Surface-modified polyacrylonitrile nanofibers as supports

Polyacrylonitrile nanofibers (PAN-nfs) are one of the most studied nanofibres because of their excellent characteristics, such as good mechanical strength, chemical resistance, and good thermal stability. Due to the easy dissolution in polar organic solvents, PAN-nfs are mostly produced via electrospinning technique. The electrospun PAN-nfs surfaces are relatively in-active and hydrophobic, and, therefore, hinder some potential applications; however, chemical surface modification reactions, such as amination, reduction, hydrolysis, and amidoximation, have been carried out on them. These reactions bring about functional groups, such as amine, hydroxyl, carboxylic, imine etc, to the surface PAN-nfs and invariably make their surfaces active and hydrophilic. The surface-modified PAN-nfs have been used as supports for organic compounds, enzymes, and antibodies in biological studies. They have also been used for immobilization of various organic ligands for adsorption of metal ions in water. Furthermore, because of their ability to complex metal ions, several surface-modified PAN-nfs have also been used as supports for transition metal catalysts in Fenton’s chemistry.IS

Effect of build location on microstructural characteristics and corrosion behavior of EB-PBF built Alloy 718

Electron beam-powder bed fusion (EB-PBF), a high-temperature additive manufacturing (AM) technique, shows great promise in the production of high-quality metallic parts in different applications such as the aerospace industry. To achieve a higher build efficiency, it is ideal to build multiple parts together with as low spacing as possible between the respective parts. In the EB-PBF technique, there are many unknown variations in microstructural characteristics and functional performance that could be induced as a result of the location of the parts on the build plate, gaps between the parts and part geometry, etc. In the present study, the variations in the microstructure and corrosion performance as a function of the parts location on the build plate in the EB-PBF process were investigated. The microstructural features were correlated with the thermal history of the samples built in different locations on the build plate, including exterior (the outermost), middle (between the outermost and innermost), and interior (the innermost) regions. The cubic coupons located in the exterior regions showed increased level (~ 20 %) of defects (mainly in the form of shrinkage pores) and lower level (~ 30-35 %) of Nb-rich phase fraction due to their higher cooling rates compared to the interior and middle samples. Electrochemical investigations showed that the location indirectly had a substantial influence on the corrosion behavior, verified by a significant increase in polarization resistance (Rp) from the exterior (2.1 ± 0.3 kΩ.cm2) to interior regions (39.2 ± 4.1 kΩ.cm2). © 2020, The Author(s)