Amount Of Magnetic Phase Research Articles

INVESTIGATION OF OFF-STATE VISCOSITY OF MAGNETORHEOLOGICAL (MR) FLUIDS

Bu çalışmada silikon yağ ve demir (Fe) bazlı manyetoreolojik (MR) akışkanlarının kapalı durum (off-state) viskozite özellikleri incelenmiştir. Farklı oranlardaki manyetik faz miktarı (hacmen %5, 10, 20, 30 ve 40) ile hazırlanan MR akışkanlarının rölatif viskozitesinin (ηrel) – manyetik faz miktarına (φ) olan ilişkisi deneysel olarak tespit edilmiştir. Elde edilen veriler Mooney ve Krieger-Dougherty modelleriyle karşılaştırılmıştır. Deneysel sonuçlar MR akışkanın viskozitesinin manyetik faz miktarı ile önemli ölçüde arttığını göstermiştir. Ayrıca viskozite profilleri Mooney modeli ile uyumlu bulunmuştur.

Force acting on a cluster of magnetic nanoparticles in a gradient field: A Langevin dynamics study

Magnetophoretic force acting on a rigid spherical cluster of single-domain nanoparticles in a constant-gradient weak magnetic field is investigated numerically using the Langevin dynamics simulation method. Nanoparticles are randomly and uniformly distributed within the cluster volume. They interact with each other via long-range dipole-dipole interactions. Simulations reveal that if the total amount of particles in the cluster is kept constant, the force decreases with increasing nanoparticle concentration due to the demagnetizing field arising inside the cluster. Numerically obtained force values with great accuracy can be described by the modified mean-field theory, which was previously successfully used for the description of various dipolar media. Within this theory, a new expression is derived, which relates the magnetophoretic mobility of the cluster with the concentration of nanoparticles and their dipolar coupling parameter. The expression shows that if the number of particles in the cluster is fixed, the mobility is a nonmonotonic function of the concentration. The optimal concentration values that maximize the mobility for a given amount of magnetic phase and a given dipolar coupling parameter are determined.

Magnetic properties of olivine basalt: Application to Mars

The natural remanent magnetisation (NRM) of basalt lava containing (oxidised) magnetic phases is usually assumed to be proportional to the weight percent of magnetic phases. It is shown here that olivine basalt has a different behaviour. The NRM intensity increases at an increasing rate with the amount of magnetic phases. This is attributed to the oxidation of olivine during cooling of the basalt that leads to the exsolution of magnetite in a single domain state. In this way, olivine basalt is found to become an order of magnitude more magnetic than basalt that does not contain olivine. A simple explanation for the magnetic anomalies on Mars is offered, based upon these findings and Mössbauer spectroscopy data from Gusev crater on Mars.

The effect of mechanical deformation on magnetic properties and MRI artifacts of type 304 and type 316L stainless steel.

The purpose of this study was to evaluate the influence of composition and deformation of biomedical stainless steels on mechanical properties, magnetic properties, and MRI artifacts. Type 304 and Type 316L samples were prepared using standard wire-drawing techniques. Mechanical properties were determined using standard test methods. The amount of ferromagnetic phase present was estimated using a Severn Gage and x-ray diffraction. Magnetic field attraction and artifacts were determined using previously described techniques. The strength of both steels increased significantly with increasing deformation. None of the type 316L wires transformed to the magnetic phase. The amount of magnetic phase in the type 304 wires increased with increasing deformation. There was no magnetic field attraction, and artifacts were minimal for all of type 316L wires and the undeformed type 304 wire. Deflection and artifacts were significant for the deformed type 304 stainless steel. These results provide guidance regarding the use of type 304 and type 316L stainless steels for bioimplants. In this regard, type 316L stainless steel seems to be a more acceptable material with respect to MR compatibility.