混合条件对环氧有机土纳米复合材料插层剥离行为及性能的影响

采用X 射线衍射仪、透射电镜 (TEM )研究了混合条件 ,即混合温度和时间 ,对环氧 /16 烷基胺有机蒙脱土体系在固化前的混合物以及加入固化剂、促进剂固化后有机土的插层与剥离行为的影响 .同时采用拉伸试验机、冲击试验机和热机械分析仪测定了插层与剥离型纳米复合材料的物理力学性能 .从X 射线衍射看出 ,有机土很容易在混合过程被环氧所插层 .混合物经固化后可以形成插层型或剥离型纳米复合材料 .存在一个混合温度 时间 插层剥离转变的 3 T图 .只有在一定的混合条件的区域内才能形成剥离型纳米复合材料 .剥离型比插层型纳米复合材料具有较高的力学性能     

苯并噁嗪中间体/蛭石插层纳米复合物热固化行为的研究

通过对双酚A型苯并嗪中间体 (BOZ A) 蛭石插层纳米复合物固化过程的分析表明长链烷基铵阳离子对BOZ A的热开环聚合反应没有表现出催化作用 ,也不影响纳米复合物的结构形态 .不同蛭石含量的插层纳米复合物 ,在形成不同纳米分散状态的纳米复合物的过程中 ,蛭石晶片对BOZ A的热开环聚合具有明显不同的阻碍作用 ,蛭石含量为 3%的插层纳米复合物 16 0℃的凝胶化时间较纯树脂延长约 7min ,活化能升高约8kJ mol,固化反应热焓降低约 14J g ,使得固化物的固化程度较纯树脂降低约 7%～ 10 % ,阻碍作用最大 ,其它含量的次之     

两性纳米复合高吸水性树脂的结构与性能

通过丙烯酸钠、阳离子单体丙烯酰氧乙基三甲基氯化铵(DAC)与钠蒙脱土原位溶液聚合成功地制备了具有插层结构的两性纳米复合高吸水性树脂. 其吸水性树脂吸水倍率和凝胶的抗压强度相对于聚丙烯酸钠基质均有较大提高. 吸水倍率最高可达2 380 g/g, 而凝胶的抗压强度提高到基质的180%左右. 由于复合材料结构上具有两性基团, 表现出对环境pH值特殊的应答性. 同时, 阳离子单体DAC的加入影响体系纳米结构的形成.     

插层聚合制备粘土/环氧树脂纳米复合材料过程中粘土剥离行为的研究

用ＸＲＤ、ＤＳＣ 等手段研究了有机蒙脱土在环氧树脂中的插层与剥离行为,证明环氧树脂容易插层到粘土片层间,形成稳定的插层混合物,加入胺固化剂固化后,粘土被剥离而得到剥离型纳米复合材料,剥离程度与所采用的固化温度关系不大,主要取决于固化程度,全部剥离的时间与环氧树脂凝胶的时间接近．     

有机-无机纳米复合水凝胶*

本文综述了近年来有机-无机纳米复合水凝胶领域的研究进展。针对无机成分的不同种类及复合形式,本文将目前已见报道的有机-无机纳米复合水凝胶划分为三类,分别为层状硅酸盐纳米插层复合水凝胶、粘土交联纳米复合水凝胶和二氧化硅纳米杂化复合水凝胶。阐述了三类纳米复合水凝胶的发展趋势,特别就它们的合成方法进行了详细归纳与总结。在此基础上,介绍了纳米无机成分对复合水凝胶的性能增强机理,并就三者之间的增强差异进行了说明。     

