Search

Synthesis of nanostructured carbon allotropes using CO2 as a cheap carbon source is challenging and usually limited by high temperature activation. Herein, formation of 3D nanostructured carbon allotropes including nano-graphene and single crystalline nanodiamond films is feasible at room temperature on various single crystal metals (e.g., Bi, Ag, Zn, and Co) that were formed under the dynamic CO2 electrochemical reduction reaction environment at relatively low applied potential (−1.1 to −1.6 V vs. Ag/AgCl). The nanocrystalline carbon was obtained as the major products from CO2 (≥96% selectivity, ∼1 μm thickness) without any liquid products. Upon applying the negative potential, nanoclustering of the self-limiting ultrathin metal oxide layers of metal particles on the highly conductive substrate could lead to formation of negatively charged metal clusters, which were well stabilized by the ternary electrolyte system containing [BMIm]+[BF4]-/propylene carbonate/water. This system allows the reduction of CO2 into single atoms C∗ and the subsequently electrocrystallization of C∗ into carbon allotropes on the crystallographic planes of the single crystal metals formed as the building blocks. The CO2-derived Ag–C/epoxy composites show promising thermal conductivity. The results present a breakthrough advancement in the growth of nanostructured carbon allotropes from CO2 by the viable negative CO2 emission approach.

Kenaf is a renewable resource that has recently attracted great interest owing to its fast growth which makes a large volume of raw material in a short time. Due to its large surface area and high water adsorption, kenaf cellulose was readily prepared as a substrate immobilized with dimethylglyoxime (DMG) for specific Ni(II) sensor. Herein, a simple and highly sensitive colorimetric detection of Ni(II) using kenaf cellulose-based 3D printed device was successfully created. The large volume (1.0 mL) of Ni(II) solution can be applied on a kenaf cellulose-based 3D printed sensor coupled with a multilayer of adsorption pads. This system provides a wide linear range (0.1–100 mg/L) with an extremely low limit of detection (40 μg/L), significantly improved from a conventional filter paper-based device (1.0 mg/L) for 25 uses, and it enables highly sensitive colorimetric detection of Ni(II) contamination in industrial wastewater without any use of external instruments validated with a standard ICP-OES method.

With environmental awareness in societies, bioplastics continue to receive increasing attention and utilization rate. Polylactic acid (PLA) is one of the most important biopolymers in the market today, owing to its high strength and relative ease of forming. Unlike the common structural, fossil fuel-based plastics, such as Acrylonitrile-Butadiene-Styrene (ABS), the surface of PLA cannot be readily metallized in preparation for electroplating using the conventional plating-on-plastic (POP) process. This partially limits the wider use of the material for functional and decorative applications. In this research study, we systematically explored three strategies for metallizing the surface of PLA, namely, (A) chemical etching and palladium activation technique, (B) polyelectrolyte multilayers (PEMs) and Ag nanoparticle deposition technique, and (C) Ag conductive painting technique. PLA samples, prepared by Fused Deposition Modelling (FDM) 3D-printing technique, were metallized by various techniques followed by electroless deposition and electroplating of copper layers. The study was performed comparatively with respect to the ABS surface. The samples microstructures, chemical distributions, and plating characteristics were assessed with optical and scanning electron microscopy. The adhesion of the metallic coatings was analyzed using scratch test and tape test. Although uniform deposition of copper layers on PLA surfaces could be achieved using all three metallizing methods under investigation, the three methods were found to provide different degrees of benefits with respect to deposition rate, surface uniformity, and process simplicity.

In the present study, a systematic investigation is performed to assess the relationship between electroplating parameters, pore morphology and internal surface area of copper deposits which are promising to serve as electrodes for electrochemical reduction reactions of carbon dioxide (CO2). A set of porous copper deposits are fabricated with the dynamic hydrogen bubble template method. The microstructural and Brunauer–Emmett–Teller (BET) analysis demonstrate that current density, deposition time, and bath composition control pore size, strut size, and hence surface area which could be as high as 20 m2/g. Selected sets of porous copper electrodes are then employed in the electrochemical reduction reaction test to determine their conversion performance in comparison to a monolithic copper surface. From the gas chromatography (GC) and nuclear magnetic resonance (NMR) analysis, porous copper is shown to provide higher rates of production of some important chemicals, as compared to copper foil electrodes. Porous copper with fern-like morphology serves as a promising electrode that yields relatively high amounts of acetaldehyde, acetate and ethanol. The study thus presents the opportunities to enhance the electrochemical reduction reaction of CO2 through microstructural engineering of the copper surface, which benefits both CO2 reduction and generation of chemical products of high value.

