Chapter 2 - Synthesis of nanomaterials using top-down methods

Abstract

Nanomaterial synthesis procedures that are scalable, cheap, and green are not common. Several synthesis strategies are discussed with a focus on top-down syntheses. Here, ball milling for nanoalloys, composites, grains, and semicrystalline materials is discussed. The mechanical alloying processes are used to generate amorphous and crystalline alloys as well as metal and nonmetal nanocomposites by doping, metal insertion, and co-alloying are also discussed. The nonequilibrium processes whereby alloying is achieved are discussed in the thermodynamics of mixing different elemental powders, milling types, and inert atmosphere to generate stable mixed powder materials with the same composition stoichiometrically required. Under higher energies, deformation and fracture of the materials occur, and these deformations define particle shape and porosity. Cold-welding approaches also lead to material fracture and smaller powders for different alloying particles in grain-refined matrices. The application of mechanical milling of different alumina materials can lead to the synthesis of a wide variety of materials for specific applications, which can be further modified using postannealing or activation processes to generate activated materials. This chapter reviews the basic concepts, energetics, and considerations of synthesis of different nanomaterials for catalysis and energy applications.