Solid State Phenomena Vol. 227

Abstract: The aim of this work which is a part of larger approach, is the surface functionalization by means of plasma electrolytic oxidation (PEO) as a pretreatment prior to the application of biopolymer. The process was developed for the number of magnesium alloys, and AZ31, RZ5 and ZM21 in particular. An oxide layer was formed in two step consecutive process in KOH-Na₃PO₄ and KOH-NaF solutions. The coatings are built from sub-layers: reach in F at the metal-coating interface containing small pores and top layer with larger pores. An important feature for the surface biocompatibility is a presence and distribution of P within the top part of the coating which create a nucleation sites for the development of calcium phosphates. From the results of long term impedance measurements carried out in simulated body solution (SBF) at 37°C it may be concluded that the best corrosion protection is provided by the anodic layer formed on AZ31 alloy. After the testing the surface of alloys studied in this work was covered by a film of compounds containing calcium and phosphorus.

Abstract: This paper presents the results of investigations on electrolytic polishing and anodic passivation of Ti-15Mo alloy. The influence of chemical composition of the bath used in electrolytic polishing and anodic passivation process on the morphology, wettability and corrosion resistance of the electrochemically modified vanadium-free Ti-15Mo alloy was presented. The electropolishing process was carried out in a solution containing: sulphuric acid, ethylene glycol, ammonium fluoride and oxalic acid. Moreover, the anodic oxidation process was carried out in a 1.0 M H₂SO₄, 1.0 M H₃PO₄ and 0.5 M solution of K₂SiO₃ and 5 g/dm³ KOH. It was found that the electrolytic polishing and anodic passivation led to significant improvement of the surface morphology. The electrolytic polishing and anodic passivation of Ti-15Mo improved corrosion resistance of the alloy in contact with of Ringer's physiological solution. The samples anodised at 100 V in 1.0 M H₃PO₄ presented the highest corrosion resistance.

Abstract: The influence of temperature change of isotonic 0.9 % NaCl solution and Ringer's solution from 36 ^оС to 40 ^оС on the corrosion resistance of Ti-6Al-4V alloy with nitride and oxynitride coatings was studied. It was shown that increase of the temperature of 0.9 % NaCl and Ringer's solutions doesn′t deteriorate the protective function of oxynitride coating on Ti-6Al-4V alloy. It was determined that by increasing the temperature of Ringer's solution the corrosion processes on nitride coating are accelerated, while in 0.9 % NaCl the nitride coating provides the stable characteristics.

Abstract: In the present paper we report the acquisition of a composite coating based on cobalt and ultra high molecular weight polyethylene (Co/UHMWPE) as a novel hybrid biocoating with potential application as a biomaterial, using the electrochemical deposition technique at room temperature. Three different concentrations of UHMWPE, namely 20 gL-1, 30 gL-1 and 50 gL-1, were used in a cobalt sulphate bath. The corrosion behaviour of the Co/UHMWPE hybrid biocoating was studied in comparison with pure cobalt coating at different exposure times in Hanks’ solution as simulated body fluid (SBF), using the electrochemical impedance spectroscopy method. The polarisation resistance of the Co/UHMWPE hybrid biocoating increased during immersion time in the SBF medium in comparison to the pure cobalt coating. An easy way to prepare Co/UHMWPE hybrid biocoatings was identified: namely, by properly incorporating UHMWPE microparticles into a Co matrix using electrocodeposition from a cobalt electrolyte plating bath with increasing corrosion resistance in a solution simulating body fluid.

Abstract: The aim of the work was the deposition of polymer fibres of submicrometric and nanometric diameter. A layer of the fibres was produced from biocompatible polymer, i.e. poli (ε) caprolactane (PCL). The polymer was dissolved in a mixture of DMF:DCM solvents. In order to enhance the hydrophobic effect, silica particles (5–10 nm) were introduced into the polymer solution. PCL fibres were produced using electric field of 25 kV. Wettability of the produced layer was determined using the method of sitting drop (DSA T500). Its microstructure was observed using scanning an electron microscope (Nova NanoSEM) and an atomic force microscope (MULTIMODE 8 AFM, Bruker). It was revealed that only coatings made of the pure polymer fibres showed superhydrophobicity (PCL fibres, wetting angle of 151^o), while the nanocomposite fibres made of PCL and 3 wt.% SiO₂ formed a layer with a wetting angle of 113^o, which was more hydrophobic than a conventional polymer layer made by casting (wetting angle of PCL foil is 90^o).

