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Transformation of Co3O4 nanoparticles to CoO monitored by in situ TEM and predicted ferromagnetism at the Co3O4/CoO interface from first principles
Journal of Materials Chemistry C ( IF 5.7 ) Pub Date : 2021-3-27 , DOI: 10.1039/d0tc05727d
Xiaodan Chen 1, 2, 3, 4, 5 , Heleen van Gog 6, 7, 8, 9, 10 , Marijn A. van Huis 1, 2, 3, 4, 5
Affiliation  

Nanoparticles of Co3O4 and CoO are of paramount importance because of their chemical properties propelling their applications in catalysis and battery materials, and because of their intriguing magnetic properties. Here we elucidate the transformation of Co3O4 nanoparticles to CoO into nanoscale detail by in situ heating in the transmission electron microscope (TEM), and we decipher the energetics and magnetic properties of the Co3O4/CoO interface from first principles calculations. The transformation was found to start at a temperature of 350 °C, and full conversion of all particles was achieved after heating to 400 °C for 10 minutes. The transformation progressed from the surface to the center of the nanoparticles under the formation of dislocations, while the two phases maintained a cube-on-cube orientation relationship. Various possibilities for magnetic ordering were considered in the density functional theory (DFT) calculations and a favorable Co3O4/CoO {100}/{100} interface energy of 0.38 J m−2 is predicted for the lowest-energy ordering. Remarkably, the DFT calculations revealed a substantial net ferromagnetic moment originating from the interface between the two antiferromagnetic compounds, amounting to approximately 13.9 μB nm−2. The transformation was reproduced ex situ when heating at a temperature of 400 °C in a high vacuum chamber.

中文翻译:

通过原位TEM监测Co3O4纳米颗粒向CoO的转化,并根据第一原理预测Co3O4 / CoO界面处的铁磁性

Co 3 O 4和CoO纳米颗粒具有极其重要的意义,因为它们的化学性质推动了它们在催化和电池材料中的应用,并且由于它们令人着迷的磁性。在这里,我们阐明了在透射电子显微镜(TEM)中通过原位加热将Co 3 O 4纳米颗粒从CoO转变为纳米级细节的过程,并解释了Co 3 O 4的能量和磁性能。/ CoO接口来自第一个原理的计算。发现该转化在350℃的温度开始,并且在加热至400℃10分钟之后实现了所有颗粒的完全转化。在位错的形成下,相变从纳米颗粒的表面发展到中心,而两相则保持了立方对立方的取向关系。在密度泛函理论(DFT)计算中考虑了各种有序的磁性排序方法,以及0.38 J m -2的有利Co 3 O 4 / CoO {100} / {100}界面能预测最低能量排序。值得注意的是,DFT计算显示从所述两个反铁磁化合物之间的界面产生实质性的净力矩铁磁始发,约计13.9 μ纳米-2。该变换被再现易地在高真空室中在400℃的温度下加热时。
更新日期:2021-04-14
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