Using ab initio calculations we have computed the lattice constants, bulk moduli, and local and total density of states of the MAX phases, Ti 2 TlC, Zr 2 TlC, and Hf 2 TlC in the hexagonal P6 3 / mmc space group. The results for lattice constants are within 2% of experimental results. The bulk moduli are predicted to be 125, 120, and 131 GPa, respectively. These are the lowest values of bulk moduli among all MAX phases studied to date. The electronic density of states shows that all three materials are conducting. These low values of their bulk moduli are attributed to weak metal M ͑M=Ti,Zr,Hf͒ bonding with the A element thallium.

In the medical device industry, angioplasty balloons have been widely used in the less invasive treatment of heart disease by expanding and relieving clogged structures in various arterial segments. However, new applications using thin coatings on the balloon surface have been explored to enhance therapeutic value in the delivery of pharmaceuticals (drug-elution) or control thermal energy output (RF ablation). In this study, angioplasty balloon materials comprised of poly(ether-block-amide) (Pebax) were investigated via atomic force microscopy (AFM), transmission electron microscopy (TEM), scanning electron microscopy (SEM), and small-angle X-ray scattering (SAXS) to characterize physical properties at the balloon surface that may affect coating adhesion. The soft segment of this Pebax 1074 material is polyethylene oxide (PEO) and the hard segment is nylon-12. The morphology of the hard segments of this block co-polymer are found via AFM stiffness measurements to be (40 ± 20) nm by (300 ± 150) nm and are oriented parallel to the surface of the balloon. SAXS measurements found the lamellar spacing to be (18.5 ± 0.5) nm, and demonstrate a preferential orientation in agreement with TEM and AFM measurements. Fixation of this balloon in resin, followed by cryo-sectioning is shown to provide a novel manner in which to investigate surface characteristics on the balloon such as material or coating thickness as well as uniformity in comparison to the bulk structure. These outputs were deemed critical to improve overall balloon processing such as molding and surface treatment options for robust designs toward better procedural outcomes targeting new therapeutic areas.

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In this work, the microstructure and texture evolution of the strip cast Nd−Fe−B flake has been systematically investigated by correlating multiple state-ofthe-art characterization techniques. We found that (i) besides the existence of random ultrafine equiaxed grains at the wheel side of the flake, elongated (001) textured grains were formed into a V-shape zone between neighboring nucleation sites, which possibly resulted from the in-plane growth of the low energy preferred growth direction of grains (a axis). Both ultrafine random equiaxed grains and elongated (001) textured grains are detrimental to achieving a high-performance Nd− Fe−B magnet, due to the inhomogeneous grain shape and nonuniform distribution of rare earth-rich phase within these grains or along the grain boundaries, which deteriorate the alignment of the Nd−Fe−B powders in the subsequent hydrogen decrepitation process and jet milling procedure. To overcome the issues mentioned above, two potential approaches are proposed, which are increasing the nucleation rate on the wheel side and homogenization of rare earth-rich phase within grains or along grain boundaries; (ii) columnar grains containing (Nd,Pr) 2 Fe 14 B lamellae with an average spacing of ∼5 μm and discontinuous rare-earth rich phase were formed in the remaining part of the flake. Accordingly, a model in terms of the microstructure and texture evolution was proposed.

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