Quality assurance is an important topic for additive manufacturing (AM) and often seen as a requirement for the transition and adoption of the technology toward fabrication of end use applications. As AM technologies are used for production, it is necessary to ensure high quality, repeatable, and reproducible components are manufactured. Various nondestructive examination techniques have been used to evaluate AM-fabricated parts to determine part quality post-fabrication (e.g. scanning and/or microstructural characterization). In situ monitoring methods have been developed for AM technologies to enable defect detection and have potential to be used for in situ monitoring and correction of fabrication anomalies (e.g. undesired temperature gradients and porosity). In this research, defects (e.g. pores) were seeded into parts fabricated using the powder bed fusion AM process, electron beam melting, and monitored using in situ infrared (IR) thermography. Results from layerwise thermography were compared with results obtained using computer tomography (CT) scanning techniques. Although the measured geometry of the seeded defects between IR thermography and CT was substantially different (area difference of ∼60%), the thermographs did provide a good indication of defects present within a fabricated part. Furthermore, defect correction methods were evaluated including post-processing methods such as hot isostatic pressing as well as in situ correction methods such as layer re-melting. Re-melting a porous layer successfully corrected defects and demonstrates a potential method for in situ defect correction if implemented in future systems equipped with automatic feedback control of powder bed fusion processes.
Lithium-ion batteries (LIB) have been receiving extensive attention because of the high specific energy density for wide applications such as electronic vehicles, commercial mobile electronics, and military applications. In LIB, graphite is the most commonly used anode material; however, lithium-ion intercalation in graphite is limited, hindering the battery charge rate and capacity. To overcome this obstacle, nanostructured anode assembly has been extensively studied to increase the lithium-ion diffusion rate. Among these approaches, high specific surface area metal oxide nanowires connecting nanostructured carbon materials accumulation have shown propitious results for enhanced lithium intercalation. Recently, nanowire/graphene hybrids were developed for the enhancement of LIB performance; however, almost all previous efforts employed nanowires on graphene in a random fashion, which limited lithium-ion diffusion rate. Therefore, we demonstrate a new approach by hydrothermally growing uniform nanowires on graphene aerogel to further improve the performance. This nanowire/graphene aerogel hybrid not only uses the high surface area of the graphene aerogel but also increases the specific surface area for electrode-electrolyte interaction. Therefore, this new nanowire/graphene aerogel hybrid anode material could enhance the specific capacity and charge-discharge rate. Scanning electron microscopy (SEM) and X-ray diffraction (XRD) are used for materials characterization. Battery analyzer and potentio-galvanostat are used for measuring the electrical performance of the battery. The testing results show that nanowire graphene hybrid anode gives significantly improved performance compared to graphene anode.
We report the discovery of a new (S)-3-aminopyrrolidine series of CCR2 antagonists. Structure-activity relationship studies on this new series led to the identification of 17 (INCB8761/PF-4136309) that exhibited potent CCR2 antagonistic activity, high selectivity, weak hERG activity, and an excellent in vitro and in vivo ADMET profile. INCB8761/PF-4136309 has entered human clinical trials.
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