Electropolished Samples Research Articles

Comparison of electropolished 316L steel samples manufactured by SLM and traditional technology

PurposeThis paper aims to present the way of modifying surfaces of 316L stainless steel elements that were manufactured in the selected laser melting (SLM) technology and then subjected to mechanical and electrolytic processing (electropolishing [EP]). The surface of the as-generated and commercial produced parts was modified by grinding and EP, and the results were compared. The authors also present an example of the application of EP for the final processing of a sample technological model – an initial prototype of a 316L steel implant manufactured in the SLM technology.Design/methodology/approachThe analyzed properties included surface topography, roughness, resistance to corrosion, microhardness and the chemical composition of the surface before and after EP. The roughness described with the Ra, Rt and Rz was determined before and after EP of samples manufactured from 316L steel with use of traditional methods and additive technologies.FindingsEP provides us with the opportunity to process elements with a complex structure, which would not be possible with use of other methods (such as milling or grinding). Depending on the expected final surface of elements after the SLM process, it is possible to reduce the surface roughness with the use of EP (for t = 20 min, Ra = 3.53 ± 0.37 µm and for t = 40 min, Ra = 3.23 ± 0.22 µm) or mechanical processing and EP (for t = 4 min, Ra = 0.13 ± 0.02 µm). The application of the EP method to elements made from 316L steel, in a bath consisting of sulfuric acid (VI), H2SO4 (35 Vol.%), phosphoric acid (V), H3PO4 (60.5 Vol.%) and triethanolamine 99 per cent (4.5 Vol.%), allows us to improve the surface smoothness and to obtain a value of the Ra parameter ranging from 0.11 to 0.15 µm. The application of a current density of 20 A/dm2 and a bath temperature of 55ºC results in an adequate smoothing of the surface (Ra < 0.16 µm) for both cold rolled and SLM elements after grinding. The application of EP, to both cold rolled elements and those after SLM, considerably improves the resistance to corrosion. The results of potentiodynamic corrosion resistance tests (jkor, EKA and Vp) of the 316L stainless steel samples demonstrate that the values of Vp for elements subjected to EP (commercial material: 1.3·10-4 mm/year, SLM material: 3.5·10-4 mm/year) are lower than for samples that were only ground (commercial material: 4.0·10-4 mm/year, SLM material: 9.6·10-4 mm/year). The microhardness was found to be significantly higher in elements manufactured using SLM technology than in those cold rolled and ground. The ground 316L steel samples were characterized by a microhardness of 318 HV (cold rolled) and 411 HV (SLM material), whereas the microhardness of samples subjected to EP was 230 HV (commercial material) and 375 HV (SLM material).Originality/valueThe 316L samples were built by SLM method. The surface of the SLM samples was modified by EP. Surface morphological changes after EP were studied using optical methods. Potentiodynamic tests enabled to notice changes in the corrosion resistance of 316L. Microhardness results after electropolished 316L stainless steel were shown. The chemical composition of 316L surface samples was presented. The smoothening of the surface amounted to Ra = 0.16 µm.

Human Embryonic Stem Cell-Derived Mesenchymal Progenitor (hESCs-MP) Growth on Nanostructured Ti6Al4V Surfaces

Nanotexturing processes that focus on enhancing the bone-implant contact, such as electropolishing, have been proposed. The aim of this work was to evaluate the influence of Ti6Al4V surface morphology on human embryonic stem cell-derived mesenchymal progenitor (hESCs-MP) growth. Three surface treatments were used in this study: mechanically polished samples and two types of electropolished samples that were treated for 4 min and 12 min, respectively. The systems were characterized by atomic force microscopy, contact profilometry, X-ray diffraction, and wettability. Each system was submitted to a cell culture containing hESCs-MP cells for 14 days, and the resultant cell growth on each system was then evaluated. The results indicated that surfaces with higher nanometric and micrometric roughnesses experienced greater hESCs-MP cell growth in osteogenic media. The same behavior was not observed for cell growth in non-osteogenic media due to the absence of dexamethasone, which is responsible for controlling protein adsorption on the surface.

