Université de Fribourg

Hybrid magnetic iron oxide nanoparticles with tunable field-directed self-assembly

Malik, Vikash ; Pal, Antara ; Pravaz, Olivier ; Crassous, Jérôme J. ; Granville, Simon ; Grobety, Bernard ; Hirt, Ann M. ; Dietsch, Hervé ; Schurtenberger, Peter

In: Nanoscale, 2017, vol. 9, p. 14405-14413

We describe the synthesis of hybrid magnetic ellipsoidal nanoparticles that consist of a mixture of two different iron oxide phases, hematite (α-Fe2O3) and maghemite (γ-Fe2O3), and characterize their magnetic field-driven self-assembly. We demonstrate that the relative amount of the two phases can be adjusted in a continuous way by varying the reaction time during the synthesis, leading to...

Université de Fribourg

Quantification of mass transfers and mineralogical transformations in a thrust fault (Monte Perdido thrust unit, southern Pyrenees, Spain)

Trincal, Vincent ; Charpentier, Delphine ; Buatier, Martine D. ; Grobety, Bernard ; Lacroix, Brice ; Labaume, Pierre ; Sizun, Jean-Pierre

In: Marine and Petroleum Geology, 2014, vol. 55, p. 160–175

In fold-and-thrust belts, shortening is mainly accommodated by thrust faults which are preferential zones for recrystallisation and mass transfer. This study focuses on a detachment fault related to the emplacement of the Monte Perdido thrust unit in the southern Pyrenees. The studied fault zone consists of a 10 m thick intensively foliated phyllonite developed within the Millaris marls, of...

Université de Fribourg

Alburnite, Ag₈GeTe₂S₄, a new mineral species from the Roşia Montana Au-Ag epithermal deposit, Apuseni Mountains, Romania

Tămaş, Călin G. ; Grobety, Bernard ; Bailly, Laurent ; Bernhardt, Heinz-Juergen ; Minuţ, Adrian

In: American Mineralogist, 2014, vol. 99, no. 1, p. 57–64

Alburnite, ideally Ag₈GeTe₂S₄, was discovered in the Cârnicel vein from the Roşia Montana epithermal Au-Ag ore deposit, Apuseni Mountains, Romania. The new mineral is associated with tetrahedrite, galena, pyrite, sphalerite, chalcopyrite, and tellurides (hessite, altaite, and sylvanite). Associated gangue minerals are rhodochrosite, quartz, calcite, and rhodonite. Alburnite was observed...

Université de Fribourg

A closer look at the synthesis and formation mechanism of hematite nanocubes

Malik, Vikash ; Grobety, Bernard ; Trappe, Veronique ; Dietsch, Herve ; Schurtenberger, Peter

In: Colloids and Surfaces A: Physicochemical and Engineering Aspects, 2014, vol. 445, p. 21–29

We have synthesized hematite cube-shaped nanoparticles using different synthesis paths to examine the effect of the intermediate product akaganeite (β-FeOOH) on the size and shape of the final hematite particles. Akaganeite spindles and hematite nanocubes are prepared using forced hydrolysis of iron chloride (FeCl₃) salt. We use a combination of transmission electron microscopy (TEM), high...

Université de Fribourg

Magnetic properties of silica coated spindle-type hematite particles

Reufer, Mathias ; Dietsch, Hervé ; Gasser, U. ; Grobety, Bernard ; Hirt, A. M. ; Malik, Vivek Kumar ; Schurtenberger, Peter

In: Journal of Physics: Condensed Matter, 2011, vol. 23, no. 6, p. 065102

Magnetic properties of particles are generally determined from randomly oriented ensembles and the influence of the particle orientation on the magnetic response is neglected. Here, we report on the magnetic characterization of anisotropic spindle-type hematite particles. The easy axis of magnetization is within the basal plane of hematite, which is oriented perpendicular to the spindle axis. Two...