Liquid Phase Reduction Method Research Articles

Degradation kinetics, influencing factors, and mechanisms of polycyclic aromatic hydrocarbons in a Fe3O4-nZVI Fenton-like system

To improve the catalytic performance of nano zero-valent iron (nZVI) in a Fenton-like system, Fe3O4 supported nZVI (Fe3O4-nZVI) was produced by the liquid-phase reduction method and co-precipitation method, then characterized by SEM, EDS, XRD, XPS, and VSM. Fe3O4-nZVI was used as the catalyst in a Fenton-like system to degrade polycyclic aromatic hydrocarbons (PAHs) such as naphthalene (Nap), phenanthrene (Phe), and pyrene (Pyr) in simulated wastewater. The results showed that under the optimization conditions, which were 25℃, 0.6g/L of Fe3O4-nZVI dosage, 3 of the pH in the reaction system, and 10-15mmol/L of the concentration of H2O2, the sequence of degradation efficiency in this system was Phe (99.76%)>Pyr (99.71%)>Nap (98.01%). The reused experiments on Fe3O4-nZVI showed that the degradation efficiency for PAHs remained above 87% after 4 reuses of Fe3O4-nZVI. These results indicated that nanoscale magnetic composites of Fe3O4-nZVI had excellent reactivity, stability, and reuse performance. The fitting parameters of kinetics showed that the degradation of PAHs in the Fenton-like system with the Fe3O4-nZVI catalyst fitted well with the Behnajady-Modirshahla-Ghanbery kinetic model. The radial quenching experiment proved that ·OH was the dominant free radical for the degradation of PAHs in the Fe3O4-nZVI Fenton-like system. Based on the degradation products of PAHs and the related literature, the possible degradation paths of the three PAHs in the Fe3O4-nZVI Fenton-like system were inferred. The above results could provide a reference and basis for the treatment of wastewater containing PAHs by Fe3O4-nZVI Fenton-like technology.

Synthesis of uniform spherical silver powder without dispersants in a confined impinging-jet reactor

Sliver powder is the most common and extensively utilized precious metal powder in electronics, primarily for electronic paste. Herein, micron-sized spherical silver powder was synthesized via a liquid phase reduction method employing silver nitrate as the source of silver and ascorbic acid as the reducing agent in a confined impinging jet reactor (CIJR). The impact of the molar ratio between silver nitrate and ascorbic acid, the flow rate, and the temperature on the particle size of silver powder was investigated. The optimal process conditions for silver powder are as follows: maintain a molar ratio of 1:1 and control the feeding rate at 10ml/min while operating at 50 ° C. The confined impinging jet reactor offers enhanced control over reaction conditions during the synthesis of silver powder, surpassing the capabilities of traditional batch reactors. The aforementioned optimized methodology was employed to successfully synthesize uniform and spherical silver powder (with an aspect ratio approaching 1) in the low Reynolds number jet, resulting in an average particle size of d50 = 0.83 μm and a standard deviation of 0.07, without the addition of dispersant. The synthesis method presented here improves the performance of silver powder, simplifies the production process, reduces energy consumption, and minimizes waste generation. These advances yield significant environmental and economic benefits. In the future, with the continuous development and optimization of microreactor technology, this synthesis method is anticipated to play a more prominent role in the commercial-scale production and application of micrometer-sized silver powder.

Effect of pH on the fabrication of lauric acid/Ag phase change nanocapsules via liquid-phase reduction

