Neutron Diffraction Studies of Graphite−Potassium−Methylamine:  Staging Transitions and Structure of New Graphite Intercalation Compounds

Abstract

Graphite intercalation compounds (GICs) of the type KC x (CH 3 NH 2 ) y have been prepared by in situ amination of stage-II C 24 K and stage-IV C 48 K, and studied by time-of-flight neutron diffraction. As the vapor pressure of methylamine is increased the compounds pass through a rich sequence of staging transitions, in which the regular repeat of n empty graphite layers is progressively filled by intercalant. In these staging transitions, n always changes by -1. We therefore observe lower stage unaminated compounds as methylamine is introduced into the starting compounds. Isotopic substitution of CD 3 ND 2 for CD 3 NH 2 has enabled us to determine the detailed structure of the fully aminated stage-I and stage-II end compounds, C 24 K(CH 3 NH 2 ) 3 and C 48 K(CH 3 -NH 2 ) 3 . We find that the interlayer structure is based on 3-fold coordinated potassium ions and is relatively insensitive to the stage.

Graphite Powder and Multiwalled Carbon Nanotubes Chemically Modified with 4‐Nitrobenzylamine

“…For full intercalation to occur, the interlayer spacing must increase. An extensive literature search reveals that this can be readily achieved by intercalating alkalimetal ions, such as Li + , K + , into graphite to produce graphite intercalation compounds (GICs), for example, C 8 Li, C 24 Li, [18,19,[22][23][24][25][26]74] or by using graphitic oxide [20,21] and graphitic acid. [75] Hence, as our derivatisation procedure does not include any of the above-mentioned systems or criteria, we conclude that full intercalation of 4-NBA into graphite may be safely ruled out as possible mechanism of modification.…”

“…Examples of this method include initiating chemisorption of aryl diazonium salts by direct reduction with hypophosphorous acid in the presence of graphite powder; [5,6,11] (b) physical adsorption (physisorption) of the modifying molecules or substrates, such as proteins onto the carbon surface; [12][13][14][15] (c) finally, carbon paste electrodes can be used, where the paste binder is doped with the modifier during preparation. [5,6,16] Another method of tailoring the properties of carbon electrodes is to intercalate small molecules and ions, such as ammonia, [17,18] methylamine, [19] alkyl amines, [20,21] small aromatic molecules [22][23][24] and, in particular, the alkali-metal ions such as lithium, into various forms of graphite and graphitic oxide. [22][23][24][25][26] These forms of graphite have usually been pretreated in some way to cause an expansion in the interlayer spacing between the graphite sheets to facilitate the intercalation process.…”

Robust Kalman filter and smoother for errors-in-variables state space models with observation outliers based on the minimum-covariance determinant estimator

“…For full intercalation to occur, the interlayer spacing must increase. An extensive literature search reveals that this can be readily achieved by intercalating alkali‐metal ions, such as Li + , K + , into graphite to produce graphite intercalation compounds (GICs), for example, C 8 Li, C 24 Li,18, 19, 22–26, 74 or by using graphitic oxide20, 21 and graphitic acid 75. Hence, as our derivatisation procedure does not include any of the above‐mentioned systems or criteria, we conclude that full intercalation of 4‐NBA into graphite may be safely ruled out as possible mechanism of modification.…”

“…Another method of tailoring the properties of carbon electrodes is to intercalate small molecules and ions, such as ammonia,17, 18 methylamine,19 alkyl amines,20, 21 small aromatic molecules22–24 and, in particular, the alkali‐metal ions such as lithium, into various forms of graphite and graphitic oxide 22–26. These forms of graphite have usually been pretreated in some way to cause an expansion in the interlayer spacing between the graphite sheets to facilitate the intercalation process.…”

Kinetically Determined Phase Transition from Stage II (LiC12) to Stage I (LiC6) in a Graphite Anode for Li-Ion Batteries

“…The intercalation phenomena of metal ions (e.g., Li, Na, and K) or small molecules (e.g., HNO 3 , FeCl 3 , SbF 5 , and organic radicals) into graphite lead to the formation of graphite intercalation compounds (GICs). − Upon intercalation, this always demonstrates interesting phenomena, such as ion/vacancy ordering, selective ion insertion, and spatial ion ordering in the graphite host. In terms of Li intercalation into graphite, it gives rise to numerous intermediate phases whose composition (Li x C 6 ) could vary from x = 0 to 1.…”