Papers by Keyword: Electrophoretic Deposition

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Authors: C. Ramskogler, L. Cordero, Fernando Warchomicka, A.R. Boccaccini, Christof Sommitsch
Abstract: An area of major interest in biomedical engineering is currently the development of improved materials for medical implants. Research efforts are being focused on the investigation of surface modification methods for metallic prostheses due to the fundamental bioinert character of these materials and the possible ion release from their surfaces, which could potentially induce the interfacial loosening of devices after implantation. Electron beam (EB) structuring is a novel technique to control the surface topography in metals. Electrophoretic deposition (EPD) offers the feasibility to deposit at room temperature a variety of materials on conductive substrates from colloidal suspensions under electric fields. In this work single layers of chitosan composite coatings containing titania nanoparticles (n-TiO2) were deposit by EPD on electron beam (EB) structured Ti6Al4V titanium alloy. Surface structures were designed following different criteria in order to develop specific topography on the Ti6Al4V substrate. n-TiO2 particles were used as a model particle in order to demonstrate the versatility of the proposed technique for achieving homogenous chitosan based coatings on structured surfaces. A linear relation between EPD time and deposition yield on different patterned Ti6Al4V surfaces was determined under constant voltage conditions, obtaining homogeneous EPD coatings which replicate the 3D structure (pattern) of the substrate surface. The present results show that a combination of both techniques can be considered a promising surface modification approach for metallic implants, which should lead to improved interaction between the implant surface and the biological environment for orthopaedic applications.
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Authors: Yadir Torres, Carlos Romero, Qiang Chen, Gonzalo Pérez, José Antonio Rodríguez-Ortiz, Juan José Pavón, Laura Álvarez, Cristina Arévalo, Aldo Boccaccini
Abstract: Commercially pure titanium (cp Ti) is typically accepted as one of the best in vitro and in vivo bone replacement biomaterial, due to its excellent balance between biomechanical and biofunctional properties. In that context, the aim of this work is to prove the hypothesis of a simultaneous solution to certain specific limitations of cpTi, which can often compromise the reliability of implants: (i) stress-shielding phenomenon, and (ii) a deficient biointerface with bone, which reduces the osseointegration. Porous samples of cp Ti, grade IV, were obtained by space-holder technique (50 vol.% NH4HCO3, 800 MPa, at 1250 oC during 2h, under high vacuum), to produce a good balance between Young ́s Modulus and yield strength. Different types of porous samples were manufactured by considering different size particles ranges of NH4HCO3: 100-200μm, 250-355μm and 355-500μm. Afterwards, they were coated with a PEEK/45S5 bioactive glass composite by electrophoretic deposition, to be finally sintered at 350oC for 1h. The coatings homogeneity, infiltration efficiency, adhesion and cracking, were studied in order to establish correlations with processing conditions (time of deposition, applied voltage, composition, concentration and stability of the colloidal suspension). Detailed structural characterization of the coatings was performed (SEM and XRD), besides the contact angle and contact profilometry testing. Additional mechanical and chemical insights were achieved by evaluating both the tribo-mechanical (instrumented microindentation and micro-scratch testing) and electrochemical behaviors (potentiodynamic polarization and in vitro corrosion tests in SBF). All these results allowed us to determine the optimal balance of properties for a porous substrate (space holder of 250-355μm) with a coating obtained for 65 V, 2 min, 6 mm (distance between electrodes), 10 g/L bioactive glass and 20 g/l PEEK. The high adhesion estimated between the bioactive/biopolymer coatings and the porous titanium substrates (excellent infiltration) suggest that this new biocomposite is a good candidate for load-bearing applications.
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Authors: Inga Narkevica, Laura Stradina, Liga Stipniece, Jurijs Ozolins
Abstract: TiO2 nanoparticles were electrophoretically deposited on the dense TiO2-x ceramic electrodes from suspension containing TiO2 nanoparticles, isopropanol as a solvent and triethanolamine as dispersant. The effect of deposition parameters including deposition voltage (10 to 60 V) and deposition time (10 to 40 min) on the microstructure and deposition yield was examined. It was found that the thickness of coating increased with increasing deposition time and deposition voltage. However, it affected the quality of obtained coating e.g. cracks and holes were observed. Optimizing deposition parameters homogeneous coating with smooth microstructure and limited surface damage can be obtained. Thermal treatment of the coating in the temperature range from 700 to 1100 °C causes anatase to rutile phase transformation. Crack formation was noted during sintering due to the phase transformation and thermal stresses.
