Substituent Effect on Infrared Spectra and Thermodynamic Properties of Polynitroamino Substituted Cyclopentane and Cyclohexane

运用密度泛函理论方法计算并研究了多硝基氮杂取代环戊烷和环己烷中的取代基效应. 基于B3LYP/6-31G**水平优化的分子结构,通过简谐振动分析,求得两类单环硝胺的红外光谱并作归属,发现理论计算值与已有实验值吻合较好. 基于统计热力学原理,求得它们的热力学性质,探讨了热力学性质与温度和取代基数目之间的关系. 结果表明,热力学性质与温度变化和取代基数目之间均很好地线性相关,同时取代基数目对热力学性质的变化具有基团加和性     

给体位置和数目对四苯基乙烯衍生物双光子吸收性质的影响

在杂化密度泛函水平上,利用响应函数方法,计算了一类四苯基乙烯衍生物的双光子吸收性质.考虑了四苯基乙烯上给电子基团的位置和数目对双光子吸收性质的影响.并且,根据实验者采用的分子,通过增加分子的平面性和共轭长度,以及增强给体强度,理论设计了三种分子结构,并计算了它们的双光子吸收性质.结果表明,给体位置和数目对双光子吸收性质有重要影响.位于分子末端的给体取代基能有效提高双光子吸收强度.随着给体数目的增加,双光子吸收波长发生红移.在四苯基乙烯的不同侧位上添加给体取代基对双光子吸收性质的影响有明显差异.与实验者采用的分子相比,理论设计的分子结构双光子吸收截面均明显增大.当三苯胺基代替四苯基乙烯基之后,双光子吸收峰发生较大红移,双光子吸收截面明显增大.     

磷钼酸作为光催化还原剂制备纳米金溶胶

选择二甲基甲酰(DMF)为电子牺牲剂,以磷钼杂多酸作为光催化还原剂制备了纳米金溶胶,由于DMF与磷钼杂多阴离子间的电荷转移作用,导致钼系杂多酸可成为制备纳米金溶胶的光催化还原剂.实验结果表明,紫外光照作用及光照时间、DMF用量等是影响纳米金的形成和形貌的主要因素,选择适宜的合成条件可以得到粒径均匀、分散性好的纳米金溶胶.     

活性炭负载硅钼钒杂多酸催化苯羟基化反应

以活性炭为载体,采用回流吸附法制备了负载型硅钼钒杂多酸催化剂,以冰醋酸作溶剂,过氧化氢作氧化剂,研究了由苯直接羟基化制苯酚的催化活性。结果表明,苯为2mL,冰醋酸为15mL,过氧化氢为5mL,当负载型杂多酸的用量为0.2g、反应温度70℃、反应时间60m in时,硅钼钒催化合成苯酚的收率可达7.4%,选择性达97.1%。     

钼、钒的单一及混合溶液中离子存在形态的拉曼光谱研究

利用拉曼光谱研究了钼、钒单一及混合溶液在pH=10.0~1.0时的离子分布行为. 钼、钒离子在存在形式上存在着差异：当pH=9.0~7.5时钒主要以(VO₃)_n^n-形式存在,而钼主要为MoO₄^2-. 这一差异是目前现有的许多钼钒分离方法的基本原理. 通过将混合溶液体系的拉曼光谱与单一体系进行对比,分析得出了混合体系中离子的存在形式. 当pH低于6.5时,部分V-O-V基团中的V原子会被Mo原子取代,从而形成了钼钒杂多酸离子. 当pH=6.0~2.0时,钒主要以十聚钒酸盐形式存在;当pH=2.0~1.0时,混合溶液中的钼主要以具有七钼酸盐结构的杂多酸离子存在,而在相同pH的单一溶液中,钼的存在形式主要为Mo₈O₂₆^4-和Mo₃₆O₁₁₂^8-.     

锰卟啉/钒取代杂多酸配合物的合成、表征和性能研究

利用碘化四对(4-三甲氨基苯基)锰卟啉与钒取代杂多酸H5 PMo10 V2O40,在水溶液中,室温下反应合成了锰卟啉/钒取代杂多酸配合物,用红外和紫外光谱技术对其结构进行了表征,发现该配合物中包含着金属卟啉的环状结构与杂多酸的笼状结构,并且二者以化学键的形式键合在一起.以该化合物作为催化剂,以过氧化氢水溶液为氧化剂,在温和的条件下研究了锰卟啉/钒杂多酸配合物对苯的羟基化反应的影响,考察了催化剂的催化活性,探讨了催化剂对苯羟基化反应的活性中心.研究结果表明,杂多酸中的钒原子是其主要的催化活性中心,锰卟啉的存在可以有效地提高其催化活性.     

