Alpha-Fe(2)O(3) nanorods and nanotubes have been synthesized and characterized by high-resolution transmission electron microscopy and X-ray diffraction. By means of different surfactant assistance, the high-quality one-dimensional products were obtained, respectively, with aqueous butanol solution as the solvent and carbamide as the base, giving rise to single-crystalline products at 150 degrees C. The formation mechanism has been presented. Significantly, the magnetic investigations show that the magnetic properties are strongly shape-dependent; i.e., the nanorods have a Morin transition at 166 K from canted antiferromagnetic state to antiferromagnetic state, while the nanotubes exhibit a three-dimensional magnetic ordering above 300 K that has been attributed to the presence of small particles in a few regions of the tubes.

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Distribution of inclusions plays an essential role in inducing intracrystalline ferrite, and the migration behavior of inclusions during solidification has a significant influence on their distribution. The solidification process of DH36 (ASTMA36) steel and the migration behavior of inclusions at the solidification front were observed in situ using high-temperature laser confocal microscopy. The annexation, rejection, and drift behavior of inclusions in the solid–liquid two-phase region were analyzed, providing a theoretical basis for regulating the distribution of inclusions. Analysis of inclusion trajectories showed that the velocity of inclusions decreases significantly as they near the solidification front. Further study of the force on inclusions at the solidification frontier shows three situations: attraction, repulsion, and no influence. Additionally, a pulsed magnetic field was applied during the solidification process. The original dendritic growth mode changed to that of equiaxed crystals. The compelling attraction distance for inclusion particles with a diameter of 6 μm at the solidification interface front increased from 46 μm to 89 μm, i.e., the effective length for the solidification front engulfing inclusions can be increased by controlling the flow of molten steel.

Abstract. Steel samples under different pulse magnetic field are produced using self-developed pulsed magnetic field generator, and the discharge voltage of the pulsed magnetic field selected from the experiment is 0V, 40V, 80V, and 100V four gradient levels. The morphology of the microstructure is photographed by metallographic microscope, then the calculation of the multi fractal software，which is designed by Visual C++，of the optical image input is carried out. The distribution patterns of different pulse magnetic fields have been quantitatively characterized by the results of the calculation. With the increase of the discharge voltage, ( Multifractal spectrum width) decreases from 0.481338 to 0.439.5 and then increases to 0.545596, which explains process of the change from uniform to uniform to uneven and more complicated organizational structure; (multifractal spectrum) ＞ 0, the fine microstructure dominated，the increased proportion of intracrystalline ferrite.