芴2,7位取代的9,9’-二芳基螺芴类化合物的合成及性能

设计并合成了一系列以三苯胺为核,芴衍生物为外围基团的有机蓝光小分子,该合成通过Suzuki反应在9-芳基芴的2位和(或)7位引入相同或不同取代基作为模块,并利用Friedel-Crafts反应将4-甲基三苯胺与这一系列模块结合.用NMR,MS和元素分析进行结构表征.荧光测试结果表明该类化合物溶液的荧光发射波长范围在442～466 nm之间,属蓝光发射.电化学测试显示该类材料的HOMO能级位于-5.15～-5.19 eV之间.差示扫描量热仪与热重分析得出化合物的玻璃化转变温度在166℃以上,热分解温度高于398℃,表明该类材料具有良好的热稳定性.     

One-step synthesis of lamellar molybdate pillared hydrotalcite and its application for AZ31 Mg alloy protection

A novel anticorrosion pigment for AZ31 Mg alloy protection, molybdate pillared hydrotalcite (HT-MoO₄^2?), was successfully fabricated via a simple one-step process. The physicochemical properties of the samples were well characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), Fourier transform infrared spectroscopy (FT-IR), Raman spectra, and inductively coupled plasma (ICP) method, respectively. The results indicated that the material showed typical characteristics of molybdate intercalated hydrotalcite. Additionally, it was found that the sample exhibited nano-sized lamellar morphology with the particle size of 35–60 nm. Moreover, the coating on AZ31 Mg alloy containing HT-MoO₄^2? pigment showed obviously higher corrosion protection performance in comparison with the strontium chromate (SC) pigment by Electrochemical impedance spectroscopy (EIS) measurements. The mechanism of corrosion protection was proposed to be that the HT-MoO₄^2? pigment in the coating would cause the pigment to undergo amphoteric ion exchange with aggressive NaCl solution, leading to the release of molybdate and Zn²⁺ inhibitors.     

The origin of the high performance of tungsten carbides/carbon nanotubes supported Pt catalysts for methanol electrooxidation

The Pt supported on WC modified MWCNT catalysts (PtWC/MWCNT) were synthesized by the combination of organic colloidal and intermittent microwave heating (IMH) methods for the first. The results proved the better performance of the PtWC/MWCNT catalyst than that of Pt/C for methanol oxidation in terms of the onset potential and peak current density. The synergistic effect between Pt nanoparticles and WC and the structure effect of the MWCNTs could be the reasons to result in the high activity. The CO stripping test provided the evidence that the onset potential shift for methanol oxidation is consistent with the reduction in the overpotential for the CO oxidation on PtWC/MWCNT catalyst. Therefore, the mechanism of the high performance for methanol oxidation on PtWC/MWCNT catalyst is probably the easier oxidation of CO-like species which cause high overpotential for further oxidation of methanol.     

Spacelike Willmore surfaces in 4-dimensional Lorentzian space forms

Spacelike Willmore surfaces in 4-dimensional Lorentzian space forms, a topic in Lorentzian conformal geometry which parallels the theory of Willmore surfaces in S4, are studied in this paper. We define two kinds of transforms for such a surface, which produce the so-called left/right polar surfaces and the adjoint surfaces. These new surfaces are again conformal Willmore surfaces. For them the interesting duality theorem holds. As an application spacelike Willmore 2-spheres are classified. Finally we construct a family of homogeneous spacelike Willmore tori.     

Piezoelectric and bonding properties of a cement-based composite for dental application

A cement-based piezoelectric composite was introduced as real-time health monitoring systems to dentin. Lithium sodium potassium niobate and zinc polycarboxylate cement were mixed and made piezoelectric under different poling conditions. X-ray diffraction and scanning electron microscope confirmed the component and microstructure of the cement. The bonding force of the composites was compared to that of pure cement by analysis of variance. The optimum poling method was determined and the influencing factors of piezoelectric coefficient were discussed.     

CCD数码照相系统分辨率测试技术研究

介绍了CCD数码照相系统电视分辨率和空间分辨率的实验测试方法。以实验测试为基础定量地给出了数码照相系统可达到的分辨能力 (6 0 0TVL和 71条线 /mm)。在现有条件下 ,作者对传统冲洗金相显微照片同相同试样金相组织的电子金相照片进行了比较 ,并得到了满意的结果。     

A General Theoretical Model of Enthalpy‐Entropy Compensation

Enthalpy‐entropy compensation remains a mystery in chemistry and biophysics. Recent study suggested that the solvent reorganization might constitute the physical origin of the compensation, which was unfortunately not widely applicable because compensation was also observed in solid phase reactions. In this study, a general theoretical model based upon strict mathematical deduction was presented, which indicated that the redistribution of the distinguishable subspecies might be the physical origin of the enthalpy‐entropy compensation in complex systems. As examples, the enthalpy‐entropy compensations in solvation and surface adsorption were discussed.