Papers by Keyword: Strong Magnetic Field

Abstract: Preparation of Mn-Cu based damping alloy ingots coupled with strong magnetic fields shows many interesting phenomena on the solidification microstructure and the crystal lattice. In this study, modified M2052 ingots were prepared under different magnetic fields to investigate the bulk solidification behavior by using optical microscopy, scanning electron microscopy, energy dispersive spectroscopy and X-ray diffraction. Metallographic analysis reveals that the deflection angle of the primary dendrite arm increases with the increase of magnetic field strength. The distribution of chemical composition characterized by X-ray Fluorescence discloses that Mn is enriched while Cu is depleted along the circumferential surface side, and the variation tendency changes from almost a level to a sloping line under applied magnetic field. High magnetic field have altered the orientation of the γ-Mn dendrites from (200) to (111), and the coupling mechanism of alloy solidification with strong magnetic field is discussed based on the experimental results.

Abstract: Orientation technique based on the magneto-scientific crystal alignment phenomenon combined with electrophoretic deposition (EPD) technique was applied for the seeding process of zeolite L particles. Well-dispersed, ethanol-based zeolite L suspension was prepared and then consolidated on porous zirconia substrates by EPD. Conducting polypyrrole film synthesized on the zirconia substrate was used as an anodic substrate for the EPD process. The EPD was performed in a superconducting magnet with applying 12 T strong magnetic field to the suspension. The degree of orientation was characterized by XRD and compared with that of the zeolite L layer prepared by slip casting in a 12 T strong magnetic field using the same suspension.

Abstract: Beta-sialon:Eu²⁺ phosphor deposits were fabricated by electrophoretic deposition (EPD) process within a strong magnetic field (12 T). The direction of the magnetic field was adjusted to be parallel or perpendicular to that of the electric field, that is, vertical-or horizontal setup. The oriented deposits were fabricated by aligning the β-sialon:Eu²⁺ particles along the higher magnetic-susceptibility c-crystal axis (a, b-crystal plane). For the case of vertically-setup magnetic field, the oriented deposit aligned along the c-axis possessed higher relative deposit density than the randomly fabricated deposit, as a result, varying the intensity ratio of emission and transmitted excitation, and therefore, presenting different chromaticity coordinates; for the case of horizontally-setup magnetic field, photoluminescence (PL) intensities of the deposits oriented along c-axis were significantly improved by comparing with those of the randomly-oriented ones.

Abstract: The recent interest in positrons distribution in the space revealed the anomalous presence of high energetic positrons. There are different possible origins of such positrons, including the decay of heavy particles in the dark matter, also pulsars or neutron stars. In our study we calculated the annihilation properties of the electron – positron bound system in superstrong magnetic fields expected for neutron stars. For this aim we use solutions of the (relativistic) Bethe-Salpeter equation derived by L.B. Leinson and A. Perez [1]. The results indicate strong dependency of the annihilation properties (rate and intensity) on the value of the magnetic field.

Abstract: This paper reviews the most important results by the authors on the processing of textured -Si3N4 and -sialon by slip casting in a strong magnetic filed of 12 T and reaction-sintering. The a, b-axis textured -Si3N4 and -sialon have been obtained using the static magnetic field because of the magnetic susceptibility of ca, b > c c for -Si3N4. However, the c-axis textured -Si3N4 has also been successfully obtained using a rotating magnetic field. The -Si3N4 crystal was found to exhibit substantially stronger orientation ability than the a-Si3N4 crystal regardless of the Si3N4 raw powders. It reveals that the -Si3N4 nuclei play a key role in the texture development in -Si3N4/-sialon.

Abstract: This paper reports the texture development in Si3N4 by strong magnetic field alignment (SMFA), using slip casting of α-Si3N4 raw powder (SN-E10) and pressureless sintering. The texture of β-Si3N4 in the green and sintered bodies was characterized by X-ray diffraction analysis (XRD) and scanning electron microscopy (SEM). The a, b-axis and c-axis aligned β-Si3N4 has been obtained by the static and rotating magnetic field of 12 T, respectively. The β-seed addition and prolonged sintering both enhance the texture, but the former is more efficient. This work suggests an efficient SMFA strategy of producing highly textured β-Si3N4, particularly the unidirectionally c-axis aligned β-Si3N4 by seeding the α-raw powder using the less-agglomerated β-phase particles.

Abstract: We have reported that development of texture can be controlled by colloidal processing in a strong magnetic field followed by heating even for diamagnetic ceramics such as alumina, titania and so on. We demonstrate in this study that alumina/alumina laminar composites with different crystalline-oriented layer are produced by electrophoretic deposition (EPD) in a strong magnetic field. This composite was fabricated by alternately changing the angle between the directions of the magnetic and electric fields layer by layer during EPD in 12T. The grains in alternate layers are aligned differently.

Abstract: A strong static magnetic field (SSMF) of about 10 T was introduced to the aging process of AZ91 magnesium alloy. Comparing with conventional aging, in the first stage of aging with SSMF, discontinuous precipitation of Mg17Al12 at grain boundary was accelerated. The magnetically induced grain boundary migration might be responsible for this acceleration effect. The density of the Mg17Al12 continuous precipitates inside the grains was increased and the precipitation plates became thinner in SSMF pre-aged specimens, which might be ascribed to the retarded volume diffusion resulted from the SSMF.