不同晶型TiO2的制备与光催化性能研究

采用溶胶凝胶法,利用不同温度热处理制备了不同晶体结构的TiO2纳米晶.利用XRD、SEM、EDS、XPS等分析方法对样品的晶体结构、形貌、化学元素组成以及价态进行了表征.结果表明400 ℃、500 ℃热处理TiO2为锐钛矿晶型,600 ℃ 热处理为锐钛矿金红石混合晶型,700 ℃热处理为金红石晶型,单颗粒子呈现类似球形形貌.以罗丹明B为目标污染物,测试了样品的光催化性能,结果表明400 ℃热处理TiO2具有最高的光催化活性,3 h后对罗丹明B的降解率达到94.6;,其反应速率常数达到0.969 h-1.     

退火温度对镶嵌于SiO2膜中的Ge纳米晶结构的影响

采用磁控溅射及退火的方法制备了含Ge纳米晶的SiO2复合膜,应用拉曼散射和X射线衍射技术研究不同退火温度下的Ge纳米晶结构.结果表明:Ge纳米晶的结晶温度约为750 ℃.运用声子限域模型(RWL model)对样品的拉曼散射光谱进行拟合,确定出样品中Ge纳米晶的尺寸.通过XRD谱计算复合膜的内部压应力,得出由其引起的拉曼峰位的蓝移量,得出结论:压应力是造成拉曼模拟曲线与实验曲线峰位偏离的主要原因.     

合成GaP纳米晶过程的关键影响因素

本文系统研究了在有机溶剂中常压合成GaP纳米晶过程中反应温度、反应时间、反应体系的均匀性和原料的比例等关键影响因素.GaP纳米晶的产率、形貌以及平均粒度随着这些关键因素的改变有很大的不同.制备的GaP纳米晶用X射线衍射仪和透射电镜进行了表征.发现了最优化的合成工艺条件,实现了GaP纳米晶的高产率(达85;)制备,而且形貌和粒度可以根据需要进行调控.     

基于电沉积技术的纳米晶材料晶粒细化工艺研究

纳米晶材料电沉积工艺是在传统电沉积工艺的基础上,通过控制适当的工艺条件,最终获得具有各种性能的纳米晶电沉积层的过程.研究表明,由电沉积工艺制备的纳米晶材料,晶粒细小且组织均匀,具有耐磨、耐蚀、耐高温氧化等特殊性能.本文分析了在电沉积过程中纳米晶形成的机理,探讨了工艺参数、复合电沉积和脉冲电沉积、有机添加剂以及采用其它工艺措施对晶粒细化过程的影响.介绍了电沉积纳米晶材料的各种性能及应用.     

Co包覆Al2O3/TiC复合材料的烧结及性能

采用Co包覆Al2O3/TiC微米级、纳米级粉料进行了不同Co含量、不同烧结温度的热压烧结实验.综合分析和对比了两种不同粒径包覆粉体的烧结结果,结果发现纳米级的粉体烧结效果优于微米级粉体的烧结效果.综合力学性能最佳的纳米级复相陶瓷材料的硬度为HRA92.7,抗弯强度σf为782 Mpa,断裂韧性KIC为7.81 Mpa·M1/2.利用SEM观察采取综合力学性能最佳的ATC纳米复合材料制备工艺制备的Al2O3、Al2O3/TiC和ATC的断口,可以看出Al2O3、Al2O3/TiC主要以沿晶断裂为主,而ATC为沿晶与穿晶混合断口,并从ATC断口,发现形成了晶内型结构,观察到了裂纹曲折的扩展路径以及裂纹的分叉、偏转、桥联这些有助于材料强度和韧性提高的现象.     

Cu2ZnSnS4纳米晶的溶剂热法制备和表征

利用溶剂热制备了Cu2ZnSnS4 (CZTS)球形纳米晶.采用X射线衍射(XRD)、拉曼光谱、扫描电子显微镜(SEM)、高分辨透射电子显微镜(HRTEM)、能量色散谱(EDS)和紫外-可见分光光度计对产物的物相结构、形貌、化学组分及光学性能进行表征.结果表明:所制备的CZTS球形纳米晶具有锌黄锡矿结构,球形颗粒的直径为190～300 nm,每个球形颗粒是由很多平均尺寸大约24 nm的纳米晶构成.纳米晶具有锌黄锡矿结构,其禁带宽度约为1.55 eV.同时研究了反应前驱溶液中不同量的硫脲和氯化锌对所制备的CZTS纳米颗粒的结构、原子组分比和形貌的影响规律,并对其形成机理进行了初步探讨.     

微波熔盐沉积制备AlN纳米晶及光致发光特性研究

以高纯AlCl3和Li3N为反应原料,NaCl和KCl为混合熔盐,使用微波熔盐沉积法在700℃制备出A1N纳米晶.利用XRD、SEM、EDS等对纳米晶的物相、形貌进行了定性和定量表征,并使用PL测试了材料的光学性质,分析了主要缺陷类型.XRD测试结果表明,实验获得产物为六方纤锌矿结构的AlN.使用Scherrer公式估算了AlN 产物的晶粒平均粒度大小约为35.6 nm,表明所得确为AlN纳米晶.SEM观测到的纳米晶形貌为方形,分布均匀且晶粒形状几近,平均粒度约为35 nm.EDS测试结果显示AlN纳米晶中Al和N的原子相对百分含量为50.521;和49.479;,其化学配比几近于1∶1物质的量比.室温PL测试发现发光中心在435 nm,缺陷主要是杂质缺陷类型.以上结果充分表明微波熔盐沉积法是一种制备AlN纳米晶的有效方式.     

