An XPS investigation on the thermal stability of the insulating surface layer of soft magnetic composite powder

Unlocking iron metal as a cathode for sustainable Li-ion batteries by an anion solid solution

Traditional cathode chemistry of Li-ion batteries relies on the transport of Li-ions within the solid structures, with the transition metal ions and anions acting as the static components. Here, we demonstrate that a solid solution of F- and PO43- facilitates the reversible conversion of a fine mixture of iron powder, LiF, and Li3PO4 into iron salts. Notably, in its fully lithiated state, we use commercial iron metal powder in this cathode, departing from electrodes that begin with iron salts, such as FeF3. Our results show that Fe-cations and anions of F- and PO43- act as charge carriers in addition to Li-ions during the conversion from iron metal to a solid solution of iron salts. This composite electrode delivers a reversible capacity of up to 368 mAh/g and a specific energy of 940 Wh/kg. Our study underscores the potential of amorphous composites comprising lithium salts as high-energy battery electrodes.

Optimizing FeSiCr-Based Soft Magnetic Composites Using the Deionized Water as the Phosphating Solvent

To prepare a soft magnetic powder core, the magnetic powder surface has to be insulated by phosphating treatment. Organic chemicals such as ethanol and acetone are generally used as solvents for phosphoric acid, which may cause serious environmental problems. This work proposed deionized water as the environmentally friendly phosphating solvent for FeSiCr powder. The soft magnetic composites (SMCs) were prepared using phosphoric acid for inorganic coating and modified silicon polymer for organic coating. The effect of different phosphating solvents, including deionized water, ethanol, and acetone, on the structure and magnetic properties of SMCs were investigated. It is found that the solvent affects the phosphating solution's stability and the phosphoric acid's ionization. The phosphoric acid is more stable in deionized water than in ethanol and acetone. The phosphating reaction in deionized water is also more stable in deionized water, resulting in a dense phosphate coating on the particle surface. The effects of phosphoric acid concentration and temperature on the magnetic properties of FeSiCr-based SMCs were further studied. With the increase in phosphoric acid concentration and temperature, the magnetic permeability and saturation magnetization of the powder core decrease, and the core loss decreases, followed by an increase. The optimized combination of properties was obtained for the SMCs phosphated with 0.2 wt.% phosphoric acid in deionized water at 35 °C, including a high effective permeability μe of 25.7, high quality factor Q of 80.2, low core loss Pcv of 709.5 mW/cm3 measured at 0.05 T @ 100 kHz, and high withstanding voltage of 276 V, due to the formation of uniform and dense insulating coating layers. In addition, the SMCs prepared with phosphated powder show good corrosion resistance. The anti-corrosion properties of the SMCs using deionized water as a phosphating solvent are better than those using ethanol and acetone.

Surface Modification of ZnO Nanocrystals with Conjugated Polyelectrolytes Carrying Different Counterions for Inverted Perovskite Light-Emitting Diodes

In this work, bromide ions (Br^-) on the conjugated polyelectrolytes (CPEs) were converted to tetrafluoroborate (BF₄^-) or hexafluorophosphate (PF₆^-) ions through anion exchange. The three CPEs (PFN-Br, PFN-BF₄, and PFN-PF₆) were utilized solely for surface modification of zinc oxide nanocrystals (ZnO NCs). The ionic groups on CPEs can form permanent dipoles to facilitate charge injection from ZnO NCs to cesium lead bromide (CsPbBr₃) NC emitters, therefore promoting luminescent properties of inverted perovskite light-emitting diodes (PeLEDs). The experimental results reveal that ZnO NC films were smoothened by CPEs that allowed flat deposition of the perovskite active layers; moreover, the improved contact between ZnO and perovskite layers was beneficial for reducing leakage current, as verified in the dark current measurement of devices. In addition, the incorporation of CPEs helped to passivate the defects of ZnO NC films and prolong the carrier lifetime of CsPbBr₃ NCs. PeLEDs based on different CPEs were then constructed and evaluated. The device based on PFN-Br showed the highest brightness and current efficiency, and the one based on PFN-BF₄ exhibited better current efficiency over PFN-Br under the low current density below 160 mA/cm². This is the first report using fluorene-based CPEs with Br^-, BF₄^-, or PF₆^- groups to modify the properties of ZnO and CsPbBr₃ NCs for the construction of inverted PeLEDs so far. Our experiments explored new kinds of CPEs on the surface modification of ZnO NCs and device performance of PeLEDs.

