Kontrola rasti zelo majhnih nanodelcev stroncijevega heksaferita med hidrotermalno sintezo

diplomsko delo visokošolskega strokovnega študijskega programa

Leon Stare (Author), Darko Makovec (Mentor)

Abstract

Znano je, da lahko hidrotermalno sintetiziramo zelo majhne nanodelce Sr heksaferita (SrFe12O19) velikosti približno 10 nm. Sinteza takih nanodelcev je mogoča le pri temperaturah malo nad temperaturo njihovega nastanka. Če se temperatura poveča, začnejo nastajati veliki, ploščati kristali heksaferita, ki so posledica Ostwaldove pogrobitve. To onemogoča sintezo nanodelcev, ki bi imeli velikost okoli 30 nm in bi po predvidevanjih izkazovali želene magnetne lastnosti. V diplomskem delu sem se posvetil preučevanju vpliva natrijeve soli karboksimetil celuloze (NaCMC) na rast nanodelcev Sr heksaferita med hidrotermalno sintezo. Predpostavili smo, da se bo NaCMC adsorbiral na površino nastalih nanodelcev in tako uravnaval njihovo rast. Hidrotermalna sinteza poteka z obarjanjem ionov Sr in Fe iz vodnih raztopin z velikim prebitkom hidroksida NaOH in hidrotermalno obdelavo suspenzije oborjenih ionov pri temperaturah nad 100 °C. Sinteza je potekala v eni stopnji ali v dveh stopnjah. Pri sintezi v eni stopnji sem NaCMC dodal v suspenzijo oborjenih ionov, suspenzijo zaprl v avtoklav in segreval pri različnih temperaturah med 180 °C in 300 °C. Pri sintezi v dveh stopnjah pa sem v prvi stopnji sintetiziral zelo majhne nanodelce Sr heksaferita in nato njihovo suspenzijo v drugi stopnji avtoklaviral v prisotnosti NaCMC pri različnih temperaturah. Produkte smo analizirali z rentgensko difraktometrijo in s presevno elektronsko mikroskopijo. Izkazalo se je, da s sintezo v eni stopnji ne dobimo monofaznega produkta. Dodatek primerne količine NaCMC pri sintezi v dveh stopnjah zavre Ostwaldovo pogrobitev, hkrati pa ne zavre popolnoma primarne rasti. Z dodajanjem NaCMC in naknadno hidrotermalno obdelavo sem lahko povečal srednjo velikost zelo majhnih nanodelcev Sr heksaferita na približno 15 nm pri temperaturi 200 °C.

Keywords

nanodelci;hidrotermalna sinteza;heksaferiti;Ostwaldova pogrobitev;

Data

Language:	Slovenian
Year of publishing:	2013
Source:	Maribor
Typology:	2.11 - Undergraduate Thesis
Organization:	UM FKKT - Faculty of Chemistry and Chemical Engineering
Publisher:	[L. Stare]
UDC:	546.42.057:620.3(043.2)
COBISS:	16814870
Views:	1508
Downloads:	86
Average score:	0 (0 votes)
Metadata:

Other data

Secondary language:	English
Secondary title:	Growth control of ultrafine strontium hexaferrite nanoparticles during hydrothermal synthesis
Secondary abstract:	Ultrafine Sr-hexaferrite (SrFe12O19) nanoparticles, approximately 10 nm in size can be synthesized using a hydrothermal method. Synthesis of the ultrafine nanoparticles is only possible at the temperatures just above a formation temperature of the hexaferrite. When the temperature is increased, large, platelet crystals form due to Ostwald ripening. Ostwald ripening makes synthesis of the nanoparticles with the size of approximately 30 nm impossible. In the diploma work I studied the influence of a sodium salt of carboxymethyl cellulose (NaCMC) on the Sr-hexaferrite nanoparticles growth during the hydrothermal synthesis. We assumed that the NaCMC will adsorb onto the surfaces of the formed nanoparticles thus influencing their growth. For the hydrothermal synthesis the Sr and Fe ions are precipitated from the aqueous solution using a high excess of hydroxide NaOH. The suspension of the precipitates is subsequently hydrothermally treated at temperatures above 100 °C. The synthesis was conducted in single step or in two steps. For the single-step synthesis the NaCMC was added into the suspension of the precipitated ions, sealed in an autoclave and heated to different temperatures between 180 °C and 300 °C. For the two-step synthesis ultrafine nanoparticles were synthesized in the first step. The ultrafine nanoparticles were subsequently hydrothermally treated in the presence of NaCMC in the second step. The products were analysed using X-ray diffractometry and transmission electron microscopy. It appeared that the single-phase hexaferrite product cannot be obtained using the single-step synthesis. The addition of the appropriate amount of NaCMC in the two-step synthesis blocked Ostwald ripening, however, did not completely block primary growth of the nanoparticles. That enabled synthesis of the Sr-hexaferrite nanoparticles with average size of approximately 15 nm at the temperature of 200 °C.
Secondary keywords:	nanoparticles;hydrothermal synthesis;hexaferrites;Oswald ripening;
URN:	URN:SI:UM:
Type (COBISS):	Undergraduate thesis
Thesis comment:	Univ. v Mariboru, Fak. za kemijo in kemijsko tehnologijo
Pages:	XI, 34 f.
Keywords (UDC):	mathematics;natural sciences;naravoslovne vede;matematika;chemistry;crystallography;mineralogy;kemija;inorganic chemistry;anorganska kemija;applied sciences;medicine;technology;uporabne znanosti;medicina;tehnika;engineering;technology in general;inženirstvo;tehnologija na splošno;materials testing;commercial materials;power stations;economics of energy;preiskava materiala;blagoznanstvo;energetske centrale;energetika;nanotechnology;nanotehnologija;
ID:	1027396