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    Effects of carbon doping and annealing temperature on magnetic MnAl powders and MnAl polymeric composites
    (2021-03-01)
    Thongsamrit, Wannisa
    ;
    Charoensuk, Thanida
    ;
    Saetang, Panissa
    ;
    Jantaratana, Pongsakorn
    ;
    Ruttanapun, Chesta
    Process parameters leading to magnetic polymer composites, an essential ingredient in the additive manufacturing of rare-earth-free magnets, are investigated. The induction melting of manganese (Mn) and aluminum (Al), and subsequent annealing at 450, 500, or 550 °C for 20 min, gave rise to ferromagnetic τ-MnAl phase, as well as other phases. The nonmagnetic Al<inf>4</inf>C<inf>3</inf> and oxide phases were then removed by the magnetic separation. Magnetic powders from the magnetic separation were incorporated in polylactic acid (PLA) matrix via a solution route. The remanent magnetization as high as 4.3 emu/g in the powder form was reduced to 2.3-2.6 emu/g in the composites. The reduction in coercivity was minimal, and the largest value of 814 Oe was obtained when the powder annealed at 450 °C was loaded in the composite. The phase composition and hence magnetic properties were even more sensitive to the carbon (C) doping. Interestingly, the addition of 3% C led to coercivity as high as 1445 Oe in MnAl-C powders without further annealing. The enhanced coercivity was attributed to the domain wall pinning by the AlMn<inf>3</inf>C phase, and magnetizations are likely increased by this phase.
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    Ferromagnetism of manganese-aluminium alloyed with 0–3% carbon from direct induction melting and subsequent annealing
    (2020-01-01)
    Charoensuk, Thanida
    ;
    Saetang, Panissa
    ;
    Ruttanapun, Chesta
    ;
    Phrompet, Chaiwat
    ;
    Pinitsoontorn, Supree
    The transformation from ε to τ phase is investigated in manganese-aluminium (Mn<inf>55</inf>Al<inf>45</inf>) alloyed by the induction melting. By annealing Mn<inf>55</inf>Al<inf>45</inf> at 450–550°C for 2 h, the ferromagnetic τ-MnAl is enhanced at the expense of ε phase. The largest coercivity of 1139 Oe and remanent magnetization of 3.71 emu/g are obtained after annealing at 550°C. The additions of 1 and 2% carbon affect the phase and magnetic properties of Mn<inf>55</inf>Al<inf>45</inf> but the 2 h annealing at 550°C still leads to the largest coercivity. Interestingly, substantial coercivity and magnetizations are directly obtained in (Mn<inf>55</inf>Al<inf>45</inf>)<inf>98</inf>C<inf>2</inf> and (Mn<inf>55</inf>Al<inf>45</inf>)<inf>97</inf>C<inf>3</inf> by the induction melting without further heat treatments.
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    Properties of manganese oxide films prepared by electrostatic deposition technique
    (2018-01-01)
    Songkeaw, Potiyan
    ;
    Onlaor, Korakot
    ;
    Thiwawong, Thutiyaporn
    ;
    Tunhoo, Benchapol
    In this work, the electrostatic spray deposition technique was applied to prepare manganese oxide tin films. The effects of post annealing at various temperatures on the properties of manganese oxide film were studied. The properties of the films were assessed by X-ray photoelectron spectroscopy and field-emission scanning electron microscope. In addition, the electrochemical properties of the manganese oxide films were investigated. It was found that the prepared films could be used for supercapacitive, energy storage devices.