Phase change nanocapsules can be dispersed in fluids to form latant functional thermal fluids (LFTFs), which can serve as effective coolants for extending the lifespan of electronic devices. For this purpose, it is significant to prepare phase change capsules that possess excellent heat storage capacity, thermal conductivity, and suspension stability. In this paper, lauric acid/silver composite phase change nanocapsules were prepared by liquid-phase reduction method. To investigate the effect of pH value on capsule synthesis, six phase change capsule samples were prepared between pH values of 2.6–4.6. The results indicate that the prepared nanocapsules exhibited good heat storage capacity and thermal conductivity under different pH values. However, as pH increases, the silver shell thickness on the nanocapsule surface initially decreases and subsequently increases. The silver shell thickness of L3 is the thinnest, measuring 12.5 nm. Correspondingly, the enthalpy and volume encapsulation rate of the phase change capsules first increase and then decrease. The lauric acid/Ag nanocapsules possess a thermal conductivity in the 1.77–4.32 W/(m∙K) range. Further, it is found that pH affects the formation of silver shell on the surface of lauric acid/Ag phase change nanocapsules by influencing the electrostatic interactions between particles, and diffusion in the system, which explains the variation of silver shell thickness with pH value for the six capsule samples. We also found that the thinner the silver shell of the nanocapsules, the more advantageous it is to reduce the density of the capsules, thereby improving their suspension. Therefore, controlling the pH value during the preparation to obtain lauric acid/Ag phase change nanocapsules with thin silver shell thickness plays an important role in improving the overall performance of phase change nanocapsules used for preparing latent functionally thermal fluid.

Pd Nanoparticles Loaded on Cu Nanoplate Sensor for Ultrasensitive Detection of Dopamine.

The detection of dopamine is of great significance for human health. Herein, Pd nanoparticles were loaded on Cu nanoplates (Pd/Cu NPTs) by a novel liquid phase reduction method. A novel dopamine (DA) electrochemical sensor based on the Pd NPs/Cu/glass carbon electrode (Pd/Cu NPTs/GCE) was constructed. This sensor showed a wide linear range of 0.047 mM to 1.122 mM and a low limit of detection (LOD) of 0.1045 μM (S/N = 3) for DA. The improved performance of this sensor is attributed to the obtained tiny Pd nanoparticles which increase the catalytic active sites and electrochemical active surface areas (ECSAs). Moreover, the larger surface area of two-dimensional Cu nanoplates can load more Pd nanoparticles, which is another reason to improve performance. The Pd/Cu NPTs/GCE sensor also showed a good reproducibility, stability, and excellent anti-interference ability.

Data-driven designed low Pt loading PtFeCoNiMnGa nano high entropy alloy with high catalytic activity for Zn-air batteries

Developing low Pt loading and high-activity oxygen electrocatalysts is necessary to promote large-scale fuel cell applications. By data-driven and density functional theory calculations, PtFeCoNiMnGa nano high entropy alloy (HEA) was synthesized through liquid-phase reduction and H2 calcination method and loaded on carbon nano-tube (CNT). Due to high entropy, electronic modulation, and cocktail effects, PtFeCoNiMnGa HEA catalyst shows great catalytic activity in oxygen evolution/reduction reaction (OER/ORR). The PtFeCoNiMnGa/CNT showed a low overpotential of 243 mV for OER, and for ORR a mass activity of 1.12 A mgPt−1 (5.3 times than Pt/C). Moreover, the PtFeCoNiMnGa/CNT showed high durability by maintaining 95 % of its initial performance for up to 50 h. In addition, the zinc-air battery assembled with PtFeCoNiMnGa/CNT as the cathode catalyst had an open-circuit potential of 1.52 V and an energy density of 130.6 mW cm−2, and was able to operate stably for 120 h without any significant degradation.

Degradation Efficiency and Mechanism of Tetracycline in Water by Activated Persulfate Using Biochar-Loaded Nano Zero-Valent Iron.

