Graphite Bi-intercalation Compounds Research Articles

Dynamic scaling and aging phenomena in a short-range Ising spin glass:Cu0.5Co0.5Cl2−FeCl3graphite bi-intercalation compound

Static and dynamic behavior of short-range Ising spin glass (SG) ${\mathrm{Cu}}_{0.5}{\mathrm{Co}}_{0.5}{\mathrm{Cl}}_{2}\ensuremath{-}{\mathrm{FeCl}}_{3}$ graphite bi-intercalation compounds has been studied with superconducting quantum interference device dc and ac magnetic susceptibility. The T dependence of the zero-field relaxation time $\ensuremath{\tau}$ above a spin-freezing temperature ${T}_{g}(=3.92\ifmmode\pm\else\textpm\fi{}0.11\mathrm{K})$ is well described by critical slowing down. The absorption ${\ensuremath{\chi}}^{\ensuremath{''}}$ below ${T}_{g}$ decreases with increasing angular frequency $\ensuremath{\omega},$ which is in contrast to the case of 3D Ising spin glass. The dynamic freezing temperature ${T}_{f}(H,\ensuremath{\omega})$ at which ${\mathrm{dM}}_{\mathrm{FC}}(T,H)/dH={\ensuremath{\chi}}^{\ensuremath{'}}(T,H=0,\ensuremath{\omega})$ is determined as a function of frequency (0.01 Hz $<~\ensuremath{\omega}/2\ensuremath{\pi}<~1\mathrm{kHz})$ and magnetic field $(0<~H<~5\mathrm{kOe}).$ The dynamic scaling analysis of the relaxation time $\ensuremath{\tau}(T,H)$ defined as $\ensuremath{\tau}=1/\ensuremath{\omega}$ at ${T=T}_{f}(H,\ensuremath{\omega})$ suggests the absence of SG phase in the presence of H (at least above 100 Oe). Dynamic scaling analysis of ${\ensuremath{\chi}}^{\ensuremath{''}}(T,\ensuremath{\omega})$ and $\ensuremath{\tau}(T,H)$ near ${T}_{g}$ leads to the critical exponents $(\ensuremath{\beta}=0.36\ifmmode\pm\else\textpm\fi{}0.03,$ $\ensuremath{\gamma}=3.5\ifmmode\pm\else\textpm\fi{}0.4,$ $\ensuremath{\nu}=1.4\ifmmode\pm\else\textpm\fi{}0.2,$ $z=6.6\ifmmode\pm\else\textpm\fi{}1.2,$ $\ensuremath{\psi}=0.24\ifmmode\pm\else\textpm\fi{}0.02,$ and $\ensuremath{\theta}=0.13\ifmmode\pm\else\textpm\fi{}0.02).$ The aging phenomenon is studied through the absorption ${\ensuremath{\chi}}^{\ensuremath{''}}(\ensuremath{\omega},t)$ below ${T}_{g}.$ It obeys a $(\ensuremath{\omega}{t)}^{\ensuremath{-}{b}^{\ensuremath{''}}}$ power-law decay with an exponent ${b}^{\ensuremath{''}}\ensuremath{\approx}0.15--0.2.$ The rejuvenation effect is also observed under sufficiently large (temperature and magnetic-field) perturbations.

Raman scattering study of acceptor-acceptor-type graphite bi-intercalation compounds

