Magnetite

About: Magnetite is a research topic. Over the lifetime, 10277 publications have been published within this topic receiving 278071 citations.

A Close-up of the Effect of Iron Oxide Type on the Interfacial Interaction between Epoxy and Carbon Steel: Combined Molecular Dynamics Simulations and Quantum Mechanics

Abstract: In the present study, the effect of different types of iron oxides, which naturally exist on steel substrate, on the interfacial interaction between an epoxy coating and a carbon steel substrate was studied at the molecular/atomic level by employing molecular dynamics (MD) simulations and quantum mechanics (QM) calculations. Three types of iron oxide, that is, ferrous oxide (FeO), ferric oxide (Fe2O3, hematite), and ferrous ferric oxide (Fe3O4, magnetite), were considered for modeling, and their binding energies were calculated and compared by altering the concentration of hydroxide groups on the surface. To probe the effect of curing agent on interfacial interactions, computations were performed for either uncured or aminoamide-cured epoxy resins. The effect of the acid–base properties of the iron oxide on the molecular bonding was theoretically investigated by imposing diverse iron hydroxide/oxide termination groups. Noticeably, MD and QM calculations confirmed rather well earlier experimental evaluatio...

Magnetic properties of jet-printer inks containing dispersed magnetite nanoparticles

Abstract: Two ferrofluid inks for jet-printing, containing magnetite NPs of slightly different average radius (sample A: 6 nm; sample B: 8 nm) were prepared by adding a dispersion of magnetite nanopowders in n-hexane to an insulating ink. Isothermal magnetization loops of inks were measured by means of a vibrating sample magnetometer in the temperature interval 5–300 K up to 70 kOe. The inks were then ejected at room temperature on standard paper by means of either a thermal ink jet head (TIJ; sample A) or a piezoelectric ink jet head (PIJ; sample B). Magnetic properties of prints on paper (FC/ZFC curves, isothermal magnetic loops and related hysteretic properties) were measured between 10 and 300 K using an alternating gradient force magnetometer up to 20 kOe. The inks display a different magnetic behavior with respect to both prints. In particular, the dispersed NPs are characterized by an effective radius (and ensuing magnetic interaction) larger than expected on the basis of the properties of the starting powders. Instead, the NP radii in both prints are closer to the starting values. The printed magnetic films show an almost perfect superparamagnetic (SP) response around room temperature; however, at temperatures lower than 100 K the SP scaling is not observed and both samples behave as interacting superparamagnetic (ISP) materials. The evolution from the SP to the ISP regime is marked by a steady increase in the hysteretic properties of both samples. Particular attention will be paid to the study of magnetic interactions occurring among NPs. The effect of the ejection process on the degree of aggregation of magnetite NPs will be here studied.

Thermal alteration of the magnetic mineralogy in ferruginous rocks

Abstract: The Northampton ironstone contains the paramagnetic minerals siderite and berthierine and a trace of the ferrimagnetic mineral magnetite. The magnetic fabric of this sedimentary rock, as defined by the anisotropy of magnetic susceptibility, is controlled by bedding compaction but is inverse (i.e., the maximum susceptibility axes are normal to the bedding plane). This inverse fabric is attributed to the dominating presence of siderite. The rocks were incrementally heated to 600°C, and the magnetic fabric was measured at room temperature and at near liquid nitrogen temperature after each heating step; cooling the samples in liquid nitrogen enhances the paramagnetic contribution to the magnetic fabric. After heating the samples above 250°C, the room temperature magnetic fabric became normal with the minimum susceptibility axes perpendicular to the bedding plane. The low-temperature magnetic fabric remains inverse until the samples are heated to about 500°C. After heating to higher temperatures a normal fabric was observed at both room temperature and low temperature. Rock magnetic evidence shows that magnetite is created during the heating. The start of mineralogical changes in the rock was detected by electron spin resonance spectroscopy, powder X ray diffraction, and acquisition of isothermal remanence. Berthierine starts to break down at approximately 250°C and is totally oxidized by 500°C. The creation of magnetite in the heating experiments corresponds with this mineralogical change. The change in the room temperature magnetic fabric is associated with the decomposition of berthierine, part of which alters to magnetite. The new magnetite phase has a normal magnetic fabric which overprints the inverse magnetic fabric of siderite.