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U ovom radu nanostrukturni filmovi cirkonijevog dioksida stabilizirani itrijevim oksidom (YSZ) pripravljeni su sol-gel postupkom i tehnikom uranjanja naneseni na podloge od austenitnog nehrđajućega čelika AISI 316L (X2CrNiMo17-2-2). Istraživanje je usmjereno na optimiranje procesnih parametara priprave YSZ filmova. Određen je utjecaj udjela stabilizatora kristalne faze, broja slojeva, brzine nanošenja slojeva, vremena kvašenja te temperature i atmosfere toplinske obrade. Za karakterizaciju sol-gel filmova ZrO2 i njegovih praškastih oblika korištene su sljedeće analitičke tehnike: difrakcija rentgenskog zračenja u polikristalnom uzorku (PXRD), infracrvena spektroskopija s Fourierovom transformacijom (FTIR), Ramanova spektroskopija, diferencijalna toplinska analiza/termogravimetrija (DTA/TG) i diferencijalna pretražna kalorimetrija/termogravimetrija (DSC/TG), analiza oslobođenih plinova sa spektrometrijom masa (EGAMS), optička emisijska spektrometrija s tinjajućim izbojem (GDOES), pretražna elektronska mikroskopija uz energijski razlučujuću rentgensku spektroskopjiu (SEM/EDS) te mikroskopija atomskih sila (AFM). Istraživanja korozijske otpornosti nezaštićenog nehrđajućega čelika te čelika prevučenog nanostrukturnim sol-gel ZrO2 filmovima provedena su elektrokemijskim mjernim tehnikama potenciodinamičke polarizacije (Tafelova ekstrapolacija) i elektrokemijske impedancijske spektroskopije (EIS) u mirujućem simuliranom morskom okolišu (3,5%-tna vodena otopina NaCl). Dugotrajnost zaštite koju pružaju keramički filmovi ispitana je elektrokemijskom impedancijskom spektroskopijom (EIS). Elektrokemijskim mjerenjima utvrđeno je da nanostrukturni sol-gel ZrO2 filmovi, posebice troslojni filmovi toplinski obrađeni u vakuumu na temperaturi 400 C, značajno povećavaju korozijsku postojanost nehrđajućega čelika u 3,5%-tnoj vodenoj otopini NaCl. Abstract In this thesis nanostructured films of zirconia stabilized with yttria were prepared by sol-gel method and deposited on the austenitic stainless steel AISI 316L (X2CrNiMo17-2-2) surface by dip coating method. Process parameters optimisation for YSZ films was the aim of the study. Influence of the amount of crystal structure stabiliser, number of layers, withdrawal speed, soaking time, temperature and atmosphere of thermal processing were determined. For the characterization of sol-gel ZrO2 films and its powders following analytical techniques were used: powder X-ray diffraction (PXRD), Fourier transform infrared (FTIR) and Raman spectroscopies, differential thermal/thermogravimetric analysis (DTA/TG), differential scanning calorimetry/thermogravimetric analysis (DSC/TG), evolved gas analysis-mass spectrometry (EGAMS), glow-discharge optical emission spectrometry (GDOES), scanning electron microscopy with energy dispersive X-ray spectroscopy (SEM/EDS), atomic force microscopy (AFM). Electrochemical corrosion behaviour of the sol-gel ZrO2 films coated and uncoated stainless steel substrates was evaluated by electrochemical tests such as Tafel extrapolation and electrochemical impedance spectroscopy (EIS) in simulated marine environment (3.5 wt.% aqueous NaCl solution). Electrochemical tests confirmed that protection longevity of nanostructure sol-gel ZrO2 film, especially 3 layered films, thermally processed at 400 C in vacuum, significantly increased corrosion stability of stainless steel in 3.5 wt.% NaCl solution.

In this paper, one layer and three layers of yttria stabilized sol-gel ZrO2 thin films were deposited on the X2CrNiMo17-12-2 (AISI 316L) austenitic stainless steel by dip coating method. For the preparation of sol zirconium(IV) butoxide was used as pre-cursor, i-propanol as a solvent with addition of nitric acid as a catalyst, acetylacetone as chelating agent and water for hydrolysis. Deposited films were calcined at the temperature of 400 °C. Thickness of sol-gel ZrO2 films deposited on stainless steel was determined by glow- discharge optical emission spectrometry (GD- OES). It was found that thickness of deposited films increases by increasing the number of layers.

