The passivity of AISI 304L and AISI 316L stainless steels in a borate buffer solution, with and without the addition of chloride ions, was studied using cyclic voltammetry and potentiodynamic ...measurements. The passive layers formed by electrochemical oxidation at different passivation potentials on both the stainless steels were studied by X-ray photoelectron spectroscopy, their compositions were analysed as a function of depth, and the cationic fraction of the passive film was determined. The passive films established on the two stainless steels in the borate buffer solution at pH
=
9.3 contained the oxides of two main elements, i.e., Fe and Cr. The oxides of the alloying elements Ni and, optionally, Mo, also contribute to the passive layer. In the presence of chloride ions a strong chromium enrichment was observed in the passive layers.
We investigated micro-threaded stem taper surface and its impact on premature failures, aseptic loosening, and infection in cementless hip endoprostheses. Our study focused on the fretting, and ...crevice corrosion of micro-threaded tapers, as well as the characterization of the microstructure and surface properties of two new and three retrieved Zweymüller stem tapers. The retrieved samples were selected and examined based on the head–stem taper interface being the sole source of modularity with a metallic component, specifically between the Ti alloy taper stem and the ceramic head. To determine the surface chemistry and microstructures of both new and retrieved hip endoprostheses stem taper titanium alloy, scanning -electron microscopy (SEM) was employed for morphological and microstructural analyses. Energy dispersive spectroscopy (EDS) was utilized for characterizing chemical element distribution, and electron backscattered diffraction (EBSD) was used for phase analysis. The roughness of the micro-threated stem tapers from different manufacturers was investigated using an optical profilometer, with standard roughness parameters Ra (average surface roughness) and Rz (mean peak to valley height of the roughness profile) being measured. Electrochemical studies revealed no fretting corrosion in retrieved stem tapers with ceramic heads. Consequently, three retrieved tapers and two new ones for comparison underwent potentiodynamic measurements in Hank’s solution to determine the corrosion rate of new and retrieved stem taper surfaces. The results showed a low corrosion rate for both new and prematurely failed retrieved samples due to aseptic loosening. However, the corrosion rate was higher in infected and low-grade infected tapers. In conclusion, our study suggests that using ceramic heads reduces taper corrosion and subsequently decreases the incidence of premature failures in total hip arthroplasty.
For the improvement of surface roughness, titanium joint arthroplasty (TJA) components are grit-blasted with Al2O3 (corundum) particles during manufacturing. There is an acute concern, particularly ...with uncemented implants, about polymeric, metallic, and corundum debris generation and accumulation in TJA, and its association with osteolysis and implant loosening. The surface morphology, chemistry, phase analysis, and surface chemistry of retrieved and new Al2O3 grit-blasted titanium alloy were determined with scanning electron microscopy (SEM), X-ray energy-dispersive spectroscopy (EDS), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS) and confocal laser fluorescence microscopy, respectively. Peri-prosthetic soft tissue was studied with histopathology. Blasted retrieved and new stems were exposed to human mesenchymal stromal stem cells (BMSCs) for 7 days to test biocompatibility and cytotoxicity. We found metallic particles in the peri-prosthetic soft tissue. Ti6Al7Nb with the residual Al2O3 particles exhibited a low cytotoxic effect while polished titanium and ceramic disks exhibited no cytotoxic effect. None of the tested materials caused cell death or even a zone of inhibition. Our results indicate a possible biological effect of the blasting debris; however, we found no significant toxicity with these materials. Further studies on the optimal size and properties of the blasting particles are indicated for minimizing their adverse biological effects.
We studied inflammatory and oxidative stress-related parameters and cytotoxic response of human umbilical vein endothelial cells (HUVEC) to a 24 h treatment with milled particles simulating debris ...involved in sandblasting of orthopedic implants (OI). We used different abrasives (corundum-(Al
O
), used corundum retrieved from removed OI (u. Al
O
), and zirconia/silica composite (ZrO
/SiO
)). Morphological changes were observed by scanning electron microscopy (SEM). Concentration of Interleukins IL-6 and IL-1β and Tumor Necrosis Factor α (TNF)-α was assessed by enzyme-linked immunosorbent assay (ELISA). Activity of Cholinesterase (ChE) and Glutathione S-transferase (GST) was measured by spectrophotometry. Reactive oxygen species (ROS), lipid droplets (LD) and apoptosis were measured by flow cytometry (FCM). Detachment of the cells from glass and budding of the cell membrane did not differ in the treated and untreated control cells. Increased concentration of IL-1β and of IL-6 was found after treatment with all tested particle types, indicating inflammatory response of the treated cells. Increased ChE activity was found after treatment with u. Al
O
and ZrO
/SiO
. Increased GST activity was found after treatment with ZrO
/SiO
. Increased LD quantity but not ROS quantity was found after treatment with u. Al
O
. No cytotoxicity was detected after treatment with u. Al
O
. The tested materials in concentrations added to in vitro cell lines were found non-toxic but bioactive and therefore prone to induce a response of the human body to OI.
