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In geology, a redox buffer is an assemblage of minerals or compounds that constrains oxygen fugacity as a function of temperature. Knowledge of the redox conditions (or equivalently, oxygen fugacities) at which a rock forms and evolves can be important for interpreting the rock history.
This buffer is known as the hematite-magnetite or HM buffer. At lower oxygen levels, magnetite can form a buffer with quartz and fayalite known as the QFM buffer. At still lower oxygen levels, magnetite forms a buffer with wüstite known as the MW buffer. The QFM and MW buffers have been used extensively in laboratory experiments on rock ...
The formula for magnetite is more accurately written as FeO·Fe 2 O 3 than as Fe 3 O 4. Magnetite is one part FeO and one part Fe 2 O 3, rather than a solid solution of wüstite and hematite. Magnetite is termed a redox buffer because, until all Fe 3+ present in the system is converted to Fe 2+, the oxide mineral assemblage of iron remains
Oxygen fugacity range where common cation pairs dominate.Data for plotting are from Shearer et al., (2006). [1] IW represents Iron-Wüstite buffer and QFM represents Quartz-Fayalite-Magnetite buffer. Mantle oxidation state (redox state) applies the concept of oxidation state in chemistry to the study of the Earth's mantle.
Buffer capacity falls to 33% of the maximum value at pH = pK a ± 1, to 10% at pH = pK a ± 1.5 and to 1% at pH = pK a ± 2. For this reason the most useful range is approximately p K a ± 1. When choosing a buffer for use at a specific pH, it should have a p K a value as close as possible to that pH.
Iron(II,III) oxide, or black iron oxide, is the chemical compound with formula Fe3O4. It occurs in nature as the mineral magnetite. It is one of a number of iron oxides, the others being iron(II) oxide(FeO), which is rare, and iron(III) oxide(Fe2O3) which also occurs naturally as the mineral hematite. It contains both Fe2+and Fe3+ions and is ...
H {\displaystyle H} is the magnitude of the applied magnetic field (A/m), T {\displaystyle T} is absolute temperature (K), C {\displaystyle C} is a material-specific Curie constant (K). Pierre Curie discovered this relation, now known as Curie's law, by fitting data from experiment. It only holds for high temperatures and weak magnetic fields.
Iron oxide nanoparticles are used in cancer magnetic nanotherapy that is based on the magneto-spin effects in free-radical reactions and semiconductor material ability to generate oxygen radicals, furthermore, control oxidative stress in biological media under inhomogeneous electromagnetic radiation.