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971.
Jianbing Hua Chao Wu Liming Zou Shuyun Chen Hongwei Lu Yongjing Xu Xianyang Peng 《Journal of Thermal Analysis and Calorimetry》2017,128(3):1273-1278
In this study, a series of binary mixtures of N-butyl stearate (nBS) and methyl palmitate (MP) were used to produce a novel composite phase change material (CPCM) for potential application in the eastern China, and their thermal properties were investigated by differential scanning calorimetry (DSC). The results of DSC indicated that the mixture consisting of 10 mass% nBS and 90 mass% MP is optimum as the CPCM in terms of the phase change temperature ranges (T f = 19.74–5.59 °C; T m = 18.34–33.80 °C) and latent heats (ΔH f = 176.8 J g?1; ΔH m = 189.3 J g?1). On the other hand, the thermal reliability and chemical stability of the CPCM after 120, 180, 240, 300, 360 and 500 accelerated thermal cycling tests were studied by DSC and fourier transform infrared (FTIR) analysis. The results demonstrated that the CPCM had good thermal reliability and chemical stability. 相似文献
972.
Effect of halogen bonding on supramolecular assembly and photophysical properties of diaryl oxalates
Dong-En Wu Yang-Hui Luo Man-Ning Wang Qing-Ling Liu Gao-Ju Wen Ling-Jun Zhu Chang-Po Fan Bai-Wang Sun 《Structural chemistry》2017,28(6):1731-1742
In order to determine the effect of halogen bonding on supramolecular assemblies and photophysical properties of diaryl oxalates, diaryl oxalate itself and its derivatives with fluorine, chlorine, bromine, and iodine substituents in the p-position of phenyl rings were studied and compared. Their single-crystal structures were studied by geometrical analysis and theoretical calculation. The study reveals that different halogen bonds are formed with respect to different halogen atoms, such as C…F and X…X (bromine and iodine atoms) interactions, and molecular stacking modes would be affected by halogen bonds directly. Comparative studies of photophysical properties in dilute solution and solid state indicate that halogen substitutions would not affect the emission processes of diaryl oxalates in dilute solution; this is not the case for their solid state. This work has demonstrated that halogen bonds play an important role in regulating structures and photophysical properties of diaryl oxalates. 相似文献
973.
Yong-Ming Cui Lu Qiao Yi Li Qian Wang Wu Chen Wen-Xuan Yan 《Transition Metal Chemistry》2017,42(1):51-56
A series of dioxomolybdenum(VI) complexes with similar hydrazone ligands have been prepared, specifically [MoO2L1(MeOH)] (1), [MoO2L2(MeOH)] (2) and [MoO2L3(MeOH)] (3), where L1, L2 and L3 are the dianionic forms of 2-chloro-N′-(2-hydroxybenzylidene)benzohydrazide, 2-chloro-N′-(2-hydroxy-5-methylbenzylidene)benzohydrazide and N′-(3-bromo-5-chloro-2-hydroxybenzylidene)-2-chlorobenzohydrazide, respectively. The complexes were characterized by physicochemical and spectroscopic methods and also by single-crystal X-ray determination. The hydrazone ligands coordinate to the Mo atoms through their phenolate O, imine N and enolic O atoms. The Mo atoms are six-coordinated in octahedral geometries. The complexes show high catalytic activities and selectivities in the epoxidation of cyclohexene with tert-butylhydroperoxide as primary oxidant. 相似文献
974.
采用硝酸–高氯酸湿法消解或硝酸–双氧水微波消解植物样品,以电感耦合等离子体原子发射光谱法同时测定样品溶液中钾、钠、钙和镁含量。用该法测定灌木枝叶和茶叶标准样品,测定值均在标准值范围内,测定结果的相对标准偏差为0.45%~4.05%(n=8)。钾、钠、钙、镁的加标回收率分别为94.4%~107.6%,92.6%~107.9%,93.7%~105.4%,92.9%~107.2%。该方法操作简便,测量精密度和准确度完全满足植物中钾、钠、钙和镁含量的测定要求。 相似文献
975.
