Elektroforetsko taloženje i karakterizacija hidroksiapatit/lignin i srebro/hidroksiapatit/lignin prevlaka na titanu

Abstract

Cilj ove doktorske disertacije je optimizacija nanošenja tankih hidroksiapatit (HAP) i biokompozitnih hidroksiapatit/lignin (HAP/Lig) prevlaka, kako bez tako i sa srebrom, postupkom elektroforetskog taloženja, kao i karakterizacija ovako dobijenih prevlaka različitim fizičko-hemijskim i biološkim metodama. Prednost korišćenja ovog postupka u odnosu na druge metode nanošenja jeste mogućnost precizne kontrole debljine i morfologije prevlaka. Variranjem vrednosti napona tokom različitog vremena taloženja utiče se na masu prevlake, a prevlake zadovoljavajuće debljine i dobre adhezije su taložene na titanu pri 60 V tokom 45 s. Ispitan je uticaj koncentracije lignina na morfologiju, fazni sastav i termičko ponašanje HAP/Lig prevlaka različitim metodama kao što su skenirajuća elektronska mikroskopija, difrakcija X-zraka, termogravimetrijska analiza, spektroskopija infracrvene svetlosti sa Furijeovom transformacijom u modu totalne refleksije i fotoelektronska spektroskopija X-zracima. Pokazano je da su HAP i HAP/Lig prevlake uspešno sinterovane na temperaturi od 900 °C bez narušavanja kristalne strukture, koja je znatno niža od uobičajene temperature sinterovanja (1200 °C). Izostanak novih faza nakon sinterovanja na difraktogramima sinterovanih prevlaka ukazuje da koncentracija lignina veća od 0,5 mas. % u HAP/Lig prevlakama ima pozitivan efekat na održanje rešetke hidroksiapatita tokom procesa sinterovanja. Rezultati termogravimetrijske analize su pokazali da se termička stabilnost HAP/Lig prevlaka smanjuje sa povećanjem koncentracije lignina. Ispitivanje morfologije HAP/Lig prevlaka SEM analizom su pokazala da jedino HAP/Lig prevlaka sa 1 mas. % Lig pre i posle sinterovanja ima uniformnu površinu bez pukotina. Međutim, u slučaju sinterovanih HAP/Lig prevlaka sa koncentracijama lignina većim od 0,5 mas. % nije primećen veliki porast Ca/P odnosa, što potvrđuje da nema razgradnje HAP rešetke...

The main goal of this PhD thesis is optimization of formation of thin hydroxyapatite (HAP) and biocomposite hydroxyapatite/lignin (HAP/Lig) coatings, with and without silver, by electrophoretic deposition as well as characterization of obtained coatings by various physico-chemical and biological methods. The advantages of this method compared to different methods of ceramic coating deposition are good controll of coating thickness and morphology. The influence of applied voltages during different deposition times was studied, and coatings deposited on titanium at 60 V during 45 s with satisfactory thickness and adhesion properties were proven as a most appropriate ones. The effect of lignin concentration on morphology, phase composition and thermal behaviour of HAP/Lig coatings was investigated by various methods such as scanning electron microscopy, X-ray diffraction, thermogravimetric analysis, attenuated total reflection Fourier transform infrared spectroscopy and X-ray photoelectron spectroscopy. The HAP and HAP/Lig coatings were successfully sintered at 900 °C, which is significantly lower than the usual sintering temperature (1200 °C), without any changes in their crystal structure. It was found that lignin concentration in HAP/Lig coatings higher than 0.5 wt. % protects hydroxyapatite lattice from decomposition, as indicated by absence of new peaks in diffractogram of sintered coatings. The thermogravimetric analysis results, showed that thermal stability of HAP/Lig coatings decreased with increasing of lignin concentration. The morphology investigated by SEM analysis of HAP/Lig coatings, demonstrated that only HAP/Lig coatings with 1 wt. % lignin exhibited uniform surface without fractures before and after sintering. Also, there was no indication of high increase in Ca/P ratio in sintered HAP/Lig coatings with lignin concentration higher than 0.5 wt. %, which represents another confirmation that there was no decomposition of HAP lattice...