Electrolytic Deposition Technique Research Articles

Wear performance of MoS2 doped Al2O3 CPED coatings on TC6 titanium alloy

The innovative work presented in the paper focused on microstructures and wear performance of MoS2 doped Al2O3 coatings on TC6 alloy. Nano- and micron-sized MoS2 particles doped Al2O3 coatings (n and m-MoS2/Al2O3 coating) were fabricated on TC6 alloy via cathodic plasma electrolytic deposition (CPED) technique. The microstructures and compositions of the coatings were characterized, the tribological behaviors were tested, and doping mechanism of MoS2 particles was discussed. The results showed that, doped coatings were composed of α-Al2O3, γ-Al2O3 and MoS2. The doping of MoS2 particles promoted the transformation from γ-Al2O3 to α-Al2O3 during CPED process, and increased the compactness and crystallinity of doped coatings. The friction coefficients of TC6 alloy, Al2O3 coating, n-MoS2/Al2O3 coating and m-MoS2/Al2O3 coating were about 0.7, 0.6, 0.55 and 0.45 in sequence, and the wear rates of n-MoS2/Al2O3 coating and m-MoS2/Al2O3 coating were about 75 % and 58 % of Al2O3 coating. MoS2 particles played the role of lubrication and contributed to improving wear performance of doped coatings, both friction coefficients and wear rates were declined, and micron-sized MoS2 particles presented better wear performance than nano-sized particles.

Low Current Density Cathode Plasma Electrolytic Deposition of Aluminum Alloy Based on a Bipolar Pulse Power Supply

The present paper reported a novel bipolar-pulse cathodic plasma electrolytic deposition (BP-CPED) technique with a low current density. This newly developed CPED technique can break down the barriers of the existing CPED technique with higher current density. In this report, ceramic coatings were successfully prepared on aluminum alloy via the BP-CPED technique in an aqueous carbamide-based electrolyte. Data recording results in the reacting process show that there is the current density of the cathode below 0.15 A/cm2 and that of the anode below 0.035 A/cm2, which approximately reaches the level of conventional MAO technique. Interestingly, the addition of PEG into the electrolyte can further reduce the current density and effectively improve the coating quality. The kinetic of the BP-CPED process was discussed based on the evolution of current density/voltage-time curves and spark discharge phenomena. SEM observations illustrate that BP-CPED coatings possess a typical porous-surface feature. XRD analysis indicates that the coating was mainly composed of Al2O3 and Al4C3. Al2O3/Al4C3/ZrO2 composite coatings fabricated after Zr-doping reflected the successful Zr-incorporation into the coating, which demonstrated that the BP-CPED technique can be used to design the coating composition by the doping modification. The direct pull-off and thermal shock tests confirmed that new BP-CPED coatings obtained under the cathodic plasma discharge have excellent bonding strength. It is possible that this novel BP-CPED technique can provide a promising choice in developing the large-area CPED surface treatment for the industrial application.

CATHODIC PLASMA ELECTROLYTIC DEPOSITION (CPED) TECHNIQUE FOR SURFACE STRENGTHENING OF TITANIUM AND TITANIUM ALLOYS: A MINI REVIEW

Due to the unique properties of titanium (Ti) and its alloys, it has a particularly wide range of applications in aerospace, automotive, medical and other fields. However, the problems of low surface hardness, high friction coefficient and low wear resistance of Ti alloys limit its development to a certain extent. The destruction of Ti and its alloys often occurs on the surface of materials such as wear damage, corrosion, and oxidation resistance. Therefore, the exploration and application of surface strengthening technology is particularly important. The cathodic plasma electrolytic deposition (CPED) technology, as a surface modification technology, can achieve better adhesion and facilitate the material to achieve better comprehensive performance. This paper briefly introduces the basic concepts, principles and development progress of CPED. Starting from the preparation of ceramic coatings, metal coatings, diamond-like carbon films and composite coatings, it summarizes the application of CPED in Ti and its alloys. Applications in alloys to improve thermal oxidation resistance, wear resistance, corrosion resistance, and film-based adhesion. At the end, its development in the new era environment is prospected.

