In the paper, there are presented the analyses of iron Fe2p3/2 and chromium Cr2p3/2 and oxide O1s XPS spectra of surfaces obtained after abrasive and electrochemical polishing with additional treatment as chemical chelating in the solution containing of 10% Citric Acid and 2% Ethylenediaminetetraacetic Acid. There was also performed electro-chelating after mechanical polishing in the electrolyte for chemical chelating. The maximum values of chromium compounds to iron compounds ratio were obtained after electropolishing with and without stirring with chemical chelating in Citric Acid and EDTA and they were in rage from 3.5 to 3.6. The minimum value was obtained for the steel surface after abrasive polishing and electro-chelating and was equal 1.3. After electrochemical polishing and chemical passivation in the surface layer there were detected FeO and Cr(OH)3 as dominated compounds. After abrasive polishing and electro-chelating there were mostly Fe2O3 and Cr2O3.
K. Rokosz, T. Hryniewicz, K. Pietrzak and W. Malorny
The SEM and EDS results of porous coatings formed on pure titanium by Plasma Electrolytic Oxidation (Micro Arc Oxidation) under DC regime of voltage in the electrolytes containing of 500 g zinc nitrate Zn(NO3)2·6H2O in 1000 mL of concentrated phosphoric acid H3PO4 at three voltages, i.e. 450 V, 550 V, 650 V for 3 minutes, are presented. The PEO coatings with pores, which have different shapes and the diameters, consist mainly of phosphorus, titanium and zinc. The maximum of zinc-to-phosphorus (Zn/P) ratio was found for treatment at 650 V and it equals 0.43 (wt%) | 0.20 (at%), while the minimum of that coefficient was recorded for the voltage of 450 V and equaling 0.26 (wt%) | 0.12 (at%). Performed studies have shown a possible way to form the porous coatings enriched with zinc by Plasma Electrolytic Oxidation in electrolyte containing concentrated phosphoric acid H3PO4 with zinc nitrate Zn(NO3)2·6H2O.
K. Rokosz, T. Hryniewicz, K. Pietrzak, P. Sadlak and J. Valíček
The purpose of this work is to produce and characterize (chemical composition and roughness parameters) porous coatings enriched in calcium and phosphorus on the titanium (CP Titanium Grade 2) by plasma electrolytic oxidation. As an electrolyte, a mixture of phosphoric acid H3PO4 and calcium nitrate Ca(NO3)2·4H2O was used. Based on obtained EDS and roughness results of PEO coatings, the effect of PEO voltages on the chemical composition and surface roughness of porous coatings was determined. With voltage increasing from 450 V to 650 V, the calcium in PEO coatings obtained in freshly prepared electrolyte was also found to increase. In addition, the Ca/P ratio increased linearly with voltage increasing according to the formula Ca/P = 0.035·U+0.176 (by wt%) and Ca/P = 0.03·U+0.13 (by at%). It was also noticed that the surface roughness increases with the voltage increasing, what is related to the change in coating porosity, i.e. the higher is the surface roughness, the bigger are pores sizes obtained.
K. Rokosz, T. Hryniewicz, S. Raaen, D. Matýsek, Ł. Dudek and K. Pietrzak
Plasma Electrolytic Oxidation (PEO) known also as Micro Arc Oxidation (MAO) process is widely used to fabricate porous coatings on titanium and its alloys mainly in water- and acid-based solutions to different applications, e.g. in biomaterials, catalysts, and sensors. In the present paper, the SEM, EDS, and XPS results of porous coatings obtained by PEO treatment on titanium in electrolytes based on concentrated phosphoric H3PO4 acid with calcium nitrate tetrahydrate Ca(NO3)2·4H2O, or magnesium nitrate hexahydrate Mg(NO3)2·6H2O, or zinc nitrate hexahydrate Zn(NO3)2·6H2O for 3 minutes at 200 Vpp (peak to peak) with frequency of 50 Hz, are presented. Based on EDS results, the Ca/P, Mg/P, and Zn/P ratios, which equal to 0.95, 0.176, and 0.231, respectively, were found out. The XPS studies of the top 10 nm of the porous layer clearly indicate that it contains mainly phosphates (PO43− and/or HPO42− and/or H2PO4−, and/or P2O74−) with titanium (Ti4+) and calcium (Ca2+) or magnesium (Mg2+), or zinc (Zn2+).
