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131.
Ming‐Han Liu Yao‐Hung Tseng Heather F. Greer Prof. Dr. Wuzong Zhou Prof. Dr. Chung‐Yuan Mou 《Chemistry (Weinheim an der Bergstrasse, Germany)》2012,18(50):16104-16113
Mesocrystals of ZnO were synthesized hydrothermally by using gum arabic as a structure‐directing agent. Their hierarchical structure has a unique twin‐brush form consisting of vertically aligned nanorods in a single‐crystal‐like porous form. The formation mechanism of the twin‐brush ZnO was investigated by quenching a series of samples at different times and examining them by TEM, SEM, and XRD. The alignment of ZnO crystal units can be modulated by adding simple salts such as KCl to change the units from nanorods to nanoplates. This can be explained by screening the dipolar force of the polar crystal. Local cathodoluminescence of twin‐brush ZnO was used to follow the local structure changes. 相似文献
132.
V. BabayanN.E. Kazantseva R. Mou?kaI. Sapurina Yu.M. SpivakV.A. Moshnikov 《Journal of magnetism and magnetic materials》2012,324(2):161-172
This work is devoted to the analysis of factors responsible for the high-frequency shift of the complex permeability (μ?) dispersion region in polymer composites of manganese-zinc (MnZn) ferrite, as well as to the increase in their thermomagnetic stability. The magnetic spectra of the ferrite and its composites with polyurethane (MnZn-PU) and polyaniline (MnZn-PANI) are measured in the frequency range from 1 MHz to 3 GHz in a longitudinal magnetization field of up to 700 Ое and in the temperature interval from −20 °С to +150 °С. The approximation of the magnetic spectra by a model, which takes into account the role of domain wall motion and magnetization rotation, allows one to determine the specific contribution of resonance processes associated with domain wall motion and the natural ferromagnetic resonance to the μ?. It is established that, at high frequencies, the μ? of the MnZn ferrite is determined solely by magnetization rotation, which occurs in the region of natural ferromagnetic resonance when the ferrite is in the “single domain” state. In the polymer composites of the MnZn ferrite, the high-frequency permeability is also determined mainly by the magnetization rotation; however, up to high values of magnetizing fields, there is a contribution of domain wall motion, thus the “single domain” state in ferrite is not reached. The frequency and temperature dependence of μ? in polymer composites are governed by demagnetizing field and the induced magnetic anisotropy. The contribution of the induced magnetic anisotropy is crucial for MnZn-PANI. It is attributed to the elastic stresses that arise due to the domain wall pinning by a polyaniline film adsorbed on the surface of the ferrite during in-situ polymerization. 相似文献
133.
Haiyan Mou Fei Shen Qingfeng Shi Yizhou Liu Chifei Wu Weihong Guo 《European Polymer Journal》2012,48(4):857-865
In this work, an inorganic metal salt, zinc chloride (ZnCl2), was mechanically mixed with nitrile butadiene rubber (NBR) to prepare a novel crosslinkable NBR/ZnCl2 composite. ZnCl2 was found to dissolve into NBR upon heating to a designed temperature, which was considered as a result of dissolution process induced by the occurrence of coordination reaction. Consequently, the morphology of the composite could change from an obvious two-phase structure to a macro-homogeneous phase structure. The determination of the coordination bonding in NBR/ZnCl2 composite was done by Fourier transform infrared spectroscopy. The crosslinking procedure of the composite was investigated by dynamic mechanical analysis and differential scanning calorimetry. A Kissinger’s method was used to calculate the active energy. Other characterizations including scanning electron microscopy, elemental analysis, X-ray Diffraction and polarized microscope with a hot stage were used to investigate the morphology of the composite. Furthermore, the resulting material possessed special and excellent tensile properties. 相似文献
134.
