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Carbonization of pure MnO 2 by CH 4 -H 2 gas mixture with various CH 4 /(CH 4 + H 2 ) molar ratios in the temperature range of 900–1250 °C had been performed in our previous work. This study further investigated the carbonization and alloying process of MnO 2 by CH 4 -H 2 gas mixture in the presence of Fe 2 O 3 at 900–1300 °C using XRD, optical microstructure, SEM-EDS and phase diagram analyses. Carbonization test of pure Fe 2 O 3 was also conducted to understand the effect of Fe 2 O 3 on the carbonization of MnO 2 more explicitly. It was found that Fe 2 O 3 could be carbonized to Fe 3 C at 900–1150 °C. The Fe 2 O 3 briquettes began to melt at 1100 °C and a large amount of Fe-C melts appeared as the temperature went up to 1150 °C. When the MnO 2 + 25 wt%Fe 2 O 3 briquettes were reduced at 900–1000 °C in CH 4 -H 2 gas mixture, the Fe 2 O 3 was preferentially carbonized to Fe-C phase while the MnO 2 was only reduced to MnO. The formation of Fe-C phase was beneficial to the carbonization of MnO since the carbonization temperature of MnO can decrease from 1100 °C to 1000 °C. The carbonization degree of MnO was dramatically accelerated over 1100 °C due to the transformation of Fe-C phase from solid state to melts. Morphology analysis indicated that the MnO core was wrapped by the shell of Fe-C melts. The alloying process of Mn-Fe-C was conducted through the elements migration of Fe and Mn between the core and shell. At 1300 °C, the Mn-Fe-C alloy turned to melt and aggregated since the highest melting temperature of the Mn-C-25 wt% Fe system was only 1274 °C. Finally, a ferromanganese crude alloy with 68–72 wt% Mn, 20–25 wt% Fe and 6.0–8.0 wt% C was obtained when the MnO 2 + 25 wt% Fe 2 O 3 briquettes were carbonized by CH 4 -H 2 gas mixture at 1300 °C for 60 min. [ABSTRACT FROM AUTHOR]

Phase transformation of MnO 2 and Fe 2 O 3 roasted in air atmosphere at temperatures of 500–1400 °C for synthesizing manganese ferrite (Mn x Fe 3 − x O 4 ) has been reported. In current work, the morphologies and properties of the Mn x Fe 3 − x O 4 products with various x values during the synthesis process were characterized by XRD, XPS, SEM-EDS, AFM, VSM and Vickers-type microhardness analyses to further understand the formation mechanism of Mn x Fe 3 − x O 4 from MnO 2 and Fe 2 O 3 by solid-state reaction. Results showed that the x value in the Mn x Fe 3 − x O 4 gradually increased to 1 with the extension of roasting time from 30 min to 120 min at 1300 °C. Morphology measurements indicated the Mn x Fe 3 − x O 4 particles presented polyhedron structure and the shape of polyhedron particles gradually became regular with the increasing of x value. In addition, it's interesting to find that the polyhedron particles had multi-layer stacking structure and the thickness of each layer was about 5 nm. The saturation magnetization of the Mn x Fe 3 − x O 4 samples increased with the rising of x value. A polyhedral MnFe 2 O 4 (x = 1) product with saturation magnetization of 78.5 emu/g was obtained when the MnO 2 and Fe 2 O 3 briquettes with molar ratio of 1:1 were roasted at 1300 °C for 120 min. Moreover, the Hv hardness of the Mn x Fe 3 − x O 4 increased from 154.8 kg/mm 2 to 339.4 kg/mm 2 with elevating the temperature from 1000 °C to 1300 °C. [ABSTRACT FROM AUTHOR]

An investigation on the behavior of SnO 2 in the tin-bearing iron concentrates during the reduction sintering process (RSP) has been conducted by the authors' group. It was found that only about 30 wt.% of tin was removed under the optimal conditions. However, the underlying reason why it was so difficult to remove tin by the RSP was not understood. In this study, the phase evolution of tin oxide, iron oxide and calcium oxide under simulative sintering conditions was investigated by varying the gas compositions, sintering temperature and basicity (CaO/SiO 2 ). The results indicated that the Ca-Sn oxides were prior formed at 900 °C–1000 °C in the reduction atmosphere with CO / (CO + CO 2 ) = 10–40 vol.%, while the phases of Fe-Sn spinel (Fe 3 − x Sn x O 4 ) and Ca-Fe-Sn oxides were easily generated as the temperature increased to 1100 °C–1200 °C. The phases of Fe 2 − 4x/3 Sn x O 3 and Ca-Fe-Sn-Si oxides began to generate at 1100 °C in an oxidative atmosphere with O 2 /(O 2 + CO 2 ) = 25–100 vol.%. In addition, increasing alkalinity accelerated the formation of Ca-Sn oxides under reduction atmosphere, which brought about an adverse effect on the tin removal in the sintering process. [ABSTRACT FROM AUTHOR]