GdVO4晶体的生长及其性能研究

采用提拉法沿a轴和c轴生长出无色透明的GdVO4单晶,质量均超过50g.用X射线荧光分析法测得两个主要元素Gd和V的分凝系数都接近1.室温下测量了GdVO4晶体的X射线粉末衍射图,确定所获GdVO4晶体属于四方晶系,D194h-I41/amd空间群.通过晶体的锥光干涉图确定GdVO4晶体为单轴晶,光轴方向平行于c轴且光学均匀性比较好.利用高分辨X射线衍射仪测量GdVO4晶体的摇摆曲线,结果表明生长的GdVO4晶体的晶格完整性较好.通过浮力法测得其室温下密度为5.478g/cm3.透过波谱表明透过波长大于340nm.     

Nd:YbVO4激光晶体的生长及热学性质

用提拉法沿a轴和c轴成功生长出质量优良的Nd:YbVO4新型单晶.采用HRXRD-D5005型高分辨X射线衍射仪测得晶体的摇摆曲线,可以测得(400)面的半峰宽为70.92″,(004)面的半峰宽为19.80″.测得掺杂浓度为1;原子分数Nd:YbVO4晶体中Nd离子的有效分凝系数Keff为0.54.在298.15～573.15K温度范围内测量了晶体的热膨胀系数,αa=2.6×10-6/K,αb=2.5×10-6/K,αc=8.7×10-6/K;测得比热值为0.45～0.65J/g·K.测量了晶体的热扩散系数a,从而得到了其热导率λ.     

大尺寸优质激光晶体Nd3+/Yb3+∶NaY(WO4)2的生长和性能研究

采用提拉法生长了尺寸为φ25 mm×100 mm的大尺寸Nd3+与Yb3+掺杂的NaY(WO4)2晶体.对晶体的生长习性进行了讨论,利用XRD对晶体进行了相分析.测试了晶体的热膨胀特性,得到了主轴方向的热膨胀系数,测得沿c轴的膨胀系数大约为a轴的两倍.在室温下测试了Yb3掺杂的NaY( WO4)2晶体的吸收谱、荧光光谱和相关能级的荧光衰减,用标准与改进的J-O理论分析了吸收光谱与荧光光谱.结果表明,Yb3+掺杂的NaY( WO4)2晶体有着较好的光谱性能参数.采用氙灯泵浦Nd3+掺杂的NaY( WO4)2,实现了1.06 μm波段786 mJ的激光输出,同时在LD泵浦下,采用LBO晶体倍频,实现了87 mW的激光输出,基频光光转换效率为25;,斜率效率为7.98;.     

新型钨青铜型晶体Ca0.28Ba0.72Nb2O6的生长研究

研究了Ca0.28Ba0.72Nb2O6 (CBN-28)多晶料的制备和单晶的生长,用提拉法成功生长出CBN-28单晶.从X射线粉末衍射数据计算了CBN-28晶体的晶胞参数,并对其粉末衍射图各衍射峰进行了指标化.CBN晶体属四方晶系4mm点群.晶胞参数为a=1.2432(±2)nm,c=0.3957(±1)nm.采用浮力法测得其平均密度为5.372g/cm3,测得其莫式硬度为7,并通过测量CBN-28的介电性质,确定其居里点为260℃.     

K2Al2B2O7晶体的热学性质研究

K2Al2B2O7(KABO)晶体是近年发现的一种有应用前景的深紫外非线性光学晶体,也是目前唯一一种可以生长出大尺寸单晶的BO3基团非线性光学晶体.KABO有可能用于固态激光器的266nm及193nm高功率输出.本文对该晶体的物理化学性质及热学性质进行了研究,KABO晶体不潮解,不溶于水、酒精等溶剂,可溶于盐酸,硝酸和磷酸等强酸;测得莫氏硬度为5.5～6.5,用浮力法测得其密度为2.47g/cm3;用差热分析(DTA)方法测量其熔点为1109.7℃.用热重分析(TGA)方法结合分解产物的粉末X射线衍射(XRD)分析,确定KABO在900℃以上开始分解,分解产物主要为KAl11O17和K2Al24O37;用热机械分析仪测量了其热膨胀系数,沿物理学轴X、Y、Z方向分别为8.4×10-6/K、7.7×10-6/K、1.65×10-5/K.在室温至300℃温度范围内测量了KABO晶体的比热变化,比热随温度的升高线性增大.在47.6℃和294.6℃时比热分别为1.0084J/g℃与1.39J/g℃.     

