Preparation and characterisation of Fe/Fe3O4 fibres based soft magnetic composites

Soft magnetic composites (FSMCs) have been prepared by using Fe fibres coated with a layer of Fe₃O₄, this layer playing the role of insulating material. The coating was made via blackening method by simply immersing the fibres in the blackening bath for 5, 10 and 15 min. The formation of the Fe₃O₄ coating on the surface of the fibres was confirmed by X-ray diffraction. The SEM investigation, used to evaluate the thickness of the coatings, has proved that increasing the coating duration leads to the increase of the coating thickness and complete coverage of the surface of the fibres. Differential scanning calorimetry and thermomagnetic measurements were used to investigate the thermal stability of the composite fibres. The fibres coated with Fe₃O₄ were compacted at a compaction pressure of 700 MPa to obtain toroidal magnetic cores. The obtained cores were characterised in DC and AC magnetisation regime. The analysis of the quasi-static hysteresis loops evidenced that increasing the thickness of the Fe₃O₄ leads to a slight deterioration of the compact's magnetic properties. However, as the thickness of the Fe₃O₄ layer increases, the development of eddy currents at a larger scale is hindered as proved by the AC magnetic investigations. A model for analytic separation of the core losses is proposed. By applying this model to the prepared samples, we are now able to discriminate between the occurring losses and adjust the preparation process of new samples to the targeted characteristics.     

Microstructure and microwave-frequency electromagnetic properties of Ni0.4Zn0.6Fe2O4/Ba0.6Sr0.4TiO3 composites

(x)Ni_0.4Zn_0.6Fe₂O₄+(1−x)Ba_0.6Sr_0.4TiO₃ composite ceramics with x=0.6, 0.7, 0.8, 0.9 and 1 were synthesized by solid state reaction method. The high dense composites have only two phases, i.e., Ni_0.4Zn_0.6Fe₂O₄ and Ba_0.6Sr_0.4TiO₃. The permittivity ε′ of the composites decreases slightly with the frequency increasing from 3 MHz to 1 GHz. The permittivity ε′′ of the composites also shows a little increase with frequency in the 3 MHz–1 GHz range. The permeability displays a relaxation resonance within the 3 MHz–1 GHz frequency range. The permeability μ′ increases while the cut-off frequency decreases with the Ni_0.4Zn_0.6Fe₂O₄ concentration, obeying the Snoek's law μ_if_r=constant. The permittivity ε′ of the composites decreases with Ni_0.4Zn_0.6Fe₂O₄ concentration. The composites have a relatively higher ε′ than the pure Ni_0.4Zn_0.6Fe₂O₄ at 1–10 GHz. In the frequency range of 1–10 GHz, the magnetic permeability μ′ reaches its maximum and μ′′ shows a minimum for the composite with x=0.6 in all ceramics. The permeability μ′ of the composites decreases with dc magnetic field at 1–10 GHz. The permeability shows a domain wall resonance, and the resonance frequency shifts to high frequency with the dc magnetic field. The permittivity was also influenced by the dc magnetic field due to a magnetodielectric effect.     

Magneto-dielectric laminated Ba(Fe0.5Nb0.5)O3-Bi0.2Y2.8Fe5O12 composites with high dielectric constant and high permeability

Magneto-dielectric laminated ceramic composites of xBa(Fe_0.5Nb_0.5)O₃-(1-x)Bi_0.2Y_2.8Fe₅O₁₂(BFN-BYIG) with high volume fractions of the giant dielectric constant material BFN (x=10, 30, 50, 70 wt%) were fabricated by the solid-state sintering method. Microstructure, dielectric and magnetic properties of the composites were investigated. The composites possess stable dielectric properties in the frequency range from 100 Hz to 1 MHz with high dielectric constant and low dielectric loss. The maximum permeability of the magneto-dielectric laminated composites reaches up to about 25. And the magnetic behaviors are strongly dependent on the mass ratio of BYIG. The results indicate that such multilayer structures of BFN/BYIG can enhance the permeability and decrease the dielectric and magnetic loss efficiently.     

