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Abstract In vacuum infiltration of Ni-based self-fluxing alloy (NiCrBSi) cladding, reinforced with ultrafine WC particles with average particle size (APS) of 0.2–0.4 μm, several plate-like anomalous WC grains were observed with size of greater than 20 μm. To prevent this anomalous grain growth, Cu shells were coated on WC particles. The very low solid state solubility of WC in copper phase at high temperature can lead to no anomalous WC grain growth. Cu shell with a thickness about 30–50 nm was deposited by means of electroless plating on ultrafine WC particles. The microstructural features of Cu-coated carbides and the resultant brazed claddings were characterized by field emission scanning electron microscopy (FESEM) equipped with energy dispersive X-ray spectroscopy (EDS). The evaluation of the brazed cladding revealed a thick ultrafine grained-microstructure with homogeneous grain size distribution, in contrast to the bare WC-based cermet cladding. The hardness of this novel composite cladding was nearly increased up to 1500 HV, which was 40% more than that of the un-coated WC reinforced cladding. The results demonstrated that the resistance against crack initiation and propagation considerably improved by using Cu-coated WC particles in the sintered media. Highlights • To prevent anomalous WC grain growth in Ni based cladding, Cu shell was coated on WC particles by electroless deposition. • The very low solid state solubility of WC in copper phase at high temperature led to no anomalous WC grain growth. • A fine microstructure with homogeneous grain size distribution was obtained in Cu-coated WC reinforced Ni based cladding. • The hardness of this cladding was increased up to 1500 HV, 40% more than that of uncoated WC reinforced Ni base cladding. • The resistance against crack initiation and propagation was considerably improved in Cu-coated WC reinforced Ni based cladding. [ABSTRACT FROM AUTHOR]

Abstract In this study, a novel Ni-P-coated WC/NiCrBSi composite cladding was prepared on a carbon steel substrate through high-temperature vacuum brazing technique with the aim of improving the wear properties of the surface. In order to improve the wettability of WC particles by a liquid phase (NiCrBSi alloy), Ni-P layer was deposited on carbide particles by electroless plating. This layer assisted to fabricate a thick coating with very low porosity, improving adhesion strength between ceramic particles and the matrix. The morphology, crystal structure and microstructure of coated carbides and the resultant composite cladding were characterized by field emission scanning electron microscopy (FESEM) equipped with energy dispersive X-ray spectroscopy (EDS), and X-ray diffraction (XRD) analysis. Thin electroless plated Ni-P shell with a thickness about 50–150 nm, were coated on WC particles. In the claddings, a uniform and homogenous distribution of WC particles in Ni-based matrix was observed. The pin on disk wear test was carried out to investigate the wear behavior of the fabricated cladding reinforced with and without Ni-P coated WC particles. The results indicated that the resistance against crack initiation and propagation significantly improved by using Ni-P layer in the sintered cladding. This cladding exhibited very low wear weight loss than conventional brazed cladding. Highlights • A thick brazed coating was performed by core-shell powder (ultrafine WC@NiP) and Ni-based alloy as an infiltrant material. • Ni-P shell layer on WC particles improved the adhesion of particles to the Ni-based brazing alloy. • The remaining pore space value was decreased by using WC@NiP, resulting in increased the wear resistance. • The cracking susceptibility was decreased for Ni-based brazed cladding reinforced with Ni-P coated WC particles. [ABSTRACT FROM AUTHOR]

NiGa alloy nanowires were electrodeposited from an acidic sulfate bath into nanoporous anodized alumina oxide (AAO). This template was fabricated by two-step anodizing. The effects of bath composition and current density were explored on the Ga content of electrodeposited nanowires. The Ga content in the deposits was increased by increasing both Ga in the bath composition and electrodepositing current density. The NiGa alloy nanowires were synthesized for Ga content up to 2–4% without significant improving the magnetic properties. Above this threshold Ga clusters were formed and decreased the magnetic properties of the nanowires. For Ga content of the alloy above 30%, the wires were too short and incomplete. X-ray diffraction patterns reveal that the significant increase of Ga content in the nanowires, changes the FCC crystal structure of Ni to an amorphous phase. It also causes a sizeable increase in the Ga cluster size; these both lead to a significant reduction in the coercivity and the magnetization respectively. [ABSTRACT FROM AUTHOR]

