tailieunhanh - Báo cáo hóa học: " Influence of structure of iron nanoparticles in aggregates on their magnetic properties"

Tuyển tập các báo cáo nghiên cứu về hóa học được đăng trên tạp chí hóa hoc quốc tế đề tài : Influence of structure of iron nanoparticles in aggregates on their magnetic properties | Rosická and Sembera Nanoscale Research Letters 2011 6 527 http content 6 1 527 o Nanoscale Research Letters a SpringerOpen Journal NANO EXPRESS Open Access Influence of structure of iron nanoparticles in aggregates on their magnetic properties Dana Rosická and Jan Sembera Abstract Zero-valent iron nanoparticles rapidly aggregate. One of the reasons is magnetic forces among the nanoparticles. Magnetic field around particles is caused by composition of the particles. Their core is formed from zero-valent iron and shell is a layer of magnetite. The magnetic forces contribute to attractive forces among the nanoparticles and that leads to increasing of aggregation of the nanoparticles. This effect is undesirable for decreasing of remediation properties of iron particles and limited transport possibilities. The aggregation of iron nanoparticles was established for consequent processes Brownian motion sedimentation velocity gradient of fluid around particles and electrostatic forces. In our previous work an introduction of influence of magnetic forces among particles on the aggregation was presented. These forces have significant impact on the rate of aggregation. In this article a numerical computation of magnetic forces between an aggregate and a nanoparticle and between two aggregates is shown. It is done for random position of nanoparticles in an aggregate and random or arranged directions of magnetic polarizations and for structured aggregates with arranged vectors of polarizations. Statistical computation by Monte Carlo is done and range of dominant area of magnetic forces around particles is assessed. Keywords structure of aggregates iron nanoparticles aggregation magnetic forces 1 Introduction Zero-valent iron nanoparticles nZVI composed of iron Fe0 and its oxides are spherical particles with diameter approximately 40 nm and with a large specific surface. These particles are used for decontamination of groundwater and soil and especially .