Micromagnetic Modeling of Magnetite/Maghemite Particles with a Multi-Layer Core-Shelled Structure

2020 ◽  
Vol 1013 ◽  
pp. 9-13
Author(s):  
Kun Peng Ge ◽  
Wyn Williams

Low temperature oxidized core-shelled magnetite is paramount important in recording geomagnetic field. To characterize the effects of transition zone between the core-shell on the magnetic properties of low temperature oxidation of magnetite, micromagnetic models of hysteresis parameters and microstructures of a multi-layer core-shelled model were systematically investigated by MERRILL (Micromagnetic Earth Related Rapid Interpreted Language Laboratory). Numerical simulations indicate that SD particles (<70 nm) remain highly uniform magnetization, but show decreasing coercivities as oxidation preceeds. For fine SV particles (80 nm to 120 nm), the hysteresis parameters respectively increase and dramatic decrease at the early and late stage of oxidation, and the micromagnetic behaviors vary significantly. Finally the hysteresis parameters of larger SV (>130) particles remain nearly unchanged during oxidation. It indicates that fine SV particles are more sensitive to oxidation, and dominate the dramatic change of experiment observation. Overall, low temperature oxidation of magnetite preferring a multi-layer coupled oxidation process from outside to interior and is capable of recording paleomagnetic signals.

Fuel ◽  
2018 ◽  
Vol 222 ◽  
pp. 350-361 ◽  
Author(s):  
Lanjun Zhang ◽  
Zenghua Li ◽  
Wenjing He ◽  
Jinhu Li ◽  
Xuyao Qi ◽  
...  

2013 ◽  
Vol 652-654 ◽  
pp. 871-876 ◽  
Author(s):  
Xiao Xing Zhong ◽  
Guo Lan Dou ◽  
Hai Hui Xin ◽  
De Ming Wang

Low temperature oxidation of two different low rank coals was measured by in-situ FTIR. Curve-fitting analysis was employed to identify functional groups types of raw coals, and series technology was carried out on in-situ infrared spectrum of sample coals at low-temperature oxidation process to analyze the changes of main active functional groups with temperature. The results indicate that -CH3, -CH2, -OH, C=O, COOH are the main active functional groups in low rank coal. In the oxidation process, with temperature increasing, the methyl and methylene show the tendency of increase after decrease and then decrease, and all of hydroxyl, carboxyl and carbonyl group present the tendency of increase after decrease, there exists some differences among the main functional groups in the coal low-temperature process.


2004 ◽  
Vol 234 (1-4) ◽  
pp. 197-201 ◽  
Author(s):  
T Hattori ◽  
K Azuma ◽  
Y Nakata ◽  
M Shioji ◽  
T Shiraishi ◽  
...  

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