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Author: search.filters.author.Charoensuk, ThanidaSubject: search.filters.subject.Magnetic polymer composite

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    Item type:Publication,
    Loading effect of sol-gel derived barium hexaferrite on magnetic polymer composites
    (2021-03-01)
    Charoensuk, Thanida
    ;
    Thongsamrit, Wannisa
    ;
    Ruttanapun, Chesta
    ;
    Jantaratana, Pongsakorn
    ;
    Sirisathitkul, Chitnarong
    Solution–processing methods were investigated as viable alternatives to produce the polymer-bonded barium hexaferrite (BaM). BaM powders were first synthesized by using the sol-gel auto-combustion method. While the ignition period in two synthesis batches varied, the morphology of hexagonal microplates and nanorods, as well as magnetic properties, were reproduced. To prepare magnetic polymer composites, these BaM powders were then incorporated into the acrylonitrile-butadiene-styrene (ABS) matrix with a weight ratio of 80:20, 70:30, and 60:40 by using the solution casting method. Magnetizations were linearly decreased with a reduction in ferrite loading. Compared to the BaM loose powders and pressed pellet, both remanent and saturation magnetizations were lower and gave rise to comparable values of the squareness. The squareness around 0.5 of BaM samples and their composites revealed the isotropic alignment. Interestingly, the coercivity was significantly increased from 1727–1776 Oe in loose BaM powders to 1874–2052 Oe for the BaM-ABS composites. These composites have potential to be implemented in the additive manufacturing of rare-earth-free magnets.
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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.