Thin oxide layers were produced by exposure of polished and sputter-cleaned stainless steel samples to approximately 10
−5 mbar oxygen administered into the fast entry chamber previously pumped down ...to 10
−8 mbar. XPS as well as AES depth profiling determined principal constituents of the oxide layer as chromium and iron oxides and estimated layers to be in the nanometer range (of the order of 2–3 nm). Since thickness estimations obtained by depth profiling depend on sample stoichiometry, which may be changed by the very process of the profiling measurement, independent determination of oxide layers thicknesses by means of a non-destructive technique was also performed. A simple method was used to estimate oxide layer thickness from the peak intensity ratio vs. emission angle measurements. Full ARXPS was also attempted. For angular dependent XPS measurements, a special tilted sample holder was used to translate the instrument's available sample tilt into an emission angle range from 0 to 75°. Thus, sets of metallic/oxide peaks from Fe 2p
3/2 and Cr 2p
3/2 were measured for different angles. From these data, thickness estimations were derived that were roughly in agreement with thickness estimations obtained from depth profiling data. These estimations were, however, grouped around two distinct values, depending on types of metallic peaks used, which may suggest that even these ultrathin layers are formed of two distinct sublayer types.
Cu–Al–Ni shape memory alloys (SMAs) have been investigated as materials for medical devices, but their biomedical application is still limited. The aim of this work was to compare the microstructure, ...corrosion and cytotoxicity in vitro of a Cu–Al–Ni SMA. Rapidly solidified (RS) thin ribbons, manufactured via melt spinning, were used for the tests. The control alloy was a permanent mould casting of the same composition, but without shape memory effect. The results show that RS ribbons are significantly more resistant to corrosion compared with the control alloy, as judged by the lesser release of Cu and Ni into the conditioning medium. These results correlate with the finding that RS ribbons were not cytotoxic to L929 mouse fibroblasts and rat thymocytes. In addition, the RS ribbon conditioning medium inhibited cellular proliferation and IL-2 production by activated rat splenocytes to a much lesser extent. The inhibitory effects were almost completely abolished by conditioning the RS ribbons in culture medium for 4weeks. Microstructural analysis showed that RS ribbons are martensitic, with boron particles as a minor phase. In contrast, the control Cu–Al–Ni alloy had a complex multiphase microstructure. Examination of the alloy surfaces after conditioning by energy dispersive X-ray and Auger electron spectroscopy showed the formation of Cu and Al oxide layers and confirmed that the metals in RS ribbons are less susceptible to oxidation and corrosion compared with the control alloy. In conclusion, these results suggest that rapid solidification significantly improves the corrosion stability and biocompatibility in vitro of Cu–Al–Ni SMA ribbons.
A microstructural characterization of the powder-metallurgy high-speed-steel S390 Microclean was performed based on an elemental distribution of the carbide phase as well as crystallographic ...analyses. The results showed that there were two types of carbides present: vanadium-rich carbides, which were not chemically homogeneous and exhibited a tungsten-enriched or tungsten-depleted central area; and chemically homogeneous tungsten-rich M
6C-type carbides. Despite the possibility of chemical inhomogenities, the crystallographic orientation of each of the carbides was shown to be uniform. Using electron backscatter diffraction the vanadium-rich carbides were determined to be either cubic VC or hexagonal V
6C
5, while the tungsten-rich carbides were M
6C. The electron backscatter diffraction results were also verified using X-ray diffraction. Several electron backscatter diffraction pattern maps were acquired in order to define the fraction of each carbide phase as well as the amount of martensite phase. The fraction of martensite was estimated using band-contrast images, while the fraction of carbides was calculated using the crystallographic data.
The surface oxidation of duplex stainless steel (DSS 2205) was studied by X-ray photoelectron spectroscopy (XPS). The experiments were performed on the alloy after controlled oxidation in a ...chloride-enriched solution at controlled potentials. The evolution of the passive film formed on the DSS in a chloride solution was studied using cyclic voltammetry with XPS surface characterization at selected potentials. The evolution of the oxide films and its specific compositions formed on the DSS was studied as a function of depth. Fe/Cr oxidized layers and oxide thicknesses were observed and correlated with the various potentiostatic potentials. The importance of Mo and Cr inside the oxide films in this article is studied and described, whereas their role in the protective layer, as oxides, is significant.
SiO
x
-like coatings were deposited on glass slides from a hexamethylsiloxane precursor by plasma-assisted CVD (PACVD). Surface energies (23.1-45.7 mJ m
−1
) were correlated with the degree of ...surface oxidation and hydrocarbon contents. Tapping mode AFM revealed a range of surface topologies with Ra values 1.55-3.16 nm and RMS roughness 1.96-4.11 nm. Settlement of spores of the green alga Ulva was significantly less, and detachment under shear significantly more on the lowest surface energy coatings. Removal of young plants (sporelings) of Ulva under shear was positively correlated with reducing the surface energy of the coatings. The most hydrophobic coatings also showed good performance against a freshwater bacterium, Pseudomonas fluorescens, significantly reducing initial attachment and biofilm formation, and reducing the adhesion strength of attached bacterial cells under shear. Taken together the results indicate potential for further investigation of these coatings for applications such as heat exchangers and optical instruments.
PDF
