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This paper reports a new approach to density improvement in ceramic binder jetting additive manufacturing: combining powder bed compaction and nanopowders. Samples were printed on a commercially available binder jetting 3D printer using an alumina nanopowder. Compaction thickness was varied across 0, 5, 10, 15, 20, and 60 μm at a layer thickness of 5 μm, and across 0, 100, and 200 μm at a layer thickness of 30 μm. Sintered density, as well as powder bed density, was measured. Furthermore, microstructure of sintered samples, with a focus on number and size of pores, was investigated to substantiate the density results. It was shown that at the same layer thickness, higher compaction thickness resulted in higher powder bed density, higher sintered density, and smaller number and size of pores in sintered samples. The highest sintered density (72.0%) achieved in this study was on par with the highest density reported in the literature on binder jetting of alumina without involving unusual liquid feedstocks or special post-processing techniques, demonstrating the effectiveness of this new approach to density improvement.

In powder bed additive manufacturing, feedstock powder can be dispensed onto powder bed through a hopper. The hopper dispensing system assisted by ultrasonic vibration is effective, especially for powder with small particle sizes (e.g.

This short communication reports an experimental investigation on the relationships among powder properties (i.e., apparent density, tap density, and Hausner ratio), feed region density, and powder bed density in ceramic binder jetting additive manufacturing. Seven differently sized alumina powders (from 0.05 μm to 70 μm) were used for this experimental investigation. Simple linear regression was applied to analyze the experimental data. It was found that powder bed density matched well with feed region density under all conditions of this investigation. The results also showed that apparent density was a stronger predictor than tap density and Hausner ratio for powder bed density.

Binder jetting is a promising additive manufacturing process to fabricate a wide range of materials, including ceramics. The objective of this research is to investigate the effects of particle size on flowability and sinterability of the feedstock powder and resultant properties of fabricated parts. A commercial ceramic composite powder was sieved into three different particle size ranges: designated as fine, medium, and coarse powders, respectively. Flowability and sinterability measurements were performed on the sieved powders. After printing and sintering, the density of samples was measured with the Archimedes’ method. Compressive tests were performed to investigate the mechanical properties of the fabricated parts. The experimental results showed that flowability increased but sinterability decreased as particle size increased. The printed and sintered density was dependent on both flowability and sinterability: the highest density was achieved by the medium powder due to the balance between flowability and sinterability. The compressive strength was dominated by sinterability: the highest strength was achieved by the fine powder because of the highest sinterability.

Because of its high sinterability, nanopowder could be beneficial for ceramic binder jetting additive manufacturing to achieve a high density on printed and sintered parts. However, the flowability of nanopowder is poor because of the large interparticle cohesion. This poor flowability prohibits the usage of nanopowder in ceramic binder jetting. In this study, to improve the flowability of nanopowder, alumina nanoparticles were granulated into micron-sized granules through spray freeze drying. The raw nanopowder and granulated powder were compared by characterizing their flowability and printability. Results showed that the granulated powder had a much better flowability than the raw nanopowder. Because of the superior flowability, the granulated powder formed a denser and smoother powder bed than the raw nanopowder and resulted in denser and smoother printed and sintered samples. These improvements indicated that the printability of nanopowder was improved by granulation.

This paper investigates the effect of heat treatment on the magnetic properties of nanocrystalline Fe-Ni-Si powders prepared by mechanical alloying method which can be used in soft magnetic composites fabrication. Fe-85%, Si-10% and Ni-5% alloys were prepared using a vibrating disc mill. The magnetic properties of the samples were measured by a vibrating sample magnetometer (VSM) and the microstructural properties of the un annealed sample were measured by XRD and SEM. Three samples were annealed in three different temperatures from 500 °C to 600 °C and were compared with a sample without annealing. It was found that with increasing the annealing temperature, stress relieving and crystallite size increased whereas microstrain and saturation magnetization decreased.

In general, melting process is not a common method for the production of oxide dispersion strengthened (ODS) alloys due to agglomeration and coarsening of oxide particles. However, vacuum casting process has recently been employed as a promising process to produce micro-scale oxide dispersed alloys. In this paper, we report the process and characterization of in situ formation and uniform dispersion of nano-scale Y-Ti oxide particles in Fe-10Ni-7Mn (wt.%) alloy. The processing route involves a solid-liquid reaction between the added TiO2 as an oxygen carrier and dissolved yttrium in liquid metal leading to an optimal microstructure with nano-sized dispersed oxide particles. The developed thermodynamic model shows the independence of the final phase constituents from experimental conditions such as melting temperature or vacuum system pressure which offers a general pathway for the manufacture of oxide dispersion strengthened materials.