Hollow polyaniline/Fe3O4 microsphere composites: Preparation,characterization, and applications in microwave absorption

Hollow polyaniline/Fe₃O₄ microsphere composites with electromagnetic properties were successfully prepared by decorating the surface of hollow polyaniline/sulfonated polystyrene microspheres with various amounts of Fe₃O₄ magnetic nanoparticles using sulfonated polystyrene (SPS) as hard templates and then removing the templates with tetrahydrofuran (THF). The synthesized hollow microsphere composites were characterized by FT-IR, UV/Vis spectrophotometry, SEM, XRD, elemental analysis, TGA, and measurement of their magnetic parameters. Experimental results indicated that the microspheres were well-defined in size (1.50–1.80 μm) and shape, and that they were superparamagnetic with maximum saturation magnetization values of 3.88 emu/g with a 12.37 wt% content of Fe₃O₄ magnetic nanoparticles. Measurements of the electromagnetic parameters of the samples showed that the maximum bandwidth was 8.0 GHz over ?10 dB of reflection loss in the 2–18 GHz range when the Fe₃O₄ content in the hollow polyaniline/Fe₃O₄ microsphere composites was 7.33 wt%.     

Realizing high-resistivity and low-loss Fe–Si–Al based soft magnetic powder cores through interfacial chemistry regulation

As a symbolic ceramic oxide, SiO₂ is one of the most important insulating layers of soft magnetic powder cores (SMPCs). Thus, the reaction of SiO₂ with Fe–Si–Al based SMPC substrates during annealing, the induced phase transition of the core-shell structure, and the influence of the latter on the magnetic characteristics of SMPCs are worth investigating. In this study, Fe–Si–Al based SMPCs were successfully synthesised using fluidised-bed chemical vapour deposition (FB-CVD) at various times, combined with an electric pressure-assisted sintering method and high-temperature annealing. The evolution of the insulating layers with different thicknesses was investigated. With increasing thickness, the insulating layers (shell) gradually transformed into Al₂O₃ and the Fe–Si–Al substrate (core) to Fe₃Si. The newly formed Al₂O₃ and Fe₃Si increased the coercivity and saturation magnetisation of the SMPCs, while the hysteresis loss increased with thicker insulating layers. The generated Al₂O₃ improved the integrity of the insulating layers, preventing possible point contact between particles, and significantly reduced the Eddy current losses. The SMPCs with the thickest insulating layers (7#) exhibited superior magnetic properties (Ms = 129.3 emu/g, resistivity = 2.51 mΩ cm, total loss = 593.1 kW/m³ at 10 mT and 100 kHz; 18.0% reduction from the maximum). Thus, a precise method of adjusting the magnetic behaviour of Fe–Si–Al based SMPCs was developed through the novel approach of building SMPCs with inorganic ceramic insulating layers, enabling a comprehensive understanding of the relationship between the thickness of insulating layers and magnetic properties, which is of significance for industrial production.     

Ultra-low core loss FeSiAl soft magnetic composites with in-situ double oxidation layers of outer Fe3O4 layer and inner super-thin Al2O3/SiO2 hybrid layer

How to synchronously reduce eddy current loss and hysteresis loss still remains a challenge for achieving low core loss of soft magnetic composite (SMC). In-situ surface oxide effectively combines the formation of insulating layer and the release of internal stress during the molding process. In this study, FeSiAl SMC has been fabricated by powder metallurgy method with in-situ oxidated FeSiAl powder, in which FeSiAl powder are covered by outer Fe₃O₄ insulating layer and inter super-thin Al₂O₃/SiO₂ hybrid layer. Fe₃O₄ layer alleviates dilution magnetic effect, ensuring high saturated magnetization and effective permeability. The super-thin Al₂O₃/SiO₂ hybrid layer enhances electrical resistance, reducing eddy loss. Effects of the in-situ oxidation time on insulating layer and soft magnetic performances of SMC are investigated in detail. Synchronous reduction of eddy current loss and hysteresis loss is achieved through high resistance accompanied with proper insulating layer thickness and low coercive force provided by the special microstructure. For powder with 90 min oxidation at 500 °C, core loss of SMC is low up to 64 mW/cm³ at 50 mT and 100 kHz and 363 mW/cm³ at 100 mT and 100 kHz, while the permeability is kept at 50 until 1100 kHz and is stable until 140 °C. Meanwhile, DC bias performance reaches 51.2% at 100 Oe applied field and Q value is 104.8 at 400 kHz.     