晶种法制备高长径比纳米银线的研究

利用AgNO3和NaCl反应生成的AgCl颗粒作为晶种合成纳米银线.详细研究了纳米银线在溶液中的生长过程,探讨了AgCl晶种与银源AgNO3物质的量的比和反应时间对纳米银线形貌的影响.通过SEM、TEM、XRD、紫外可见光光谱等测试方法,对纳米银线的生长过程和不同条件下制备的纳米银线的微观形貌和晶体结构进行表征.实验表明,纳米银线是在AgCl颗粒表面上定向生长,AgCl与AgNO3物质的量的比和反应时间影响纳米银线的长度和直径大小.当AgCl与AgNO3的物质的量比为1:5,反应时间4 min时,制备的纳米银线平均直径52 nm,长径比超过了1000.     

软模板法制备二氧化钛纳米晶及表征

以钛酸丁酯为原料,正负表面活性剂自组装形成的囊泡为软模板,制备了二氧化钛纳米晶.采用XRD,TEM,TG-DSC,SEM和EDS,XPS等对二氧化钛纳米晶的微观结构进行表征.结果表明:二氧化钛纳米晶在囊泡双层膜内部,双层膜之间和外部均有析出;150℃,450℃,500℃,750℃,830℃焙烧得到锐钛矿相和金红石相二氧化钛纳米晶,并且随温度升高,锐钛矿相二氧化钛含量先增后减,500℃焙烧产物锐钛矿相二氧化钛含量最高,950℃焙烧产物只含有金红石相二氧化钛,二氧化钛纳米粒子呈不规则五边形,尺寸在80～110 nm之间.750℃焙烧产物对活性艳红具有较好的光催化活性.     

温度对钛酸盐纳米管水热转化的TiO_2纳米晶形貌演变的影响机制

钛酸纳米管水热转化是制备晶相组成和形貌可调控TiO2纳米晶的工艺易控及成本低且收率高的途径。本文研究了两种pH值体系中,水热处理温度对钛酸纳米管水热转化的TiO2纳米晶形貌演变的影响。当钛酸悬浮液的pH值为2.0时,钛酸纳米管水热转化为锐钛矿相纳米晶,且随着水热温度的升高,纳米晶的形貌向规则的双锥形演变;对于pH为0.5的强酸性体系,钛酸纳米管水热转化为金红石相纳米棒,并随着水热温度的升高,其形貌向带有两锥形尖端的长方体纳米棒演变。最后,结合TEM和HRTEM分析,探讨了钛酸纳米管向不同晶相组成和形貌的TiO2纳米晶的水热转化及其形貌演变机制。     

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 structures of the cis and trans isomers of a tetrathia[3.3.3.3]cyclophane

Both the cis and trans isomers of 3,11,18,26-tetrathiatricyclo[26.2.2.1^5,9.2^13,16.1^20,24] hexatriaconta-5,7,9,20,22,24-hexene have been prepared and structurally characterized. Each of these centrosymmetric tetrathia dimers includes two cyclohexane rings in chair conformations with either 1,4-cis or 1,4-trans bonding and two meta-substituted benzene rings. The cis isomer packs into the monoclinic space group P2₁/a with a = 10.485(3)Å, b = 10.3956(18)Å, c = 14.1343(10)Å, = 105.200(13)°, Z = 2 and refined to an R factor of 0.046. The trans isomer crystallizes in the monoclinic space group P2₁/c with a = 10.7217(12)Å, b = 5.6797(7)Å, c = 25.415(5)Å, = 96.001(12)°, Z = 2 and refined to an R factor of 0.043. In the cis structure each benzene ring faces a cyclohexane ring while in the trans structure the cyclohexane rings face one another.     

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.     

电沉积法制备ZnO纳米棒阵列及其发光特性

本文以掺F的SnO2导电玻璃为基板,以硝酸锌水溶液为电解液,采用三电极恒电位体系电沉积制备ZnO纳米棒阵列,系统考察了硝酸锌浓度和沉积电位等工艺参数对ZnO纳米棒阵列的微观形貌及其发光性能的影响规律.结果表明,硝酸锌浓度和沉积电位对纳米棒阵列的形貌有显著影响,控制适宜的工艺条件可以制备出直径分布均匀、结晶性好且纯度高的六方纤锌矿ZnO纳米棒阵列.荧光光谱分析表明,电沉积制备出的ZnO纳米棒阵列在385 nm附近有一个强荧光发射峰,且发光性能稳定、对纳米棒阵列微观形貌的细微变化不敏感,使其在发光二极管和激光器等领域具有广阔的应用前景.     

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.