Magnetic Ni micro/nanostructures with controlled morphology have drawn intensive attention due to their interesting physicochemical properties and potential applications in micro/nanodevices. In this study, one-dimensional Ni nanochains with an average diameter of about 140 nm were prepared by a magnetic-¯eld-assisted chemical reduction of Ni 2þ with hydrazine hydrate free of any template or surfactant. It was found that the morphology and the size of the Ni chains could be adjusted by changing the complexant used in the synthesis. The usage of surfactant in the synthesis would retard the¯rm connection of Ni nanoparticles and thus resulted in the formation of Ni nanochains consisting of loosely aggregated Ni nanoparticles. The magnetic measurement at room temperature indicated that the coercivity of the Ni sample reached 133.2 Oe, which was much higher than that of bulk Ni metal.

Flowerlike Ni microcrystals composed of star-shaped Ni nanorods with a diameter of ~200 nm were fabricated by a facile chemical reduction process, in which ethylenediamine tetraacetic acid sodium (EDTA) was used as complexant to assist in the formation of the flowery shape of the sample. The products were characterized by X-ray diffractometer, scanning electron microscopy, energy-dispersive X-ray spectroscopy and superconducting quantum interference device magnetometer. Scanning electron microscopy images indicated the typical size of the flowery Ni microcrystals was 2–3 μm and the length of the star-shaped Ni nanorods was in the hundreds of nanometers up to micron scale. The X-ray diffraction pattern showed the Ni microcrystals were present in the face-centred cubic phase and magnetic measurement results demonstrated the greatly enhanced coercivity of the sample (168.5 Oe) at room temperature. Based on the evolution of the structure and the morphology of products with increasing reaction time, a possible formation mechanism was proposed to illustrate the growth of the flower-like Ni architecture.

The interactions between the energetic particles and atoms in materials would result in the atomic displacements and the associated radiation defects. The interstitial dislocation loop, as one of the primary radiation defects, is formed by the clustering of the supersaturated self-interstitial atoms from the displacement damages in body centered cubic (bcc) iron based materials. The radiation hardening, embrittlement, swelling, creep, etc. are generally related to these loops and their interactions with other defects. In addition, the irradiation would also result in the formation of the micro-cracks from the surface of the materials and also from the interface of grains, precipitates, and gas-bubbles inside the materials, which would result in the irradiation assisted stress corrosion crack (IASCC). Therefore, to understand the interaction between interstitial dislocation loop and micro-crack under the irradiation, is one of key steps to understand the underlying mechanism of IASCC. In this work, the interaction between interstitial dislocation loop and micro-crack is simulated by molecular dynamics method on an atomic scale. The distance, relative position between them and radius of dislocation loop, as the main factors affecting their interactions, are studied to explore the underlying reason for inducing the micro-crack to expand on the slip plane. The simulation results indicate that when the interaction between them dominates the whole process with the distance between them within the critical value, the dislocation network containing the <inline-formula><tex-math id="Z-20200522122407-1">\begin{document}$ \langle 100 \rangle $\end{document}</tex-math><alternatives><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="11-20200317_Z-20200522122407-1.jpg"/><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="11-20200317_Z-20200522122407-1.png"/></alternatives></inline-formula> and 1/2<inline-formula><tex-math id="Z-20200522122407-2">\begin{document}$ \langle 111 \rangle $\end{document}</tex-math><alternatives><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="11-20200317_Z-20200522122407-2.jpg"/><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="11-20200317_Z-20200522122407-2.png"/></alternatives></inline-formula> segments, would interact with the crack tip to inhibit the crack from expanding through the pinning effect. When the size of loop is different, the pining effect would be available only when the interaction between loop core and crack tip dominates with the distance between them within the critical value. All these results provide new understanding for further exploring the IASCC under irradiation.

