A Kinetic Study on the Reduction of Single Magnetite Particle with Melting Products at High Temperature Based on Visual and Surface Analytical Techniques

In this study, the reduction characteristics of single magnetite particles with melting products at high temperature were investigated by using visualization and surface analytical techniques. The morphology evolution, product type, reduction degree, and reduction rate of single magnetite particles during the reduction process were analyzed and compared at different reduction temperatures. The results showed that the morphology of the product formed at the reduction temperature of 1300 °C was a mainly nodular structure. When the reduction temperature was above 1400 °C, the products were melted to liquid and flowed out of the particle to form a layered structure. The morphology of the melted products finally transformed to be root-like in structure on the plate around the unmelted core. Raman spectroscopy was used to determine the product types during the reduction process. Experiments studying the effects of gas flowrate and particle size on the reduction degree were carried out, and the results showed that both increasing the temperature and gas flowrate can increase the reduction degree. The internal/external diffusion influence can be ignored with a particle size smaller than 100 μm and a gas flowrate more than 200 mL/min. However, owing to the resistance of the melted products to gas diffusion, the reduction rates at 1400 and 1500 °C were reduced significantly when the reduction degree increased from 0.5 to 1.0. Conversely, the formation of the liquid enlarged the contact area of the reducing gas and solid–liquid and further increased the reduction degree. The kinetics parameters, including average activation energy and pre-exponential factor, were calculated from the experimental data. The reduction kinetics equation of the single magnetite particle, considering the effect of melted products is also given in this study.

Magnetite nanoparticles for nonradionuclide brachytherapy

Magnetite nanoparticles possess several properties that can make them useful for targeted delivery of radiation to tumors for the purpose of brachytherapy. Such particles are biodegradable and magnetic and can emit secondary radiation when irradiated by an external source. In this work, the dose distribution around a magnetite particle of 10 nm diameter being irradiated by monochromatic X-rays with energies in the range 4–60 keV is calculated.

Wet milling versus co-precipitation in magnetite ferrofluid preparation

Various uses of ferrofluids for technical applications continuously raise the interest in improvement and optimization of preparation methods. This paper deals with preparation of finely granulated magnetite particles coated with oleic acid in hydrocarbon suspensions following either chemical co-precipitation from iron salt precursors or wet milling of micron size magnetite powder with the goal to compare the benefits and disadvantages of each method. Microstructural measurements showed that both methods gave similar magnetite particle size of 10-15 nm. Higher saturation magnetization was achieved for the wet-milled magnetite suspension compared to relatively rapid co-precipitation synthesis. Different efficacies of ferrophase incorporation into kerosene could be related to the different mechanisms of oleic acid bonding to nanoparticle surface. The comparative data show that wet milling represents a practicable alternative to the traditional co-precipitation since despite of longer processing time, chemicals impact on environment can be avoided as well as the remnant water in the final product.