掺铽钼酸镉荧光粉的制备与光谱性质

以Cd(NO3)2·4H2O和Na2MoO4·2H2O为原料,采用沉淀法制备Tb3+离子掺杂的CdMoO4微纳米颗粒.在600℃下,分别对样品保温1h、3h,通过X-射线衍射仪(XRD)、扫描电子显微镜(SEM)、红外光谱(IR)、荧光光谱分析(PL)对样品进行了表征.结果表明,产物为纯白钨矿型纯四方相CdMoO4,在1650 cm-1、1376 cm-1、756 em-1处的特征吸收峰对应于[MoO4]2-四面体中Mo-O键的反对称伸缩振动,在3500～3300 cm-1和430 cm-1处出现明显的红外特征吸收带,可能是CdMoO4:Tb3+吸附水羟基弯曲振动而引起的.在310 nm激发下,CdMoO4:Tb3+,主峰都位于547.5 nm处,484 nm、547.5 nm、611.5 nm分别对应于Tb3+的5D4-7F6、5D4-7F5、5D4-7F3的跃迁.     

锌添加对大尺寸硼掺杂金刚石生长的影响

采用高温高压法在NiMnCo体系下,通过添加低熔点金属锌合成出硼掺杂金刚石晶体.探究锌添加剂对硼掺杂金刚石晶体合成条件、形貌、颜色的影响.实验结果表明在NiMnCo体系中,随着锌添加量增加,硼掺杂金刚石的合成压强和温度明显提高,晶体的颜色逐渐变黑;红外吸收光谱显示,随着锌添加量的增加,氮杂质特征吸收峰1130 cm-1和1344 cm-1逐渐消失,氮杂质含量降低至消失;1290 cm-、2460 cm-1、2800 cm-1硼相关吸收峰增强,即硼杂质的含量逐渐增多.在传统NiMnCo触媒体系下,锌的添加有利于硼原子进入金刚石晶格中去,本工作为合成高质量硼掺杂金刚石提供新的思路.     

镶嵌在SiO2基体中SiC纳米晶的紫外光致发光

将剂量为2×1016 cm-2的C+以60 keV的能量注入到SiO2薄膜中并进行了退火处理.从样品的室温光致发光(PL)光谱中观察到六个PL峰,其峰位分别处于2.601 eV、2.857 eV、3.085 eV、3.249 eV、3.513 eV和3.751 eV.其中3.249 eV处的PL峰与4H-SiC有关.而对于尚未见报道的3.751 eV处PL峰,进行了红外吸收和荧光激发(PLE)测试:在PLE谱4.429 eV处显示出一个对应于3.751 eV处的激发峰.在红外吸收谱上证实0.205 eV(1650cm-1)处的吸收峰与3.751 eV处发光峰的起源相关,从而推断在3.751 eV处的PL峰应起源于氧空位缺陷.     

掺锗CZSi中与锗有关的红外光谱特性

用FTIR法测试了CZ法生长的不同掺Ge浓度单晶的红外吸收光谱,结果发现掺锗浓度≤1;(重量比)低浓度情况下,红外谱图与不掺锗CZSi的红外谱图基本相同.但随着掺入晶体中锗浓度的增加, 红外谱图在710cm-1处出现了一个新的吸收峰.锗浓度越高,此峰越明显.该峰可能是由于Ge-C或Si-Ge-C键合体系的产生而引起的红外吸收峰.     

对比不同离子的掺杂对镍锌铁氧体电磁损耗性能的影响

应用水热法掺杂Co2+、Mn2+和Cu2+到纳米镍锌铁氧体粉末中.并利用XRD、TEM和VNA对其进行表征和分析,研究了掺杂不同金属离子对样品粒度、形貌、电磁损耗性能及吸收性能的影响.结果表明:镍锌钴铁氧体结晶更加完全,晶粒结构更加完整,出现团聚现象,晶粒排列相比其他更加致密.并且晶格常数由0.8352 nm增加到0.8404 nm,改变吸收峰的位置,增加吸收器的带宽,改善材料在低频率区间内的的吸波性能.Mn2+的掺杂相比镍锌钴铁氧体吸波性能下降,吸波效果减弱.Cu2+的掺杂没有影响纳米镍锌铁氧体电磁损耗的吸波频段.     

