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RISS 인기검색어
- 검색키워드
- 저자 : M. Sarkari (검색결과 2 건)
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Post Deformation at Room and Cryogenic Temperature Cooling Media on Severely Deformed 1050-Aluminum
M. Sarkari Khorrami,M. Kazeminezhad 대한금속·재료학회 2018 METALS AND MATERIALS International Vol.24 No.2
The annealed 1050-aluminum sheets were initially subjected to the severe plastic deformation through two passes of constrainedgroove pressing (CGP) process. The obtained specimens were post-deformed by friction stir processing at roomand cryogenic temperature cooling media. The microstructure evolutions during mentioned processes in terms of grainstructure, misorientation distribution, and grain orientation spread (GOS) were characterized using electron backscattereddiffraction. The annealed sample contained a large number of “recrystallized” grains and relatively large fraction (78%) ofhigh-angle grain boundaries (HAGBs). When CGP process was applied on the annealed specimen, the elongated grainswith interior substructure were developed, which was responsible for the formation of 80% low-angle grain boundaries. TheGOS map of the severely deformed specimen manifested the formation of 43% “distorted” and 51% “substructured” grains. The post deformation of severely deformed aluminum at room temperature led to the increase in the fraction of HAGBsfrom 20 to 60%. Also, it gave rise to the formation of “recrystallized” grains with the average size of 13 μm, which werecoarser than the grains predicted by Zener–Hollomon parameter. This was attributed to the occurrence of appreciable graingrowth during post deformation. In the case of post deformation at cryogenic temperature cooling medium, the grain sizewas decreased, which was in well agreement with the predicted grain size. The cumulative distribution of misorientationwas the same for both processing routes. Mechanical properties characterizations in terms of nano-indentation and tensiletests revealed that the post deformation process led to the reduction in hardness, yield stress, and ultimate tensile strengthof the severely deformed aluminum.
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Kinetic study of Fischer–Tropsch process on titania-supported cobalt–manganese catalyst
H. Atashi,F. Siami,A.A. Mirzaei,M. Sarkari 한국공업화학회 2010 Journal of Industrial and Engineering Chemistry Vol.16 No.6
An active cobalt–manganese catalyst was prepared by co-precipitation method, and was also tested for hydrogenation of carbon monoxide to light olefins. The catalyst was characterized using X-ray diffraction (XRD), scanning electron microscopy (SEM) and Brunauer–Emmett–Teller (BET) surface area techniques. The kinetic experiments on a well-characterized Co–Mn/TiO2 catalyst were performed in a fixed-bed micro-reactor, and were also conducted in a temperature range of 190–280 8C, pressure range of 1–10 bar, H2/CO feed ratio (mol/mol) range of 1–3 and a space velocity range of 2700–5200 h1. Two kinetic expressions based on Langmuir–Hinshelwood–Houngen–Watson (LHHW) mechanism were observed to fit the experimental data accurately for Fischer–Tropsch synthesis reaction. The kinetic parameters were estimated with non-linear regression method. Activation energies obtained were 35.131 and 44.613 kJ/mol for optimal kinetics models.
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