| Abstrakt: |
[Display omitted] • Nano-sized Nd–Fe–B was synthesized by calciothermic reduction. To address the compromise of the magnetic properties by calcium by-products, a new rinsing method was developed for the selective removal of CaO. The proposed method uses an NH 4 NO 3 solution, zeolite, and a Schlenk line, thereby enabling the attainment of high-performance, high-purity magnetic nanostructures. Magnetic Nd 2 Fe 14 B nanoparticles are synthesized by a bottom-up process via calciothermic reduction, which complements the negative reduction potential of rare-earth elements, thus affording nanoscale products. However, to obtain high-purity, high-performance magnetic nanoparticles, residual calcium by-products that persist after calcium thermal reduction-diffusion must be selectively removed. In previously reported rinsing methods, H 2 O or H+ diffuse into the magnetic nanoparticles, thereby leading to hydridation. Herein, we propose a novel rinsing solution, NH 4 NO 3 /methanol, that does not deteriorate the magnetic properties. The magnetic properties are enhanced by selectively removing calcium by-products (i.e., CaO) from the magnetic nanoparticles with NH 4 NO 3 /methanol solution and by preventing hydridation and oxidation using zeolite and Schlenk line. The intrinsic coercivity (H ci) is maintained at 75.1 % (from 8.5 kOe to 6.3 kOe), and the saturation magnetization (M s) increases two-fold (110.08 emu/g) after rinsing with NH 4 NO 3 solution, compared with prior to rinsing treatment (47.363 emu/g). Rinsing the magnetic nanoparticles with NH 4 NO 3 /methanol solutions does not cause deterioration of the obtained Nd 2 Fe 14 B nanostructures, where Ms = 112.0 emu/g and H ci = 8.4 kOe after rinsing with NH 4 NO 3 /methanol using the zeolite and Schlenk line. Using rinsing methods in previous studies. 3.5 % of the initial coercivity is maintained, whereas with the new rinsing method, 95.2 % of the coercivity is maintained, thus indicating that rinsing does not induce deterioration of the magnetic properties. [ABSTRACT FROM AUTHOR] |
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