Electrochemical Synthesis of Graphite Intercalation Compounds with Low-or Non-sulfur Content PDF Download

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Languages : en
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HKUST Call Number: Thesis MECH 1997 Kang.

Author: Zhengwei Zhang
Publisher:
ISBN:
Category : Graphite intercalation compounds
Languages : en
Pages : 260

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Author: Bahar Ozmen Monkul
Publisher:
ISBN:
Category : Graphite fluorides
Languages : en
Pages : 338

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New acceptor-type graphite intercalation compounds (GICs) containing perfluoroalkyl anions have been synthesized by using both chemical and electrochemical methods and characterized by elemental and thermogravimetric analyses. Investigation into these graphite intercalation compounds can provide novel materials and a detailed understanding of their properties. GICs of composition Cx[FB(C2F5)3]·[delta]F are prepared for the first time by the intercalation of fluoro-tris(pentafluoroethyl)borate anion, [FB(C2F5)3]−, under ambient conditions in aqueous (48 %) hydrofluoric acid containing the oxidant K2[MnF6].Powder-XRD data indicate that products are pure stage 2 and physical mixture of stage 2 and stage 3 after 1 h to 20 h reaction times. The calculated basal repeat distance, Ic, is 1.20 nm for stage 2 and 1.54-1.56 nm for stage 3 GICs, corresponding to gallery heights of di= 0.86-0.89 nm. In addition, stage 2 GIC of Cx[FB(C2F5)3]·[delta]CH3NO2 having di=0.84 nm is prepared by electrochemical oxidation of graphite in a nitromethane electrolyte. The elemental analyses of these complex GICs required that a new sample digestion protocol be developed. After digestion, the fluoride amounts in these GIC samples were analyzed by using ion-selective fluoride combination electrode. The method developed is able to provide fluoride anion content in GICs without interference from the decomposition products of [FB(C2F5)3]- anion. For the boron analyses the same digestion procedure above is used and the B contents were determined by ICP-AES. For Cx[FB(C2F5)3]·[delta]F, both compositional parameters x and [delta] are obtained from the results of elemental B and F analyses. For the chemically prepared GICs at 1 h to 20 h, calculated x values were in the range of 51-56 and the calculated [delta] values increased with reaction time from approx. 0-2. Combining B analysis and TGA mass loss gives a composition of x=44 and [delta]= 0.37 for the electrochemically prepared GIC of Cx[FB(C2F5)3]·[delta]CH3NO2. Energy minimized structure for the isolated borate anion and powder XRD data show that the borate anions adopt a "lying-down" orientation where the long axes of [FB(C2F5)3]- intercalate anions are parallel to the encasing graphene sheets. The same electrochemical synthesis strategy is also used for the preparation of a new acceptor-type GIC containing the cyclo-hexafluoropropane-1,3-bis(sulfonyl)amide anion, [CF2(CF2SO2)2N]−. The gallery heights of 0.85-0.86 nm are determined by powder X-ray diffraction for stage 2 and 3 products. These GICs are obtained by electrochemical oxidation of graphite in a nitromethane electrolyte. GICs containing the linear anion, [(CF3SO2)2N]− are also prepared in order to compare the gallery heights and the electron charge distributions that helps to understand the GIC stabilities within the graphene sheets. The compositions of GICs containing [CF2(CF2SO2)2N]− are determined by thermogravimetric, fluorine and nitrogen elemental analyses. GICs of composition Cx[(C2F5)3PF3] are prepared for the first time by the intercalation of tris(pentafluoroethyl trifluorophosphate (FAP) anion, [(C2F5)3PF3]− by electrochemical oxidation of graphite. Powder-XRD data indicate that products are of stages 2-4 with gallery heights of 0.82-0.86 nm. These GICs are characterized by the same methods using TGA and F ion selective probe analyses.

Author: Toshiaki Enoki
Publisher: Oxford University Press
ISBN: 9780195351842
Category : Science
Languages : en
Pages : 556

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Graphite intercalation compounds are a new class of electronic materials that are classified as graphite-based host guest systems. They have specific structural features based on the alternating stacking of graphite and guest intercalate sheets. The electronic structures show two-dimensional metallic properties with a large variety of features including superconductivity. They are also interesting from the point of two-dimensional magnetic systems. This book presents the synthesis, crystal structures, phase transitions, lattice dynamics, electronic structures, electron transport properties, magnetic properties, surface phenomena, and applications of graphite intercalation compounds. The applications covered include batteries, highly conductive graphite fibers, exfoliated graphite and intercalated fullerenes and nanotubes.

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Category : Dissertations, Academic
Languages : en
Pages : 956

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Author: Weekit Sirisaksoontorn
Publisher:
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Category : Graphite intercalation compounds
Languages : en
Pages : 147

