Korozijska otpornost biomedicinskih implantnih materijala na bazi titanija

master's thesis

• Title (english): Corrosion resistance of biomedical titanium-based implant materials
• Author: Sara Krivačić
• Mentor: Jozefina Katić (mentor)
• Committee member: Jozefina Katić (predsjednik povjerenstva)
• Committee member: Marijana Kraljić Roković (član povjerenstva)
• Committee member: Petar Kassal (član povjerenstva)
• Granter: University of Zagreb; Faculty of Chemical Engineering and Technology; Zagreb
• Defense date and country: 2020-12-21, Croatia
• Scientific / art field, discipline and subdiscipline: NATURAL SCIENCES; Chemistry

Abstract

Svrha ovog rada bila je ispitati učinak kalcij-fosfatne biokeramičke prevlake (CaP-prevlaka) na korozijsku otpornost titanijeve legure s aluminijem i niobijem, Ti–6Al–7Nb koja se komercijalno upotrebljava kao implantni materijal u ortopedskim uređajima. Naime, osim što omogućuje oseointegraciju, CaP-prevlaka čini kinetičku barijeru za odvijanje elektrokemijske korozijske reakcije te tako štiti materijal od degradacije uzrokovane korozijom. Time se također povećava biokompatibilnost implantnog materijala. Kalcij-fosfatna prevlaka nanesena je na uzorak Ti–6Al–7Nb elektrokemijskom metodom katodne depozicije. Elektrodepozicija filma kalcijevog fosfata provedena je iz vodene otopine Ca(NO3)2 i NH4H2PO4. Formiranje filma provedeno je u trajanju od 1 h pri dva potencijala elektrodepozicije odabranih na temelju rezultata cikličke voltametrije. Provedena je elektrokemijska karakterizacija Ti–6Al–7Nb legure u simuliranoj fiziološkoj otopini (Hanksovoj otopini). Na taj su način određena elektrokemijska korozijska svojstva legure, koja su uspoređena prije i nakon površinske modifikacije. Korištene su sljedeće elektrokemijske eksperimentalne tehnike: elektrokemijska impedancijska spektroskopija (EIS), linearna polarizacija u širokom, te linearna polarizacija u uskom rasponu potencijala u odnosu na potencijal otvorenog kruga. CaP depozit dodatno je okarakteriziran metodom optičke mikroskopije. Interpretacijom impedancijskih spektara određeno je kako je površina nemodificirane Ti–6Al–7Nb legure prevučena spontano formiranim filmom titanijevog(IV) oksida, TiO2, koji se sastoji od dva dijela, vanjskog (poroznog) te unutarnjeg (barijernog). Ustanovljeno je kako je za korozijsku otpornost nemodificirane legure odgovoran barijerni dio filma TiO2. Temeljem impedancijskih spektara modificiranih uzoraka određeno je kako se površinski film sastoji od dva dijela: vanjskog, koji čini CaP depozit isprepleten s poroznim slojem TiO2; te unutarnjeg, koji se sastoji od barijernog TiO2. Temeljem vrijednosti otpornih komponenata zaključuje se kako CaP depozit doprinosi poboljšanju polarizacijskog otpora Ti–6Al–7Nb legure. Iz rezultata je vidljivo kako je elektrodepozicijom pri Eed = –1,75 V ostvaren kvalitetniji CaP depozit. Ova pretpostavka potvrđena je tehnikama linearne polarizacije.

Abstract (english)

The aim of this study was to examine the effect of calcium-phosphate bioceramic coating (CaP coating) on the corrosion resistance of titanium alloy with aluminum and niobium, Ti–6Al–7Nb which is commercially used as implant material in orthopedic devices. Besides enabling osseointegration, the CaP coating forms a kinetic barrier for the electrochemical corrosion reaction and thus protects the material from degradation caused by corrosion and increases the biocompatibility of the implant material. The CaP coating was applied to the Ti–6Al–7Nb sample by the electrochemical cathodic deposition method. Electrodeposition of calcium phosphate film was performed from an aqueous solution of Ca (NO3)2 and NH4H2PO4. The film formation was performed during 1 hour at two potentials selected based on the cyclic voltammetry results. Electrochemical characterization of Ti–6Al–7Nb alloy in Hanks' balanced salt solution was performed in order to determine the electrochemical corrosion properties of the alloy. Those were compared before and after the surface modification. The following electrochemical experimental techniques were used: electrochemical impedance spectroscopy (EIS) and linear polarization techniques in narrow and wide range versus open-circuit potential. The CaP deposit was further characterized by optical microscopy. By interpreting the impedance spectra, it was determined that the surface of the unmodified Ti–6Al–7Nb alloy was coated with a spontaneously formed film of titanium(IV) oxide, TiO2, which consists of two parts, outer (porous) and inner (barrier). The barrier part of the TiO2 film was found to be responsible for the corrosion resistance of the unmodified alloy. Impedance spectra of the modified samples showed that the surface film consists of two parts: the outer one, which consists of a CaP deposit intertwined with a porous TiO2 layer; and internal, consisting of barrier TiO2. Based on the values of the resistance components, it is concluded that the CaP deposit contributes to the polarization resistance of the Ti–6Al–7Nb alloy. Based on the results, it is concluded that by electrodeposition at Eed = –1,75 V a higher quality CaP deposit was achieved. This assumption was confirmed by the linear polarization techniques.

• Keywords: biokeramički materijali; biokompatibilnost; elektrodepozicija; elektrokemijska karakterizacija; implantni materijali na bazi titanija
• Keywords (english): bioceramic materials; biocompatibility; electrodeposition; electrochemical study; titanium based biomaterials
• Language: croatian
• URN:NBN: urn:nbn:hr:149:191096
• 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)
• Type of resource: Text
• File origin: Born digital
• Access conditions: Closed access
• Created on: 2022-07-19 13:23:43