Enhancement in magnetic permeability of Ni-Co-Zn ferrites using CuO doping for RF and microwave devices

Novel soft magnetic ferrite materials will play a crucial role in next-generation trillion-dollar sensor technologies related to 5G communications and internet of things as these materials can achieve improved wireless power/signal transfer efficiency with high operation frequency. In this work, Ni_0.4Co_0.25Zn_0.35Fe₂O₄ ferrites with high permeability and low magnetic loss were prepared for RF and microwave device applications. Composition and microstructure control is crucial to obtain the desired magnetic and loss properties. CuO dopant (x = 0 wt% to 20 wt%) were employed during the synthesis of Ni_0.4Co_0.25Zn_0.35Fe₂O₄ ferrite specimens to modify the microstructures, thus improving the magnetic properties of the ferrites. High value of measured relative permeability (μ’ of 4-10) and relatively low magnetic loss tangent ( of 0.01-0.1) has been achieved at frequency range between 100 and 800 MHz. Addition of CuO, especially up to 3 wt%, can cause a significant increase in permeability. Real part of the permeability of 3.87 and 10.9 has been achieved for undoped and 3 wt% CuO doped specimens, while noticeable reduction in magnetic losses has been observed for the doped sample measured at 400 MHz. The resonance frequency of synthesized ferrites has also been shifted into GHz range, when higher concentration of CuO dopants (>5 wt%) were employed.     

Effects of Ni coating thickness on the microstructure and mechanical properties of resistance-welded WC-Co/B318 steel joints

WC-Co pellets electroplated with different Ni coating thicknesses and B318 steel were resistance welded for carbide-tipped saw blade applications. The effects of the Ni coating thickness on the welding process, interfacial microstructures, and mechanical properties of the joints were investigated. The results showed that the shear force increased before decreasing as the Ni coating thickness increased. When the coating thickness was 40 μm, expulsions began to appear during welding, while a thicker coating resulted in longer expulsion times. Voids and macro cracks were generated at the joints because of the expulsions, which reduced the shear force of the joint. The XRD results of the welding slag and the EDS results of the interface indicate that the microstructures can be divided into five phase categories: light gray (Fe₃W₃C), gray (Co₃W₃C), white (WC), fishbone eutectic structure (Fe₆W₆C), and dark [(γ Fe, Ni) solid solutions]. As a thicker Ni coating hinders reactions between molten Fe and dissolved WC, the joint interface contained more Fe₆W₆C at 20 μm and 30 μm but had more bulk Fe₃W₃C at 40 μm and 50 μm. The upper part of the joint showed brittle fractures on the WC-Co side, while most of the lower part fractured at the interface. Only the joints at 20 μm and 30 μm had a small fracture area on the steel side. Moreover, the fracture on the steel side at 30 μm showed elongated shear dimples, which explains the maximum shear force of the joint at 30 μm.     

Properties of alumina coatings prepared on silica-based ceramic substrate by plasma spraying and sol-gel dipping methods

Silica-based ceramic cores are widely used in the manufacturing of hollow, nickel-based, superalloy turbine blades. However, elemental Hf, Ti, Al, and other active metals in the superalloy can react with silica-based ceramic cores during casting, resulting in a reduction in the quality of the turbine blades. In this study, both plasma spraying and sol-gel dipping methods were used to prepare alumina coatings on silica-based ceramic substrates to prevent the interfacial reaction. The performance of the alumina coatings prepared by both methods was evaluated by comparative analysis of the surface roughness, bonding interface morphologies, and the adhesive characteristics of the coating. The plasma-sprayed alumina coating has a roughness greater than 5 μm and peeled away from the substrate due to the difference in thermal expansion between SiO₂ and Al₂O₃ at temperatures above 1500 °C, rendering the silica-based substrate with the plasma-sprayed alumina coating unfit for the application requirements of the casting process. The alumina coating prepared by the sol-gel dipping method improved the roughness of the substrate from Ra 2.39 μm to Ra 1.83 μm, and no peeling was observed when heated to 1550 °C for 30 min due to the pinning characteristics of the coating on the substrate. Furthermore, the interfacial reaction between the DZ125 superalloy melt and the silica-based substrate coated with alumina by sol-gel dipping method were investigated. The alumina coating effectively inhibited the interfacial reaction and no reaction products were detected during the directional solidification with pouring temperature of 1550 °C and withdraw rate of 5 mm/min. While a uniform, 4–5 μm thick HfO₂ reaction layer formed between the uncoated substrate and the DZ125 alloy melt. Two dipping-drying cycles were required to ensure the alumina sol completely covered the surface of the substrate.     

