膨胀石墨/聚苯胺/Fe_3O_4复合材料的制备及吸波性能

采用原位聚合方法制备了膨胀石墨/聚苯胺(EG/PANI)复合材料,将Fe_3O_4负载于EG/PANI表面,得到具有电磁吸收性能的EG/PANI/Fe_3O_4复合材料.通过扫描电子显微镜(SEM)、X射线衍射仪(XRD)、傅里叶变换红外光谱仪(FTIR)及矢量网络分析仪(VNA)等对复合材料的形貌、成分和吸波性能进行了研究.吸波性能分析结果表明,当掺杂浓度为0.05 mol/L,匹配厚度d=2 mm时,样品的最小反射损耗(RLmin)在8.64 GHz处达到-37 dB.随着掺杂浓度的增加,最小反射损耗峰向低频移动,对应的匹配厚度逐渐变厚.材料的介电弛豫极化、涡流损耗及λ/4模型的干涉相消现象出现的双峰,使EG/PANI/Fe_3O_4复合材料在电磁波吸收领域有一定的应用前景.     

聚羟基丁酸酯/碳纳米管复合纳米纤维膜的制备及其对重金属离子吸附分离性能的研究

以聚羟基丁酸酯和碳纳米管为原料,采用三氯甲烷/二甲基甲酰胺混合溶液为溶剂,利用静电纺丝技术制备了聚羟基丁酸酯/碳纳米管复合纳米纤维膜.研究了碳纳米管的含量对纳米纤维膜形貌和力学性能的影响,探讨了复合纳米纤维膜对重金属Cu(II)、Cd(II)和Pb(II)的吸附特性.实验结果表明:加入1 wt%碳纳米管能够将纳米纤维的平均直径从(728±146)nm降低至(468±89)nm,纳米纤维膜的比表面积从27.24 m~2/g提高至43.45 m~2/g;碳纳米管的复合能够有效增强聚羟基丁酸酯纳米纤维,当碳纳米管含量1 wt%为最佳,拉伸强度可达5.85 MPa,较纯聚羟基丁酸酯纳米纤维提升了115%.复合纳米纤维膜对重金属离子具有良好的吸附特性,其对Cu(II)、Cd(II)和Pb(II)的最佳吸附pH值为5,此时最大吸附容量分别为91.04、171.05和197.03mg/g,平衡吸附时间分别约为50、60和60 min,吸附率分别为1.79、2.83和3.28 mg/g/min;热力学和动力学分析表明,复合纳米纤维膜对重金属Cu(II)、Cd(II)和Pb(II)的吸附行为更符合Freundlich模型,吸附过程更符合Pseudo-second order模型;循环使用实验表明,重复使用5次后,其吸附容量可保持在初始值的87%以上,具有较好的使用寿命.     

MoS_2/TiO_2复合催化剂的制备及其在紫外光下的光催化制氢活性

为了研究复合光催化剂在光催化中的制氢效率,采用水热法制备了Mo S2纳米片,然后通过水热法在Mo S2纳米片上负载了TiO_2纳米颗粒,形成了Mo S2/TiO_2异质结复合催化剂。采用冷场发射扫描电子显微镜(FE-SEM)、透射电子显微镜(TEM)、X射线衍射(XRD)、紫外-可见吸收光谱(UV-Vis)、拉曼光谱(Raman),X射线光电子能谱(XPS)对材料的结构和光学性能表征并进行分析。通过光催化制氢测试对光催化剂进行评价,实验结果表明,在波长为365 nm的紫外光照射下,最高光催化制氢速率为1004μmol·h-1·g-1,对应的催化剂的Mo S2含量为30%,其催化速率远大于单一的Mo S2和TiO_2,表明Mo S2/TiO_2复合催化剂在紫外光照下能显著提高光催化产氢性能。基于Mo S2/TiO_2复合光催化剂优越的光催化产氢性能,本文对复合光催化剂的产氢机理做了研究和分析。     

Parabola-Hyperbola P-H kinetic model for NR sulphur vulcanization

A Parabola-Hyperbola (P-H) kinetic model for NR sulphur vulcanization is presented. The idea originates from the fitting composite Parabola-Parabola-Hyperbola (P-P-H) function used by the authors in [1,2] to approximate experimental rheometer curves with the knowledge of a few key parameters of vulcanization, such as the scorch point, initial vulcanization rate, 90% of vulcanization, maximum point and reversion percentage. After proper normalization of experimental data (i.e. excluding induction and normalizing against maximum torque), the P-P-H model reduces to the discussed P-H composite function, which is linked to the kinetic scheme originally proposed by Han and co-workers [3]. Typically, it is characterized by three kinetic constants, where classically the first two describe incipient curing and stable/instable crosslinks and the last reproduces reversion.The powerfulness of the proposed approach stands into the very reduced number of input parameters required to accurately fit normalized experimental data (i.e. rate of vulcanization at scorch, vulcanization at 90%, maximum point and reversion percentage), and the translation of a mere geometric data-fitting into a kinetic model. Kinetic constants knowledge from simple geometric fitting allows characterizing rubber curing also at temperature different from those experimentally tested.The P-H model can be applied also in the so-called backward direction, i.e. assuming Han's kinetic constants known from other models and deriving the geometric fitting parameters as result.Some existing experimental data available, relying into rheometer curves conducted at 5 different temperatures on the same rubber blend are used to benchmark the P-H kinetic approach proposed, in both backward and forward direction. Very good agreement with previously presented kinetic approaches and experimental data is observed.     