An Investigation of the Electropolishing of Metal Parts Fabricated By Powder Bed Fusion Additive Manufacturing

In this work the use of non-aqueous electropolishing for the surface treatment of the as-received Ti6Al4V and IN718 parts fabricated by laser and electron beam powder bed fusion additive manufacturing (PBF-AM) was investigated. Using the non-aqueous electrolyte, the characteristics of the voltage-current curve of the electropolishing exhibit a general absence of the plateau stage for both materials. Experimental design was carried out to quantify the significance of individual electropolishing parameters on the surface qualities of the samples. The electrolyte flow rate, the temperature and the electropolishing voltage appear to be the most significant input variables, and strong coupling effects among various electropolishing parameters were observed. The surface roughness of the electroplished samples exhibits significant improvement to less than 1μm, although the macroscopic surface texture was not effectively eliminated. In addition, the high-cycle fatigue performance of the electropolished samples exhibit significant improvement, which demonstrated the effectiveness of the surface treatment.

Nitrogen doping and the performance of superconducting radio-frequency niobium cavities: insights from neutron diffraction and neutron Compton scattering

Neutron Compton scattering and neutron diffraction have been applied to investigate the influence of nitrogen doping of niobium on the performance of superconducting radio-frequency niobium cavities. To this end, a comparative study of the neutronic response of two samples has been performed. An electro-polished and nitrogen-doped niobium sample was compared with a standard, a niobium sample that has only undergone the electro-polishing procedure. The first piece of information, provided by neutron diffraction, is that additional conditioning of the electro-polished cavity material, through doping with nitrogen, leads to a systematically larger niobium lattice expansion, which provides an upper conservative limit of nitrogen concentration consistent with values reported in the literature. Furthermore, neutron Compton scattering shows a broadening of the niobium momentum distribution in the nitrogen-doped sample, as compared to the standard, thus indicating an increased degree of ordering and binding of niobium in the metal lattice. On the whole, these observations suggest that nitrogendoping leads to some degree of lattice ordering, most likely due to increased hydrogen trapping, in agreement with previous results using surface spectroscopy.

Improved two-step Brytal process for electropolishing of aluminum alloys

Three aluminum alloys (5N, 1100 and 8005) were electropolished with an environmentally friendly Brytal process in order to evaluate the influence of the substrate and the operating parameters in the roughness and reflectivity of the specimens. Electropolishing was implemented in two-step, allowing lower roughness than those reported in the one-step process. Morphology and second-phase particles on electropolished samples were analyzed by SEM, roughness was measured by means of AFM and reflectivity was measured with a UV–vis spectrophotometer getting a high reflectivity for high purity aluminum and for two aluminum alloys in which reflectivity decreased due to second phase particles.

Improvement of Electropolishing of 1100 Al Alloy for Solar Thermal Applications

Aluminum sheets-based mirrors are finding applicability in high-temperature solar concentrating technologies because they are cost-effective, lightweight and have high mechanical properties. Nonetheless, the reflectance percentages obtained by electropolishing are not close to the reflectance values of the currently used evaporated films. Therefore, controlling key factors affecting electropolishing processes became essential in order to achieve highly reflective aluminum surfaces. This study investigated the effect of both the electropolishing process and previous heat treatment on the total reflectance of the AA 1100 aluminum alloy. An acid electrolyte and a modified Brytal process were evaluated. Total reflectance was measured by means of UV–Vis spectrophotometry. Reflectance values higher than 80% at 600 nm were achieved for both electrolytes. Optical microscopy and scanning electron microscopy images showed uneven dissolution for the acid electropolished samples causing a reflectance drop in the 200-450 nm region. The influence of heat treatment, previously to electropolishing, was tested at two different temperatures and various holding times. It was found that reflectance increases around 15% for the heat-treated and electropolished samples versus the non-heat-treated ones. A heat treatment at low temperature combined with a short holding time was enough to improve the sample total reflectance.

Electrochemical Reduction of Industrial Baths Used for Electropolishing of Stainless Steel