Effect of chain structure on the glass transition temperature and viscoelastic property of cis‐1,4‐polybutadiene via molecular simulation 下载免费PDF全文
Yangyang Gao Youping Wu Jun Liu Liqun Zhang 《Journal of Polymer Science.Polymer Physics》2017,55(13):1005-1016
In this work, by adopting the united atom model of cis‐1,4‐poly(butadiene) (PB), we systemically investigate the effect of the chain structure on the glass transition temperature (Tg) and the viscoelastic property of PB system. First, we analyze the atom translational mobility, bond reorientation dynamics, torsional dynamics, conformational transition rate, and dynamic heterogeneity of the PB chains with different chain structures in detail by determining the corresponding Tg. In addition, our results clearly indicate that with the decrease of the amount of the free end atoms of PB via the end‐linking method, the mobility of the PB chains quickly decreases. As a result, the Tg of the PB chains gradually increases. Depending on the chain structure and the calculation method, the Tg of the PB chains varies from 154 to 240 K. In addition, the temperature dependence of the dynamic properties has different Arrhenius behaviors above and below Tg. The calculated activation energy varies from 7.37 to 16.37 KJ/mol for different chain structures above Tg, which can be compared with those for other polymers. In addition, through the end‐linking approach the strong interaction between the PB chains improves the storage modulus G′ and the loss modulus . Meanwhile, the immobility of the free end atoms effectively reduces the friction loss of the chains under the shear field, which is reflected by the low loss factor . In summary, this work can further help to understand the effect of the chain structure on the dynamic properties of the PB chains. Meanwhile, it provides an effective approach to reduce the energy loss during the dynamic periodic deformation, which can cut the fuel consumption via the end‐linking method. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2017 , 55, 1005–1016 相似文献
976.
Intermolecular H···O═C bonds induced 2D self‐assembly of thiophene based diketopyrrolopyrrole derivative 下载免费PDF全文
Yican Wu Jinxing Li Bao Zha Xinrui Miao Lei Ying Wenli Deng 《Surface and interface analysis : SIA》2017,49(8):735-739
Compounds with diketopyrrolopyrrole (DPP) and thiophene moieties have attracted considerable attention because of their promising charge transport properties. The molecular conformation and self‐assembly of 2,5‐dihexadecyl‐3,6‐di(thiophen‐2‐yl)‐2,5‐dihydropyrrolo[3,4‐c]pyrrole‐1,4‐dione (TDPP‐C16) molecule have been investigated by scanning tunneling microscopy and density functional theory alculation. The TDPP‐C16 molecules adsorb with their optimized S‐shaped conformation and form a zipper‐like pattern on highly oriented pyrolytic graphite surface. R and S rotated structures are observed. The nanostructure is dominated by intermolecular double hydrogen bonds between C═O of the DPP units and hydrogen atom of thiophene rings in the neighboring molecules in each row. Atomic force microscopy and density functional theory calculation also display the existence of strong intermolecular hydrogen bonding. The results provide molecular evidence for the intermolecular interactions of the surface structure, which could benefit to the design of the organic semiconducting materials and understanding of underlying principle of charge transfer process. Copyright © 2017 John Wiley & Sons, Ltd. 相似文献
977.
Xiu-li Yan Xing Wu Jian-fei Zhou Zhi-guo Zhang Jinguo Wang 《Journal of Crystal Growth》2000,220(4):543-547
High optical quality Er3+:YVO4 laser crystals have been grown by using the floating zone method (FZ). The spectroscopic properties and 3 μm lasing of Er3+:YVO4 were investigated. It is found that the Er3+ concentration has a negative effect on the emission of the transition 4I13/2→4I15/2(1.55 μm ), and a positive effect on that of the 4I11/2→4I13/2 transition (2.68 μm). With direct upper-state pumping and a plane-concave cavity a self-terminating laser was achieved at the wavelength of 2.724 μm in the 30 at% Er3+ doped sample. 相似文献
978.
979.
Zhenye Ma Cheng Li Rujun Wu Rizhi Chen Zhenggui Gu 《Journal of Crystal Growth》2009,311(21):4575-4580
In this paper, a novel ceramic membrane anti-solvent crystallization (CMASC) method was proposed for the safe and rapid preparation ammonium perchlorate (AP) crystals, in which the acetone and ethyl acetate were chosen as solvent and anti-solvent, respectively. Comparing with the conventional liquid anti-solvent crystallization (LASC), CMASC which successfully introduces ceramic membrane with regular pore structure to the LASC as feeding medium, is favorable to control the rate of feeding rate and, therefore, to obtain size and morphology controllable AP. Several kinds of micro-sized AP particles with different morphology were obtained including polyhedral-like, quadrate-like to rod-like. The effect of processing parameters on the crystal size and shape of AP crystals such as volume ratio of anti-solvent to solvent, feeding pressure and crystallization temperature were investigated. It is found that higher volume ratio of anti-solvent to solvent, higher feeding pressure and higher temperature result in smaller particle size. Scaning electron microscopy (SEM) and X-ray diffraction (XRD) were used to characterize the resulting AP crystals. The nucleation and growth kinetic of the resulting AP crystals were also discussed. 相似文献
980.