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Laser powder bed fusion (LPBF) is a fusion-based additive manufacturing process. It has the advantage of allowing the manufacturing of metal matrix composites. This advantage arises from its small melting zone and rapid cooling rate, which minimize the risk of reinforcement segregation. In this work, 0.3 wt% and 1.0 wt% Y2O3 nanoparticles were added to 316L to fabricate oxide dispersion-strengthened (ODS) steels using the LPBF process. Notably, Y2O3 agglomerates were identified in the LPBF-fabricated 316L ODS steels, without inducing grain refinement, while the impact on tensile strength of Y2O3 addition proved negligible. Tensile elongation was decreased due to the poor bonding of the Y2O3 agglomerations to the matrix. The crucial role of the wettability of the reinforcement and the matrix in facilitating grain refinement and strength enhancement is discussed. The poor wettability of the Y2O3 particles and 316L emerged as the primary cause for Y2O3 agglomeration. This finding highlights the importance of addressing wettability issues to optimize the manufacturing process and enhance the overall performance of LPBF-fabricated metal matrix composites. [ABSTRACT FROM AUTHOR]

Here we demonstrate direct ink write (DIW) additive manufacturing of carbon nanotube (CNT)/phenolic composites with heat dissipation and excellent electromagnetic interference (EMI) shielding capabilities without curing-induced deformation. Such polymer composites are valuable for protecting electronic devices from overheating and electromagnetic interference. CNTs were used as a multifunctional nanofiller to improve electrical and thermal conductivity, printability, stability during curing, and EMI shielding performance of CNT/phenolic composites. Different CNT loadings, curing conditions, substrate types, and sample sizes were explored to minimize the negative effects of the byproducts released from the cross-linking reactions of phenolic on the printed shape integrity. At a CNT loading of 10 wt %, a slow curing cycle enables us to cure printed thin-walled CNT/phenolic composites with highly dense structures; such structures are impossible without a filler. Moreover, the electrical conductivity of the printed 10 wt % CNT/phenolic composites increased by orders of magnitude due to CNT percolation, while an improvement of 92% in thermal conductivity was achieved over the neat phenolic. EMI shielding effectiveness of the printed CNT/phenolic composites reaches 41.6 dB at the same CNT loading, offering a shielding efficiency of 99.99%. The results indicate that high CNT loading, a slow curing cycle, flexible substrates, and one thin sample dimension are the key factors to produce high-performance 3D-printed CNT/phenolic composites to address the overheating and EMI issues of modern electronic devices.