烷基紫精/五氧化二钒插层化合物的组装、表征及磁性的研究

以烷基紫精(alkylviologens; 又称紫精或紫罗精)为有机客体、层状五氧化二钒为无机主体, 在液、固两相反应体系中, 利用I^－与V^5＋的氧化还原反应, 使烷基紫精阳离子通过静电引力作用进入被还原的五氧化二钒层板之间, 形成一系列新颖的无机-有机插层化合物. 并运用X射线粉末衍射(XRD)、红外(FT-IR)、X射线光电子能谱(XPS)、紫外-可见漫反射(UV-vis DRS)等方法对其进行了表征. XRD分析结果证明, 五氧化二钒的层间距随着烷基紫精中烷基链的增长而增大, 但其结晶度随着烷基紫精阳离子中烷基链的增加而降低. XPS研究表明, 该类材料中的钒是以V^4＋和V^5＋两种混合价态存在, 氧原子处于三种不同的化学环境, 这些现象说明烷基紫精阳离子的引入对五氧化二钒的骨架结构影响不大, 主体五氧化二钒的层状结构保存完好; 氮原子处于两种不同的化学环境, 证实插层化合物中主客体之间相互修饰的协同效应, 有可能起到了稳定客体分子激发态的作用, 同时FT-IR光谱中芳香环特征谱带强度的变化也进一步证明了这一结论. UV-vis DRS分析发现由于主客体的相互作用使插层化合物在紫外和可见光区域产生特殊的光吸收性质. 从磁性研究的结果可以看出, 在温度低于15 K时, 插层化合物RV2为反铁磁性的有序结构; 当温度高于15 K时, 转变为顺磁性, 表现出磁无序结构.     

静电自组装聚电解质/有机染料插层蒙脱土光致变色纳米复合膜

从构筑静电自组装聚电解质／有机染料插层蒙脱土光致变色纳米复合膜所必需 的基本纳米构件--有机染料插层蒙脱土光致变色纳米复合物的设计出发，制备了具有光致 变色功能的蒙脱土／阳离子偶氮染料（GTL）均插层纳米复合物现，插人蒙脱土层 间的GTL热稳定性大幅度提高．由于GTL在纳米受限空间的超分子有序结构共轭，使 偶氮基发生了高达91 nm的显著红移．使用该插层纳米复合物构件与阳离子聚电解 质（PDAC）通过静电自组装得到了生长均匀、排列规整有序的光致变色聚电解质／ 阳离子偶氮染料插层蒙脱土纳米复合膜.     

气凝胶材料的研究进展及其在航空航天领域的应用

气凝胶材料是由聚合物分子链或纳米粒子组成的一种三维纳米骨架结构的多孔材料,它具有低密度、高孔体积、高孔隙率和大比表面积等结构特点,表现出优异的光、热、声、电和力学等特性.气凝胶这种轻质材料能够很好地代替金属材料,在隔热保温、电磁屏蔽、能量储存和基体骨架等航空航天领域具有广泛的应用前景.本文介绍了气凝胶最新研究进展及其在...     

新型力学性能增强二氧化硅气凝胶块体隔热材料

作为一种轻质和超高孔隙率的三维纳米多孔材料,二氧化硅气凝胶具有极低的常温导热系数,成为理想的纳米多孔超级隔热材料。然而,二氧化硅气凝胶的力学性能很差,且常压干燥制备的气凝胶整体性较差,这些都极大地限制了二氧化硅气凝胶的实际应用。近年来,通过复合或交联的方法制备得到的新型二氧化硅气凝胶,在一定程度上提高了其整体性、强度和柔韧性,使得二氧化硅气凝胶作为单独的块体材料应用成为可能。本文简要介绍二氧化硅气凝胶的多孔结构、基本性质和隔热原理,并对纤维增强、聚合物交联和其他复合二氧化硅气凝胶作为块体隔热材料的研究现状进行重点综述。最后,总结了该领域存在的关键问题,并提出未来的研究方向。     