Stages 4 and 5 ${\mathrm{FeCl}}_{3}$-graphite intercalation compounds (GIC's) were prepared by a two-bulb method, and were used as host materials for the synthesis of graphite bi-intercalation compounds (GBC's), where the bi-intercalated species were ICl, IBr, and ${\mathrm{SbCl}}_{5}.$ Various types of GBC's were obtained by changing the reaction temperatures, and the layer sequences were clarified by x-ray diffraction. Lattice dynamics of the resultant GBC's was investigated by Raman spectroscopy. Since the layer sequence of GBC's from a stage 4 ${\mathrm{FeCl}}_{3}\ensuremath{-}\mathrm{G}\mathrm{I}\mathrm{C}$ with one bi-intercalated layer is ${\mathrm{G}(\mathrm{F}\mathrm{e}\mathrm{C}\mathrm{l}}_{3}{)\mathrm{G}}_{1}{\mathrm{G}}_{2}{(\mathrm{I})\mathrm{G}}_{3}{\mathrm{G}}_{4}{(\mathrm{F}\mathrm{e}\mathrm{C}\mathrm{l}}_{3})\mathrm{G},$ where ${\mathrm{G}}_{n},$ $({\mathrm{FeCl}}_{3}),$ and (I) denote the $n\mathrm{th}$ graphite, ${\mathrm{FeCl}}_{3},$ and bi-intercalated layers, respectively, and all graphene layers are adjacent to an intercalate layer. The GBC's give only one Raman-active ${E}_{2g}^{(2)b}$ mode frequency in the Raman spectra although the intercalates are different. GBC's from stage 5 ${\mathrm{FeCl}}_{3}\ensuremath{-}\mathrm{G}\mathrm{I}\mathrm{C}$ with one bi-intercalated layer give the stacking sequence of ${\mathrm{G}(\mathrm{F}\mathrm{e}\mathrm{C}\mathrm{l}}_{3}{)\mathrm{G}}_{1}{\mathrm{G}}_{2}{(\mathrm{I})\mathrm{G}}_{3}{\mathrm{G}}_{4}{\mathrm{G}}_{5}{(\mathrm{F}\mathrm{e}\mathrm{C}\mathrm{l}}_{3})\mathrm{G}.$ Since two types of graphene layers, interior $({\mathrm{G}}_{4})$ and bounding $({\mathrm{G}}_{1,2,3,5})$ layers exist, two peaks identified as Raman-active ${E}_{2g}^{(2)i}$ and ${E}_{2g}^{(2)b}$ mode frequencies appear in Raman spectra. Both frequencies were affected by the bi-intercalated species. From the ${E}_{2g}^{(2)i}$ frequencies, the degree of electron affinities of the bi-intercalated layers was evaluated to be in the order of ${\mathrm{IBr}l\mathrm{ICl}l\mathrm{SbCl}}_{5}.$ For the GBC's with two bi-intercalated layers, their layer sequences were determined to be ${\mathrm{G}(\mathrm{F}\mathrm{e}\mathrm{C}\mathrm{l}}_{3}{)\mathrm{G}\mathrm{G}(\mathrm{I})\mathrm{G}(\mathrm{I})\mathrm{G}\mathrm{G}(\mathrm{F}\mathrm{e}\mathrm{C}\mathrm{l}}_{3})\mathrm{G}$ or ${\mathrm{G}(\mathrm{F}\mathrm{e}\mathrm{C}\mathrm{l}}_{3}{)\mathrm{G}\mathrm{G}(\mathrm{I})\mathrm{GG}(\mathrm{I})\mathrm{G}(\mathrm{F}\mathrm{e}\mathrm{C}\mathrm{l}}_{3})\mathrm{G}.$ In this case, only bounding layers of graphite exist. However, two peaks were observed in the Raman spectra. The difference of the Raman-active ${E}_{2g}^{(2)b}$ mode frequencies was due to the intercalate coupling effect.

Raman Scattering Study of FeCl3 Based Graphite Bi-Intercalation Compounds

FeCl3-IBr, -ICI, and -SbCl5 -graphite bi-intercalation compounds (GBC's) have been synthesized from a stage 4 FeCI3 -graphite intercalation compound (GIC). and their lattice dynamics has been investigated by Raman spectroscopy. First, layer sequences of these GBC's were determined by x-ray diffraction, and the sequence was determined to be G(FeCl3)G1G2(1)G3G4(FeCI3)G. where Gn, (FeCl3), and (1) refer to the nth graphite, FeCl3, and bi-intercalate layers, respectively. The sequences were the same irrespective of bi-intercalated species. These GBC's give only one peak identified as Raman active mode frequency in the Raman spectra. The peak frequencies were found to be affected by bi-intercalated species, and the frequencies were in the order of IBr <ICI <SbCl5. From this result, the degree of charge transfer was determined to be in the order of IBr < ICI < SbCl5.