β-Zn3BPO7晶体的提拉法生长研究

采用提拉法生长β-Zn3BPO7(简称ZBP)晶体.研究了生长工艺,用[210]方向的籽晶,获得了尺寸为35mm×20mm×10mm的单晶,该晶体无色透明,不开裂,呈现发育完好的{001}板面.通过设计特殊的温场以及在生长结束后采用适当的热条件有效地抑制了相变的发生.生长过程中靠近液面的温度梯度为30～60℃/cm,晶体转速为15～25r/min,提拉速度不大于1mm/h.ZBP晶体有宽的透光范围,它的紫外吸收边为240nm.ZBP晶体不潮解,其莫氏硬度为5Mohs.     

硼酸锶钡(Ba0.87Sr3.13B14O25)晶体的生长、结构和性质研究

本文报道了一种新的硼酸盐化合物-Ba0.87Sr3.13B14O25,采用泡生法已生长出尺寸为35mm×25mm×5mm的晶体.该晶体为单斜晶系,C2/m空间群,a=1.6425(3)nr,b=0.77739(16)nm,c=1.6665(3)nm,β=119.22(3)°,Z=4.结构中B3O8六元环通过O原子和BO3三角形相互连接,构成三维的硼氧阴离子骨架,金属阳离子占据多面体间的空隙.测量了BSBO晶体的透过谱,该晶体的显微硬度为578kg/mm2.     

有机非线性光学晶体DAST的生长、形貌及透过光谱

采用自发结晶法和籽晶法制备了4-(4-二甲基氨基苯乙烯基)甲基吡啶对甲基苯磺酸盐(DAST)晶体,所得晶体尺寸为10 mm×10mm 1～2 mm.研究了不同生长位置对生长习性和晶体形貌的影响,在溶液中部或顶部生长时DAST晶体倾向于沿a轴方向生长,晶体呈片状;在溶液底部时DAST晶体c轴方向生长加快,晶体呈块状.测试了DAST晶体(001)面X射线衍射摇摆曲线,对比分析了不同生长方法对晶体质量的影响.另外,对所制备的DAST晶体的透过光谱及吸收系数进行了研究.     

Bridgman法生长Cr∶LiCAF晶体及其闪光灯泵浦性能

本文报道了用Bridgman法生长的优质大尺寸Cr∶LiCAF晶体及其闪光灯泵浦性能研究.晶体尺寸达φ10×120mm和φ20×100mm,光学质量优良.用氙灯泵浦φ4×70mm的Cr∶LiCAF激光棒,在注入能量为137J时,获得了1.84J的能量输出,测得晶体的斜效率为2.38;,无损耗效率为4.31;.     

Nb∶KTiOPO4晶体的生长和倍频性能

通过研究晶体生长工艺参数对Nb∶KTiOPO4(Nb∶KTP)晶体生长的影响,用熔盐顶部籽晶法获得尺寸为55mm×25mm×5mm的Nb∶KTP透明单晶.研究中发现熔体的温度梯度、籽晶和降温速率将严重影响Nb∶KTP晶体的生长.Nb离子的引入不利于Nb∶KTP晶体的生长,尤其是造成晶体易开裂,且沿a轴方向生长速度非常缓慢.同时,Nb的引入大大改变Nb∶KTP晶体的倍频性能.掺杂Nb浓度的摩尔分数为13;时,Nb∶KTP晶体的倍频的Ⅱ型相位匹配的截止波长缩短至937nm,且有效产生469nm倍频蓝光;掺杂Nb浓度的摩尔分数为3;时,Nb∶KTP晶体对Nd∶YAG的1.0642μm激光倍频的最佳相位匹配角为θ=88.32°,()=0°,非常接近90°非临界相位匹配方向.     

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。     

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.     

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。     

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.     

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 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.