Nanocrystalline maghemite O was prepared by a wet chemical method. The thermal stability of this material has been investigated by using differential thermal analysis (DTA) measurements and x-ray diffraction analyses. One exothermic peak without weight loss appears irreversibly on the DTA curve. It was confirmed for the first time that this exothermic peak corresponds completely to the maghemite-to-hematite (-to-) structural phase transition. The nanocrystalline maghemite O particles grow very slowly when the temperature is lower than the range of the exothermic peak; whereas, during and after the transition, the nanocrystalline hematite O particles grow rapidly with increasing temperature. Moreover, the transition temperature of nanocrystalline maghemite O is higher than that of the coarse-grained counterpart. In this paper, the authors have also suggested some preliminary physical interpretations of the experimental results.

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Ke-Ying(张科营) a) † , Guo Hong-Xia(郭红霞) a) , Luo Yin-Hong(罗尹虹) a) , Fan Ru-Yu(范如玉) a) , Chen Wei(陈 伟) a) , Lin Dong-Sheng(林东生) a) , Guo Gang(郭 刚) b) , and Yan Yi-Hua(闫逸华) c)

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Radiation effects of microprocessor in mixed neutron and gamma rays radiation field were researched. The ionizing energy deposited by neutron in Geant4 simulation accords with experimental data. Qualitative correlation is demonstrated between transistors and circuit.Index Terms-gamma irradiation, microprocessor, neutron irradiation, total ionizing dose effect