Sinteza visoko-entropijskog oksida prijelaznih metala postupcima iz otopine

master's thesis

• Title (english): Solution-based synthesis of high-entropy oxide of transition metals
• Author: Iva Lončar
• Mentor: Jelena Macan (mentor)
• Committee member: Jelena Macan (predsjednik povjerenstva)
• Committee member: Zvonimir Katančić (član povjerenstva)
• Committee member: Katarina Mužina (član povjerenstva)
• Granter: University of Zagreb; Faculty of Chemical Engineering and Technology; Zagreb
• Defense date and country: 2024-09-03, Croatia
• Scientific / art field, discipline and subdiscipline: TECHNICAL SCIENCES; Chemical Engineering

Abstract

Cilj ovog rada bila je sinteza visoko-entropijskog oksida kemijske formule (TiZrHfNbTa)O11. Korištena su četiri postupka sinteze: limunski, koprecipitacijski, sol-gel i hidrotermalni. Kao polazni reaktanti za sve četiri sinteze korišteni su kloridi niobija (NbCl5), tantala (TaCl5), hafnija (HfCl4) i cirkonija (ZrCl4) te titanijev butoksid (Ti(C4H9O)). Svi sintetizirani uzorci karakterizirani su infracrvenom spektroskopijom s Fourierovom transformacijom (FTIR) te pretražnom elektronskom mikroskopijom i energijski razlučujućom rendgenskom spektroskopijom (SEM/EDXS). Na temelju SEM/EDXS rezultata zaključeno je da su kod svih sintetiziranih uzoraka udjeli niobija, tantala, hafnija i cirkonija približno jednaki dok je titanija gotovo dvostruko više, što je vjerojatno posljedica njegove veće reaktivnosti budući da se u reakcijsku smjesu uvodi u obliku alkoksida. Uzorci visoko-entropijskih oksida koji su u
SEM/EDXS analizama pokazali najveći stupanj homogenosti i dobro poklapanje množinskih udjela pojedinih elemenata s teorijskim udjelima, dodatno su analizirani rendgenskom difrakcijskom analizom (XRD). Na temelju XRD analize zaključeno je da se dobiveni difraktogrami žarenih visoko-entropijskih oksida podudaraju s literaturnim podacima čime je potvrđeno da su svi primijenjeni postupci prikladni za sintezu HEO ciljanog sastava. Iz difraktograma prekursora dobivenog hidrotermalnim postupkom zaključeno da tim postupkom sinteze nije moguće direktno dobiti oksid bez dodatnog koraka žarenja.

Abstract (english)

The aim of this work was the synthesis of high-entropy oxide with the chemical formula (TiZrHfNbTa)O11. Four synthesis methods were used: citric, coprecipitation, sol-gel, and hydrothermal. Chlorides of niobium (NbCl5), tantalum (TaCl5), hafnium (HfCl4), and zirconium (ZrCl4), as well as titanium butoxide (Ti(C4H9O)), were used as starting reactants for all four syntheses. All synthesized samples were characterized using Fourier-transform infrared spectroscopy (FTIR) and scanning electron microscopy with energy-dispersive X-ray spectroscopy (SEM/EDXS). Based on SEM/EDXS results, it was concluded that the contents of niobium, tantalum, hafnium, and zirconium in all synthesized samples are approximately equal, while the content of titanium is almost twice as high, likely due to its higher reactivity since it is introduced into the reaction mixture in the form of an alkoxide. High-entropy oxide samples that showed the highest degree of homogeneity in SEM/EDXS analyses and good matching of elemental molar ratios with theoretical values were further analyzed using X-ray diffraction analysis (XRD). Based on XRD analysis, it was concluded that the diffractograms of annealed high-entropy oxides match the literature data, confirming that all applied methods are suitable for the synthesis of HEO with the targeted composition. From the diffractogram of the precursor obtained by the hydrothermal method, it was concluded that this synthesis method does not directly yield an oxide without an additional annealing step.

• Keywords: hidrotermalni postupak; koprecipitacijski postupak; limunski postupak; sol-gel postupak; visoko-entropijski oksid
• Keywords (english): hydrothermal synthesis; coprecipitation synthesis; citric synthesis; sol-gel synthesis; high-entropy oxide
• Language: croatian
• URN:NBN: urn:nbn:hr:149:642556
• Study programme: Title: Materials Science and Engineering - Graduate study; Study programme type: university; Study level: graduate; Academic / professional title: sveučilišni/a magistar/magistra inženjer/inženjerka kemijskog inženjerstva (sveučilišni/a magistar/magistra inženjer/inženjerka kemijskog inženjerstva)
• Type of resource: Text
• File origin: Born digital
• Access conditions: Embargoed access; Embargo expiration date: 2026-09-01
• Created on: 2024-09-10 12:20:11