Preparation and Structural Investigation of CuCl_2 Graphite Intercalation Compounds

Superfine graphite powder was prepared by ball-milling exfoliated graphite containing anhydrous CuCl2 in planetary ball milling systems. Nano-scale CuCl2 graphite intercalation compounds were synthesized by heating a mixture of anhydrous CuCl2 and graphite nanosheets. Scanning electron microscopy, energy-dispersive X-ray spectroscopy and high-resolution transmission electron microscopy were performed to characterize the microstructures of stage-1 nano-scale CuCl2 graphite intercalation compounds. The structure and components of the domain wall and core in the nano-scale CuCl2 graphite intercalation compounds are described. The results show that the content of CuCl2 in the mixture plays a crucial role in the size of the nano-scale CuCl2 graphite intercalation compound.

Electrical Properties of Expanded Graphite Intercalation Compounds

The intercalation compounds of CuCl2 were synthesized with expanded graphite, whose magnitude of the electrical conductivity is about 10(3)S(.)cm(-1). Their electrical conductivity is 3 similar to6 times as high as that of the expanded graphite, and about 10 times as high as that of GIC made of the non-expanded graphite. The microanalysis results of chemical compounds by X-ray energy spectrum scanning of TEM testified that the atomic ratio of chloride and cupric is nonstoichoimetric. The multivalence and exchange of electrovalence of the cupric ion was confirmed by the XPS-ESCA. Vacancy of chlorine anion increases the concentration of charge carrier. The special stage structure, made of graphite and chloride, produces a weak chemical bond belt and provides a carrier space in the direction of GIC layer. These factors develop the electrical properties.

Synthesis of NdCl_3-FeCl_3-Graphite Intercalation Compounds

NdCl3-FeCl3-graphite intercalation compounds were synthesized by means of molten salt-exchange method.Their layer structure and the relative content of the elements were investigated by X-ray diffraction, scanning electronmicroscopy and energy dispersive X-ray spectroscopy. The results show that the products are mixtures of 2, 3,4-stages,among them, the c-axis repeat distance, Ic, of stage-3 NdCl3-GIC is 1. 6536±0. 0024 nm. In addition, the mechanismof RECl3 intercalation reaction was discussed.

Study of NdCl_3-FeCl_3-Graphite Intercalation Compounds by X-Ray Photoelectron Spectroscopy

NdCl 3 FeCl 3 graphite intercalation compounds were synthesized by molten salt exchange method. The state of the intercalates and the relative contents of Nd, Fe, Cl, C in the product were determined by X ray photoelectron spectroscopy(XPS). From the XPS data, it is concluded that the binding energy of Fe2p electrons is about 711 20～710 3 eV, the binding energy of Nd3d electrons is about 983 08～983 20 eV, and Fe in the product has two valence states (Fe 3+ and Fe 2+ ).

Electronic Effect of Carbon Support on Pt Catalyst Supported on Graphite Intercalation Compound

Graphite intercalation compounds（GIC） were tested as an experimental model for studying the electronic effect of carbon support on the catalytic activity and poisoning tolerance of Pt catalyst for direct methanol fuel cells. The GIC samples with different intercalation degrees were prepared by electrolyzing graphite flake in H2SO4 for varying the periods of time. The GIC-supported Pt catalyst was deposited electrochemically. The catalytic activity and poisoning tolerance of the GIC-supported Pt catalysts were evaluated. It was found that GIC with sulfate anion as intercalate was able to catalyze methanol electrooxidation, which could be related to the positive charges generated on the graphite layer upon intercalation. As intercalation degree increased, the catalytic activity of the GIC-supported Pt catalyst decreased while the poisoning tolerance improved. This suggests that electron donation from support to catalyst had great effect on both catalytic activity and poisoning tolerance of Pt catalyst. And intercalation can be adopted as another important way to make modification on carboneous catalyst support.

