Calorimetric and dielectric effects during polymerization of an elastomer‐containing mixture and liquid‐liquid phase separation

Calorimetry and dielectric spectroscopy of an elastomer, amine terminated butadiene acrylonitrile (ATBN), dissolved in a stoichiometric mixture of ethylene diamine and diglycidyl ether of bisphenol‐A, were studied in real time during the polymerization and phase separation of the mixture. In the two polymer compositions containing 8 w/w % ATBN and 20 w/w % ATBN, the total enthalpy released per mole of DGEBA's reaction was the same, indicating indetectably small changes in molecular interactions before and after the phase separation. The dielectric relaxation spectra showed no evidence for phase separation, which indicated a gradual phase separation with time and the extent of polymerization, and relatively small differences in the permittivity and conductivity between the ATBN particles and the network matrix at the time of phase separation. The equilibrium permittivity and dc conductivity showed a nonideal mixing of ATBN. The stretched exponential relaxation parameter remained at 0.36, but the characteristic dielectric relaxation time and the dc conductivity increased on addition of ATBN. An increase in the temperature had a greater effect on the relaxation time than the increase in the extent of polymerization. © 1999 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 37: 1911–1919, 1999     

基于多分辨率小波变换的复合材料晶粒边缘的检测

材料晶粒的边缘检测是材料三维重构的一个基础性问题,本文简要介绍了利用小波变换探测图像边缘的原理和材料SEM图像的特点,根据Mallat小波理论中图像边缘对应于小波变换模的局部极大值点的理论,采用二次B样条小波对复合材料SEM图像进行了多分辨率小波变换,从低分辨率到高分辨率逐步搜索边缘,并根据不同分辨率噪声的小波系数变化较大的特点,抑制了噪声.成功的检测出FeAl-ZrO2复合材料第二相晶粒的边缘.文章的最后给出了实验结果并且对实验结果进行了讨论.     

SO2存在下钠、钙、铁及其复合物对NO-半焦反应的催化作用

采用程序升温还原技术,在SO2存在气氛下,对钠、钙、铁及其复合物的NO-半焦催化反应性能进行了研究。结果表明,在相同条件下三种金属对NO-半焦反应的催化活性顺序为：Fe>Ca>Na。SO2可能通过参与氧传递过程来影响金属对NO-半焦反应的催化活性。SO2的浓度对负载三种不同金属半焦催化活性的影响是不同的。SO2浓度对负载钠半焦的催化活性影响最为显著。在SO2存在气氛下,负载2％钠或铁和负载3％钙的半焦具有高的NO转化活性。在SO2存在气氛下,钠－钙和钠－铁二元金属复合催化剂的活性较高,这可能是由于这两种金属间存在协同作用的缘故。     

复合晶核剂对黄磷炉渣微晶玻璃析晶的影响

以黄磷炉渣为主要原料,通过添加不同种类的复合晶核剂,采用熔融法制备了黄磷炉渣微晶玻璃.借助化学热力学软件FactSage 6.4模拟计算晶相类型,借助Kissinger方程分析析晶能力,利用X射线衍射仪(XRD)和扫描电子显微镜(SEM)进行验证.结果表明:相比添加单一晶核剂TiO2,复合晶核剂TiO2+CaF2或复合晶核剂TiO2+P2O5均能够降低黄磷炉渣基础玻璃的析晶活化能E,促进其析晶,复合晶核剂TiO2+Cr2O3能够提高黄磷炉渣基础玻璃的析晶活化能E,抑制其析晶;无论添加单一晶核剂TiO2,还是添加复合晶核剂TiO2+CaF2、复合晶核剂TiO2+P2O5或复合晶核剂TiO2+Cr2O3,黄磷炉渣微晶玻璃晶相类型相同,主晶相为硅灰石(CaSiO3),副晶相为铝透辉石(Ca(Mg,Al)(Si,Al)2O6)和氟磷灰石(Ca5(PO4)3F),这与化学热力学软件FactSage 6.4模拟计算结果基本一致.     

HPLC-PDA analysis of ACE-inhibitors,hydrochlorothiazide and indapamide utilizing design of experiments

A simple, rapid, precise, accurate and sensitive high performance liquid chromatographic method has been developed for simultaneous determination of ACE inhibitors with hydrochlorothiazide and indapamide in pharmaceutical formulations. ‘Design of Experiments’ (DoE) using ‘central composite design’ (CCD) was applied to facilitate method development and optimization. Mobile phase was optimized utilizing response surface methodology using Design Expert software. Chromatographic separation was achieved on Hypersil®-Gold C₁₈ (100 × 4.6 mm, 3 μm, Thermo Fisher Scientific, USA), column at 25 °C. The mobile phase was 58% buffer (5 mM KH₂PO₄, containing triethylamine 0.25 ml/L), 25% acetonitrile and 17% methanol (pH adjusted to 2.8 ± 0.1). The analysis was performed at 215 nm. The mobile phase flow rate was 1.0 ml/min and injection volume 10 μl. The method was validated for linearity, limits of quantitation and detection, accuracy, precision, ruggedness and robustness as per the International Conference on Harmonization (ICH) guidelines. Calibration curves (for lisinopril, hydrochlorothiazide, captopril, imidapril, perindopril, indapamide and trandolapril) were linear in the concentration range of 5–35 μg/ml. The limit of detection and limit of quantitation for experimental drugs ranged from 0.03 to 0.61 and 0.08–1.84 μg/ml respectively.     