Successive Magnetic Phase Transitions of CucCo1-cCl2-FeCl3 Graphite bi-intercalation Compounds

CucCo1-cCl2-FeCl3 graphite bi-intercalation compounds (GBIC's) have a c-axis stacking sequence of -G-I1-G-I2-G-I1-G-I2-G- (G = graphite layer, I1 = CucCo1-cCl2 layer, and I2 = FeCl3 layer). These compounds undergo magnetic phase transitions at Th, Tcu, Tcl, TSG, and TRSG (Th>Tcl>TRSG=TSG). depending on the Cu concentration. The phase transition at Th is related to a helical spin order. The phase transitions at Tcu and Tcl are associated with a spin order of CucCo1-cCl2 layers. The re-entrant spin glass phase below TRSG for c≤0.4 and the spin glass phase below TSG for c≥0.5 are due to the spin frustration effect occurring in FeCl3 layers. The nature of these phases has been studied using SQUID DC magnetization and SQUID AC magnetic susceptibility.

Synthesis, Structure and Electrochemical Reactivity of CrO3-H2SO4- Graphite Bi-Intercalation Compounds Prepared at Room Temperature

The paper deals with the synthesis, structure and electrochemical properties of CrO3-H2SO4-graphite bi-intercalation compound (CrO3-H2SO4-GBC) prepared at room temperature. In contrast to the two step process in which CrO3 is first intercalated chemically followed by electrochemical bi-intercalation of H2SO4, the method described in the paper allows the simultaneous intercalation of CrO3 and H2SO4 into graphite to give CrO3-H2SO4-GBC. The electrochemical method appeared to be suitable both to distinguish the original CrO3-H2SO4-GBCs of different structures and to enrich them with H2SO4 to provide stage-1 compound.

Synthesis and Characterization of Acceptor Type Graphite Bi-Intercalation Compounds

FeCl3-based graphite bi-intercalation compounds (GBCs) were prepared from stage 5 FeCl3-graphite intercalation compound and their formatiomechanism, stacking sequences, and lattice dynamics were studied. Bi-intercalated species were H2SO4, IBr, ICl, and SbCl5. From the stacking sequences determined by X-ray diffraction measurements, bi-intercalation processes were found to be affected by the electron affinity of bi-intercalated species. Lattice dynamics of the resultant GBCs was investigated by Raman spectroscopy. In the Raman spectra of GBCs with one bi-intercalated layer, two peaks assigned as Raman active E (2) i2g and E (2) b2g mode frequencies were obtained, and both frequencies were affected by the bi-intercalated species. Raman spectra of GBCs with two bi-intercalated species gave two E (2) b2g mode frequencies due to the double-intercalate coupling effect.

Electrochemical formation and stability of CrO3HClO4graphite bi-intercalation compounds

Abstract The present paper concerns CrO3HClO4graphite bi-intercalation compounds (CrO3 HClO4GBCs) synthesized upon the subsequent intercalation of 70 wt% HClO4 into stage-3 and stage-5 CrO3graphite intercalation compounds. On the basis of the results of the potentiodynamic and galvanostatic measurements and the XRD analysis, it has been shown that the formation of stage-1 CrO3HClO4 GBC occurs for both CrO3GICs but the overoxidation and deintercalation processes, as well as the cycling behaviour of the ternary GBCs, depend on the structure of the original CrO3GIC. In contrast to the binary HClO4GIC, which is readily deintercalated to the pure graphite upon cathodic reduction, CrO3HClO4 GBCs and the products of their overoxidation are only partially deintercalated despite cathodic reduction followed by washing with water. After such a treatment, CrO3HClO4GBCs retain the stage structure characteristic of the original CrO3GIC but surprisingly exhibit a new chemical composition. A role of the CrO3 intercalate in the mechanism of the intercalation/deintercalation reactions occurring within CrO3HClO4GBCs is discussed. The results of this work lend credence to the assumption that bi- and co-intercalation phases coexist in the product of the subsequent intercalation of HClO4 into CrO3GIC.

Bi-intercalation of ICl into a stage-5 FeCl3 graphite intercalation compound.

