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Hryniewicz T.,Koszalin University of Technology | Rokosz K.,Koszalin University of Technology | Rokicki R.,Electrobright
Materials Letters | Year: 2012

Nanoindentation studies were performed on CP-titanium biomaterial after its treatment under a standard electropolishing (EP) and magnetoelectropolishing (MEP) conditions, with abrasive finishing (MP) carried out on the samples for reference. The Young's modulus of elasticity and nanohardness were investigated. The mechanical properties of titanium biomaterial demonstrated an evident dependence on the surface treatment conditions. After magnetoelectropolishing (MEP) treatment a considerable deviation in mechanical properties of the same Ti biomaterial is observed in comparison with the mechanical properties obtained from the samples after abrasive finishing (MP) and a standard electropolishing (EP). © 2012 Elsevier B.V. All rights reserved.


Hryniewicz T.,Koszalin University of Technology | Konarski P.,Laboratorium Badawczo Pomiarowe Techniki Prozni | Rokosz K.,Koszalin University of Technology | Rokicki R.,Electrobright
Surface and Coatings Technology | Year: 2011

Hydrogen concentration in AISI 316L stainless steel samples was monitored perpendicularly to the flat sample surface up to the depth of 0.8μm, using secondary ion mass spectrometry (SIMS). Depth profile analysis was performed on the samples after electrolytic polishing under different conditions. Analyses were performed on SAJW-05 apparatus with quadrupole Balzers QMA-410 analyzer and Physical Electronics 06-350E ion gun. 5keV Ar+ primary ion beam of 100μm diameter was scanned over 1mm×0.8mm area. Positive (H+, C+, CH+, O+, Cr+, Fe+) and negative (H-, C-, CH-, O-, OH-, CrO-, FeO-) secondary ion emission was registered from central part of the scanned area (10% of area) during primary ion beam sputtering.Results of hydrogen depth profile analysis were compared for the samples after a conventional electrochemical polishing (EP), and magnetoelectropolishing (MEP). Both EP and MEP processes were carried out under the electrochemical conditions regarding also natural and forced convection. The steel samples taken of a hot-rolled sheet, as received (AR), and after abrasive polishing (MP), were used as a reference. Results show that the increased current density (up to 200A/dm2) and electrolyte stirring during electropolishing cause lowering of the hydrogen content in the samples, with the best result regarding hydrogen content decrease obtained on MEP200 sample. In fact, within the MEP process, characteristic with the self-contained electrolyte whirling, the contents of hydrogen are significantly decreased. © 2011 Elsevier B.V.


Rokicki R.,Electrobright | Haider W.,University of Texas–Pan American | Maffi S.K.,University of Texas Health Science Center at San Antonio
Journal of Materials Engineering and Performance | Year: 2014

Research was undertaken to determine the influence of the increased content of chromium in the outermost passive layer of magneto-electrochemically refined Co-Cr alloy L-605 surface on its hemocompatibility. The chemistry, roughness, surface energy, and wettability of conventionally electropolished (EP) and magnetoelectropolished (MEP) samples were studied with x-ray photoelectron spectroscopy (XPS), open circuit potential, atomic force microscopy, and contact angle meter. In vitro hemocompatibility of tested material surfaces was assessed using two important indicators of vascular responses to biomaterial, namely endothelialization and platelets adhesion. The endothelialization was assessed by seeding and incubating samples with human umbilical vein endothelial cells (HUVEC) for 3 days before counting and observing them under a fluorescent microscope. The platelet (rich plasma blood) adhesion and activation test on EP and MEP L-605 alloy surfaces was assessed using a laser scanning confocal microscope. The XPS analysis of MEP samples showed significant enrichment of the passive layer with Cr and O when compared with the EP one. The amount of other elements in the passive layer did not show a significant difference between EP and MEP treatments. The adhesion of HUVEC cells shows remarkable affinity to surfaces enriched in Cr (MEP) with almost 100% confluency. In addition, the number of platelets that adhered to standard EP surfaces was higher compared to the MEP surface. The present study shows that the chromium-enriched surface of cobalt-chromium alloy L-605 by the magnetoelectropolishing process tremendously improves surface hemocompatibility with regard to stent functionality by enhanced endothelialization and lower platelet adhesion and should be taken under consideration as an alternative surface of biodegradable polymer drug-eluting stents, polymer-free drug-eluting stents as well as bare-metal stents. © 2014, ASM International.


