水热体系中不同前驱物对合成镁铝水滑石微结构的影响

以不同的镁源、铝源组合为前驱物,利用XRD、SEM及EDS比较研究了水热体系中不同的前驱物组合对合成镁铝水滑石(Mg-Al-LDHs)晶体微结构及晶体生长的影响,同时利用生长基元的配位体理论对其生长机理进行了初步探讨.研究结果表明:当固定体系的pH =12,水热温度120℃、水热时间18h的条件下,不同的前驱物组合均可以合成结晶度较好的镁铝水滑石晶体;但不同的镁源、铝源组合对产物的物相、分散性、结晶规整性、厚径比、纯度、大小及微结构有一定的影响.当镁源固定为MgCl2,铝源分别为Al2O3、Al(NO3)3、AlCl3时,不溶性氧化铝合成的LDHs规整性、分散性及纯度较差,晶体发育不完整;当铝源分别为溶解度较好Al(NO3)3、AlCl3时,合成产物LDHs晶体的结晶度、规整性、分散性及纯度较好,但由于溶解度和相连阴离子极性的不同,造成产物微结构的微小差异;当镁源固定为溶解度较大的Mg(NO3)2时,铝源分别为Al(NO3)3、AlCl3时,同溶解度较小MgCl2相比,更有利于合成结晶度、规整度、尺寸更小的镁铝水滑石晶体.溶解度较大的镁源、铝源前驱物组合合成的镁铝水滑石有更高的结晶度和规整度.EDS分析证实,溶解度较差的Al2O3合成的镁铝水滑石纯度较差.溶解度较好的不同镁源、铝源前驱物组合合成的镁铝水滑石不含有任何其它阴离子杂质,平均镁铝比约为3,非常接近LDHs的理论值.     

Co-MgAl三元类水滑石的合成、微结构及吸附性能研究

采用水热法制备了Co-MgAl三元类水滑石层状化合物(HTLcs),利用X射线衍射(XRD)、扫描电镜(SEM)比较研究了不同Co2+比例条件下对合成产物物相、晶体微结构及晶体生长的影响,同时利用生长基元的配位体理论对其合成机理进行了初步探讨.以甲基橙(MO)模拟染料废水为吸附对象,比较研究了三元类水滑石与二元水滑石焙烧产物的吸附性能和吸附机理.研究结果表明:钴离子同层板二价镁离子存在着交换作用,钴离子掺杂量的不同,没有影响水滑石固有的层板结构,但影响了构建钴镁铝三元类水滑石过程中各晶面的生长.Co∶Mg∶Al为1∶2∶1的HTLcs经过500 ℃焙烧后,焙烧产物(LDO)仍呈现片状结构.但径向尺寸和厚度同焙烧前相比略有减小,产物的均一性、规整性相比焙烧前变差,其对甲基橙模拟染料废水的吸附脱色性能随着时间的增加,呈缓慢增加的趋势,达到吸附平衡需要时间更长为70 min,脱色率仅为60;左右,明显低于二元镁铝水滑石焙烧产物(MgAl-LDO)(90;).吸附动力学研究表明Co-MgAl-LDO焙烧产物对甲基橙的吸附过程更符合准二级动力学方程,吸附等温线符合Freundlich模型,而二元MgAl-LDO对甲基橙的吸附过程较符合准一级动力学方程,吸附等温线符合Langmuir模型.     

微波水热法制备Mg-Al水滑石纳米晶

以MgO和Al(OH)3为起始反应物,用微波水热法在180℃反应30 min,可以制备出平均晶粒度约35 nm的高结晶度单相纳米晶Mg-Al水滑石.用XRD、SEM对合成产物进行了表征.随反应温度升高和时间的延长,合成产物中杂相减少,Mg-Al水滑石晶粒度逐渐增大.在180℃反应仅1 min,即可获得平均晶粒度为约27 nm Mg-AlLDHs,杂相只有微量MgO.微波水热法能够促进起始反应物快速水解,形成Mg-Al LDHs晶核和晶粒长大.     

规整锌铝类水滑石的合成及其结构分析

采用改进的水热法合成了六方状规整的锌铝类水滑石,样品采用XRD、SEM、N2吸附-解吸进行了物相、形貌及比表面分析.结果发现,当在水热反应体系中加入体积分数为25;的乙二醇,反应温度T=180℃,反应时间t=20 h时可获得显著的板层结构、晶形好、分散性好、规整性好、优质的Zn-Al类水滑石,谢乐公式估算粒子粒径约在39.24 nm左右.     

规整Cu-Zn-Mg-Al类水滑石的合成及其结构分析

以CuCl2·2H2O、ZnCl2·6H2O、MgCl2·6H2O、AlCl3·6H2O、Na2CO3为原料,采用丙三醇-水热法组装了优质铜-锌-镁-铝类水滑石.样品采用XRD、SEM、TEM、TG-DAT、N2吸附-解吸的分析方法进行了物相、粒度、晶体形貌结构、热分析和比表面分析.分析了不同介质条件对Cu-Zn-Mg-Al-HTlc类水滑石样品特征的影响.结果发现,在水热反应体系中加入体积分数为15;的丙三醇,反应温度为180 ℃,反应时间为18 h时可获得晶形好、板层结构显著、规整性好、分散性好的优质铜锌铁镁铝水滑石,估算薄层厚度约在36 nm左右.     