Investigation of interfacial thermal stabilities of Nbf/TiAl composites with and without Al2O3 coating in interface

Continuous Nb fiber-reinforced TiAl-matrix composites have tremendous potential for replacing brittle TiAl alloy. However, at elevated temperature, interfacial reaction between fiber and matrix is aggravated, causing instability of the interfacial microstructure and mechanical property of Nbf/TiAl composite. Fortunately, the problem could be solved by introducing fiber coating. Consequently, in this study, Al2O3 coating was prepared on Nb fiber by cathodic plasma electrolytic deposition (CPED) technique. Concurrently, interfacial microstructure changes of the composites were explored during thermal treatment at 1100 and 1200 °C. The results show that, during heat treatment at 1100 °C for up to 100 h, for the composite without Al2O3 coating, the interfacial microstructure changes are as follows: Nb/σ/α2/TiAl→Nb/σ/B2/α2/TiAl→Nb/σ/TiAl, which leads to serious thermal residual stress and cracks in interface. Inversely, the introduction of Al2O3 coating can prevent the formation of brittle σ phase during preparation and the 1100 °C heat treatment. However, under 1200 °C heat treatment, the Al2O3 coating gradually fads away and be replaced by α2-Ti3Al phase. Finally, the interfacial phases including σ and α2 are formed. The existence of the Al2O3 coating can delay the formations of the brittle phases and avoid cracks for a long time, which greatly improves interfacial thermal stability of the Nbf/TiAl composite.

Ultra-trace determination of mercury by platinum-coated tungsten coil trapping cold vapour atomic absorption spectrometry

ABSTRACT Within the scope of this study, a simple, highly sensitive and rapid trapping method for the determination of mercury (Hg) was developed. In this method, the surface of the tungsten coil (W-coil) was coated with platinum using the electrolytic deposition technique. Scanning electron microscopy–energy-dispersive X-ray analyses were performed to examine the surface morphology of Pt-coated W-coil. During the experiment, firstly, Hg vapour generated by tetrahydroborate, used as a reducing agent, was efficiently trapped on the Pt-coated W-coil at collection temperature in hydrochloric acid medium. Subsequently, Hg trapped on the surface of the Pt-coated W-coil was revolatilised by the effect of releasing-stage gases at the optimised releasing temperatures and transported to quartz T-tube atomiser. The experimental conditions have been optimised. Under the optimised conditions, a limit of detection (LOD) of 8.8 ng L−1 was obtained using three times the standard deviation of blank values using Pt-coated W-coil trap cold vapour atomic absorption spectrometry (CVAAS) system. The precision of the measurements was evaluated by relative standard deviation of 4.4%, which is obtained by 11 consecutive measurements of reagent blanks for a collection volume of 6.83 mL corresponding to 90 s collection. The enhancement factors for both LOD (3 s) and characteristic concentration (Co) were found to be 5.09 and 5.02 when compared with the regular CVAAS system without trap. The accuracy of the proposed method was evaluated by analysing BCR 146 R (Sewage sludge), RTC (Sandy Loam 7), ERM-BD151 (skimmed milk powder) and NIST 1641e (mercury in water) certified reference materials (CRMs). There was a good agreement between certified and found values for all CRMs. The results of the application of the developed method in seawater showed the spike recovery ranges from 94.2% to 102.4%.