PubMed | University of Tennessee at Knoxville, Florida International University, University of Texas–Pan American and Electrobright
Type: | Journal: Materials science & engineering. C, Materials for biological applications | Year: 2015

The constant demand for new implant materials and the multidisciplinary design approaches for stent applications have expanded vastly over the past decade. The biocompatibility of these implant materials is a function of their surface characteristics such as morphology, surface chemistry, roughness, surface charge and wettability. These surface characteristics can directly influence the materials corrosion resistance and biological processes such as endothelialization. Surface morphology affects the thermodynamic stability of passivating oxides, which renders corrosion resistance to passivating alloys. Magnetoelectropolishing (MEP) is known to alter the morphology and composition of surface films, which assist in improving corrosion resistance of Nitinol alloys. This work aims at analyzing the surface characteristics of MEP Nitinol alloys by scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS). The wettability of the alloys was determined by contact angle measurements and the mechanical properties were assessed by Nanoindentation. Improved mechanical properties were observed with the addition of alloying elements. Cyclic potentiodynamic polarization tests were performed to determine the corrosion susceptibility. Further, the alloys were tested for their cytotoxicity and cellular growth with endothelial cells. Improved corrosion resistance and cellular viability were observed with MEP surface treated alloys.


PubMed | University of Texas–Pan American, Florida International University, DDE Laboratory and Electrobright
Type: Journal Article | Journal: Journal of biomedical materials research. Part B, Applied biomaterials | Year: 2015

The thrombogenicity of a biomaterial is mainly dependent on its surface characteristics, which dictates its interactions with blood. Surface properties such as composition, roughness wettability, surface free energy, and morphology will affect an implant materials hemocompatibility. Additionally, in the realm of metallic biomaterials, the specific composition of the alloy and its surface treatment are important factors that will affect the surface properties. The utility of magneto-electropolished (MEP) ternary Nitinol alloys, NiTiTa, and NiTiCr as blood contacting materials was investigated. The hemcompatibility of these alloys were compared to mechanically polished (MP) metallic biomaterial counterparts. In vitro thrombogenicity tests revealed significantly less platelet adherence on ternary MEP Nitinol, especially MEP NiTi10Ta as compared to the MP metals (p<0.05). The enhanced anti-platelet-adhesive property of MEP NiTi10Ta was in part, attributed to the Ta2 O5 component of the alloy. Furthermore, the formation of a dense and mixed hydrophobic oxide layer during MEP is believed to have inhibited the adhesion of negatively charged platelets. In conclusion, MEP ternary Nitinol alloys can potentially be utilized for blood-contacting devices where, complications resulting from thrombogenicity can be minimized.


Rokicki R.,Electrobright | Haider W.,University of Texas–Pan American | Hryniewicz T.,Koszalin University of Technology
Journal of Materials Science: Materials in Medicine | Year: 2012

The influence of 6 % sodium hypochlorite (NaClO) treatment on adhesion and proliferation of MC3T3 pre-osteoblast cells seeded on electropolished (EP) and magnetoelectropolished (MEP) nitinol surfaces were investigated. The chemistry, topography, roughness, surface energy, wettability of EP and MEP nitinol surfaces before and after NaClO treatment were studied with X-ray photoelectron spectroscopy (XPS), profilometry, and contact angle meter. In vitro interaction of osteoblast cell and NaClO treated EP and MEP nitinol surfaces were assessed after 3 days of incubation by scanning electron microscopy. The XPS analysis shows that NaClO treatment increases oxygen content especially in subsurface oxide layer of EP and MEP nitinol. The changes of both basic components of nitinol, namely nickel and titanium in oxide layer, were negligible. The NaClO treatment did not influence physico-morphological surface properties of EP and MEP nitinol to a big extent. The osteoblast cells show remarkable adherence and proliferation improvement on NaClO treated EP and MEP nitinol surfaces. After 3 days of incubation they show almost total confluence on both NaClO treated surfaces. The present study shows that NaClO treatment of EP and MEP nitinol surfaces alters oxide layer by enriching it in oxygen and by this improves bone cell-nitinol interaction. © Springer Science+Business Media, LLC 2012.


