列,CsI相的厚度在5 μm左右。共晶样品的X射线激发发射谱显示在CsI-LiCl和CsI-LiCl:Na共晶样品存在缺陷发光,在CsI-LiCl样品中还观察到了纯CsI的自陷激子(STE)发光。CsI-LiCl样品在α粒子激发下的多道能谱中观察到明显的全能峰,这一结果证明CsI-LiCl共晶可用于热中子探测的潜力。     

静电纺丝法制备CeO2微纳米纤维及其除氟性能

以聚丙烯腈(PAN)为载体,六水合硝酸铈[Ce(NO₃)₃·6H₂O]为原料,采用静电纺丝法制备了Ce(NO₃)₃/PAN纤维,在空气中热处理得到CeO₂微纳米纤维,通过XRD、BET和SEM对CeO₂微纳米纤维进行表征。采用静态吸附实验探讨了CeO₂微纳米纤维去除水溶液中氟离子的性能,考察了溶液pH值、初始氟离子浓度及共存阴离子等对吸附性能的影响。结果表明,pH=3时,CeO₂微纳米纤维对F^-的吸附性能最佳,CeO₂吸附量随着F^-浓度的增大呈上升趋势。CeO₂微纳米纤维对F^-的吸附等温线遵循Langmuir模型,二级动力学模型能很好地描述CeO₂微纳米纤维对F^-的吸附过程。CeO₂微纳米纤维的除氟性能优良,可为其实际应用提供理论参考。     

First-principles coexistence simulations of supercooled liquid silicon

We perform first-principles coexistence simulations of the low-density and the high-density phases of supercooled liquid silicon and find a negative slope for the coexisting line in the temperature-pressure plane. Electron density maps and electron-localization function plots of the two phases of silicon show marked differences. The calculated differences suggest more localized electrons in the low-density liquid compared to the high-density liquid, coming from an increased population of covalent bonds, which further explain the calculated negative slope in the two phase coexistence regime. This is consistent with the presence of a pseudo-gap in low-density liquid silicon, absent in the high-density liquid which shows a metallic behavior.     

Triethyl ammonium salt of O,O′-bis(p-tolyl)dithiophosphate, [Et3NH]+[(4-MeC6H4O)2PS2]−

Triethyl ammonium Salt of O,O′-bis(p-tolyl)dithiophosphate and O,O′-bis(m-tolyl)dithiophosphate have been obtained by reaction of p- and m-cresol, respectively with P₂S₅ in toluene and have been characterized by elemental analysis, IR, ¹H and ³¹P NMR spectroscopy. The molecular structure of O,O′-bis(p-tolyl)dithiophosphate has been determined. Crystal data: [Et₃NH]⁺[(4-MeC₆H₄O)₂PS₂]⁻: Monoclinic, P2₁/c, a=15.2441(9) ?, b=10.415(2) ?, c=3.9726(9) ?, β=91.709(7)°, V=2217.5(1) ?⁻³, Z=4.Supplementary materials Additional material available from the Cambridge Crystallographic Data Centre (CCDC no. 600927 for [Et₃NH]⁺[(4-MeC₆H₄O)₂PS₂]⁻ comprises the final atomic coordinates for all atoms, thermal parameters, and a complete listing of bond distances and angles. Copies of this information may be obtained free of charge on application to The Director, 12 Union Road, Cambridge CB2 2EZ, UK (fax: +44-1223-336033; email: deposit@ccdc.cam.ac.uk or www:http://www.ccdc.cam.ac.uk).     

Crystal structures of thecis andtrans isomers of dithiahexahydro[3.3]metacyclophane

Structures of both thecis andtrans isomers of dithiahexahydro[3.3]metacyclophane, ?C₆H₄?CH₂SCH₂?C₆H₁₀?CH₂SCH₂?, have been determined, wherecis andtrans refer to the attachments to the cyclohexane ring. Thecis form crystallizes in the monoclinic space groupP2₁/c witha=8.4299(11)Å,b=21.772(2)Å,c=8.9724(13)Å, β=116.574(11)^o, andZ=4. Thetrans isomer packs into the monoclinic space groupP2₁ witha=8.159(16)Å,b=10.185(5)Å,c=9.558(2)Å, β=112.435(18)^o, andZ=2. The cyclohexane ring of thecis isomer is in the chair conformation, while the cyclohexane of thetrans isomer is found in a twisted boat conformation.     

