Binder Jet Additive Manufacturing with Granulated Ceramic Powders

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Currently, ceramic parts made by binder jet additive manufacturing have low density and poor mechanical properties; this award supports fundamental research addressing the use of granulated ceramic nanopowder for binder jet additive manufacturing to address these shortcomings. Nanoparticles are difficult to incorporate into the most common additive manufacturing approaches, but the use of granulations of ceramic nanoparticles with binders allows the use of nanoparticles without the normal drawbacks of limited spreadability. A granulated nanoparticle consists of nanoparticles combined with a polymer binder, which is then machined or milled to produce a particle a few tens of micrometers in diameter, which contains many nanoparticles. This allows the use of granulations without complicating spreading of powder in an additive manufacturing machine, and the use of nanoparticles to produce denser, stronger parts in additive manufacturing. Research results from this project will help enable additive manufacturing of high-density ceramic parts to produce wear-resistant parts economically. The ultimate application in mind is next-generation orthopedic implants, which is an economic area of great importance to the US. In addition, there are spillover applications in the aerospace, defense and automotive sectors, so that this proposal directly and positively impacts economic welfare and national security. The research will involve undergraduate and graduate students, including those from the underrepresented groups, who will conduct experiments and analyze experimental results. The research objective is to test three sets of hypotheses: (1) granulated powder leads to a higher printed and sintered density than both nanopowder and micropowder; (2) granulated powder has a similar flowability to micropowder but a higher flowability than nanopowder; and (3) granulated powder has a similar sinterability to nanopowder but a higher sinterability than micropowder. The first set of hypotheses will be tested by measuring the densities of printed and sintered samples from the three powders (granulated powder, nanopowder, and micropowder) with Archimedes' method and statistically comparing the results. The second set of hypotheses will be tested by comparing the Hausner ratios (the ratio between tap and apparent densities of each powder) of the three powders. The third set of hypotheses will be tested by comparing the achieved densities of the three powders by a traditional pressing and sintering means. Testing these three sets of hypotheses will result in new knowledge about effects of granulation on binder jet additive manufacturing, and flowing and sintering behaviors of granulated powder, nanopowder, and micropowder.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.