Utjecaj uvjeta priprave na kristalizaciju ZrO2 stabiliziranog itrijem

master's thesis

• Title (english): Influence of preparation conditions on crystallization of yttria-stabilized zirconia
• Author: Lidija Brcković
• Mentor: Jelena Macan (mentor)
• Committee member: Jelena Macan (predsjednik povjerenstva)
• Committee member: Stanislav Kurajica (član povjerenstva)
• Committee member: Juraj Šipušić (član povjerenstva)
• Granter: University of Zagreb; Faculty of Chemical Engineering and Technology; Zagreb
• Defense date and country: 2015-07-07, Croatia
• Scientific / art field, discipline and subdiscipline: TECHNICAL SCIENCES; Basic Technical Sciences; Materials

Abstract

Istraživan je utjecaj uvjeta priprave na kristalizaciju cirkonijeva dioksida stabiliziranog itrijem, pa su u tu svrhu pripremljeni uzorci sol-gel postupkom i mehanokemijskom pripremom. Osim toga kod sol-gel postupka ispitivan je utjecaj prisutnosti Al2O3 (0 % i 20 %) te prethodnog mljevenja na kristalizaciju prašaka, dok je prilikom mehanokemijske pripreme proučavan utjecaj udjela Al2O3 (10, 20 i 30 %). Prašci su kalcinirani na temperaturama 400 – 1200 °C, a prešane su i tablete koje su kalcinirane na 1400 °C.
Kristalizacija prašaka praćena je rendgenskom difrakcijskom analizom, Ramanovom spektroskopijom te simultanom razlikovnom pretražnom kalorimetrijom i termogravimetrijskom analizom. Morfologija tableta ispitana je pretražnim elektronskim mikroskopom, a gustoća im je određena Arhimedovom metodom.
Ustanovljeno je da prisutnost Al2O3 odgađa početak kristalizacije ZrO2, ali je njihova kristalizacija inače nezavisna. Do 1200 °C kristaliziraju tetragonski ZrO2 i korund kao konačne faze. Mljevenje utječe na kristalizaciju sol-gel prašaka, pošto tvori nukleuse dalje kristalizacije.
Kod mehanokemijske pripreme nema utjecaja promjene udjela Al2O3 na kristalizaciju prašaka. Zbog manje homogenosti početnog praška na kraju nastaje i monoklinski ZrO2.
Dobivene tablete su porozne, ali nema znatnije razlike između mehanokemijske pripreme i sol-gel postupka u veličini pora i relativnoj gustoći tableta. Mehanokemijska priprema daje tablete homogenije morfologije, dok je prednost sol-gel postupka dobivanje čiste tetragonske faze.

Abstract (english)

Influence of preparation conditions on the crystallization of yttria-stabilized zirconia was investigated, and for this purpose samples were prepared by sol-gel process and mechanochemical preparation. For the sol-gel process, the influence of the presence of alumina (0% and 20 %) and previous milling on crystallization was examined, while for the mechanochemical preparation influence of alumina content (10, 20 and 30 %) was studied. The powders were calcined at temperatures in 400 – 1200 °C range, while compressed tablets were calcined at 1400 °C.
Crystallization of powders was monitored by X-ray diffraction analysis, Raman spectroscopy and simultaneous differential scanning calorimetry and thermogravimetric analysis. The morphology of the tablets was tested by scanning electron microscope, and their density was determined by Archimedes method.
The presence of alumina was found to delay crystallization of zirconia, otherwise their crystallization is independent. Tetragonal zirconia and corundum crystallize as the final phases at 1200 °C. Milling affects the crystallization of the sol-gel powders since nuclei of further crystallization are formed.
In case of mechanochemical preparation there is no influence of alumina content on powders crystallization. Because of less homogeneous initial powder, monoclinic zirconia is also eventually formed.
The obtained tablets are porous, but there are no significant differences between the mechanochemical preparation and sol-gel process in pore size and the relative density of tablets. Mechanochemical preparation gives tablets with homogeneous morphology, while the advantage of the sol-gel process is preparation of pure tetragonal phase.

• Keywords: ZrO2 stabiliziran itrijem; Al2O3; sol-gel postupak; mehanokemijska priprema; kristalizacija; poroznost
• Keywords (english): yttria-stabilized zirconia; alumina; sol-gel process; mechanochemical preparation; crystallization; porosity
• Language: croatian
• URN:NBN: urn:nbn:hr:149:791352
• Study programme: Title: Materials Science and Engineering - Graduate study; Study programme type: university; Study level: graduate; Academic / professional title: magistar/magistra inženjer/inženjerka kemijskog inženjerstva (magistar/magistra inženjer/inženjerka kemijskog inženjerstva)
• Type of resource: Text
• File origin: Born digital
• Access conditions: Open access
• Created on: 2016-12-07 12:36:42