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Authors: Zaeem Ur Rehman, Mohsin Ali Raza, Faizan Ali Ghauri, Rumasa Kanwal, Akhlaq Ahmad, Aqil Inam
Abstract: In this study graphene coatings were deposited on mild steel substrate using feasible and environmental friendly method. The successful synthesis of graphite oxide was carried by the modified Hummer’s method. Graphene oxide (GO) coatings were developed from GO/water suspension using electrophoretic deposition (EPD). The EPD parameters voltage and deposition time were varied to deposit uniform adherent coatings. The coatings were post heat treated at 200 °C in vacuum for 4h to assess the effect on coated samples. GO and GO-EPD coating morphology were characterized using Fourier transform infrared spectroscopy (FTIR), Atomic force microscopy (AFM) and Scanning electron microscopy (SEM). Linear polarization (LPR) and electrochemical impedance spectroscopy (EIS) tests were performed in saline solution to evaluate electrochemical response. Coatings were partially reduced due to removal of oxygen containing functional groups during EPD and post heat treatments. The GO post heat treated coating had better corrosion resistance ~2 times than that of bare mild steel and higher charge transfer resistance.
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Authors: Alexis Karla Garcia, Rinlee Butch M. Cervera
Abstract: YSZ film was fabricated by a facile electrophoretic deposition process using commercial YSZ powders. YSZ films with average thickness of around 10 µm were deposited on LSM/YSZ substrate at 20 V for 20 minutes and subsequently sintered at 1200 °C, 1300 °C, and 1350°C. XRD patterns of the deposited and sintered films can be attributed to mostly cubic YSZ phase. On the other hand, SEM images revealed that a sintering temperature above 1300 °C was needed to obtain a denser YSZ film. The film morphology also showed that as the sintering temperature increases, the YSZ grain size also increases.
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Authors: Feng Hua Li, Han Gao, Bo Wen Zhang, Qing Lian Zhu
Abstract: MgB2 powder was fabricated by sintering the mixture of pure Mg and B powder with atomic ratio of Mg : B=1:2. The magnetic property of the powder indicated that it was superconducting and its critical transition temperature was 39K. Titanium based MgB2 films were obtained by electrophoretic deposition method using Ni sheet as anode and titanium tapes as cathode. The films were annealed at 500°C for 2 hours, subjected to argon-hydrogen (95%Ar+5%H2) gas flow. The results of X-ray diffraction (XRD) analysis showed that the composition of the film was mainly MgB2. The observation under scanning electron microscopy (SEM) showed that the film of MgB2 was uniform and dense. The electrical resistivity of double-side MgB2 film was about 5.280×10-8Ω/m.
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Authors: Malinee Meepho, Nutthita Chuankrerkkul, Sirima Chauoon, Rojana Pornprasertsuk
Abstract: Thin film electrolyte made of 8-mol% yttria stabilized zirconia (8YSZ) was fabricated on porous NiO-8YSZ anode substrates using electrophoretic deposition (EPD). The porous NiO-8YSZ anode substrates were prepared by powder injection molding technique. The electrolyte suspensions containing 8YSZ nanoparticles and polyethylene glycol (PEG) as a dispersant (1-19 wt%) were formed in ethanol. The maximum zeta potential value was obtained from the 8YSZ suspension with 5 wt% PEG considered as an optimal content of PEG dispersant. The electrophoretic deposition of 8YSZ film was performed on the porous anode substrate using a constant voltage of 30 V for 150 sec prior to co-sintering at different temperatures in order to obtain dense 8YSZ electrolyte film on the porous anode substrate. Co-sintering at 1250°C for 1 h resulted in a formation of a dense 8YSZ thin-film electrolyte with a thickness of 6.35 mm. An open circuit voltage at 800°C of a single cell having 8YSZ thin-film electrolyte on porous NiO-8YSZ anode substrate was 1.09 V, indicating a gas-tightness of 8YSZ thin-film electrolyte fabricated by using EPD.
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