Jia Xu, Zhang Leilei, Tian Yi, Wu Binbin, Tao Yu, He Duanwei, Yang Baocheng, Boi Filippo S, Lei Li
Institute of Atomic and Molecular Physics, Sichuan University Chengdu 610065 China
Institute of Nano-Structured Functional Materials, Huanghe Science and Technology College Zhengzhou 450063 China
RSC Adv. 2024 Mar 4;14(11):7490-7498. doi: 10.1039/d3ra08967c. eCollection 2024 Feb 29.
In this work, we report a novel high-pressure solid-state metathesis (HSM) reaction to produce spherical bulk (diameters 2-4 mm) Co-C alloys (CoC and CoC). At 2-5 GPa and 1300 °C, C atoms preferentially occupy the interstitial sites of the face-centered cubic (fcc) Co lattice, leading to the formation of metastable CoC. The CoC decomposes above 1400 °C at 2-5 GPa, C atoms infiltrate the interstitial sites of the fcc Co lattice, saturating the C content in Co, forming an fcc CoC solid solution while the C atoms in excess are found to precipitate in the form of graphite. The Vickers hardness of the Co-C alloys is approximately 6.1 GPa, representing a 19.6% increase compared to hexagonal close-packed (hcp) Co. First-principles calculations indicate that the presence of C atoms in the CoC structure leads to a relative decrease in the magnetic moments of the two distinct Co atom occupancies. The Co-C alloys exhibited a soft magnetic behavior with saturation magnetization up to 93.71 emu g and coercivity of 74.8 Oe; coercivity increased as the synthesis pressure rises.
在这项工作中，我们报道了一种新型的高压固态复分解（HSM）反应，用于制备球形块状（直径2 - 4毫米）的Co - C合金（CoC和CoC）。在2 - 5 GPa和1300 °C下，C原子优先占据面心立方（fcc）Co晶格的间隙位置，导致亚稳CoC的形成。CoC在2 - 5 GPa下于1400 °C以上分解，C原子渗入fcc Co晶格的间隙位置，使Co中的C含量饱和，形成fcc CoC固溶体，而过量的C原子则以石墨形式析出。Co - C合金的维氏硬度约为6.1 GPa，相较于六方密堆积（hcp）Co提高了19.6%。第一性原理计算表明，CoC结构中C原子的存在导致两种不同Co原子占据的磁矩相对减小。Co - C合金表现出软磁行为，饱和磁化强度高达93.71 emu g，矫顽力为74.8 Oe；矫顽力随合成压力的升高而增加。
