New trends in intercalation compounds

We review here some of the recent developments in intercalation compounds generally, with numerous examples taken from the literature on graphite intercalation compounds. Particular emphasis is given to research opportunities and new directions in this rapidly moving research field.     

从第13届国际插层化合物大会看插层化合物的最新发展趋势

2005年6月5日至9日在法国克莱蒙特-弗朗市（Clermont-Ferrand）召开了第13届国际插层化合物大会（13th International Symposium on Intercalation Compounds，ISIC13），来自23个国家的170余名学者参加了此次大会，其中国内的清华大学材料系、北京化工大学可控化学反应重点实验室、武汉理工大学材料学院等10名代表参加了该次大会。大会内容涵盖了插层化合物的合成工艺、胶体化学、材料结构与材料电磁性、电化学性能、纳米材料（包括纳米粒、纳米纤维、纳米复合材料）、插层化合物的自组装技术以及生物分子的插层化合物等七个议题，包括炭材料（富勒烯、石墨、碳纳米管），过渡金属硫族化合物、金属氢氧化物、陶瓷及改性陶瓷、层状金属氧化物及氢氧化物、沸石及磷酸盐和纳米复合材料等七类材料。     

Organometallic intercalation compounds of FeOCl

The layered transition metal oxyhalide FeOCl has been found to undergo direct intercalation by the organometallic molecular compounds ferrocene and cobaltocene. From x-ray powder diffraction studies, it has been shown that the Van der Waals gap between the FeOCl layers expands by roughly 5Å to accomodate the metallocene. With either metallocene, the data accurately fit a body centered orthorhombic unit cell. A structural model consistent with the observations is proposed, based on a simple shift of alternate FeOCl layers by one-half unit cell in the [101] direction (a-c diagonal) accompanied by the interlayer expansion. There is no evidence for ordering within the metallocene layers. The intercalation of ferrocene is especially significant because its first ionization potential (6.88 eV) is substantially higher than those of organometallic compounds previously intercalated into transition metal dichalcogenides.     

Lithium intercalation in KxTi8O16 compounds

Several bronzes K_xTi₈O₁₆ have been prepared from K_1.64(1)Ti₈O₁₆ by means of oxidative reactions. These bronzes have been intercalated with lithium by electrochemical methods in order to test their performances as electrode materials in lithium rechargeable batteries. The main result is that although the maximum capacity (260 Ah kg⁻¹) is reached in the compound with the lowest potassium content, a low reversibility and high polarisation are obtained. Bronzes with intermediate potassium content are more attractive for applications in rechargeable lithium batteries. These compounds maintain an acceptable capacity (200 Ah kg⁻¹) while having high cyclability and low polarisation. The application should be addressed to anode materials rather than to cathode due to the low voltage (1.75 V) obtained during the intercalation reaction.     

Ion exchange of intercalation compounds from WOP2O7 and intercalation ofn-alkylamines

Ion exchange of Na _x WOP₂O₇ ·nH₂O (x 1.4) prepared from WOP₂O₇ was attempted, using alkaline and alkaline earth ions. The degree of exchange was observed to be >50% at 90° C except for Mg²⁺. The basal spacing of ion-exchanged materials for the hydrated phase were dependent on the number of water molecules in the interlayer spaces, while those for the dehydrated phase increased with the size of ions in the interlayer spaces. The network of water molecules linked by the hydrogen bond in the interlayer spaces seems to determine the basal spacing. By the ion-exchange reaction,n-alkylammonium ions were intercalated into the interlayer spaces of Na _x WOP₂O₇ ·nH₂O (x 1.4) and Sn _x H _y WOP₂O₇ ·nH₂O (2x +y 0.5). In spite of the difference in the charge density of the host layer, a similar arrangement of alkyl chains in the interlayer spaces resulted, and neutral amines were considered to be intercalated as well as ammonium ions. Direct reaction ofn-alkylamine with WOP₂O₇ produced an intercalation compound without reduction of tungsten. The arrangement of the amines in the interlayer spaces is similar to that supposed to the ion-exchanged derivatives when heated at 140° Cin vacuo.     

