Title Mikrostruktura elektroispredenih nanovlakana oksida željeza
Title (english) The microstructure of iron oxide nanofibers prepared by electrospinning
Author Gabrijela Radić
Mentor Marijana Kraljić Roković (mentor)
Mentor Željka Petrović (komentor)
Committee member Marijana Kraljić Roković (predsjednik povjerenstva)
Committee member Jozefina Katić (član povjerenstva)
Committee member Željka Petrović (član povjerenstva)
Granter University of Zagreb Faculty of Chemical Engineering and Technology Zagreb
Defense date and country 2019-09-27, Croatia
Scientific / art field, discipline and subdiscipline TECHNICAL SCIENCES Chemical Engineering
Abstract U ovom radu istražena su morfološka, mikrostrukturna, poluvodička i električna svojstva vlakana hematita (α-Fe2O3) dobivenih procesom elektroispredanja pri tri različita protoka prekursorske otopine; 1,5 ml h^-1, 1,0 ml h^-1, 0,5 ml h^-1 i termičkom obradom na 700 °C, 1 h. Rezultati dobiveni EDS, ATR-FTIR, XRD i UV metodama potvrdili su da su dobivena čista α-Fe2O3 vlakna. SEM snimke hematitnih vlakana pokazale su kako njihova veličina (promjer) ovisi o protoku, tj. smanjuje se smanjenjem protoka. Električna svojstva α-Fe2O3 vlakana ispitana su metodom četiri točke, a korištenjem Taucova postupka utvrđeno je kako materijal posjeduje poluvodička svojstva. Loša električna provodnost usmjerila je istraživanje prema stvaranju kompozitnog materijala koji bi imao poboljšana elektrokemijska svojstva. U tu je svrhu hidrotermalnom metodom sintetiziran kompozitni materijal α-Fe2O3/reducirani grafenov oksid (rGO) iz otopina grafenova oksida (GO) i ekstrakta lista masline (ELM) u koje su dispergirana hematitna vlakna. Za ovu namjenu korištena su hematitna vlakna dobivena pri protoku 1,0 ml h^-1. Navedeni postupak provodio se pri pH 4 i pH 10, a dobiveni su kompozitni hidrogelovi. Za svaki uzorak kompozita sintetiziran je i pripadajući referentni rGO hidrogel koji nije sadržavao hematitna vlakna. Za uzorke kompozita α-Fe2O3/rGO i referentne uzorke rGO provedena je strukturna, morfološka i elektrokemijska karakterizacija. Ugradnja α-Fe2O3 vlakana u kompozit potvrđena je SEM i XRD rezultatima, a utvrđeno je i da su vlakna smanjila aglomeraciju listova rGO. Kako bi se provela elektrokemijska mjerenja sastavljeno je 6 simetričnih superkondenzatora koji su ispitani cikličkom voltametrijom (CV), elektrokemijskom impedancijskom spektroskopijom (EIS) i kronopotenciometrijom. Dobiveni rezultati pokazali su pozitivan utjecaj α-Fe2O3 vlakana na kapacitivna svojstva kompozitnog materijala.
Abstract (english) Microstructure of the hematite fibres (α-Fe2O3) obtained by the electrospinning process at three different flow rates of the precursor solution; 1,5 ml h^-1, 1,0 ml h^-1, 0,5 ml h^-1 and thermal processing at 700 °C, 1 h has been investigated. Using EDS, ATR-FTIR, XRD and UV methods it has been confirmed that the obtained fibres consisted only of α-Fe2O3. SEM images of the hematite fibres pointed out the fibre diameter / flow rate correlation, i.e. the slowest flow rate produced fibres with the smallest diameters. Electrical properties of α-Fe2O3 fibres have been examined using the four point probe method and the semiconducting properties have been confirmed using the Tauc model. Due to the low electrical conductivity of hematite the research was directed towards the formation of a composite material with enhanced electrochemical properties. A composite material α-Fe2O3/rGO has been obtained via a hydrothermal method using graphene oxide (GO) and olive leaf extract (ELM) solution with addition of hematite fibres (1,0 ml h^-1). This procedure was carried out at two different pH values; 4 and 10, and as a result composite hydrogels were obtained. In addition to this, for each composite sample a reference hydrogel without hematite fibres was synthesised, rGO. Morphological, structural and electrochemical characterizations have been conducted for the composite (α-Fe2O3/rGO) and reference (rGO) samples. SEM and XRD results confirmed the incorporation of the hematite fibres into the composite material as well as a partial prevention of the rGO sheet agglomeration. In order to carry out electrochemical measurements 6 symmetrical supercapacitors have been assembled and tested by means of cyclic voltametry (CV), electrochemical impedance spectroscopy (EIS) and chronopotentiometry. The obtained results showed a positive effect of the α-Fe2O3 fibres on capacitive properties of the composite material.
Keywords
elektroispredanje
hematit
hidrotermalna sinteza
rGO
superkondenzator
Keywords (english)
electrospinning
hematite
hydrothermal synthesis
rGO
supercapacitor
Language croatian
URN:NBN urn:nbn:hr:149:113431
Project Number: IP-2013-11-8825 Title: Elektrokemijski superkondenzator visoke snage i velikog sadržaja energije za primjenu u električnim vozilima Title: High power-high energy electrochemical supercapacitor for hybrid electric vehicles Acronym: ESUP-CAP Leader: Zoran Mandić Jurisdiction: Croatia Funder: HRZZ Funding stream: IP
Project Number: IP-2016-06-8254 Title: Nastajanje i svojstva 1D a-Fe2O3 nanostruktura dopiranih odabranim metalnim ionima Acronym: 1D-DopedFeOX Leader: Mira Ristić Jurisdiction: Croatia Funder: HRZZ Funding stream: IP
Study programme Title: Applied Chemistry - Graduate study; specializations in: Environmental chemistry and green technologies, Advanced materials and technologies, Applied organic chemistry Course: Advanced materials and technologies Study programme type: university Study level: graduate Academic / professional title: magistar/magistra primijenjene kemije (magistar/magistra primijenjene kemije)
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Created on 2022-02-27 13:27:30