Modifying a surface to achieve a superhydrophobic characteristic has increasingly become an attractive approach to protect oxidation of metals and alloys. This review comprehensively discusses the state of the art of superhydrophobic surface modification with a particular focus on the corrosion inhibiting quality. Generally, there are two main approaches to induce superhydrophobicity, namely application of low surface energy coating and roughening of a surface to a binary micro/nano-rough structure. These strategies, which are often combined and found to complement one another, have been successfully demonstrated to provide corrosion-resistant improvement with moderate durability for a number of metals and alloys, including stainless steels, aluminum, magnesium, titanium, copper, and zinc.

Ni-W-B alloy coating containing amorphous boron particle were fabricated by direct current electrodeposition on low carbon steel substrates. The effect of boron concentration in the plating bath on the surface morphology, the overall boron content in the deposited layers and the hardness of the resulting coating layer were investigated. Scanning electron microscopy (SEM) revealed that the surface morphology of the Ni-W-B coating layer was largely modified by the boron particle loading in the electroplating suspension. Distinct nodular structures were observed in these samples. Energy dispersive X-ray spectroscopy (EDS) spectra suggested that the overall boron content in the coating layer increased with increasing boron particle loading from 1 to 3 g/L. Too high boron particle loading of 10 g/L resulted in lower overall boron content. The highest hardness of 680.86 ± 17.67 Hv was obtained from Ni-W-B/B coating layer fabricated using the boron particle loading of 5 g/L.

The effects of alkaline non-cyanide zinc plating bath formulation on the plating characteristics and deposit properties are investigated. Scanning electron microscope and X-ray diffractometer are used to study the surface morphology and texture of the zinc deposits respectively. Uniform and compact coatings with a dominant (110) texture are obtained for all of the bath formulations. Nevertheless, significant differences in surface morphology and relative preferences for the (110) and (100) planes were found to result from the concentrations of zinc and sodium hydroxide in the bath. Electrochemical impedance spectroscopy and potentiodynamic polarization scan were employed to evaluate the corrosion resistance. The coatings with a moderate Zn (8-11 g/L) and controlled NaOH (120 g/L) contents show good corrosion resistance, with the corrosion current and corrosion rate being the lowest at 8 g/L of Zn and 120 g/L of NaOH. The ratio of texture coefficient, morphology, and compressive residual stress from different bath composition contribute to the corrosion resistant property. The findings from this work should provide useful information of electrogalvanized zinc coatings with enhanced corrosion resistance.

An integrated system based on nickel foam (Ni foam), titanium dioxide sol/graphene nanocomposite and lactate oxidase (LOx) has been successfully developed for the sensing of lactate. A TiO2/graphene nanocomposite was readily synthesized and coated on a 3D porous Ni foam electrode to develop a novel electrode in an electrochemical biosensor. The as-prepared nanocomposite and the modified Ni foam were characterized by Fourier transform infrared spectroscopy (FT-IR), transmission electron microscopy (TEM) and scanning electron microscopy (SEM) to verify the well intercalation of graphene within TiO2 sol and successful coating of such nanocomposite on Ni foam surface, respectively. Comparing with an unmodified Ni foam, TiO2 sol/graphene modified Ni foam offered a drastic increase in current response signal (a 28-fold) toward H2O2 detection, suggesting a potential application of this system as a sensitive electrochemical sensor. Then, LOx was immobilized onto the modified electrode for lactate sensor via H2O2 detection. Interestingly, the combination between graphene and TiO2 sol enhanced both sensitivity and stability of this sensor. A wide linear range of 50 μM to 10 mM with a detection limit of 19 μM was obtained for lactate without interfering effect from ascorbic acid, dopamine, and glucose. This platform was sensitive enough for early diagnosis of severe sepsis and septic shock via the detection of concerned lactate level. Eventually, it was successfully applied to detection of lactate in a complex biological fluid.