剥离型硅橡胶/黏土纳米复合材料研究

利用层状硅酸盐制备有机 无机纳米复合材料是当前人们研究的热点[1,2 ] ,这类材料具有较常规聚合物 无机填料复合材料无法比拟的优点 ,可以明显改善高分子材料的物理机械性能、热稳定性、气体阻隔性、阻燃性、导电性、光学性等 .一般来说 ,聚合物 层状硅酸盐 (Ｐｏｌｙｍｅｒｌａｙｅｒｅｄｓｉｌｉｃａｔｅ ,ＰＬＳ)纳米复合材料可分为插层型和剥离型两种类型 .插层型纳米复合材料即聚合物插入到硅酸盐层中 ,硅酸盐在近程仍保持原有的有序晶体结构 ,在远程则是无序的 .对弹性体而言 ,硅酸盐含量在插层型杂化材料中的含量比较高 ,力学性能…     

Enhancement of intercalation properties of V2O5 film by TiO2 addition

Although it is well-known that TiO2 incorporation can greatly improve the cyclic stability of V2O5, the influences of TiO2 addition on the Li+ intercalation properties of V2O5 remain an issue of debate in literature. In this paper, we report on a systematic investigation of the preparation and intercalation properties of V2O5-TiO2 mixture films. The present work demonstrates that high Li+ intercalation rates and capacity in V2O5 films are achievable with TiO2 addition. For example, the addition of 20 mol % Ti into V2O5 polycrystalline demonstrated an approximated 100% improvement in Li+ intercalation performance as compared to single V2O5 electrodes. Such enhancement in intercalation properties of V2O5 films with TiO2 addition was attributed to changes in microstructure, crystallinity, and also a possible lattice structure and interaction force between adjacent layers in V2O5.     

Ni-V2O5.nH2O core-shell nanocable arrays for enhanced electrochemical intercalation

We have prepared Ni-V(2)O(5).nH(2)O core-shell nanocable arrays for Li(+) intercalation applications. Ni-V(2)O(5).nH(2)O nanocables were prepared via formation of Ni nanorod arrays through the template based electrochemical deposition, followed by coating of V(2)O(5).nH(2)O on Ni nanorods through electrophoretic deposition. Transmission electron microscopy (TEM) micrograph clearly shows the Ni core was covered completely by a V(2)O(5).nH(2)O shell. Electrochemical analysis demonstrates that in a current density of 1.6 A/g, the Li(+) intercalation capacity of Ni-V(2)O(5).nH(2)O nanocable array is approximately 10 times higher than that of single-crystal V(2)O(5) nanorod array and 20 times higher than that of sol-gel-derived V(2)O(5) film. Both energy density and power density of such nanocable-array electrodes are higher than the V(2)O(5) film electrode by at least 1 order of magnitude. Such significant improvement in electrochemical performance is due to the large surface area and short diffusion path offered by the nanostructured V(2)O(5).nH(2)O.     

V2O5-anchored carbon nanotubes for enhanced electrochemical energy storage

Functionalized multiwalled carbon nanotubes (CNTs) are coated with a 4-5 nm thin layer of V(2)O(5) by controlled hydrolysis of vanadium alkoxide. The resulting V(2)O(5)/CNT composite has been investigated for electrochemical activity with lithium ion, and the capacity value shows both faradaic and capacitive (nonfaradaic) contributions. At high rate (1 C), the capacitive behavior dominates the intercalation as 2/3 of the overall capacity value out of 2700 C/g is capacitive, while the remaining is due to Li-ion intercalation. These numbers are in agreement with the Trasatti plots and are corroborated by X-ray photoelectron spectroscopy (XPS) studies on the V(2)O(5)/CNTs electrode, which show 85% of vanadium in the +4 oxidation state after the discharge at 1 C rate. The cumulative high-capacity value is attributed to the unique property of the nano V(2)O(5)/CNTs composite, which provides a short diffusion path for Li(+)-ions and an easy access to vanadium redox centers besides the high conductivity of CNTs. The composite architecture exhibits both high power density and high energy density, stressing the benefits of using carbon substrates to design high performance supercapacitor electrodes.     

