We have first studied the orientation process of α- Al2 O3 fine particles, using in situ neutron diffraction measurements on the particles in a liquid solvent under magnetic fields. The neutron diffraction intensity of 006 and 116 reflections is significantly reduced by the vertical magnetic field up to 100 kOe, while the 113 and 204 reflections remain unchanged within the experimental accuracy. The energy balance between the magnetic anisotropic energy and the thermal fluctuation following the Boltzmann distribution is important for the crystal orientation of the α- Al2 O3 particles in suspension. Comparing the experimental data with the theoretical equation, we find that the magnetic field, where the particles are fully oriented, is above 200 kOe. Our obtained data prove that the in situ neutron diffraction measurement is a powerful tool for investigating the alignment of the crystal orientation under magnetic fields.
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