周期极化掺镁不同组分LiNbO3晶体的研究

利用气相平衡扩散法研制出掺镁不同组分的LiNbO₃晶体，并对其极化特性进行了研究.研究表明晶体的开关电场和自发极化不仅与晶体组分［Li］/［Nb］比有关而且与掺镁量有关，［Li］/［Nb］比为0.973掺入2mol% MgO的近化学比LiNbO₃晶体的开关电场仅为1.8kV/mm，是同成分晶体的1/12，且其极化结构的质量要远好于同成分LiNbO₃晶体和近化学比LiNbO₃晶体. 关键词： 气相平衡扩散 3晶体')" href="#">掺镁LiNbO₃晶体 周期极化     

汉语会话中反问应答衔接语的话语标记功能研究

汉语会话中有很多仅起到衔接连贯作用的意义泛化的应答标记,其中包括了一些经过主观语法化后固化的反问句结构,主要用来衔接话轮,表达一定的主观态度。这些反问句结构可以看作是固化结构或小句层面的话语标记语,其语用功能可以分析为话轮转换标记、应答标记、态度标记和话题标记。     

寻找爱米莉悲剧人生的根源——浅析威廉·福克纳的《献给爱米莉的一朵玫瑰》

本文主要从家庭、婚姻生活以及社会环境方面来寻找爱米莉悲剧人生的原因。封建家庭制度,父亲的独断专制,婚姻生活的不幸以及社会大环境的冷漠造就了爱米莉性格的变态和扭曲。笔者旨在呼吁女性们要增强自信心以及在社会中的自身价值,让人们不要忽视这以往被压抑的女性群体。     

霍尔效应实验及其在电梯中的应用

该文介绍了霍尔效应实验的原理,提出了实验操作中容易忽视的问题及解决办法,并总结了目前霍尔效应在电梯领域的各种应用。     

甲胺与MFI、FAU 及FER型高硅沸石的相互作用

The adsorption of methylamine on highly siliceous MFI, FAU and FER-type zeolites was investigated withXRD, FT-IR, Raman, ^13C and ^29Si MAS NMR, and compared with the adsorption of methanol. As the adsorption of the amine, the relative intensity of XRD peaks of the zeolites has been changed significantly, the high-resolution ^29Si MAS NMR peaks have been broadened and shifted to low field, and the resonance of Si-OH groups has appeared. The vibration of N-H has been shifted to low frequency and C-N vibration moved to high frequency in the IR spectra, and the ^13C resonance peak broadened and shifted to high field for the adsorbed amine. The facts reveal an associating interaction between the perfect framework of the zeolites and the adsorbed methylamine with hydrogen bonds, leading to the formation of Si-OH groups and the high desorption temperature of the methylamine from the zeolites.     

洛莫司汀的1H、13C NMR全归属

应用~1H NMR、~(13)C NMR、DEPT135、~1H-~(13)C HMBC、~1H-~(13)C HSQC、~1H-~1H COSY和~1H-~1H NOESY等多种NMR技术,对文献报道的洛莫司汀(Lomustine)~1H和~(13)C NMR数据进行了修正与补充;特别是应用2D NMR对重叠程度较高的环己烷区进行了指认归属,并确定了其空间构型.     

周期极化掺镁不同组分LiNbO3晶体的研究

利用气相平衡扩散法研制出掺镁不同组分的LiNbO3晶体 ,并对其极化特性进行了研究 .研究表明晶体的开关电场和自发极化不仅与晶体组分 [Li] [Nb]比有关而且与掺镁量有关 ,[Li] [Nb]比为 0 973掺入 2mol%MgO的近化学比LiNbO3晶体的开关电场仅为 1 8kV mm ,是同成分晶体的 1 12 ,且其极化结构的质量要远好于同成分LiNbO3晶体和近化学比LiNbO3晶体 .     

含偶氮苯的咔唑类光折变化合物的合成与光谱研究

通过重氮化偶联反应制备了一种既含偶氮基团又含咔唑基团的光折变材料,并通过红外、紫外和拉曼光谱对其进行了结构鉴定和分析.     

Structural evolution and bandgap modulation of layered β-GeSe2 single crystal under high pressure

Germanium diselenide (GeSe₂) is a promising candidate for electronic devices because of its unique crystal structure and optoelectronic properties. However, the evolution of lattice and electronic structure of $β$-GeSe₂ at high pressure is still uncertain. Here we prepared high-quality $β$-GeSe₂ single crystals by chemical vapor transfer (CVT) technique and performed systematic experimental studies on the evolution of lattice structure and bandgap of $β$-GeSe₂ under pressure. High-precision high-pressure ultra low frequency (ULF) Raman scattering and synchrotron angle-dispersive x-ray diffraction (ADXRD) measurements support that no structural phase transition exists under high pressure up to 13.80 GPa, but the structure of $β$-GeSe₂ turns into a disordered state near 6.91 GPa and gradually becomes amorphous forming an irreversibly amorphous crystal at 13.80 GPa. Two Raman modes keep softening abnormally upon pressure. The bandgap of $β$-GeSe₂ reduced linearly from 2.59 eV to 1.65 eV under pressure with a detectable narrowing of 36.5%, and the sample under pressure performs the piezochromism phenomenon. The bandgap after decompression is smaller than that in the atmospheric pressure environment, which is caused by incomplete recrystallization. These results enrich the insight into the structural and optical properties of $β$-GeSe₂ and demonstrate the potential of pressure in modulating the material properties of two-dimensional (2D) Ge-based binary material.     

粘性高分子表面活性剂的合成研究

利用羟乙基纤维素(HEC)与1,2-环氧十八烷(EO-18)反应制备粘性高分子表面活性剂(EOHEC),探索了不同条件对产物性能的影响规律。研究发现,原料配比、溶胀时间、反应温度是影响EOHEC粘度性能的重要因素。控制合适条件能使HEC被EO-18接枝的程度达到最佳,从而使EOHEC靠主链的水溶性伸展作用及支链的疏水缔合作用形成大的结构单元,提高其粘性,另外,主链的亲水作用及支链的疏水作用,有效地保证了EOHEC水溶液的表面活性。