| 1. |
- Akhtar, Farid, et al.
(författare)
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Pressureless infiltration of Si3N4 preforms with an Al-2wt% Mg alloy
- 2005
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Ingår i: International Journal of Minerals, Metallurgy and Materials. - 1674-4799 .- 1869-103X. ; 12:4, s. 351-356
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Tidskriftsartikel (refereegranskat)abstract
- The pressureless infiltration process to synthesize a silicon nitride composite was investigated. An Al-2wt%Mg alloy was infiltrated into silicon nitride preforms in the atmosphere of nitrogen. It is possible to infiltrate the Al-2wt%Mg alloy in silicon nitride preforms. The growth of the composite with useful thickness wasfacilitated by the presence of magnesium powder at the interface and by flowing nitrogen. The microstructure of the Si3N4-Al composite has been characterized using scanning electron microscope.During the infiltration of Si3N4 preforms, Si3N4 reacted with aluminium to form silicon and AlN. Thesilicon produced during the growth consumed in the formation of MgSiAlO, MgSiAlN and Al3.27Si0.47 type phases. The growth of the composite was found to proceed in two ways, depending on the oxide content in the initial preforms. First, less oxide content preforms gave rise to MgAlSiO and MgAlSiN type phases after infiltration. Second, more oxide content preforms gave rise to AlN-Al2O3 solid solution phase(AlON). The AlON phase was only present in the composite, containing 10% aluminium in the silicon nitride preforms before infiltration.
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| 2. |
- Avazkonandeh-Gharavol, M. H., et al.
(författare)
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Effect of partition coefficient on microsegregation during solidification of aluminium alloys
- 2014
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Ingår i: International Journal of Minerals, Metallurgy and Materials. - : Springer Science and Business Media LLC. - 1674-4799 .- 1869-103X. ; 21:10, s. 980-989
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Tidskriftsartikel (refereegranskat)abstract
- In the modeling of microsegregation, the partition coefficient is usually calculated using data from the equilibrium phase diagrams. The aim of this study was to experimentally and theoretically analyze the partition coefficient in binary aluminum-copper alloys. The samples were analyzed by differential thermal analysis (DTA), which were melted and quenched from different temperatures during solidification. The mass fraction and composition of phases were measured by image processing and scanning electron microscopy (SEM) equipped with an energy-dispersive X-ray spectroscopy (EDS) unit. These data were used to calculate as the experimental partition coefficients with four different methods. The experimental and equilibrium partition coefficients were used to model the concentration profile in the primary phase. The modeling results show that the profiles calculated by the experimental partition coefficients are more consistent with the experimental profiles, compared to those calculated using the equilibrium partition coefficients.
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| 3. |
- Bahrami, Ataallah, et al.
(författare)
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Process mineralogy as a key factor affecting the flotation kinetics of copper sulfide minerals
- 2019
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Ingår i: International Journal of Minerals, Metallurgy and Materials. - : Springer. - 1674-4799 .- 1869-103X. ; 26:4, s. 430-439
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Tidskriftsartikel (refereegranskat)abstract
- The aim of this study is to apply process mineralogy as a practical tool for further understanding and predicting the flotation kinetics of the copper sulfide minerals. The minerals’ composition and association, grain distribution, and liberation within the ore samples were analyzed in the feed, concentrate, and the tailings of the flotation processes with two pulp densities of 25wt% and 30wt%. The major copper-bearing minerals identified by microscopic analysis of the concentrate samples included chalcopyrite (56.2wt%), chalcocite (29.1wt%), covellite (6.4wt%), and bornite (4.7wt%). Pyrite was the main sulfide gangue mineral (3.6wt%) in the concentrates. A 95% degree of liberation with d80 > 80 µm was obtained for chalcopyrite as the main copper mineral in the ore sample. The recovery rate and the grade in the concentrates were enhanced with increasing chalcopyrite particle size. Chalcopyrite particles with a d80 of approximately 100 µm were recovered at the early stages of the flotation process. The kinetic studies showed that the kinetic second-order rectangular distribution model perfectly fit the flotation test data. Characterization of the kinetic parameters indicated that the optimum granulation distribution range for achieving a maximum flotation rate for chalcopyrite particles was between the sizes 50 and 55 µm.
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| 4. |
- Chatterjee, Ritayan, et al.