W掺杂ZnO电子结构与光学性质第一性原理计算

采用了基于密度泛函理论(DFT)的第一性原理平面波超软赝势方法,计算本征ZnO和不同W掺杂浓度下W:ZnO体系的电子结构和光学性质.计算结果表明:W掺杂可以提高ZnO的载流子浓度,从而改善ZnO的导电性.掺杂后,吸收光谱发生红移现象,且光学性质变化集中在低能量区,而高能量区的光学性质没有太大变化,计算结果与相关实验结果相符合.最后,结合电子结构定性分析了光学性质的变化.     

杂多阴离子的NMR和ESR研究：Ⅱ磷钼钒杂多酸及其镧盐的NMR

具有Keggin结构的磷钼钒杂多酸及其盐是有效的氧化剂.本文通过磷钼钒杂多酸及其镧盐的~(31)p,~(51)V,~(139)La,~(17)O及~1H的NMR测定,并结合红外和差热分析,说明镧的引入对Keggin结构没有影响,但镧对水分子有强的作用力,使阴离子之间存在更多的水分子,从而对催化氧化活性产生了影响.     

激光拉曼光谱对LiFePO4/C正极材料包覆碳结构的研究

利用激光拉曼光谱对LiFePO4/C锂离子正极材料碳外壳的石墨化程度进行了研究,对不同碳源合成的样品进行激光拉曼光谱比较,并结合X射线衍射、扫描电镜、透射电镜、选区电子衍射、电阻率测试等多种检测手段,对材料的性质结构和形貌进行了研究.结果发现,相比对应sp3杂化峰和sp2杂化峰的峰面积比,对应非等向性sp2杂化峰和对应规则sp2杂化峰的ID/IG分布更加均匀,其显示的石墨化程度与材料导电性在一定程度上有相似规律,但同一材料的拉曼光谱信号因受碳包覆均匀性的影响出现较大差别,且相对于单独用柠檬酸或蔗糖做碳源的样品,利用两者混合物做碳源的样品的ID/IC值和sp3杂化峰和sp2杂化峰的峰面积比值均较高.在扫描电镜和透射电镜图中,可以观察到二次和一次颗粒包覆不均匀的现象,这有可能是导致同个样品中不同点数据不均匀的原因.但是较大的离散性还是影响了拉曼光谱在此类检测中的客观准确性.     

p型Na掺杂各向异性ZnO的电子性质与热电输运性质

采用密度泛函理论的第一性原理计算研究了p型Na掺杂各向异性ZnO的能带结构、光学性质、介电性质、总态密度和不同原子的分态密度,并系统分析了其热电输运性质。计算分析结果表明,p型Na掺杂ZnO为p型直接带隙半导体,其带隙增大到1.3eV,其对于光子的吸收限向低能量光子移动,体系费米能级附近的态密度大幅度提高,这主要是p态电子贡献的;在费米能级附近的导带和价带中都出现了新的能级,这些新的能级主要由Nas、Nap、Znp、Znd和Op电子形成,且他们之间存在着强耦合相互作用。Na掺杂ZnO的电输运性质具有各向异性;其价带和导带中的载流子有效质量均较大;载流子输运主要由Nas、Nap、Znp和Op电子完成。     

Se替代Te对BiCuTeO电热输运性能的影响

层状氧硫族化合物由于其本征的低晶格热导率和可观的热电性能吸引了广泛关注,其中以BiCuSeO化合物的热电性能最为优异.但是,其同晶型化合物BiCuTeO,由于带隙较小且存在大量本征Cu空位,导致载流子浓度较高,热电性能较差,从而研究较少.针对BiCuTeO存在的上述问题,本文利用Se替代部分Te,以期能够展宽带隙并减少Cu空位,提高其热电性能.采用固相反应结合快速热压烧结制备了BiCuTe_(1-x)Se_xO(x=0, 0.1, 0.2, 0.3和0.4)块体热电材料,并系统地研究了该体系的电热输运性能.研究结果表明,利用Se替代Te,可以使BiCuTeO导电层化学键强度增加、带隙增大、载流子有效质量增加以及载流子散射增强,从而导致载流子浓度和迁移率同时降低,进而电导率随着Se含量增加而剧烈降低, Seebeck系数则显著增大.由于综合电输运性能恶化,功率因子随着Se含量增加而减小,导致热电优值zT随着Se含量增加而降低.最终,Se含量为x=0.1的样品,在室温和723 K时的zT值分别达到约0.3和0.7,仍然在较宽温区内保持较高的zT值.由于Se替代Te改变了BiCuTeO的能带结构,通过载流子浓度优化,有望进一步提高其热电性能.     