CTAB与SDBS对碳酸锶粒子生长形态调控及机理研究

以表面活性剂CTAB和SDBS为化学添加剂,采用化学共沉淀法对碳酸锶晶体的生长形态进行调控,成功地制备出了实心的树枝状和花瓣为空心的花状碳酸锶粉体,并用X射线衍射(XRD)、扫描电子显微镜(SEM)和傅里叶变换红外光谱(FT-IR)等分析手段对样品进行了表征;最后重点对化学添加剂可能产生的影响机理进行了初步的探讨.结果表明,CTAB和SDBS在晶体生长的过程中能起到显著的影响作用,两者对粒子分散性能的作用效果相反,而且后者对晶体(013)和(213)晶面表面能降低的贡献明显大于前者.     

Crystal structure of Zn4Na(OH)6SO4Cl·6H2O

The structure of Zn₄Na(OH)₆SO₄Cl·6H₂O, a secondary mineral from Hettstedt, Germany, was determined by single-crystal X-ray diffraction. The crystals are hexagonal,a=8.413(8),c=13.095(24) Å, space group $P\bar 3$ , Z=2. The structure was refined to R=0.0554 and R_w=0.0903 for 970 reflections with I≥3σ(I). The structure can be described as zinc hydroxide layers perpendicular toc, from which sulfates and chlorides extend. The layers are held together by a system of hydrogen bonds involving hexaaquo Na⁺ ions which occupy the interlayer space.     

Synthesis and Crystal Structure of 5-[2-(6-bromonaphthalenyloxymethyl)]-3-(4-morpholinomethyl)-1,3,4-oxadiazole-2(3<Emphasis Type="Italic">H</Emphasis>)-thione

Abstract  The title compound, C₁₈H₁₈BrN₃O₃S, a derivative of 1,3,4-oxadiazole, crystallizes in the triclinic space group P-1 with unit cell parameters a = 6.8731(3), b = 8.9994(4), c = 15.7099(6) ?, α = 92.779(3)°, β = 130.575(3)°, γ = 107.868(4)°, Z = 2. The dihedral angle between the mean planes of the planar naphthyl and morpholine (chair) rings with the planar oxadiazol ring is 50.1(8) and 76.8(6)°, respectively. The planar naphthyl ring is twisted 52.2(5)° with the mean plane of the morpholine ring. A group of four intermolecular close contacts are observed between a bromine atom and hydrogen atoms from the closely packed naphthyl, morpholine and oxy–methyl groups in the unit cell. These molecular interactions in concert with an additional series of π–π stacking interactions that occur between the center of gravity of the two 6-membered rings of the naphthalene group influence the twist angles of each of these three groups. A MOPAC AM1 calculation of the conformation energy of the crystal structure [226.0128(9) kcal] compared to that of the minimum energy structure after geometry optimization [29.9744(1) kcal] reveals a significantly reduced value. The twist angles of the three groups above also change after the AM1 calculation giving support to the influence of both intermolecular C–H···Br short-range interactions and Cg π–π stacking interactions on these angles which therefore play a role in stabilizing crystal packing. Graphical Abstract  Crystal structure of 5-{[(6-bromonaphthalen-2-yl)oxy]methyl}-3-(morpholin-4-ylmethyl)-1,3,4-oxadiazole-2(3H)-thione, C₁₈H₁₈BrN₃O₃S, is reported and its geometric and packing parameters described and compared to a MOPAC computational calculation. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

Crystal structure of irisolidone from the flowers of Pueraia lobata

Irisolidone (5,7-dihydroxy-6,4′-dimethoxyisoflavone) was isolated from the flowers of Pueraia lobata and its crystal structure was examined by X-ray single crystal diffraction. The crystal structure of irisolidone is monoclinic, space group P2₁/c with a = 15.491(9) ?, b = 7.895(4) ?, c = 13.321(7) ?, β = 110.546(9)° and Z = 4. Hydrogen bonding and aromatic π–π stacking assemble the title compound into a three-dimensional networking structure.