(författare)
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Structural, microstructural, and thermal characterizations of a chalcopyrite concentrate from the Singhbhum shear zone, India
- 2015
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Ingår i: International Journal of Minerals, Metallurgy and Materials. - : Springer Science and Business Media LLC. - 1869-103X .- 1674-4799. ; 22:3, s. 225-232
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Tidskriftsartikel (refereegranskat)abstract
- The structural and morphological characterizations of a chalcopyrite concentrate, collected from the Indian Copper Complex, Ghatshila, India, were carried out by X-ray diffraction, scanning electron microscopy, and energy-dispersive X-ray spectroscopy. The concentrate powder was composed mainly of free chalcopyrite and low quartz in about 3:1 weight ratio. The particle size was about 100 mu m. Spectroscopic studies (FTIR, Raman, UV-visible) of the concentrate supported the XRD findings, and also revealed a marginal oxidation of the sulfide phase. The energy band gap of the sulfide was found to be 3.4 eV. Differential thermal analysis and thermogravimetry of the concentrate showed a decomposition of chalcopyrite at 658 K with an activation energy of 208 kJ center dot mol(-1), and two successive structural changes of silica at 848 K and 1145 K.
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| 5. |
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| 6. |
- Duan, Shengchao, et al.
(författare)
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Evolution of nonmetallic inclusions in 80-t 9CrMoCoB large-scale ingots during electroslag remelting process
- 2024
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Ingår i: International Journal of Minerals, Metallurgy and Materials. - : University of Science and Technology Beijing. - 1674-4799 .- 1869-103X. ; 31:7, s. 1525-1539
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Tidskriftsartikel (refereegranskat)abstract
- In combination with theoretical calculations, experiments were conducted to investigate the evolution behavior of nonmetallic inclusions (NMIs) during the manufacture of large-scale heat-resistant steel ingots using 9CrMoCoB heat-resistant steel and CaF2–CaO–Al2O3–SiO2–B2O3 electroslag remelting (ESR)-type slag in an 80-t industrial ESR furnace. The main types of NMI in the consumable electrode comprised pure alumina, a multiphase oxide consisting of an Al2O3 core and liquid CaO–Al2O3–SiO2–MnO shell, and M23C6 carbides with an MnS core. The Al2O3 and MnS inclusions had higher precipitation temperatures than the M23C6-type carbide under equilibrium and nonequilibrium solidification processes. Therefore, inclusions can act as nucleation sites for carbide layer precipitation. The ESR process completely removed the liquid CaO–Al2O3–SiO2–MnO oxide and MnS inclusion with a carbide shell, and only the Al2O3 inclusions and Al2O3 core with a carbide shell occupied the remelted ingot. The M23C6-type carbides in steel were determined as Cr23C6 based on the analysis of transmission electron microscopy results. The substitution of Cr with W, Fe, or/and Mo in the Cr23C6 lattice caused slight changes in the lattice parameter of the Cr23C6 carbide. Therefore, Cr21.34Fe1.66C6, (Cr19W4)C6, Cr18.4Mo4.6C6, and Cr16Fe5Mo2C6 can match the fraction pattern of Cr23C6 carbide. The Al2O3 inclusions in the remelted ingot formed due to the reduction of CaO, SiO2, and MnO components in the liquid inclusion. The increased Al content in liquid steel or the higher supersaturation degree of Al2O3 precipitation in the remelted ingot than that in the electrode can be attributed to the evaporation of CaF2 and the increase in CaO content in the ESR-type slag.
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| 7. |
- Hytonen, Noora, et al.
(författare)
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Effect of weld microstructure on brittle fracture initiation in the thermally-aged boiling water reactor pressure vessel head weld metal
- 2021
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Ingår i: International Journal of Minerals, Metallurgy and Materials. - : Springer Nature. - 1674-4799 .- 1869-103X. ; 28:5, s. 867-876
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Tidskriftsartikel (refereegranskat)abstract
- Effects of the weld microstructure and inclusions on brittle fracture initiation are investigated in a thermally aged ferritic high-nickel weld of a reactor pressure vessel head from a decommissioned nuclear power plant. As-welded and reheated regions mainly consist of acicular and polygonal ferrite, respectively. Fractographic examination of Charpy V-notch impact toughness specimens reveals large inclusions (0.5-2.5 mu m) at the brittle fracture primary initiation sites. High impact energies were measured for the specimens in which brittle fracture was initiated from a small inclusion or an inclusion away from the V-notch. The density, geometry, and chemical composition of the primary initiation inclusions were investigated. A brittle fracture crack initiates as a microcrack either within the multiphase oxide inclusions or from the de-bonded interfaces between the uncracked inclusions and weld metal matrix. Primary fracture sites can be determined in all the specimens tested in the lower part of the transition curve at and below the 41-J reference impact toughness energy but not above the mentioned value because of the changes in the fracture mechanism and resulting changes in the fracture appearance.