Optimization of microfluidic functionalization of a plasmonic-based device for selective capture of anti-folic acid in solution

Recent advances in nanoscience and nanotechnology have led to the development of ultrasensitive plasmonic substrates with a theoretical limit of detection of a single molecule. However, the use of such devices in clinical practice and medicine is still hampered by their low selectivity and poor specificity. Even with the support of statistical data analysis methods, identifying specific biomarkers among hundreds of antagonists using an inherently label-free technology is still challenging. Here we develop a microfluidic device to optimize functionalization of the plasmonic substrate with a cysteine-folic acid complex for selective capture of anti-folic acid in solution. Since the latter is expressed by tumor cells, the device can potentially be used to detect and isolate circulating tumor cells from liquid biopsy samples. The plasmonic substrate is a 2D array of gold nanoparticle clusters fabricated by optical lithography and electrolytic deposition techniques. The system combines the sensitivity of a plasmonic substrate with the selectivity of a ligand recognition scheme to achieve identification of specific biomarkers in complex, low-abundance mixtures. The shape of the microfluidic chamber and the flow rate to be used were designed to functionalize the plasmonic substrate and to deliver biological solutions to the active sites of the device in an optimized and uniform manner. Fluorescence and SERS measurements were conducted on the functionalized samples. The results confirmed good and uniform immobilization and colocalization of receptors on plasmonic structures, enabling effective recognition of the target molecule.

Study of wear and corrosion behavior of cathodic plasma electrolytic deposition of zirconia– hydroxyapatite on titanium and 316L stainless steel in Ringer’s solution

Abstract The wear resistance and corrosion behavior of titanium and 316L stainless steel were studied after depositing a composite coating of zirconia and hydroxyapatite using the cathodic plasma electrolytic deposition technique. No sign of adhesive wear was observed on coated samples due to the unique surface morphology of the treated samples, after a pin on disk wear test in Ringer’s solution. The average values of friction coefficient for treated titanium and steel samples were observed to be 0.2 which exhibited a decrease of about 4 fold for titanium and 7 fold for steel with respect to the substrates. As a result of potentiostatic cyclic tests in Ringer’s solution the corrosion current density of coated steel (2.47 × 10–10 A cm–2) was found to be much lower than for the steel substrate (1.87 × 10–7 A cm–2), treated and untreated Ti (6.60 × 10–6, 4.17 × 10–7 A cm–2), indicated the increase in corrosion resistance of steel and decrease of it for titanium after coating.

Cathode electrolytic plasma deposition of (Al0.9Cr0.1)2O3/γ-Al2O3 composite coatings onto Ti45Al8.5Nb0.1Y0.2W alloys for high-temperature applications

The anti-oxidation properties of TiAl-based alloys at above 900 °C are of particular interesting for high-temperature applications. Here, novel (Al0.9Cr0.1)2O3/γ-Al2O3 composite coatings have been fabricated on the surface of Ti45Al8.5Nb0.1Y0.2W alloys by cathode electrolytic plasma deposition technique (CEPDT). The effects of as-prepared composite coatings on the microstructure and long-term oxidation behavior of Ti45Al8.5Nb0.1Y0.2W alloys are investigated through X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), energy dispersion spectrometry (EDS), and isothermal oxidation measurements. Benefited from Cr3+ doping at the Al3+ sites of Al2O3, there shows a much denser structure for the (Al0.9Cr0.1)2O3/γ-Al2O3 composite coatings than single γ-Al2O3 coatings. This favors the decrease of weight gain into 0.773 mg/cm2 for CEPDT-modified alloys with the composite coatings after overall oxidation of 720 h at 900 °C, as compared to mass gains of 3.213 mg/cm2 and 2.331 mg/cm2 for pristine alloys and CEPDT-modified alloys with γ-Al2O3 coatings. It is also found that the microstructural characteristics of the composite coatings after oxidation shows much favorable impact on high-temperature application of TiAl-based alloys in a protective way.

Targeted Delivery of Colloidal Silver for MCF-7 Breast Cancer Treatment.

