Laser-Induced Hematite/Magnetite Phase Transformation

Dynamic shock wave driven simultaneous crystallographic and molecular switching between α-Fe2O3 and Fe3O4 nanoparticles – a new finding

“…, from the hematite to the magnetite (Fe 3 O 4 ) and the XRD pattern obtained is matched well with the standard XRD pattern of the magnetite. 47 In the present case, the required minimum energy for the phase transition from α-Fe 2 O 3 to Fe 3 O 4 might have been supplied by the applied shock pulses inducing the breakage of the Fe–O bonds in the atomic structure, which could have resulted into the local volume collapse of the hematite enforcing dynamic re-crystallization. 27…”

“…47 Because α-Fe 2 O 3 is an oxygen-rich system compared to Fe 3 O 4 , there are many possibilities for initiating the oxidation process under high-temperature and high-pressure conditions resulting in the observed oxygen poor system in the Fe and O system rather than the polymorphic phases. 36,47 It was suspected from the observed results that the contribution of the effects related to the kinetics of the crystallization interface of the Fe and O systems were quite a lot higher than that of the impact of the oxygen content. While increasing the number of shocks to as high as 400 shocks, the hematite NPs were observed and the corresponding XRD pattern is shown in Fig.…”

“…36,44–46 Ferreira et al have observed the phase-transition from hematite to magnetite (Fe 3 O 4 ) influenced by high power laser irradiation (100 W). 47 Mendili et al demonstrated the transition from γ-Fe 2 O 3 to α-Fe 2 O 3 influenced by thermal treatment and laser irradiation. 48 Rozenberg et al have shown that hematite has high-pressure phase stability up to 76 GPa and found the structural phase-transition from the corundum-type structure to the Rh 2 O 3 ( ii ).…”

Full Spectral Range Raman Signatures Related to Changes in Enameling Technologies from the 18th to the 20th Century: Guidelines, Effectiveness and Limitations of the Raman Analysis

“…The red is made of hematite [2,51] and the brown was obtained by mixing these two colorations. Note the very high sensitivity of the spectrum to the illumination power which causes oxidation and phase changes from a few to 0.1 mW [51,70,71]. The blue dots show a glaze spectrum, with a weak quartz signal, characteristic of coloring by cobalt ions dissolved in the glaze.…”

“…This is the case of tridymite (SiO 2 ) which is very difficult to detect, more difficult than mullite, even when significant quantities are observed by diffraction [69]. The second difficulty concerns the strongly colored phases formed of elements with multiple variances which are heated up under the laser beam and transform, resulting in oxidation and phase transition [51,66,70,71]. The measurement must be done under very low laser power, which is expensive in terms of measurement time.…”