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| 8. |
- Li, Jian-Li, et al.
(författare)
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Effect of FeO on the formation of spinel phases and chromium distribution in the CaO-SiO2-MgO-Al2O3-Cr2O3 system
- 2013
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Ingår i: International Journal of Minerals, Metallurgy and Materials. - : Springer Science and Business Media LLC. - 1674-4799 .- 1869-103X. ; 20:3, s. 253-258
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Tidskriftsartikel (refereegranskat)abstract
- Synthetic slag samples of the CaO-SiO2-MgO-Al2O3-Cr2O3 system were obtained to clarify the effect of FeO on the formation of spinel phases and Cr distribution. X-ray diffraction (XRD) and scanning electron microscopy (SEM) equipped with energy-dispersive spectroscopy (EDS), as well as the thermodynamic software FactSage 6.2, were used for sample characterization. The results show that the addition of FeO can decrease the viscosity of molten slag and the precipitation temperatures of melilite and merwinite. The solidus temperature significantly decreases from 1400 to 1250 degrees C with the increase of FeO content from 0wt% to 6wt%. The addition of FeO could enhance the content of Cr in spinel phases and reduce the content of Cr in soluble minerals, such as merwinite, melilite, and dicalcium silicate. Hence, the addition of FeO is conducive to decreasing Cr leaching.
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| 9. |
- Liu, Bo, et al.
(författare)
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Synthesis and properties of SrFe12O19 obtained by solid waste recycling of oily cold rolling mill sludge
- 2019
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Ingår i: International Journal of Minerals, Metallurgy and Materials. - : Springer Science and Business Media LLC. - 1869-103X .- 1674-4799. ; 26:5, s. 642-648
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Tidskriftsartikel (refereegranskat)abstract
- The aim of this study was to develop a new approach for the preparation of environmentally friendly, high-value products from oily cold rolling mill (CRM) sludge. Utilizing oily CRM sludge as a source of iron, strontium hexaferrite (SrFe12O19) powders were prepared by multi-step processes involving acid leaching, chemical conversion treatment, and synthesis by a citrate precursor. The influences of citric acid dosage and the pH of the sol system on the formation, crystallite size, and magnetic properties of the obtained SrFe12O19 powders were investigated. High saturation magnetization (74.8 mA-m(2)g(-1)) and intrinsic coercivities (614.46 mT) were achieved for pH 7.0 of the sol system, for which the molar ratio of citric acid dosage to the total dosage of Fe-3+ and Sr2+ was 1.5. This study presents a new approach to utilizing oily CRM sludge, and even refractory iron-containing solid waste.
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| 10. |
- Mostaghel, Sina, et al.
(författare)
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Influence of alumina on mineralogy and environmental properties of zinc-copper smelting slags
- 2013
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Ingår i: International Journal of Minerals, Metallurgy and Materials. - : Springer Science and Business Media LLC. - 1674-4799 .- 1869-103X. ; 20:3, s. 234-245
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Tidskriftsartikel (refereegranskat)abstract
- An iron-silicate slag, from a zinc-copper smelting process, and mixtures of this slag with 5, 10 and 15 wt-% alumina addition were re-melted, semi-rapidly solidified and characterized using scanning electron microscopy equipped with energy dispersive spectroscopy, and X-ray diffraction. The FactSageTM6.2 thermodynamic package was applied to compare the stable phases at equilibrium conditions with experimental characterization. A standard European leaching test was also carried out for all samples to investigate the changes in leaching behaviour due to addition of alumina. Results show that the commonly reported phases for slags from copper and zinc production processes (olivine, pyroxene and spinel) are the major constituents of the current samples. A correlation can be seen between mineralogical characteristics and leaching behaviours. The sample with 10 wt-% alumina addition, which contains high amounts of spinels and lower amounts of the other soluble phases, shows the lowest leachabilities for most of the elements.
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