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Abstract
Nanocrystalline materials are showing great prospects in industry and technology. This is mainly because they have some unique properties which are not shown by the bulk crystalline materials. Nanomaterials represent almost the ultimate in increasing surface area. Substances with high surface area have enhanced chemical, mechanical, optical and magnetic properties, and this can be exploited for a variety of structural and non-structural applications.
Surface coating of nanoparticles with different materials to produce core-shell structures is currently an active area of research, because such coating allows modification and tailoring of physical and chemical properties of core materials depending on synthetic conditions. Furthermore, core-shell nanoparticles are expected to have unique properties that are not originally present in either core or shell materials. The pure PANI, MgFe2O4, Co0.5Mg0.5Fe2O4, CoFe2O4, PANI/ MgFe2O4, PANI/ Co0.5Mg0.5Fe2O4 and PANI/ CoFe2O4 have been synthesized in this research work as the following:
Preparation of Co1-xMgxFe2O4
Co1-xMgxFe2O4 (x= 0, 0.5, 1) nano-particles were prepared by mixing a solutions of Co(NO3)2.6H2O, Mg(NO3)2.6H2O and Fe(NO3)3.9H2O in stoicchiometric ratio with a solution containing NaOH+Na2CO3 [80,81] ([NaOH]=1.6[Mg+2+Co+2+Fe+3], [CO32-]=2.0[Fe3+]) in deionised water (pH≈9). The solutions were simultaneously added to a colloid mill [82, 83] and mixed for 2 min. The resulting slurry was placed in a three neck flask and aged at 100 °C for 6 h. The final precipitate was filtered, washed thoroughly with deionised water and dried at 100 °C for 24 h. The resulting sample was then calcined at 900 °C for 2 hrs. and then grinded to obtain a fine powder.
Synthesis of PANI / Co1-xMgxFe2O4
A typical in-situ chemical polymerization method for the PANI/ Co1-xMgxFe2O4 was carried out by the routine synthesis [65]. 0.5 g of Co1-xMgxFe2O4 was added to 50 ml of freshly prepared reaction mixture (0.2M aniline and 0.25 M ammonium peroxydisulphate in 1 M HCl) at 20 °C. The mixture was stirred during the polymerization of aniline for 12 hrs. The ferrite coated with PANI was separated on a filter paper, rinsed with 1 M HCl and warm de-ionized water, and dried at 70 °C in an electrical oven.
Throughout this work it was found that:
• The pure PANI and the core-shell materials of PANI/ Co1-xMgxFe2O4 have been synthesized successfully in this research work by in situ chemical oxidative polymerization method.
• The structure of the obtained polymer nanocomposites was investigated. The obtained data from the XRD, FTIR and UV-vis. showed that there is an interaction between the ferrites and PANI. Also, the morphology of the composites was characterized by TEM showing that obtained composites have core-shell structures.
• The thermal behavior of the composites was represented by using the TGA technique. We found that the presence of the ferrites in the PANI matrix increase the thermal stability of the polymer and by increasing the ferrite content in the composite, the thermal stability increase.
• The magnetic properties of the composites were investigated by VSM. The magnetic parameters indicate that the adding of the ferrites to the PANI improves its magnetic nature. The variation in the structure of the ferrite as the following: Co1-xMgxFe2O4 (x= 0, 0.5, 1), enable us to produce composite materials with tailoring properties.
• By studding the electrical conductivities of the pure PANI and composites, we found that the conductivity of the composites decrease by adding the ferrites.
• The adsorption of bromopyrogallol red dye as toxic dye on PANI was investigated and we found that the adsorption rate is affected by presence of the ferrites and the PANI/CoFe2O4 was the best one for the adsorption.