在钛酸钠纤维表面吸附生长SnO_2量子点

本文研究了水热条件下SnO_2纳米晶体在钛酸钠纤维表面的吸附生长特性.采用水热法,以钛酸钠晶体纤维和适量的SnCl_4· 5H_2O为前驱物,水热反应条件为pH值11,填充度68;,反应温度120 ℃、150 ℃,反应时间24 h,在钛酸钠纤维表面生长了金红石相SnO_2纳米晶体,晶体尺度约为5 nm.实验结果显示钛酸钠晶体表面具有很强的表面活化能.     

搅拌-超声氧化锆纳米管脱色降解甲基橙的研究

采用阳极氧化法在有机溶液中制备氧化锆纳米管,以搅拌-超声方法研究其对甲基橙的脱色降解性能.实验采用不同pH值的甲基橙溶液,发现氧化锆纳米管对较强酸性的甲基橙溶液有较理想的脱色降解效果.对比氧化锆粉体、纳米管未退火、退火后(600℃)三种材料,退火后的氧化锆纳米管的脱色降解性能整体最佳.XRD测试显示退火后氧化锆纳米管阵列呈现单斜和四方相的混合体.通过FTIR测试脱色降解后的氧化锆纳米管阵列,显示材料中已经不存在甲基橙分子结构,对比研究发现醌式结构和偶氮式两种结构下脱色降解机理相同.     

醇-水体系中pH值和焙烧温度对合成MgO纳米片晶体性质的影响

采用液相法,在醇-水体系中,以Mg(NO3)2·6H2O为镁源、PEG-2000为表面活性剂、NH3·H2O为沉淀剂,研究了pH值和焙烧温度对制备MgO纳米片晶体性质的影响.采用XRD、SEM和BET等手段对MgO纳米片晶相组成、微观形貌、孔结构进行分析表征.研究结果表明,pH值和焙烧温度对MgO纳米片晶相组成没有影响,但对样品微观形貌和比表面积影响较大.较低的pH值和焙烧温度或者较高的pH值和焙烧温度均会导致样品形状不规则,出现不同程度团聚,比表面积较小.在pH=10、焙烧温度500℃条件下制得MgO纳米片形状规整、分散性较好,比表面积、孔容和平均孔径分别为145.42 m2·g-1、0.67 mL·g-1和18.56 nm.     

水热法合成羟基磷灰石的微分析研究

以CaCO3和CaHPO4·2H2O为前驱体,采用水热法制备了羟基磷灰石(HAP)晶体,利用X射线衍射(XRD)、扫描电镜(SEM)及X射线能谱分析仪(EDS)系统研究了pH值、水热温度、反应时间、Ca2+浓度等条件对合成HAP晶体微结构及晶体生长的影响,同时对其生长机理进行了探讨.结果表明:随着水热合成温度的升高、时间的延长、Ca2浓度的增加,晶体发育越完整,HAP晶体的长径比呈增大趋势;体系的pH值对HAP晶体的生长有较大的影响,随着pH值的增加HAP晶粒的大小、长径比减小趋势明显;在水热温度为200℃,pH值=10,时间8h的条件下,可得到结晶度高、晶形完整清晰,端面尺寸在50～ 70 nm,生长极性明显的六方柱状的一维n-HAP晶体.EDS分析结果证实合成的HAP平均钙磷比约为1.70左右,同理论值比较相符.点分析研究表明晶体端面的钙磷比比平均的略高,钙磷比约为1.75,从而证明了Ca2+的浓度直接影响着HAP晶体的极性生长.     

二维晶体Ti3C2的制备及其对有机染料的吸附性能研究

采用49;的氢氟酸刻蚀Ti3AlC2成功制备了层状二维晶体Ti3C2,并研究了其作为吸附剂对有机染料罗丹明B(RhB)、亚甲基橙(MO)和亚甲基蓝(MB)的吸附性能.利用X射线衍射仪(XRD)、扫描电子显微镜(SEM)、气体吸附分析仪、紫外可见分光光度计等对样品物相、晶体结构和孔隙结构及比表面积进行了表征,考察了温度和染料浓度对Ti3C2吸附效果的影响.结果表明,二维晶体Ti3C2对有机染料具有较好的吸附性能,随着温度的升高吸附速率有明显的提高;Ti3C2对RhB和MB的吸附效果随着温度的升高均有明显的提高,但对100 mg/L的MO,在25℃时吸附效果最好.45℃时,Ti3C2对浓度为50 mg/L的染料的吸附速率RhB＞ MB＞ MO.     

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.