Formation and evolution of interstitial dislocation loop induced by radiation damage in a material are confirmed to seriously affect the performance of the material under irradiation. For example, in body-centered cubic Fe based alloy, 1/2<inline-formula><tex-math id="Z-20191230113253">\begin{document}$\left\langle 111 \right\rangle $\end{document}</tex-math><alternatives><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="3-20191379_Z-20191230113253.jpg"/><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="3-20191379_Z-20191230113253.png"/></alternatives></inline-formula> and <inline-formula><tex-math id="Z-20191230113318">\begin{document}$\left\langle 100 \right\rangle $\end{document}</tex-math><alternatives><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="3-20191379_Z-20191230113318.jpg"/><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="3-20191379_Z-20191230113318.png"/></alternatives></inline-formula> are mainly formed during the irradiation, which is related to various degradations of material properties. Thus, the understanding of their effect on radiation damages of material is always one of the hottest topics in nuclear material society. Previous studies have shown the surface effect on 1/2<inline-formula><tex-math id="Z-20191230113405">\begin{document}$\left\langle 111 \right\rangle $\end{document}</tex-math><alternatives><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="3-20191379_Z-20191230113405.jpg"/><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="3-20191379_Z-20191230113405.png"/></alternatives></inline-formula> loop through the investigation of the interaction between 1/2<inline-formula><tex-math id="Z-20191230113300">\begin{document}$\left\langle 111 \right\rangle $\end{document}</tex-math><alternatives><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="3-20191379_Z-20191230113300.jpg"/><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="3-20191379_Z-20191230113300.png"/></alternatives></inline-formula> loop and {111} surface. Considering the difference in property between 1/2<inline-formula><tex-math id="Z-20191230113308">\begin{document}$\left\langle 111 \right\rangle $\end{document}</tex-math><alternatives><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="3-20191379_Z-20191230113308.jpg"/><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="3-20191379_Z-20191230113308.png"/></alternatives></inline-formula> loop and <inline-formula><tex-math id="Z-20191230113327">\begin{document}$\left\langle 100 \right\rangle $\end{document}</tex-math><alternatives><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="3-20191379_Z-20191230113327.jpg"/><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="3-20191379_Z-20191230113327.png"/></alternatives></inline-formula> loop, in this work the interaction between a <inline-formula><tex-math id="Z-20191230113322">\begin{document}$\left\langle 100 \right\rangle $\end{document}</tex-math><alternatives><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="3-20191379_Z-20191230113322.jpg"/><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="3-20191379_Z-20191230113322.png"/></alternatives></inline-formula> loop and {100} surface is studied in detail through the molecular dynamics method. The simulation results indicate that the factors including Burgers vector of loop, loop-to-surface depth, interaction between pre-existing <inline-formula><tex-math id="Z-20191230113337">\begin{document}$\left\langle 100 \right\rangle $\end{document}</tex-math><alternatives><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="3-20191379_Z-20191230113337.jpg"/><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="3-20191379_Z-20191230113337.png"/></alternatives></inline-formula> loops, and temperature, all seriously affect the interaction between loop and surface. Especially, the present results show for the first time the evolution of Burgers vector of <inline-formula><tex-math id="Z-20191230113333">\begin{document}$\left\langle 100 \right\rangle $\end{document}</tex-math><alternatives><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="3-20191379_Z-20191230113333.jpg"/><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="3-20191379_Z-20191230113333.png"/></alternatives></inline-formula> loop from <inline-formula><tex-math id="Z-20191230113343">\begin{document}$\left\langle 100 \right\rangle $\end{document}</tex-math><alternatives><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="3-20191379_Z-20191230113343.jpg"/><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="3-20191379_Z-20191230113343.png"/></alternatives></inline-formula> to 1/2<inline-formula><tex-math id="Z-20191230113348">\begin{document}$\left\langle 111 \right\rangle $\end{document}</tex-math><alternatives><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="3-20191379_Z-20191230113348.jpg"/><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="3-20191379_Z-20191230113348.png"/></alternatives></inline-formula> and its one-dimensional diffusion to surface. According to these results, we also further explore the surface evolution after its interaction with loop. The appearance of atomic island results in the rugged surface morphology. All these results provide a new insight into the radiation damage to the surface of material.