Design and preparation of low-filled magnetic oriented BN@Fe3O4/EP insulating composite with improved thermal conductivity and thermal stability

As an excellent two-dimensional insulating material with high thermal conductivity, high temperature stability and high hardness, hexagonal boron nitride(h-BN) is widely applied in semiconductor manufacturing, aerospace, metallurgical manufacturing and other cutting-edge fields. However, the unique surface structure of h-BN leads to poor lubricity and easy agglomeration, which limits the application of h-BN especially in the field of electronic packaging. To address key issues boosted above, this study designed and prepared the BN@Fe₃O₄ magnetic insulating particles and doped it into the reduced viscosity epoxy resin to prepare the composites. By selecting appropriate external magnetic field strength and BN@Fe₃O₄ particles’ content, a novel 3D structure of fillers like dominoes in epoxy resin composite was successfully constructed. The microstructure of the BN@Fe₃O₄ particles and composites were analyzed, the thermal conductivity, the mechanical and the electrical properties of composites were simultaneously tested. Results manifested that the core-shell structures with BN as core and Fe₃O₄ as shell was successfully prepared, linking through the PDA middle layer between the BN core and Fe₃O₄ shell. Under the influence of magnetic orientation, the BN@Fe₃O₄ magnetic particles were preferred an out-of-plane oriented in the epoxy resin composites, resulted an enormously enhanced on thermal conductivity of composites. At a magnetic field strength of 60 mT and 25 vol% BN@Fe₃O₄ content, the thermal conductivity of BN@Fe₃O₄/EP composites is as lofty as 1.832 W/(m K), which is 1023.46% higher than that of pure epoxy resin. Meanwhile, the thermal stability has also been slightly improved, the elastic modulus and insulation performances remain at the same level.     

Effect of CrSi2 on the ablation resistance of a ZrSi2-Y2O3/SiC coating prepared by SAPS

To improve the ablation resistance of carbon/carbon (C/C) composites, a proportional amount of ZrSi₂-CrSi₂-Y₂O₃ mixed particles were deposited on the surface of SiC-coated C/C composites by supersonic air plasma spraying (SAPS) to form a ZrSi₂-CrSi₂-Y₂O₃/SiC coating. The microstructure and phase compositions of the coating were studied by SEM, EDS, XRD and its anti-ablation performance was tested by oxyacetylene torch. The experimental results showed that the ZrSi₂-CrSi₂-Y₂O₃ outer coating had a dense microstructure without obvious pores and microcracks, and the thickness reached approximately 150 μm. In the process of being eroded and scoured by the oxyacetylene flame, the coating exhibited excellent anti-ablation property, which was attributed to the mosaic microstructure formed by ZrO₂ and a Si-O-Cr liquid film on the coating surface. After experiencing an ablation time of 80 s, the linear ablation rate and the mass ablation rate of the coating were -1.0 ± 0.03 μm s^-1 and -0.16 ± 0.014 mg s^-1, respectively.     

Magnetic properties of PAN-based carbon fibres modified with magnetite nanoparticles

The magnetic properties of PAN-based carbon fibres modified with magnetite nanoparticles are presented and analyzed. PAN fibres and PAN-based carbon fibres modified with different amounts of magnetite are characterized by the use of magnetization measurements and Mössbauer spectroscopy techniques. The investigations revealed that magnetite (Fe₃O₄) decomposed into Fe_α, Fe_γ and cementite (Fe₃C). Precise analysis of the phase’s contents for different carbon fibres has been carried out in relation to the initial magnetite compound. Analysis of the Mössbauer spectra allowed the determination of the phase contents in fibres with different initial magnetite concentrations. Partial transformation of magnetite into γ-Fe induces catalytic carbonization and formation of a highly crystalline carbon matrix at 1000 °C. The apparent crystallite size in carbon fibres containing 30% magnetite was almost seven times higher than that found in the pure carbon fibres.     

Electromagnetic interference shielding effectiveness of hybrid multifunctional Fe3O4/carbon nanofiber composite

Electromagnetic interference shielding effectiveness (EMI SE) of multifunctional Fe₃O₄/carbon nanofiber composites in the X-band region (8.2–12.4 GHz) is studied. Here, we examine the contributing effects of various parameters such as Fe₃O₄ content, carbonization temperature and thickness on total shielding efficiency (SE_total) of different samples. The maximum EMI SE of 67.9 dB is obtained for composite of 5 wt.% Fe₃O₄ (0.7 mm thick) with the dominant shielding by absorption (SE_A) of electromagnetic radiation. The enhanced electromagnetic shielding performance of Fe₃O₄/carbon nanofiber composites is attributed to the increment of both magnetic and dielectric losses due to the incorporation of magnetite nanofiller (Fe₃O₄) in electrically conducting carbon nanofiber matrix as well as the specific nanofibrous structure of carbon nanofiber mats, which forms a higher aspect ratio structure with randomly aligned nanofibers. Furthermore, we prove that the addition of elastomeric polydimethylsiloxane (PDMS) as a coating for carbon nanofiber composite strengthens the composite structure without interfering with its electromagnetic shielding efficiency.     