分步插层法制备硝酸盐-硫酸-GIC

通过硫酸、硝酸或硝酸盐分步插层的方法,成功制备了硝酸/硝酸盐-硫酸-GIC三元石墨层间化合物.采用XRD、SEM和EDS对GIC的结构进行了研究.结果表明:与直接插层法相比,分步插层法有利于插层物质的插层反应,充分扩大石墨层间距,形成低阶石墨层间化合物,使膨胀效果更优,膨胀体积高达450mL/g以上;膨胀后GIC的孔结构均匀,层壁较薄,片层结构清晰,膨胀充分.同时,分步插层法能够降低实验操作的危险性,污染小,反应易于控制.     

Exfoliation of graphite-CrO3 intercalation compounds in hydrogen peroxide solution

This paper deals with the reaction of the graphite-CrO₃ intercalation compounds with hydrogen peroxide. As a consequence of this reaction, the exfoliation of the compound of the solvent as well as the impregnation-dry method has been observed. The swelling of the material results in a distinct decrease in bulk density of the compounds. It has been demonstrated that the split flakes of the exfoliated compounds can be transformed into a honeycomb-like structure if the reaction takes place in a more concentrated solution of H₂O₂. X-ray analysis has revealed that in spite of a partial leaching out of CrO₃ from the structure of graphite, the intercalation compounds are still preserved. Some contributions to the mechanism of exfoliation are discussed.     

二维高频磁特性测量中关键性问题研究

为准确测量磁性材料的磁特性,提出二维磁特性测试方法,使用新型激磁装置及传感结构,针对二维磁特性激磁装置的电磁干扰及屏蔽结构进行深入研究,设计屏蔽结构,屏蔽效能可以达到61.699d B。讨论测试过程环境中的直流干扰和工频及低频杂波对实验结果的影响等关键性问题,并提出解决方案。实验证明:所提出的解决方法是实用有效的,具有可行性。     

碳纤维作宿主的三元插层化合物研究

以高模量碳纤维作宿主，采用熔融盐法分别合成了FeCl3-ZnCl2和CuCl2一NiCl2作插层剂的三元插层化合物，由x射线衍射分析得知：前者的插层效果要优于后者。采用8mm波衰减率测试系统测试了两种产物对8mm波的衰减，结果表明：经FeCl3-ZnCl2和CuCl2-NiCl2插层的碳纤维对8mm波的衰减率分别可达8dB和6dB。     

Effects of processing parameters on the structure and amount of intercalation of copper chloride-graphite intercalation compounds

Natural graphite powders were intercalated with copper chloride using gas phase reaction in this study. The effects of intercalation temperature, time, and the amount of intercalants on the structure and the amount of intercalation were investigated. An electron probe x-ray microanalyzer (EPMA) was used to quantitatively measure the copper concentration in copper chloride-graphite intercalation compounds. Only stage 1 and stage 2 structures were found in the present processing conditions and the stage structure is mainly determined by the reaction temperature. Results of EPMA quantitative measurement indicated that the amount of intercalation increased with increasing intercalation temperature. However, the amount of intercalation was independent of the reaction time due to the small particle size of graphite host materials.     

Alloying effect on electronic structures of lithium intercalation compounds

The alloying effect on the electronic structures of spinel LiM_xMn_2−xO₄ (M=Ti, Cr, Mn, Fe, Co, Ni, Cu and Zn) has been investigated by the DV-Xα molecular orbital method. Following the addition of alloying element M, new M-3d bands in the density of states appeared additionally compared with that in pure LiMn₂O₄. As the new M-3d bands appeared, the new O-2p bands also emerged accordingly in the same positions around Fermi energy due to M–O interaction. If alloying element M leads to emergence of O-2p band in low energy position, withdrawal of Li electrons from this low O-2p band would results in high electrochemical cell voltage. The mechanism of high voltage occurrence due to alloying in lithium intercalation compounds can be attributed to the low oxygen levels near Fermi energy modified by neighbor alloying element.     

