Novel FeSiAl soft magnetic composites (SMCs) with a phosphate insulation coating doped with magnetic NiFe2O4 nanocrystalline particles were prepared. They exhibited high permeability, ultra-low loss, and high thermal stability. The saturation magnetization of the FeSiAl SMC increased, while the coercivity decreased due to the exchange coupling of the magnetic nanocrystalline particles. The total loss of the novel SMC decreased to 139.93 kW/m3 at 100 mT and 100 kHz, which is only one-third of that of common commercially available Sendust composites, while the permeability was up to 62 for the reduced demagnetization field. Furthermore, three-dimensional loss separation was performed based on the nonlinear regression method, and the complex permeability was separately addressed as the domain-wall movement and spin resonance parts. The minimum total loss was ascribed to the significantly reduced hysteresis loss and the slightly reduced eddy current loss, corresponding to the low coercivity (Hc = 0.341 Oe) and high impedance (|Z| = 67.1 MΩ). This was attributed to the improved magnetic properties and resistance of the insulation coating, which was related to the magnetic nanoparticles embedded in the insulation coating. The permeability was mainly derived from the spin resonance due to the complete insulation coating and ultrafine particles. This novel SMC with a phosphate insulation coating doped with magnetic NiFe 2 O 4 nanocrystalline particles provides a high-efficiency, high-frequency, and high-saturation soft magnetic device for switching power supplies, photovoltaic inverter boost inductors, and other applications.
Ultrafiltration membranes with relatively small pores are highly expected in various separation cases. As a flexible manner to efficiently tighten the pores, post modification provides a robust platform for preparing the desired membranes. However, the endeavor to pursue high permselectivity of the membranes has been made by paying close attention to the modification layers while the effects of the substrate membranes are generally overlooked. In this work, tight membranes with ultrahigh permeance were produced by coating polyethylenimine (PEI) on gradient nanoporous phenolic substrates. Cationic PEI was tightly deposited on the negatively charged phenolics via electrostatic deposition, thus reducing the effective pore sizes to ∼2.6 nm through a single-step coating. The gradient porous nanostructures still remained after PEI coating in the phenolic membranes. The coated membranes exhibited ∼4–45 times higher permeance than counterparts with similar rejections. As the cationic PEI was distributed on the membrane surface and pore wall after coating, the positively charged membranes thus produced were able to efficiently separate cationic dyes from water.
Graphene oxide (GO) membranes exhibit ultrafast water permeation properties, which have been employed in various membrane-based separations including nanofiltration for dye removal from textile wastewater. However, it’s still a great challenge to achieve precise control over the microstructure of GO membranes and obtain ultrathin GO membranes with exceptional separation efficiency and robust membrane structure. Herein, in-situ confined interfacial polymerization (IP) is proposed for fabricating loose polyamide (PA)@GO hybrid membranes with high permeance and dye rejection as well as robust membrane stability. A new diamine of sulfadiazine (SA) with intrinsic hydrophilic and conjugated sulfonamide groups is employed as cross-linker of GO membranes and monomer of PA in IP process, simultaneously. PA is in-situ synthesized in confined GO interlayer via IP process and intercalated into GO interlayer, which enlarges the interlayer spacing of GO membranes gradiently. The combination of hydrophilic PA nanofiltration layer on GO membrane surface and the PA intercalated GO membrane with varying interlayer spacing creates hierarchical transport channels for water molecules, which contributes to the high water permeance. Moreover, the less reactive SA monomer endows PA@GO selective layer with appropriate negative charge and loose transport channels, which contributes to both of high permeance and dye rejection due to Donnon effect and size exclusion effect. The PA@GO hybrid membrane exhibits high permeance of 75.5 L/(m 2 ·h·bar) with TB dye rejection of 99.8 %, and exhibits low NaCl rejection of 11.6 %. Moreover, PA@GO hybrid membrane shows good fouling resistance and long-term stability as well as stable separation performance under harsh conditions. Both of high permeance and dye rejection of PA@GO hybrid membrane suggests that the integration of PA nanofiltration layer and GO membrane via in-situ confined interfacial polymerization can achieve the delicate control over the interlayer channel structure and the physicochemical properties of the membrane surface of GO membranes, which offers a promising method to break through the trade-off effect between permeability and selectivity of GO membranes.
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