Synthesis and electrochemical properties of vanadium pentoxide nanotube arrays

Nanotube arrays of amorphous vanadium pentoxide (V(2)O(5)) were synthesized via template-based electrodeposition, and its electrochemical properties were investigated for Li-ion intercalation applications. The nanotubes have a length of 10 microm, outer diameter of 200 nm and inner diameter of 100 nm. Electrochemical analyses demonstrate that the V(2)O(5) nanotube array delivers a high initial capacity of 300 mAh/g, about twice that of the electrochemically prepared V(2)O(5) film. Although the V(2)O(5) nanotube array shows a more drastic degradation than the film under electrochemical redox cycles, the nanotube array reaches a stabilized capacity of 160 mAh/g, which remains about 1.3 times the stabilized capacity of the film.     

层状钒青铜纳米片的制备及其锂离子电池阳极材料性能

室温下, 在水溶液中将铵根离子和水分子插入到商用V₂O₅纳米颗粒的层间, 制得了层状的钒青 铜[(NH₄)₂V₆O₁₆·H₂O]纳米片. 该纳米片的尺寸为2~10 μm, 厚度为50~250 nm. 与商用V₂O₅纳米颗粒相比, (NH₄)₂V₆O₁₆·H₂O纳米片用作锂离子电池(LIBs)的阳极材料时, 其性能得到较大提升, 包括大的可逆放电容量 (0.1 A/g时为1148 mA·h/g)、 出色的循环性能(循环70圈后在0.1 A/g时具有1002 mA·h/g的高容量)和高倍率性能(在0.1 A/g时具有1070 mA·h/g的可逆性能). 研究结果表明, (NH₄)₂V₆O₁₆·H₂O纳米片可以作为锂离子电池优良的阳极材料, 也有望应用于其它(如钠离子电池和锌离子电池等)可再充电电池.     

Synthesis and Characterization of Self-Assembled V2O5 Mesostructures Intercalated by Polyaniline

A new nanocomposite of vanadium pentoxide (V2O5) and polyaniline (PANI) were synthesized by in situ oxidative polymerization/intercalation on V2O5 powder at room temperature. The reaction was facile and topotactic, forming polyaniline as the emeraldine salt. It was indicated that V2O5 itself can catalyze the oxidative polymerization of aniline and that layered structure could make aniline intercalate into the V2O5 framework. It makes the in situ polymerization feasible to occur in the layer of V2O5 structure. XRD results showed PANI/V2O5 nanocomposite possessed lamellar mesostructure, which was determined by an X-ray diffraction peak at 6.5° and SEM photograph. And FT-IR spectrum suggested that there was interaction between PANI and V2O5. The hybrid had better thermal stability in N2 and air ambience.     

Vanadium oxide intercalated with polyelectrolytes: novel layered hybrids with anion exchange properties

Novel anion exchange hybrid materials were developed by the insertion of poly(diallymethylammonium chloride) (PDDACl) and poly(allylamine hydrochloride) (PAHCl) polyelectrolytes into V(2)O(5) interlayer spaces using hydrothermal treatment and were used to host an anionic cyanine dye. A systematic study of the hybrid material synthesis by direct in situ reaction of PDDACl and PAHCl polycations with V(2)O(5) powders showed that the interlayer space of V(2)O(5) expands from 0.44 nm to 1.40 nm and 1.80 nm upon intercalation of PDDACl and PAHCl polyelectrolytes, respectively. X-ray photoelectron spectroscopy and DR UV-Vis-NIR spectroscopy revealed that some V(5+) sites were reduced to V(4+) during the intercalation of the polyelectrolytes, these acted as both charge balancing entities for the negative oxide sheets and carriers for exchange sites located in the V(2)O(5) interlayer space. The interlayer separation is consistent with the existence of coiled conformation of the polycations. The hybrid materials produced [PDDACl](0.24)[PDDA](0.29)V(2)O(5) and [PAHCl](0.28)[PAH](0.47)V(2)O(5), exhibited approximately 45.0% and 37.0% of chloride ions still available for anionic exchange, respectively. These materials were used to encapsulate a cyanine anionic dye. The presence of the dye was evidenced in the [PDDACl](0.24)[PDDA](0.29)V(2)O(5) by significant fluorescence, with emission peak centered at 617 nm.     