Tetracycline (TC) contamination in water is one of the key issues in global environmental protection, and traditional water treatment methods are difficult to remove antibiotic pollutants.Therefore, efficient and environmentally friendly treatment technologies are urgently needed. In this study, activated persulfate (PS) using a biochar-loaded nano zero-valent iron (BC-nZVI) advanced oxidation system was used to investigate the degradation effect, influencing factors, and mechanism of TC. BC-nZVI was prepared using the liquid-phase reduction method, and its structure and properties were analyzed by various characterization means. The results showed that nZVI was uniformly distributed on the surface or in the pores of BC, forming a stable complex. Degradation experiments showed that the BC-nZVI/PS system could degrade TC up to 99.57% under optimal conditions. The experiments under different conditions revealed that the iron-carbon ratio, dosing amount, PS concentration, and pH value all affected the degradation efficiency. Free radical burst and electron paramagnetic resonance (EPR) experiments confirmed the dominant roles of hydroxyl and sulfate radicals in the degradation process, and LC-MS experiments revealed the multi-step reaction process of TC degradation. This study provides a scientific basis for the efficient treatment of TC pollution in water.

Fabrication of fabric-based piezoresistive sensors based on chemically deposited fabric silver electrodes and PDMS-MWCNTs/CB composite films with thermally expandable microspheres

Optimizing the fabrication process of fabric electrodes and creating active layers with a controlled pore structure is crucial for advancing high-performance flexible pressure sensors. This work proposes an approach to manufacturing fabric-based piezoresistive sensors. Specifically, it utilizes the liquid-phase chemical reduction method with microdroplet jetting technology and the thermally expandable microsphere foaming method. The impact of conductive material filling content and the microsphere expansion process on the active layer performance was investigated. Additionally, the electrical properties of fabric metal silver electrodes were evaluated, along with the sensing capabilities and applications of the sensors. The results reveal that the electrodes exhibit an average sheet resistance of 0.023 Ω sq−1. The sensor displays a sensitivity of 0.21 kPa−1, with a response-recovery time of approximately 300/200 ms and repeatability over 5000 s. Human motion signal tests of the sensor demonstrate its potential in healthcare and sports monitoring applications.

Complexing agent-assisted Cr(VI) removal in a continuous fixed-bed system with nanoscale Fe0/NaA molecular sieve membrane supported on nickel foam

Complexing agents (CAs) can be used for the removal of Cr(VI) via nanoscale Fe0 (nZVI) reduction in cost-effective manner. However, nZVI is prone to aggregation and passivation, and some conventional CAs are toxic and difficult to biodegrade, potentially causing secondary pollution. Therefore, selecting an environmentally friendly CA for assisting in the removal of Cr(VI) via supported nZVI is imperative. Herein, NaA molecular sieve membrane-supported nZVI (nZVI/NaA-NF) was prepared via the secondary growth and liquid-phase reduction method using nickel foam (NF) as the carrier. The physicochemical characteristics of nZVI/NaA-NF before and after reaction were analysed via SEM, EDS, and XPS. A CA-improved nZVI/NaA-NF was used for the effective removal of Cr(VI) in a continuous fixed-bed system. Furthermore, the influences of various experimental factors including the CA type, CA concentration, solution pH, space velocity, and inlet Cr(VI) concentration on Cr(VI) removal were systematically investigated. The results demonstrated that nZVI particles were homogeneously immobilized on the NaA molecular sieve membrane/NF for fresh nZVI/NaA-NF, and tetrasodium iminidisuccinate (IDS-4Na) inhibited the aggregation of Cr(III)/Fe(III) (hydr)oxide precipitates during the reaction. IDS-4Na demonstrated excellent promotive effect on Cr(VI) removal via nZVI/NaA-NF. The breakthrough time for Cr(VI) in the addition of IDS-4Na was considerably longer than that of nZVI/NaA-NF alone. The breakthrough concentration of Cr(VI) only reached 1.1% and 9.9% of the inlet concentration at 220 and 240 min, with an IDS-4Na concentration of 4 mM, a pH of 2.5, and a space velocity of 0.265 min−1. The Bohart–Adams model was appropriate to predict the initial part of Cr(VI) breakthrough curves in the nZVI/NaA-NF fixed bed. The saturated concentration (N0) increased with an increase in inlet Cr(VI) concentration. The Yoon–Nelson model afforded good fitting results for all breakthrough curves of Cr(VI). The k′ value increased with an increase in space velocity, and the τ value decreased.