STUDY ON THE MICROSTRUCTURE OF Fe-KCI GRAPHITE INTERCALATION COMPOUND

The intercalatants presence of Fe-KCl graphite intercalation compound (Fe-KCl G/C) is in the form of independent crystalline phase. In this paper, its distribution in the carbon interlayer, crystalline status and powder sizes have been studied by X-ray diffraction (XRD) , small angle X-ray scattering (SAXS) and transmission electron microscope (TEM). And the partial crystal structure of the GIC has been researched too.

A PRELIMINARY STUDY ON THE STABILITY OF TERNARY CoCl_2-FeCi_3 GRAPHITE INTERCALATION COMPOUNDS

The ternary CoCl2-FeCl3 graphite intercalation compounds (CoCl2-FeCl3 G/C) have been subjected to different treatments in various media. It is found that the CoCl2-FeCl3 GIC is stable 'when it is stored under conditions of opening to at-mosphere,whereas,acids,NaOH,boiling water,and heat treat-ments have different effects on the stability of the CoCl2-FeCl3 G/C.

Doping inhomogeneity and staging of ultra-thin graphite intercalation compound flakes probed by visible and near-infrared Raman spectroscopy

When ultra-thin graphite intercalation compounds（GICs） are deposited on the SiO2/Si substrate, it is found that their colors are dependent on the thickness of GIC flakes. The sample colors of ultrathin GIC flakes can no longer provide qualitative information on the stage index. Here, multi-wavelength Raman spectroscopy is thus applied to study the doping inhomogeneity and staging of ultra-thin GICs by FeCl3 intercalation. The G band intensity of stage-1 GIC flakes is strongly enhanced by 532-nm laser excitation, while that of stage-2 and stage-3 flakes exhibits strong intensity enhancement for 785-nm laser excitation. The near-infrared lasers are suggested to probe the doping inhomogeneity and staging of ultra-thin GIC flakes.

Electrochemically triggered decoupled transport behaviors in intercalated graphite:From energy storage to enhanced electromagnetic applications

Pyrolytic graphite (PG) with highly aligned graphene layers,present anisotropic electrical and thermal transport behavior,which is attractive in electronic,electrocatalyst and energy storage.Such pristine PG could meeting the limit of electrical conductivity (~2.5×10^(4) S·cm^(−1)),although efforts have been made for achieving high-purity sp^(2) hybridized carbon.For manipulating the electrical conductivity of PG,a facile and efficient electrochemical strategy is demonstrated to enhance electrical transport ability via reversible intercalation/de-intercalation of AlCl_(4)^(-)into the graphitic interlayers.With the stage evolution at different voltages,variable electrical and thermal transport behaviors could be achieved via controlling AlCl_(4)^(-)concentrations in the PG because of substantial variation in the electronic density of states.Such evolution leads to decoupled electrical and thermal transport (opposite variation trend) in the in-plane and out-of-plane directions,and the in-plane electrical conductivity of the pristine PG (1.25×10^(4) S·cm^(−1)) could be massively promoted to 4.09×10^(4) S·cm(AlCl_(4)^(-)intercalated PG),much better than the pristine bulk graphitic papers used for the electrical transport and electromagnetic shielding.The fundamental mechanism of decoupled transport feature and electrochemical strategy here could be extended into other anisotropic conductive bulks for achieving unusual behaviors.

Composites on Base of the Ultradispersed Polytetrafluoroethylene and Graphite Oxide Intercalated Compounds

Composites based on ultradispersed polytetrafluoroethylene and intercalated graphite oxide compounds with dodecahydro-closo-dodecaborates and methods of their fabrication have been developed. The fabricated composites have been characterized using XRD analysis, and optical microscopy. These composites are distinguished with completeness of their combustion, since the combustion products comprise gaseous boron fluorine-containing compounds of boron, boron trifluoride (BF3), and boron oxyfluoride ((BOF)3). Besides, these composites are characterized with increased energy capacity as compared to purely oxygen-containing compounds, since the heat of formation of boron fluorine-containing compounds is higher than that of boron oxide. Introduction of ultradispersed polytetrafluoroethylene imparts composites with hydrophobicity, thus improving their functioning properties.