Long‐term exploitation of industrial electropolishing baths may contribute to the emergence of surface defects and may limit the range of applicable current densities. Due to this, extending the time of use of industrial baths is a major challenge. The application of electrochemical reduction in the process of reduction industrial baths enabled to reduce its contamination and, as a result, to enhance the surface quality of electropolished samples of grade 304 stainless steel. The contamination influence of the electropolishing bath on such parameters of the electropolished samples as roughness, gloss, mass reduction, and corrosion resistance was compared. The conducted tests included reduction of the contaminated industrial bath with use of cathodic reduction and monitoring of bath contamination with use of emission spectrometry ICP‐OES. Potentiodynamic tests in 0.5 M chlorine environment with the aim to determine the influence of electrochemical reduction of the plating bath on surface resistance demonstrated that the pitting corrosion resistance of samples electropolished in a bath after reduction was reduced by approximately 0.1 V in comparison with samples electropolished before reduction. The calculations conducted for 24 corrosion resistance measurements demonstrated that differences between the results were significant. Bath reduction leads to improved roughness and gloss, even by approximately 500 GU (gloss units). At the same time, mass reduction decreases even by 13% in comparison with the process conducted in the bath before reduction. This may have a positive influence by slowing down the bath contamination process and, as a result, it reduces negative environmental impact. Another argument that supports the reduction of industrial baths is slowing down the process of cathode contamination during the electropolishing process. In industrial conditions, this may extend the possibility to conduct the process without the need for cathode reduction or replacement.

Optical investigation of niobium properties: Electrical- and physical constants

In this paper, we report optical (reflectance) measurements and investigations of optical properties of electropolished (EP), buffered chemical polished (BCP), and as-received (AR) from vendor niobium (Nb) samples typically used for fabrication of superconducting radio frequency (SCRF) cavities. Optical conductivity (σ(0), approximated near zero frequency) of EP (σ(0) ∼ 9 × 103Ω−1 cm−1) sample is one order of magnitude higher than that of BCP (σ(0) ∼ 7 × 102Ω−1 cm−1) and AR (σ(0) ∼ 3 × 102Ω−1 cm−1) niobium samples. Furthermore, physical constants of electropolished Nb-SCRF materials such as concentration of conduction electrons ( ∼ 1.8 × 1022electrons/cm3), average velocity ( ∼ 5.9 × 107cm/s) of the electrons on the Fermi surface, and mean free path ( ∼ 0.53 nm) were also found to be considerably higher than that of the BCP and the AR samples. The depth of electric field penetration (in low frequency region) in the electropolished Nb sample ( ∼ 80 nm) is appreciably lesser than the BCP ( ∼ 450 nm) and the AR ( ∼ 400 nm) samples.

Surface morphology and passive film composition after pickling and electropolishing

In this work, a novel method of selecting the most favourable electropolishing (EP) conditions is presented as a compromise between the processing time and obtaining the lowest possible roughness value of Sa or Sq (commonly used parameters) as well as the gradual increase of parameters highlighted in this work Ssk and Sku. The results showed that the most appropriate EP charge input should be higher than 1.2 Amin cm−2 and lower than 2.3 Amin cm−2. XPS high-resolution spectra revealed that pickling and EP of the samples results in a decrease of the ratio of the iron oxides amount (at.-%) to the total amount of chromium oxides and hydroxides (at.-%) in the passive film. This ratio gradually decreases reaching the values 1.2, 1.0 and 0.7 for as-received, pickled and electropolished samples, respectively. This result demonstrates iron dissolution of the outer surface layer by pickling and EP.

Tribological behavior of gray cast iron textured by maskless electrochemical texturing

Gray cast iron is widely used in diesel automotive engines due to its combination of low cost and good fusibility, but also to the presence of graphite flakes in their microstructure. Besides their role as mechanical dampers, graphite flakes can act as solid lubricant, reducing friction and wear of moving components. Surface texturing has been intensively investigated in recent years to improve lubrication and reduce friction and wear in tribological applications, but little attention has been given to surface texturing of gray cast irons. On the other hand, surface texturing adds costs, which can supplant the benefits achieved, in particular when high cost surface texturing techniques are employed. Maskless electrochemical texturing (MECT) is a promising technique, which combines simplicity, low cost and high speed. Recently, MECT was adapted to texture gray cast irons. This work investigates the tribological performance of gray cast iron textured by MECT using lubricated block-on-ring tests under two different rotational speeds and a constant normal load. The blocks consisted of textured cast iron and the rings of SAE 4620 steel. For comparative purposes, untextured polished gray cast iron blocks, as well as gray cast iron blocks subjected to electrochemical polishing (employing the same electrolyte used during MECT) were tested. The results showed a large reduction in friction (up to 2.5x) and wear (higher than 5x) when comparing the polished and the textured samples. Comparing the textured samples and the electropolished samples, this improvement in performance reduced, showing that the benefits were partly due to the texture pattern itself (arrays of pockets) and partly to the exposure of the graphite flakes during electrochemical dissolution of the metal matrix. As the wear progressed and the contact between the block and the ring became more conformal, the benefits obtained by MECT (and electro polishing) were reduced.

