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31 results on '"SalimiJazi, H. R."'

8. Mechanical, corrosion, and tribocorrosion behavior of biomedical ZrO2 ceramic coatings prepared by thermal oxidation.

Author

Sourani, F., Raeissi, K., Enayati, M. H., Chu, Paul K., and SalimiJazi, H. R.

Subjects
TRIBO-corrosion, CERAMIC coating, KNEE joint, RAMAN spectroscopy, SALINE solutions, X-ray diffraction
Abstract

For the simultaneous improvement of mechanical, corrosion, and tribo-corrosion properties of Zr–2.5Nb alloy, an adherent black coating was deposited on the Zr–2.5Nb substrate by thermal oxidation in air at different temperatures and times to use in biomedical applications such as knee joints and orthopedic/dental replacements. According to obtained results, the long-term corrosion and tribo-corrosion resistance, and frictional properties in the phosphate-buffered saline solution improved significantly by oxidization at 523 °C for 4 h compared to the bare substrate. XRD patterns and Raman spectra revealed the formation of monoclinic and tetragonal ZrO2, as well as Nb2O5 phases in the black coating. According to microstructural studies, high adherence between the compact oxide layer and substrate decreased due to the formation of micro-cracks in the coating at a high operating temperature of 700 °C. [ABSTRACT FROM AUTHOR]

Published
2023
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19. Synthesis and Characterization of Mechanical Behavior and Thermal Shock Resistance of Macro-Porous SiC Solar Absorber.

Author

Parvanian, A. M., Salimijazi, H. R., and Fathi, M. H.

Subjects
THERMAL shock, THERMAL resistance, RENEWABLE energy sources, SOLAR receivers, SOLAR energy, SOLAR radiation
Abstract

The concentrated solar power (CSP) is one of the renewable energy sources in which solar irradiation heat energy will be used in a steam turbine to generate electrical grid. Solar radiation is absorbed by a solar receiver reactor on the surface of a porous solar absorber. In this survey, synthesis and mechanical/thermal characterization of micro-porous silicon carbide (SiC) absorber to be used in solar reactor is carried out. SiC foams were synthesized and categorized based on three different pore sizes i.e. 5, 12 and 75 ppi. Mechanical behavior and thermal shock resistance of porous foams in the working temperature range for absorber (25-1200 °C) were evaluated. Results revealed that the specific compressive strength (σc/ρ) of foams increase exponentially by a decrement in the porosity percentage and the average pore size. Moreover, for foams with smaller pore size, a considerable decrease in mechanical strength due to thermal shock was observed. This could be due to increase in the number of struts per unit volume i.e. more weak struts to withstand the mechanical loading. So, porous foams with coarser pore sizes were distinguished to be more capable of tolerating thermal shock while serving as solar absorbers. [ABSTRACT FROM AUTHOR]

Published
2020
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28. Characterization of vacuum plasma sprayed boron carbide

Author

Salimijazi, H. R., Coyle, T. W., Javad Mostaghimi, and Leblanc, L.

Abstract

Boron carbide has been successfully deposited on Ti alloy by vacuum plasma spraying (VPS). Mechanical properties of the deposited structure were assessed by micro-hardness and nano-hardness indentation. Chemical and phase compositions of the starting powder and the as-sprayed structure were characterized using hot gas extraction (LECO), x-ray diffraction (XRD), x-ray photoelectron spectroscopy (XPS), scanning transmission electron microscopy (STEM), and Raman spectroscopy. The microstructure consisted of equiaxed boron carbide grains, microcrystalline boron carbide particles, and amorphous carbon regions at the grain boundaries. The amount of boron oxide and amorphous carbon increased during spraying. Carbon segregation to grain boundaries in the as-deposited B4C was observed. The measured micro-hardness was slightly higher than values previously reported (1033 ± 2009 HV). There was significant variation of nano-hardness from point to point in the material due to the existence of multiple phases, splat boundaries, and porosity in the deposited structure.

30. Characterization of yttria coatings synthesized by conventional DC plasma spray and a novel plasma torch

Author

Saeidfar, M., Salimijazi, H. R., Emadi, R., Javad Mostaghimi, Pershin, L., and Coyle, T. W.

Abstract

Yttrium oxide (Y2O3) can be used in different applications such as corrosion resistance, high temperature applications and semi-conductor production equipment due to its very high thermal and chemical stability. In the current research, yttria coatings were processed using a new type of DC plasma gun consisted of molecular gases CO2+CH4. Physical and structural properties were compared with the coating made by SG-100 plasma torch. Gas mixture of CO2+CH4 improves the torch efficiency due to its high thermal enthalpy and conductivity which leads to increased particle temperature and complete fusion of the sprayed particles during the process of coating. SEM study of the structure revealed that the coating has higher density and lower porosity compared to the coating produced by SG-100 torch. No unmelted particles can be observed in the coating. XRD analysis of the coating showed that the coating contains no amount of harmful metastable monoclinic phases. This all proves the better quality of the coatings deposited by CO2+CH4 gas mixture in comparison to the conventional coatings.

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