V2O5/TiO2催化剂表面钒氧物种的分散状态和催化性能

用X射线衍射(XRD)、激光拉曼光谱(LRS)、程序升温还原(TPR)和微反评价等手段研究了V₂O₅在TiO₂(锐钛)表面的分散状态和负载型V₂O₅/ TiO₂(锐钛)催化剂的邻二甲苯选择氧化催化性能. 结果表明在TiO₂(锐钛)表面V₂O₅分散容量的实测值(1.14 mmol V/100 m² TiO₂)与TiO₂(锐钛) 优先暴露晶面(001)上的空位密度(1.16 mmol/100 m² TiO₂)接近, 这表明分散的钒离子可能键合在TiO₂(锐钛)表面的空位上, 与嵌入模型估算结果相符. 当V₂O₅的负载量远低于其分散容量时, 表面上的钒氧物种主要为孤立的VOx通过V-O-Ti键与载体结合. 随V₂O₅负载量的增加, 孤立的VOx与其最近邻的钒氧物种(可为孤立或聚合)通过V-O-V键结合, 导致V-O-Ti键的比例降低和聚合钒氧物种的比例增多、表面氧物种的反应活性降低. 虽然V₂O₅/TiO₂催化剂的邻二甲苯选择氧化的活性随负载量增加而增加, 到钒氧物种成单层时达极大, 但按每个钒离子估算的TON(转化数)却随负载量的增加而线性下降. 当V₂O₅的负载量高于其分散容量时, 增加的V₂O₅以晶相形式存在, 此时除钒离子的利用率降低外, 还由于晶相V₂O₅中只有V-O-V存在, 与之相结合的氧离子的活性较与V-O-Ti键合的弱, 邻二甲苯选择氧化的活性随负载量的增加有所下降, 而其TON则更为迅速地线性降低.     

有机多羧酸为桥连配体的过渡金属配位聚合物化学

以FeCl₃∙6H₂O, Na₄bta (H₄bta = 1,2,4,5-benzentetracarboxilic acid), 1,10-phen (1,10-phenanthroline)和H₂O为原料, 用水热技术合成出了以均苯四甲酸根为桥连配体的新的二维配位聚合物[Fe(μ₄-bta)_0.5(phen)(OH)]_n (1). 化合物1的晶体属于单斜晶系, P2₁/n空间群, a = 1.0129(2), b = 0.9265(2), c = 1.5696(3) nm, β = 91.37(3)°, V = 1.4721(5) nm³, Z = 3. 一致性因子R₁ = 0.0292, wR₂ = 0.0798. 结构测定结果表明, 化合物中, 每个bta配体连接四个Fe^III单元, 构成新的μ₄-配位模式, bta的四个脱质子的羧基, 交替地以单齿和双齿配位方式与Fe^III离子连接, 构成二维无限层状结构.磁性测试结果表明, 该化合物中存在着反铁磁相互作作用. 热失重谱显示出, 它具有较好的热稳定性. 此外, 还测定了化合物的IR及UV-Vis谱.     

Ionic Liquid Based Electrolyte with Mesoporous Silica SBA-15 as Framework for Quasi-solid-state Dye-sensitized Solar Cells

Quasi-solid-state electrolytes were fabricated with mesoporous silica SBA-15 as a framework material. Ionic conductivity measurements revealed that SBA-15 can enhance the conductivity of the quasi-solid-state electrolyte. The diffusion coefficients of polyiodide ions such as Ⅰ3ˉ and Ⅰ5ˉ which were confirmed by Raman spectroscopic measurement, were about twice larger than that of I-. The optimized photoenergy conversion efficiency of dye-sensitized solar cells （DSSC） with the quasi-solid-state electrolyte was 4.3% under AM 1.5 irradiation at 75 mW·cm^-2 light intensity.     

丙烯酸稀土接枝剑麻纤维及性能研究

为改善剑麻纤维(SF)与聚合物基界面的相容性,制备了丙烯酸稀土接枝剑麻纤维,并对其结构进行表征。用过硫酸铵作为引发剂,把丙烯酸稀土接枝到剑麻纤维表面上。利用红外光谱仪、扫描电子显微镜、X射线粉末衍射仪对接枝剑麻纤维结构进行表征,结果表明丙烯酸稀土已成功接枝到剑麻纤维表面上。考察了接枝剑麻纤维热稳定性和吸油性能,结果表明接枝剑麻纤维的热稳定性、吸油性能优于剑麻纤维,饱和吸油量(24 h)达5.957 g.g-1,吸油倍率达4.727%。     