This work presents a systematic study of the effects of current pulsation on soft magnetic properties and giant magnetoimpedance (GMI) of nickel-iron (NiFe) coatings electrodeposited on copper wires. The specimens were prepared by the electrodeposition technique with controlled bath compositions and varied applied current waveforms. The microstructural and chemical investigations indicate that current pulsation with 50% duty cycle and 50 Hz frequency provides significantly smoother coating surface of uniform nodules, with comparable Fe content but different phase composition, as compared to the direct current condition. The vibrating sample magnetometer evidently shows that the deposits prepared with a pulsed current exhibit relatively small coercivity, below 4 Oe. Using the four-point probe technique, the MI ratio of the pulse deposits is found to reach a significantly high value above 2,000% with decent sensitivity. The benefits of current pulsation in improving the characteristics of NiFe deposits, and correspondingly the alloys’ soft magnetic properties and MI effects are demonstrated.

Systematic investigation of 1-benzyl pyridinium-3-carboxylate (BPC), a brightener in alkaline non-cyanide zinc electroplating using reversed phased high-performance liquid chromatography is performed for the first time. This approach is applicable for monitoring of plating bath, brightener consumption and accurate bath replenishment to produce satisfied electroplated zinc surface. The binding energy between zinc and the additives is calculated by density functional theory (DFT) to verify the contribution of additives in the electroplating process. Following a long-term plating session for 8 h, depletions of zinc and additives are found to largely affect brightness and surface morphology of the electrodeposited zinc surface. The replenishment of zinc and additives maintains the bath in an appropriate condition to provide the desired coating properties. The effects of organic additives on zinc deposition including appearance, glossiness, thickness, surface morphology, and crystal structure are systematically investigated. Furthermore, the study demonstrates synergistic effects of brightener and leveler on microstructure, grain refinement, and preferred crystallographic orientation of the electrogalvanized coatings.

Thermal annealing could potentially serve as important instrument for controlling and improving the properties of the soft magnetic films. A systematic investigation is carried out in this study to determine and analyze the effects of low-temperature heat treatment on the microstructure and magnetic properties of CoFe films of different chemical compositions. The coercivity of the alloys is found to be critically influenced by surface roughness and uniaxial anisotropy, which is in turn affected by thermal annealing. The saturation magnetization on the other hand is controlled mainly by chemical compositions.

The wetting behavior of copper is important for many engineering applications. The present study demonstrates a method to modify the wetting characteristics of copper surfaces by developing porous structures via the promotion of hydrogen bubbles and rapid and nonuniform growth of the deposits. The porous copper deposits are fabricated with various controlled plating parameters, and subsequently stored in different conditions, including air, water, and saline solution, to assess the possible influence of the storage conditions on the wetting behavior. The study shows that the wetting angles can be tailored by electrodeposition parameters, namely, plating bath formulation and applied current density, which influence the morphology of the porous structure. The storage conditions are found to largely affect the wetting behavior, owing to their influence on surface morphology and surface chemistry. Hydrophobic and hydrophilic surface characteristics are developed in the copper deposits stored in air and in the saline solution, respectively.

Galvanized coatings are widely used in industry, but the influences of microstructure on corrosion behaviors have rarely been studied in these coatings. The present investigation aims to systematically analyze crystallographic texture and nanostructural features of galvanized coatings as well as their chromate conversion layers, and examines the relationship between their structures and corrosion properties. Three groups of electrogalvanized coatings fabricated with different types of plating additives are studied, using a series of complementary characterization techniques. The corrosion behaviors of the deposits are then analyzed with the potentiodynamic polarization technique and salt spray test, in light of their structural characteristics. The study reveals that the additives critically influence the microstructure of both the galvanized coatings and chromate layer. The corrosion resistance of the coatings can be enhanced by suppressing the {100} crystallographic planes of zinc and minimizing defects along the zinc/substrate interface, and by promoting formation of an amorphous-oxide layer in the chromate film.

