The objective of this research is to develop a scalable manufacturing process for high-volume production of low-cost graphene materials from lignin. The process includes preparation of catalyst-lignin precursors, pretreatment of precursors, and catalytic graphitization of kraft lignin to graphene materials. A growth concept, “catalytic thermal molecular welding (CTMW)” technique is proposed and validated to produce graphene materials from solid carbon resources. CTMW technique is a single process with two stages, i.e., the carbon-encapsulated metal nanostructures are first prepared. Then in the second stage these core-shell structures are opened by “scissoring molecules”, the cracked carbon shell units are welded and reconstructed to multilayer graphene materials under high temperature with selected “welding reagent gases” like light hydrocarbons (methane, natural gas, etc.) and hydrogen. Multi-layer nano-shell structure-based graphene materials, such as fluffy graphene, graphene chains, multi-layer graphene nanoplatelets, flatten or curved sheet-like graphene can be produced through altering fabrication conditions. The effects of transitional metal catalysts (Ni, Cu, Fe, and Mo) on the yields and structures of multi-layer nano-shell structure-based graphene materials from lignin are compared. The effects of the iron chemical resources (Fe(NO3)3, FeCl2, FeCl3, and Fe2O3 (nano)), iron loading on the yields and structures of multi-layer graphene materials from lignin are also examined. The influences of temperature, heating rate, heating time, metal-lignin precursor particle size, and welding reagent gas types on the yield of multi-layer graphene materials from lignin resources are investigated. Welding temperatures are optimized as1,000°C or above, with heating rates of 10°C or above. Welding gases including, argon (Ar), hydrogen (H2), methane (CH4), natural gas (NG), and mixed of these gases, are used at flow rates from 20 to 300 mL/min. Heating time is controlled between 0 to 5 hours. The effect of precursor particle size on final products is examined between 44 to 426 microns (Delta-m).

Les multicouches de graphène en empilement rhomboédrique sont considérés comme une phase prometteuse du carbone. Cela est due à la particularité de cette phase de pouvoir exhiber des états à forte corrélation électronique comme le magnétisme ou la supraconductivité à haute température critique. Ce qui est due, a son tour, à l’occurrence d’un état de surface avec une dispersion d’énergie électroniques quasi-nulle à proximité du niveau de Fermi. Malgré que le graphite Bernal soit la forme la plus stable du graphite, des échantillons a trois et quatre couches de graphène en empilement rhomboédrique ont pu être synthétisés. Plus récemment, des flocons d’épaisseur dépassant les 17 couches ont été isolés et provisoirement attribués à des séquences d’empilement rhomboédrique. Cette attribution à été faite via des expériences de spectroscopie Raman sous champ magnétique, bien que l’empreinte Raman des multicouche de graphène en empilement rhomboédrique est actuellement inconnue. Même le cas simple du spectre Raman résonnant à deux phonons (le pic 2D) du graphite Bernal n’est pas totalement compris. Dans ce travail de thèse, nous fournissons une description ab-initio complète du pic Raman 2D dans les systèmes de graphène à trois et quatre couches pour tous les empilements possibles, ainsi que pour le graphite Bernal, rhomboédrique et une alternance de graphite Bernal et rhomboédrique. / Multi-layer graphene with rhombohedral ABC stacking is considered as a promising carbon phase possibly displaying correlated states like magnetism or high-T c superconductivity due to the occurrence of an ultraflat electronic surface band at the Fermi level. Despite Bernal graphite being the most stable form of graphite, three and four layers graphene samples with rhombohedral stacking can be synthesized. Recently, flakes of thickness up to 17 layers were tentatively attributed ABC sequences although the Raman fingerprint of rhombohedral multilayer graphene is currently unknown and the 2D two-phonon resonant Raman spectrum of Bernal graphite not completely theoretically understood. Here we provide a complete first principles description of the 2D Raman peak in three and four layer graphene for all possible stackings, as well as for bulk Bernal, rhombohedral and an alternation of Bernal and rhombohedral graphite, that can be seen as a periodic sequence of ABA and ABC trilayers. Calculations for several laser energies are performed and we give practical prescriptions are proposed to identify long range sequences of ABC multi-layer graphene flakes.