Localized-domains staging structure and evolution in lithiated graphite

Intercalation provides to the host materials a means for controlled variation of many physical/chemical properties and dominates the reactions in metal‐ion batteries.Of particular interest is the graphite intercalation compounds with intriguing staging structures,which however are still unclear,especially in their nanostructure and dynamic transition mechanism.Herein,the nature of the staging structure and evolution of the lithium(Li)‐intercalated graphite was revealed by cryogenic‐transmission electron microscopy and other methods at the nanoscale.The intercalated Li‐ions distribute unevenly,generating local stress and dislocations in the graphitic structure.Each staging compound is found macroscopically ordered but microscopically inhomogeneous,exhibiting a localized‐domains structural model.Our findings uncover the correlation between the long‐range ordered structure and short‐range domains,refresh the insights on the staging structure and transition of Li‐intercalated/deintercalated graphite,and provide effective ways to enhance the reaction kinetic in rechargeable batteries by defect engineering.

Synthesis and Characterization of Exfoliated Graphite/ABS Composites

Exfoliated graphite was prepared by chemical route and then further subjected to thermal oxidation and sonication for size reduction and increased interlayer spacing in natural flake graphite. Exfoliated graphite/ABS composites were pre-pared with varying filler concentration by solution casting method. Exfoliated graphite and composites were character-ised by scanning electron microscopy and energy dispersive X-ray analysis, Fourier transform infrared spectroscopy and X-ray diffractometry techniques. After thermal exfoliation significant peak of graphite at 2? = 26.4? disappeared completely, confirming successful exfoliation of graphite. SEM images revealed homogeneous dispersion of exfoliated graphite in the matrix and EDAX confirmed successful reduction of graphite oxide.

Characteristics and Microstructure of Graphite Encapsulated Iron Nanoparticles

The graphite encapsulated a-Fe particles were prepared by reduction of stage-2 and stage-3 FeCI3 graphite intercalation compounds （GICs） with metallic potassium, X-ray diffraction analysis （XRD）, energy dispersive X-ray spectroscopy （EDS） investigation and transmission electron microscopy （TEM） observation show that the reduction products of stage-2 FeCl3-GICs contains more abundant a-Fe nanoparticles than those of stage-3. High-resolution TEM （HRTEM） observation reveals that the nanoparticle of a-Fe was polycrystals or twins, which was real or quasi two-dimension in shape, and whose space orientation was strictly controlled by the graphene. Based on the experiment results, a possible growth model of the graphite encapsulated ct-Fe was proposed.

Preparation and microwave absorption properties of FeNi/graphite nanocomposites

FeNi/graphite nanocomposites were prepared by reducing FeCl3-NiCl2-GICs in H2. The elemental composition,structure,magnetic and microwave absorption of FeNi/graphite nanocomposites were investigated using X-ray diffraction,energy dispersive spectra,hysteresis loop and electromagnetic parameter analysis. The results show that with the increase of the reduced temperature,the number and size of particles of FeNi increases,and the FeNi /graphite nanocomposites changes to soft magnetism. FeNi /graphite nanocomposites bear microwave absorption properties. With the increase of the thickness of the sample,the matching frequency tends to shift to the low frequency region,and theoretical reflection loss becomes less at the matching frequency. Microwave absorption property in the low frequency region of FeNi/graphite nanocomposites prepared at 600 ℃(FeNi/C600) is the best. When the thickness is 2 mm,the maximum theoretical reflection loss of FeNi/C600 is-4.3 dB and the matching frequency is 3.5 GHz.

Intercalation behavior of spiro-bipyrrolidinium cation into graphite electrodes from ethylene carbonate

The intercalation behavior of spiro-(1,1)-bipyrrolidinium cation(SBP+) into graphite electrode from spiro-(1,1)-bipyrrolidinium tetrafluoroborate-ethylene carbonate(SBPBF4-EC) solutions is investigated by conventional electrochemical tests and in situ X-ray diffraction measurements. Two kinds of graphite intercalation compounds(GICs) with discrete characteristic intercalated gallery heights(IGHs)(ca. 0.95 and0.75 nm) can be obtained with varying the salt concentration. The effect of graphite type is also addressed.