不同Li/Nb比Mg:In:Fe:LiNbO3晶体的光折变性能研究

采用提拉法生长了不同Li/Nb比(Li/Nb=0.85,0.94,1.05,1.20,1.38)的Mg:In:Fe:LiNbO3(LN)单晶.测试了Mg:In:Fe:LN晶体的红外透射光谱,紫外吸收光谱,抗光致散射能力,响应时间和指数增益系数.实验结果显示:Li/Nb=0.85晶体的OH-吸收峰在3481cm-1附近, Li/Nb=0.94、1.05、1.20的晶体的OH-吸收峰在3505cm-1附近,而Li/Nb=1.38晶体的OH-吸收峰有三个,分别在3466cm-1、3481cm-1和3518cm-1附近.随着Li/Nb比的增大,晶体的紫外吸收边发生紫移,抗光致散射能力增强,响应速度加快,指数增益系数增大.结果表明:Li/Nb=1.38的晶体是性能最为优良的光折变晶体材料.     

氧化锌纳米棒的制备及其光电性能的研究

以硝酸锌Zn(NO3)2·6H2O和六次甲基四胺(HMT)为原料,通过水热法制备出氧化锌纳米棒,研究了反应时间和冷却时间对产物形貌和尺寸的影响.采用扫描电子显微镜(SEM)、X射线衍射(XRD)、光致发光谱(PL)、紫外-可见光谱、红外光谱(FT-IR)表征产物的结构和性能.结果表明,反应时间为6 h和急速冷却至室温条件下合成样品为六方纤锌矿氧化锌纳米棒,平均直径为300 nm;样品具有良好的结晶质量和发光性能,样品在200～400nm有较强的紫外吸收性能;FT-IR图谱表明产物在430 cm-1左右出现了Zn-O特征吸收峰,并有所红移;样品的开启场强为2.2 V/μm,场增强因子为2550,当场强为4.75 V/μm时,电流密度可以达到0.7 mA/cm2,是一种性能优良的冷阴极电子发射源.     

氧对饵掺杂硅纳米晶粒电子结构和光学性质的影响

采用第一性原理,对O与Er共掺杂硅纳米晶粒的电子结构及光学性质进行了计算.计算结果表明:O原子的掺杂没有影响Er掺硅纳米晶粒的禁带宽度;Er掺硅纳米晶粒结构在紫外区的吸收峰因O原子的掺入明显加强,红外区源于Er原子的吸收峰峰值减小.     

稀土掺杂氧化锌纳米粉的制备及其性能研究

本文以Zn(NO3)2和(NH4)2CO3为原料,采用共沉淀法分别制备了La3+和Y3+掺杂的氧化锌纳米粉体,借助于XRD、TEM、荧光光谱仪等测试手段分别对粉体的相组成、形貌及其光致发光性能进行了表征.结果表明:镧掺杂可以促使纳米氧化锌取向连接,而钇掺杂则控制和修饰其沿极性方向的聚集.当钇掺入量由0.2;增至2;原子分数时,引起氧化锌晶体发光强度的改变,且导致粒径减小至10 nm左右,而粒径减小引起的量子尺寸效应使发光峰蓝移.在掺杂量均为1;原子分数的条件下,镧掺杂可以增强纳米氧化锌的黄光发光强度并使其峰位蓝移,钇掺杂则能削弱黄色发光.     

Nd3+:α~NaYF4单晶体的生长与光谱特性

以KF为助熔剂,初始原料按照NaF:KF:YF3:NdF3=30:18:47:5的摩尔比例,采用助熔剂-坩埚下降法成功生长出了优质块体Nd3+掺杂α~NaYF4单晶体.XRD图谱表明,引入少量钕离子没有改变单晶体的立方相结构.测定了钕离子在晶体中的实际掺杂浓度为3.15mol;,相比初始掺杂浓度偏小,说明在单晶体中稀土离子存在着分凝现象.根据吸收图谱,在800nm处具有最强吸收峰,最大吸收系数α和吸收跃迁截面σabs分别为0.91cm-1和0.138×10-20cm2.在800nm激光激发下,发射光谱在800~1500nm范围内有三个峰,由4F3/2能级跃迁到4I11/2能级所产生位于1052nm处的峰值最强,测得荧光寿命为35μs.掺钕氟化钇钠晶体的光学特性表明它在中红外激光领域具有潜在的应用价值.     

