Mg0.3Fe2.7GeTe2 单晶的磁性及霍尔效应研究

Fe3GeTe2 是一种具有稳定长程磁有序的准二维范德瓦尔斯磁性材料, 范德瓦尔斯材料的稳定性和可调性使其在自旋电子器件的应用方面具有巨大潜力. 本文用助熔剂法生长了 Mg 原子掺杂Fe2 位的 Mg0.3Fe2.7GeTe2单晶样品, 并对 Mg 掺杂Fe3GeTe2 的结构、磁性和输运性质的影响进行了研究. 磁性数据表明 Mg 掺杂后铁磁转变温度不变, 但样品的饱和磁矩减小. 输运性质的测量中观察到各向异性的反常霍尔效应, 与Fe3GeTe2 相比, Mg掺杂后的反常霍尔电阻率减小, 同时各向异性发生了变化.     

对流层夜间化学研究

NO3自由基与N2O5是对流层夜间化学的关键物种。一方面NO3与O3等组分是夜间大气中的重要氧化剂,与它们的反应是生物排放挥发性有机物（VOCs）的主要汇;另一方面NO3与N2O5和雨滴或气溶胶颗粒物发生的异相反应则是大气中氮氧化合物NOx（NO,NO2）的主要清除过程,从而可以减轻对流层臭氧污染。研究它们的化学反应性质及对其进行实地测量,对深入理解大气氧化过程和全面了解区域乃至全球大气自净能力有重要意义。本文总结了近年来有关夜间化学的研究成果,介绍了以NO3和N2O5为中心的基本夜间化学过程、对流层中NO3与N2O5的源与汇以及外场测量技术的最新研究进展,并提出了尚待解决的一些问题。     

采用新型引发剂乳液聚合法合成高相对分子质量聚乙烯醇

采用新型引发剂偶氮二异(N-胺乙基)丁脒(ABEA)对醋酸乙烯酯的低温乳液聚合进行了研究。通过正交试验得出了高相对分子质量聚醋酸乙烯酯的最佳工艺配方。讨论了引发剂浓度、反应温度和乳化剂浓度对聚合物相对分子质量和转化率的影响。对高相对分子质量聚醋酸乙烯酯醇解工艺进行了探讨,并获得了聚合度为3500~4000的聚乙烯醇。     

WO3 homojunction photoanode: Integrating the advantages of WO3 different facets for efficient water oxidation

The manipulation of the surface property of WO₃ photoanode is the main breakthrough direction to improve its solar water oxidation performance both in thermodynamics and kinetics.Here,we report a WO₃(002)/m-WO₃ homojunction film that is composed of an upper WO₃ layer with predominant(002)facet(WO₃(002))and a lower WO₃ layer with multi-crystal facets(m-WO₃)as a photoanode for solar water oxidation.Due to the synergistic effect of WO₃(002)layer and m-WO₃ layer,better water oxidation activity and stability are achieved on the WO₃(002)/m-WO₃ homojunction film relative to the m-WO₃ and WO₃(002)film.Specifically,the improved water oxidation performance on the WO₃(002)/m-WO₃ homojunction film is attributed to the followings.In thermodynamics,the band position differences between WO₃(002)layer and m-WO₃ layer lead to the formation of WO₃(002)/m-WO₃ homojunction,which has positive function of improving their charge separation and transfer.In kinetics,the upper WO₃(002)layer of the WO₃(002)/m-WO₃ film has superior activity in the adsorption and activation of water molecules,water oxidation on this homojunction film photoanode is inclined to follow the four-holes pathway,and the corrosion of photoanode from the H₂O₂ intermediate is restrained.The present work provides a new strategy to modify the WO₃ photoanodes for thermodynamically and kinetically efficient water oxidation.     

鲁科版高中化学必修新教材情境素材分析与教学建议

研读新课程标准中的相关要求,分析鲁科版必修新教材的情境素材类型和呈现方式,得出教材中情境素材具有:微项目使实践情境大放异彩、史实情境彰显中华民族自信、情境素材充分体现STSE教育理念等特点.据此提出从静态的教材情境到动态的教学情境转化的3条教学建议:充分重视教材栏目所蕴含的情境教学功能;深挖教材情境素材所承载的学科核心...     

Synthesis and Crystal Structure of a New Zn(II) Nitronyl Nitroxide Complex [Zn(NIT4Py)(PDA)(H2O)3]

1 INTRODUCTION Nitronyl nitroxides, independently or in combina- tion with metal ions, have been one of the most wi- dely studied systems in molecular magnetism for understanding radical-radical or metal-radical inte- ractions as well as for synthesizing organic ferroma- gnets and metal-radical magnetic materials[1～4]. Up to now, lots of metal-radical complexes have been reported[5～8]. On the other hand, cooperative inter- molecular interactions, such as coordination bonds, hydrogen bon…     

Poly(terephthalic anhydride) single crystals: Morphology and crystal structure

Single crystals of poly(terephthalic anhydride) (PTA) have been grown using the confined thin film melt polymerization technique. Thin lamellae (ca. 50 Å) are found for low polymerization temperatures, with thick crystals forming for polymerization at 200°C. Shearing of the material shortly after the initiation of polymerization at 200°C yielded single crystal domains composed of fibrillar texture material; these samples gave [010] zone ED patterns complementing the [001] zone patterns from the unsheared CTFMP samples. A monoclinic, single chain, two repeat unit, unit cell (Pc11) is proposed based on four different electron diffraction zone patterns: a = 6.01 Å, b = 3.94₅ Å, c = 14.11 Å, α = 106.9°. Simulations, using the Cerius² program, of the corresponding molecular conformation, packing and electron diffraction (ED) patterns were performed; the ED simulations are in good agreement with the observed patterns. An R-factor of 0.23 is obtained based on a comparison of calculated and observed structure factors for the 39 independent ED reflections observed on the different zone patterns. © 1996 John Wiley & Sons, Inc.     

Stereochemistry of the hydrogenation of o-xylene over a silica-supported polysilazane–platinum complex

Silica-supported polysilazane (SiO₂-Si-N), and its platinum complex (SiO₂-Si-N-Pt) were prepared. It was found that SiO₂-Si-N–Pt can catalyze hydrogenation of o-xylene under mild conditions (40–50°C, 1 atm). The products of the reaction were cis-and trans-1,2-dimethylcyclohexane. The formation of trans-1,2-dimethylcyclohexane may be adequately explained according to the ‘roll-over’ model. The stereoselectivity was influenced by temperature and catalyst concentration, the proportion of the cis isomer decreasing with an increase in each of the two factors. The effects of other reaction parameters, such as the N/Pt mole ratio in the complex, solvents and reaction time, etc. on the hydrogenation of o-xylene were also studied. The SiO₂-Si-N–Pt catalyst is very stable in reaction and turnover numbers amount to 200 in 80 hr.     

控制结晶-微波碳热还原法制备高密度LiFePO4/C

应用控制结晶法从溶液相制备球形FePO4.xH2O,再高温烧结得到FePO4前驱体,最后用微波碳热还原法合成高密度L iFePO4/C.由XRD和SEM表征该材料的结构、形貌,并测试其电化学性能.