Improving the cycle stability of FeCl3-graphite intercalation compounds by polar Fe2O3 trapping in lithium-ion batteries

FeCI3-intercalated graphite intercalation compounds (GICs) with high reversible capacity and high volumetric energy density are attractive anode material alternatives of commercial graphite. However, the rapid capacity decay, which was induced by chloride dissolution and shuttling issues, hindered their practical application. To address this problem, here, we introduce flake-like Fe2O3 species with inherently polar surface on the edge of FeCl3 -intercalated GICs through microwave-assisted transformation of a fraction of FeCl3 component. Theoretical simulations and physical/electrochemical studies demonstrate that the introduced Fe2O3 component can afford sufficient polar active sites for chemically bonding the soluble FeCl3 and LiCl species based on the polar-polar interaction mechanism, further inhibiting the outward diffusion of the chlorides and immobilizing them within the GIC material. In a lithium ion cell, the FeCl3 -intercalated GIC with a suitable Fe2O3 content shows remarkably improved cycling stability with a high reversible capacity of 1,041 mAh·g^-1 at a current density of 200 mA·g^-1. Capacity retention of 91 % is achieved at a high current density of 1,000 mA·g^-1 over 300 cycles. This work opens up the new prospect for immobilizing chlorides by introducing inorganic species in GIC for long-cycle electrochemical batteries.

Structure model and synthesis of NdCl_3-FeCl_3-graphite intercalation compounds

The distribution of the elements and microstructure of NdCI3-FeCI3-graphite intercalation compounds (GICs) were shown by scanning electron microscope (SEM) and energy dispersive spectroscopy (EDS). The results show that Nd element intercalates into graphite, forming NdCI3-FeCI3-GICs, and the distribution of Nd and Fe is nearly even. On the basis of the data, a structure model for RECI3-GICs was founded, and the characteristic layer distance and the index of interval energy were calculated. The calculated results agree with experimental ones, and the relative errors are ±2%. Thus it can be seen that the (111) face is optimal direction for intercalation reaction of TbCl3-LuCl3, and the (001) face is that for LaCl3-GdCl3, because of the lowest interval energy.

超微粉石墨层间化合物FeCl_3-NiCl_2-GICs的制备及电磁性能研究

以微粉石墨为主体材料合成出不同阶结构的FeCl3 NiCl2 GICs。应用XRD、SEM对产物的晶体结构与表面形貌进行分析表征。采用范德保法测量产物在常温常态下的电阻率 ,用MODEL960 0振动磁强计测量GICs在 0～ 7 95 8× 10 5A m磁场强度下的磁化强度、磁化率。测量数据表明异类原子FeCl3、NiCl2 插入石黑层间后 ,GICs的电导率增加 1 3～ 2 9倍 。

用H_2O_2-H_2SO_4合成低硫GIC的研究

采用化学氧化法在浓硫酸与双氧水混合液中合成了H2SO4-GIC ,研究了插层工艺参数如双氧水浓度、双氧水与浓硫酸的配比以及水洗液的pH值、烘干温度、膨化温度等对膨胀容积和残余硫含量的影响 ,同时也对整个插层机理进行了探讨 ,得到了制造低硫膨胀石墨的合理工艺参数。

石墨层间化合物FeCl_3-CrO_3-GIC的制备及性能研究

以天然鳞片石墨、CrO3、CH3NO2、FeCl3为原料,按物质的量的比34∶1.5∶22∶1,利用化学氧化法制备出低温易膨胀、高膨胀容积的石墨层间化合物,300℃时膨胀容积为420mL·g-1,800℃时达到最大膨胀容积630mL·g-1,明显优于传统硫酸、硝酸插层的石墨层间化合物。采用SEM、EDS、FTIR、XRD、TG、VSM等技术对石墨层间化合物的组成、结构、性能进行了表征和分析。