Trevor P Almeida

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Magnetite (Fe3O4) is an important magnetic mineral to Earth scientists, as it carries the dominant magnetic signature in rocks, and the understanding of its magnetic recording fidelity provides a critical tool in the field of palaeomagnetism. However, reliable interpretation of the recording fidelity of Fe3O4 particles is greatly diminished over time by(More)
The thermomagnetic behavior of remanence-induced magnetite (Fe3O4) particles in the pseudo-single-domain (PSD) size range (~0.1–10μm), which dominate the magnetic signature of many rock lithologies, is investigated using off-axis electron holography. Construction of magnetic induction maps allowed for the visualization of the vortex domain state in an(More)
The study of the paleomagnetic signal recorded by rocks allows scientists to understand Earth's past magnetic field and the formation of the geodynamo. The magnetic recording fidelity of this signal is dependent on the magnetic domain state it adopts. The most prevalent example found in nature is the pseudo-single-domain (PSD) structure, yet its recording(More)
The effect of maghemization on the magnetic properties of magnetite (Fe3O4) grains in the pseudo-single-domain (PSD) size range is investigated as a function of annealing temperature. X-ray diffraction and transmission electron microscopy confirm the precursor grains as Fe3O4 ranging from 150 to 250 nm in diameter, whilst M€ ossbauer spectrometry suggests(More)
The hydrothermal growth mechanism of α-Fe₂O₃ nanorods has been investigated using a novel valve assisted pressure autoclave. This approach has facilitated the rapid quenching of hydrothermal suspensions into liquid nitrogen, providing 'snapshots' representative of the near in situ physical state of the synthesis reaction products as a function of known(More)
A unique new class of core-shell structured composite nanoparticles, C-coated inorganic fullerene-like WS2 (IF-WS2) hollow nanoparticles, has been created for the first time in large quantities, by a continuous chemical vapour deposition method using a rotary furnace. Transmission electron microscopy and Raman characterisations of the resulting samples(More)
A suite of near-identical magnetite nanodot samples produced by electron-beam lithography have been used to test the thermomagnetic recording fidelity of particles in the 74–333 nm size range; the grain size range most commonly found in rocks. In addition to controlled grain size, the samples had identical particle spacings, meaning that intergrain(More)
The production of a synthetic basalt comprising Fe3O4 grains (~ 50 nm to ~ 500 nm), via a glass ceramic method, has been confirmed using transmission electron microscopy and X-ray diffractometry. Off-axis electron holography combined with in situ heating allowed for the visualisation of non-uniform vortex states present in saturation remanent structures,(More)
The thermal demagnetization of pseudo-single-domain (PSD) magnetite (Fe3O4) particles, which govern the magnetic signal in many igneous rocks, is examined using off-axis electron holography. Visualization of a vortex structure held by an individual Fe3O4 particle (~250 nm in diameter) during in situ heating is achieved through the construction and(More)