The effectiveness and adsorption mechanism of iron-carbon nanotube composites for removing phosphate from aqueous environments

This study successfully employed iron-carbon nanotubes (Fe-CNT) to recover phosphate (P) from water. We examined the effects of various iron concentrations denoted by Fe-CNT-1 and Fe-CNT-2 on P removal and compared them with pristine carbon nanotubes (CNTs). The adsorption capacity of Fe-CNTs was much better than pristine CNTs. According to the high adsorption capacity, Fe-CNT-2 sample was very effective for P recovery and exhibits ∼7 times higher P removal efficiency than that of pristine CNTs. The characterization of the as-obtained adsorbent (Fe-CNT-2) and pristine CNTs were performed using X-ray diffraction, Brunauer-Emmett-Teller method, Field emission scanning electron microscope coupled with energy-dispersive spectroscopy detector (FESEM-EDS), X-ray photoelectron spectroscopy and Transmission electron microscopy. Results demonstrated that iron oxide nanoparticles were successfully deposited on the surface of CNT. The adsorption kinetics and isotherm studies for P removal showed pseudo-second-order rate constants (R² > 0.99) and the Langmuir isotherm (R² > 0.99) respectively, thus revealing that the nature of adsorption was chemisorption. The estimated Langmuir adsorption capacity of Fe-CNT-2 was 36.5 mgP/g or 112 mg PO₄/g at an equilibrium time of 3 h. The ionic strength provided by SO₄^2-, NO₃^-, and Cl^- demonstrated no considerable influence on phosphate adsorption. Moreover, the P adsorbed Fe-CNT-2 was efficiently recovered with different concentrations of desorbing reagents, such as NaOH and NaCO₃^2-. Moreover, the findings of X-ray photoelectron spectroscopy (XPS) analysis demonstrated that OH group played a major role in the P removal by Fe-CNT-2. The findings of this study demonstrate that Fe-CNT-2 had a great deal of application as an effective and stable adsorbent for the P recovery from aquatic environments.

Effect of the Temperature on the Magnetic and Energetic Properties of Soft Magnetic Composite Materials

In recent years, innovative magnetic materials have been introduced in the field of electrical machines. In the ambit of soft magnetic materials, laminated steels guarantee good robustness and high magnetic performance but, in some high-frequency applications, can be replaced by Soft Magnetic Composite (SMC) materials. SMC materials allow us to reduce the eddy currents and to design innovative 3D magnetic circuits. In general, SMCs are characterized at room temperature, but as electrical machines operate at high temperature (around 100 °C), an investigation analysis of the temperature effect has been carried out on these materials; in particular, three SMC samples with different binder percentages and process parameters have been considered for magnetic and energetic characterization.

Granulation of drinking water treatment residuals as applicable media for phosphorus removal

Recycling drinking water treatment residuals (DWTR) show promise as a strategy for phosphorus (P) removal; however, powdered DWTR is not an ideal practical medium due to clogging. This study granulates DWTR by entrapping powdered DWTR in alginate beads. Results show that granular DWTR has an appreciable amount of mesopores along with a Brunauer-Emmett-Teller (BET) surface area of 43.8 m²/g and total pore volume of 0.049 cm³/g. Most metals (e.g., Al, Ba, Be, Cd, Co, Cr, Mn, Ni, Pb, and Zn) in granular DWTR became more stable and granular DWTR could be considered non-hazardous material. Further analysis indicates that the granular DWTR has strong P adsorption capability with a maximum adsorption capacity of 19.70 mg/g as estimated by the Langmuir model. Good P adsorption may be attributed to the formation of Fe-PO₄ and Al-PO₄ associated with the amorphous state of enormous iron and aluminum in granular DWTR. More importantly, granular DWTR exhibits good mechanical stability and maintained its shape with weight loss below 12.49% after three recycling rounds. Overall, granular DWTR appears to serve as better media for phosphorus removal in water treatment structures such as wetlands.