X-ray diffraction (XRD) has been used for the study of bi-intercalation of ICl into the stage-5 ${\mathrm{FeCl}}_{3}$ graphite intercalation compound (GIC). The stage-5 ${\mathrm{FeCl}}_{3}$ GIC is obtained when the temperature of graphite is set at 788 K, and the temperature of ${\mathrm{FeCl}}_{3}$ at 573 K in the two-zone system. Since the stage-5 ${\mathrm{FeCl}}_{3}$ GIC has four consecutive vacant galleries in the c-axis direction, the ${\mathrm{FeCl}}_{3}$-ICl graphite bi-intercalation compounds (GBC's) with one and two ICl layers are studied. When the temperature of the stage-5 ${\mathrm{FeCl}}_{3}$ GIC is held at 373 K and the temperature of ICl at 323 K, the ${\mathrm{FeCl}}_{3}$-ICl GBC with one ICl layer is obtained. The layer sequence of the GBC is found to be an admixture of G(${\mathrm{FeCl}}_{3}$)GG(ICl)GGG(${\mathrm{FeCl}}_{3}$)G and G(${\mathrm{FeCl}}_{3}$)GGG(ICl)GG(${\mathrm{FeCl}}_{3}$)G by XRD, where G, (${\mathrm{FeCl}}_{3}$), and (ICl) refer to graphite, ${\mathrm{FeCl}}_{3}$, and ICl layers, respectively. The ${\mathrm{FeCl}}_{3}$-ICl GBC with two ICl layers is prepared with the temperatures of the stage-5 ${\mathrm{FeCl}}_{3}$ GIC and ICl at 333 and 313 K, respectively. Its layer sequence is determined to be G(${\mathrm{FeCl}}_{3}$)GG(ICl)G(ICl)GG(${\mathrm{FeCl}}_{3}$)G. From the result of the layer sequence of the ${\mathrm{FeCl}}_{3}$-ICl GBC with two ICl layers, the order of the degree of the charge transfer is shown to be ${\mathrm{FeCl}}_{3}$ GIC&gt;ICl GIC.

Formation process and structure of graphite oxide

Formation process of graphite oxide has been investigated by using a modified Staudenmaier method and an electrochemical one. The modified Staudenmaier method revealed that graphite oxide is formed via stage 1 graphite bi-intercalation compounds of HNO 3 and H 2SO 4. On the other hand, the electrochemical method showed that graphite oxide is synthesized via stage 1 HClO 4 graphite intercalation compound (GIC) in 11.6 M HClO 4 solution and via stage 2 HClO 4 GIC in 9.2 M HClO 4 solution. Structure of graphite oxide was studied by fluorination of graphite oxide at 50–200°C. The main fluorination reaction is the substitution of hydroxyl group by fluorine atom. The c-axis repeat distances (I c) of fluorinated graphite oxides, prepared by both the Brodie and the modified Staudenmaier methods, were around 0.9 nm, which is close to that of stage 2 type poly(dicarbon monofluoride), ( C 2 F) n The in-plane lattice parameter a 0 of graphite oxide increased toward that of ( C 2 F) n by fluorination (0.251 nm), and decreased toward that of graphite itself by dehydration (0.246 nm). These results strongly support the ( C 2 F) n -type structure model of graphite oxide.

Bi-intercalation of H2SO4 into stages 4–6 FeCl3–graphite intercalation compounds

Stages 4–6 FeCl3–graphite intercalation compounds (GIC's) have been prepared by an ordinary two-bulb method, and the bi-intercalation processes of H2SO4 into the GIC's have been studied by x-ray diffraction. Since stages 4–6 FeCl3–GIC's have more than three vacant interlayer spaces in the c-axis repeat distance, the bi-intercalation of H2SO4 into the GIC's takes place stepwise. Consequently, various FeCl3–H2SO4–graphite bi-intercalation compounds (GBC's), from the GBC's with one H2SO4 layer to the GBC's saturated with H2SO4, are obtained in the bi-intercalation processes. Their compositions are described as C6.0nFeCl3 · c(6.0/6.5)H2SO4 from the calculation of structure factor for x-ray diffraction, where n is the stage number of the starting FeCl3-GIC's, and c is the number of H2SO4 layers. Stacking sequences of all the FeCl3–H2SO4–GBC's are also determined.