Optimization of Electropolishing on NiTi Alloy Stents and Its Influence on Corrosion Behavior.

Nitinol or NiTi alloys are well-known as an attractive biomedical material due to their unique properties such as the shape memory effect, super-elasticity and biocompatibility. These characteristics enable them to be best candidates for implant materials such as stent. One of the major factors that strongly affect the performance of nitinol stent is its unique surface properties. In this study, the influence of electropolishing on nitinol stents and its corrosion behavior were observed. Electropolishing is an effective method for surface treatment, which not only controls the surface state but also helps to produce uniform surface layers. Therefore, to improve the surface quality of nitinol stents, we conducted an electropolishing under various conditions from 30–40 V and 10–30 s as a post heat treatment for nitinol stent manufacturing process. In order to find the optimal surface state of NiTi stents, various electropolished samples were explored using various characterization techniques. Furthermore, the potentiodynamic polarization tests were also performed to determine the corrosion resistance. The electropolished nitinol stents under the condition of 40 V for 10 s exhibited the best corrosion performance as well as surface quality.

Application of Radio Frequency Glow Discharge Sputtering for Nanoindentation Sample Preparation

The applicability of radio frequency glow discharge (rf-GD) sputtering to the surface finishing of nanoindentation specimens was examined for pure Al, Cu, and Ni. Comparisons were made between specimens that had been subjected to the following surface finishing: (1) rf-GD sputtering, (2) electropolishing, and (3) mechanical polishing with 0.25 µm of diamond suspension. It was suggested from the nanoindentation behavior and the quality of electron backscattered diffraction patterns that residual damage on the surface of the rf-GD sputtered samples was as small as that of electropolished samples, while some damages remained on the surface of the mechanically polished samples. The areal roughness within a 1-μm square of the rf-GD sputtered surface was comparable to that of the mechanically polished surface and slightly larger than that of the electropolished surface. Nonetheless, the difference of the roughness within the range of this study has no practical impact upon nanohardness and elastic modulus evaluation. Pop-in events occurred in the electropolished and rf-GD sputtered specimens, but not in the mechanically polished samples. The critical load for pop-in to occur was slightly smaller in rf-GD sputtered sample than in electropolished samples.

Quantitative in-situ TEM nanotensile testing of single crystal Ni facilitated by a new sample preparation approach

Twin-jet electro-polishing and Focused Ion Beam (FIB) were combined to produce small size Nickel single crystal specimens for quantitative in-situ nanotensile experiments in the transmission electron microscope. The combination of these techniques allows producing samples with nearly defect-free zones in the centre in contrast to conventional FIB-prepared samples. Since TEM investigations can be performed on the electro-polished samples prior to in-situ TEM straining, specimens with desired crystallographic orientation and initial microstructure can be prepared. The present results reveal a dislocation nucleation-controlled plasticity, in which small loops induced by FIB near the edges of the samples play a central role.

Influence of Surface Nanoporus Structure on the Corrosion Fatigue of Type 316L Stainless Steel in Sodium Chloride Solution

Corrosion fatigue is one of the severe corrosion problems that leads to materials failure. Therefore numerous works have been dedicated in order to improve fatigue life. For example, it was reported that the surface treatment such as shot-peening improved fatigue life of a low-alloy steel. This result indicates that the surface properties and morphology may affect the corrosion fatigue behavior. Recently nanopore arrays have been reported to be fabricated on stainless steels in perchloric acid containing organic solvents. The dimension of nanopore is controlled by applied voltage.[1-3] In the present work, we investigated the impact of surface morphology on corrosion fatigue behavior of type 316L stainless steel in a 0.9% NaCl solution. 3 types of samples with different morphologies were prepared; mirror-finished, electropolished and nanoporus samples. In the sodium chloride solution, the fatigue test was performed to evaluate the effect of the surface morphology on fatigue life. Furthermore, fractured samples were observed by a scanning electron microscopy(SEM). Results indicate that the surface morphology clearly affects on the fatigue life, that is, the presence of nanopore arrays improved fatigue life in the sodium chloride solution. Details on influence of the surface nanoporus structure on the corrosion fatigue behavior will be discussed in the presentation. [1]V.Vignal, J.C.Roux, S.Flandrois, A.Fevrier, Corrosion Science.42(2000)1041 [2]F.Martin, D.Del Frari, J.Cousty, C.Bataillon, Electrochimica Acta 54(2009)3086 [3]H.Tsuchiya, T.Suzumura, Y.Terada, S.Fujimoto, Electrochimica Acta 82(2012)333

