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61.
62.
采用DIS数字信息化系统,对不同浓度的蓝墨水溶液在激光光源照射下的透射平均照度及照度分布图像进行实验研究,得到了平均照度值随溶液浓度变化的规律。对不同颜色塑料膜片对白炽灯光源透过照度值及照度分布图像进行实验研究得到及其相关之规律。 相似文献
63.
Intermolecular Stetter reaction of aromatic aldehydes with (E)-(2-nitrovinyl)cyclohexane catalyzed by thiazolium A has been developed. The reaction rate and efficiency are profoundly impacted by the presence of thiourea B. The reaction affords moderate to good yields of the Stetter product. Some factors influencing yield were discussed. 相似文献
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《Comptes Rendus Physique》2015,16(2):193-203
The field of multiferroics has experienced a rapid progress resulting in the discovery of many new physical phenomena. BiFeO3 (BFO) compound, which is one of the few room-temperature single-phase multiferroics, has contributed subsequently to this progress. As a result, significant review articles have been devoted specifically to this famous system. This chapter is dedicated to the strain effects on the structure stability and property changes of BFO thin films. It is a short and non-exhaustive topical overview that may be seen as an invitation for interested readers to go beyond. There is a very active and prolific research in this field and we apologize to the authors whose relevant work is not cited here. After a short introduction, we will thus review the effect of strain on BFO films by describing the consequences on the structure and the phase transitions as well as on polar, magnetic and magnetoelectric properties. 相似文献
66.
Dr. Lars Borchardt Dr. Martin Oschatz Prof. Dr. Stefan Kaskel 《Chemistry (Weinheim an der Bergstrasse, Germany)》2016,22(22):7324-7351
Lithium–sulfur batteries are among the most promising electrochemical energy storage devices of the near future. Especially the low price and abundant availability of sulfur as the cathode material and the high theoretical capacity in comparison to state‐of‐the art lithium‐ion technologies are attractive features. Despite significant research achievements that have been made over the last years, fundamental (electro‐) chemical questions still remain unanswered. This review addresses ten crucial questions associated with lithium–sulfur batteries and critically evaluates current research with respect to them. The sulfur–carbon composite cathode is a particular focus, but its complex interplay with other hardware components in the cell, such as the electrolyte and the anode, necessitates a critical discussion of other cell components. Modern in situ characterisation methods are ideally suited to illuminate the role of each component. This article does not pretend to summarise all recently published data, but instead is a critical overview over lithium–sulfur batteries based on recent research findings. 相似文献
67.
Above,below, and in‐between the two glass transitions of ultrathin free‐standing polystyrene films: Thermal expansion coefficient and physical aging 下载免费PDF全文
In previous work we observed two simultaneous transitions in high molecular weight (MW) free‐standing polystyrene films that were interpreted as two thickness‐dependent reduced glass transition temperatures (Tgs). The weaker lower transition agreed well with the MW‐dependent Tg(h) previously reported, while the much stronger upper transition matched the MW‐independent Tg(h) previously observed in low‐MW free‐standing films. Here, we investigate the nature of these two transitions by inspecting the temperature dependence of the films' thermal coefficient of expansion (TCE) and present physical aging measurements using ellipsometry both below and in‐between the two transitions. TCE values indicate approximately 80 to 90% of the film solidifies at the upper transition, while only 10 to 20% remains mobile to lower temperatures, freezing out at the lower transition. Physical aging is observed at a temperature below the upper transition, but above the lower transition, indicative of the upper transition being an actual glass transition associated with the α‐relaxation. © 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2015 , 53, 64–75 相似文献
68.
采用密度泛函理论B3LYP方法,研究了锡苯和铅苯的[2+2],[4+2]及[4+4]二聚反应的微观机理和势能剖面,考察了Sn(Pb)原子上的2,4,6-三甲基苯基(Mes)取代基对反应势能剖面的影响.研究结果表明,所有反应均为协同过程,且大多数情况下,2个C—Sn(Pb)键同步形成.[2+2]和[4+2]反应在热力学和动力学上均比相应的[4+4]反应容易进行,而[4+2]反应在动力学上比相应的[2+2]反应有利.Sn(Pb)原子上的Mes取代基在热力学和动力学上均不利于反应的进行.铅苯的动力学稳定性与锡苯相当,但其热力学稳定性高于锡苯. 相似文献
69.
Theoretical investigations on the insertion reaction mechanisms of three- membered-ring silylenoid H2 Si Li F with GeH 3R(R = F, OH, NH2) have been systematically carried out by combined density functional theory(DFT) and ab initio quantum chemical calculations. The geometries of all stationary points for these reactions were optimized using the B3 LYP method and then the QCISD method was used to calculate the single-point energies. The calculated results indicate that, there are one precursor complex(Q), one transition state(TS), and one intermediate(IM) which connect the reactants and the products along the potential energy surface. The insertion reactions of three-membered-ring silylenoid with Ge H3 R proceed in a concerted manner, forming H2RSi-Ge H3 and Li F. The calculated potential energy barriers of the three reactions are 29.17, 30.90, and 54.07 k J/mol, and the reaction energies for the three reactions are –127.05, –116.91, and –103.31 k J/mol, respectively. The insertion reactions in solvents are similar to those in vacuum. Under the same situation, the insertion reactions should occur easily in the following order: GeH 3-F GeH 3-OH GeH 3-NH2. The elucidations of the mechanism of these insertion reactions provided a new mode of silicon-germanium bond formation. 相似文献
70.