燃烧-色谱法测定催化剂上碳含量标准物质的确定

利用燃烧-色谱法测定催化剂上碳含量采用外标法定量时,需要确定一种标准物作为定量的基础.在自主开发的燃烧-色谱高温定碳仪上,详细研究了草酸、碳酸钙和碱式碳酸镁3种物质的分解温度,根据3种物质的定碳常数测定了同一催化剂上的碳含量,并与化学法的测定结果进行了比较.结果表明,碳酸钙是测定催化剂上碳含量最合适的标准物质.     

伞形花内酯的荧光量子产率与电离常数

研究了伞形花内酯在不同酸度下的荧光光谱,测量了荧光量子产率和电离常数。伞形花内酯有2种荧光型体,分别存在于弱酸性和弱碱性溶液中。在pH 3～6的溶液中,伞形花内酯以中性分子型体存在,最大激发波长λex=325nm,最大发射波长λem=455nm;在pH 9～10.5的溶液中,伞形花内酯主要以阴离子型体存在,λex/λe...     

LiBe+分子基态及其低电子激发态

采用Davidson校正的多参考组态相互作用方法(MRCI+Q)和多参考平均二次耦合团簇方法(MRAQCC)结合基组ROOS-ANO-TZP得到了LiBe+分子基态(x1∑+)以及六个低电子激发态(a3Σ+,b3∏,A1∑+,B1∏,c3∑+,C1∑+)的势能曲线(PECs).计算结果表明:X1∑+,a3∑+,b3∏和...     

有机和生物晶体固态核磁共振参数的准确预测

理论计算有助于复杂的有机和生物系统光谱的鉴定.对于核磁共振光谱,固体结晶中的化学位移和四极耦合常数(QCC)受到邻近的分子和晶格的氢键和范德华作用较大的影响,从而显示出与气态单体分子不同的NMR参数.因此,在固体晶体NMR参数的理论计算中有必要将氢键和范德华作用这两个因素考虑进来.基于周期性方法,本文采用L-Ala-Gly二肽和硝基苯晶体作为模型体系来考察该方法计算NMR参数的精度.研究结果显示周期结构模型能够将分子间的氢键和范德华作用考虑进来,得到的化学位移和QCC值明显优于传统的单分子模型和超分子模型得到的结果,采用该方法计算的结果能够重现NMR实验结果.     

新席夫碱与铜(Ⅱ)、铁(Ⅲ)在溶液中的配位反应研究

以1-(3-吡啶基)-1,3-丁二酮和1,3-二(2-胺基苯氧基)-2-丙醇进行缩合得到席夫碱1,3-二(2-胺基苯氧基)-2-丙醇缩双1-(3-吡啶基)丁烷-1,3-丁二酮(L),并通过单晶X射线衍射解析了Schiff碱配体(L)的结构。进一步将Schiff碱配体L与金属铜髤、铁髥进行配位反应。采用UV-Vis光谱技术,分别测定了铜髤、铁髥配合物的稳定常数。     

"化学反应原理"模块教学中几个问题的探讨

结合"化学反应原理"(选修4)模块的教学实践,对化学平衡常数的量纲、化学反应进行的方向和沉淀的转化等内容,在更高的层面上进行了深入探讨.     

同结构GdIIIMII(M=Cu，Ni，Co，Fe，Mn)配合物磁性理论研究

基于DFT-BS方法,在不同泛函方法和基组下计算[CuIIGdIII{pyCO(OEt)py C(OH)(OEt)py}3]2+及3d-Gd异金属配合物的磁耦合常数,结果表明,PBE0/TZVP(Gd为SARC-DKH-TZVP)水平可用于描述其磁学性质。顺磁中心CuII、GdIII与桥联配位氧原子间存在较强的轨道相互作用,其磁轨道主要由GdIII的4fz3、4fz(x2-y2)轨道、CuII的3dx2-y2轨道和桥联配位原子O的p轨道组成。顺磁中心CuII离子以自旋离域作用为主,GdIII离子以自旋极化作用为主,顺磁中心CuII自旋离域作用对桥联氧原子的影响大于顺磁中心GdIII的自旋极化作用。在同结构3d-Gd配合物中,随着MII离子未成对电子的增加,顺磁中心间自旋密度平方差越大,顺磁中心MII和GdIII之间的反铁磁性贡献越大,其磁耦合常数越小。     