Sol-gel derived zirconia, ZrO2 (stabilized by yttria in 5 mol %) nanocrystals (5YSZ) were annealed at different temperatures in different atmosphere conditions (air and vacuum) and investigated. Prepared samples were characterized by X-ray diffraction (XRD), differential thermal analysis (DTA), Fourier- transform infrared spectroscopy (FT-IR) and micro-Raman spectroscopy. The results of DTA and XRD analysis show the zirconia crystallization onset at temperature no lower than 400 ºC. Average crystallite size of the 5YSZ annealed in air at 400, 600, 700 and 800 °C were calculated to be 10, 15, 22 and 33 nm, respectively. On the other hand, crystallite size remains in the range 4–13 nm when the heat treatment was conducted in vacuum. Annealing atmosphere affects crystallization, resulting in lower thermal treatment requirements and enabling controlled crystallite growth. XRD and micro-Raman spectroscopy showed nanocrystalline 5YSZ samples were successfully stabilized in the tetragonal phase and preserved phase stability over the investigated thermal treatment range.

In this paper, sol-gel process, as a relative simple and low-cost method, was used for deposition of ceramic films on stainless steel substrate. Mixed TiO2–ZrO2 (1:1) sol–gel films were deposited on the X2CrNiMo17-12-2 (AISI 316L) austenitic stainless steel by dip coating method. For the sol preparation, titanium isopropoxide and zirconium butoxide were used as precursors, i-propanol as a solvent with addition of nitric acid as a catalyst, acetylacetone for peptization and water for hydrolysis. One-layer deposited films were annealed at the temperature of 400 °C and 600 °C. The surface topography, as well as roughness parameters (Ra, Rq, Rmax and the Zrange values) of sol-gel TiO2–ZrO2 films were analysed by atomic force microscopy (AFM).

In this paper, one layer and three layers of yttria stabilized sol-gel ZrO2 thin films were deposited on the X2CrNiMo17-12-2 (AISI 316L) austenitic stainless steel by dip coating method. For the preparation of sol zirconium(IV) butoxide was used as pre-cursor, i-propanol as a solvent with addition of nitric acid as a catalyst, acetylacetone as chelating agent and water for hydrolysis. Deposited films were calcined at the temperature of 400 °C. Thickness of sol-gel ZrO2 films deposited on stainless steel was determined by glow-discharge optical emission spectrometry (GD-OES). It was found that thickness of deposited films increases by increasing the number of layers. Electrochemical impedance spectroscopy (EIS) and potentiodynamic polarization in simulated marine environment (3.5 wt. % NaCl aqueous solution) were used to de-termine the corrosion behaviour of ZrO2 coated stainless steel. The influence of ZrO2 layers number on the degree of the protection was examined as well. It was found that the sol-gel ZrO2 films are able to make an appreciable improvement in the corrosion resistance of stainless steel in the investigated corrosive medium.

In this paper, sol-gel TiO2−ZrO2 films with one layer, three layers and five layers were deposited on the X2CrNiMo17-12-2 (AISI 316L) austenitic stainless steel by dip coating method. Calcination was carried out at 400 °C and 600 °C. For quantitative depth profile analysis of sol-gel TiO2−ZrO2 films the following two different analytical techniques were used and compared: glow-discharge optical emission spectrometry (GD-OES) and time-of-flight elastic recoil detection analysis (TOF-ERDA). Obtained results of GD-OES and TOF-ERDA spectrometry indicated that the depth of the deposited films was increased by increasing the number of deposited layers as well as by increasing the calcination temperature. It was found that the thickness of deposited sol-gel TiO2−ZrO2 films varied from 8 to 95 nm, depending on the number of layers and the calcination temperature. Also, it was found that diffusion of some elements (mainly Cr and Fe) from substrate through interface and film was increased by increasing the calcination temperature. Results obtained by GD-OES and TOF-ERDA indicated that both techniques are excellent tools in the field of surface engineering and can be successfully used for determining elemental composition as a function of depth.

Sol-gel TiO2–ZrO2 films with one layer were deposited on the X2CrNiMo17-12-2 (AISI 316L) austenitic stainless steel by dip coating method. For the preparation of sol titanium isopropoxide and zirconium butoxide were used as precursors, i-propanol as a solvent with addition of nitric acid as a catalyst, acetylacetone for peptization and water for hydrolysis. Deposited films were calcined at the temperature of 400 °C and 600 °C. Thickness of sol-gel TiO2–ZrO2 films deposited on stainless steel was determined by glow-discharge optical emission spectrometry (GD-OES). It was found that thickness of deposited films increases by increasing the temperature of heat treatment. Morphology and phase composition of sol-gel TiO2–ZrO2 films were analysed by atomic force microscopy (AFM) and X-ray diffraction (XRD), respectively. Electrochemical impedance spectroscopy (EIS) in simulated marine environment (3 wt. % NaCl aqueous solution) was used to determine corrosion properties of TiO2–ZrO2 films. It was found that the sol-gel TiO2–ZrO2 films are able to make an appreciable improvement in the corrosion resistance of the stainless steel in investigated corrosive medium.