Digital Light Processing of Complex Ceramic Oxides: from Tailored Density Components to Ox-Ox CMCs Fabrication

This research work investigates the application of Digital Light Processing (DLP) technique for the development of oxide ceramics and oxide-oxide ceramic matrix composites (Ox-Ox CMCs) with tailored properties and complex geometries. The work covers the entire process, from slurry formulation and optimisation, to printing, thermal treatments and properties evaluation. In the first part, the study focuses on alumina-based structures for electromagnetic applications. Alumina cellular architectures with controlled porosity are printed and sintered, reaching near-full density (97% of the theoretical value) and enabling the tailoring of dielectric constants for waveguide antennas. The influence of the slurry constituents on the presence of delaminations in green components is demonstrated. Optimised formulation provides stable rheology, improved interlayer adhesion and good sintering behaviour, while dielectric testing confirms a linear correlation between porosity and dielectric constant. The second part of the work demonstrates the feasibility of producing highly complex silica cores and moulds for investment casting using a specially designed silica-based slurry. The sintered and infiltrated cores exhibit full leachability in KOH solution (100%), good mechanical properties (16.2 MPa) and lower porosity (27.4%) compared to injection-moulded reference. Dimensional accuracy is within 0.20-0.35 mm of CAD models, even for challenging geometries with thin, overhanging and tilted regions, highlighting the potential of DLP to reproduce really complex features. Investigations on silica moulds identify both opportunities and limitations of the process: while complex geometries are successfully fabricated and enable defect-free copper infiltration, issues such as cleaning efficiency and surface roughness strongly depend on geometry and layer thickness. The third part explores the fabrication of Ox-Ox CMCs via DLP, with particular focus on fibre insertion strategies and interphase development. Slurry composition and process conditions directly affect matrix densification and shrinkage. Dry bundles insertion into green or sintered matrices improved structural CMC’s integrity, while rigid cured bundles generate voids and discontinuities between bundles and matrix and among fibres. Interphase quality affects the mechanical behaviour: well-developed interphases promote pseudo-ductile behaviour, typical of CMCs, while poor or discontinuous interphases lead to brittle fracture.