This paper presents the magnetite study results of a Fe3O4/C nanocomposite obtained with air pyrolysis of a heterogeneous system which includes iron dichloride tetrahydrate – the source of magnetite nanoparticles (NPs) – and polyacrylonitrile (PAN) – the source of a carbon shell for nanoparticles protection from issues like aggregation. Methods such as Mössbauer spectroscopy and X-ray diffraction analysis are used for studying and determine the magnetite NP formation way. There are two types of NPs in the system studied: ferrimagnetic and superparamagnetic ones, the difference between which is clearly watched when taking Mössbauer spectra – sextets and doublets relatively. All magnetite NPs are established to be formed according to the reaction chain the inter-mediate elements of which is ferrous carbonate well-known for its decomposition into magnetite upon heating: FeCl2 → FeCO3 → Fe3O4. This transformation occurs in the temperature range from 200 oC to 400 oC above which an ability of the carbon shell to protect NPs is gradually reduced that leads to agglomeration and oxidation to hematite α-Fe2O3.
To study the magnetite obtained, size distribution of magnetite crystallites and the degree of nonstoichiometry are estimated. According to various calculations, the average crystallite size is 9-10 nm.
To preserve the NP properties, storage methods are important to be chosen properly, thence Mössbauer spec-troscopy of the Fe3O4/C nanocomposite is carried out after keeping it in air at room temperature for 1 year.