Electroless Ni-Zn-P coating with the optimal content of Ni and Zn in the alloy provides high corrosion resistance for steel. Ni-rich phase of this high hardness Ni-Zn-P alloy offers barrier protection property and sacrificial protection property is obtained from the alloy with proper content of Zn. In this work, the Ni-Zn-P coatings were prepared on steel substrates by using alkaline electroless deposition. The parameters of deposition process including complexing agent concentration, bath pH, zinc ion and nickel ion concentration were systematically studied. The microstructural morphology and elemental composition of the coatings were characterized by scanning electron microscopy. It was found that complexing agent, zinc ion and nickel ion concentrations play important role on Zn content of Ni-Zn-P alloy whereas alkalinity of the solution bath directly affects the deposition rate. The results of corrosion resistance investigated by linear polarization illustrate that the corrosion potential (Ecorr) of Ni-Zn-P coatings is negatively shifted by an increase of Zn content in the alloys. From this work, Ecorr of 83%Ni-11%Zn-6%P coating prepared in this system is slightly lower than steel. To achieve a higher effect of sacrificial protection for corrosion protection of steel, Ni-Zn-P with higher content of Zn should be further studied.

In this work, microstructure and corrosion properties of zinc electroplated steel before and after black chromating was investigated. The test samples were prepared by electrodeposition process, using a commercially-available alkaline electrolyte. Subsequently, the galvanized samples were applied with a black chromate-based passivation layer and a clear top-coat layer. Their microstructures were examined using X-ray diffractometry and scanning electron microscopy. The corrosion resistance of the samples was assessed with the salt spray test, following the ASTM B117, electrochemical impedance spectroscopy (EIS), and potentiodynamic polarization in 5 wt.% NaCl solutions. The study showed that zinc electroplated steels exhibit (110) crystallographic orientation. The passivation and top-coat layers did not affect the microstructure of the zinc layer, and covered uniformly on the zinc layer for all sets of samples. The corrosion resistant results obtained from salt spray testing and electrochemical testing revealed that the microstructure of zinc coatings prepared by using different applied current did not influence on their corrosion resistance markedly. While black passivation followed by top coating provided a significant improvement on corrosion resistance of the coatings.

By the time the pipelines and other facilities reach their service lives and are to be decommissioned, Mercury (Hg) shall be assessed and monitored as per regulations and for the sake of health and environment care. Company and research institute partners have been therefore developing innovative method to prove the cleanliness of the pipelines and other facilities especially for on-site works. In general, spectrophotometry such as cold-vapor atomic absorption spectrometry is proposed to be as standard technique to measure Hg level in samples. Even though this method is sensitive for lowconcentration detection, to meet the sensitivity requirement, it needs extensive sample preparation and long analysis time. Consequently, this technique is not suitable for analysis at worksites. Therefore, a sensitive, selective, rapid and portable Square Wave Anodic Striping Voltammetry (SWASV) has been developed for the determination of ultra-trace levels of Hg in samples. Hg is contaminant and inherently found in Oil and Gas production and operation assets, especially in the Gulf of Thailand. It may interact and remain in pipelines and other facilities in the production and operation conditions. The level of Hg contamination is normally so low that some specific methodologies based on chemical laboratory are required to confirm such low concentration level (ppb to ppm level). However, it is not common to set-up laboratory station for Hg detection such as cold-vapor atomic absorption spectrometry at worksites especially at offshore remote well head platforms. SWASV could be therefore an alternative method to detect and screen Hg-contaminated pipelines and facilities. The method does not require any separation or pre-concentration steps and is directly applied to determine levels of Hg in environmental or retreived samples. The comparison between the proposed SWASV and ICP-OES standard method was performed on the samples, the concentrations obtained by both methods were in agreement with the certified values of Hg, according to the paired t-test at 95% confidence level. SWASV is therefore being developed further to put into mobile lab (poratbale tool). The proposed method is capable of analyzing Hg on-site, reducing total analysis time and monitoring very low concentration of Hg (even down to ppb level) with simple preparation and operation. It could be therefore recommended as an alternative option or as screening method to analyze various samples contaminated with Hg as part of decommissioning activities.