• The Ni-Cu foam was decorated with Pd nanoparticles by galvanic replacement method. • The Tafel slope of Ni-Cu/Pd is 72 mV dec−1 which is 94 mV dec−1 less than substrate. • The fractal architecture of Ni-Cu/Pd provided a high surface area (112.5 cm2). • Ni-Cu/Pd requires 134 mV overpotential at the current density of 10 mA cm−2. Fractal Ni-Cu foam with palladium nanoparticles on (Ni-Cu foam / Pd) was prepared by electrodeposition and galvanic replacement method. The results showed that after the fabrication of Pd particles on Ni-Cu foam, the hydrogen evolution reaction (HER) activity of the electrode improved dramatically. The morphology and phase structure of deposited layers were studied by field emission scanning electron microscopy, and X-ray diffraction methods, respectively. In order to investigate the morphology of the coatings in more details, transmission electron microscope was used, which its figures authenticated the presence of Pd nanoparticles on the fractal structures of Ni-Cu. Based on the electrochemical tests in KOH (1.0 M), the Ni-Cu foam / Pd electrode has good electrocatalytic properties, with a low overpotential of 134 mV at 10 mA cm−2 and Tafel slope of 72 mV dec−1. Cyclic voltammetry measurements showed that the Ni-Cu foam/Pd possesses a high electrochemical surface area of 112.5 cm2 that was attributed to the presence of both fractal Ni-Cu foam and Pd nanoparticles. Overall, this study proposes a feasible approach for the fabrication of a highly-porous, super hydrophilic, and scalable electrode with a great performance toward HER. [ABSTRACT FROM AUTHOR]

Abstract: This paper presents the results of milling time on the structure and properties of obtained stainless steel/30%TiC nanocomposite prepared by planetary milling in argon atmosphere using stainless steel 316 and titanium carbide powders. Achievement of a fine distribution of TiC nanoparticles in the steel matrix was the main purpose of this study. The results showed that increasing of the milling time up to 40h led to good distribution and grain refinement of nanocomposite powder. The microstructure evolution of milled powders and nanocomposite were investigated by Scanning Electron Microscopy (SEM), X-ray Diffraction (XRD), Transmission Electron Microscopy (TEM) and optical microscopy. TEM image revealed clearly that TiC nanoparticles with grain size of 50nm were distributed in steel matrix at milling time of 40h. The maximum hardness and density were 67 HRC and 6.63g/cm3, respectively, when the sample was pressed under 550MPa pressure and sintered at 1400°C. [Copyright &y& Elsevier]

Abstract: NiMn alloys were electrodeposited from chloride bath with various Mn content up to 10 at.%. The effect of bath composition and current density on Mn content of electrodeposited thin films was explored. A maximum of 9.8 at.% Mn content in deposited films was obtained at optimized current density of 40 mA/cm2 and MnCl2/NiCl2 concentration ratio of 2.5 in the bath. The morphology and crystal structure of deposits were evaluated by scanning electron microscopy (SEM) and X-ray diffraction (XRD). The constituents in the films were determined by energy dispersive X-ray spectroscopy (EDS). It was revealed that the structure of NiMn coatings had an average grain size of about 17 nm. It was found that the deposits exhibited FCC structure with prefer orientation of <111>. The soft magnetic properties of electrodeposited films were measured by vibrating sample magnetometer (VSM). It was observed that the magnetic parameters such as coercivity and saturation magnetization were decreased with increasing of Mn in the deposits. [Copyright &y& Elsevier]

Abstract: In this study, TiO2−x N x /TiO2 double layers thin film was deposited on ZnO (80nm thickness)/soda–lime glass substrate by a dc reactive magnetron sputtering. The TiO2 film was deposited under different total gas pressures of 1Pa, 2Pa, and 4Pa with constant oxygen flow rate of 0.8sccm. Then, the deposition was continued with various nitrogen flow rates of 0.4, 0.8, and 1.2sccm in constant total gas pressure of 4Pa. Post annealing was performed on as-deposited films at various annealing temperatures of 400, 500, and 600°C in air atmosphere to achieve films crystallinity. The structure and morphology of deposited films were evaluated by X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM), and atomic force microscopy (AFM). The chemical composition of top layer doped by nitrogen was evaluated by X-ray photoelectron spectroscopy (XPS). Photocatalytic activity of samples was measured by degradation of Methylene Blue (MB) dye. The optical transmittance of the multilayer film was also measured using ultraviolet–visible light (UV–vis) spectrophotometer. The results showed that by nitrogen doping of a fraction (∼1/5) of TiO2 film thickness, the optical transmittance of TiO2−x N x /TiO2 film was compared with TiO2 thin film. Deposited films showed also good photocatalytic and hydrophilicity activity at visible light. [Copyright &y& Elsevier]

