فصلنامه علوم و مهندسی سطح ایران
پیاپی 19 (زمستان 1392)

In this study, friction stir processing (FSP) was utilized tofabrcation Fe based nano structure Fe48Cr18Mo7Nb6C4B16Y1 particles. For this reason, wc cone shape tool and constant tool rotation rate and travel speed 800 rpm and 100mm/min was used respectively. Microstructural, tribological properties and hardness has been studied. The results show that the hardness was increased by The presence of reinforcing particles and improved microstructural by FSP. The study of wear behavior shows that wear resistance was increased then steel base. Also investigation of wear surface showed that The dominant wear mechanism in the not reinforcement steel is lamination wear that with composite fabrication it to become abrasive wear.

In this research, alumina particles within Ni-P electroless coating were co-deposited on mild carbon steel substrate. The structure of the coatings was investigated by X-Ray Diffraction (XRD) analysis and the particles content in Ni-P-Al2O3 coating was determined by image analysis software and using the micrographs obtained by Scanning Electron Microscopy (SEM). The tribological behavior of the coatings was evaluated by pin-on-disc method and by using 52100 steel pins. Potentiodynamic polarization and Electrochemical Impedance Spectroscopy (EIS) methods were also used to study the corrosion behavior of the coatings in 3.5wt.%NaCl solution. The results showed that the hardness and wear resistance have increased with raising the alumina particles in nanostructure Ni-P-Al2O3 composite coating, whereas the corrosion resistance has decreased due to the activation of pitting corrosion.

Electrodeposition of Ni-Co alloy coatings was carried out in the modified Watts bath using different electrolytes by sediment co-deposition (SCD) technique in order to investigate the influence of saccharin and nano-SiC particles on the coatings. Surface morphology, chemical composition, phase composition, microhardness and corrosion resistance of coatings were studied using SEM, EDX, XRD, microhardness and polarization measurements. Results indicated that using different electrolytes led to changing the surface morphologies of coatings. Electrodeposition in the electrolyte containing saccharin led to varying the preferred orientation of coatings from (111) to (200) compared to Ni-45Co alloy and Ni-Co/SiC nanocomposite coatings. Moreover, Ni-Co/SiC nanocomposite coatings exhibited higher microhardness and corrosion resistance than pure Ni, Ni/Sa (Ni-Saccharin), Ni/SiC, Ni-45Co and Ni-Co/Sa (Ni-Co/Saccharin) coatings. Microhardness of Ni-Co alloy coatings was increased by increasing cobalt content in the coatings. The maximum microhardness value (615 HV) was obtained for nanocomposite coatings electrodeposited at current density of 3A/dm2. The observed properties were discussed based on the structural details.

Composite electroplating is a method for simultaneous plating of small ceramic particles in the plated metallic layer, in order to develop the morphology and mechanical properties. The electroplating method possesses many advantages such as low first cost, high speed of production, the possibility scaling up to industrial technologies and low service temperature. In this study, production of nano structural metal matrix composite "Ni-Fe(Ti,W)C" is investigated by electroplating method and the effect of important parameters such as substrate material and current density on coating properties, is evaluated. For this purpose, nickel bath was used under the condition of direct current. Based on the obtained results from characterizing the coating by X-ray diffraction (XRD), Scanning electron microscopy (SEM) and Energy Dispersive X-ray spectroscopy (EDS), it was recognized that nano structure composite Ni-Fe(Ti,W)C is producible and the steel substrate is appropriate than brass substrate with magnetic Ni-Fe matrix for electroplating of double carbid. Also with improvement of current density, surface morphology was more HV and the grain size was decreased to 27 nm smooth, the microhardness was increased to 1750.

