IRANIAN JOURNAL OF SURFACE SCIENCE AND ENGINEERING
Year:2020 | Volume:- | Issue:43|Papers Count:6

The purpose of this study was the co-electrodeposition of boron carbide (B4C) hard particles and tungsten sulfide (WS2) lubricant particles on copper substrate and produce Ni-B4C-WS2 nanocomposite coatings. Hardness and tribological behavior of nanocomposite coatings were also investigated. Field emission electron microscopy (FESEM) was used to study the microstructure of coatings and hardness and tribological behavior, were evaluated by microhardness and pin-on-disk tests respectively. The results showed that hybrid nanocomposite coating is more fine-grained than other coatings, and have a better distribution of boron carbide and tungsten sulfide particles. The hardness of hybrid coating was obtained 461 vickers, which was much higher than that of the other two coatings. The lowest weight loss after wear test at slide distance of 800 m was obtained in 1 mg hybrid coating which was much lower than other two coatings. Also, the lowest friction coefficient for the hybrid coating was 0. 53.

In the present work, two-component heterostructure of ZnOnanorods array (ZnO NRs) and CuO nanostructure has been grown. Well-aligned ZnO NRs have been synthesized using seed layer by low temperature wet chemical method. Then, CuOthin film has been form by thermal oxidation ofCu thin film deposited by magnetron sputtering on ZnO NRs to increase and expand optical absorption to visible region. The structure, morphology and chemical, optical, photocatalytic properties of ZnO NRs/CuOheterostructures have been studied by, X-ray diffractometry (XRD), field emission-scanning electron microscope/ energy dispersive X-ray spectroscopy (FE-SEM /EDX), UV-Vis-near IR optical absorption spectroscopy, and current – voltage measurement, respectively. Thermal oxidation of Cu thin film on ZnO NRs in the temperature range 200-600 ° C Cause ZnO NRs/CuO TF heterostructure to form. The ZnO NRs/CuOheterostructures increase and expand optical absorbtion to visible range in comparision to bare ZnO NRs. Photocatalytic activity of ZnO NRs/CuOheterostructure was investigated through Rhodamine B (RhB) photodegrdation under UV-Vis irradiation. Photocatalytic efficiency of ZnO NRs/CuOheterostructure is considerably increased in comparison to bare ZnO NRs.

In this study, silica and carbon doped silica thin films were deposited on silicon substrates by plasma polymerization using capacitively coupled system in radio frequency. Organo-silicon TEOS vapor was used as a precursor for synthesizing the films which were mixed by specific flow rate of oxygen gas. In order to combine carbon elements into the silica films, acetylene gas was also added into the plasma gas mixture. The effect of acetylene gas flow rates on thickness and refractive index of the films was studied by spectroscopic ellipsometry. Furthermore, in order to investigate the films transparency, the optical absorption was also determined using the same analysis. Morphological investigation of the films using atomic force microscopy was shown that increasing acetylene into the plasma, causes to increase the surface roughness of the films from 0. 1 nm to 5. 3 nm. Furthermore, the results of optical analysis were shown that increasing acetylene concentration in the plasma led to increase the films refractive index from 1. 447 to 1. 485 as well as increase their optical absorption from 0. 8% to 9. 3%. Moreover, for adding carbon elements into the silica films and changing their properties, the effect of increasing acetylene flow rate was compared by decreasing oxygen flow rate.

In the current study, the Ge1-xCx coatings were deposited on silicon and glass substrates by a plasma enhanced chemical vapor deposition (PECVD) process with a gas mixture of GeH4 and CH4 as the precursors. In order to evaluate the environmental stability of the coatings, the salt fog test was used. Microstructural investigation and bonding characterization of coatings were performed using a field emission scanning electron microscope (FESEM) equipped with energy dispersive spectrometer (EDS) and X-ray photoelectron spectrometer (XPS), respectively. After 24 hours exposure to the salt fog, all of the germanium-carbon coatings are deposited under different conditions shows a very good stability; So that, there was no trace of detachment, peeling, cracking and blistering on the specimens. Scanning electron microscopic evaluations from the surface of the coatings also confirmed this. Only for the carbon-rich Ge1-xCx coatings, some parts of the edges of the coating were degraded. The mechanism of degradation of the coatings was described as blistering and crack development due to the influence of water molecules on the interface of the coating/substrate.

In this paper, effect of input parameters (pulse on time, pulse current, voltage and duty cycle) of electric discharge deposition process on surface quality parameters including surface hardness, surface deposited layer thickness and roughness of AISI H13 tool steel using Ti-Cr-Cu alloys as electrode was studied. SEM was used to investigate the thickness of the surface layer, and the hardness of surface deposited layer was measured by microhardness test. Also, XRD method was used to identify the compounds on the surface and deposited surface roughness was controlled using Ra parameter. Based on the obtained results, TiC, Cr7C3 and Fe2C are formed at the deposited layer due to surface alloying and increasing surface hardness. Also, by increasing the pulse current and the pulse on time, the surface hardness and depth of the deposited layer were increased. Furthermore, with increase in input voltage, the thickness of the surface layer is increased and the workpiece surface roughness is reduced. Also, by increasing the duty cycle due to the increase in the number of sparks in time, the depth of the surface deposited layer is increased.

Doping rare transition metals into Mn-Co spinel oxide (MCO) could improve conductivity and bonding of coated interconnects applied for solid oxide fuel cells. In the present study, Cux(Mn, Co)3-xO4 (x=0, 0. 2 and 0. 4) nanopowders were synthesized via sol-gel based Pechini method. Protective coatings of spinel compounds have been applied on SUS430 stainless steel interconnects by using electrophoretic deposition (EPD). The optimum condition of 1 min deposition time at 60 V was chosen according to the uniformity of coating microstructure. Kinetics of deposition was studied based on Baldisserri model at 60 V for Cu0. 2MCO and Cu0. 4MCO samples. The sintering of coated samples was carried out in two-steps under the both reducing and oxidizing atmospheres. The phase and microstructure of synthesized spinel nanopowders and coatings were characterized by X-ray diffraction (XRD) and field-emission scanning electron microscopy (FE-SEM) equipped with EDS. The results of non-isothermal area specific resistance (ASR) measurements in the temperature range of 550-800oC showed the minimum value of area specific resistance (ASR)=3. 2 mΩ cm2 and maximum activation energy of Ea=48. 2 kJ/mole were obtained for Cu0. 2MCO sample.