IRON PYRITE NANOCRYSTALS

An apparatus includes a nanocrystal. The nanocrystal includes a core including FeS2; and a coating including a ligand component capable of chemically interacting with both an iron atom and a sulfur atom on a surface of the core

Optimization of the Kinematic Model for Biomimetic Robotic Fish with Rigid Headshaking Mitigation

Biomimetic robotic fish is a new type of underwater robot with many superior characteristics such as high movement speed, high motion efficiency, high energy efficiency, and so on. However, the traditional kinematic model for biomimetic robotic fish has many shortcomings which limit their movement speed, such as the rigid shakes of the fish’s head when it swims, which is caused by neglecting the influences of manufacturing process on the model. In order to mitigate the rigid headshaking, a revised kinematic model is proposed by introducing an offset of the joints rotation center. The proposed kinematic equations are well simulated in a MATLAB environment, and the numerical results illustrate the advantage of the new kinematic model. Finally, experimental results generated from a three-joint biomimetic robotic fish with the proposed model show that the fish’s head shaking is effectively restrained, and therefore the swimming speed is significantly improved

Effect of compressive load on texture evolution and anisotropic behavior of dual-phase steel under biaxial loading in complete σ11-σ22 space

Advanced high strength steels (AHSS) are typically loaded in a multiaxial stress state during forming process and service. However, the deformation mechanism under multiaxial loading is not clarified, which limits the optimization of sheet metal forming. In particular, due to instability, biaxial compression loading of single thin plate has not been reported, which results in unclear evolution of the yield surfaces in the second, third and fourth quadrants of σ11-σ22 space and corresponding deformation mechanisms. Therefore, the deformation mechanism of AHSS thin plates under biaxial loading was systematically investigated in the complete σ11-σ22 space using a specially designed cruciform specimen and buckling prevention fixture in the current work. The mechanical properties of dual-phase (DP780) steel under different loading paths were studied by uniaxial tension, uniaxial compression, and biaxial loading tests. There is an obvious yield strength difference between the first quadrant and the third quadrant in the σ11-σ22 space. In the second and fourth quadrants of σ11-σ22 space, the compression part makes a greater effect on the yield behavior of the material than the tension part. More specifically, dislocation slip is activated earlier at the boundary under compression loading, resulting in earlier yielding of the material. Based on the analysis of the Taylor factor, the activation of slip systems of DP780 steel before and after deformation is clarified. In addition, a detailed analysis of the microstructure and texture evolution in DP780 steel after deformation is conducted, and a correlation between texture evolution and loading paths is established. It is found that the compression part under biaxial loading results in more grains with low Taylor factor and promotes the transformation of the initial texture to copper or rotated copper texture in DP780 steel

Coupled Thermomechanical Responses of Zirconium Alloy System Claddings under Neutron Irradiation

Zirconium (Zr) alloy is a promising fuel cladding material used widely in nuclear reactors. Usually, it is in service for a long time under the effects of neutron radiation with high temperature and high pressure, which results in thermomechanical coupling behavior during the service process. Focusing on the UO2/Zr fuel elements, the macroscopic thermomechanical coupling responses of pure Zr, Zr-Sn, and Zr-Nb binary system alloys, as well as Zr-Sn-Nb ternary system alloy as cladding materials, were studied under neutron irradiation. As a heat source, the thermal conductivity and thermal expansion coefficient models of the UO2 core were established, and an irradiation growth model of a pure Zr and Zr alloy multisystem was built. Based on the user material subroutine (UMAT) with ABAQUS, the current theoretical model was implemented into the finite element framework, and the consequent thermomechanical coupling behavior under irradiation was calculated. The distribution of temperature, the stress field of the fuel cladding, and their evolution over time were analyzed. It was found that the stress and displacement of the cladding were sensitive to alloying elements due to irradiated growth

Near-Infrared Emitting AgInS₂/ZnS Nanocrystals

Near-infrared emitting AgInS₂/ZnS nanocrystals were synthesized by carefully controlling the growth conditions in a Ag/In/Zn/S solution with less zinc relative to the other precursors. The role of having a smaller amount of zinc (8 atom %) was systematically investigated in an effort to understand the mechanism of the largely red-shifted emission. The AgInS₂/ZnS nanocrystals can be transferred to aqueous solutions while retaining the emission intensity. The near-infrared emission and solubility in aqueous solutions make AgInS₂/ZnS nanocrystals excellent candidates for bioimaging and photocatalytic applications

One-Step Nickel Foam Assisted Synthesis of Holey G‑Carbon Nitride Nanosheets for Efficient Visible-Light Photocatalytic H₂ Evolution

Graphitic carbon nitride (g-C₃N₄) with layered structure represents one of the most promising metal-free photocatalysts. As yet, the direct one-step synthesis of ultrathin g-C₃N₄ nanosheets remains a challenge. Here, few-layered holey g-C₃N₄ nanosheets (CNS) were fabricated by simply introducing a piece of nickel foam over the precursors during the heating process. The as-prepared CNS with unique structural advantages exhibited superior photocatalytic water splitting activity (1871.09 μmol h^–1 g^–1) than bulk g-C₃N₄ (BCN) under visible light (λ > 420 nm) (≈31 fold). Its outstanding photocatalytic performance originated from the high specific surface area (240.34 m² g^–1) and mesoporous structure, which endows CNS with more active sites, efficient exciton dissociation, and prolonged charge carrier lifetime. Moreover, the obvious upshift of the conduction band leads to a larger thermodynamic driving force for photocatalytic proton reduction. This methodology not only had the advantages for the direct and green synthesis of g-C₃N₄ nanosheets but also paved a new avenue to modify molecular structure and textural of g-C₃N₄ for advanced applications

Study of the Partial Ag-to-Zn Cation Exchange in AgInS₂/ZnS Nanocrystals

AgInS₂–ZnS (AIZS) nanocrystals (NCs) were synthesized using a simple one-step approach by heating a Ag/In/Zn/S solution to 210 °C providing highly tunable photoluminescence (PL). The incorporation of Zn even at low temperatures (∼150 °C) and the increased cation exchange of silver by zinc at higher temperatures strongly influence the optical properties of the resulting NCs. The correlation between synthesis parameters and resulting optical properties provided insights on the growth and stability of ternary and quaternary semiconductors. Systematic investigation with time-resolved spectroscopy showed distinguishable PL behaviors between developing and fully grown AIZS NCs. Attempts to coat as-prepared AgInS₂ NCs resulted in the same PL behavior as the one-step reaction product indicating that Zn readily exchanges with Ag ions even when not directly incorporated in the initial reaction mixture. Even with a low amount of zinc, the fully grown AIZS NCs showed improved PL QYs and single exponential decay behavior with long PL lifetimes. Control of the optical properties of these NCs makes them potentially useful for applications in photovoltaics and bioimaging particularly in light of their nontoxicity