Ultrafast Fenton-like reaction using a peroxymonosulfate-mediated confined-Fe0 catalyst for the degradation of sulfamethoxazole

Herein, a nanoconfinement strategy was employed to encapsulate nano zero-valent iron (confined-Fe0) for the rapid degradation of sulfamethoxazole (SMX) through a peroxymonosulfate (PMS)-mediated Fenton-like reaction. The confined-Fe0 catalyst was synthesized in situ using a liquid-phase reduction method, incorporating nitrilotriacetic acid (NA) modified carboxylated carbon nanotube (FOC-N-6). Comprehensive experimental analyses and characterizations demonstrated the FOC-N-6 catalyst facilitated rapid electron transfer through the carbon framework and the surface PMS reactive complex (FOC-N-6-PMS*). This process accelerated the Fe(III)/Fe(II) redox cycle and promoted the formation of surface Fe(II) active sites (Fe0-OCNT-COOFe(II)-), which served as dominant adsorption sites for PMS. Density functional theory (DFT) calculations revealed that the confined-Fe0 structure can decrease the adsorption energy (Eads) of PMS on the FOC-N-6 surface. And the FOC-N-6-PMS* facilitated the rapid degradation of SMX through both non-radical and radical pathways. This confined-Fe0 catalytic strategy holds promise as a viable method for controlling emerging contaminants.

Synthesis of bare and modified zerovalent iron nanoparticles and their use in porous polylactic acid composites for methyl orange removal

The main objective of this study was to assess the efficacy of two types of immobilised zerovalent iron nanoparticles (nZVI) incorporated into a porous biopolymer matrix of polylactic acid (PLA) as a novel multifunctional composite system for potential use in dye wastewater treatment. The study involved the preparation of unmodified and 2,6-pyridinedicarboxylic acid (PDCA) modified nZVI material using liquid phase reduction method. Zeta potential measurement and UV-Vis spectrophotometry revealed that the ligand-modified nZVI particles exhibited better dispersion stability in aqueous media than bare particles. SEM-EDS analysis showed a higher oxidation state of the ligand-modified nZVI particles and good dispersion and adhesion of nZVI particles in the mesoporous structure of PLA matrix. The removal efficiency of methyl orange was determined spectrophotometrically where a high efficiency (above 90 %) for high concentration of bare nZVI was detected. Its composites also showed an efficiency of 75 – 100 %. However, modified nZVI showed much lower efficiency, especially after embedding in the PLA matrix.

The Synthesis of Copper Nanoparticles for Printed Electronic Materials Using Liquid Phase Reduction Method.

This text discusses the synthesis of copper nanoparticles via a liquid phase reduction method, using ascorbic acid as a reducing agent and CuSO4·5H2O as the copper source. The synthesized copper nanoparticles are small in size, uniformly distributed, are mostly between 100-200 nm with clear boundaries between particles, and exhibit excellent dispersibility, making them suitable for metal conductive inks. 1. The copper nanoparticles are analyzed for good antioxidation properties, because their surface is coated with PVP and ascorbic acid. This organic layer somewhat isolates the particle surface from contact with air, preventing oxidation, and accounts for about 9% of the total weight. 2. When the prepared copper nanoparticles are spread on a polyimide substrate and sintered at 250 °C for 120 min, the resistivity can be as low as 23.5 μΩ·cm, and at 350 °C for 30 min, the resistivity is only three times that of bulk copper. 3. The prepared conductive ink, printed on a polyimide substrate using a direct writing tool, shows good flexibility before and after sintering. After sintering at 300 °C for 30 min and connecting the pattern to a circuit with a diode lamp, the diode lamp is successfully lit. 4. This method produces copper nanoparticles with small size, good dispersion, and antioxidation capabilities, and the conductive ink prepared from them demonstrates good conductivity after sintering.

