Emergence of interstitial-atom-free HCP nickel phase during the thermal decomposition of Ni3C nanoparticles
Emergence of interstitial-atom-free HCP nickel phase during the thermal decomposition of Ni3C nanoparticles
复制标题
DOI：
10.1039/c4ra01874e
复制
发表时间：
2014-01-01
期刊：
影响因子：
3.9
通讯作者：
Shieu, Fuh-Sheng
中科院分区：
文献类型：
--
作者：
Chiang, Ray-Tung;Chiang, Ray-Kuang;Shieu, Fuh-Sheng
在惰性氮气气氛下，在300℃至800℃的温度范围内对Ni₃C纳米粒子（NPs）的热分解进行了实验研究。结果表明，在500℃的分解温度下，形成了六方密堆积（HCP）镍相，其晶胞常数a = 0.2496 nm，c = 0.4078 nm。这些常数与无间隙原子（IAF）六方密堆积镍的理论预测值相似。因此，可以推断在Ni₃C热分解为面心立方（FCC）镍和碳的过程中，六方密堆积镍相是作为中间相形成的。透射电子显微镜（TEM）结果表明，这种无间隙原子六方密堆积镍相的形成是由于在镍纳米粒子上附着了类石墨壳层，它限制了密堆积层的滑移，从而阻碍了六方密堆积镍向面心立方镍的转变过程。磁化结果显示，饱和磁化强度（M - s）随着六方密堆积镍含量的增加而增加。此外，外推结果表明，在300 K的温度下，无间隙原子六方密堆积镍相的M - s值等于70.1 emu g⁻¹。换句话说，无间隙原子六方密堆积镍相是铁磁性的，其磁矩略高于面心立方镍。总体而言，本研究中呈现的结果为六方密堆积镍相的磁化特性提供了有用的见解，并且与理论预测相符。
An experimental investigation is performed into the thermal decomposition of Ni3C nanoparticles (NPs) under an inert nitrogen atmosphere at temperatures ranging from 300 to 800 degrees C. It is shown that given a decomposition temperature of 500 degrees C, a hexagonal close-packed (HCP) Ni phase is formed with cell constants of a=0.2496 nm and c=0.4078 nm. These constants are similar to those predicted theoretically for interstitial-atom-free (IAF) HCP Ni. Thus, it is inferred that the HCP Ni phase is formed as an intermediate phase during the thermal decomposition of Ni3C into face-centered cubic (FCC) Ni and carbon. The transmission electron microscopy (TEM) results suggest that the formation of this IAF HCP Ni phase is due to the adhesion of a graphite-like shell on the Ni NPs, which constrains the slip of the close-packed layers and therefore hinders the HCP Ni to FCC Ni transformation process. The magnetization results show that the saturation magnetization (M-s) increases with increasing HCP Ni content. In addition, the extrapolation results suggest that the Ms value of the IAF HCP Ni phase is equal to 70.1 emu g(-1) at a temperature of 300 K. In other words, the IAF HCP Ni phase is ferromagnetic with a magnetic moment slightly higher than that of FCC Ni. Overall, the results presented in this study provide a useful insight into the magnetization properties of the HCP Ni phase and are consistent with the theoretical predictions.