Texture and High Yield Strength of Rapidly Solidified AZ31 Magnesium Alloy Extruded at 250 °C.

In this study, commercial AZ31B magnesium alloy was used to compare the differences between the microstructure, texture, and mechanical properties of conventional solidification (as homogenized AZ31) and rapid solidification (as RS AZ31). The results demonstrate that a rapidly solidified microstructure leads to better performance after hot extrusion with a medium extrusion rate (6 m/min) and extrusion temperature (250 °C). The average grain size of as-homogenized AZ31 extruded rod is 100 µm after annealing and 4.6 µm after extrusion, respectively, but that of the as-RS AZ31 extruded rod is only about 5 µm and 1.1 µm, correspondingly. The as-RS AZ31 extruded rod attains a high average yield strength of 289.6 MPa, which is superior to the as-homogenized AZ31 extruded rod, and is improved by 81.3% in comparison. The as-RS AZ31 extruded rod shows a more random crystallographic orientation and has an unconventional weak texture component in <112¯1>/<202¯1> direction, which has not been reported yet, while the as-homogenized AZ31 extruded rod has an expected texture with prismatic <101¯0>/<1¯21¯0>//ED.

Microstructure and Air Trace Defects of the Rapidly Solidified ZK60 Magnesium Alloy Ribbon.

ZK60 alloy metal ribbons were prepared successfully in a carbon dioxide atmosphere by varying the speeds of melt spinning. The thin metal ribbon with different solidification speeds was prepared by controlling different rotation speeds, and the influence of solidification speed on the ZK60 ribbon was studied. The results show that the gas mark has a significant effect on the local structure of the ribbon. The gas mark's proportional area of the ZK60 ribbon increases first and then decreases with the increase in roll speed, and the gas mark proportion area is the smallest at 17.6 m/s. With the increase in the solidification rate, the base texture of the ribbon is enhanced, and the proportion of columnar crystals in the ribbon gradually increases. At the rate of 17.6 m/s, columnar crystals run through the entire side of the ribbon, and uniformly distributed spherical-particle phases are found inside the grain. At the speed of 17.6 m/s, the mechanical properties of different areas of the ribbon are close and different from those of the other two speeds, and the performance of the quenching zone is better than that of the slow-cooling zone.

Visualization of Type-J counter current chromatography: Hydrodynamic behavior in a helical column.

In counter-current chromatography (CCC), the hydrodynamic motion of a two-phase solvent system in the column/coil is very important. There are some previous visualization studies on CCC using stroboscopic photography. As CCC separation is a continuous liquid-liquid extraction process, observing the distribution and movement of the solvent system on-line will be helpful to understand the hydrodynamic behavior during the whole CCC separation process. In the present study, a high-speed imaging camera was employed to take videos of a running CCC bobbin (visualized continuously on-line). The dynamic motion and phase distribution of conventional quaternary solvent system hexane/ethyl acetate/methanol/water (HEMWat) and ternary solvent system dichloromethane/methanol/water were both investigated. Wave-like mixing was observed in the area where the centrifugal force is minimum in different diameter columns. When the coil rotated, the mixing zone was "fixed" at the minimum centrifugal force position. Several photographs of the rotating coiled tube were taken which revealed that the phase dispersion hardly changes once equilibrium is established. Finally, the sample dispersion process was also recorded. These results will help us to understand the separation process in a CCC column/coil and also present some more interesting questions related to separation efficiency which are shown in discussion part of this paper.

Silver Nanoparticles Modified with Sodium Triphosphate: Antibacterial Activity, Hemocompatibility and Cytotoxicity.

In this study, we report silver nanoparticles (Ag NPs) modified with sodium triphosphate (STTP) (Ag-STPP NPs) prepared by a simple surface modification and chemical reduction method. It was confirmed by 31P NMR spectroscopy that STPP was successfully introduced to the surface of Ag NPs. It was revealed by conductivity change measurements, bacterial growth kinetics and antibacterial efficiency tests that Ag-STPP NPs still retained the strong antibacterial ability. It was demonstrated by hemolysis assays, red blood cell morphology measurements, plasma recalcification time and in vitro clotting times that Ag-STPP NPs had improved hemocompatibility. It was also implied by cell viability measurements that Ag-STPP NPs possessed low cytotoxicity and high cytocompatibility. These findings, combined with the low-cost and ease of synthesis, make Ag-STPP NPs a promising candidate for biomedical applications.