Graphite thermal reactions

The description of the association of heterocychc chemistry and microwave irradiation has also shown that performing microwave-assisted reactions should be considered with special attention. A few of these considerations can be applied generally for conducting microwave-assisted reactions and include the following (a) the ratio between the quantity of the material and the support (e.g., graphite) or the solvent is very important (b) for solid starting materials, the use of solid supports can offer operational, economical and environmental benefits over conventional methods. However, association of liquid/solid reactants on solid supports may lead to uncontrolled reactions which may result in worse results than the comparative conventional thermal reactions. In these cases, simple fusion of the products or addition of an appropriate solvent may lead to more convenient mixtures or solutions for microwave-assisted reactions. 

Its inert behavior towards numerous chemical compounds and its adsorbent properties (responsible for the retention of volatile or sublimable organic compounds), make graphite the choice support for thermal reactions. Among its impurities, magnetite was revealed to be an active catalyst, and some reactions can be performed without any added catalyst. Two processes are then possible, the graphite-supported reaction ( dry process), and the reaction in the presence of a small amount of graphite (solid-liquid medium). 

The seminal work by Maleki et al. in 1999 seemed to provide a direct answer to the question about which of the five possible processes was responsible for the thermal runaway of a lithium ion cell. Using ARC, they first determined the thermal runaway onset temperature in a lithium ion cell based on LiCo02/graphite with LiPFe/EC/DMC/DEC to be 167 °C. The thermal reaction, however, was found to start at 123 °C and continued to self-heat the system to the above onset temperature. Using DSC and TGA, they further determined the heat evolution as well as the thermal profile for the individual components of the cell in the presence of electrolytes, which included cathode, anode, and anode binder (PVdF). 

Vol 10 "The Thermal Properties of Graphite "Lamellar Reactions in Graphitizable Carbons and in Vol 11 "Highly Oriented Pyrolytic Graphite 7) G. Cohn, Edit, Expls -Pyrots 7(1), 1974 (Lists Vols 8—11 of the above book and suggests that the paper on electronic properties in Vol 8 may be of interest in connection with carbon bridge detonators)... 

N.-S. Choi, I. A. Profatilova, S.-S. Kim, E.-H. Song, Thermochim. Acta 2008, 480, 10-14. Thermal reactions of lithiated graphite anode in LiPF6-based electrolyte. 

Thermal conductivity of graphite Thermal conductivity of insulating alumina Equilibrium potential for reaction (2.93)... 

Graphite remains the pre-eminent anode material for lithimn-ion batteries because of its good performance. Thermal reactions at salt-based SEls proceed via smface salt decomposition and yield mainly LiF the reaction in predominantly solvent based SEls proceeds via decomposition of Uthium-alkyl carbonates to Li2C03. The reaction mechanism of anode for lithium-ion cell is expressed as follows [12, 13] ... 

Choi NS, Profatilova lA, Kim SS, Song EH (2008) Thermal reactions of lithiated graphite anode in liPEg-based electrolyte. Thermochimica Acta 480 (1-2) 10-14... 

Any sihcate that forms thermally and chemically stable residual compounds as its oxygen content is reduced provides a suitable source of siUcon for this reaction. A typical process consists of alternating aluminum, siUca, and graphite plates separated by 2—4-cm thick graphite spacers stacked in a graphite-lined alumina tube and heated to 1400°C for 12 h in a nitrogen atmosphere. After cooling for approximately 6 h the fibers are removed. 

The resistance of graphite to thermal shock, its stabiUty at high temperatures, and its resistance to corrosion permit its use as self-supporting vessels to contain reactions at elevated temperatures (800—1700°C), eg, self-supporting reaction vessels for the direct chlorination of metal and alkaline-earth oxides. The vulnerabiUty of cemented joints in these appHcations requires close tolerance ( 0.10 mm) machining, a feat easily accompHshed on graphite with conventional metal machining equipment. 

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