Preparation and characterization of Nickel-and cobalt-doped magnetites

Abstract

Nickel-and cobalt-doped magnetites were prepared by a co-precipitation method and studied in some detail, in an effort to identify some effects of the doping cations on the magnetic, crystallographic and morphological properties of the resulting spinel. The synthetic samples were characterized by conventional chemical analysis, powder X-ray diffractometry, Mössbauer spectroscopy, saturation magnetization and scanning electron microscopy. From chemical analysis, the continuous increase of Ni 2+ or Co 2+ is accompanied by a simultaneous decrease of the Fe 2+ contents, in the spinel structure. The magnetization values also decrease continuously with increasing doping cation contents. Mössbauer parameters are characteristic of substituted magnetites and indicate the presence of a single phase only. Based on the inverted intensities of the lines 1 (leftmost, on the negative Doppler velocity scale) and 2 of Mössbauer spectra of doped samples, relatively to the pure magnetite, it was assumed that the isomorphical substitution occurs preferentially on octahedral coordination sites of the spinel structure. The coercive field of these ferrites decrease steadily with Ni 2+ but increases with Co 2+ contents, reaching a maximum at x = 0.38, in the general formula Co x Fe 3-x O 4 .

Effect of Mechanochemical Treatment on Magnetic Properties of Nanodimensional Magnetite-Type Materials

“…nanoparticles [1,3,12,13]. We cannot exclude again the inuence of the agglomeration eects typical for wet synthesis methods as co-precipitation [11].…”

Synthesis of Improved Catalytic Materials for High-Temperature Water-gas Shift Reaction

“…[6][7][8][9] Magnetite (Fe3O4) and substituted magnetite-type ferrites -Me0.5Fe2.5O4 (Me = Mn 2+ , Co 2+ , Cu 2+ , etc.) are members of solid solution series, which permits the synthesis of samples with various magnetic properties and various degree of electron T delocalization.…”

“…It was found that the properties of nanosized spinel ferrites differ strongly from those of the corresponding bulk materials. [6][7][8][9] It was found that partially substituted magnetites (MexFe3-xO4) have better catalytic behavior than the MeFe2O4. [2][3] Up today, much attention has been paid to the preparation of such nanocrystalline bulk and supported materials, because of difficulty of their synthesis procedures and special techniques used.…”

“…Various synthetic methods have been developed to synthesize oxide nanoparticles, among them co-precipitation, thermal decomposition, sol-gel, microemulsion and other techniques. [2][3][6][7][8][9] It was established that the degree of crystallinity, particle size and particle morphology of oxide nanoparticles are strongly dependent on the method used for their preparation. In this regard the heterogeneous catalyst for water-gas shift reaction should have a number of characteristics.…”

Mass spectrometric analysis of mono- and multi-phosphopeptides by selective binding with NiZnFe2O4 magnetic nanoparticles

“…Magnetic nanoparticles of ferrites (mNOF) and transition metal ion doped ferrites (for example, Ni 2 þ and Zn 2 þ ) [15][16][17] have been studied because of their distinct magnetic and electrical properties [18][19][20] , chemical and thermal stabilities 21,22 , coordination abilities of exposed octahedral metal ions 22 as well as high ratios of surface area to volume. We demonstrate here that different metal ions at the surface octahedral sites of NiZnFe 2 O 4 , Fe 3 O 4 , NiFe 2 O 4 and ZnFe 2 O 4 nanoparticles have distinctly different binding affinities towards multi-and monophosphopeptides.…”