Morphology Of Composite Coatings Research Articles

Pulsed electrodeposition of MXenes/HAp multiple biological functional coatings on 3D printed porous Ti-6Al-4V bone tissue engineering scaffold

Titanium and its alloys have been widely used as bone tissue engineering scaffold due to their excellent biocompatibility and mechanical strength. In order to promote bone ingrowth, integration and match the mechanical properties of natural bone tissue, this study proposed diamond-like microstructure porous Ti-6Al-4V scaffolds for personalized bone defect repair. In order to prepare the multiple biological functional coatings on the curve surface inside of the 3D printed porous scaffolds, pulsed electrodeposition method was proposed to obtain multiple layers of Ti3C2Tx/HAp composited coatings. Delaminated Ti3C2Tx has an ultra-thin microstructure according to transmission electron microscopy (TEM) observation and is well dispersed in electrolyte. X-ray diffraction (XRD) characterization shows that Ti3C2Tx has been synthesized and regulates more CaHPO4‧2H2O (DCPD) to Hydroxyapatite (HAP) conversion, which is confirmed by Fourier transform infrared spectroscopy (FTIR) at 0.2 mg/mL concentration. Scanning electron microscopy (SEM) shows that the morphologies of composite coatings are closely related to Ti3C2Tx content due to the availability of effective voltages for electrodeposition. By means of finite element method, deposition thickness and distribution of coatings were simulated to explore the precipitation kinetics and selection of electrodeposition parameters and a current density of 15 mA/cm2 was ultimately used. In vitro electrochemical corrosion of Ti3C2Tx/HAp coatings were tested in human simulated body fluid (SBF) to verify its corrosion resistance in physiological environment and Ti3C2Tx/HAp composited coatings possess the best corrosion resistance according to linear scanning voltammetry (LSV) and electrochemical impedance spectroscopy (EIS) tests. In vitro MC3T3-E1 cell culturing studies were investigated to evaluate cell behaviors and biocompatibility of these coatings. The results indicate that cells grow well on the surface of composite coatings without showing cytotoxicity and cell morphologies show a good spreading state and a trend of inward growth.

Effect of Amorphous Boron on the Microstructure and Corrosion Properties of Ni-W Coatings

In this study, a nickel-tungsten/amorphous boron composite coating (Ni-W/B) was successfully deposited on carbon steel using the electrodeposition method. Electrodeposition was performed by dispersing varying quantities of amorphous boron (0, 0.5, 1, and 3 g/L) particles in a Ni-W electrolytic bath. The microstructure and morphology of composite coatings were characterized by scanning electron microscope (SEM). The electrochemical properties of the Ni-W alloy and Ni-W/B composite coatings were studied using electrochemical impedance spectroscopy (EIS), polarization curves, and immersion testing. It was found that the addition of amorphous boron particles to Ni-W coatings can significantly smooth the modified composite coatings and improve the corrosion resistance, probably by changing the corrosion from pitting to uniform corrosion with increasing boron content. The boron concentration of 0.5 g/L in the bath provided the highest corrosion resistance among all the modified coatings.

Nanostructured compositions based on polymeric paintwork materials and environmentally safe biocides

Composite coatings containing iodine- and bromine-containing compounds as biocides have been obtained on the basis of industrial paintwork materials. A number of composite coatings containing biocides - Nitroxynil, Ioxynil and 2,5-dibrom-4-nitrophenol, have been analyzed using a modified technique for assessing biological activity and toxicity for determining the survival rate of Artemia salina crustaceans. It was found that the compositions on the basis of paintwork materials with Nitroxynil show the greatest bioactivity. AFM study of the surface morphology of the developed coatings showed that the introduction of biocides leads to coating structuring at the nanolevel, with the strength of nanostructured coatings on impact decreases by 2-3 times, however, these values are 2 times higher than those of the reference sample --- an industrial copper-containing antifouling paint. The obtained results can be used for further development of environmentally safe protective and antifouling polymer coatings and paintwork materials. Keywords: protective and antifouling paintwork materials, iodine- and bromine-containing biocides, atomic-force microscopy, morphology of composite coatings, surface roughness, impact strength.