Despite wide usage of electrogalvanized coatings in various applications, characterization studies on their micro/crystal structure, and the understanding of how they correspondingly affect the properties, such as corrosion, are rather limited. This is mainly attributed to some difficulties in preparing and examining the zinc coating layers, owing to their intrinsically low corrosion resistance and refined nano-scaled crystallite size. This study aims to examine such challenges systematically and propose some mitigation strategies. Particularly, sample preparation processes, including surface finishing for metallography and sample thinning processes are explored. Furthermore, a range of electron microscopy techniques, including scanning electron microscopy (SEM), electron back scattered diffractometry (EBSD), and transmission electron microscopy (TEM) are investigated in relation to the achievable clarity of microstructural details of electrogalvanized coatings.

An electrochemical deposition is a fast and cost-efficient process to produce film or coating. In this research, Ni-Ti electrodeposition is developed by codepositing a Ti-dispersed Ni-matrix layer from a Ni-plating solution suspended with Ti particles. To enhance the coating uniformity and control the atomic composition, the pulsed current was applied to codeposit Ni-Ti layers with varying pulse duty cycles (10 to 100 pct) and frequencies (10 to 100 Hz). The microstructures and compositions of the codeposited layers were analyzed by scanning electron microscopy, X-ray diffraction, and X-ray fluorescent techniques. The pulsed current significantly improved the quality of the Ni-Ti layer as compared to a direct current. The Ni-Ti layers could be electroplated with a controlled composition within 48 to 51 at. pct of Ti. The optimal pulse duty cycle and frequency are 50 pct and 10 Hz, respectively. The standalone Ni-49Ti layers were removed from copper substrates by selective etching method and subsequently heat-treated under Ar-fed atmosphere at 1423 K (1150 °C) for 5 hours. The phase and microstructures of the post-annealed samples exhibit different Ni-Ti intermetallic compounds, including NiTi, Ni3Ti, and NiTi2. Yet, the contamination of TiN and TiO2 was also present in the post-annealed samples.

Nickel-tungsten-boron/amorphous boron particle (Ni-W-B/B) composite coatings were co-electrodeposited on the surfaces of low-carbon steel by direct current electrodeposition. The microstructure, hardness friction and wear properties of the deposits were investigated. Scanning electron microscopy (SEM) revealed uniform deposition of a nodular structure in the Ni-W-B/B composite coatings. Energy dispersive X-ray spectroscopy (EDS) was employed to qualitatively compare the amount of boron in the composite coatings prepared using bath temperatures of 50 °C and 75 °C. Incorporation of amorphous boron particles was found to enhance the hardness of the Ni-W-B coatings by as much as 11.8%. A maximal hardness value of 680.9 ± 17.7 HV0.05 was obtained from the Ni-W-B/B composite coatings with 5 g/L boron loading and prepared using the higher plating bath temperature, 75 °C. Hardness could also be further improved by approximately 16.1% through heat treatment at 500 °C. Furthermore, using a plating bath temperature of 75 °C also resulted in films with lower friction coefficients and better wear resistance.

Hard chrome is an important coating used widely in the industry, yet the understanding of its plating process in relation to surface crack development and corresponding properties has not been fully established. This research has investigated the development of surface crack of hard chrome through the variations of chromic acid concentration, catalyst content and plating temperature, and subsequently examined how crack density contributes to wettability and mechanical properties in dry and lubricated environments. The study has revealed that an increase in crack density in the low-to-medium crack range (150–400 crack/cm) is generated due to the decrease in the chromic acid-to-catalyst volume ratio and the increase in temperature. These process parameter adjustments has led to reduction of cathodic current efficiency and hydrogen gas development which can ultimately generate stress in the deposits. An increase in crack density has contributed to the marked improvement of wettability with a decrement of the contact angle from 8.5° to 4.2°. Hardness has also been found to increase from 720 to 830 HV. Furthermore, crack density increment has also resulted in the reduction in wear rate of the coatings in a non-lubricated condition. The hardness of the coating and the presence of cracks appear to largely influence the improvement of the wear resistance.

