EPD Method Research Articles

Deposition of Ultrathin Cellulose Nanofibers Films As Bio-Implant Corrosion Coatings

The wide use of magnesium and magnesium-based alloys for bio-implant materials has so far been restricted due to the rapid corrosion rate of such materials under in-vivo conditions 1,2. Cellulose based coatings have previously been examined as coatings for magnesium materials although the use of TEMPO-oxidised nano-fibrillated cellulose (CNF-TEMPO) coatings has yet to be explored 3,4. The work outlines details of an investigation in to the effect that deposition method has on the coating characteristics. Three different methods were used to deposit CNF-TEMPO coatings including adsorption, spin coating and anodic electrophoretic deposition. The coatings were subsequent analysed using atomic force microscopy (AFM), ellipsometry and quartz crystal microbalance (QCM) to determine differences in nanotopographic surface roughness and hydrophilicity in particular. The ability of the EPD technique to deposit films from relative dilute solutions (0.01 to 0.1 wt-%) was demonstrated. Finally, samples of magnesium were coated and the corrosion properties of the ultrathin films were determined using a number of electrochemical techniques including linear sweep voltammetry, polarization and free corrosion measurements. Overall, the results show that CNF-TEMPO coatings produced using the EPD method offer a potential starting point for the next generation of biobased coatings for implant materials.

Effect of the Nafion content in the MPL on the catalytic activity of the Pt/C-Nafion electrode prepared by pulsed electrophoresis deposition

The aim of this work is to study the effect of Nafion content in the microporous layer (MPL) on the electrophoretically deposited Pt/C-Nafion electrode performance. First, the MPLs are prepared with different Nafion ionomer contents (5, 10, 20, 30 and 40 wt%) on the carbon paper substrates. Next, Pt/C-Nafion electrodes are prepared by pulsed electrophoresis deposition (pulsed EPD) from a Pt colloidal solution as a plating bath. The catalytic activities of the prepared Pt/C-Nafion electrodes are evaluated using the cyclic voltammetry (CV) technique for hydrogen oxidation reaction (HOR). Also, a PEMFC single cell test is carried out using the Pt/C-Nafion electrodes prepared with the pulsed EPD method as a cathode. The mass-specific power density for the Pt/C-30wt% Nafion electrode is 1578.8mWmgPt−1, which is higher than the rest of the Pt/C-Nafion electrodes. The Nafion content in the cathode MPL should affect the performance of the PEMFC, especially at a high current density.

Electrochemical behavior of 45S5 bioactive ceramic coating on Ti6Al4V alloy for dental applications

Titanium and its alloys are widely used as implant materials because of their mechanical properties and non-toxic behavior. Unfortunately, they are not bioinert, which means that they can release ions and can only fix the bone by mechanical anchorage, this can lead to the encapsulation of dense fibrous tissue in the body. The bone fixation is required in clinical conditions treated by orthopedic and dental medicine. The proposal is to coat metallic implants with bioactive materials to establish good interfacial bonds between the metal substrate and bone by increasing bioactivity. Bioactive glasses, ceramics specifically 45 S5 Bioglass, have drawn attention as a serious functional biomaterial because osseointegration capacity. The EPD method of bioglass gel precursor was proposed in the present work as a new method to obtain 45S5/Ti6A14V for dental applications. The coatings, were thermally treated at 700 and 800°C and presented the 45 S5 bioglass characteristic phases showing morphology and uniformity with no defects, quantification percentages by EDS of Si, Ca, Na, P and O elements in the coating scratched powders, showed a good proportional relationship demonstrating the obtention of the 45S5 bioglass. The corrosion tests were carried out in Hank's solution. By Tafel extrapolation, Ti6Al4V alloy showed good corrosion resistance in Hank's solution media, by the formation of a passivation layer on the metal surface, however, in the system 45S5/Ti6Al4V there was an increase in the corrosion resistance; icon-, Ecorr and corrosion rate decreased, the mass loss and the rate of release of ions, were lower in this system than in the titanium alloy without coating.

