Direkte Beobachtung des Wachstums von Eisen auf Magnetit

Abstract

Morphologische Untersuchungen im Heiztisch‐ und im Rasterelektronenmikroskop. Ausbildung typischer Makro‐ und Mikroporensysteme in der Eisenphase. Neue Theorie über das Minimum in der Reduktionsgeschwindigkeit von Magnetit bei 750 °C.

On the Relationships between the Kinetics and Mechanisms of Gaseous Hydrogen Reduction of Solid Nickel Oxide

“…Large radial fissures were observed at the middle of the iron nuclei during the reduction of magnetite below approximately 550°C; in addition to the large radial fissures, the iron nuclei contained extensive micropores. [15,16] In the reduction of tungsten oxide, [17] it was found that, when the WO 2.96 was reduced to metal with hydrogen gas between 500°C and 700°C, a star-shaped cracking pattern was formed on the solid surface. It was suggested that the star-shaped cracking pattern is formed due to a local contraction of the product during the reduction process.…”

The influence of CaO on the precipitation behaviour of iron in the reduction of iron oxide

“…Some of these works tried to explain the difference in the structure of iron when pure iron ore material had been used and other models took into account the peculiarities of material which contained CaO. The model which is produced by the results of this investigation is based on the ideas of Wagner [3], Rist et al [7,11], Pluschkell [15] and Schiller [14] on the nucleation and the nucleus growth. As mentioned above, the relationship between the capacity of the production of iron ions at the 2-phase boundary gas/wustite, and the capacity of the transport of the iron ions inwards, is responsible for the precipitation behaviour of the iron.…”

“…Many reports have been published on the subject of the reduction mechanism, the reduction rate and the swelling index, but only a few on the precipitation behaviour of iron [1][2][3][4][5][6]. The precipitation behaviour, among other things, is responsible for the reduction rate and the swelling conduct of the iron ore. We indicate the different types of product structure in the reduction of iron oxides to metallic iron depending on the factors: porous, dense and fibrous [4][5][6][7][8][9][10][11][12][13][14][15][16][17][18][19][20][21]. The reduction characteristics of each microsructural type are different and depend on the reduction temperature, reducing gas composition and the nature of the initial oxide.…”

“…There is no similarity in the published reports about the precipitation behaviour, and mechanisms of reduction of iron oxides, and the effect of CaO addition, due to different materials (e.g., hematite, magnetite, wü stite ...), reduction conditions were used by various researchers [7][8][9][10][11][12][13][14][15][16][17][18][19][20][21]. Thus, in order to eliminate irregularities that may be caused by unknown impurities, chemically pure raw materials were used in the experiments.…”