A Ni–P–TiO2 coating was readily prepared by direct incorporation of nano-TiO2 sol into a Ni–P solution followed by electroless deposition. This coating was applied as a working electrode in an electrochemical sensor for the first time. The morphologies of the TiO2 sol and the coated surface were well characterized by TEM, SEM and AFM. The high hydrophilicity of this surface was verified by contact angles of 40.7/41.8. Here, the appropriate amount of TiO2 within the nanocomposite was optimized (2 g L−1) prior to applying as an electrode. Interestingly, the electrocatalytic activity of the coating towards the oxidation of alcoholic compounds was investigated by linear sweep voltammetry. Apparently, incorporation of TiO2 into the composites substantially improved the electrocatalytic activity of Ni–P and 2 layers of Ni–P/Ni–P–TiO2 coating provided the highest sensitivity for all analytes, especially for sorbitol. A low LOD value of 1.0 nM and a wide linear range of 2.0 nM to 0.2 mM were achieved for sorbitol. Furthermore, a high stability and high reproducibility (2.96% RSD) for this system were obtained. Owing to ultra-high sensitivity, wide linearity, high stability, easy preparation and low cost, it might be a promising tool for early diagnosis of diabetes via sorbitol detection.

Ni–W–diamond composite coatings were prepared by pulse current electrodeposition on carbon steel. It is found that the pulse current can affect the rate of diamond incorporation and the content of tungsten alloyed in the matrix. The effect of the duty cycle and frequency on the hardness of the coatings is associated with the amount of diamond particles and the tungsten contents in the Ni–W matrix. Moreover, the diamond content is the primary mechanism in improving the hardness of composite coatings.

Chromate conversion coating is an important surface finishing process for electroplated zinc coatings that are widely employed in automotive applications. In addition to providing enhanced corrosion protection, the conversion coating offers a shade of colors to the coated products, both for aesthetic and functional benefits. Due to the stringent requirements on environmental issues, the industry is replacing the conventional hexavalent chromate with a more environmentally friendly trivalent chromate for the production of coatings. This effectively poses the requirement of the fundamental understanding on how the keys processing parameters of trivalent chromate conversion coating may relate to coloring of the coating products.In this work, for the first time, a systematic study is carried out to correlate the electroplating parameters, including the current density and electrolyte’s additives, on the formation of the trivalent chromate conversion coating, and hence the color appearance of the top-coats. Focusing on the black conversion coating, the color and optical properties are analyzed using a colorimeter and an optical spectrometer. The results notably show that, while the additives highly influence the observable shade of blackness, current density affects the optical properties in the visual spectrums. The microstructural and chemical characterization techniques, namely FE-SEM, OM, and XRD, are used to shed some light on the underlying mechanism that controls the color appearance. The understanding developed in this study will impact the design and fabrication of the electrogalvanizing products of desired color and esteemed functional performance.

Man-made or unnatural wind from the industrial exhaust air system is an alternative wind resource for countries with natural low-speed or intermittent wind such as Thailand. It has strong and consistent wind speed when compared to the natural wind, with velocity about 5 to 10 m/s at a distance of 5 cm from the exhaust air outlet. However, some negative impacts to the exhaust air system performance was observed when a conventional wind turbine was employed. The objective of this research is to feasibility study the practicality of a prototype shaftless small scale horizontal axis wind turbine (SSHWT) to generate electricity from the exhaust air of the industrial exhaust air system. Aerodynamic, blade and generator designs were addressed in this study to maximize energy output and minimize negative impacts to the performance of the original exhaust air system. The performance of SSHWT was tested with a selected industrial fan that is widely used in industrial sections. The results showed that the SSHWT could generate electricity with less negative effect to exhaust air system performance. However, it still needs further improvements caused by the voltage output is too low. By the concept design, this innovative wind turbine is compact, thus needs only small space for installation. This SSHWT has high market potential for low wind speed countries to take advantage of unnatural wind resources which are better in terms of efficiency and economy for sustainable energy development.

The effects of current density and Ti particle loading in a plating bath on the morphology and hardness of Ni-Ti composite coatings via an electrochemical-codeposition process were investigated. The Ti-reinforced Ni-matrix composite coatings were codeposited on copper substrates using a Ni-ion electrolytic solution stably suspended with -45 micron Ti particles. Within the current studied range, the coatings’ Ti contents are in the range between 46 and 62 at.%. The morphology appeared to vary with current density. Structures of the Ni-Ti composite coatings produced under low current density conditions revealed denser structures, which is in contrast to the more porous structures noted in the coatings produced under high current density. An initial increase of current density from 100 to 150 mA/cm2 also tends to raise Ti coating content. The reinforcement of Ti particles in the coatings also increased their hardness, which is attributed to the possible role of the embedded Ti particles in hindering matrix deformation. The effect of Ti loading on the coating’s Ti contents was not significant under conditions used in the present study