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Novel donor-type graphite intercalation compounds (GICs) containing tetra-n-alkylammonium (TAA) cations have been synthesized by using both ion-exchange and electrochemical methods. Structural and compositional data of the resulting TAA-GICs are investigated by using powder X-ray diffraction (PXRD), one-dimensional electron density calculations, thermogravimetric and elemental analyses, and capillary zone electrophoresis (CZE). A new GIC with composition of [(C4H9)4N]C44 is prepared by intercalation of tetra-n-butylammonium cation, (C4H9)4N, via ion exchange from a [Na(en)1.0]C15 GIC (en = ethylenediamine). The synthesis reaction proceeds at 60°C for 90 min in a N, N-dimethylformamide (DMF) solvent. A dull-black stage-1 [(C4H9)4N]C44 provides the gallery height of di = 0.802 nm, indicating a presence of flattened cation conformation. CZE data reveal that the Na(en) cationic complex is quantitatively displaced by (C4H9)4N+ cations. A homologous series of TAA-GICs; i.e. TAA = symmetric (C[subscript n]H[subscript 2n+1])4N+ (n = 3-8) and asymmetric (CH3)3(C12H25)N+, (CH3)3(C1H3-- )N+ and (CH3)2(C1H3-- )2N+, are prepared using the similar ion-exchange procedure, albeit with shorter reaction time (10 min), in dimethylsulfoxide (DMSO). The obtained TAA-GICs contain either monolayer or bilayer arrangement of flattened TAA intercalates with significant co-intercalation of DMSO molecules in a bilayer arrangement. PXRD data suggest that the monolayer is also observed with small TAA intercalates such as (C3H-- )4N+ and (C4H9)4N+ with di ~ 0.80 nm. On the other hand, larger symmetric TAA cations, (C[subscript n]H[subscript 2n+1])4N+ (n = 5-8), and asymmetric TAA cations all form only the bilayer arrangement with d[subscript i] ~ 1.10 nm. Thermogravimetric analyses combined with mass spectrometry and elemental analyses show a presence of ~1-2 DMSO co-intercalates per bilayer cation. The generated electron density map is sufficient to confirm the existence of bilayer structures, including DMSO co-intercalates. These GICs have very low charge density on graphene sheets for stage-1 GICs, namely C63p− for [(C7H15)4N]C63p−1.4DMSO, as confirmed by Raman peak shifts. In addition, TAA-GICs are also synthesized using the electrochemical reduction on a graphite electrode in TAABr/DMSO-based electrolytes. Similar to GIC products obtained from a chemical ion-exchange method, large TAA cations, (C[subscript n]H[subscript 2n+1])4N+ (n = 5-8), form the bilayer arrangement with 0.7-1.2 DMSO co-intercalates per TAA cation and di ~ 0.11 nm. A mixed phase product, including a stable (C4H9)4N+ monolayer arrangement (di = 0.815 nm), is observed in (C4H9)4N+ intercalation with a little amount of DMSO. No stable and isolable GIC products are obtained in case of TAA cations smaller than (C4H9)4N+ even though cyclic voltammograms show the characteristic features of reversible intercalation/de-intercalation for these cations. Therefore, a surface passivation model is proposed to describe the relative stabilities of GICs containing large TAA intercalates. The effect of surface passivation is further studied on the preparation of (C2H5)4N-GIC. Large TAA cation such as (C6H13)4N+, (C--H15)4N+ or (C8H1-- )4N+, is used to passivate the graphite surface of [Na(en)1.0]C15, followed by ion exchange with (C2H5)4N+ to obtain a (C2H5)4N-GIC product. PXRD data suggest the formation of a stage-1 compound with di ~ 0.81 nm, indicating monolayer arrangement of intercalate. The GIC composition is found to be [(C2H5)4N]C5--.0.5DMSO. Additionally, the hydrophobic nature of passivated GIC surfaces enhances the chemical stabilities in aqueous media and other protic solvents.

Author: Birte Andrea Jache
Publisher:
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Category :
Languages : en
Pages :

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Author: Mahmood Aliofkhazraei
Publisher: CRC Press
ISBN: 1466591196
Category : Science
Languages : en
Pages : 3379

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Graphene is the strongest material ever studied and can be an efficient substitute for silicon. This six-volume handbook focuses on fabrication methods, nanostructure and atomic arrangement, electrical and optical properties, mechanical and chemical properties, size-dependent properties, and applications and industrialization. There is no other major reference work of this scope on the topic of graphene, which is one of the most researched materials of the twenty-first century. The set includes contributions from top researchers in the field and a foreword written by two Nobel laureates in physics. Volumes in the set: K20503 Graphene Science Handbook: Mechanical and Chemical Properties (ISBN: 9781466591233) K20505 Graphene Science Handbook: Fabrication Methods (ISBN: 9781466591271) K20507 Graphene Science Handbook: Electrical and Optical Properties (ISBN: 9781466591318) K20508 Graphene Science Handbook: Applications and Industrialization (ISBN: 9781466591332) K20509 Graphene Science Handbook: Size-Dependent Properties (ISBN: 9781466591356) K20510 Graphene Science Handbook: Nanostructure and Atomic Arrangement (ISBN: 9781466591370)

Author: Mahmood Aliofkhazraei
Publisher: CRC Press
ISBN: 146659134X
Category : Science
Languages : en
Pages : 480

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Explore the Practical Applications and Promising Developments of GrapheneThe Graphene Science Handbook is a six-volume set that describes graphene's special structural, electrical, and chemical properties. The book considers how these properties can be used in different applications (including the development of batteries, fuel cells, photovoltaic

Author: Paul Hagenmuller
Publisher:
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Category : Science
Languages : en
Pages : 654

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Inorganic Solid Fluorides: Chemistry and Physics deals with the chemical and physical properties of inorganic solid fluorides and covers topics ranging from methods used in the preparation of fluorides to the crystal chemistry of fluorides and transition metal oxyfluorides. Defects in solid fluorides are also discussed, along with fluorine intercalation compounds of graphite and high oxidation states in fluorine chemistry. This book is comprised of 21 chapters and begins with an overview of general trends related to fluorides, including bonding problems and economic implications of fluorides.