非等电子Sb替换Cu和Te后黄铜矿结构半导体Cu_3Ga_5Te_9的热电性能

热电材料是一类能够实现热与电相互转换的功能材料,在制冷和发电领域极具应用潜力.本文采用金属Sb元素非等电子替换Cu3Ga5Te9化学式中的Cu和Te,观察到材料Seebeck系数和电导率提升的现象.这些电学性能的改善与载流子浓度和有效质量的增大及迁移率基本维持不变有关.载流子浓度的提高是由于Sb原子占位在Te晶格位置后费米能级进入到价带所产生的空穴掺杂效应所致,同时也与Cu含量减少后铜空位(V-1Cu)浓度增大相关联.另外,非等电子替换后,阴离子(Te2-)移位导致了晶格结构缺陷参数u和η的改变,其改变量fiu和fiη与材料晶格热导率(κL)的变化密切相关.在766 K时,适量的Sb替换量使材料的最大热电优值(ZT)达到0.6,比Cu3Ga5Te9提高了近25%.因此,通过选择替换元素、被替换元素及替换量有效地调控了材料的电学及热学性能,在黄铜矿结构半导体中实现了非等电子元素替换改善热电性能的思想.     

磷化铟(InP)在太赫兹波段的特性研究

太赫兹(THz)时域光谱(TDS)技术,能同时测量幅值和相位信息,因而能检测到物质丰富的物理化学性质,已逐渐成为科学界一大热点。磷化铟(InP)因其载流子寿命短、质量小等优良性能,正逐渐成为产生和检测THz波辐射的首选光电导材料之一。文章利用THz-TDS测试技术,在室温氮气环境中,对n型0.35 Ω·cm的InP材料在0.2～4 THz波段的特性进行了研究。文章根据物理传输模型,利用更准确的迭代方式,选用新的初始值,更快更准确的得到了复折射率,介电常数,电导率等THz光学常数,并且用Drude模型进行了理论上的模拟计算,所得结果与实验吻合很好,最后还得到了载流子的寿命、迁移率和浓度等THz重要参数。     

Characterisation of molybdenum intermediate layers in Cu-C system with SIMS method

In the design of new high-speed chip generations a huge problem is bleeding off process heat during their operation. The installation of heat sinks onto such chips is necessary. Possible materials are copper-coated carbon composites. They combine high thermal conductivity with low density and a tailorable coefficient of thermal expansion (CTE). The low wettability of copper onto carbon necessitates a surface pretreatment.Flat slices of nitrogen-plasma etched vitreous carbon (Sigradur G) made up as a model system for carbon fiber material. The later serial fabrication of these fibers includes a hot pressing step after the deposition joining them to solid composites. It is simulated by a heat treatment step of the compound. The first sample series consisted of samples with 100 nm molybdenum and 500 nm copper layers (sputter deposited), as deposited and heat treated. The second run concludes samples without molybdenum layer but an additional 50 nm cap layer deposited after heat treatment.All samples were investigated with secondary ion mass spectrometry (SIMS), showing a diffusion of carbon into the molybdenum layer. Measuring MCs⁺ secondary ions, both matrix elements and trace elements were detectable sufficiently.     

镧系元素双1：11系列杂多蓝的红外光谱和紫外光谱研究

本文首次系统研究了镧系元素钼采双１：１１系列两子杂多蓝ＫｚＨｙ（Ｌｎ（ＸＭｏ１１Ｏ３９０２）．ｎＨ２Ｏ（Ｘ＝Ｐ，Ｌｎ＝Ｌａ，Ｃｅ，Ｐｒ，Ｎｄ，Ｓｍ，Ｇｄ；Ｘ＝Ｓｉ，Ｌｎ＝Ｃｅ，Ｐｒ，Ｓｍ，Ｔｂ，Ｄｙ）的红外光谱和紫外光谱，对特征峰进行指认，并与还原前的杂多酸盐进行比较，发现有的特征峰出现小的位移，有的峰强度稍有变化，所以得出结论，还原前后，杂多阴离子结构基本不变，但有轻微的畸变。     

Solid vitreous electrolytes based on the system Li2O-Li2SO4-B2O3-MoO3 for rechargeable lithium power sources

In the given work with the purpose of improvement of moistening ability of sulfoborate solid vitreous electrolyte (SVE) in their structure entered molybdenum oxide (VI). Reduction of wetting angle, i.e. improvement of electrode wetting by a SVE-melt, accompanied by better electrode (aluminium) /SVE interface contact formation. Accordingly, the interface impedance is reduced. As a result of the carried out experiments is established, that the modifying SVE by molybdenum oxide (VI) renders complex positive influence on its physical-chemical properties, namely: improves X-ray-amorphism, raises ionic conductivity, reduces electronic conductivity and effective energy of ion conductivity activation. At comparison of properties modified SVE and "LiPON", it is visible, that the ratio between ionic and electronic conductivity for modified SVE approximately on the order is higher, than for "LiPON". Ionic conductivity of the modified SVE higher than conductivity of "LiPON". The low value of electronic conductivity investigated SVE on a background ionic is the positive factor from the point of view of their use in lithium power sources. Paper presented at the Patras Conference on Solid State Ionics — Transport Properties, Patras, Greece, Sept. 14 – 18, 2004.     

