Thermodynamics of Iron Oxides and Oxyhydroxides in Different Environments

Holocene palaeoenvironmental conditions in NE Bulgaria uncovered by mineral magnetic and paleomagnetic records of an alluvial soil

“…c) the same as b) for samples from the alluvial clays in the C horizon. and Barnard, 2016;Roberts et al, 2020). Its presence is further revealed by the variations with depth of the S-ratio (Fig.…”

“…The absence of the peak at 500 • C on the cooling curve for the sample at 171 cm depth probably indicates deficiency of organic matter, although the strong increase of the signal on cooling as relative percent from the initial susceptibility is similar to that of other samples. Consequently, another source favoring reducing conditions, such as water from the dehydration of hydrous minerals, during heating at high temperatures (above 600 • C) induces similar reactions (Guo and Barnard, 2016). The latter contribute to k-increase on cooling for the soil samples as well.…”

Chemistry for Audio Heritage Preservation: A Review of Analytical Techniques for Audio Magnetic Tapes

“…It is worth noting that, in general, during these transformations, due to the different crystal structure, the density of the starting material changes (in the case magnetite → maghemite, density falls) with an increasing of weight if oxidation processes occur due to oxygen taking up. It was reported [34,35,37] that, in magnetite particles larger than 300 nm, some hematite nuclei formed even at temperature lower than 200 • C and maghemite formation was bypassed; at 200-250 • C, crystal smaller than 300 nm transformed to maghemite which in turn transformed to hematite (Figure 11). It was observed that small amount of OH favor maghemite formation.…”

“…The most important iron magnetic oxides [34][35][36][37] are magnetite (Fe 3 O 4 ) and maghemite (γ-Fe 2 O 3 ), as shown in Figure 9. Magnetite is a black ferrimagnetic oxide containing both Fe II and Fe III ions forming two interpenetrating magnetic sublattices: Fe III occupies tetrahedral sites and octahedral sites are occupied by both Fe II and Fe III .…”

On the thermal and hydrothermal stability of spinel iron oxide nanoparticles as single and core-shell hard-soft phases

“…[13][14][15][16][17] Moreover, the transition in nanosized systems is size-dependent. [3,[18][19][20][21][22][23][24][25][26] In the literature, there are several ways to stabilize the spinel iron oxides from phase transition.…”