A series of chiral 5,6-dihydro-1,4-oxazin-2-one substrates, as preformed cyclic aldimines and ketoimines, were employed to develop a new asymmetric Ugi three-component reaction for the first time. The Ugi reaction of the imines, isocyanides, and carboxylic acids opens an efficient access to novel morpholin-2-one-3-carboxamide compounds. The chiral imines showed promising stereoinduction for the new chiral center of the Ugi products, and predominant trans-isomers were obtained in the most cases. Addition of some Lewis acids or proton acids could improve the diastereoselectivity further but usually led to a drop in total yield. The Ugi-3CR could be extended to the stereoselective synthesis of ketopiperazine-2-carboxamide derivatives. 相似文献
135.
136.
离子色谱法在食品分析中的最新应用 总被引:9,自引:0,他引:9
综述了离子色谱法在食品分析中的最新应用 ,并对这方面的发展趋势进行了讨论。 60篇。 相似文献
137.
Nanocrystalline tin‐oxide particles were prepared as electrodes on the bases of ITO glass and AT‐cut quartz crystals (sputtered gold), respectively, and characterized for their electrochemical behavior. Experiments suggested that the SnO2 particles could induce an energy barrier to the redox reactions taking place on the electrode surface. When the amount of SnO2 exceeded ca. 10?7 mol cm?2, electrochemical activity demonstrated by the solution redox couples was entirely suppressed. Nevertheless, electrochemical impedance spectroscopic (EIS) measurements suggested that mutual communication between redox couples would still take place on the surface of SnO2. For instance, although the CV curves of Fe(CN)63‐/4‐ were completely blocked, the exchange current of Fe(CN)63‐/4‐ could still flow through the tin‐oxide modified electrode, increasing with its concentration up to 40 mM. The propagation of electrons in the SnO2 film was likely via a hopping mechanism. Electrochemical quartz microbalance (EQCM) measurements, in addition, suggested that a charge‐compensating cation (K+ or H+) uptake reaction may be induced as electrons were pumped to the Sn02 electrode, while, if electrons were removed, that could cause water desorption. Analysis based on the Frumkin adsorption isotherm showed the driving force behind the adsorption of water on SnO2 is about ?2 kcal/mol. Nonetheless, the adsorbed water might face a competitive repulsion from acetonitrile when acetonitrile was used as the electrolyte medium. 相似文献
138.
Hung‐Te Chang Kuo‐Chen Chiang Fung Fuh Wong Chun‐Sheng Huang Yang‐Ming Liao Wen‐Fa Kuo Shaw‐Bing Won Mou‐Yung Yeh 《Heteroatom Chemistry》2007,18(4):438-442
The synthesis of potential fluorescent active 4‐(5‐aryl‐1,3,4‐oxadiazol‐2‐yl)phenylhydrazine derivatives was accomplished in three steps. The key step was the dehydration cyclization of 1,2‐diacylhydrazines to form the 1,3,4‐oxadiazole ring by use of acetic anhydride/perchloric acid mixture as the dehydrating agent. The sydnone moiety served as the masked hydrazines, which could be demasked by HCl for further application. © 2007 Wiley Periodicals, Inc. Heteroatom Chem 18:438–442, 2007; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/hc.20318 相似文献
139.
纳米ZnO颗粒在阳极Al2 O3模板中的强光致发光研究 总被引:1,自引:0,他引:1
用金属醇盐水解法在阳极Al2O3模板的有序孔洞中生长了纳米量级的ZnO颗粒,并用扫描电子显微镜(SEM)和高分辨电子显微镜(HRTEM)对其形貌进行观察.对纳米ZnO/多孔阳极Al2O3模板组装体的光致发光谱进行测量,将组装体中纳米ZnO颗粒的发光强度与常规方法制备的纳米ZnO颗粒发光强度做了比较,就发光强度提高的原因进行了讨论. 相似文献
140.
在理论上详细描述了一种新型的激光偏振移相干涉测振系统.通过计算机对两路正交干涉光电信号的接收和正弦逼近法数字处理,在1Hz~10KHz宽频带内测量振动台的振幅和初相位,从而实现加速度传感器复合灵敏度的绝对校准.运用琼斯矩阵证明干涉系统中通过偏振片调整可保证两信号的正交性. 相似文献