Abstract: In this work the assessment of the corrosion performances in saliva solution of NdFeB magnets coated with silane layers was studied for its application in orthodontic brackets. The silane film, deposited by dip coating technique, has been prepared with varying dipping steps, with the purpose to identify the number of layers able to achieve an optimal protective action. Corrosion protection performance, during immersion in Fusayama synthetic saliva solution, was evaluated by means electrochemical impedance spectroscopy (EIS). The silane coatings evidenced good barrier properties resulting in an improvement of the anti-corrosion performances of the magnets. Better results were observed for samples with at least 15 layers of silane, that evidenced still acceptable protective action after three days of immersion in a Fusayama synthetic saliva solution.

Abstract: In this work we shows procedure for new biomaterial - void metal composite (VMC) formation. We used a quasi-spherical sucrose crystals as a space holder material. In the process, titanium powder (different particle sizes) and sucrose were mixed together and uniaxially pressed to make a green compacts. In the next step the sucrose crystals were dissolved in water, leaving open spaces surrounded by metallic scaffold with different porosity (50 – 70%). Such prepared titanium scaffold was dried and sintered in vacuum. The foams morphology was investigated by SEM and CT. The corrosion tests of the as prepared materials were performed in Ringer`s solution using cyclic polarization measurements. We shows that Ti scaffolds prepared by using sucrose as a space holder have corrosion resistance comparable to bulk microcrystalline titanium.

Abstract: The aim of the paper was to compare physicochemical features of hip joint cups coated with hydroxyapatite in the initial state and after period of 36 months of implantation. The cups we produced from stainless steel Cr-Ni-Mo with increased content of azote dedicated to implants which chemical composition is compatible with recommended ISO 5832-9 standards. On the basis of obtained results it can be stated that hydroxyapatite resorption did not affect equally the entire surface of the cup. It was also stated that tested biomaterial of the cup was well wetted (hydrophilic). For all the tested samples prepared from cups in the initial state and cups after the implantation the presence of transpassivation potential E_tr was stated, which proves not only good corrosion resistance but also biocompatibility of analyzed cups.

Abstract: NiTi alloys are used for both medical and veterinary purposes, and also for production of surgical instruments. Sulphate-reducing bacteria (SRB) colonize various anaerobic environments, including human oral cavity. Desulfovibrio desulfuricans is the SRB species responsible for corrosion of many metals including highly alloyed steels as well as titanium and its alloys. The aim of this work was to compare growth of D. desulfuricans biofilms on NiTi alloy submerged in artificial saliva or in inflammatory saliva. The results of investigations showed differences between D. desulfuricans biofilms formed on NiTi alloy in the presence of artificial saliva and inflammatory saliva. The growth medium influenced biofilm structure; inflammatory saliva promotes its formation. The biofilms grown on samples immersed in inflammatory saliva were much thicker as compared with samples emerged in artificial saliva. After 28 days of incubation in inflammatory saliva, plentiful mature biofilm was present on alloy surface.

Abstract: The aim of this study was to investigate the effects of Sn and Mo contents on electrochemical behavior and phase analysis of Ti12Mo23Sn (wt.%) and Ti23Mo12Sn (wt.%) alloys for biomedical applications. The samples were manufactured by blended combining the elemental method from a sequence of uniaxial and cold isostatic pressing with subsequent densification by sintering at 1000°C, in protective gas atmosphere. The corrosion resistance of the studied alloys in Ringer's solution were determined. The structural properties were examined by scanning electron microscopy (SEM + EDS) and X-ray diffraction (XRD). X-ray phase analysis shows two phases: β-Ti and Ti₃Sn for both samples. The proposed quantitative composition of the tested samples was confirmed in the chemical analysis. The results of the electrochemical analysis reveal that the open circuit potentials recorded for the Ti12Mo23Sn and Ti23Mo12Sn samples were quite similar. Moreover, obtained results indicate that the titanium alloy composed of 23 wt.% of Mo and 13 wt.% of Sn exhibited slightly better corrosion resistance than the Ti12Mo23Sn sample with lower concentration of Mo (12 wt%) in the Ringer`s solution.