钠离子电池正极材料Na3V2(PO4)2O2F的控制合成与电化学性能优化

采用简单的水热合成法制备氟磷酸钒氧钠(Na_3V_2(PO_4)_2O_2F,简写为NVPOF),通过调节水热反应溶液的pH值和反应温度等关键参数,有效调节NVPOF的颗粒尺寸和均匀性,优化其电化学性能。研究结果显示,性能最优的NVPOF的合成条件是:pH值为7.00±0.05,水热反应温度为170℃。在该条件下合成的NVPOF正极材料具有优异的电化学性能,表现为0.1C(1C=130 mA·g~(-1))的倍率下放电比容量可达123.2 mAh·g~(-1),且在20C的高倍率下仍可实现85.9 mAh·g~(-1)的比容量,在1C下循环200圈后其容量保持率为96.2%,表明该材料具有高容量、优异的倍率和循环性能。所制备的NVPOF颗粒为纳米尺度且具有很高的均匀性,可缩短Na~+的传输路径从而缩短其传输时间,且NVPOF晶体结构具有高稳定性,是一类具有高性能的钠离子电池正极材料。     

中学化学实验教学发展历程回顾及启示(下)

按照时间脉络将我国中学化学实验教学划分为4个主要阶段。第4个阶段是立足国际、迎头赶上期,伴随着新课程改革,中学化学实验教学培养理念和培养模式向国际看齐,中学化学实验教学得到了更大的发展。以发展学生“科学素养”为核心的培养理念的提出以及围绕“三维目标”课程体系的构建,促使教师的教学方式和学生的学习方式均发生了巨大的转变,信息技术的发展也使得化学实验教学课堂更加丰富多彩。化学实验教学论的建立为进一步指导教学实践发挥了重要作用。当前及今后还要加强对化学实验教学重要性的认识以及化学实验教学功能的认识。     

磷脂囊泡在胺端基和羧端基修饰金表面的沉积

磷脂囊泡与阴,阳离子性表面作用的深入理解对磷脂的生物纳米科技应用具有重要意义.通过石英电子微天平及耗散系数测量仪,研究了不同离子性磷脂囊泡在胺端基和羧端基修饰Au衬底的沉积行为.实验观察到四条囊泡沉积路径:(ⅰ)吸附至临界值后破裂成膜;(ⅱ)吸附即破裂成膜;(ⅲ)吸附不破裂;(ⅳ)不吸附.沉积路径由囊泡与衬底的双电层相互作用决定,离子可发挥调节作用.     

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根据尘埃等离子体理论,考虑到尘埃粒子的充放电过程,研究了尘埃冰晶粒子吞噬效应对极区中层电子浓度分层结构及电导率和介电常数的影响。结果表明,尘埃冰晶粒子的吞噬效应造成了极区中层80~90km高度范围内电子浓度的分层结构,并进而导致这一区域尘埃等离子体电导率、介电常数沿高度出现明显的分层,为解释和研究极区中层夏季回波现象提供参考。     

一种基于分子链统计理论的橡胶超弹性混合本构模型

橡胶材料因其独特的超弹性在实际中广泛应用,通过解析应力-应变关系可以为橡胶力学性能的工程应用提供理论指导。为了更准确地描述橡胶材料力学性能,提出一种适用于橡胶材料的超弹性混合本构模型。新模型基于Gaussian模型与八链模型,引入有关拉伸比的权重函数将二者耦合,在拉伸比较小的情况下,新模型退化成Gaussian形式,在拉伸比较大的情况下,新模型可以依靠权重函数改善八链模型在小变形区域的不足。针对取向硬化的应力-应变曲线、无取向硬化的应力-应变曲线、不同拉伸比应力-应变曲线三种力学特征曲线,从单轴拉伸、等双轴拉伸和纯剪切三类实验数据进行预测验证。结果表明,新模型同时保留了Gaussian模型在小变形范围和八链模型在大变形范围内的预测优势,且对拉伸比和应力应变曲线形式没有依赖性,均能给出高精度的预测结果,突破了Gaussian模型和八链模型的使用限制,为橡胶超弹性力学性能的预测提供了新的思路。     

Chloride anion-induced dimer capsule based on a polyfluorinated macrocycle meta-WreathArene

[1_n]metacyclophanes are a class of important building blocks for supramolecular assembly of artificial capsules. Herein we present the preparation and properties of a novel polyfluorinated macrocycle meta-WreathArene, a C₂-symmetrical [1₄]metacyclophane. Adopting a cone conformation in acetone solution, the macrocycle can form dimer capsules through hydrogen bonds induced by chloride anions. Each dimer capsule consists of two meta-WreathArene and two chloride anions, and has been unambiguously characterized both in solution and in solid state.     