Amongst various cancer diseases, breast cancer is frequently diagnosed malignancy in women. Existing treatments are inadequate, painful and toxic. New ways of treatments need to be explored. The present work proposes preparation and targeted delivery of a formulation, F-1, for MCF-7 breast cancer treatment. The formulation, colloidal silver (0.76 ppm), was prepared by electrolytic deposition technique and multi surface coatings. Black tea extract (2.25%v/v) was used as a capping agent to tune the morphology of silver nanoparticle and potato extract (6.25%v/v) as a functionalizing agent for targeting MCF-7 breast cancer site. Characterization results show highly pure spherical silver nanoparticles with an average particle size of 15nm. The shift of peaks in the FTIR spectra of formulation confirms the interaction between nanoparticles and extracts. The UV-visible peak was obtained at 525nm, a typical characteristic of silver nanoparticles. In-vivo; anti-cancer study of formulation gave a moderate therapeutic effect in Non-Obese Diabetic Severe Combined Immune Deficiency (NOD-SCID) mice. It is observed that tumor volumes obtained in the case of Formulation-1 were moderately inhibited from days 5 to 9. However, one of the mice in the Formulation-1 group inhibited tumor volume to 1.52 cc similar to one of the mice of positive control group (Adriamycin 1.42cc).

Microstructure and high temperature oxidation behavior of the Al2O3 CPED coating on TiAl alloy

Al2O3 coating was fabricated on the surface of γ-TiAl alloy via cathodic plasma electrolytic deposition (CPED) technique. The microstructure and the composition of the coating were elaborately characterized. The results revealed that, the uniform coating combined well with the substrate, which was mainly composed of α-Al2O3, γ-Al2O3 and trace amount of amorphous Al(OH)3. Moreover, the high temperature oxidation behaviors of the substrate, the coating and their interface were investigated in detail. It was found that the existence of the Al2O3 coating could substantially decline the oxidation rate of TiAl alloy, because of the significant increase in high temperature oxidation resistance.

Study of silver nanoparticles activity against He-La cell lines

In the present work, poly-dispersed silver nanoparticles (Ag NPs), using principles of green chemistry, are synthesised and their anti-cancer activity against He-La cell lines is studied. The synthesis method is easy, simple, environment friendly and does not require any sophisticated labs. One of the physical synthesis methods, electrolytic deposition technique with black tea leaf extract as capping agent, was designed to synthesise silver nanoparticles. Elemental analysis using X-ray patterns show synthesis of highly pure silver nanoparticles. Activity against cell lines was observed in a dose-dependent manner using MTT assay. The IC50 value of sample against He-La cervical cancer cell lines were obtained at 30-fold dilutions of concentration of 178 μg/ml.

Investigation on the Functionally Graded Properties of Zn–6MgO–12MnO2 Composite Coating Fabricated by Dual Anode Electrolytic Deposition Technique

The effect of MnO2 particulates on Zn–MgO composite prepared via electrocodeposition route on low carbon steel was investigated. The experiment was conducted at constant current density of 11.2 A cm−2. The microstructural properties of the coated surfaces were characterized using high-resolution Nikon Optical Microscope (OPM) and scanning electron microscopy attached with energy-dispersive spectrometer (SEM/EDX). The corrosion behaviour was examined using linear polarization method in 3.5% NaCl-simulated seawater environment. The micro-hardness features of the electrodeposits were analyzed by dura scan hardness tester. The homogenizing and thermal stability of the fabricated composite was determined at 200 °C for 4 h. The results show that the structural performance and corrosion resistance property of the coating is dependent on the dispersion strengthening of the particle incorporation. The micro-hardness of the deposited samples increased with the increased addition of MnO2 with over 90%. The improvement in the micro-hardness of the deposited samples suggests that MnO2 has a strengthening effect on the mild steel.

A novel CeO2/MgAl2O4 composite coating for the protection of AZ31 magnesium alloys

A novel CeO2/MgAl2O4 composite coating, fabricated via a cathode plasma electrolytic deposition (CPED) technique followed by hydrothermal synthesis, was developed in this study to explore its potential application as corrosion protection for AZ31 magnesium alloys. The microstructure observed through scanning electron microscopy indicated that reducing the duty cycle of the power source within a reasonable range during the CPED process was beneficial to form a uniform and dense MgAl2O4 coating, which served as an ideal adhesive matrix for a uniform CeO2 coating as the outermost layer. The results of electrochemical impedance spectra and neutral salt spray tests showed that the decoration of the CeO2 layer significantly improved the corrosion resistance of the CeO2/MgAl2O4 composite coating compared to the single MgAl2O4 coating and bare substrate. Cross-cut tests revealed that the adhesion of the MgAl2O4 coating and the CeO2/MgAl2O4 composite coating were both excellent due to the strong binding between the MgAl2O4 coating and the substrate.