Immersed smoothed finite element method for two dimensional fluid–structure interaction problems

A novel method called immersed smoothed FEM using three‐node triangular element is proposed for two‐dimensional fluid–structure interaction (FSI) problems with largely deformable nonlinear solids placed within incompressible viscous fluid. The fluid flows are solved using the semi‐implicit characteristic‐based split method. Smoothed FEMs are employed to calculate the transient responses of solids based on explicit time integration. The fictitious fluid with two assumptions is introduced to achieve the continuous form of the FSI conditions. The discrete formulations to calculate the FSI forces are obtained in terms of the characteristic‐based split scheme, and the algorithm based on a set of fictitious fluid mesh is proposed for evaluating the FSI force exerted on the solid. The accuracy, stability, and convergence properties of immersed smoothed FEM are verified by numerical examples. Investigations on the mesh size ratio indicate that the stability is fairly independent of the wide range of the mesh size ratio. No additional volume correction is required to satisfy the incompressible constraints. Copyright © 2012 John Wiley & Sons, Ltd.     

BEM solution of two dimensional unilateral contact problems with friction by a new approach

Recently, a new numerical resolution method has been introduced for frictionless unilateral contact problems which reduces the resolution of the unilateral problem to the resolution of a nonlinear equation. This reduction is based on a reformulation of the unilateral problem, which at the same time governs the usual unknowns and extra unknowns characterising the contact zone position. The supplementary equations needed by the introduction of these extra unknowns are given by writing the contact force and the gap between the body and its support vanish simultaneously on the contact zone boundary. The boundaries of the bodies in contact are supposed regular in the contact zone vicinity. The aim of the present paper is to extend this resolution method to unilateral contact problems with Coulomb friction.     

Non-linear effects in two dimensional superfluids

We review the relationship between superfluidity, Bose condensation and vortices in two dimensional superfluids. The theory of the dynamic response of superfluid films, due to Ambegaokar et al., is reviewed and then extended to describe the non-linear response of both helium and superconducting films.     

Eddies in two dimensional stokes flow

Eddies in two dimensional Stokes flow produced by a cylinder or rotelet rotating in the presence of a fixed plane are discussed together with a rotelet interior to a cylinder which is either fixed or rotating. Free eddies are shown to exist for certain locations of the rotelet inside the cylinder.     

插层化合物在膨化过程中的热分解动力学

采用红外傅立叶变换光谱仪与热重分析仪联动装置在线检测HNO3-CH3COOH—GIC、H2SO4-GIC及H2SO4-CH3COOH—GIC等插层石墨的相变及热分解过程，同时通过快速扫描得到相应时间段内分解产物的红外光谱，并运用Kissinger—Ozawa原理计算了几种典型膨化反应的动力学参数。研究结果揭示了膨化过程的热分解机理，当升温速率在20℃／min～80℃／min范围时，由实验数据计算出膨化反应表观活化能不大于120kJ／mol。     

Synthesis and characterization of indium intercalation compounds of molybdenum sulphoselenide

The synthesis, structure and properties of indium-intercalated compounds of molybdenum sulphoselenide, In_1/3MoS_xSe_2–x (0x 2) compounds were investigated. X-ray analysis shows that all these compounds possess layer-type structure with hexagonal symmetry. Studies of room-temperature magnetic susceptibility, thermoelectric power experiments and two-probe conductivity measurements in the temperature range 25–350 °C, confirmed that these are diamagnetic semiconductors with In_1/3MoS₂, In_1/3MoS_1.5Se_0.5 and In_1/3MoS_xSe_2–x (0x1.5) exhibiting n- and p-type conductivity, respectively. These results have been explained on the basis of existing band models. Thermal stability behaviour of these compounds in an air atmosphere and X-ray analysis of the oxidized product were also studied.