Asymptotic behavior toward the combination of contact discontinuity with rarefaction waves for 1-D compressible viscous gas with radiation

This paper is concerned with the large-time behavior toward the combination of two rarefaction waves and viscous contact wave for the Cauchy problem to a one-dimensional Navier–Stokes–Poisson coupled system, modeling the dynamics of a viscous gas in the presence of radiation. We show that the composite wave with small strength is asymptotically stable under partially large initial perturbations. The proofs are based on the more refined energy estimates to control the possible growth of the perturbations induced by two different waves and large data.     

Recent Progress in High-Performance Lithium Sulfur Batteries: The Emerging Strategies for Advanced Separators/Electrolytes Based on Nanomaterials and Corresponding Interfaces

Lithium-sulfur (Li−S) batteries, possessing excellent theoretical capacities, low cost and nontoxicity, are one of the most promising energy storage battery systems. However, poor conductivity of elemental S and the “shuttle effect” of lithium polysulfides hinder the commercialization of Li−S batteries. These problems are closely related to the interface problems between the cathodes, separators/electrolytes and anodes. The review focuses on interface issues for advanced separators/electrolytes based on nanomaterials in Li−S batteries. In the liquid electrolyte systems, electrolytes/separators and electrodes system can be decorated by nano materials coating for separators and electrospinning nanofiber separators. And, interface of anodes and electrolytes/separators can be modified by nano surface coating, nano composite metal lithium and lithium nano alloy, while the interface between cathodes and electrolytes/separators is designed by nano metal sulfide, nanocarbon-based and other nano materials. In all solid-state electrolyte systems, the focus is to increase the ionic conductivity of the solid electrolytes and reduce the resistance in the cathode/polymer electrolyte and Li/electrolyte interfaces through using nanomaterials. The basic mechanism of these interface problems and the corresponding electrochemical performance are discussed. Based on the most critical factors of the interfaces, we provide some insights on nanomaterials in high-performance liquid or state Li−S batteries in the future.     

New polymer electrolyte membrane for medium-temperature fuel cell applications based on cross-linked polyimide Matrimid and hydrophobic protic ionic liquid

New hydrophobic protic ionic liquid, 2-butylaminoimidazolinium bis(trifluoromethylsulfonyl)imide (BAIM-TFSI), has been synthesized. The ionic liquid showed good thermal stability to at least 350 °C. The conductivity of BAIM-TFSI determined by electrochemical impedance method was found to be 5.6 × 10^?2 S/cm at 140 °C. Homogeneous composite films based on commercial polyimide (PI) Matrimid and BAIM-TFSI containing 30–60 wt% of ionic liquid were prepared by casting from methylene chloride solutions. Thermogravimetric analysis data indicated an excellent thermal stability of PI/BAIM-TFSI composites and thermal degradation points in the temperature range 377 °C–397 °C. The addition of ionic liquid up to 50 wt% in PI films does not lead to any significant deterioration of the tensile strength of the polymer. The dynamic mechanical analysis results indicated both an increase of storage modulus E′ of PI/BAIM-TFSI composites at room temperature and a significant E′ decrease with temperature compared with the neat polymer. The cross-linking of the PI with polyetheramine Jeffamine D-400 allowed to prepare PI/Jeffamine/BAIM-TFSI (50%) membrane with E′ value of 300 MPa at 130 °C. The ionic conductivity of this cross-linked composite membrane reached the level of 10^?2 S/cm at 130 °C, suggesting, therefore, its potential use in medium-temperature fuel cells operating in water-free conditions.     

稀土掺杂上转换纳米颗粒-金属有机骨架复合材料的研究进展

稀土掺杂上转换纳米颗粒-金属有机骨架复合材料是一类新型的功能复合材料. 它不仅结合了稀土掺杂上转换纳米颗粒和金属有机骨架这两种材料的特性, 体现了两者复合后的协同效应, 还具有设计灵活和功能易拓展等优势. 本文聚焦稀土掺杂上转换纳米颗粒-金属有机框架复合材料的最新发展, 总结了该类复合材料的制备方法, 介绍了其在生物和催化等领域的应用, 并对其面临的挑战和发展前景进行了展望.     

二维材料用于渗透能转换的研究进展

在河水与海水的交界处实现渗透能提取与捕获是解决未来能源危机的重要方式之一. 渗透能因为储量大, 容易获取以及绿色可持续的优势受到广泛关注. 反向电渗析技术是一种能够有效捕获渗透能的方法之一, 目前已经得到了深入的研究与发展. 离子交换膜是反向电渗析技术转换渗透能的关键组件, 其性能的优异程度决定能量转换效率的高低. 常见的膜材料主要是高分子聚合物及其改性化合物, 最近一些二维材料如石墨烯、 氧化石墨烯、 二硫化钼、 各种框架材料及其改性复合物因优异的选择性离子传输、 纳米级通道、 丰富的表面功能基团以及可修饰性成为捕获渗透能的重要膜材料. 本文综合评述了二维材料作为离子传输通道的类型以及相应的传输机理; 例举了二维材料及其复合物的设计方案和在渗透能转换方面的具体应用; 最后提出了目前二维材料在渗透能转换领域中面临的挑战以及未来的发展方向.