高β相聚偏氟乙烯基复合体系的制备及压电性能

为了提高聚偏氟乙烯(PVDF)的压电性能,需要寻找有效的途径来提高PVDF的电活性相(β相)含量。 通过水热法成功合成了Ag、ZnO以及二者复合(Ag-ZnO)的3种类型纳米粒子,并与PVDF共混形成PVDF复合薄膜。 通过表征PVDF复合材料的形貌,结晶性能和压电性能,可以发现Ag-ZnO复合纳米粒子的协同作用可以有效提高PVDF的结晶性能和压电性能。 此外,通过单轴拉伸可以使得所有PVDF膜的β相含量得到进一步提高,其中拉伸后的PVDF/Ag-ZnO纳米颗粒(P-C)的β相物质的量分数最高,达到70.0％,最佳的压电系数(d₃₃)达到了31.0 pC/N。     

常见客体分子对笼型水合物晶格常数的影响

Natural gas hydrates are considered as ideal alternative energy resources for the future, and the relevant basic and applied research has become more attractive in recent years. The influence of guest molecules on the hydrate crystal lattice parameters is of great significances to the understanding of hydrate structural characteristics, hydrate formation/decomposition mechanisms, and phase stability behaviors. In this study, we test a series of artificial hydrate samples containing different guest molecules (e.g. methane, ethane, propane, iso-butane, carbon dioxide, tetrahydrofuran, methane + 2, 2-dimethylbutane, and methane + methyl cyclohexane) by a low-temperature powder X-ray diffraction (PXRD). Results show that PXRD effectively elucidates structural characteristics of the natural gas hydrate samples, including crystal lattice parameters and structure types. The relationships between guest molecule sizes and crystal lattice parameters reveal that different guest molecules have different controlling behaviors on the hydrate types and crystal lattice constants. First, a positive correlation between the lattice constants and the van der Waals diameters of homologous hydrocarbon gases was observed in the single-guest-component hydrates. Small hydrocarbon homologous gases, such as methane and ethane, tended to form sI hydrates, whereas relatively larger molecules, such as propane and iso-butane, generated sⅡ hydrates. The hydrate crystal lattice constants increased with increasing guest molecule size. The types of hydrates composed of oxygen-containing guest molecules (such as CO₂ and THF) were also controlled by the van der Waals diameters. However, no positive correlation between the lattice constants and the van der Waals diameters of guest molecules in hydrocarbon hydrates was observed for CO₂ hydrate and THF hydrate, probably due to the special interactions between the guest oxygen atoms and hydrate "cages". Furthermore, the influences of the macromolecules and auxiliary small molecules on the lengths of the different crystal axes of the sH hydrates showed inverse trends. Compared to the methane + 2, 2-dimethylbutane hydrate sample, the length of the a-axis direction of the methane + methyl cyclohexane hydrate sample was slightly smaller, whereas the length of the c-axis direction was slightly longer. The crystal a-axis length of the sH hydrate sample formed with nitrogen molecules was slightly longer, whereas the c-axis was shorter than that of the methane + 2, 2-dimethylbutane hydrate sample at the same temperature.     

初应力下压电半导体板中SH波的传播特性

针对无限大n-型压电半导体板,论文理论研究了其在初应力作用下水平剪切波的传播特性。基于压电半导体三维宏观理论和边界条件得到色散关系,结合数值算例,系统分析了边界条件、初始载流子浓度、板的厚度和初应力大小对SH波传播特性的影响。此外,讨论了初应力下两种不同材料中的SH波传播。研究显示：较小的初应力对相速度影响很小可忽略,当初应力达到一定值时波速急剧下降;类似地,初应力足够大时衰减才会逐渐加强。计算结果对压电半导体器件设计具有一定的理论指导意义。