4.0～5.5GPa压力下硬玉翡翠的合成与表征

模拟天然硬玉成矿原理,采用优化的合成工艺,以硅酸铝和硅酸钠为原料制备出玻璃料,在高温高压下将非晶质的硬玉成分粉末转化为晶态硬玉.合成硬玉质地温润细腻、色泽均匀,具有高档硬玉的品质.XRD和SEM分析结果表明合成样品结晶矿物为硬玉(NaAlSi2O6),且结晶程度较好,晶粒细密,具有与天然硬玉相似的柱状纤维编织结构.在4.0～5.5 GPa压力条件下研究发现,随着压力的增加,硬玉合成温度随之增加;温度对合成硬玉晶粒的成长和编织情况有很大的影响;利用FTIR检测合成硬玉,其红外特征峰与天然硬玉一致,表明其分子结构为硅氧四面体结构;检测合成硬玉的硬度和密度等常规宝玉石参数与天然硬玉接近.     

人工合成翡翠研究进展

几个世纪以来,随着工艺技术以及珠宝行业的蓬勃发展,有着“玉石之王”之称的翡翠在装饰和收藏方面的需求量日益激增。但翡翠在自然界中的形成条件极其苛刻,导致其供应量难以满足人们的需求。因此,人工翡翠合成技术的发展对于解决天然翡翠供给不足的问题大有裨益,不仅能够推进翡翠高产化,还能加快其市场化进程。现有的人工合成翡翠的主流工艺大多采用高温高压法,该方法的关键是翡翠前体的合成以及玻璃质非晶硬玉到硬玉的转化。在这个过程中,找到一种条件相对温和的翡翠前体合成方法成为了人工合成翡翠的难点和突破点。本文论述了近年来国内外翡翠合成的最新研究热点和应用情况,着重介绍了固相烧结法、化学合成法和溶胶凝胶法三种翡翠前体常规制备技术。并从不同的制备技术路线出发,评估了各种方法的优缺点,同时对未来人工合成翡翠领域的发展进行了展望。     

6.0GPa下NaAlSi2O6翡翠的合成与表征

通过模拟天然翡翠的形成机理,对高温高压技术和玻璃料制取工艺的优化,以Na2SiO3·9H2O和Al2(SiO3)3为原料并添加少量致色剂CrO3,在超高压6.0 GPa下实现玻璃料由非晶态向晶态转化.通过XRD、FTIR和SEM等方法对样品进行表征,实验结果表明:6.0 GPa、1530℃条件下合成样品呈现翠绿色,质地温润,具有较高的润度和透明度;样品主要成分为NaAlSi2 O6,结晶度较高,分子结构为硅氧四面体结构,晶粒细密,致密有序;合成翡翠的硬度和密度等常规宝玉石参数也与天然翡翠接近,我们的研究对于探究翡翠在超高压下形成提供了数据参考.     

一种翡翠仿制品-透辉石微晶玻璃显微结构及晶体化学特征的研究

利用偏光显微镜、电子探针仪及X射线粉晶衍射仪,对一种翡翠的仿制品-人造透辉石微晶玻璃的显微结构、析晶特征、化学成分及物相组成进行了研究.该微晶玻璃外观具有明显的放射状晶花,偏光显微镜下观察及BSE图像反映出透辉石微晶玻璃具有显微斑状结构,且含特征的骸晶.电子探针测试得到该材料内玻璃质基质、主晶相透辉石及少量石英的化学成分,其中透辉石内的镍含量明显高于天然翡翠.X射线粉晶衍射分析确定其主要物相为透辉石和玻璃质,与天然翡翠以硬玉、纳铬辉石等为主要矿物组成不同.     

YVO4∶Eu3+纳米荧光粉的水热法合成及其光致发光性能的研究

以NaVO3,Y2O3,Eu2O3为原料,采用水热法在不同pH值(pH =6.5,8.2,10.1,13)条件下合成了具有不同形貌与颗粒尺寸的YVO4∶ Eu3+纳米荧光粉.利用XRD,TEM和荧光光谱仪对样品的结构、形貌和光致发光性能进行了研究.实验结果表明:所合成样品均为具有四方锆石结构的YVO4∶Eu3+纳米晶,溶液pH值对所合成样品的形貌与颗粒大小均有明显影响,而且光致发光性能与样品的形貌有关,YVO4∶Eu3棒状纳米荧光粉因具有较高结晶度而具有较高的荧光强度.     