Nickel(II) cluster‐based mixed‐cation coordination polymer synthesized from 2‐mercaptobenzoic acid and its application

High‐nuclearity metal clusters have received considerable attention not only because of their diverse architectures and topologies, but also because of their potential applications as functional materials in many fields. To explore new types of clusters and their potential applications, a new nickel(II) cluster‐based mixed‐cation coordination polymer, namely poly[hexakis[μ₄‐(2‐carboxylatophenyl)sulfanido]di‐μ₃‐chlorido‐tri‐μ₂‐hydroxido‐octanickel(II)sodium(I)], [Ni₈NaCl₂(OH)₃(C₇H₄O₂S)₆]_n, 1 , was synthesized using nickel chloride hexahydrate and mercaptobenzoic acid (H₂mba) as starting reactants under hydrothermal conditions. The material was characterized by single‐crystal X‐ray diffraction (SCXRD), Fourier transform IR spectroscopy, thermogravimetric analysis, powder X‐ray diffraction and X‐ray photoelectron spectroscopy analysis. SCXRD shows that 1 consists of a hexanuclear nickel(II) [Ni₆] cluster, dinuclear Ni^II nodes and a mononuclear Na^I node, resulting in the formation of a complex covalent three‐dimensional network. In addition, a tightly packed NiO/C&S nanocomposite is fabricated by sintering the coordination precursor at 400 °C. The uniform nanocomposite consists of NiO nanoparticles, incompletely carbonized carbon and incompletely vulcanized sulfur. When used as a supercapacitor electrode, the synthesized composite shows an extra‐long cycling stability (>5000 cycles) during the charge/discharge process.     

Resin‐Derived Ni3S2/Carbon Nanocomposite for Advanced Rechargeable Aqueous Zn‐Based Batteries

The exploration of high‐energy and stable cathode materials is highly desirable and challenging for the development of advanced Zn‐based batteries. In this work, a facile pyrolysis method is reported to synthetize Ni₃S₂/carbon nanocomposite as high‐performance cathode by employing ion exchange resin as a precursor. Attributing to the abundant active sites and enhanced conductivity from well binding between Ni₃S₂ and carbon, a markedly high capacity of 234.3 mA h g^?1 is obtained for this Ni₃S₂/carbon at a high current density of 6.9 A g^?1. Moreover, a Zn‐based battery is demonstrated by using the Ni₃S₂/carbon as a cathode and Zn plate as an anode, which delivers a maximum power density of 58.6 kW kg^?1, together with a peak energy density of 356 W h kg^?1 and 93.7% capacity retention after 5000 charging–discharging cycles. This simple synthetic strategy to achieve robust Ni‐based composite electrodes may open up new opportunities to design other transition metal–based electrodes for energy storage applications.     

Influence of the Si–O–C interplayer on the flexural behaviors of C/Si–C–N composites

Carbon fiber reinforced Si–C–N matrix composite(C/Si–C–N) with a Si–O–C interlayer (C/Si–O–C/Si–C–N) was fabricated via CVI and PIP process. The flexural behaviors of C/Si–O–C/Si–C–N were investigated using the three-point-bending method and the SEM technique. The results indicated that the flexural strengh of the C/Si–O–C/Si–C–N increases with increasing temperature and the modulus of the composite is essentially unchanged. The strength of C/Si–O–C/Si–C–N is comparable to that of C/PyC/Si–C–N, and the role of Si–O–C interlayer in C/Si–C–N can rival that of the PyC interlayer. The weaker interfacial bonding and the larger thickness of Si–O–C interlayer make a contribution to this at RT while the thinner interlayer and unstable structure of Si–O–C interphase do it above 1300 °C.     

三维多孔复合碳层对电极的制备及其光伏性能研究

基于TiO_2光阳极、Pt对电极的染料敏化太阳能电池(DSSC)因其优异的光电转换特性受到了广泛的关注,然而Pt昂贵的价格制约了其发展与应用.针对这一问题,本文设计、制备了一种由相对致密且高导电的石墨膜(PC层,底层)及多孔碳纳米颗粒膜(CC层,顶层)构成的低成本、高性能三维多孔复合碳层对电极.基于该CC/PC对电极的DSSC具有优异的光伏性能:在1.5标准太阳光照射下,其填充因子高达65.28%(较Pt对电极高4.1%)、光电转换效率高达5.9%(为Pt对电极的94.2%). CC/PC对电极的优异光伏性能主要归因于其独特的三维多孔导电结构,该结构有极高的比表面积和丰富的催化反应活性位,有利于电子的快速传输及离子的快速转移,在这些因素的协同作用下,其光电转换性能大大改善.     

非冻结水对微球复合水凝胶机械性能的影响

本文旨在用DSC的方法研究水凝胶结合水的能力与韧性的关系。 分别以甲基丙烯酸丁酯(BMA)或甲基丙烯酸六氟丁酯(HFBMA)和烯丙基胺为单体,制备了2种核壳纳米微球(BMA微球和HFBMA微球)。 再以其作为大分子引发剂和交联剂,制备了微球交联复合水凝胶(BMA-H凝胶和HFBMA-H凝胶)。 通过差示扫描量热仪(DSC)、傅里叶变换红外光谱仪(FTIR)和透射电子显微镜(TEM)等技术手段研究凝胶的结构和性能。 结果表明,HFBMA-H凝胶具有更好的机械性能,其拉伸强度和断裂伸长率分别可达280 kPa和3960%,远高于BMA-H凝胶(101 kPa,2700%)。 通过对2种复合凝胶体系内不同状态的水进行分析,发现HFBMA-H凝胶的非冻结水的质量分数明显高于BMA-H凝胶,这种非冻结水的增塑作用对于凝胶机械强度的提升具有重要影响。