Abstract: Titanium oxide thin films were deposited by DC reactive magnetron sputtering on ZnO (80 nm thickness)/soda-lime glass and SiO2 substrates at different gas pressures. The post annealing on the deposited films was performed at 400 °C in air atmosphere. The results of X-ray diffraction (XRD) showed that the films had anatase phase after annealing at 400 °C. The structure and morphology of deposited layers were evaluated by scanning electron microscopy (SEM) and atomic force microscopy (AFM). The surface grain size and roughness of TiO2 thin films after annealing were around 10–15 nm and 2–8 nm, respectively. The optical transmittance of the films was measured using ultraviolet–visible light (UV–vis) spectrophotometer and photocatalytic activities of the samples were evaluated by the degradation of Methylene Blue (MB) dye. Using ZnO thin film as buffer layer, the photocatalytic properties of TiO2 films were improved. [ABSTRACT FROM AUTHOR]

Abstract: Shape memory NiTi-based thin films approximately 2μm thick were deposited onto Si (100) substrates at room temperature by simultaneous DC magnetron sputter deposition from separate elemental Ni and Ti targets. The effect of composition on film structure, surface morphology, transformation temperature and mechanical behavior was studied using variable temperature X-ray diffraction, atomic force microscopy, electrical resistivity, and nanoindentation. The films showed the expected shape memory and superelasticity behavior corresponding to the different film compositions, comparable with bulk properties. The transformation from the low temperature martensitic phase to the high temperature parent phase takes place above room temperature in Ti-rich and near-equiatomic films, and below room temperature in Ni-rich films. Mechanical properties of films investigated at room temperature by a series of nanoindentations at mN loads (indentation depth<200nm) with a spherical indenter demonstrate superelasticity in Ni-rich material and martensitic deformation for Ti-rich and near-equiatomic compositions. [Copyright &y& Elsevier]

Abstract: Size-dependent thermodynamic parameters, such as Gibbs free energy, enthalpy and entropy, for the transition of a Ni nanofilm to catalyst particles for subsequent carbon nanotube growth have been explored. In this investigation, we consider the derived equations of the size-dependent melting temperature of nanosolids based on our previous works. Using this thermodynamic approach, it is found that the diameter of Ni particles is 3 times greater than the thickness of the original film. From the critical and stable sizes of transformed Ni nanoparticles, a minimum film thickness for transformation of film to nanoparticles was obtained. Our predictions are in good agreement with experimental results. [Copyright &y& Elsevier]

Abstract: High temperature shape memory NiTiHf thin films with varying hafnium contents up to 28.7at.% were fabricated by DC magnetron sputtering using simultaneous sputter deposition from separate elemental targets. The required film composition was achieved by adjusting the power ratio to the targets. The as-deposited films were amorphous; a post deposition annealing was performed at 550°C to crystallize the films. Two-micron thick films were characterized by energy dispersive spectroscopy in a scanning electron microscope, temperature controlled X-ray diffraction, differential scanning calorimetry, and atomic force microscopy. The results showed that above 10at.% Hf additions the transformation temperatures increased considerably over NiTi. The crystallization temperature of the films varied as a function of Hf concentration and was as high as 519.2°C, at Hf content of 28.7at.%. The R-phase transformation was observed during cooling at compositions less than 16at.% Hf. The transformation temperatures confirmed that the films are comparable with bulk NiTiHf alloy of similar composition. [Copyright &y& Elsevier]

