ساخت و بررسي خواص ساختاري و مغناطيسي نانو ذرات فريت نيكل ﴿NiFe2O4﴾

چكيده انگليسي :

The Fabrication and Study of Structural and Magnetic Properties of Ni Ferrite Nanoparticles NiFe 2 O 4 Hajar Hajihashemi h hajihashemy@ph iut ac irU 1TU 1T Date of Submission 2012 07 02 Department of physics Isfahan University of Technology Isfahan 84156 83111 Iran Degree M Sc Language FarsiSupervisor Dr Parviz Kameli kameliU @cc iut ac irAbstract Spinel ferrites are a group of materials in the nanometer scale which have a wide variety of applications inmedicine and economics Now of the problems in this area is fabricating pure homogenous nanoparticles withcontrollable size In this research in order to prepare a pure sample of Ni ferrite in low temperatures severalmethods including sol gel with changing parameters such as pH complexion agent and co precipitation methodswere used In all the synthesized samples the effect of temperature on the structure and magnetic properties of thesamples was studied using analysis such as x ray diffraction XRD Furier Transform Infrared FTIR microscopicimaging SEM and vibrating sample magnetometer VSM The x ray diffraction spectrum of the samples preparedvia the sol gel method and with different pH verified that increasing pH decreases the formation temperature of thephase of pure ferrite nickel in this method Also the results showed that increasing pH of the first solution to 7 isconcomitant with decreasing the nano particles size and in the alkaline solution pH 7 again the size of theincrease causes the formation of the second phase of FeR n the samples Finally utilizing the complexingparticles increases Also in samples synthesized by the co precipitation method it was observed that temperature ROR Riagent of EDTA in synthesizing the samples by the sol gel method we managed to fabricate pure samples of nickelferrite in low temperatures The complexing agent EDTA by surrounding the metallic ions not only decreases theprobability of oxidation of metallic ions but also decreases the interaction between ions and causes the formation offiner particles The effect of temperature on the samples was studied The results of XRD showed that increasingthe annealing temperature results in larger particles The SEM images also confirm the enlarging of particlesconcomitant with temperature increasing Also strain in these samples decreases along with annealing temperaturedecreasing which is a sign of structure conversion from inverse spinel to mixed spinel The inverse structures of thesamples is changed and with the redistribution in the arrangement of the cations in the tetrahedral and octahedralsites the mixed structure is formed The changes in the relative intensity of the Brag peaks confirms this idea Themagnetization of the samples demonstrate the increase in saturation magnetization with enlargement of theparticles Based on the core shell model every particle is formed of a core part with the magnetic order called core and a disordered shell layer named shell Along with the particles enlargement the contribution of the coreincreases relative to the shell and therefore the saturation magnetization of the samples increases too Albeit thestructure conversion of the inverse to the mixd spinel has affected the magnetization It was also observed that thecoercive field of the samples increased with increasing the size of the particles up to 33 nm and then with moreincreasing in the size the field decreased The maximum of the coercive field happens in the critical size of thesingle domain and this critical size for the samples prepared by the EDTA method happened in the range of 25 33nm Keywords Spinel ferrites Sol gel Precipitation pH Temperature effect EDTA Cation Distribution Core shellmodel Critical size

حاجي هاشمي، هاجر

ساخت و بررسي خواص ساختاري و مغناطيسي نانو ذرات فريت نيكل ﴿NiFe2O4﴾

فريت هاي اسپيني , سل-ژل , همرسوبي , PH , اثر دما , EDTA , باز توزيع كاتيون هاي مدل مغزه-پوسته , اندازه بحراني