In recent years, the highly conductive patterned fabric has been field of interest for many researchers by focusing on medical and electrical application of flexible and wearable electronic devices. In the meantime, inkjet printing technology as a high precision technique has been extensively successful in flexible electronic device industry. Compared to other techniques, the ink jet printing is most preferred due to low process time, expenses, waste material and also its great capability for creation of flexible conductive pattern. In current study, the polyester fabric was employed for temperature and pH optimization in nickel electroless plating process. The fabrication process composed of three steps including the etching, activation and electroless plating. The etching process provides necessary condition for inkjet printing in activation step followed by electroless plating. The formation of a multi cavity structure on PET fabric after etching process and a continues metallic phase composed of nickel nano crystals(20-100nm) after plating process are two major finding from AFM, SEM and optical microscopic images. The four probe conductivity measurements showed a range of conductivity around 2632± 35 S/cm. Range of patterns including spiral or flat panels with applications in antenna and sensors show the technique perfection. The capacitance measurements also represent a range between 10-20 nF.

In the current study, (Ti, Cr)N coatings were deposited on the D6 tool steel substrates. Physical and mechanical properties of coatings such as microstructure, thickness, phase composition and hardness were evaluated. The friction and wear behavior of the coatings were investigated using ball-on-disc test under normal loads of 5, 7 and 9 N at sliding distance of 500 m, at room temperature. Phase compositions were studies by X-ray diffraction method. Mechanical properties were determined by nano-indentation technique. Scanning electron microscope and energy dispersive spectroscopy were utilized to investigate the microstructures and wear mechanisms. The results clarified that the wear resistance of (Ti, Cr)N and TiN coatings were better than CrN coating. Wear resistance of the Cr-Ti-N coatings was related to Ti content and increased with increasing Ti content. The dominant wear mechanisms were characterized to be abrasive and tribochemical.

Highly ordered anodic TiO2 nanotube arrays have attracted great attention due to fast electron transport and high surface - to - volume ratio. In this work, firstly, the effect of different surface characteristics on the structure, tube morphology and ordering of titanium oxide nanoporous films were investigated and then highly ordered anodic TiO2 nanotube arrays were produced by two-step anodic oxidation. Current transients were recorded during the potentiostatic anodization. Morphology of the TiO2 nanotube arrays were studied using field emission scanning electron microscopy (FESEM) and atomic force microscopy (AFM). We found that anodic oxidation of titanium after electropolishing produces the most homogeneous TiO2 nanotubes with a high ordering degree across the surface. FESEM images show that TiO2 nanotube formed on electropolishing surfaces exhibits a smooth surface at the top of the grown film. By contrast, TiO2 nanotube formed on mechanical polishing surfaces exhibits a rough top surface and different tube sizes. As a results, The requisites for the fabrication of extremely regular arrays of valve metal oxide nanotubes are the electropolishing of the valve metal and a two-step anodization process.

In this paper successive method involving laser ablation followed by autocatalytic reduction has been developed for fabrication of Pd-MoO3-x. First molybdenum oxide nanoparticles were prepared by laser ablation in H2O or H2O2 liquid using excimer (KrF, λ=248 nm) or solid state (Nd:YAG, λ=1064 nm) lasers. Then PdCl2 solution with different concentrations were added to the colloidal solution with the hope palladium nanoparticles are deposited upon the initial nanoparticles. The effect of laser wavelength on palladium solution and ablation environment were studied by means of Transmission Electron Microscopy (TEM), UV-Vis spectrophotometry and Atomic Force Microscopy (AFM).

In this study, the formation ElectrolessNi-P coating on AZ31 Mg alloy by commercial bath SLOTONIP70 wasinvestigated. In this regard bath condition was determined and the effect of surface preparation parameter on properties of coating was studied. The time and required amount of acid hydrofluoric was introduced.After coating in optimum conditions, X-Ray analysis, Scanning Electron Microscopy (SEM) and Energy Dispersive spectroscope (EDS) were used to characterize the coatings.The result showed that Sand blast process before coating was necessary stage to inhibit crack formation in the coatings. The optimum condition for coating was 35wt% HF, pH 6/4 and the temperature 80°C. In these conditions the crystallized cauliflower-like structurecoating content about 3-4wt% of phosphorus was obtained.