Cathodic plasma electrolytic deposition of ZrO2/YSZ doped Al2O3 ceramic coating on TiAl alloy

Abstract ZrO2/yttria-stabilized zirconia (YSZ) doping Al2O3 ceramic coating was fabricated via cathodic plasma electrolytic deposition (CPED) technique. The microstructures and the chemical and phase compositions of the doped coating were characterized, the mechanical properties and the high temperature oxidation resistance were evaluated, and the doping mechanism was also discussed in detail. The results showed that, doped Zr4+ and Y3+ ions could effectively reduce the working voltage during CPED process and increase the content of metastable γ-Al2O3 in the coating. Accordingly, the doped ZrO2/YSZ significantly refined the grain size of Al2O3, as well as remarkably improved the high temperature oxidation resistance, the micro-structural compactness and hardness of the Al2O3 CPED coating. This study displayed here constructed an efficiently method for the fabrication of multifunctional coating on the surface of TiAl alloy.

CeO2 doped Al2O3 composite ceramic coatings fabricated on γ–TiAl alloys via cathodic plasma electrolytic deposition

CeO2 doped Al2O3 composite ceramic coatings were fabricated on TiAl alloys via cathodic plasma electrolytic deposition technique in 0.3 mol/L Al(NO3)3 ethanol electrolytes containing different concentrations of Ce(NO3)4. The effects of CeO2 doping contents on microstructures, elemental compositions, mechanical properties, high temperature oxidation resistance at 850 °C, and wear resistance against GCr15 balls at 200 °C of the coatings were investigated. The results indicated that the contents of CeO2 in composite coatings increased with increasing concentration of Ce(NO3)4, and composite coatings were composed of α–Al2O3 mainly, γ–Al2O3, and a little CeO2. The doping of CeO2 helped to improve the phase inversion from γ–Al2O3 to α–Al2O3. The crystallization and wear resistance of composite coatings increased due to the doping of CeO2. In the electrolyte containing 0.015 mol/L Ce(NO3)4, the coating was the most uniform and compact, and of the best high temperature oxidation resistance and mechanical properties.

Anticancer Activity of Green Silver Nanoparticles against He-La Cervical Cancer Cell Lines

Abstract In the present work, green nanotechnology was used to synthesize silver nanoparticles of different sizes to study their anti-cancer activity against He-La cervical. The synthesis method is easy, simple, environment friendly and does not require any sophisticated labs. This method utilizes principles of green chemistry. Silver nanoparticles were synthesized using electrolytic deposition technique with black tea leaf extract as capping agent. The as-synthesized nanoparticles were characterized using XRD, TEM, and UV-Visible and FTIR spectroscopy techniques. Elemental analysis of the X-ray graphs reveals that highly pure silver nanoparticles are synthesized. Activity of the Ag NPs against cell lines was observed in a dose-dependent manner using MTT assay and it was found that as-synthesized silver nanoparticles inhibited the growth of He-La cervical cancer cell lines almost up to 70-75% respectively. The IC50 value of sample against He-La cervical cancer cell lines were obtained at 30-fold dilutions of concentration of 178 ppm

Integration of MoO2 Composite on the Micro-evolution and Anticorrosion Mitigation of Zn–Ni–MoO2 Thin Films Coating by Electrodeposition System

