Papers by Keyword: Co-Deposition

Abstract: This Paper investigated the corrosion resistance and microstructural performance of zinc-magnesium oxide-tungsten boride (Zn-MgO-WB) composite coating on mild steel. Tungsten boride as an additive was co-deposited with zinc-magnesium oxide on mild steel via electrolytic deposition. The zinc-magnesium oxide and zinc-magnesium oxide-tungsten boride composite coatings were fabricated at the voltage of 0.6 and 0.8 V for 15 minutes and 45 °C. The effects of the deposits on the corrosion properties were examined. The corrosion behaviour was studied using linear polarization and weight loss method in 3.5% NaCl simulated environment. From the results obtained, it is evident that a decrease in applied potential influences the deposition of the coatings. The alloys with tungsten boride in their bath mixture performed better than those without. The zinc-magnesium oxide-tungsten boride (0.8 V) composite coated sample exhibits the least corrosion rate (Cr) of 0.0010482 mm/year and the microstructural examination of the sample via scanning electron microscope (SEM) unveiled homogeneous dispersion of particles and smooth morphology. The smooth morphology, defect-free surface, coupled with the uniform dispersion of the zinc-magnesium oxide-tungsten boride nanoparticles on the steel surface could have been responsible for high corrosion resistance performance of the coating in the simulated 3.5% NaCl medium. More so, the energy dispersive spectroscopy (EDS) revealed the presence of zinc, magnesium oxide, tungsten boride particles.

Abstract: For revealing internal atomic processes in bimetallic nanoparticles, individual hemispherical Ag-Cu alloy particles were grown by direct current (DC) magnetron sputtering. Phase separation of particles was found to be size- and composition-dependent. Particles smaller than 5 nm in diameter remained as a solid solution of the components for all tested compositions (15-80 at.% Ag). At 15 and 30 at.% Ag compositions phase separation was observed only for particles above 5 nm in diameter. Computer simulations by Stochastic Kinetic Mean Field model reproduced the size-dependence of the decomposition and the internal structure of two-phase particles. Theoretical explanation is given for the composition dependence of the phase separation tendency.

Abstract: The Ni-Mo+MoO₂ composite coatings were obtained onto the steel substrate using an in situ co-deposition of a Ni-Mo alloy and MoO₂ powder particles maintained in suspension in the potassium pyrophosphate bath. To characterize the physical and chemical properties of the obtained coatings, SEM, EDS, and XRD methods, were applied. It was found that the co-deposited MoO₂ particles strongly influenced the properties of the Ni-Mo alloy coating. In comparison with the comparable Ni-Mo deposit containing 45 at.% of Mo, the presence of MoO₂ embedded into the composite coating diminished the content of Mo alloyed with Ni to 23 at.%. The electrodeposited Ni-Mo+MoO₂ composite coating obtained under proposed electrochemical conditions contained 25 at.% of MoO₂. The effect of the embedded MoO₂ as composite component on changes of the surface morphology and structure of the Ni-Mo binary alloy, was also discussed.

Abstract: The object of this work was to obtain the Ni+MoS₂ composite electrocoatings by in situ co-deposition of molybdenum (IV) sulfide particles (< 2 μm) and nickel from a suspension plating bath. Physical and chemical characterization of the coatings was carried out using SEM, EDS, and XRD methods. The chemical composition of these coatings of a diphase structure (Ni, MoS₂) was found to be dependent on the current density and temperature of electrodeposition. The optimal electrochemical conditions for embedding of the maximum amount of 26.4 wt.% of MoS₂ into the crystalline nickel matrix, were experimentally determined. The co-deposition process of MoS₂ particles and metallic nickel was discussed based on the adsorption mechanism. Such porous Ni+MoS₂ composite coatings can be proposed as electrode material for hydrogen electroevolution.

Abstract: An Ni-Fe alloy on the surface of nickel foam was prepared by electro deposition. The effects of technological parameters including current density, pH value, temperature and the ratio of [Ni²⁺] to [Fe²⁺] of planting solution on the thickness and iron content of the alloy coating were studied. The cross-section microstructure and surface morphologies were observed by optical microscopy and scanning electron microscope, and the compositions of the alloy coating were analyzed by energy dispersive spectrometer and ICP-AES. Experiment results show that the thickness of the alloy coating is increased with increasing current density, temperature, pH value and the ratio of [Ni²⁺] to [Fe²⁺] of the planting solution. The Fe contents of the alloy coating is increased with increasing current density and pH value of the planting solution, and decreased with increasing temperature and the ratio of [Ni²⁺] to [Fe²⁺] of the planting solution. A 36.2 μm thick alloy layer of uniform and dense coating with the Fe content of 60.5 wt% is obtained under the parameters of n(Ni²⁺)/ n(Fe²⁺)= 4, current density = 10 A/dm² and pH = 4.2 at 50 °C for one hour.

