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Although there have been extensive studies on CoCrFeNi high entropy alloys (HEAs), they are still far from industrial applications due to their inferior strength. Based on the approach of interstitial atom strengthening which has been shown to be one of the effective ways to modify the properties of metallic materials, a series of (CoCrFeNi)100-xNx (x = 0, 0.25 and 0.50 at. %) HEAs were prepared in this study by selective laser melting (SLM). It was found that nitrogen addition in CoCrFeNi HEA can slightly refine the microstructure but did not change the preferred orientations after SLM. By increasing the nitrogen content in the matrix, the strength increases while the ductility is reduced. Also, the addition of nitrogen in CoCrFeNi HEA can decrease the stacking fault probability, leading to the increased stacking fault energy (SFE) in N-doped CoCrFeNi HEA. The increased strength in N-doped CoCrFeNi HEA samples mainly attributes to the solid solution strengthening of nitrogen, whereas the ductility loss results from the impediment on the formation of deformed twins induced by increased SFE. These results can provide a new strategy for designing high-strength N-doped HEAs.

The main risk of tissue-engineered implant materials is the stimulation of exogenous materials to the body. In order to reduce immune rejection and promote the growth of autologous cells, we attempted in vitro matrix formation by culturing human aorta smooth muscle cells (SMCs) in a silk fibroin (SF) porous scaffold, and investigated the synthesis and deposition of extracellular matrix (ECM) components in scaffolds, including collagen-I, collagen-III and elastin. We also investigated the regulatory effect of transforming growth factor β1 (TGF-β1). SMCs displayed higher survivability and proliferation after treatment with TGF-β1 than untreated controls at 1 week after inoculation. SMCs in the SF scaffolds exhibited efficient synthesis of ECM-related proteins. All three proteins were deposited in scaffolds, and this was promoted by treatment with TGF-β1. Incipient expression of collagen-III was lower than that of elastin and collagen-I, but it was increased significantly at 2 weeks. The phenotype of SMCs in SF scaffolds changed from a synthetic phenotype to a contraction phenotype after inoculation for 2 weeks. However, treatment with TGF-β1 slowed down this phenotypic transformation, and enhanced the ECM protein synthesis ability. This method could potentially be used for a wide range of polymers where specific architectures and microenvironments are required.

Synthetic dyes have caused serious ecological and environmental threats in our daily lives. Effective and inexpensive dye-degradation methods are desperately perused for decades. In this work, ultrasonic-vibration treatment is found as an effective approach that can dramatically improve the degradation performance of industrial Fe78Si9B13 amorphous powders towards methylene blue. As demonstrated by synchrotron X-ray nano-computed tomography and scanning electron microscope combined with X-ray photoelectron spectroscopy, the micro-channels on the surface or inside of Fe78Si9B13 particles offer a shortcut for fast mass transfer and supply plenty of reactive sites with low density and high energy due to the structural rejuvenation after ultrasonic vibration. It leads to the reduction of the reaction activation energy of degradation under the pseudo-first-order kinetic model and an exceptional decomposition capacity. Our work not only extremely drives down the current costs of wastewater treatments, but also provides a promising approach for tuning the effectivity of alloying catalysts via manipulating the potential energy state of metallic glasses based on the high-frequency mechanical vibration technique.

A novel Fe39Ni39B12.82Si2.75Nb2.3P4.13 bulk metallic glass (BMG) with high notch toughness of 72.3 MPa m1/2, large plastic strain of 9.8%, high yield strength of 2930 MPa, and a large critical diameter of 2.5 mm was successfully developed. This BMG also exhibits excellent soft magnetic properties, i.e., higher saturation magnetic flux density of 0.86 T, extremely low coercivity of 0.65 A/m, and high effective permeability of 23,250 with high frequency stability. Its toughness value is the highest among Fe-based BMG family. The origin of high toughness was also investigated in detail by using synchrotron X-ray diffraction and aberration-corrected high-resolution transmission electron microscopy. It was found that the high toughness are attributed to atomic-scale structural heterogeneity that resulted from large free volume, high content of metal-metal bonds and high structural disorder degree, which can promote the multiple shear bands and hinder the subsequently propagation. This work provides useful guidelines for developing tough FeNi-based BMGs with high strength and excellent soft magnetic properties from an atomic structural perspective.