SmCo Magnet Material And Instrument Experiment Part

  • Milling of SmCo Magnet and Sm Pieces

      SmCo magnet samples were first crushed by a hydraulic press to reduce them to a particle size ≤5 mm, to be suitable for the next milling step. A planetary ball mill (Fritsch, model Pulverisette 7) was used to further reduce the magnets into a powder using the following milling conditions: stainless steel pots and balls (diameter 10 and 1 mm), ball-to-powder ratio 3/1, 600 rpm, 3 cycles of milling (5 min) and pause (5 min). The obtained powder was shaken on an automatic stack of sieves for 15 min and the powders with size <45 μm were used in this work. The collected magnet powder was stored under inert argon atmosphere to prevent further oxidation by air. The crystalline structure of the milled, unsieved SmCo powder was determined by XRD analysis.

      Samarium powder was obtained from the samarium pieces by ball-milling with the same procedures as mentioned above, except that the material of the pot and balls was zirconium oxide. Two fractions of powders were obtained by sieving: ≥125 μm and <125 μm. The latter one was further used in this work.

      Synthesis and Characterization of Trichloride IL

      [P666,14][Cl3] was prepared according to the same procedure described in the previous work.A detailed description of the synthesis method, setup and safety considerations can be found there. Briefly, chlorine gas (5.56 g, 78 mmol) was purged into dry [P666,14]Cl (40.66 g, 78 mmol) at room temperature in a flask protected from light. The chlorine gas was controlled by a chlorine flow meter made with chlorine compatible materials.

      Dissolution Experiments

      Dissolution was conducted in two series of tests with 4 mL glass vials protected from light. First, IL mixture (1 mL) with various volume fractions of [P666,14][Cl3] in [P666,14][Cl] (from 0 vol % to 100 vol %) were mixed with 21 ± 1 mg of SmCo magnet powder at 200 rpm for 24 h at room temperature (23 °C). Each leachate was then separated from the solid residue by centrifugation. Second, 1 mL of IL mixture [P666,14]2[Cl3]Cl (50 vol % [P666,14][Cl3] in [P666,14][Cl]) were mixed with different amounts of SmCo powder. The procedures for mixing and phase separation were the same as the methods mentioned above. The metal concentrations in the IL phases were measured by ICP-OES analysis. To measure metal contents in IL samples by ICP-OES analysis, a certain amount of IL samples was digested with strong acids into aqueous solutions with a microwave digestion instrument. This microwave digestion procedure is only for analytical purpose and has no influence on the leaching experiments.

      The Alnico Ring Magnets dissolution rate was studied at 23 and 50 °C; 40 ± 1 mg of SmCo powder was mixed with 1 mL [P666,14]2[Cl3]Cl at 200 rpm. After a certain time, 10 μL of the IL leachate was taken out and treated though microwave digestion prior to ICP-OES analysis.