Magnetic properties of synthesized nanoparticles with different morphologies quantified using shape descriptors

Predmet istraživanja ove doktorske disertacije je uticaj strukture i oblika nanočestica na njihove magnetne karakteristike. Cilј istraživanja je da se kvantifikuju oblici sintetisanih feri-oksidnih nanočestica na slikama dobijenim transmisionom elektronskom mikroskopijom (TEM) i da se izvrši karakterizacija njihovih magnetnih svojstava. Karakterizacija i analiza su urađene za sintetisane nanočestične materijale dobijene sol-gel metodom, hidrotermalnom metodom, kombinovanom metodom taloženja i koloidne hemije, kao i korišćenjem metode samosagorevanja rastvora. Realna slika sintetisanih nanočestica (veličina i oblik sintetisanih nanočestica) u uzorcima su ispitivani pomoću transmisione elektronske mikroskopije. Iz dobijenih mikroskopskih merenja izvršeno je izračunavanje cirkularnosti, orijentabilnosti, eliptičnosti i izduženosti oblika sintetisanih čestica. Algoritmi za analizu oblika su implementirani u programskom paketu MATLAB. Prikazana je i distribucija čestica prema obliku i veličini nanočestica kako bi se dobila što verodostojnija slika ispitivanih uzoraka. Određene su veličina i oblik nanočestica, saturaciona magnetizacija i koercitivna sila sintetisanih nanočestica. Magnetna karakterizacija sintetisanih uzoraka je urađena VSM i SQUID magnetometrima. Pokazano je da se promenom oblika i strukture nanočestica mogu menjati magnetne karakteristike nanomaterijala, što je veoma interesantno za fundamentalna istraživanja i praktične primene. Očekuje se da će rezultati ove doktorske disertacije doprineti bolјem razumevanju uticaja oblika nanočestica na magnetne karakteristike, novim teorijskim modelima, unapređenju metoda sinteze i praktičnih primena nanočestičnih materijala.The subject of this doctoral dissertation is the influence of the structure and shape of nanoparticles on their magnetic properties. The aim of the research was to quantify shapes of synthesized ferric oxide nanoparticles on images obtained by transmission electron microscopy (TEM) and to carry out a characterization of their magnetic properties. Characterization and analysis were performed for synthesized nanoparticle materials obtained by sol-gel method, hydrothermal method, using a combined method of deposition and colloid chemistry, as well as using the self-combustion method. The real images of the synthesized nanoparticles (size and shape of the synthesized nanoparticles) in the samples were examined using transmission electron microscopy. On the basis of the obtained microscopic measurements, the calculation of shape circularity, orientability, ellipticity and elongation of the synthesized particles was carried out. The algorithms for the shape analysis are implemented in MATLAB. It shows the distribution of the particle by size and shape of nanoparticles to give a more realistic picture of the samples. The size and shape of the nanoparticles, saturation magnetization and coercive force of the synthesized nanoparticles were determined. Magnetic characterization of the synthesized samples was done by VSM and SQUID magnetometers. It has been shown that by changing the shape and structure of nanoparticles the magnetic properties of nanomaterials that are very interesting for fundamental research and practical applications can be changed. It is expected that the results of this doctoral dissertation will contribute to a better understanding of the shape-dependent magnetic properties, development of new theoretical models, improvement of synthesis methods and practical applications of nanoparticle materials