共查询到20条相似文献,搜索用时 62 毫秒
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《高等学校化学学报》2014,(2)
正有机化学总结、复习与提高:重点·难点·习题精解(第二版)有机化学所包含的知识面广,知识点多,学生学习相对困难。为此本书作者根据多年的教学经验,把有机化学教学中的重点、难点及学生容易出现问题的知识点进行了归纳、总结和梳理。全书分别从结构与性质、反应机理、制备反应、化学合成、波谱解析五个专题,对有机化学的基本理论、重点、难点进行了分析和总结,并对某些知识点有所拓宽和加深;同时针对这些知识点编写了相应的习题,并给出详细的解答,可以起到复习、巩固、提高以及备考的作用。 相似文献
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王华 《影像科学与光化学》2017,35(5)
本文综述了近年来噻吩螺烯的化学与光化学合成方面的重要进展。在螺烯的化学合成方面,阐明了单螺烯的常见合成手法,即以并三噻吩为构筑模块,合成螺烯前驱体联并三噻吩,其后通过硫代关环手法制备噻吩单螺烯。由于前驱体的两个并噻吩片段可能存在分子内的相互作用,造成无法无限制增长螺烯分子的尺寸。通过增加助溶基团的合成策略可以将螺烯的分子结构由单螺烯引入到双螺烯。在螺烯的光化学合成方面,光化学氧化关环的实例表明了光化学是构筑单螺烯与双螺烯的有效手法。由于存在前驱体双键在光照条件下可以打开产生双自由基的光化学反应机理,在其后关环步骤可有效产生外消旋体与内消旋体这样有趣的双螺烯产物。此外,本文针对噻吩螺烯领域的前景,提出了3个方面的观点:1)通过设计末端噻吩环上硫原子的位置异构,形成新的螺烯同分异构体;2)通过合成设计,可以制备新结构的双螺烯与多螺烯;3)通过手性拆分,可将螺烯旋光体应用于手性催化、手性组装等应用领域。 相似文献
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This is a popular science article introducing the chemical knowledge contained in the search and use of colors. From the different aspects of architectural, textile dyeing and paints, three examples are chosen to reveal the chemical principles behind. Humanistic story and science interpretations are combined to reflect the close connection between chemistry and human life. 相似文献
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本文介绍了高压条件对凝聚态物质电子结构和晶体结构的影响,其中包括高压对元素外层电子结构、能带结构和晶体缺陷的影响,高压导致的原子配位数的增加、元素非正常氧化态、结构相变和态变。同时从十个方面介绍了高压条件下凝聚态物质间的化学反应,最后对高压条件下凝聚态化学未来的发展做了展望。 相似文献
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高温高压下氧化锌纳米晶的晶粒演化动力学 总被引:3,自引:0,他引:3
用GS-1B型六面顶压机研究了ZnO纳米晶高温高压下的晶粒演化动力学, 用MDI/JADE5 X射线衍射仪(Cu靶)和XL30S-FEG场发射扫描电子显微镜对高压样品的相组成、晶粒尺寸及微观形貌进行了表征. 实验发现300 ℃(包括300 ℃)以下, ZnO纳米材料中晶粒生长速率随着压力的升高先增大后减小, 1~3 GPa烧结体晶粒尺寸随着压力的升高而增大, 4~6 GPa烧结体晶粒尺寸随着压力的升高而减小. 利用高压下晶粒生长速率方程求出1~3 GPa, 4~6 GPa的激活体积分别为-5.82, 9.66 cm3/mol. 400 ℃(包括400 ℃)以上, 1~6 GPa烧结体的晶粒尺寸随着压力的升高而不断增大. 相似文献
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Silicon nanowires (SiNWs) were synthesized with silicon monoxide as the only starting material. At the beginning, a protective gas argon was charged into the reaction chamber and the temperature ramp was controlled at 3 ℃·min-1. The growth condition for SiNWs was controlled at 480 ℃ under the pressure of 2.8 MPa. The morphology and the structure of the products were characterized by TEM, HRTEM and XRD. The results revealed that SiNWs were diamond structure and their diameters were distributed from 5 to 25 nm. The SiNW was single crystal in the central core and was coated with amorphous silica shell at the exterior surface. Influenced by the quantum effect, Raman spectrum of the SiNWs was found to be redshifted. The oxide-assisted growth mechanism was suggested to explain the growth model of self-assembled SiNWs. 相似文献
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单相Ce0.5Zr0.5O2立方固溶体的高压高温合成 总被引:1,自引:0,他引:1
以化学沉淀法制备的 Ce O2 和 Zr O2 纳米微粒为前驱体 ,首次在高压高温 (3 .1 GPa,1 0 73 K)下合成了单相 Ce0 .5Zr0 .5O2 面心立方固溶体 .使用 X射线衍射、TG-DTA、XPS、Raman、电子自旋共振谱和交流阻抗谱等对样品的结构、Ce离子的价态和导电性进行了表征 .实验结果表明 ,纳米 Ce O2 -50 % Zr O2 混合物在高压 (0 .9GPa以上 )高温 (1 0 73 K以上 )条件下可以发生固态反应 ,高压下固溶温度明显降低 .Ce0 .5Zr0 .5O2 面心立方固溶体在 773 K以下是热稳定的 ,不发生结构转变 ,固溶体中 Ce离子完全以 Ce4 + 形式存在 ,773 K退火也不引起 Ce4 + 向 Ce3 + 转变 ,晶格中氧缺位非常少 .Ce0 .5Zr0 .5O2 面心立方固溶体是离子导电 ,82 3 K时电导率 σ=1 .2× 1 0 -5S/cm,与纯 Ce O2 在同温度下的电导率同数量级 ;1 1 2 3 K时 σ=2 .1× 1 0 -3 S/cm,小于掺入稀土或碱土氧化物的氧化锆和氧化铈基电解质的电导率 .在高温区和低温区 ln(σT)与 1 /T的关系满足斜率不同的二条直线 ,低温活化能小于高温活化能 .固溶体的显微硬度 (50 g载荷 )为 572 HV. 相似文献
