Additive Manufacturing and Sintering of Advanced Materials: Innovative Technologies Development, Computational simulations, experimental validation

Already from its invention, Additive Manufacturing (AM) was a groundbreaking technology and have increasingly grown attention, especially since it has been applied to advanced materials. It can manufacture otherwise impossible to achieve geometries, often with time and cost saving if compared to traditional technologies. Even if nowadays, there are many widely adopted printing technologies, each of them has various limitations in terms of costs, processable materials and operator skills. This work aims at developing possible alternative AM technologies to current standards to provide easy to use, low-cost and versatile solutions. The first proposed alternative is based on an already adopted printing approach that falls under the umbrella of Material Extrusion (MEX) based technologies. More in specific, it is usually referred as Robocasting. The process consists in the extrusion of a paste made of the powder of the material of interest, a solvent, and a binder. It is fundamental to understand and tailor the rheological properties of these inks to achieve a reliable and consistent print. The second alternative is even more innovative. It has been developed what internally is called Direct Powder Deposition (DPD) which more in general belongs to the Material Jetting (MJT) type of printing. In this case, the powder of interest is directly deposited inside a die, alongside a sacrificial material, also in powder form, via piezoelectric actuators. With this approach any organic component is removed. In this case as well, rheological properties of the powder play a fundamental role. Both approaches need a post printing step called sintering. Due to the extrusion of loose powders, these grains must undergo a binding process and form a bulk material. Also, in this step the work aims at innovating by combining additive manufacturing and field assisted sintering technology (FAST) like Spark Plasma Sintering (SPS). Many challenges arise when innovative technologies are employed, for example SPS has been limitedly implemented due to its vast energy consumption. During the thesis, a possible solution is explored by coupling the machine with Finite Element Modeling (FEM) to understand how the sintering progresses and optimize the heating element shape. To prove the effectiveness of the proposed ideas, they have been implemented in technologically relevant environments each with its peculiarities and challenges.