The effect of iridium(III) ions on the formation of iron oxides in a highly alkaline medium

Synthesis and Properties of Ni-doped Goethite and Ni-doped Hematite Nanorods

“…(a) Bhf is an average value of the hyperfine magnetic field distribution crystallinity [71,72] and M-for-Fe substitution. [62][63][64]73,74] In the present case, Ni-for-Fe substitution caused a shift to lower wave numbers, while an increase in Ni-goethite particle size caused a shift to higher wave numbers. Fe-O stretching or the lattice vibration band at 622 cm -1 gradually shifted to lower wave numbers due to both Ni-for-Fe substitution and increased particle size and crystallinity.…”

“…An increase in size of metal-doped goethite crystallites and particles, formed by the same mechanism, was also observed in the case of Mn, Ir or In doping of goethite. [61][62][63][64] The XRPD patterns of the calcined samples Ni0-400 to Ni50-400 are shown in Figure 4 along with the positions and intensities of diffraction lines of the standard hematite The widths of the strongest hematite diffraction lines (104) and (110) (as well as the widths of other, less intense lines) differ significantly, which is typical for hematite prepared by calcination of goethite nanorods at temperatures < 500 °C. [65] This phenomenon was explained by the presence of two different iron stacking sequences (twin orientations) in the same hexagonal close-packed oxygen framework of hematite obtained by calcination of goethite.…”

“…In line with XRPD results, which revealed an increase in goethite crystallite size by Ni doping, increasing size of the goethite nanorods by Ni doping (SEM images of samples Ni20, Ni33 and Ni50) was also evident, similar to the doping of goethite with Mn, Ir or In. [61][62][63][64] In the images of samples with high Ni content, both Ni ferrite nanoparticles and elongated goethite particles are present. FE-SEM images of calcined samples ( Figure 6) showed the presence of Ni-doped hematite nanorods and nanoparticles of minor phases with unchanged size and shape compared to the initial samples prior to calcination.…”

“…A shift of this band to lower wave numbers has been observed in the spectra of goethite samples with larger crystallites and thicker particles [71,72] and in goethites doped with metal cations heavier than iron cations (Cu 2+ , Zn 2+ , Cd 2+ , Ir 3+ ). [62,63,73,74] FT-IR spectra of undoped hematite and Ni-doped hematite samples are shown in Figure 10. All bands in the spectrum of sample Ni0 could be assigned to hematite according to Serna et al [75] A shoulder at 640 cm -1 and a weak band at 394 cm -1 correspond to the A2u vibration modes with a transition moment parallel to the c axis, whereas the strongest bands at 517 and 432 cm -1 correspond to the Eu vibration modes with a transition moment perpendicular to the c axis.…”

Degradation of Acid Red 8 Dye Using Photo-Fenton Reaction Mediated by Titanium Modified Catalysts

“…Changes in the structure, unit-cell dimensions, crystallite size and morphology have been ascribed to incorporation of ions into iron oxide, as in the case of Ti IV in the present work. [32][33][34] The crystallite size has a strong influence on the surface area and consequently plays an important role on surface reactions. 35 Table 1 shows that the increase of titanium content favors the formation of larger crystallites, in agreement with values reported for α-hematite and titanomaghemite.…”