Thesis
SÍNTESIS Y CARACTERIZACIÓN DE NANOPARTÍCULAS DE HIERRO CERO VALENTE
Autor
ING. OROPEZA ESTRADA, SAMUEL
Institución
Resumen
In recent years there has been a great interest in the field of nanoscience, an area that covers research areas such as physics, chemistry, biology, engineering, medicine, materials science, among others. Nanoscience is defined as the study of phenomena on a scale of 1-100 nm. Nanotechnology is the capacity to create, control and manipulate objects on this scale to produce materials with specific properties. The first attemps to produce nanostructures arose in the 60's, but it was until the 80's when it was reported a systematic study of the properties of these systems.
Nanoparticles can be formed with the most of the elements of the periodic table and can be classified as: organic, inorganic, metallic, semiconducting, ionic or molecular; depending of its components. The carbon nanoclusters, are a special class in which spherical structures, C60, are including; fullerenes and carbon nanotubes. The study of metal nanoparticles is of interest due to the marked difference presented by metals in nanometer scale properties in contrast to the well known structures and properties in bulk state, highlighting the magnetic properties for numerous applications in emerging technologies.
In general the methods used in the synthesis of metal nanoparticles are: milling, gas phase synthesis, chemical vapor deposition, electron beam lithography, and chemical methods. The so-called colloidal method is one of the important chemical methods since it allows a good control in the size distribution as well as the morphology of the final particles.
Several methods to obtain Fe nanoparticles have been reported, however, the synthesis of pure metal nanoparticles is not easy, because they oxidize rapidly. Iron is a soft ferromagnetic material on bulk state, while in nanoparticles, in the range of 20 nm, shows a superparamagnetic behavior.
In this work we report the synthesis, characterization and measurement of properties of Fe0 nanoparticles, which were synthesized from organometallic precursor bis(bis(trymetylsilyl)amido)iron(II) Fe [N (SiMe3) 2] 2. The synthesis of nanoparticles was carried out in a reactor designed to obtain nanoparticles in suspension, adapted with a sampling system in orther to study the kinetics of the nanoparticle formation. The characterization techniques used during this work were: nuclear magnetic resonance (NMR) to identify organometallic precursors, dynamic light scattering (DLS) to determine the distribution of particle diameters, transmission electron microscopy (TEM) to determine the size and structure of the particles.
It was found that the kinetic model that describes the reaction of synthesis of nanoparticles corresponds to a first-order elementary reaction with a rate constant of , this result together with the TEM study were to suggest a slow growth of the nanoparticles, or a nucleation process that remains for the entire reaction time.