”Eau de graphene” from a KC8 graphite intercalation compound prepared by a simple mixing of graphite and molten potassium
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Abstract:
We synthesized KC 8 by simply mixing molten potassium and graphite at 180 °C under inert atmosphere. The KC 8 shows typical shiny bronze color, Raman characteristics and XRD pattern of an efficiently intercalated stage 1 GIC, and is of sufficient quality to produce fully exfoliated graphenide solutions in tetrahydrofuran (THF) and subsequently single layer graphene in water as ”eau de graphene” (EdG). The evolution of absorption and Raman spectroscopic signatures of the EdG as a function of processing conditions give key indications on the number of layers of the graphene flakes dispersed in EdG. (© 2016 WILEY‐VCH Verlag GmbH &Co. KGaA, Weinheim)Keywords:
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The changes resulting from the compression of graphite-CrO a intercalation compounds are demonstrated in the TG curves. In comparison with the samples examined in the form of a flake bed, the compacted compounds begin to decompose at lower temperatures and their weight loss is higher, particularly above 220 ~ To explain the obtained results, the pressure-induced changes in the structures and the activities of the compounds are considered in relation to the method of intercalation, the concentration of the intercalant and the extent of exfoliation, Intercalation compounds of graphite (GIC) are formed in reactions between graphite and certain elements or molecules. The alternating sequence of n hexagonal graphite layers and a monolayer of foreign species, called the stage number, is a characteristic feature of their structure. The insertion of the guest species between the host graphite interspaces results in the creation of new, interesting properties. The structural, electrical and thermal changes effected by intercalation have been the most intensivelY explored [1, 2]. The thermal studies have often related to the exfoliation phenomenon caused by the thermal decomposition of GIC [3-9], Above a critical temperature, the intercalant escapes from the graphite interspaces, as demonstrated by a large expansion of the sample along the c-direction and consequently a very swollen product is formed. The process ofdeintercalation can be observed in the TG curves if the released intercalant itself undergoes thermal decomposition and/or participates in a secondary reaction with the graphite carbons. The occurrence of both processes has been reported for graphite-CrO 3 intercalation compounds (GIC-CrO3's) [10-12]. When flakes of GIC-CrO3's are heated above 220 ~ lower oxides of chromium are formed, not only due to the thermal decomposition of the intercalated CrO3, but also as a result of the reduction of CrO 3 by the graphite carbons. Consequently, a two-phase mixture of these oxides and the depleted
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Vibrational excitations in pr is t ine graphite and in graphite intercalation compounds are discussed. Modes associated with carbon atom intralayer motions and with the internal excitations of guest molecular species are emphasized.
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Graphite oxide
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Cr_2O_3-graphite intercalation compounds (GICs)were prepared using graphite and CrO_3 as raw materials by vacuum heat-treatment.The stage 5 GICs was formed after heat treatment at 1400℃,and it was examined and characterized by X-ray diffraction (XRD).The XRD analysis of intercalation compounds indicated that a number of non-carbon reactant (atom,molecule,ion or groups)could intercalate the layers of graphite with reticulated layer structure physically.Consequently the layered structure of graphite changed and thus new physical and chemical properties were obtained.X-ray photoelectron spectroscopy (XPS)suggested that the compound intercalated into graphite should contain Cr~(?)compound.
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It is known that it is possible to obtain compounds of graphite intercalation by oxidative treatment of graphite, getting termografenit from them. All known methods are associated with the graphite extraction from Fe-C containing wastes and its further oxidation. Intercalation compounds of graphite are formed as a result of the introduction of atomic and molecular layers of different chemical particles between the layers of graphite plates. Termografenit is very light dispersed graphite, having a unique complex of thermal and electrical properties. This is of interest to further study the technology of making this material. In previous studies, graphite was obtained from dispersed Fe-C containing wastes of metallurgy, and then was subjected to processing. However, considering the special microstructure and the morphology of the dispersed Fe-C containing wastes, they can become a raw material for production the intercalation compounds of graphite first, and then magnetic termografenit. In the present work dispersed Fe-C containing wastes of desulphurization at PJSC «Azovstal» with up to C 60% were used. The result of this investigation is receiving a new product – graphite intercalation compounds with magnetic properties – as well as the technology of getting the compounds. The technological peculiarities, providing for remaining significant amount of the iron oxides of Fe-C wastes in the material that in the process of oxidative intercalation give the intercalation compounds of graphite with magnetic properties, were found. Subsequent thermal expansion of the intercalation compounds of graphite at 1000°C makes it possible to obtain termografenit with a bulk density of 6-10 kg/m3, the specific magnetization saturation being 12-24 A·m2/kg and the specific electrical resistance being (1,9-9,0)·10-4 Ohms·m
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The purpose of this work is to study the electric properties of graphite and the synthesis of a few layers graphite intercalation compounds (GIC). First, intercalation of Li between graphite layers was done by soaking the substrates into a 20 ml n-butyllithium solution. Second, intercalation of FeCl3 into the graphite was done by heating FeCl3 powder and graphite in the quartz tube. For Li intercalation, the appearance of an extra Bragg reflection at 23.7º indicates that Li atoms were intercalated between the graphene sheets in the specimen we grew. For FeCl3 intercalation, the (00l) Bragg reflection was caused by the FeCl3-GIC. Probably Iron Chloride was intercalated in graphite. In the Raman spectra of graphite and FeCl3-GIC, the G, D and 2D peaks were confirmed. Additional peaks only in the specimen of FeCl3-GIC were observed at 1605 cm-1 and 3415 cm-1. It is speculated that the peak is related to the intercalation of FeCl3 into the graphite.
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According to X-ray power diffraction,the patterns of graphite which was treated by different methods are obtained.These X-ray diffraction patterns show that the layers of graphite are inserted by other matters by physical and chemical methods.This kind of matter is called graphite complex intercalation compound which widen the application of the graphite complex intercalation compound.
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The results presented in this paper demonstrate that the process of intercalation; i.e., the formation of chemical compounds via insertion of atomic or molecular species in the van der Waals gap between planes of lamellar solids can substantially improve the intrinsic lubricating properties of solids. Using graphite as a model host compound, various transition metals and metal chlorides intercalated into graphite were formulated into solid film lubricants and their lubricating properties determined in a laboratory wear test device. Comparisons of endurance life and load-carrying capacity are made relative to molybdenum disulfide and unintercalated graphite. Graphite/19.8 wt. percent CoCl2 was found to exhibit over a fivefold increase in endurance life while graphite/19.3 wt. percent NiCl2 provided a greater than twofold increase in load-carrying capacity relative to graphite and was equivalent to MoS2. The degree of improvement in endurance life was found to be dependent on the concentration of intercalant in graphite and the resulting increase in interlayer carbon spacing due to intercalation. A total of 23 different intercalate compounds were investigated at various concentration levels.
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