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用高温高压法合成了Sr1-xEuxTiO3(x=0.0,0.1,0.2,0.3,0.4,0.5)及Ba0.3Eu0.7TiO3化合物.结果表明,所有样品均为立方结构,样品中存在Eu(Ⅱ)和Eu(Ⅲ)的混合价.Eu3+的掺入直接影响了Sr离子与氧离子的结合,使Sr3p3/2的结合能随x的增加而增加. 相似文献
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高温高压水中干酪根热解的拉曼光谱原位研究 总被引:1,自引:0,他引:1
利用对顶砧压腔装置,以金刚石作为顶砧,通过观测和采用拉曼光谱对干酪根在高温高压水中热解的具体过程进行了原位研究.由于金刚石顶砧只在约1 332 cm-1波数出现一个很强很尖锐的峰,因此用于压 标的石英、介质水以及样品干酪根的拉曼峰都未受影响.测试了在450℃和850 MPa条件下干酪根变化的拉 曼峰.随着温度和压力的增加,干酪根在1 600 cm-1波数附近由于芳香环振动引起拉曼峰的最大峰位置 (vmax)和半高宽(FWHM)存在转折变化.在干酪根热解之前,其芳香环结构和无序结构之间的缺陷向有序化变化.而对于干酪根的热解过程,先是热解为液相碳氢化合物,随后进一步热解为更小分子的成分,如 CH4.干酪根的热解过程与压力密切相关,增加压力对热解存在抑制作用. 相似文献
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A New Method of Measurement for Elastic Wave Velocities in Minerals and Rocks at High Temperature and High Pressure and Its Significance 总被引:1,自引:0,他引:1
We developed a new method of measurement for elastic wave velocity of rocks and minerals at high temperature and high pressure in a wedge-type cubic anvil. The shear-wave and other ultrasonic wave can be identified by full wave phase analysis (FWPA), thus the velocities of compression-wave and shear-wave can be obtained in a single experiment. We have done the measurements of elastic wave velocities on pyrophyllite, etc. at high pressure (0.1—5.5 GPa) and high temperature (ambient temperature 1600℃), the ranges of the pressure and the temperature are in the head among the methods of the wave velocites measurement in laboratory in the world. 相似文献
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Ginseng(Panax ginseng C. A. Mey.) is a traditional medicinal herb in Asia. Studies have shown that ginsenosides significantly affect immunoregulation and rare ginsenosides have anti-allergic effects. In this research, a high temperature and high pressure method was utilized to increase the contents of rare ginsenosides in the ginseng extract(GE). The anti-allergic effects of this extract were investigated in vivo. Water was used as the extraction solvent in extracting the rare ginsenosides via the high temperature and high pressure method. Extraction time and temperature were investigated in order to increase the contents of rare ginsenosides. Rare ginsenosides were qualitatively analyzed by HPLC-ESI-MS and quantitatively analyzed by HPLC-UV. Anti-allergic effects of the extracts were assessed using the ovalbumin(OVA)-induced allergic asthma model in vivo. An extraction temperature of 145℃ and extraction time of 2.0 h were chosen as the optimal conditions. Compared with traditional method, the contents of total rare ginsenosides extracted were considerably higher using the new method, that is, 14.74 times that extracted by the traditional method. In our in vivo experiments, treatment with high concentration GE may have anti-allergic effects in decreasing the total amount of IgE in serum and IL-4 in bronchoalveolar lavage fluid(BALF), and in improving the ratio of CD4+ to CD8+ T cells. The high temperature and high pressure method was an effective method to obtain GE containing more rare ginsenosides, which maybe become anti-allergic agents. 相似文献
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