Hryniewicz T.,Koszalin University of Technology | Konarski P.,Polish Tele and Radio Research Institute | Rokicki R.,Electrobright | Valicek J.,VSB - Technical University of Ostrava
Surface and Coatings Technology | Year: 2012

Hydrogenation of the commercial purity (99%) CP Titanium Grade 2 biomaterial was investigated using the secondary ion mass spectrometry (SIMS) after two finishing electrochemical operations: standard electropolishing (EP), and magnetoelectropolishing (MEP). The SIMS depth profile analyses were carried out right after electropolishing, and again one month later. The mass spectrograms of secondary positive and negative ions were recorded. SIMS spectra reveal higher emission of positive O +, Ti + and TiO + secondary ions which corresponds to higher oxidation of MEP sample. Negative spectra show higher concentration of compounds containing carbon on MEP sample than those of EP sample. Lower content of hydrogen in the near-surface layers in the MEP sample right after the process was revealed. It was found that the concentrations of oxygen and hydrogen alter in time. One month of storage in air causes the contents of hydrogen in EP and MEP samples to be equalized. The SIMS studies performed after a one month period show that the differences in hydrogen contents between EP and MEP samples are not significant. © 2012 Elsevier B.V.


Rokosz K.,Koszalin University of Technology | Hryniewicz T.,Koszalin University of Technology | Rokicki R.,Electrobright
Tehnicki Vjesnik | Year: 2014

XPS (X-ray Photoelectron Spectroscopy) measurements were performed on AISI 316LVM stainless steel tubes of biomaterial samples, serving for stents, after a standard electropolishing (EP), and magnetoelectropolishing (MEP). After electropolishing operations, the samples were kept in a closed foil pack for about four years. The results of XPS analysis indicate a significant difference in the measurement and calculation values, dependent on surface treatment method: EP and/or MEP. The steel surface film composition and PREN (pitting resistance equivalent number) were calculated. The highest numbers of these values were obtained on samples after MEP where both chromium compounds (Cr 2p) and molybdenum (Mo 3d) increased over three times against these values after EP treatment. The calculated PRENMEP (Fe, Cr, Mo, Mn, Ni, P, S, O) = 16,37, with PRENMEP (Fe, Cr, Mo, Mn, Ni, P, S) = 36,89, versus PRENEP (Fe, Cr, Mo, Mn, Ni, P, S, O) = 3,12, with PRENEP (Fe, Cr, Mo, Mn, Ni, P, S) = 8,53. The results obtained point to an advantageous and unusual effect of the magnetic field action during MEP.


Rokicki R.,Electrobright | Hryniewicz T.,Koszalin University of Technology
Transactions of the Institute of Metal Finishing | Year: 2012

Electropolishing is the electrolytic metal finishing process currently widely used in several high tech applications such as cardiovascular and orthopaedic body implants, pharmaceutical and semiconductor installations, superconductive niobium cavities, among others. The process provides a very clean, smooth, Beilby layer free, corrosion resistant surface. Currently, almost any metal, alloy and intermetallic compound can be electropolished, but in spite of that, we still do not have a single commonly accepted electropolishing theory. To make it even more complicated, the electropolishing process is constantly modified by addition of other physical agents and/or forces such as a magnetic field - magnetoelectropolishing, ultrasounds, or by changing the existing process parameters such as switching from direct to pulse current. The existing electropolishing theories differ in many ways from each other but possess one common ingredient, namely the viscous layer. The aim of this work is to show that the viscous layer is not an indispensible prerequisite to achieve a satisfactory electropolishing finish in every metal-electrolyte system. A supplement to the most broadly accepted electropolishing solid film theory by Hoar, namely the enhanced oxidation-dissolution equilibrium theory, is proposed. © 2012 Institute of Metal Finishing.


Rokicki R.,Electrobright
Medical Device and Diagnostic Industry | Year: 2010

Surface inclusions in nitinol stents, causing primary fatigue, corrosion, and nickel leaching sites, are studied. Nitinol inclusions are classified by origin and chemical composition. Classification by origin gives two kind of inclusions such as native that are distributed throughout the whole volume of the material including surfaces, and foreign that are strictly surface phenomena. Local martensitic transformation and stress concentration points are some of the problems that can be created by inclusions. A chemical test, an inclusions test, uses 6% sodium hypochlorite (NaClO) as a reagent and requires 15 minutes of immersion and observation to conclude presence or absence of surface inclusions. Electropolished nitinol implants have shown superior results in research compared with implants finished by other processes in terms of corrosion resistance, biocompatibility, reduced nickel leaching, and fatigue resistance.

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