Efficient gene transfection of suspension cells by highly branched poly(β-amino ester)

Suspension cells play a crucial role in many biological processes. However, compared to adherent cells, it is particularly challenging to introduce exogenous genes into suspension cells to regulate their biological functions with non-viral gene vectors, mainly due to the low cellular uptake and endosomal escape of polyplexes. Herein, to improve the interactions of polyplexes with cellular membranes, we design and synthesize highly branched poly(β-amino ester) (HPAE) via an “A2 + B4 + C2” Michael addition strategy. Results show that branching significantly increases DNA condensation of HPAE, cellular uptake and endosomal escape of HPAE/DNA polyplexes. In mast cells (MCs), HPAE exhibits up to 80-fold higher gene transfection efficiency compared to the corresponding linear poly(β-amino ester) (LPAE) and the leading commercial gene transfection reagents PEI25k, jetPEI, and Lipofectamine 3000, without causing obvious cytotoxicity. Our study establishes a reliable non-viral platform for efficient gene transfection of suspension cells.     

Solving the initial condition of the string relaxation equation of the string model for glass transition:part-Ⅱ

The string model for the glass transition can quantitatively describe the universal α-relaxation in glassformers. The string relaxation equation (SRE) of the model simplifies the well-known Debye and Rouse--Zimm relaxation equations at high and low enough temperatures, respectively. However, its initial condition, necessary to the further model predictions of glassy dynamics, has not been solved. In this paper, the general initial condition of the SRE for stochastically spatially configurative strings is solved exactly based on the obtained special initial condition of the SRE for straight strings in a previous paper (J. L. Zhang et al. 2010 Chin. Phys. B 19, 056403).     

Simulations of the flipping images and microparameters of molecular orientations in liquids according to molecule string model

The relaxation dynamics of liquids is one of the fundamental problems in liquid physics, and it is also one of the key issues to understand the glass transition mechanism. It will undoubtedly give enlightenments on understanding and calculating the relaxation dynamics if the molecular orientation flipping images and relevant microparameters of liquids are studied. In this paper, we first give five microparameters to describe the individual molecular string (MS) relaxation based on the dynamical Hamiltonian of the MS model, and then simulate the images of individual MS ensemble, at the same time calculate the parameters of the equilibrium state. The results show that the main molecular orientation flipping image in liquids (including supercooled liquid) is similar to the random walk. In addition, two pairs of the parameters are equal, and one can be ignored compared with the other. This conclusion will effectively reduce the difficulties in calculating the individual MS relaxation based on the single-molecule orientation flipping rate of general Glauber type, and the computer simulation time of interaction MS relaxation. Moreover, the conclusion has no doubt of the reference significance for solving and simulating the multi-state MS model.     

Kinetic Modelling of Atmospheric Pressure Corona Discharges in Humid Air

Corona discharge is a self-sustained discharge of gaseous medium in inhomogeneous electric fields, which often occurs on transmission lines and has some adverse effect on the power transmission system. In this paper, a kinetic model of corona discharges is presented to simulate the evolution process of charged particles and neutral species in humid air. To investigate the effect of humidity, our model consists of 69 species and 393 chemical reactions which consider important reactions containing H₂O molecules and hydrates. In addition, CO₂ molecules are also included to improve the integrity of reaction database. A temporal evolution of reduced electric field strengths E/N, which are typical experimental values of corona discharges, is used as input. The simulation results show that H₃O⁺ is one of the dominant positive ions which is in qualitative agreement with previous experimental results. The effect of humidity and pulse width on the plasma chemistry is also discussed. It is found that the humidity affects the maximum density and life time of the specific species. Meanwhile, the plasma chemistry could be affected by different pulse widths of the input electric field.