Role of different plasma gases on the surface chemistry and wettability of RF plasma treated stainless steel

Vacuum radio frequency (RF) plasma treatment was conducted on electropolished and passivated 316 LVM stainless steel (SS) surface by using Ar and O2. Contact angle measurements revealed that both Ar and O2 plasma treatments significantly increased the wettability of the SS surface by water. The physical and chemical effects induced by Ar and O2 plasma on SS were investigated via Atomic Force Microscopy (AFM) and X-ray Photoelectron Spectroscopy (XPS). AFM analysis revealed that plasma process exerted similar effects on surface roughness and topography. Both Ar and O2 plasma treatments resulted in smoother surface when compared to reference electropolished sample. XPS investigations of the surfaces with respect to Fe2p, Cr2p, Mo3d and O1s XPS spectra showed that the main role of Ar plasma was thinning of the oxide-hydroxide layer along with the removal of contamination without any definitive difference on the valence states of metal compounds. On the other hand, O2 plasma treatment resulted in thickening of oxide layer along with oxidation of the species to their highest valence states (CrVI, FeIII and MoVI). After washing the plasma treated surfaces with water, contact angles for oxygen plasma treated samples increased dramatically indicating the substantial role of higher valent oxides on wetting process.

On the electropolishing and anodic oxidation of Ti-15Mo alloy

This paper presents research on modifying the surface of Ti-15Mo alloy using electropolishing and anodic passivation. The electropolishing process was carried out in solutions containing sulfuric acid, ethylene glycol, ammonium fluoride and oxalic acid. Whereas a voltage range from 20 to 100V and a 1M orthophosphoric acid solution were used during the anodic passivation. The influence of above mentioned processes parameters on the quality of the obtained oxide layer on Ti-15Mo alloy was investigated. The analysis of Ti-15Mo surface after modification was performed using scanning electron microscopy (SEM), atomic force microscopy (AFM), energy-dispersive X-ray spectroscopy (EDX), X-ray photoelectron spectroscopy (XPS), ellipsometry, and mechanical tests. Moreover, the corrosion resistance was investigated using a potentiostatic method in Ringer’s solution. It was found that electropolishing leads to an increase in the surface homogeneity and to the form of an oxide layer, which consisted of TiO2 and MoO3. Whereas the oxide layers obtained during anodic passivation were characterized by different properties depending on the applied voltage. The anodic passivation at various voltages (20–100V) increased the surface wettability (94.5°–87.6°) in comparison to the electropolished sample (97.5°). Moreover, the obtained oxide layer after anodization exhibited a high hardness. The electrolytic polishing and anodic passivation of Ti-15Mo also improved corrosion resistance of the alloy in contact with Ringer's solution. The sample anodized at 80V presented the highest corrosion resistance by the smallest corrosion current density (1.4 nAcm−2) and the highest polarization resistance (37.4MΩcm2).