Theoretical and experimental determination of the electronic structure of V(2)O(5), reduced V(2)O(5-x) and sodium intercalated NaV(2)O(5)

In this work the electronic structure of V(2)O(5), reduced V(2)O(5-x) (V(16)O(39)) and sodium intercalated NaV(2)O(5) has been studied by both theoretical and experimental methods. Theoretical band structure calculations have been performed using density functional methods (DFT). We have investigated the electron density distribution of the valence states, the total density of states (total DOS) and the partial valence band density of states (PVBDOS). Experimentally, amorphous V(2)O(5) thin films have been prepared by physical vapour deposition (PVD) on freshly cleaved highly oriented pyrolytic graphite (HOPG) substrates at room temperature with an initial oxygen understoichiometry of about 4%, resulting in a net stoichiometry of V(2)O(4.8). These films have been intercalated by sodium using vacuum deposition with subsequent spontaneous intercalation (NaV(2)O(5)) at room temperature. Resonant V3p-V3d photoelectron spectroscopy (ResPES) experiments have been performed to determine the PVBDOS focusing on the calculation of occupation numbers and the determination of effective oxidation state, reflecting ionicity and covalency of the V-O bonds. Using X-ray absorption near edge spectra (XANES) an attempt is made to visualize the changes in the unoccupied DOS due to sodium intercalation. For comparison measurements on nearly stoichiometric V(2)O(5) single crystals have been performed. The experimental data for the freshly cleaved and only marginally reduced V(2)O(5) single crystals and the NaV(2)O(5) results are in good agreement with the calculated values. The ResPES results for V(2)O(4.8) agree in principle with the calculations, but the trends in the change of the ionicity differ between experiment and theory. Experimentally we find partly occupied V 3d states above the oxygen 2p-like states and a band gap between these and the unoccupied states. In theory one finds this occupation scheme assuming oxygen vacancies in V(2)O(5) and by performing a spin-polarized calculation of an antiferromagnetic ordered NaV(2)O(5.).     

长链烷胺及手性钛的螯合物Ti[(OC2H4)3N][OCH(CH3)2]在层状V2O5中的插层行为

用一种简便快速方法合成了一系列长链有机胺插层V₂O₅化合物. 用粉末X射线衍射(XRD)、红外光谱(FT-IR)、漫反射紫外-可见光谱(DR UV-VIS)等手段对插层产品的结构进行了表征. 除了正十六胺插层V₂O₅产品外, 其它长链烷胺插层V₂O₅产品的层间距d₀₀₁与长链烷胺碳数n之间具有良好的线性关系: d₀₀₁＝0.160n_C＋0.731 nm. 正十六胺与V₂O₅反应后生成两个插层相, 一个相的层间距d₀₀₁为4.01 nm, 另一相的d₀₀₁为3.20 nm. 此外, 研究了手性钛的螯合物Ti[(OC₂H₄)₃N][OCH(CH₃)₂] (记为TEAIP)在V₂O₅层间的插层行为, 得到相应的插层产品.     

Dependence of electrochemical properties of vanadium oxide films on their nano- and microstructures

Platelet- and fibrillar-structured V2O5 films have been prepared by solution methods, and their electrochemical Li+ intercalation properties have been studied. Platelet film consists of 20-30 nm sized V2O5 particles with random orientation, whereas fibrillar film is comprised of randomly oriented fibers though most of them protrude from the substrate surface. These platelet- and fibrillar-structured films exhibit relatively larger surface area and shorter diffusion path for Li+ intercalation than plain thin film structure. The processing methods, the discharge capacity, and cyclic performance of these films are compared with those of the conventional plain structured film.