Nanocrystalline CoFe films were fabricated by electrodeposition process for an investigation of the relationship between the alloys’ characteristics and their magnetic properties. The study shows that coating thickness promotes softer magnetic properties of the films, and induces changes of film roughness, preferred orientation and domain pattern. The preferred orientation of the ~1 μm films (thin films) is (110) plane, whereas that of the ~3 μm films (thick films) are (110) and (200) planes. The magnetic domain of the thin films exhibit a stripe-liked pattern, whereas a bubble-liked pattern appears in the thick films. Iron content significantly affects the magnetic properties of the thick films. In this study, the 57.3wt.%Fe thick film has the highest saturation magnetization, and the 80.0wt.%Fe thick film shows the lowest coercivity.

Galvanized steels are widely used in construction, electronic, and automotive applications. By applying heat treatment after the hot-dip galvanizing process, zinc and iron in the galvanized coatings are interacted and series of zinc-iron intermetallic phases are developed. Correspondingly, the properties of galvanized steels may be enhanced. In the recent past, attempts have been made to develop kinetics models to help predict the interdiffusion of zinc and iron in the hot-dip and annealing steps, yet they are generally complicated and sometimes do not agree well with the actual data. In this work, we extend the prior works to develop a mathematical model for predicting the interdiffusion of zinc and iron and the growth of intermetallic phases during annealing that is less complicated, yet provides reasonably accurate results, by using an explicit finite difference method (FDM) along with a special treatment at the boundaries of each phase. The data from literatures are compared and discussed to justify the accuracy of the model.

The present studies investigate the wear response of composition-modulated multilayer Ni-W coatings as fabricated by electrodeposition. By regulating the pulse waveforms of the applied currents, the chemical composition, grain size, and the individual layer thickness of the electrodeposited Ni-W CMMC can be tailored. The ball-on-disc test and the subsequent microstructural analysis indicates that the wear resistance and friction coefficient of Ni-W CMMC are influenced by the composition and the thickness of the individual alternating layer. The decrement of interlayer’s size monotoically increase wear resistance and friction coefficient.

H13 steel has been widely used in several metal working industries. Plasma nitriding is employed for improving surface hardness, but it significantly decreases corrosion resistance of H13 steel. To improve corrosion resistance, Cr plating before and after plasma nitriding is studied in the research. Surface characterization, phase analysis, hardness and corrosion test were done to evaluate the appropriate method to improve corrosion resistance. It was found that Cr plating after plasma nitriding can improve the corrosion resistance close to as-heat treated sample. The formation of Cr can increase the corrosion potential to-310.66 mV(Ag-AgCl) comparing to-349.54 mV(Ag-AgCl) of as-heat treated sample. For the corrosion resistance at constant applied voltage tested by potentiostatic technique, the sample with plasma nitriding prior to Cr plating shows the lowest corrosion current which implies the lowest corrosion rate. For the process in which Cr plating is applied before plasma nitriding, CrN layer can be formed on the surface, but this layer is very thin (about 100 nm thick). This thin layer retards nitrogen diffusion; hence, nitrided layer beneath CrN layer cannot be formed. With only thin layer of CrN, both corrosion resistance and micro-scale surface hardness cannot be improved.

An elemental nickel (Ni) or cobalt (Co) is typically introduced to tungsten carbide (WC) prior to powder injection moulding process (PIM) for hard metal fabrication to enhance toughness and tool life. Mixing of powders is normally practiced, although it requires a long processing time for homogeneous mixing. In this study, as an alternative method, an addition of Ni via the electroless deposition method is investigated. The key process parameters, including the concentration of the complexing agent, namely sodium citrate, and bath pH, are systematically examined in relation to deposition rate and deposits size, microstructure, and chemical compositions. As the bath pH is increased to higher alkalinity of 10 and the Ni ion to complexing agent mole ratio is controlled under 1:1, a stable electroless nickel solution and a relatively high deposition rate with about 15% weight gain for 1 hour deposition duration are achieved. The phosphorus (P) content, obtained in the range of 5-9 wt%, is largely influenced by the bath pH. While a rapid deposition rate is associated with preferentially deposition of Ni on pre-deposited Ni sites, a low to moderately high deposition rate results in more uniform incorporation of Ni-P alloys in WC powder mixture.