Surface modification of L605 by oxygen plasma immersion ion implantation

Event Abstract Back to Event Surface modification of L605 by oxygen plasma immersion ion implantation Carlo Paternoster1, Letícia Marin De Andrade1, Vanessa Montaño-Machado1, Ranna Tolouei1, Stéphane Turgeon1 and Diego Mantovani1 1 Laval University, Lab. for Biomaterials & Bioengineering (CRC-I), Dept. Min-Met-Materials Engineering & CHU de Quebec, Canada Introduction: Co-Cr alloys are currently used in biomedical applications for artificial heart valves, dental prosthesis, vascular stents and orthopedic fixation plates[1],[2]. L605, a Co-Cr alloy shows excellent mechanical properties, suitable for cardiovascular applications, but the presence of high amounts of Ni, Cr and Co is a health concern. A surface treatment creating a stable surface layer can effectively hinder the release of toxic ions and accommodate substrate deformation. For this reason, an electropolished L605 substrate was modified by oxygen plasma immersion ion implantation (PIII), to improve biocompatibility and increase the corrosion resistance, modifying the chemical composition[3],[4]. The effects of implanted oxygen dose (d) and antenna power (P) were investigated; the characterization of the surface condition was performed by different techniques and the interaction of endothelial cells with the modified surfaces was assessed. Materials and Methods: L605 flat samples were electropolished and subsequently oxygen implanted with a pulse duration and frequency respectively in the range of 50-100 µs and 10-40 Hz. Effect of antenna power and implanted doses have been investigated, in terms of surface and proliferation of human endothelial cells. X-Ray photoelectric spectroscopy (XPS) and scanning electron microscopy (SEM) were used to assess surface chemistry and morphology. Roughness and surface energy were studied by atomic force microscopy (AFM) and contact angle measurements. Finally, corrosion resistance was investigated by potentiodynamic test in 0,152 M saline solution. Endothelial cell viability was investigated after 1, 3 and 7 days of culture through resazurin tests. Results and Discussions: After oxygen implantation, the oxidized layer chemical composition is different from the one of the electropolished sample, and it is mainly composed by O and Co (figure 1). The oxygen amount increases for increasing doses (in the range of 17.5 % at. to 54% at.). For increasing antenna power, the oxygen surface amount does not vary in considerable way. XPS analysis attributed O1s peak to the formation of metallic oxides and complex phases including Si. Roughness decreased gradually both with increasing implantation time and with increasing antenna power (figure 2). The implantation process does not affect in a considerable way the surface morphology, as evidenced by SEM micrographs. The potentiodynamic polarization show an increase of Ecorr potential in oxygen implanted samples. Endothelial cell investigations in L605 treated samples show the highest cell viability on A3 condition (d = 400%, P = 300 W) and the lowest on B1 one (d = 400%, P = 150 W). Conclusions: Oxygen PIII can effectively change the chemical composition and surface energy of the substrate alloy. Increasing both implantation doses and antenna power increase the amount of Co oxide on the surface, improving the corrosion resistance and biological response. This work was partially funded by NSERC-Canada, FRQ-NT-Quebec and CFI-Canada. VMM was awarded of a doctoral scholarship from Conacyt – National Council of Science and Technology, Mexico. LMA was awarded of an undergraduate scholarship from CNPq - CAPES Foundation and Ministry of Education of Brazil. CP and DM were recipiendaries of the Linkage Grant from Quebec/Italy sub-commission of the Quebec Ministry of Intl Relations.

Surface modification and bare metal functionalization of cobalt chromium alloys for biomolecule grafting

Event Abstract Back to Event Surface modification and bare metal functionalization of cobalt chromium alloys for biomolecule grafting Sergio Diaz-Rodriguez1, Carlo Paternoster1, Pascale Chevallier1 and Diego Mantovani1 1 CHU de Québec Research Center, Laval University, Lab. Biomaterials and Bioengineering, CRC-I, Dept Min-Met-Materials Eng, Canada Introduction: L605 Co-Cr alloy is often used in cardiovascular applications due to its mechanical properties and resistance to corrosion [1],[2]. The biocompatibility of these devices and the reduction of adverse events (for example restenosis) associated to endovascular procedures are issues that still need to be assessed with a thorough approach. An effective one is the use of a multistep process aimed at: (1) modifying the metallic surface, to hinder the release of toxic ions (Cr, Ni) and to enhance the performance of the following modification process; (2) functionalizing the material by plasma amination directly on the metal, and (3) grafting suitable bioactive molecules for cardiovascular applications. Nevertheless, the mechanical properties of the layer formed during the first stage have to match those of the deforming substrate during device deployment. The object of this work is a preliminary study of the properties of an oxide layer produced on L605, with special emphasis to its effect on the following stages of the above mentioned strategy. Materials and Methods: L605 round samples of 15mm diameter, previously cleaned in an ultrasonic bath, were electropolished (EP) before thermal treatment (TT) in an air furnace. The effects of three temperatures (400, 500 and 600°C) and two duration times (1 or 2 hours) on the amination step effectiveness and on the coating mechanical properties [3] were investigated. The alloy amination was performed in a N2/H2 microwave plasma at 300 W during 10 min at 100 mTorr with a 5/5 sccm flow. Amination efficiency was assessed by chemical derivatization with chlorobenzaldehyde [4]. X-ray photoelectron spectroscopy (XPS), optical and scanning electron microscopy, and contact angle (CA) were used for surface characterization, before and after amination. Results and discussion: Chromium oxide is the surface main constituent of EP samples, while cobalt oxide (Fig. 1a) is the main one for TT specimens. Both temperature and exposition time induced changes in the oxide layer composition, as evidenced by XPS analyses. The surface functionalization was correlated to the initial oxide layer composition, as shown in fig. 1b: the selectivity, depict by %NH2/%N ratios, was enhanced by higher Co/Cr % at. ratios. Increasing TT temperatures and times promote surface features compatible with the formation of bigger oxide crystals. Deformed samples showed delamination and cracks for higher temperature treatments (Fig. 2). CA analyses displayed no significant difference all having a hydrophobic character (90 to 110°). Conclusion: Bare metal samples were successfully functionalized with amine groups using plasma treatment, as evidenced by chemical derivatization. Furthermore, TT increased the effectiveness of surface functionalization, obtaining more amino groups on the surface and also a better selectivity. However, high temperature samples evidenced a poor adhered and cracked oxide layer after deformation. Though, the TT at 400°C appeared promising due to its stability to deformation and its good amination yield. This work was partially supported by NSERC-Canada, CIHR-Canada, CFI-Canada, FRQ-NT-Quebec, and MRI-Quebec. SD-R was awarded of a doctoral scholarship from the NSERC CREATE program for regenerative medicine (NCPRM).

