Synthesis and Characterization of Nanocrystalline Magnetic Pigment via Coordinated Precursors

Nanocrystalline cobalt ferrite as a magnetic black pigment was synthesizedvia coordinated precursors with a significant decrease of the synthesistemperature using citric acid as a coordinating agent. the structure andproperties of the cobalt ferrite powder were characterized by x-ray diffraction (xrd),colorimetric analysis (l*a*b* color parameters), diffuse reflectance spectroscopy andvibrating sample magnetometer (vsm). in addition, the structural coordination andmorphology of the precursors and cobalt ferrite powder were evaluated by infraredspectroscopy (ftir) and scanning electron microscopy (sem). simultaneous thermalanalysis (tg-dtg-dta) was used to investigate the thermal decomposition of thecoordinated precursor. ftir spectra of the precursors indicated that carboxylategroups of citric acid coordinated to the metal ions to form the coordinated precursors.diffraction patterns and ftir spectrum confirmed the formation of a pure organic freesingle-phase spinel with a cubic system (fd3m). the crystallite size was in the range of18-22 nm using scherrer equation. the sem micrographs showed changes in themorphology of the precursors and in the sample in which the cobalt ferrite powder hadalmost spherical morphology. colorimetric analysis using l*a*b* coordinates anddiffuse reflectance spectroscopy revealed nearly full light absorption in the 350-750 nmrange which are in agreement with the black color of the cobalt ferrite pigment. valuesof the saturation magnetization (ms), remanent magnetization (mr) and magneticcoercivity (hc) corresponding to the cobalt ferrite powder were: 67.72 emu/g, 32.54emu/g and 1.8 koe, respectively. they were lower than the bulk values because of thenanoscale of the powder. prog. color colorants coat. 2(2009), 35-43. © institute forcolor science and technology.