Abstract: Two nickel base multicomponent Ni-Cu-P, Ni-Cu-P-Ce alloy coatings were prepared using electroless plating method in low acidity condition, and examined by scanning electronic microscope, x-ray diffractometer and x-ray flourometer respectively on its morphology, component and structure characteristic. Thermodynamic stability of the two samples were also examined by thermal analysis method. Research revealed a microcrystalline characteristic with compact and tight surficial cellular structure of Ni-Cu-P-Ce coating. And addition of Cu and Ce into Ni-P alloy could enhance thermodynamic stability of the coating, and let coatings transformation temperature from amorphous state to crystalline state increase approximately to 480°C Celsius. X-ray diffraction analysis indicated the reaction products to be crystal grains of nickel atoms and intermetallic compound of Ni₃P.

Abstract: An ideal anodes used for the electrochemical oxidation of organic wastewater should have excellent activity, stability and high oxygen evolution potential. In this paper the CNT (Carbon Nanotubes)-PbO₂ films electrodeposited on stainless steel were prepared. X-ray diffraction (XRD) patterns and SEM images indicated that CNT particles and PbO₂ were able to achieve co-deposit and the composite CNT-PbO₂ films were compact. The cyclic voltammograms of the CNT-PbO₂ films studied in 0.5M H₂SO₄ at a scan rate of 100 mV/s showed that the CNT-PbO₂ film has high electrochemical stability. The results of wastewater treatment indicated that the CNT-PbO₂ anodes have excellent activity in ammonia wastewater treatment.

Abstract: Composite SiN_x/DLC films were deposited on silicon substrate by co-deposition system. The carbon plasma was generated by filtered cathodic arc source, simultaneously incorporated with silicon nitride from RF magnetron sputtering. The silicon nitride sputtering rate was maintained by fixed RF power at 100W while the arc current of FCA was varied from 20 to 80A.The SiN_x/DLC film composition and optical properties were investigated by X-ray photoelectron spectroscopy and spectroscopic ellipsometry respectively. The results revealed that the atomic concentration of carbon increased while those of silicon and nitrogen decreased with increasing arc current. The oxidation was found on the film surface and related to the atomic concentration of silicon. The optical properties can be changed as a function of carbon concentration by setting different arc current. In this work, the volume percentage of carbon obtained from spectroscopic ellipsometry using Bruggeman EMA model showed good numerical correlation with the atomic percentage of carbon from XPS analysis with the range spanning across 75-95 at. %.

Abstract: Al-Ni Alloys were obtained from NiCl2-AlCl3-1-ethyl-3-methylimidazolium bromide ([EMIM]Br) ionic liquid at room temperature. The analysis of Al-Ni alloys that co-deposited at different potentials for 2h were performed using Scanning Electron Microscopy (SEM) and X-ray diffraction analysis (XRD). It appears that Ni has been rapidly solidified in the alloys and homogeneous Al-Ni alloys can be obtained at room temperature. As increasing the overpotential, the amount of Ni in the alloys was decreased whereas the amount of Al was increased. The chloride pitting potentials of alloys with the molar ratio of NiCl2/AlCl3/[EMIM]Br 0.03:2:1 was approximately 0.3 V more than pure Al.

Abstract: This study presents a novel and economical compound technique that combines co-deposition with micro w-EDM for precisely developing a multiple micro diamond wheel-tools. The wheel-blank is made of diamond grit of 0-2 µm grade by electrochemical technique, in which employs a designed micro tank with ideal convection and mini porous carrier. Using a pore size of 5-10-µm in the porous carrier, a suitable interval chip-pocket of 2-3 µm on wheel-blank can generate naturally. Formation of the multiple wheel-tools is carried out via the processes of slicing, thinning and dressing simultaneously to become grinding edges array. A circuit of resistance capacitance, which provides a very short pulse and high peak, is employed as the electrical discharge power to help in achieving a very shallow and narrow discharge cavity. The thickness of each grinding edge can be machined down to 10-µm. The experimental result shows that the proposed technique is an effective method to fabricate precision micro diamond wheel-tools.