TEM and SEM analyses of the orientation relations of recrystallized grains in a stable Al–1 wt.%Mn single crystal

The recrystallization grain orientations developed during annealing of a deformed single crystal have been characterized by in-situ TEM and ex-situ SEM. Single crystal samples of Al–1wt.%Mn alloy of brass(110) [1-1-2] orientation were deformed in a channel-die to develop 2 sets of intersecting microbands at strains of 0.51 and 0.92 and then lightly annealed. Local orientation measurements demonstrate a strong relation between the deformed orientations and the limited number of recrystallized grain orientation groups. The misorientation angles across the recrystallization front were grouped in the range 25–55° (with a maximum near 40–45°) around axes located near three normals of the 4 {111} planes; the [1-11] rotation axis parallel to the transverse direction was not found. Two groups of rotation axes were identified: (i) rotation axes very close to the <111> or <112> directions, and (ii) a scattered sequence between <111>–<112>, <111>–<122> or <122>–<012> directions. The orientations of new grains that nucleate during thin foil heating in TEM were compared with those formed during static recrystallization of bulk samples analysed by SEM/EBSD, both in the centre section of electropolished samples and in near-surface areas of abraded samples. In all experiments the new grain orientations belong to the same groups and the distribution of misorientation axes across the recrystallization front was similar.

Morphology of Co-Cr-Mo dental alloy surfaces polished by three different mechanical procedures

The present study aims at characterizing the three-dimensional (3-D) morphology of a Co-Cr-Mo dental alloy surface as a result of three different procedures used for polishing it. The sample surface morphology of the sampled surface was examined employing atomic force microscopy (AFM), statistical surface roughness parameters, and fractal analysis. An extra-hard dental alloy of cobalt-chromium-molybdenum (Co-Cr-Mo) (Wironit(®) , from BEGO, Bremen, Germany) was prepared and moulded. Different polishing treatments were carried out on three groups of six samples each--a total of 18 samples. The first group contained six electropolished (EP) samples. The second group containing six samples went through a mechanical polishing process employing green rubber discs and a high shine polishing paste applied by a rotating black brush (BB). The third group comprising six samples as well went through a mechanical polishing process by means of green rubber discs, high shine polishing paste, and a rotating deer leather brush (DL). Fractal analysis on the basis of a computational algorithm applied to the AFM data was employed for the 3-D quantitative characterization of the morphology of the sampled surfaces. The fractal dimension D (average ± standard deviation) of 3-D surfaces for BB samples (2.19 ± 0.07) is lower than that of the DL samples (2.24 ± 0.08), which is still lower than that of the EP samples (2.27 ± 0.09). The results indicated the BB samples as presenting the lowest values of statistical surface roughness parameters, thus the best surface finish, while the EP samples yielded the highest values.