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Showing 2 results for Electrodeposition
Amir Mirza Gheitaghy, Hamid Saffari, Jafar Salehi,
Volume 15, Issue 12 (2-2016)
Abstract
Boiling is a remarkably efficient heat transfer method and is commonly used in daily life and industrial applications. Changing the physical and chemical structure of hot surface in some methods as making a porosity in a manner of enhancing boiling process is an interesting topic in recent decay. In this paper, porous metal micro/nano structural surfaces is produced in order to augmentation of boiling heat transfer on copper surface by the one- and two-stage electrodeposition method. The pictures in micro and nanoscale are captured to identification of structure and surface characteristics as porosity and capillarity are estimated. Next, the effects of structures in enhancing the pool boiling are measured experimentally. So then, boiling heat transfer profiles that demonstrate heat flux versus wall superheat, are derived for water fluid. Pool boiling curves of enhanced surfaces is compared with polished surface and results of other researchers to determine the efficiency improvement. Furthermore, comparison the effect of electrodeposition process time on obtained structures shows higher porosity, capillary and strength of structure with lower process time (30 sec) lead to further enhancement of pool boiling.
H.r. Jashnani , M.r. Rahimi, A. Karimzadeh , M. Ettelaei ,
Volume 19, Issue 2 (2-2019)
Abstract
The properties such as weak wear resistance and low hardness of aluminum alloys have limited their use in various industries. In this research, it has been attempted to improve the mechanical and tribological properties of these materials by deposition of nickel-phosphorous-alumina functionally graded coating. Functionally graded coatings have been produced by a gradual change in the chemical composition and content of the nanoparticle, using continuous change in pulse parameters such as duty cycle and frequency during the coating process. So, the effect of the duty cycle and frequency has been investigated. Two types of coatings have been created with a gradual decrease in the duty cycle of 90% to 30% and a pulse frequency of 50 to 500 Hz. The result shows that the effect of frequency on the amount of phosphorus and nanoparticles is negligible, and it has mainly affected on grain size. However, in nanocomposite coats, the gradual decrease of duty cycle has led to an increase in the amount of phosphorus (5.3% to 15.5 wt. %) and alumina nanoparticles (0.7% to 2.6 wt. %) from the substrate to the top surface. With the gradual changes in chemical and microstructure, the adhesion of the coating to the substrate has improved. The results of micro-hardness have also shown that the creation of functionally graded coatings using duty cycle variation has a higher hardness than the one produced by frequency changing. Also, based on the results of the pin test on a disk against abrasive steel 52100, the wear resistance of functionally graded coatings has improved compared to single-layer coatings.
