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Additive manufacturing consists in melting metallic powders to produce objects from 3D data, layer upon layer. Its industrial applications range from automotive, biomedical (e.g., prosthetic implants for dentistry and orthopedics), aeronautics and others. This study uses life cycle assessment to evaluate the possible improvement in environmental performance of laser-based powder bed fusion additive manufacturing systems on prosthetic device production. Environmental impacts due to manufacturing, use, and end of life of the designed solution were assessed. In addition, two powder production technologies, gas atomization (GA) and plasma atomization (PA), were compared in order to establish the most sustainable one. Production via traditional subtractive technologies and the additive manufacturing production were also compared. 3D building was found to have a significant environmental advantage compared to the traditional technology. The powder production process considerably influences on a damage point of view the additive manufacturing process; however, its impact can be mitigated if GA powders are employed. K E Y W O R D S additive manufacturing, industrial ecology, life cycle assessment (LCA), orthopedic device, product lifetime, traditional manufacturing INTRODUCTIONAdditive manufacturing (AM), a 3D building technology in which the building process involves layering materials, is rapidly increasing among manufacturing processes. Its strengths are its ability to create objects with a high geometrical complexity which is difficult and costly to obtain in traditional manufacturing, and the flexibility in meeting customer's requests in terms of design, without increasing the productive costs.Its aims are perfectly in line with the European Union Industry 4.0 plan (European Parliament Research Service, 2015), which is built on the model of the high-tech strategy of the German government, and whose main objectives are an increased flexibility and productivity in manufacturing, mass customization, and better quality.In order to achieve these ambitious goals a new vision, named the "smart factory," is needed, including the integration of IT services, such as the digitization of information and big data analysis, and of cyber-physical systems, such as embedded sensors, intelligent robots, and additive manufacturing devices.Additive manufacturing has been designated by the Boston Consulting Group, the worldwide multinational company in management consulting, as one of the five enabling technologies due to increased efficiency in material use (Sirkin, Zinser, & Rose, 2015).Powder bed fusion (PBF) is one of the latest terminologies for the designation of an AM process in which a metal powder layer is laid out over a bed and sintered by a high-energy beam, often a laser (Gibson, Rosen, & Stucker, 2015).This technology can be applied to a wide range of materials, but is most suited to metals. The opportunity to build metal objects with a complex geometry and high customization potential, which is difficult and costly in tra...

This paper represents the first attempt to quantitatively and reliably assess the environmental sustainability of solution combustion synthesis (SCS) with respect to other soft chemistry strategies, which are more conventionally employed in the preparation of engineered oxide nanomaterials, namely hydrolytic and non-hydrolytic sol-gel syntheses (i. e., HSGS and NHSGS). Indeed, although SCS is well known to rely on significant reduction in the energy as well as time required for the obtainment of the desired nanocrystals, its quantitative environmental assessment and a detailed comparison with other existing synthetic pathways represents an absolute novelty of high scientific desirability in order to pursue a more sustainable development in the inorganic chemistry as well as materials science research fields. TiO 2 nanoparticles were selected as the material of choice, for the production of which three slightly modified literature procedures were experimentally reproduced and environmentally evaluated by the application of the comprehensive life cycle assessment (LCA) methodology. Particularly, SCS was compared from an environmental perspective with sol-gel approaches performed both in water and in benzyl alcohol. The results of the present study were also framed among those recently obtained in a systematic study assessing seven further chemical, physical, and biological routes for the synthesis of TiO 2 nanoparticles, comprising also flame spray pyrolysis (typically used in industrial productions), highlighting and quantifying the excellent environmental performances of SCS.

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