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 As other indirect additive manufacturing techniques, binder jetting comprises a shaping phase (the actual 3D printing) obtained by binding of the feedstock with a liquid agent, followed by a series of thermal treatments promoting sintering. However, the main difference stands in the use of dry particles to form a powder bed, which leads to a series of advantages as complete design freedom, high process throughput and material versatiliy. On the other side, green density is usually low, which may hinder complete densification of the printed parts.

In my research path at Politecnico di Milano, I'm tackling with all the challenges related with the production of structural and functional ceramics, as alumina, piezoelectric alloys and cemented carbides. It is fascinating to observe how material composition, printing parameters and sintering conditions contribute synergically to the densification mechanisms and the final properties of the printed components.

Alumina cannot be fully densified by conventional means, but the technique as demonstrated the possibility of realising complex geometries with minimal effort, which could fit the production of catalyst supports, membrane, filters and so on. Various feedstock can be employed, as dense or granulated materials, leading to different features and distributions of the internal porosities.

Similar issues were observed with piezoceramics as KNN and PZT. In this case, strategies to control the residual porosity are being developed, with the aim of tuning the piezoelectric performances of the material. Indeed, porous piezoceramics are of great interest to many industrial sectors, and the possibility of producing complex geometries would be an invaluable advantage.

Cemented carbides, as WC in cobalt matrix, are materials designed for sintering processes, so their densification is rather simple. It was possible to achieve full density (>99%) and produce intricate designs typical of the industry with mechanical properties on par with the minimal standards required.

In conclusion, the versatility and the advantages of binder jetting make it an interesting option for manufacturing of complex-shaped ceramics. In the three years of my PhD project, I had the chance of working on many different topics and problems still to be solved, in collaboration with amazing friends from ISSMC of Faenza and CSIC-ICV of Madrid and many projects are on the horizon!

Figure 1 Components printed by binder jetting

Marco Mariani

Department of Mechanical Engineering

Politecnico di Milano

Milano (Italy)

Marco.mariani@polimi.it