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。     

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.     

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.     

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)     

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.     

Selinidin: Crystal structure generated by C–H···O, C–H···π and π-π interactions

The title compound, 9,10-dihydro-8,8-dimethyl-2-oxo-2H,8H-benzo[1,2-b:3,4-b']dipyran-9-yl-2-methyl-2-butenoate, C₁₉H₂₀O₅, was isolated from the roots of Selinum vaginatum. The compound crystallizes into monoclinic space group P2 ₁ with unit cell parameters: a = 12.830(2) Å, b = 9.041(1) Å, c = 14.983(1) Å, β = 95.09(1)°, Z = 4. The crystal structure has been determined using direct methods and refined by full-matrix least-squares to a final R value of 0.0529 for 3142 observed reflections. There are two independent molecules, A and B, per asymmetric unit. In both the molecules, the coumarin nucleus is planar. However pronounced differences are observed in the conformation of dihydropyran ring which has a half-chair conformation with an 8β-9α orientation in molecule A and is intermediate between half-chair and sofa in molecule B. Differences also occur in the conformation of the 2-methylbutenoyloxy side chain at C9 due to the different geometry of C–H···π interactions in molecules A and B. Molecules A and B are connected by π–π interactions between their coumarin fragments forming dimers. The dimers interact through C–H···O and C–H···πhydrogen bonds.     

Chromene and Imidazole Based D-π-A Chemosensor Preparation and Its Anion Responsive Effects

We have designed and synthesized the colorimetric chemosensor through the reactions of 2-(4H-chromen-4-yildene)malonitrile and 4-imidazolecarboxaldehyde. Due to its well conjugated D-π-A system and the existence of NH- fragment in structure, we expected that the chemosensor can detect anion using NH- fragment in the imidazole moiety of the structure. In this regard, UV-Vis absorption spectra were measured to investigate sensing properties of the probe toward different anions in DMSO. This chemosensor can detect both fluoride and cyanide ion with absorption change in intensity. In addition, pH sensing property was also investigated upon the addition of hydroxide ion. These properties are related to the deprotonation effect. The ICT system in this molecule was also observed by the computational approach using Material Studio 4.3 package.     

电子显微分析在表征纳米晶体化学组分中的应用

纳米材料的化学组分及含量影响其光、电、声、热、磁等物理性能,电子显微分析是表征纳米晶体化学组分的重要方法之一.本文综述了X-射线能谱(EDS)、X-射线波谱(WDS)、电子能量损失谱(EELS)和选区电子衍射(SAED)等现代电子显微分析技术在表征纳米晶体化学组分、形貌、尺寸和结构等方面的应用及其研究进展,并比较了这些分析方法存在的差异,提出了其应用中存在的不足及今后的研发方向.     

Considerations on the structure and physical properties of B2O3-SiO2 and GeO2-SiO2 glasses

Data of density, refractive index and thermal expansion coefficient for B₂O₃-SiO₂ and GeO_2-SiO₂ glasses have been analyzed. The volumes of the structural units are the same found for the vitreous B₂O₃, GeO₂ and SiO₂. The volume of any structural unit is constant over the entire composition region of the glass system. The same has been found for the differential refraction and unit refraction of the structural units in these glasses. Different features are observed for the differential expansion of the structural units. There is a considerable change with composition in the differential expansion of BO₃, GeO₄ and SiO₄ units. The effect is attributed to a change in the asymmetry of vibrations with the number of Si-O-B or Si-O-Ge linkages in the matrix. The thermal expansion coefficient is mainly determined by the contribution of B₂O₃ or GeO₂ in the concerned glasses.