Evaluation of Thermoelectric Properties of Ag0.366Sb0.558Te

Ternary AgSbTe₂ materials are frequently reported to show a promising thermoelectric performance, due to the intrinsically low lattice thermal conductivity and complex valence band structure. However, stoichiometric AgSbTe₂ is found to be thermodynamically unstable and would partially decompose into Ag₂Te and Sb₂Te₃ during thermal cycling. Instead, Ag_0.366Sb_0.558Te is the composition for stabilizing the single-phase according to the Ag₂Te-Sb₂Te₃ phase diagram, while the thermoelectric transport properties have rarely been reported and are the focus of this work. Sn/Sb substitution is found to effectively increase not only the carrier concentration from ≈5 × 10¹⁹ cm⁻³ to ≈4 × 10²¹ cm⁻³, but also the density-of-states effective mass, leading to an enhanced Seebeck coefficient along with a decreased carrier mobility. Single parabolic band (SPB) model with acoustic phonon scattering enables a good understanding on the charge transport. The increased carrier concentration effectively suppresses the bipolar effect at high temperatures. As a result, a peak zT of ≈1.3 and an average of ≈0.9 are achieved.     

微波低温制备Mg2Si0.4Sn0.6-yBiy热电材料的传输机理

德拜弛豫理论表明, 在频率为2.45 GHz的外加交变电磁场的作用下, 微波对极性分子的极化过程约为10^-10 s, 因此利用微波固相反应可以在短时低温条件下制备出纳米粉体材料. 本文以MgH₂代替Mg粉, 利用微波固相反应在低温下制备了Mg₂Si_0.4Sn_0.6-yBi_y (0 ≤y ≤q 0.03)固溶体, 并结合单带抛物线计算模型对其热电传输机理进行了分析. 研究结果表明: 利用该工艺可以有效抑制Mg的挥发和MgO 的生成, 在400 ℃保温15 min内即可完成MgH₂与Si粉和Sn粉的固相反应, 获得片层间距为100 nm的超细化学计量比产物; 杂质Bi的引入可以有效增加载流子浓度, 并引起晶格畸变, 在晶格畸变和样品特有的纳米片层结构的协同作用下, 声子得到有效散射, 样品具有最低的热导率1.36 W·m^-1·K^-1. 较低的有效掺杂率和复杂的能带结构具有降低能带态密度有效质量和减小载流子弛豫时间的双刃效应, 使得本征激发提前, 在600 K样品取得最大ZT值为0.66.     

Energy band and charge-carrier engineering in skutterudite thermoelectric materials

The binary CoSb₃ skutterudite thermoelectric material has high thermal conductivity due to the covalent bond between Co and Sb, and the thermoelectric figure of merit, ZT, is very low. The thermal conductivity of CoSb₃ materials can be significantly reduced through phonon engineering, such as low-dimensional structure, the introduction of nano second phases, nanointerfaces or nanopores, which greatly improves their ZT values. The phonon engineering can optimize significantly the thermal transport properties of CoSb₃-based materials. However, the improvement of the electronic transport properties is not obvious, or even worse. Energy band and charge-carrier engineering can significantly improve the electronic transport properties of CoSb₃-based materials while optimizing the thermal transport properties. Therefore, the decoupling of thermal and electronic transport properties of CoSb₃-based materials can be realized by energy band and charge-carrier engineering. This review summarizes some methods of optimizing synergistically the electronic and thermal transport properties of CoSb₃ materials through the energy band and charge-carrier engineering strategies. Energy band engineering strategies include band convergence or resonant energy levels caused by doping/filling. The charge-carrier engineering strategy includes the optimization of carrier concentration and mobility caused by doping/filling, forming modulation doped structures or introducing nano second phase. These strategies are effective means to improve performance of thermoelectric materials and provide new research ideas of development of high-efficiency thermoelectric materials.     

钨钼杂多化合物及其用途

简要介绍了钨、钼的性质和用途,主要综述了钨钼杂多化合物的合成方法、结构、性质,及其在催化、水质缓蚀剂、分析检测、生物医学、无机离子交换剂等方面的应用。