Versatile Strategy for Electrophoretic Deposition of Polyvinylidene Fluoride-Metal Oxide Nanocomposites

Polyvinylidene fluoride (PVDF) is an advanced functional polymer which exhibits excellent chemical and thermal stability, and good mechanical, piezoelectric and ferroelectic properties. This work opens a new strategy for the fabrication of nanocomposites, combining the functional properties of PVDF and advanced inorganic nanomaterials. Electrophoretic deposition (EPD) has been developed for the fabrication of films containing PVDF and nanoparticles of TiO2, MnO2 and NiFe2O4. An important finding was the feasibility of EPD of electrically neutral PVDF and inorganic nanoparticles using caffeic acid (CA) and catechol violet (CV) as co-dispersants. The experiments revealed strong adsorption of CA and CV on PVDF and inorganic nanoparticles, which involved different mechanisms and facilitated particle dispersion, charging and deposition. The analysis of the deposition yield data, chemical structure of the dispersants and the microstructure and composition of the films provided an insight into the adsorption and dispersion mechanisms and the influence of deposition conditions on the deposition rate, film microstructure and composition. PVDF films provided the corrosion protection of stainless steel. Overcoming the limitations of other techniques, this investigation demonstrates a conceptually new approach for the fabrication of PVDF-NiFe2O4 films, which showed superparamagnetic properties. The approach developed in this investigation offers versatile strategies for the EPD of advanced organic-inorganic nanocomposites.

Carbenoxolone as a Multifunctional Vehicle for Electrodeposition of Materials

This investigation describes for the first time the application of carbenoxolone for electrophoretic deposition (EPD) of different carbon materials, polytetrafluoroethylene (PTFE) and their composite films. Carbenoxolone is a versatile biosurfactant, which adsorbs on materials due to its amphiphilic structure and allows their charging and dispersion. Moreover, carbenoxolone exhibits film-forming properties, which are investigated in experiments on EPD of films using water and ethanol-water solvents. The new deposition process is monitored in situ and the deposition yield and film microstructure are analyzed at different conditions. The EPD mechanism of materials involves electrode reactions of the carbenoxolone surfactant. The data of potentiodynamic studies coupled with the results of impedance spectroscopy show that PTFE films can be applied to protect metals from corrosion. Electron microscopy, electrochemical techniques and modeling are used for analysis of the microstructure and porosity of films prepared at different conditions. Carbenoxolone is applied as a co-surfactant for the EPD of composites.

Optimization of Direct Laser Deposition of a Martensitic Steel Powder (Metco 42C) on 42CrMo4 Steel

In this study, the deposition of martensitic stainless-steel (Metco 42C) powder on 42CrMo4 structural steel by direct laser deposition (DLD) was investigated. Clads were produced by varying the laser power, scanning speed, feed rate, and preheating. The effect of these processing variables on the microstructure and microhardness of the clads was analyzed, as well as their soundness, yield (measured by dilution), and geometric characteristics (height, width, and depth). The complex interaction of the evaluated processing variables forced the application of complex parameters to systematize their effect on the clads. A genetic optimization algorithm was performed to determine the processing conditions warranting high-quality clads, that is, sound clads, metallurgically bonded to the substrate with required deposition yield.

Researches on the Welding Behaviour of Two Brands of High-Alloy and High-Efficiency Electrodes Used to Charge High Wear Parts

The research performed and presented in this paper, aims to verify the welding behavior of electrodes developed experimentally, as well as the possibility of their use in production. A group of two electrodes produced by Bohler Company, Gridur 24 and B.M.N were taken as reference, in order to compare them in terms of the mechanical properties of the deposited metal, with the experimentally developed electrodes EICr12Fe and EIMn13SiFe. They were made determinations of the chemical composition of the deposited metal with the two types of electrodes, measurements regarding the hardness of the metal deposited, comparative determinations of the structure of the weld deposit, and of the welding penetration, determinations of the deposition yield and verification of the welding behavior.

Electrophoretic Deposition of TiO2 Nanoparticles on Dense TiO2-x Ceramic Electrodes

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.

Study of the Electrophoretic Deposition of Chitosan/Halloysite Nanotubes/Titanium Dioxide Composite Coatings Using Taguchi Experimental Design Approach

This study presents experimental results on the electrophoretic deposition (EPD) of chitosan/halloysite nanotube/titanium dioxide composite coatings based on the Taguchi design of experiments (DOE) approach. Taguchi array of L18type with mixed levels of the control factor was used to study the influence of EPD parameters, including halloysite nanotubes concentration, electric voltage and deposition time, on deposition yield. For identifying the significant factors that affected the deposition yield, multivariate analysis of variance (MANOVA) and regression analysis based on partial least-square method were used. The coatings were investigated by scanning electron microscopy (SEM), X-ray diffraction (XRD) and Fourier transform infrared (FTIR) spectroscopy analyses, respectively. It was found that the deposition time has significantly influenced the deposition rate but the halloysite nanotube concentration and the applied voltage have the smallest effect on the deposition. The optimum condition for high yield of deposition with low standard deviation is achieved when the concentration of halloysite nanotubes is 0.3 g/L and the applied voltage is 40 volt with 300 sec. as a deposition time. The predicted EPD conditions were verified by experiments and qualitative agreement was obtained.

Fundamentals of Pulsed and Direct Current Electrophoretic Infiltration Kinetics

The present research endeavors to demonstrate the applicability of electrophoretic deposition (EPD) for the infiltration and coating of porous materials to create advanced composites. Motivated by improved materials requirements of tokamak fusion reactors, the composites are created by depositing ceramic nanoparticles in porous metallic matrices using both constant voltage and pulsed DC EPD. Silicon dioxide particles with a nominal diameter of 20 nm are used as inexpensive surrogates for more application-appropriate boron carbide due to their similar surface chemistry. Fabricated materials are characterized using scanning electron microscopy (SEM) and energetic dispersive x-ray spectrometry (EDX) to visualize coating quality and penetration of the material into the substrate. At low voltage, the deposited mass in constant voltage EPD increases linearly with time while at high voltage it asymptotically approaches a maximum yield of 1.988 grams. Pulsed EPD experiments demonstrate a reduction in deposition yield but also elimination of macro-pore generation in the low voltage case. A non-dimensional parameter, ξ*, relating electrokinetics and diffusion is derived which improves process design for pulsed EPD systems.

Electrophoretic Deposition of Organic - Inorganic Composites for Biomedical Applications

Electrophoretic deposition method has been developed for the fabrication of organic-inorganic composite films, containing bioglass and hydroxyapatite in a hyaluronic acid matrix. The film composition and deposition yield were varied by variation of the electrochemical bath composition and deposition time. The films were studied by scanning electron microscopy, thermogravimetric analysis and X-ray diffraction methods. The deposition method offers the advantages of room temperature processing and allows the fabrication of composite films for biomedical applications.