Interfacial control of uni-directional SiCf/SiC composites based on electrophoretic deposition and their mechanical properties

Abstract Interfacial control of uni-directional SiC f /SiC composites were performed by EPD, and their mechanical properties at room temperature were evaluated. The effect of the thickness of carbon interphase on SiC fibers by EPD on mechanical properties of uni-directional SiC f /SiC composites was also investigated. The average thickness of carbon coating on SiC fibers increased from 42 nm to 164 nm with an increase in the concentration of colloidal graphite suspension for EPD. Dense SiC f /SiC composites were achieved and their fiber volume fraction was 47–51%. The SiC f /SiC composites had a bending strength of 210–240 MPa. As the thickness of carbon coating was below 100 nm, the SiC f /SiC composites (SC01 and SC02) fractured in almost brittle manner. In contrast, the SiC f /SiC composites (SC03) showed a pseudo-ductile fracture behavior with a large number of fiber pullout as the thickness of carbon coating was above 100 nm. The fracture energy of SC03 was 3–4 times as high as those of SC01 and SC02 and the value was about 1.7 kJ/m 2 . In consideration of the results of mechanical properties, the thickness of carbon coating on SiC fibers should be at least 100 nm to obtain high-performance SiC f /SiC composites. The fabrication process based on EPD method is expected to be an effective way to control the interfaces of SiC f /SiC composites and to obtain high-performance SiC f /SiC composites.

Preparation of Perovskite-Type Oxide Thick-Film Device by EPD Method and its Application for Electrochemical Hydrogen-Phosphate Ion Sensor

Perovskite-type oxide (LaCoO3) fine powders were prepared by a polymer precursors (PP) methods at 300~500°C. The LaCoO3fine powder could be prepared at 380°C when the use of EDA and PEG for organic-and polymer-additives, respectively. The surface area of LCO was ca. 39m2/g. LCO thick-film could be prepared from the steady state suspension with the addition of AcAc or PVAby the EPD method at +10V, 3min.The current density of the LaCoO3film sensor was changed with changing HPO42-concentration at +1.00 V vs. SCE. The device showed relatively good amperometoric response to H2PO4-from 1.0x10-5M to 1.0x10-3M with the 90% response time of ca 2min. The LaCoO3-based sensor also showed a good selectivity among the examined anions of NO3-, Cl-and SCN-.

微粉末スラリーを用いた直流・パルス泳動電着法によるBaxSr1-xTiO3誘電膜の作製と評価

微粉末スラリーを用いた直流・パルス泳動電着法によるBaxSr1-xTiO3誘電膜の作製と評価

Effects of calcination temperature on microstructures and photocatalytic activity oftitanate nanotube films prepared by an EPD method

Titanate nanotube films are fabricated on F-dopedSnO2-coated glass substrates via an electrophoretic deposition method using hydrothermallyprepared titanate nanotubes as precursors. The effects of calcination temperature on themicrostructures and photoactivity of as-prepared titanate nanotube films areinvestigated and discussed. The results indicate that the intercalated sodium ions(Na+) in the as-prepared titanate nanotubes are easily removed during the electrophoreticdeposition. The phase transformation of titanate to anatase and diffusion ofNa+ ions from glass substrates into films occur at400 °C. With increasing calcination temperature, the crystallization ofanatase enhances and sodium content in the films increases. At500 °C, the tubular structure still holds and the films show the highest photocatalytic activityprobably due to their good crystallization, large specific surface areas and tubularstructures.

Functionalized Single‐Walled Carbon Nanotubes Modified Microsensors for the Selective Response of Epinephrine in Presence of Ascorbic Acid

AbstractModified stainless steel microelectrodes (microwire diameter: 300 μm) were assembled using functionalized single‐walled carbon nanotubes (SWCNTs) deposited by the EPD method (electrophoretical deposition process). The functionalized SWCNTs, which covered the microelectrode surfaces, showed an improved sensitivity and selectivity toward the electrochemical detection of epinephrine. These chemical sensors hampered the voltammetric responses of ascorbic acid (AA) and uric acid (UA), while the electrochemical oxidation of epinephrine was significantly enhanced. Using the differential pulse voltammetry (DPV) technique, epinephrine showed a very well resolved peak centered around 240 mV, while 1 mM of AA (present in the same solution) was not detected. The corresponding permeability and permselectivity parameters were also evaluated for ascorbic acid and uric acid. To investigate the sensor selectivity, a comparative study performed using microsensors assembled with non functionalized carbon nanotubes, deposited on the microelectrode surfaces by a chemical vapor deposition (CVD) technique, was also carried out. This study was useful to highlight that the presence, or the absence of electrostatic barriers on SWCNT's walls (due to the presence of some chemical functional groups), can be able to control the electrochemical response of these sensors. This optimization resulted in microsensors with a good linear range (2–100 μM) epinephrine; a good sensitivity (28.1 A M−1 cm−2) and interelectrodes reproducibility (RSD%=7.0, n=6), a detection of limit (LOD=3σ) of 2 μM; a response time of 6 s; a significant operational stability (of 13 hours in continuous working conditions) and long term stability (1 month).

Preparation of compaction of calcium carbonate by EPD method and hydrothermal treatment

Preparation of compaction of calcium carbonate by EPD method and hydrothermal treatment