Effect of Hot Isostatic Pressing and Solution Heat Treatment on the Microstructure and Mechanical Properties of Ti-6Al-4V Alloy Manufactured by Selective Laser Melting

A powder-bed-based additive manufacturing process called electron beam melting (EBM) is defined by high temperature gradients during solidification, which produces an extremely fine microstructure compared to the traditional cast material. However, porosity and segregation defects are still present on a smaller scale which may lead to a reduction in mechanical properties. It is important to have a better knowledge of the influence of post-fabrication treatments on the microstructure and mechanical characteristics before the use of additive manufacturing parts in specific applications. In this study, the effects of solution heat treatment (SHT) and hot isostatic pressing (HIP) on the microstructure and mechanical properties of Ti-6Al-4V alloy fabricated by the EBM process have been investigated. The SHT and HIP treatments can significantly improve the ductility of EBM Ti-6Al-4V due to the coarsening of α laths and the formation of β grains

Reinforcement of binder adhesion for nickel-rich layered oxide in lithium-ion batteries using perfluorinated molecular surface modification

Ni-rich layered oxides are considered the most promising candidates for cathode materials for use in electric vehicles because of their high energy density and low cost. However, the cyclability of Ni-rich layered oxide needs to be improved because it suffers from contact loss by microcracks owing to the large anisotropic volume changes during cycling. Furthermore, its unstable surface, which releases lithium impurities by water contamination, must also be mitigated. To improve the adhesive force with a polyvinyl fluoride (PVdF) binder as well as the air-stability, a self-assembled monolayer of 1H,1H-2H,2H-perfluorodecyltriethoxysilane (PFDTES) is introduced onto the surface of Ni-rich layered oxide cathode powder. A molecular functional monolayer with fluorocarbons on Ni-rich layered oxide powder is delivered to achieve an ~ 13 angstrom thin homogeneous molecular-level functional coating at a negligible weight ratio. The functionalized surface improves the adhesion between PVdF and cathode powder by FMIDLINE HORIZONTAL ELLIPSISF interaction, relieving the electrode detachment. As a result, cycling failure mode is remarkably mitigated. The fluorinated hydrophobic surface alleviates water contamination, thereby reducing lithium impurities.N

Mass-Scalable Molecular Monolayer for Ni-Rich Cathode Powder: Solution for Microcrack Failure in Lithium-Ion Batteries

Ni-rich layered oxide with high reversible capacity, low manufacturing cost, and high potential is recognized as the best practical cathode material for high energy density lithium-ion batteries for affordable electric vehicles. However, they suffer from a poor cycle life owing to internal microcracks, which have been perceived to be due to anisotropic volume changes. Herein, the failure mechanism as well as improved cycle life is demonstrated by a self-assembled molecular monolayer (SAM) on Ni-rich layered oxide powder with a gas-phase precursor of octyltrichlorosilane (OTS), enabling mass-scalable manufacturing. The SAM process with a low heating temperature of 130 degrees C compared to the commonly used coating is also suitable to the chemically fragile Ni-rich layered oxide. Also, a homogeneous angstrom-level OTS coating is beneficial for preserving the energy density of batteries. In particular, OTS, with electrolyte-phobic functionality, is very effective for mitigating the inherent microcrack failure of the particles by reducing the internal electrolyte decomposition by controlling electrolyte wetting into secondary particles. Systematic surface analyses of the cross section of Ni-rich electrode with the OTS coating found greatly improved particle stability after 100 cycles in comparison with pristine material.

Polyhydroxyalkanoate Decelerates the Release of Paclitaxel from Poly(lactic-co-glycolic acid) Nanoparticles

Biodegradable nanoparticles (NPs) are preferred as drug carriers because of their effectiveness in encapsulating drugs, ability to control drug release, and low cytotoxicity. Although poly(lactide co-glycolide) (PLGA)-based NPs have been used for controlled release strategies, they have some disadvantages. This study describes an approach using biodegradable polyhydroxyalkanoate (PHA) to overcome these challenges. By varying the amount of PHA, NPs were successfully fabricated by a solvent evaporation method. The size range of the NPS ranged from 137.60 to 186.93 nm, and showed zero-order release kinetics of paclitaxel (PTX) for 7 h, and more sustained release profiles compared with NPs composed of PLGA alone. Increasing the amount of PHA improved the PTX loading efficiency of NPs. Overall, these findings suggest that PHA can be used for designing polymeric nanocarriers, which offer a potential strategy for the development of improved drug delivery systems for sustained and controlled release

Ultrathin ZnS and ZnO Interfacial Passivation Layers for Atomic-Layer-Deposited HfO₂ Films on InP Substrates

Ultrathin ZnS and ZnO films grown by atomic layer deposition (ALD) were employed as interfacial passivation layers (IPLs) for HfO₂ films on InP substrates. The interfacial layer growth during the ALD of the HfO₂ film was effectively suppressed by the IPLs, resulting in the decrease of electrical thickness, hysteresis, and interface state density. Compared with the ZnO IPL, the ZnS IPL was more effective in reducing the interface state density near the valence band edge. The leakage current density through the film was considerably lowered by the IPLs because the film crystallization was suppressed. Especially for the film with the ZnS IPL, the leakage current density in the low-voltage region was significantly lower than that observed for the film with the ZnO IPL, because the direct tunneling current was suppressed by the higher conduction band offset of ZnS with the InP substrate

Atomic scale identification of nano-sized precipitates of Ta/Ti-added RAFM steel and its superior creep strength

The influence of 0.015 wt% Ti addition on the formation of MX precipitates and the creep resistances of a reduced activation ferritic/martensitic (RAFM) steel has been studied. 0.1 wt% Ta was also added as same as conventional RAFM steels. Transmission electron micrographs taken from extraction replicas indicated that the area fraction of MX particles in Ta/Ti-added RAFM steel was 2.3 times higher than that in the reference steel. Atom probe tomography was employed to identify the types of MX precipitates and their interactive distribution. By using isoconcentration surfaces with different elemental concentration values, it was newly found that there are three types of MX precipitates, i.e. (Ta,V)-rich MX, Ti-rich MX and W-rich MX in the Ta/Ti-added RAFM steel. They appeared to be distributed independently in the matrix. However, in some cases, smaller sized (Ti or W)-rich MX particles were in contact with large (Ta,V)-rich MX particle. The creep rupture life of the Ta/Ti-added RAFM steel was significantly improved, as compared with the reference steel. The enhanced creep resistance can be rationalized in terms of a high density of dislocations, which were produced by a strong interaction with a higher fraction of the nano-sized MX particles within laths. © 2020 Elsevier Inc.FALS