Zinc–nickel–molybdenum nano-composite coating was deposited on carbon steel substrate using electrolytic deposition technique. The MoO2 integration into zinc–nickel matrix was investigated with reverence to particulate concentrations from 10 to 15 g/L, voltage 5–1.0 V and 1 A/dm2. The effect of the percentage variation of MoO2 particle inclusion into the zinc–nickel lattices’ was seen, and surface morphology, with intermetallic phase transformation of the nano-composite were obtained using scanning electron microscopy coupled with energy dispersive spectroscopy. The corrosion behaviour and micro-hardness characteristics of the Zn–Ni–MoO2 composite deposits were studied using linear polarization technique. The result shows that the incorporation of MoO2 particles into the zinc–nickel matrix disperses evenly with increasing concentration of MoO2 particle and significantly modified the crystal orientation of the Zn–Ni–MoO2 deposit. A content of 10 g vol.% MoO2 particle incorporated Zn–Ni–MoO2 nano-composite deposit was found to obtained good corrosion, wear and better micro-hardness properties.

Mechanism of Cathodic Plasma Electrolytic Deposition on Ti6Al4V Alloy in Al(NO<sub>3</sub>)<sub>3</sub> Ethanol-Aqueous Solution

Barrier layer was prepared by Micro-arc oxidation(MAO) technique in silicate solution, and cathodic plasma electrolytic deposition (CPED) technique was used to fabricate Al2O3 ceramic coatings on Ti6Al4V alloy in Al(NO3)3(30g/L) and ethanol-aqueous solutions. Surface morphology and elemental of the coatings were investigated by scanning electron microscope (SEM) and energy disperse spectroscopy (EDS). Reaction phenomena were recorded and products of reactions were analyzed by infrared absorption spectrum KBr compression method. Furthermore, mechanisms of different electrolytes were evaluated.

Mechanism of Al2O3 coating by cathodic plasma electrolytic deposition on TiAl alloy in Al(NO3)3 ethanol-water electrolytes

Barrier layer was prepared on TiAl alloy by Micro-arc oxidation(MAO) technique in silicate electrolyte, and cathodic plasma electrolytic deposition (CPED) technique was used to fabricate Al2O3 ceramic coating on prepared TiAl alloy in Al(NO3)3 (30 g/L) ethanol electrolytes with different water content by volume. Microstructure, composition and properties of coatings were analyzed, and mechanisms of different electrolytes were evaluated. The results showed that both arc-voltage and work voltage decreased with the increase of water content. Al2O3 CPED coatings were composed of deposition particles and cracks, and contained α-Al2O3 phase mainly and a small amount of γ-Al2O3 phase. The organic reaction mechanism was studied and the performance of TiAl alloy with CPED coating under 950 °C was superior to TiAl substrate.

Corrosion resistance and cytocompatibility studies of zinc-doped fluorohydroxyapatite nanocomposite coatings on titanium implant

In this study, zinc-doped fluoridated hydroxyapatite (ZnFHA) nano-composite coatings were deposited on the surface of commercially pure titanium (Ti-cp) via electrolytic deposition technique. The phase composition, crystallite size, microstructure, and elemental composition of coated specimens were characterized using different techniques including Fourier transform infrared spectroscopy, X-ray diffraction, scanning electron microscopy and energy dispersive X-ray analysis respectively. The influence of coatings on the corrosion behaviour of the specimens was determined by potentiodynamic polarisation in simulated body fluid. In vitro biocompatibility tests, MTT and alkaline phosphatase (ALP) were also employed to assess the cytocompatibility of ZnFHA coating with osteoblast-like MC3T3-E1 cells. Results demonstrated that zinc and fluoride were successfully incorporated into apatite lattice structure. Co-doping of Zn2+ and F− ions decreased hydroxyapatite unit cell volume and grain sizes. Obtained coatings were totally crack-free and dense, which led to decrease in corrosion current densities of Ti-cp in physiological solutions. In addition, cytocompatibility tests demonstrated a good osteoblast proliferation and spreading on ZnFHA. More importantly, results showed that the Zn/F-doping can promote ALP expression, which is a probable effect of a combination of nanostructured surface effects and ion release (Zn2+ and F−). Overall, the ZnFHA coated Ti-cp possesses favourable corrosion resistance and cytocompatibility for the application as biomedical implant material.