Chloride-fluoride-graphite ternary compounds: Preparation and characterization

Stage 1 ternary MCl n-M′F n′-graphite bi-intercalation compounds ( M = Fe, Co, or Cu and M′ = B or Nb) have been prepared by the reaction of a fluoride vapor (BF 3 or NbF 5), under fluorine gas, with stage 2 metal chloride-graphite intercalation compounds (FeCl 3, CoCl 2, or CuCl 2-GIC). The reaction products were characterized by X-ray diffraction, FT-IR spectroscopy, and 19F NMR measurements. The measured repeat distances, I c , fit well with the sums of the respective repeat distances d 1 ( MX n - G), which would be exhibited by the stage 1 metal halogenide-GIC ( I c = d 1 (MC1 n-G) + d 1(M′F n′-G)). Unusual NMR line-shifts have been observed with compounds containing magnetic species such as Fe and Co. On the basis of these results, a three-step mechanism for the intercalation of a second reagent, M′ X′ n′ , into stage 2 MX n - GIC binary compounds is proposed. At first, a ternary bi-intercalation phase is formed, then a cointercalation phase can be obtained to finally give binary M′ X′ n′ -GIC in the third step. This would permit the obtention of original binary compounds which do not form by the more conventional procedures.

Preparation of Graphite Bi-intercalation Compounds

The preparation of graphite bi-intercalation compounds (GBCs) from stage-n GIC (n=2-4) is reviewed on the basis of experimental results. Twelve groups of GBCs were obtained by electrochemical, vapour phase and liquid phase methods. The c axis repeat distance Ic of the GBCs was very close to the sum of the interplanar distances of the two intercalates, measured in binary compounds. The bi-intercalation process is in competition with several kinds of other reactions such as displacement of intercalate.

On the Preparation of Graphite Bi-Intercalation Compounds from the Liquid Phase

On the Preparation of Graphite Bi-Intercalation Compounds from the Liquid Phase

ESR in CrCl3-based graphite intercalation and bi-intercalation compounds

ESR experiments have been performed on stage-1, -2, -3, CrCl3 graphite intercalation compounds as well as on CrCl3-CdCl2 and CrCl3-MnCl2 graphite bi-intercalation compounds. The measurements have been carried out at the X-band frequency and over the temperature range $4.2~{\rm K}\leq T\leq 294~{\rm K}$. The variation of the linewidth (ΔH) and the resonance field (Hr) have been examined as a function of the temperature and the angle θ between the external field and the crystal c-axis. The results reflect the anisotropic 2D character of these systems. The room temperature angular dependence of ΔH follows a (3 cos2 θ-1)2-like behavior and that of Hr has a (3 cos2 θ-1)-like form. For the singly intercalated systems, ΔH decreases with T according to (1-Θcw/T) in the high temperature region, then shows a local minimum at around 35 K followed by a critical-like divergence at lower temperatures. In the bi-intercalated compounds, ΔH vs. T exhibits three types of behavior : for T≥220 K, ΔH behaves like T2; for 120 K $\leq T\leq 220~{\rm K}$, ΔH seems to be proportional to (1-Θcw/T); for T≤120 K, ΔH shows a gradual increase which becomes steeper and steeper with falling T. The T2-like behavior may be explained in connection to a spin-lattice relaxation phenomenon which becomes important at high temperatures. The temperature dependence of Hr is characterized by an increase of Hr∥ and a decrease of Hr⊥ with decreasing temperature. This is consistent with the theoretical predictions developed for anisotropic low-dimensional systems, reflecting the increase in the anisotropy of low temperature susceptibility.

Dipole–dipole interactions as the source of spin-glass behaviour in exchangewise two-dimensional ferromagnetic layer compounds

We have studied magnetic layered materials that have in-plane ferromagnetic exchange interactions, and dipole–dipole only interplane interactions. These are biotite mica (including a nearly ideal annite end member) and new graphite bi-intercalation compounds that contain regularly stacked arrays of ferromagnetic and diamagnetic intercalates. All these strictly (exchangewise) two-dimensional materials exhibit hysteretic spin-glass magnetization cusps at temperatures up to 42 K. This proves that, in the presence of ferromagnetic correlations, classical dipole–dipole forces can play an important role in causing spin-glass behaviour at elevated temperatures. The layered materials described are ideal model systems for the study of a class of spin glasses that require only ferromagnetic exchange interactions. Below some characteristic temperature TFC, the latter interactions induce ferromagnetic correlations that give rise to significant dipole–dipole coupling leading to "domain configuration trapping" and an onset of temperature hysteresis at T ~ TFC.