K. Rokosz, T. Hryniewicz, F. Simon and S. Rzadkiewicz
In the paper, the passive surface layers of AISI 304L after standard (EP50) and very-high-current density electropolishing (EP1000) in a mixture of orthophosphoric and sulfuric acids in a 1:4 ratio, are presented. The main finding of the presented studies is enrichment of the steel surface film in chromium: total chromium to total iron ratio was equal to 6.6 after EP50 and to 2.8 after EP1000; on the other hand, chromium compounds to iron compounds ratio was equal to 10.1 after EP50, and 3.9 after EP1000.
Electrochemical polishing of metals and alloys is one of the most currently used finishing treatments, covering metallic biomaterials with complicated shapes (coronary stents, prostheses, etc.). A standard electropolishing (EP) process has been recently modified by including a magnetic field, and called the magnetoelectropolishing (MEP). Many surface properties and even mechanical features may be modified and improved by MEP. The changes are concerned with the surface film composition which undergo a modification. For the present studies, X-ray Photoelectron Spectroscopy (XPS) analysis was applied to measure the surface film composition on AISI 316L stainless steel. In conclusion both Cr-X/Fe-X compounds ratio as well as Cr/Fe total ratio of the 316L steel after EP and MEP were calculated and compared to reveal the advantage of the magnetic field used.
In the paper, the analyses of Fe2p3/2 and chromium Cr2p3/2 XPS spectra with fitting by symmetrical and asymmetrical line shapes as well as using Linear, Shirley and Tougaard Method of Background Subtraction are presented. The calculations are performed on AISI 316L SS biomaterial after magnetoelectropolishing MEP operation. It was found, the chromium-to-iron ratio after magnetoelectropolishing MEP for other analyses could be in the range from 2.2 to 6.2 depending on the line shapes as well as type of backgrounds used to XPS spectra fitting. The most important for comparison the surface layers concerning the Cr/Fe ratio is to use the same line shape and backgrounds for all analyses.
In the paper, the surface layers formed on nickel-titanium alloy during Plasma Electrolytic Oxidation (PEO), known also as Micro Arc Oxidation (MAO), are described. The mixture of phosphoric acid and copper nitrate as the electrolyte for all plasma electrochemical processes was used. Nitinol biomaterial was used for the studies. All the experiments were performed under the voltage of 450 V and current density of 0.3 A/dm2. The main purpose of the studies was to achieve the highest amount of copper in the surface layer versus amount of the copper nitrate in phosphoric acid. The highest copper concentration was found in the surface layer after the PEO treatment in the electrolyte consisting of 150g Cu(NO3)2 in 0.5 dm3 H3PO4. The worst results, in case of the amount of copper in the NiTi surface layer, were recorded after oxidizing in the solution with 5 g Cu(NO3)2.
J. Valíček, M. Držík, T. Hryniewicz, M. Harničárová, K. Rokosz, M. Kušnerová, K. Barčová and D. Bražina
The paper deals with the measurement and identification of surfaces after machining in a non-contact manner. It presents a new modified measurement method and its implementation, the results of intensity distribution in the defocusing plane, their analysis and interpretation. The scanned intensity distribution at the defocusing plane gives information necessary to assess the second derivatives, and thus, surface functions which can be used to determine groove curvatures of the real surface morphology. The proposed method of measurement has proved to be very sensitive in evaluating the differences between surface finishing methods by which the measured surface standards (etalons) were machined. Two methods of machining were chosen: face grinding and planning. By comparing the roughness standard values Ra, there were obtained relationships between these values and the parameter of the characteristic frequency of vertical inequality being measured according to the presented method. A good correlation between the measured and surface standard values with the correlation coefficient taking a range of values from 0.8 to 1 was achieved.
The SEM and EDS results of coatings obtained on pure niobium and titanium alloys (NiTi and Ti6Al4V) by Plasma Electrolytic Oxidation in the electrolytes containing of 300 g and 600 g copper nitrate in 1 litre of concentrated phosphoric acid at 450 V for 3 minutes, are presented. The obtained coatings are porous and consist mainly of phosphorus within titanium and copper. For each coating, the Cu/P ratios were calculated. The maximum of that coefficient was found for niobium and Ti6Al4V alloy oxidised in the electrolyte containing 600 g of Cu(NO3)2 in 1 dm3 of H3PO4 and equaling to 0.22 (wt%) | 0.11 (at%). The minimum of Cu/P ratio was recorded for NiTi and Ti6Al4V alloys oxidised by PEO in electrolyte consisting of 300 g of copper nitrate in 1 dm3 of concentrated phosphoric acid and equals to 0.12 (wt%) | 0.06 (at%). The middle value of that ratio was recorded for NiTi and it equals to 0.16 (wt%) | 0.08 (at%).