In this study, electrophoretic deposition (EPD) was employed as a practical way to form porous structure of TiC-based layer. The porous medium was infiltrated successfully by a Ni-based melt phase at 1060 °C to fabricate Ni/TiC composite coatings. It was revealed that EPD parameters such as voltage affect the volume fraction of TiC particles in the sintered layer. It was indicated that electroless deposition of Ni-P shell on TiC core particles before EPD was necessary to enhance the melt penetration into the TiC porous matrix and hence to densify the porous medium. Microstructure and phase characterization were studied by field emission scanning electron microscopy (FE-SEM) and X-ray diffraction (XRD). The results showed that TiC particles were well distributed through a matrix composed of primary γ-Ni phase. The average hardness of the sintered composite coating was 1540 Vickers, which is sufficiently high to make them good candidates for wear resistance applications. [ABSTRACT FROM AUTHOR]

Abstract: The influence of sodium dodecyl sulfate (SDS) as anionic surfactant and cetyltrimethyl ammonium bromide (CTAB) as cationic surfactant on the morphology, composition, and texture and corrosion behavior of electrodeposited Co–TiO2 coatings was investigated. The polarization test revealed that the coatings deposited from SDS containing solution formed passive layer in low current densities and high positive voltages than coatings deposited in CTAB containing solution. The corrosion resistance of deposited coatings from SDS containing solution was improved in NaOH and H2SO4 solutions than CTAB one. The performed impedance test results in both corrosive media were compatible with the results of polarization test. The coatings deposited with CTAB had grains structure of 62nm whilst SDS ones showed finer grains around 45nm, which it was evaluated by XRD analysis and chronoamperometry extrapolation. [Copyright &y& Elsevier]

Abstract: We present a relation between the average coordination number and the cohesive energy for nanoparticles that shows that the ratio of nanoparticles cohesive energy to the bulk value is equal to the ratio of the nanoparticles average coordination number to that of the bulk. We consider the effect of lattice and surface packing factors on the average coordination numbers of the atoms in the nanoparticle. The melting temperature of nanoparticles has been calculated from the obtained relation for cohesive energy, and predictions for the cohesive energy and melting temperature of the nanoparticles have been compared with other theoretical models and available experimental data and the results of molecular dynamics simulations. [Copyright &y& Elsevier]

Abstract: A model has been developed to account for the dependence of melting temperature of nanoparticles on their size, shape and lattice type. This model is consistent with reported experimental data and shows better consistency than the liquid drop and bond energy model. A general equation is proposed which correlates with the bond energy model formula and has high potential for application in research and development. The model also leads to an equation showing the limiting size for nanoparticles. [Copyright &y& Elsevier]

Abstract: The main goal of this research was the characterization of the microstructure and texture of functionally graded nickel-Al2O3 nano composite coating. This coating was produced by changing the duty cycle under ultrasonic agitation during pulse deposition process. All of the electrodeposited layers were prepared at 20 A.dm−2 peak current density and constant frequency of 10Hz, and the duty cycle has been changed from 90% at the first layer to 10% at the fifth layer. According to SEM images and EBSD results, all layers except the last one showed a truncated pyramidal structure which is a typical morphology for Ni deposited coatings with [100] preferred texture. The last layer which was prepared at duty cycle of 10% exhibited a cauliflower (or colony) structure with small grains that probably resulted in random texture in this layer. EDS results showed more alumina particles can be incorporated at lower duty cycles. Foreign ions incorporation during the deposition process could be the reason for a change of [100] fiber texture to almost random orientation of grains. This rather high incorporation is due to either lower current density or higher OFF-Time duration at low duty cycles in pulse plating process. [Copyright &y& Elsevier]

Abstract: In this research, a modified, cost effective sol–gel procedure applied to synthesize BaTiO3 nanoparticles. XRD and electron microscopy (SEM and TEM) applied for microstructural characterization of powders. The obtained results showed that the type of precursors, their ratio and the hydrolysis conditions had a great effect on time, temperature and therefore the costs of the synthesis process. By selection, utilization of optimized precursor''s type, hydrolysis conditions, fine cubic BaTiO3 nanoparticles were synthesized at low temperature and in short time span (1h calcination at 800°C). The proposed procedure seems to be more preferable for mass production. The result indicated that the polymorphic transformation to tetragonal (ferroelectric characteristic) occurred at 900°C, which might be an indication of being nanosized. [Copyright &y& Elsevier]