Three dimensionally ordered macroporous bioactive SiO 2 CaO Na 2 O P 2 O 5 glass (3DOM BG) is synthesized by using the sol gel method. After an in vitro test in simulated body fluid (SBF), the hydroxyapatite (HAp) crystalline phase is clearly formed on its surface as confirmed by X ray diffractometry (XRD) and Raman spectroscopy. Mag netic 3DOM BG/Fe samples are synthesized by partial substitution of SiO 2 with iron oxide. Whilst the HAp layer is not confirmed, energy dispersive spectroscopy (EDS), Fourier transform infrared spectroscopy (FTIR) and XRD analysis reveal calcium phosphate layer on the surface of 3DOM BG/Fe samples after the SBF soaking. The growth of HAp like layer is slower with increasing iron oxides. The initial mechanism that thought to induce bone forma tion is reduced due to the replacement of Ca 2+ with Fe ions in the glass network. The formation of HAp like layer is modified by the sedimentation of Ca and P while the nonmagnetic 3DOM BG forms the calcium phosphate by the ionic exchange following the Hench mechanism. The adult human adipose tissue derived stem cells (hADSCs) can be closely attached and well spread on the flat plate of all 3DOM BG/Fe and 3DOM BG. Without detectable cytotoxicity possibly induced by iron oxides, the osteoblast can be grown and proliferated. In addition to these bioactivity and biocompatibility, porous structures can allow their possible use in targeted drug delivery and magnetic properties of 3DOM BG/Fe can essentially be implemented in hyperthermia therapy.

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.

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 Al4C3 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 AlMn3C phase, and magnetizations are likely increased by this phase.

Iron oxides in macro/mesoporous bioactive glasses were characterized by synchrotron X-ray absorption near edge structure (XANES) spectroscopy. This magnetic phase was introduced by adding Fe(NO 3 ) 3 9H 2 O during the sol-gel synthesis. The obtained bioactive glass scaffolds exhibited superparamagnetism, in which the magnetization was increased with the increase in the Fe molar ratio from 10 to 20%. The linear combination fits of the XANES spectra indicated that the increase in the Fe molar ratio to 20% enhanced the γ-Fe 2 O 3 formation at the expense of the α-Fe 2 O 3 phase. This variation also promoted the formation of fine-grained bone-like apatites on the surface of the scaffolds in the in vitro test. The apatite growth between three and seven days was confirmed by the changing elemental compositions. However, the highest magnetic proportion led to the distortion of the skeleton walls and the collapse of the porous networks.

Three dimensionally ordered macroporous bioactive glasses (3D0M-BGs), namely 80SiO2-15CaO-5P2O5, were synthesized by sol-gel method. PMMA colloidal crystals and non-ionic block copolymers P123 were used as cotemplates. The amorphous 3D0M-BGs had skeletal walls enclosing macropores. Such structure resulted from octahedral and tetrahedral holes of the face-centered cubic {fee) closest packed PMMA templates and windows interconnecting through macropores network. The thicknesses of the walls were around 50 nm-80 nm and the windows were 90 nm-110 nm in diameter. These wall thickness is increased by with an increase in ageing time up to 24 h and then gradually reduced with further increase in aging time. Vibration bands of Si-O-Si and P-O were evident in infrared spectra which are in agreement with EDS spectra indicating Si, P and Ca compositions. After in vitro bioactivity testing by soaking 3D0M-BGs in simulated body fluid at 37 °C, the crystallization of amorphous calcium phosphate layers compatible to the bone component of hydroxyl carbonate apatite were rapidly formed within 3 h. These results indicated that these 3D0M-BGs resembled ideal bone implant materials.

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Ceramic–polymer paste-injection molding is demonstrated as a facile fabrication route for barium hexaferrite magnets. Interestingly, these low-density (1.90–2.35 g/cm3) magnets exhibit substantial coercivity of 3868–4002 Oe. When ceramic paste without polymeric additives is used, reduced coercivity and slightly increased magnetizations are obtained from a magnet with the density of 2.55 g/cm3. Their magnetizations are also higher than those obtained from compactions of sol–gel-derived powders. For compact magnets (3.46–3.77 g/cm3), the DI water addition results in a slightly higher magnetization but lower coercivity than dry-pressed magnets. Compactions into disk and bar magnets give rise to comparable magnetic properties. The morphological characterizations reveal smaller barium hexaferrite particles leading to larger coercivity, and the density and shape of magnets have a less pronounced effect.

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