چكيده لاتين :
Nanocrystalline cobalt ferrite as a magnetic black pigment was synthesized
via coordinated precursors with a significant decrease of the synthesis
temperature using citric acid as a coordinating agent. The structure and
properties of the cobalt ferrite powder were characterized by X-ray diffraction (XRD),
colorimetric analysis (L*a*b* color parameters), diffuse reflectance spectroscopy and
vibrating sample magnetometer (VSM). In addition, the structural coordination and
morphology of the precursors and cobalt ferrite powder were evaluated by infrared
spectroscopy (FTIR) and scanning electron microscopy (SEM). Simultaneous thermal
analysis (TG-DTG-DTA) was used to investigate the thermal decomposition of the
coordinated precursor. FTIR spectra of the precursors indicated that carboxylate
groups 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 free
single-phase spinel with a cubic system (Fd3m). The crystallite size was in the range of
18-22 nm using Scherrer equation. The SEM micrographs showed changes in the
morphology of the precursors and in the sample in which the cobalt ferrite powder had
almost spherical morphology. Colorimetric analysis using L*a*b* coordinates and
diffuse reflectance spectroscopy revealed nearly full light absorption in the 350-750 nm
range which are in agreement with the black color of the cobalt ferrite pigment. Values
of the saturation magnetization (Ms), remanent magnetization (Mr) and magnetic
coercivity (Hc) corresponding to the cobalt ferrite powder were: 67.72 emu/g, 32.54
emu/g and 1.8 kOe, respectively. They were lower than the bulk values because of the
nanoscale of the powder. Prog. Color Colorants Coat. 2(2009), 35-43. © Institute for
Color Science and Technology.