Atomistic simulation of Al-graphene thin film growth on polycrystalline Al substrate

Abstract The growth of Al-Graphene composite coatings on polycrystalline Al substrate was investigated by using classical molecular dynamics (MD) simulations. Unlike the diffusion behaviors on single crystal surface, most of adatoms were easily bound by the steps on polycrystalline Al surface, owing to the local accelerated energy. Both Ehrlich-Schwoebel (ES) barriers and the steering effect backed up the volmer-weber growth mode, which was consistent with the dynamic growth process observed in the deposit. The morphology of composite coatings was significantly affected by graphene flakes. Enrichment of graphene flakes gave rise to an increase of the local thickness, and graphene flakes only existed in Al grain boundaries. The size of Al grains in the composite coating visibly decreased when compared with that in the pure Al coating. This grain refinement and the mechanical property can be reinforced by the increase of graphene flakes.

Corrosion Resistance of Ni-ZrO<sub>2</sub> Nanocomposite Coating Prepared by Pulse Electrodeposition with Rotating Cathode in an Ultrasonic Field

The Ni- ZrO2 nanocomposite coatings were prepared by pulse electrodeposition with rotating cathode in an ultrasonic field, and the corrosion resistance of the coatings were studied in 5% H2SO4. The surface morphologies of composite coatings after corrosion were analyzed by scanning electron microscope (SEM). And corrosion rate was tested using an electronic balance. The results shows that, compared with pure Ni coating, pulse current composite coating and pulse current composite coating with ultrasound, the Ni-ZrO2 nanocomposite coating prepared by pulse electrodeposition with rotating cathode in an ultrasonic field has more uniform micro-structure, more compacted grain and lower corrosion rate. Peculiarly, it exhibits excellent corrosion resistance.

Influence of Dispersion Methods on Nano-Al<sub>2</sub>O<sub>3</sub>/Ni+Co Composite Coating by Electrodeposition

The metal and nano-ceramic nanocomposite coatings were prepared on gray cast iron surface by electrodepositon. The nickel and cobalt were used as metal matrix of coating, and the nano-Al2O3 was chosen as second-phase particulates, which had good chemical stability, high microhardness and good wear resistance. The morphology of composite coatings was flatter and microstructure was denser than pure nickel and cobalt coatings. The composite coatings were fabricated by different dispersion methods such as high speed mechanical stir, ultrasonic vibration and ultrasonic vibration together with mechanical stir. The result indicated the nano-Al2O3/Ni+Co composite coating with fine and compact microstructure are obtained compared with pure Ni-Co coating. The nanoparticles were dispersion evenly when dispersion style was ultrasonic vibration together with mechanical stir according to composite coatings SEM images of different dispersion style. The concentration of nanoparticulates reached a maximum value when the dispersion style was ultrasonic vibration together with mechanical stir, at the same time the mechanical property such as microhardness reached a maximum value also. The reason was that nano-Al2O3 caused dispersive strengthening and grain refining.

Effect of surfactant on the fabrication and characterization of Ni-P-CNT composite coatings

In order to disperse carbon nano-tubes in electroless Ni-P coatings different surfactants (sodium dodecyl sulfate (SDS) as anionic surfactant and Hexadecyl Trimethylammonium Bromide (HTAB) as cationic surfactant) were added to the electroless bath and their respective dispersing power was monitored by using ultra violet visible (UV–vis) spectroscopy method. Then Ni-P-CNT coating deposited, using optimum surfactant-to-CNTs ratio of proper surfactant. The morphologies of composite coatings were analyzed using a scanning electron microscope (SEM). Moreover, hardness and corrosion resistance of the applied composite coatings were measured via microhardness, polarization and electrochemical impedance spectroscopy (EIS) methods. Results showed that an optimum ratio of SDS can uniformly disperse CNTs throughout the electroless Ni-P coating, which yields the highest hardness. Corrosion resistance studies showed that the incorporation of CNTs can increase the corrosion resistance of Ni-P coatings due to the filling of pores and micro-holes, while decreasing the metallic area that is prone to corrosion attack.

Novel composite coatings containing (TiC–Al 2O 3) powder

Electroless plating technique has been applied on steel substrate to prepare novel Ni–P composite coatings containing (TiC–Al 2O 3) powder synthesized by self-propagation high temperature synthesis (SHS). The operating conditions for plating process, such as powder content, temperature and pH were optimized. The mechanism of the co-deposition process was also discussed. The results demonstrated that the powder particle incorporation in deposited electrolessed layer depends on pH, temperature and content of powder suspended in plating bath. The maximum (TiC–Al 2O 3) incorporation (approximately 61 vol.%) could be obtained by addition of 10 g/L of powder in the plating solution operating at pH 5.5 and temperature 85 °C. The morphology of composite coatings has been investigated using scanning electron microscopy (SEM). Incorporation of (TiC–Al 2O 3) particles in deposited coating significantly improves the corrosion resistance, wear resistance and increases the hardness of deposited layer.