Mechanical response of polyurethane open-cell foam with electrodeposited copper coatings under compressive loads is investigated via experimental characterization. Commercially available open-cell polyurethane foam specimens are copper deposited using electroless and electro-deposition techniques. Thickness and composition of the coating are controlled by varying the deposition time to 30, 60 and 90 minutes. Micrographs of the coated foam structure show that the coating thickness is higher at the outer surface, and the averaged thickness linearly depends on the deposition time. The coated foam exhibits a stiffer compressive response than that of the uncoated one. When unloaded, the copper coating layers fracture at the center of foams ligaments, and fall off from the foam structure.

The anatase nanocrystalline TiO2 samples were synthesized by a sol–gel method with a thermal treatment under air and H2 atmospheres at 350 °C and employed as the supports for preparation of Pd/TiO2 catalysts by impregnation and electroless deposition methods. The surface Ti3+ defects on the TiO2 significantly increased when treated under H2, compared to air, with no changes in the average crystallite size, specific surface area, and pore structure. The CO chemisorption and IR of adsorbed CO results showed that the use of H2-treated TiO2 resulted in higher Pd dispersion and the formation of more isolated adsorption sites, hence improving the catalytic performance in terms of both acetylene conversion and ethylene selectivity.

Pd/TiO2 catalysts were prepared by the electroless deposition method with and without SnCl2 sensitization and employed in the liquid-phase selective hydrogenation of 3-hexyn-1-ol under mild conditions (40 °C, H2 0.2 MPa). As revealed by inductively coupled plasma optical emission spectroscopy, transmission electron microscopy, and CO pulse chemisorption, the use of conventional SnCl2/PdCl2 solution resulted in a larger amount of Pd being deposited (0.98 wt% Pd) on the TiO2 and higher Pd dispersion (6.6 × 1017 molecules CO/g Pd) than the SnCl2-free activation (0.87 wt% Pd, 5.3 × 1017 molecules CO/g Pd). However, tin was found to remain on the catalyst in the form of Sn4+ and partially covered the Pd surface. Large Pd particles were formed after electroless plating of Pd when the TiO2 was activated by PdCl2 followed by the reduction using NaH2PO2 (SnCl2-free process). The selectivity towards cis-hexen-1-ol after complete conversion of 3-hexyne-1-ol was much improved using the electroless deposition catalysts (selectivity 60–87 %) compared to the ones prepared by conventional impregnation method (selectivity 4 %). The results in this study show the advantages of electroless deposition technique as a simple methodology to synthesize highly selective catalysts for the production of cis-alkene in the alkynes semihydrogenation.

The study investigates the relationship of the reverse-pulse electrodeposited zinc-nickel alloy coatings’ characteristics and their corrosion behaviors in a saline environment, using both anodic polarization and electrochemical impedance analysis. The introduction of anodic pulsation gives deposits of more refined grain sizes and increased nickel contents, resulting in improvement of the corrosion resistance. High anodic current densities employed in the reverse-pulse electrodeposition, however, modulate crystallographic orientations of the grains, introduce porosity to the structure, and hence adversely affect the corrosion resistance of the coating deposits.

Galvanized coatings, commonly used for corrosion protection of steels' surfaces, are susceptible to crack formation and propagation due to thermal stress and deformation from post-processing. To identify geometrical parameters governing crack propagation of the coating layers, mechanics of crack propagation is numerically analyzed using finite element simulations. Focuses are given to addressing the influence of the coating thickness on fracture resistance of the zinc–iron intermetallic layers of galvanized coatings that are subjected to four-point bending. The study demonstrates that a decrease of the delta phase layer with respect to the zeta phase layer improves crack resistance of the coating layers. Furthermore, increasing the thickness of eta phase layer is shown useful for retarding crack growth in the intermetallic layers. Galvanizing protocols may be tailored to achieve a combination of intermetallic layer thicknesses that enhances the coatings' crack resistance.