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- De Colle, Mattia, et al.
(author)
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Study of the Hydration Behavior of Synthetic Ferropericlase with LowIron Oxide Concentrations to Prevent Swelling in Steel Slags
- 2021
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In: Journal of Sustainable Metallurgy. - : Springer Nature. - 2199-3831 .- 2199-3823.
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Journal article (peer-reviewed)abstract
- Steel slags generally swell when subjected to water or humidity, which prevents proper recycling in the cement or asphaltindustries. The MgO and CaO phases in steel slags are responsible for this phenomenon, as both minerals easily absorb waterto form their respective hydroxides. MgO is often present in steel slags in a solid solution with several oxides, constitutingthe so-called RO phase. This study investigates the hydration rate of an RO phase consisting of FeO and MgO called ferropericlase.The material was synthesized in a laboratory furnace by sintering a FeO–MgO powder mixture with varying initialFeO contents (approximately 10, 15, and 20 wt%). Thereafter, electron probe micro-analyzer (EPMA) and X-ray diffraction(XRD) spectroscopies were used to characterize the structure of the samples, which were mainly composed of ferropericlaseand an exsolution of magnesioferrite. Also, Mössbauer spectra showed that the total ferrous iron proportion (Fe2+/ΣFe) ofthe sintered samples was in the range of 0.55–0.72. To measure the hydration behavior, the samples in powder form werecured in an autoclave at an H2Opartial pressure of 2 atm. Thereafter, thermal gravimetric analysis (TGA) was performed tomeasure the amount of water absorbed during the autoclave curing from the mass drop associated with the dehydration ofthe hydroxide. The study found a linear correlation between the initial FeO content and the weight loss after TGA, with areduction down to 6% in the sample with an initial FeO content of 20 wt% content compared to pure MgO.
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| 2. |
- Wang, Wei, et al.
(author)
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Inclusion engineering in Co-based duplex entropic alloys
- 2021
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In: Materials & design. - : Elsevier BV. - 0264-1275 .- 1873-4197. ; 210
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Journal article (peer-reviewed)abstract
- Co-based duplex entropic alloy is designed very recently to replace pure Co as a major component of the binder phase for cemented carbide cutting tools. This work aims to provide a fundamental study of oxide inclusion characteristics in the duplex fcc + hcp Co-based entropic alloys. It is found that the Co85-xCrxFe7.5Ni7.5 (x = 15, 30 at.%) alloys hold the highest liquidus (T-liq) and solidus (T-sol) temperatures, compare with the Co85-xCrxMn7.5Ni7.5 (x = 15, 30 at.%) and Co77.5-xCrxFe7.5Mn7.5Ni7.5 (x = 15, 30 at.%) alloys. For each grade, the increasing Cr content leads to a decrease of T-sol and T-liq temperatures. It is also noted that there is an approximate 100 degrees C of undercooling exists in each grade during the solidification. The stable oxide inclusion in the Co85-xCrxMn7.5Ni7.5 and Co77.5-xCrxFe7.5Mn7.5Ni7.5 alloys is the MnCr2O4 type, while Cr2O3 is the main stable inclusion in the Co85-xCrxFe7.5Ni7.5 alloy. Furthermore, the size range of the MnCr2O4 particles is larger than that of Cr2O3. The theoretical calculation shows that MnCr2O4 has a higher coagulation coefficient than Cr2O3 does. This is due to the influence of the thermo-physical parameters, i.e. the interfacial energy between the oxide and the alloy and the viscosity of liquid alloy. The theoretical calculation fits well with the experimental findings.
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