High-strength superparamagnetic composite fibers

The polymer composites of magnetic nanoparticles can be possibly used in a bulk form by preserving all the novel characteristics of magnetic nanoparticles such as superparamagnetic behavior. By introducing magnetic properties of Fe₃O₄ nanoparticles into polymer fibers, novel magnetic properties combine with the advantages of composite fibers such as light-weight and ease-of-use. Using dry-jet-wet fiber spinning technology, we have successfully fabricated iron oxide/polyacrylonitrile (Fe₃O₄/PAN) composite fibers with 10 wt% nanoparticle in the polymer matrix. Composite fiber with a diameter as small as 15 μm can achieve tensile strength and tensile modulus values as high as 630 MPa and 16 GPa, respectively. Superparamagnetic properties of Fe₃O₄ nanoparticles were preserved in the composite fibers with saturation magnetization at 80 emu/g and coercivity of 165 G.     

Magnetic and Dielectric Properties of YIG/HDPE Composites for High-Frequency Applications

A low loss high-frequency magnetic composite with Y₃Fe₅O₁₂ (YIG) ultrafine particles embedded in a high-density polyethylene (HDPE) matrix was fabricated by using a simple low-temperature hot-pressing technique. The magnetic and dielectric properties of the as-prepared composites were investigated in detail. The results indicate that as the volume of the ceramic fillers increases, the permittivity, permeability, dielectric and magnetic loss of the composite all increase. The cut-off frequencies of the composites are all above 700 MHz. Since the low resistivity of YIG, the dielectric losses of the composites are high and decrease with frequency in the lower frequency range. Good frequency stability of the permittivities and permeabilities, and low dielectric and magnetic losses within the measurement range have been observed.     

Synthesis of magneto-dielectric coatings in electron-beam produced plasma in medium vacuum

Using sequential electron-beam evaporation of high-temperature dielectric (alumina ceramic) and magnetic (iron) targets in various gas atmospheres (helium, air, and oxygen) in medium vacuum (5–8 Pa), magneto-dielectric coatings with thickness of around 2 μm were deposited from a multicomponent beam plasma at a deposition rate of 0.2–0.3 μm/min. The coating magnetic properties were explored by the ferromagnetic resonance technique, revealing that their effective magnetization depends on the type of operating gas and varied from 4.2 to 6.8 kGs (for deposition in helium) to 0.3 kGs (in oxygen), which is characteristic of oxide ferromagnetic materials and is considerably lower than the corresponding value (∼22 kGs) for thin iron films formed by vacuum arc deposition in high vacuum. X-ray structural analysis of coatings deposited in medium vacuum in helium showed that the magnetic layer has a magnetite (Fe₃O₄) structure. The alumina ceramic layer provides the dielectric properties of the magneto-dielectric coating; a relative dielectric constant of 6.0 and a conductivity of 8.4 mS/m were achieved.     

Magnetodielectric response of composites based on a natural garnet and spinel ferrites for sub-GHz wireless applications

A natural garnet with excellent dielectric properties was mixed with different weight percentages of two spinel ferrites, Ni_0.5Zn_0.5Fe₂O₄ (NZO) and LiFe₅O₈ (LFO) to tailor its magnetodilectric properties. 3 wt% B₂O₃ was added to enhance the density of the composites. X-ray diffraction study revealed the decomposition of the mineral into hematite and cordierite and vibrational spectroscopic analysis confirmed the non-reactivity of decomposed mineral with spinel ferrites. Microstructural analysis shows well densified and almost tightly packed grains for garnet-Ni_0.5Zn_0.5Fe₂O₄ (G-N) and garnet-LiFe₅O₈ (G-L) composites. The optimised dielectric and magnetic properties of 0.5 G-0.5 NZO are ε_r = 4.1, μ_r = 1.8, tan δ_ε = 0.02, tan δ_μ = 0.49, whereas that of 0.5 G–0.5 LFO are ε_r = 4.4, μ_r = 1.4, tan δ_ε = 0.001, tan δ_μ = 0.05 at 1 GHz. Due to the moderate permittivity of garnet, a better impedance matching compared to magnetodielectric composites based on high-permittivity dielectric counterparts is observed. Hence, the present study indicates that G-N and G-L composites are potential candidates for sub-gigahertz wireless applications.     