海胆状Eu2O3/Ag3VO4复合材料的水热合成及其光致发光性能

以硝酸银和氧化铕为金属源,P123为结构导向剂,乙醇和水为溶剂.本文通过前驱体合成路线,采用水热法得到海胆状Eu2 O3/Ag3 VO4微球,并探讨其合成条件;采用SEM、XRD、XPS等方法对样品进行了表征,并探讨了Eu2 O3/Ag3 VO4海胆状微纳米结构的形成过程.测试结果表明:在反应温度为80℃,反应时间为10 h时,所合成的海胆状Eu2 O3/Ag3 VO4微球直径约为4~5μm.针对合成的样品,研究了海胆状Eu2 O3/Ag3 VO4微球的光致发光性能,并考察Eu3+掺杂量对光致发光性能的影响,当Eu3+掺杂量为4;时,样品具有最好的光致发光性能.     

锂皂石的水热合成与表征

采用水热法,以LiOH-MgCl2-SiO2-H2O为反应体系,合成了系列锂皂石(Hectorite)样品.以XRD和FT-IR分析研究了系列锂皂石合成样品的结晶度和谱学特征,探讨了原料配比、晶化温度和晶化时间对合成产物结晶度的影响.结果表明,所设定的反应体系在温度为120℃、时间为12 h水热条件下即可形成锂皂石;在12～72 h和120～200℃合成条件下,随反应时间和反应温度的增加,样品的结晶度逐渐提高.     

尿素共沉淀法制备LiNi0.8Co0.2O2正极材料及其电化学性能

采用尿素共沉淀法合成了LiNi0.8Co0.2O2锂离子电池正极材料,研究了烧结温度、锂源摩尔配比对LiNi08Co02O2晶形结构、形貌以及电化学性能的影响.结果表明,尿素共沉淀法合成LiNi0.8Co02O2样品最佳工艺条件是800℃温度条件下烧结10 h、锂过量5;合成的样品具有较好的电化学性能,以0.2C倍率充放电时首次充放电容量分别为206.4 mAh·g-1和191.6 mAh·g-1,循环30次后容量为178.2 mAh·g-1.     

光致发光在钻石检测中的应用

采用光致发光系统,在297 K及80 K温度下,应用氩离子激光器(波长为488 nm和514 nm)对合成钻石、HPHT处理钻石、辐照处理钻石和天然钻石进行了测试.结果表明:在80 K低温下的测试结果要远比常温297 K温度下好,可能出现由更多的缺陷产生的吸收峰.通常情况下,对于钻石样品514 nm光源激发,可以得到较多较明显的峰,而在488 nm光源激发时,可以产生503 nm和598 nm处的峰.CVD合成钻石、HPHT处理钻石、辐照处理钻石样品在低温80 K、514 nm激发时,均会出现较为明显的575 nm、637 nm峰,而天然钻石则不会出现或仅有微弱显现及偏移,两者区别明显,可以作为鉴定依据.辐照改色的钻石样品中可见到588 nm、680 nm特征峰,而天然钻石、CVD合成钻石及HPHT处理钻石中均未出现此峰,也可作为鉴定辐照改色钻石的依据.     

水热法制备不同粒度GdVO4∶Eu3+纳米荧光粉及发光性能研究

采用水热法在不同pH条件下制备出不同晶粒度GdVO4∶ Eu3+荧光粉.利用X射线衍射、扫描电镜和荧光光谱对GdVO4∶ Eu3+的结构、形貌和发光性能进行了研究.讨论了溶液的pH对晶粒尺寸的影响.结果表明:合成的样品均为单一的GdVO4四方晶相,纳米晶的一次性平均粒径分布在19～41 nm.反应溶液pH为6时,合成样品平均晶粒尺寸最小.激发带主要来自于V-O的电荷迁移带,发射光谱的主发射峰来自于5D0→7F2电偶极跃迁,不同pH值条件下制备的样品的电荷迁移带、发光强度、发射峰相对强度有所不同.     