Electrochemical preparation of the graphite bi-intercalation compound with H 2SO 4 and FeCl 3

Stage- n FeCl 3-GICs ( n = 2,3) prepared in the standard two-zone method were oxidized galvanostatically in H 2SO 4. The electrode potential vs. electric quantity curves observed during the treatment and the X-ray powder patterns of the products showed clearly the intercalation of H 2SO 4 into FeQ 3-GICs and the formation of the graphite bi-intercalation compounds (GBCs) of FeCl 3 and H 2SO 4. The c axis repeat distance I c of the GBCs, 17.38Å, from the stage-2 FeCl 3-GIC was equal to the sum of those of FeCl 3-GIC, 9.38Å, and of H 2SO 4-GIC, 8.00Å. From the stage-3 FeCl 3-GIC the compound with I c of 25.38Å ( = 9.38Å + 8.00Å + 8.00Å), through the intermediate with I c of 20.73Å ( = 9.38Å + 3.35Å + 8.00Å). The electrochemical reduction of these GBCs suggested that the intercalation of H 2SO 4 into FeCl 3-GICs is reversible.

Fluoride/fluoride and fluoride/sulfuric acid graphite bi-intercalation compounds

Stage-2 GICs with VF 6 and TiF 6 are used as host structures for the intercalation of other more volatile fluorides such as SbF 5, AsF 5 and WF y or of sulfuric acid. This leads to new graphite bi-intercalation compounds (GBCs) having a good regular stacking along the c-axis. From the x-ray diffraction and ESCA analyses, it is shown that the bi-intercalation affects the in-plane structure of VF 6 more than that of TiF 6 due to their different states in the parent GICs.

Structural and Transport Studies for Ternary Graphite Intercalated Phases (CoCl2, AlCl3)

Metal dihalide low-volatility is the major characteristic slowing down their intercalation into graphite (GICs: graphite intercalation compounds). An original synthesis using volatile heterocomplexes between metal dihalide (CoCl2) and gaseous dimer Al2Cl6 increases strickingly CoCl2 intercalation rate but entails cointercalation of significative amount of AlCl3 in the compounds MGICs (mixture graphite intercalation compounds). Structural studies along c-axis, in plane and out the plane (3 D stacking) display a similar behaviour as in the CoCl2 containing binary compounds. Microstructural studies confirm the separation of CoCl2 and AlCl3 in distinct domains. Other ternary phases with alternate CoCl2 and AlCl3 layers and characterized by a similar AlCl3/CoCl2 ratio can be obtained using biintercalation method: (GBICs: graphite biintercalation compounds). X-Ray diffraction shows that the biintercalation involves a complete lost of correlations in the successive CoCl2 or graphite layers. Transport studies of ternary phases (MGICs and GBICs) display an anomalous behaviour as T is lowered below the magnetic ordering temperature Tc especially for in plane resistivity.

Electrochemical preparation of metal chloride-sulfuric acid-graphite bi-intercalation compound

Stage-2 metal chloride-GICs (metal chloride: AlCl3, BiCl3 and CuCl2) prepared in the standard two-zone method were oxidized galvanostatically in H2SO4.The electrode potential vs. electric quantity curves observed during the electrochemical treatment and the X-ray powder patterns of the products showed clearly the intercalation of H2SO4 into metal chloride-GICs and the formation of the graphite biintercalation compounds (GBCs) of metal chloride and H2SO4.The c axis repeat distance Ic of the GBCs was equal to the sum of those of metal chloride-GIG and of H2SO4-GIC.

Electrochemical preparation and characterization of novel graphite bi-intercalation compounds

New graphite bi-intercalation compounds with BiCl 3/H 2SO 4, InCl 3/H 2SO 4 and BiCl 3/AuBr x have been prepared. It could be proved that the insertion of bisulfate starts at each free interlayer gap at the same time. Furthermore two tri-intercalation compounds with BiCl 3/AuBr x/H 2SO 4 and BiCl 3/AuBr x/TlCl 3, respectively, and a quadri-intercalation compound with BiCl 3/AuBr x/TlCl 3/H 2SO 4 could be obtained.