Material science
mojtaba forghani; Maedeh sadat Zoei; Mohammad Reza Pakmanesh; mohammad chiani; Saeed Asghari
Abstract
The sandwich panel is an important element of the satellite structure which various metal and composite materials are used to make its faces. Anodizing is used as a conversion coating in order to achieve the final properties of the panel surface and stability in the space environment. Anodizing is an ...
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The sandwich panel is an important element of the satellite structure which various metal and composite materials are used to make its faces. Anodizing is used as a conversion coating in order to achieve the final properties of the panel surface and stability in the space environment. Anodizing is an electrochemical process in which an oxide layer is formed using electricity. During the anodizing process, concentration polarization is created and the process is stopped when the limiting current resulting from the movement of electrical charges between the surface of the anodic layer and the electrolyte is increased. By stopping the process without spending enough time to obtain a thickness sufficient for colorability, a black anodic layer for use in space coatings is not obtained. In this research, by performing the anodizing process in four container of 250, 500, 2000 and 40000 cm3, the effect of the volume of the electrolyte on the wear and corrosion and optical-thermal properties of the layer obtained in each of the processes was investigated. The results showed that with the increase in the volume of the electrolyte caused by the increase in the volume of the container, the stopping time of the process increases. The evaluation of optical-thermal properties, wear resistance and corrosion resistance was done by infrared emission coefficient and solar absorption test, pin on disk test and salt spray test, respectively. The results of measuring optical-thermal and wear and corrosion properties for three container with volume of 500, 2000 and 40000 cm3 showed that with the increase in the volume of electrolyte and the process completion time of the process, the thickness of the anodic layer increased, which improved the optical-thermal properties, corrosion and wear resistance.
Material science
Maedeh sadat Zoei; S. Javid Mirahmadi; Mojtaba Forghani; mohammad chiani; Saeed Asghari
Abstract
Thermal barrier coatings (TBCs), are advanced ceramic systems that are usually applied to the surface of hot industrial parts to improve equipment performance at higher temperatures. During each thermal cycle, due to the mismatch in the coefficients of thermal expansion of TBC layers, these layers expand ...
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Thermal barrier coatings (TBCs), are advanced ceramic systems that are usually applied to the surface of hot industrial parts to improve equipment performance at higher temperatures. During each thermal cycle, due to the mismatch in the coefficients of thermal expansion of TBC layers, these layers expand and contract unbalanced. The resulting thermal stresses cause the nucleation and growth of microcracks in the TBC system. After several hundreds of thermal cycles, the microcracks eventually combine and form a relatively large crack that causes spallation and separation of the coating, exposing the parts to high temperatures and ultimately leading to catastrophic failure of the entire equipment. The creation of self-healing capability provides the ability to repair cracks spontaneously. In this article, various types of technologies for achieving self-healing in YSZ thermal barrier coatings and the structure and properties of the resulting coatings have been introduced and reviewed. After extracting the technologies of applying self-healing thermal barrier coating and comparing them with each other, it is possible to obtain coatings with self-healing properties according to the needs of each industry and then determined the proper composition of the self-healing coating, the proper thickness of the self-healing coating layer, the proper arrangement of the self-healing coating layer and the parameters of the coating process