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。     

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.     

X-ray analysis of sideroxol from <Emphasis Type="Italic">Sideritis leptoclada</Emphasis>

Sideroxol (1), a kaurane diterpene which has the ent-7α,18-dihydroxy-15β,16β-epoxykaurane structure (MW = 320.47, C₂₀H₃₂O₃) was obtained from the acetone extract of Sideritis leptoclada plant as well as from some other Sideritis species. It crystallizes in the orthorhombic space group P2₁, 2₁, 2₁ with a = 10.967(3), b = 24.555(5), c = 6.372(4) Å, Dc = 1.240 g cm⁻³, Z = 4, and refines to R = 0.065 for 721 independent reflections. The skeleton consists of three fused six-membered rings and a five-membered ring with fused epoxide. The six membered rings exhibited slightly distorted chair conformation. In addition to sideroxol, two kaurane and five kaurene diterpenes were isolated from the hexane and acetone extracts of the studied plant.     

New zeotype borophosphates with chiral tetrahedral topology: (H)0.5M1.25(H2O)1.5[BP2O8]·H2O (M = Co(II) and Mn(II))

Two new isostructural open‐framework zeotype transition metal borophosphate compounds, (H)_0.5M_1.25(H₂O)_1.5[BP₂O₈]·H₂O (M = Co(II) and Mn(II)) were synthesized by mild hydrothermal method. The structure of compounds were characterized by single‐crystal X‐ray diffraction which have ordered, alternating, vertex‐sharing BO₄, PO₄, and (MO₄)OM(H₂O)₂ groups with hexagonal, P 6₁ 2 2 (No 178) space group and unit cell parameters for Co a = 9.4960(6) Å, c = 15.6230(13) Å, for Mn a = 9.6547(12) Å, c = 15.791(3) Å, Z = 1 for both of them. TGA/DTA analysis, IR spectroscopy were used for characterization. Magnetic susceptibility measurements for both of the compound indicate strong antiferromagnetic interaction between metal centers. (© 2005 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Photoluminescence characteristics of Mg- and Si-doped GaN thin films grown by MOCVD technique

We have studied the optical, structural and surface morphology of doped and undoped GaN thin films. The p- and n-type thin films have been successfully prepared by low-pressure MOCVD technique by doping with Mg and Si, respectively. The different carrier concentrations were obtained in the GaN thin films by varying dopant concentrations. Photoluminescence (PL) studies were carried to find the defect levels in the doped and undoped GaN thin films at low temperature. In the undoped GaN thin films, a low intensity and broad yellow band peak was observed. The donor–acceptor pair (DAP) emission and its phonon replicas were observed in both the Si or Mg lightly doped GaN thin films. The dominance of the blue and the yellow emissions increased in the PL spectra, as the carrier concentration was increased. The XRD and SEM analyses were employed to study the structural and surface morphology of the films, respectively. Both the doped and the undoped films exhibited hexagonal structure and polycrystalline nature. Mg-doped GaN thin films showed columnar structure whereas Si-doped films exhibited spherical shape grains.     

Solubility of Ag2O into the Na2O–B2O3–Al2O3 system

The solubility of Ag₂O was measured for the Na₂O–B₂O₃ and Na₂O–B₂O₃–Al₂O₃ system with the rotating crucible method and static method, respectively, under air atmosphere at temperatures ranging from 1273 to 1423 K. The contamination of melts from crucibles could be avoided by the rotating crucible method, with which it became possible to measure the solubility of Ag₂O for the Na₂O–B₂O₃ system above the melting point of Ag for the first time. It was found that the addition of Na₂O decreases the solubility of Ag₂O while the addition of Al₂O₃ had little effect on the solubility. The effect of Na₂O and Al₂O₃ on the solubility of Ag₂O is expressed by interaction coefficients and is analyzed in terms of the basicity of melts. The solubility of Ag₂O in Na₂O–B₂O₃–Al₂O₃ melts increased with increased temperature. This phenomena was explained by a small enthalpy change in oxidation of silver.