Naslov
INFLUENCE OF Ni-DOPAND ON THE PROPERTIES OF SYNTHETIC GOETHITE

Autori
Krehula, Stjepko ; Musić, Svetozar ; Popović, Stanko

Vrsta, podvrsta i kategorija rada
Sažeci sa skupova, sažetak, znanstveni

Izvornik
International Conference on the Applications of the Mössbauer Effect / - Montpellier, 2005, T7-P20

Skup
International Conference on the Applications of the Mössbauer Effect

Mjesto i datum
Montpellier, Francuska, 05.09.2005. - 09.09.2005

Vrsta sudjelovanja
Poster

Vrsta recenzije
Nije recenziran

Ključne riječi
Ni-doping; alpha-FeOOH; XRD; FT-IR; 57Fe Mössbauer; TEM

Sažetak
Synthetic alpha-FeOOH was synthesized at highly alkaline pH by precipitation from a FeCl3 solution with the addition of tetramethylammonium hydroxide and further autoclaving of the precipitation system at 160 &ordm ; C. Ni-doped alpha-FeOOH samples were precipitated in the same way, but in the presence of varying concentrations of NiCl2. The ratio of Ni/Fe in the samples was checked by a PIXE analysis. XRD showed the presence of an alpha-FeOOH structure as a single phase up to the ratio Ni/Fe = 0.05, with a gradual broadening of diffraction lines upon increase in the amount of Ni-dopand. NiFe2O4 was found besides the dominant alpha-FeOOH phase at the ratio Ni/Fe = 0.10. FT-IR spectra showed very similar features up to the ratio Ni/Fe = 0.05. For a higher amount of Ni2+ ions, corresponding to the ratio Ni/Fe = 0.10, the IR band centered at 631 cm-1 with a shoulder at 665 cm-1 was significantly broadened and increased in relative intensity. Also, the IR band centered at 404 cm-1 was strongly broadened, whereas the relative intensities of shoulders at 451 and 371 cm-1 were significantly increased in relation to IR-bands at 454 and 376 cm-1, recorded for an undoped alpha-FeOOH. Shifts in IR bands at 892 and 796 cm-1 corresponding to Fe-OH bending vibrations were not observed for any concentration of Ni dopand. 57Fe Mössbauer spectroscopy showed high sensitivity to doping of alpha-FeOOH with Ni2+ ions. The Mössbauer spectrum of undoped alpha-FeOOH showed a sextet which deviates from the theoretical intensities ratio, with broadened spectral lines. The distributions of hyperfine magnetic fields were calculated. decreased from 35.1 T for an undoped alpha-FeOOH to 32.1 T for a sample with the ratio Ni/Fe = 0.05. Mössbauer spectroscopy showed that for the concentrations of Ni2+ ions higher than ~ 5 mol % there is saturation of the alpha-FeOOH structure with Ni2+ ions. TEM photographs of samples up to the Ni/Fe ratio 0.10 showed the presence of acicular alpha-FeOOH particles. The particle size (length) of reference goethite showed a maximum in the range 180-220 nm. The particle size was slightly decreased with Ni-doping ; however, the distribution of the length/width ratio did not change, and the maximum probability of this factor was at 4 to 5. For the Ni/Fe ratio 0.05 TEM photographs also showed a small population of cubic or pseudocubic particles ~ 10 nm in size, which were assigned to NiFe2O4. NiFe2O4 particles formed for the Ni/Fe ratio = 0.10 were about 10 to 20 nm in size.

Izvorni jezik
Engleski

Znanstvena područja
Fizika, Kemija

POVEZANOST RADA