TaB2–SiC–Si multiphase oxidation protective coating for SiC-coated carbon/carbon composites

To improve the oxidation resistance of the carbon/carbon (C/C) composites, a TaB₂–SiC–Si multiphase oxidation protective ceramic coating was prepared on the surface of SiC coated C/C composites by pack cementation. Results showed that the outer multiphase coating was mainly composed of TaB₂, SiC and Si. The multilayer coating is about 200 μm in thickness, which has no penetration crack or big hole. The coating could protect C/C from oxidation for 300 h with only 0.26 × 10^?2 g²/cm² mass loss at 1773 K in air. The formed silicate glass layer containing SiO₂ and tantalum oxides can not only seal the defects in the coating, but also reduce oxygen diffusion rates, thus improving the oxidation resistance.     

Study on orientation in EVA/Fe3O4 composite hot-melt adhesives

EVA hot melt adhesives have tackiness to both external anticorrosion coating made by cross-linked polyethylene and iron-base petroleum pipeline. But, traditional EVA hot melt adhesives cannot meet the requirement of external anticorrosion coating for weaker tackiness. Two types of Fe₃O₄ particles with different particle sizes and magnetic strengths were added in adhesives. One is of 3.665 μm^{Laser particle size analyzer (LPSA)} and 8.403×10¹ emu/g^{vibrating sample magnetometer (VSM)} and the other one is of 0.426 μm^LPSA and 3.997×10¹ emu/g^VSM. The result of peel test indicated that peel strength of composite adhesives increased as Fe₃O₄ content increased when particles size was 3.665 μm^LPSA but the tackiness of composite adhesive decreased as Fe₃O₄ content increased when particles size was 0.426 μm^LPSA. Also, microphotos of SEM revealed that the composite adhesive with 3.665 μm^LPSA Fe₃O₄ was more likely to distribute in a region near the tackiness surface between the adhesive and iron layers, but the one with 0.426 μm^LPSA Fe₃O₄ was more likely to aggregate in the middle region of adhesive. The movement of 3.665 μm^LPSA Fe₃O₄ particles could induce EVA molar chain orientation and this orientation was confirmed by infrared dichroism and XRD. Results of infrared dichroism and XRD showed that the orientation degree of EVA increased as 3.665 μm^LPSA Fe₃O₄ content increased. Furthermore, crystallinity tests by XRD and DSC indicated that crystallinity of PE segment of EVA also increased as 3.665 μm^LPSA Fe₃O₄ content increased, which could support increase of orientation tested by infrared dichroism and XRD.     

An architectural approach to the oxygen permeability of a La0.6Sr0.4Fe0.9Ga0.1O3−δ perovskite membrane

Multilayer membranes based on La_0.6Sr_0.4Fe_0.9Ga_0.1O_3−δ (LSFG) and La_0.6Sr_0.4Co_0.8Fe_0.2O_3−δ (LSCF) perovskite materials were fabricated to study the impact of membrane architecture on the oxygen permeability. Thick dense membrane and asymmetric membranes were shaped by tape casting and stacked to reach the desired architecture. Asymmetric membranes composed of a thin dense LSFG layer (120 μm) and a thick porous support layer (820 μm) of the same material were co-sintered to obtain crack-free and flat membranes. The use of large corn-starch particles (14 μm) as pore forming agent to the tape-casting slurries resulted in a connected porosity in the sintered support layer with low gas diffusion resistance. Oxygen permeation measurements in an air/argon gradient between 800 and 925 °C showed that the thickness of self-supported LSFG membranes was not the determining factor in the membrane performance for our testing conditions. A catalytic layer of La_0.6Sr_0.4Co_0.8Fe_0.2O_3−δ (LSCF), deposited on the membrane surfaces to catalyze the oxygen exchange reactions, leads to a significant increase of oxygen permeation rates. As the membrane thickness had no effect even if a catalyst coating was used, surface-exchange reactions were thought to be still limiting for the oxygen permeation fluxes. Thus, the improvement of surface activity of LSFG membrane was found to be a key point to reach higher oxygen permeation fluxes.