1H和19F NMR研究镍系催化丁二烯聚合中醇类对BF3·Oet2的增溶作用

The solubility of BF₃OEt₂ in hydrogenated gasoline was improved greatly by means of premixing BF₃OEt₂ with C₃H₁₇OH in nickel catalyst system, so that the effeciency of fluorine in the system was increased markedly. It is confirmed that there was a intermolecular hydrogen bond between alcohol and BF₃OEt₂ molecules by using ¹H NMR, which was a vital factor to lead the solubilization of BF₃OEt₂ in hydrogenated gasoline. Otherwise, the caculation formula of the chemical shift ofproton in hydroxy, ¹H = xipi,was suggested in hydrogen bond system.     

PtSn/Al2O3/MCM-41催化剂的丙烷脱氢催化性能

用微型催化反应装置评价,并结合X射线粉末衍射(XRD)、表面积和孔结构测试、程序升温还原(TPR)、氢化学吸附和热重分析等方法研究了负载型PtSn/γ-Al2O3,PtSn/MCM-41和PtSn/Al2O3/MCM-41催化剂的丙烷脱氢反应催化性能.发现PtSn/Al2O3/MCM-41催化剂具有较PtSn/MCM-41催化剂高的丙烷脱氢反应活性和较PtSn/γ-Al2O3催化剂高的反应稳定性.实验结果表明,纯硅MCM-41载体表面的锡物种因与载体相互作用较弱故易被还原,导致铂金属分散度和催化剂的丙烷脱氢活性较低.用Al2O3修饰MCM-41可以增强Sn物种与Al2O3/MCM-41载体之间的相互作用,提高PtSn/Al2O3/MCM-41催化剂铂金属分散度和丙烷脱氢催化活性.并且,积炭后的PtSn/Al2O3/MCM-41催化剂具有较高的铂金属表面裸露度,故具有较高的丙烷脱氢反应稳定性.PtSn/Al2O3/MCM-41催化剂优良的丙烷脱氢催化性能町能不仅与Sn-载体Al2O3/MCM-41较强的相互作用有关,而且与Al2O3/MCM-41载体的介孔结构有关.     

负载型MoO3 /γ-Al2O3催化剂中晶格氧的丙烷氧化脱氢反应性能

采用X射线衍射(XRD),氢气程序升温还原(H2-TPR)和无氧脉冲反应评价等研究了MoO3在γ-Al2O3载体表面的分散状态和负载型MoO3/γ-Al2O3催化剂晶格氧物种的丙烷氧化脱氢反应性能.结果表明在γ-Al2O3表面MoO3分散容量的实测值(4.73Mo6 /nm2)与按照"嵌入模型"估算的理论分散容量(4.90 Mo6 /nm2)接近.在分散容量以下,键合在γ-Al2O3表面孤立的Mo-O-Al物种倾向于分散在相邻的空位上且通过Mo-O-Mo化学键相连形成聚合的表面MoOx物种.随着MoO3负载量增加,Mo-O-Al键合方式逐步转变为Mo-O-Mo键合方式,钼离子周围的氧离子活泼性下降,导致丙烷氧化脱氢反应活性下降.超过分散容量以上的Mo离子以晶相形式存在.由于钼离子表面利用率下降,尤其是多层的晶相氧化钼表面Mo-O-Mo物种难以与载体表面铝离子键合,导致与钼离子相结合的氧离子可移动性下降、反应活泼性降低,催化剂的丙烷氧化脱氢反应活性急剧下降.     

CT-6B托卡马克的红宝石激光90°汤姆逊散射系统的相对校正

本文阐述了CT-6B托卡马克的红宝石激光90°汤姆逊散射记录系统的光谱响应相对校正和带宽响应相对校正的方法和结果.     

Discontinuous and continuous transitions of collective behaviors in living systems

Living systems are full of astonishing diversity and complexity of life. Despite differences in the length scales and cognitive abilities of these systems, collective motion of large groups of individuals can emerge. It is of great importance to seek for the fundamental principles of collective motion, such as phase transitions and their natures. Via an eigen microstate approach, we have found a discontinuous transition of density and a continuous transition of velocity in the Vicsek models of collective motion, which are identified by the finite-size scaling form of order-parameter. At strong noise, living systems behave like gas. With the decrease of noise, the interactions between the particles of a living system become stronger and make them come closer. The living system experiences then a discontinuous gas-liquid like transition of density. The even stronger interactions at smaller noise make the velocity directions of the particles become ordered and there is a continuous phase transition of collective motion in addition.