Razvoj faza u sustavu ZrO2-SiO2 tijekom termičke obrade amorfnih prekursora

master's thesis

• Title (english): Phase development of the ZrO2-SiO2 system during the thermal treatment of amorphous precursors
• Author: Šejla Zukić
• Mentor: Juraj Šipušić (mentor)
• Committee member: Juraj Šipušić (predsjednik povjerenstva)
• Committee member: Stanislav Kurajica (član povjerenstva)
• Committee member: Goran Štefanić (član povjerenstva)
• Granter: University of Zagreb; Faculty of Chemical Engineering and Technology; Zagreb
• Defense date and country: 2017-09-27, Croatia
• Scientific / art field, discipline and subdiscipline: TECHNICAL SCIENCES; Chemical Engineering; Chemical Engineering in Material Development

Abstract

Tema ove radnje bila je proučiti utjecaj termičke obrade na fazni razvoj sustava ZrO2-SiO2. Uparavanjem otopina Zr-propoksida i silicijeva tetraetoksisilana (TEOS) dobiveni su amorfni prekursori sustava ZrO2-SiO2 s različitim molarnim udjelima silicija (od 0 do 100 %). Kristalizacija dobivenih praškastih uzoraka provedena je ţarenjem na zraku, tijekom 2 h na temperaturama od 400 °C, 600 °C, 800 °C, 1000 °C, 1200 °C i 1400 °C. Rendgenskom difrakcijskom analizom na prahu i Ramanovom spektorskopijom provedena je strukturna analiza produkata žarenja. DTA/TGA analizom određena je temperatura kristalizacije cirkonijeva dioksida i gubitak mase tijekom žarenja, a SEM analiza je dala podatke o morfologiji i veličini kristalnih zrnaca. Kvantitativna analiza polimorfa ZrO2 provedena je Rietveldovim utočnjavanjem difrakcijskih slika praha. Dobiveni rezultati pokazuju da porast udjela SiO2 znatno povećava temperaturu kristalizacije cirkonijevog dioksida, od 420 °C (uzorka s 0 mol% SiO2) do 928 °C (uzorka sa 70 mol% SiO2). Iako u provedenim uvjetima termičke obrade nije došlo do značajnije ugradnje silicijevih kationa u ZrO2 rešetku, rezultati strukturne analize su pokazali da prisutnost SiO2 znatno povećava otpornost metastabilne tetragonske modifikacije cirkonijevog dioksida na utjecaj temperature. Ispitan je i utjecaj tlačnog naprezanja na faznu transformaciju ZrO2, a dobiveni rezultati su pokazali da stabilnost tetragonske modifikacije ZrO2 znatno raste sa smanjenjem veličine kristalnih zrnaca. SiO2 povećava otpornost tetragonskog ZrO2 na utjecaj tlačnog naprezanja tek kada je prisutan u vrlo velikim udjelima (80 mol%). Rezultati SEM analize su pokazali da su kod uzoraka s velikim udjelima silicija kristalna zrnca ZrO2 prekrivena amorfnim SiO2 što utječe na smanjenje brzine nukleacije i rasta kristala. Povećanjem udjela silike i smanjenjem temperature, smanjuje se veličina kristalnog zrna.

Abstract (english)

The topic of this thesis was to study the influence of thermal treatment on the phase development of ZrO2-SiO2 system. ZrO2-SiO2 amorphous precursors were obtained by the evaporation of Zr-propoxide and silicon tetraethoxysilane (TEOS) solutions, with different molar fraction of silicon (from 0 to 100%). Crystallization of the obtained powder samples was carried out by annealing in the air for 2 h at temperatures of 400 °C, 600 °C, 800 °C, 1000 °C, 1200 °C and 1400 °C. Structural analysis of crystallization products was performed by X-ray powder diffraction and Raman spectroscopy. The DTA/TGA analysis determined the crystallization temperature of zirconium dioxide and the loss of samples mass during annealing and the SEM analysis provided data on morphology and the size of the crystalline grain. Quantitative analysis of the ZrO2 polymorph was carried out by Rietveld refinements on powder diffraction patterns. The obtained results show that the increase in SiO2 content significantly increases the crystallization temperature of zirconium dioxide, from 420 °C (sample with 0 mol% SiO2) to 928 °C (sample with 70 mol% SiO2). Although under the applied thermal processing conditions there was no significant incorporation of Si cations into the ZrO2 lattice, the results of the structural analysis showed that the presence of SiO2 significantly increases the resistance of metastable tetragonal ZrO2 to the influence of temperature. The influence of pressure on the phase transitions of ZrO2 was also investigated, and the obtained results showed that the stability of the tetragonal ZrO2 significantly increased with the decrease of the crystal grain size. SiO2 increases the resistance of the tetragonal ZrO2 to the impact of pressure only when present in very large proportions (80 mol%). SEM analysis has shown that zirconia crystalline particles are embedded in the amorphous silica gel which affects the nucleation rate and crystal growth. By increasing the silica content and reducing the treatment temperature, the crystalline grain size decreases.

• Keywords: ZrO2; SiO2; XRD; Ramanova spektrometrija; SEM; DTA
• Keywords (english): ZrO2; SiO2; XRD; Ramanspectroscopy; SEM; DTA
• Language: croatian
• URN:NBN: urn:nbn:hr:149:286196
• 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: 2020-04-28 10:58:51