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In no event shall the Royal Society of Chemistry be held responsible for any errors or omissions in this Accepted Manuscript or any consequences arising from the use of any information it contains. www.rsc.org/nanoscale Page 1 of 41 Nanoscale Nanoscale REVIEW High Energetic Compositions Based on Functionalized Carbon Nanomaterials Received 00th November 2015, Qi-Long Yana, Michael Gozin†a, Feng-Qi Zhaob, Adva Cohena, Si-Ping Pangc Accepted 00th January 2016 DOI: 10.1039/x0xx00000x In recent years, research in the field of carbon nanomaterials (CNMs), such as fullerenes, expanded graphite (EG), carbon nanotubes (CNTs), graphene, and graphene oxide (GO), have been widely used in energy storages, electronics, catalysts, www.rsc.org/ biomaterials, as well as medical applications. Regarding energy storage, one of the most important research directions is the development of CNMs as carriers of energetic components by coating or encapsulation, thus forming safer advanced nanostructures with better performances. Meanwhile, some of the CNMs can also be functionalized to become energetic additives. This review article covers updated preparation methods for the aforementioned CNMs, with a more specific orientation towards the use of these nanomaterials in energetic compositions. Besides, the effects of these functionalized CNMs on thermal decomposition, ignition, combustion and reactivity properties of energetic compositions are significant, which are further discussed with more details. It has been shown that the use of functionalized CNMs in energetic compositions would greatly improve their combustion performances, thermal stability and sensitivity. In particular, the functionalized Fullerene, CNTs and GO are the most appropriate candidate components in nanothermites, solid propellants and gas generators, due to their superior catalytic properties as well as facile preparation methods. Manuscript Introduction nanomaterials (CNMs) have been developed as carriers of EMs, combining to form advanced structures with higher performances. Energetic materials (EMs) are a class of material with high Some of them, as coating or encapsulating materials, is also very amount of stored chemical energy that can be released in a fast 5 effective in improving the safety of energetic systems . way, and the typical classes of EMs include explosives, pyrotechnics It’s well known that solid carbon materials (SCMs) can be and propellants. Gunpowder (GP), invented in ancient China, is found in different forms of bulk phases (e.g. Diamonds) as well as considered as the first EMs in human history. It is a mixture of 6 more molecular forms (e.g. fullerenes) . In fact, CNMs has a unique sulfur, charcoal, and potassium nitrate (saltpeter). Charcoal as form place in nanoscience owing to their exceptional electrical, thermal, of carbon together with sulfur are fuels, while the saltpeter is an Accepted chemical and mechanical properties. They have found application in oxidizer1,2. Due to promising heat and gas generation properties, GP diverse areas as composite materials, energy storage and has been widely used as firearm propellant and pyrotechnic conversion, sensors, drug delivery, field emission devices and composition. As a primitive energetic composition, the GP is no nanoscale electronic components, due to strong adsorption longer widely in use and replaced by more advanced energetic capacity, chemical stability, high mechanical strength as well as easy systems both in civil and military applications, which are still under 7 modification . Currently, several kinds of SCMs could be used in the fast development. In past decades, researchers are seeking safer field of EMs, which can be divided into two groups. One group is energetic materials with better performance, which implies four nano-powdered carbon, such as carbon black (CB) and aspects: high energetic, insensitive, nontoxic, and environmental 3 nanodiamond, where the latter can be used as a reducing agent in friendly . In newly developed propellants and explosives, the 8 energetic compositions . Another one is CNMs with rich pore carbon-rich materials are thereby gradually replaced by high Nanoscale structure and large surface area, including fullerenes, expanded nitrogen materials (HNMs) with higher energy content and better graphite (EG), carbon nanotubes (CNTs), graphene, and graphene oxygen balance4. However, these HNMs are in most cases not safe oxide (GO). The application of these materials in the field of enough for practical applications. Recently, a variety of carbon 9 energetic compositions has been recently summarized . In order to further expand the scope of their applications in EMs, usually nano- sized carbon materials with large surface area could be a. Center for Nanoscience and Nanotechnology, Faculty of Exact Science, Tel Aviv functionalized with energetic groups, or coupled with binders, University, Tel Aviv 69978, Israel. b. Science and Technology on Combustion and Explosion Laboratory, Xi’an energetic compounds, metal fuels, combustion catalysts, etc. to Modern Chemistry Research Institute, Xi’an 710065, China. form novel advanced function nanostructures with better c. School of Materials Science & Engineering, Beijing Institute of Technology, Beijing 100081, China. properties that could be used in propellants, explosives and 10 † Corresponding authors, M. Gozin, e-maill: [email protected], Tel: +972-3-640- pyrotechnics . In recent years, extensive research has been done 5878; Q.-L. Yan, e-mail: [email protected]. This journal is © The Royal Society of Chemistry 2016 Nanoscale, 2016, 00, 1-41 | 1 Nanoscale Page 2 of 41 REVIEW Nanoscale on preparation and application of carbon nanomaterials in EMs11, journals, this paper is trying to do an overview of preparation especially graphene, GO, CNTs and their composites as combustion methods of CNMs based EMs as well as their effects on catalysts or energetic components12,13. In addition, activated carbon performance and sensitivity of corresponding energetic fiber and graphite were also attempted in propellant manufacture compositions. and waste treatment. The relevant research topics include: design, synthesis, characterization and properties of carbon based Classification of Carbon Nanomaterials nanomaterials; potential usage of nano-sized carbon materials in Carbon is one of the most important natural elements, and it rocket propulsion; the catalytic effect and mechanisms of carbon has sp3, sp2, sp hybridizations of its orbitals. The molecular carbon based nano-sized catalysts on decomposition and combustion of atoms’ anisotropy sp2 may lead to anisotropy of some crystals of energetic materials; application and characterization of carbon these materials (Table 1). Therefore, carbon materials have widely 14 nanomaterials in purification of waste water in explosive industry . extended properties. In fact, more and more new carbon materials In the past decades, a large amount of papers has been continue to be discovered and artificially prepared. There is no published regarding preparations and applications of CNMs, based other element like carbon as a single element can form so diverse on which several review papers are available mainly in Chinese and completely different substances, in terms of structures and 8,12,15-18 literature . Experimental and theoretical data on new carbon properties, such as 3-D diamond crystal and graphite, 2-D graphite nanostructures using fullerenes, nanotubes as well monolithic sheets, 1-D CNTs and 0-D fullerene molecules. It has been diamond-like nanoparticles, nanofibers, various nanocomposites as discovered that carbon materials are mostly superior in their 15 starting materials are summarized in a Russian journal as well . hardness, optical properties, heat resistance, radiation Their atomic and electronic structures, the nature of chemical characteristics, chemical resistance, electrical insulation, electrical bonds and physicochemical properties are compared. The conductivity, surface and interface properties to many other applications of fullerene materials in catalytic reactions including materials. Carbon materials probably can cover the characteristics hydrogen transfer and hydrosilylation, pyrolysis of alkanes, H2-D2 of all substances on the planet, such as “the hardest to the softest”, 16 exchange, coupling and alkyl transfer reaction are reviewed . “insulator to semiconductor, further to a super conductor”, Recent advances on the application of graphene based catalysts in “insulation to great thermal conductivity”, “fully-light absorbing to Manuscript energetic materials are also introduced, revealing that they have completely transparent” and so on, so these