Adsorption-coupled Fenton type reduction of bromate in water by high-yield polymer-derived ceramic-supported nano-zerovalent iron

Nano-zerovalent iron (nZVI) is a promising material for the removal of both organic and inorganic pollutants from contaminated water. This study investigates the potential of a novel composite of nZVI on a polymer-derived supporting ceramic (nZVI-PDC) synthesized via the liquid-phase reduction method for the simultaneous adsorption and Fenton-type reduction of bromate anion (BrO3−) in water. The nZVI nanoparticles were effectively anchored onto the PDC by impregnating high-yield carbon in a ferrous sulfate solution. The PDC facilitated the uniform dispersion of nZVI nanoparticles due to its multiple active sites distributed within mesocarbon cavities. The developed nZVI-PDC composite exhibited a high specific surface area of 837 m2 g−1 and an ordered mesoporous structure with a pore volume of 0.37 cm3 g−1. As an adsorbent, the nZVI-PDC composite exhibited a maximum adsorption capacity (qe) of 842 mg g−1 and a partition coefficient (KH) of 10.2 mg g−1 μM−1, as calculated by the pseudo-second-order model. As a catalyst, the composite demonstrated a reaction kinetic rate of 43.5 μmol g−1 h−1 within 6 h at pH 4, using a dosage of 60 mg L−1 nZVI-PDC and a concentration of 0.8 mmol L−1 H2O2. Comparatively, PDC exhibited a qe of 408 mg g−1, KH of 1.67 mg g−1 μM−1, and a reaction rate of 20.8 μmol g−1 h−1, while nZVI showed a qe of 456 mg g−1, KH of 2.30 mg g−1 μM−1, and a reaction rate of 27.2 μmol g−1 h−1. The modelling indicated that the nZVI-PDC composite followed pseudo-second-order kinetics. The remarkable removal efficiency of the nZVI-PDC composite was attributed to the synergistic effects between PDC and nZVI, where PDC facilitated charge transfer, promoting Fe2+ generation and the Fe3+/Fe2+ cycle. Overall, this work introduces a promising adsorption technology for the efficient removal of BrO3− from contaminated aqueous solutions, highlighting the significant potential of the nZVI-PDC composite in water purification applications.

Granular activated carbon supported polyethylene glycol modified nano-zero-valent iron immobilized microbial removal of 2,4-dichlorophenol in water

In recent years, the remediation of 2,4-DCP pollution using immobilized microbial technology has attracted increasing attention. Using granular activated carbon (GAC), polyethylene glycol 4000 (PEG-4000), ferrous sulfate, and sodium borohydride as raw materials, granular activated carbon loaded polyethylene glycol modified nano zero-valent iron composite material (PEG-nZVI/GAC) was prepared via a liquid-phase reduction method. Bacillus marisflavi, capable of degrading phenolic compounds, was immobilized on PEG-nZVI/GAC using an adsorption method to prepare immobilization of microorganisms by granular activated carbon loaded polyethylene glycol modified nano zero-valent iron (PEG-nZVI/GAC@B) for 2,4-DCP removal. Characterization analysis of immobilized microbes was conducted using transmission electron microscopy (TEM) and other methods to determine their physicochemical properties. Response surface methodology (RSM) was employed to optimize the conditions for 2,4-DCP removal, and the performance and mechanism of 2,4-DCP removal by PEG-nZVI/GAC@B were studied. The results indicate that nanoscale zero-valent iron (nZVI) was uniformly distributed in granular activated carbon, Bacillus marisflavi was successfully loaded onto PEG-nZVI/GAC, PEG-nZVI/GAC@B had a higher content of oxygen-containing groups on its surface, and exhibits good dispersibility, stability, and reusability. When the immobilized microbial dosage was 270.32 mg/L, the initial concentration of 2,4-DCP was 50.51 mg/L, and pH was 6.58, the predicted removal rate of 2,4-DCP was 96.53 %. Under these conditions, the actual removal rate of 2,4-DCP was 94.68 %. The removal of 2,4-DCP by PEG-nZVI/GAC@B involved adsorption by granular activated carbon, reductive dechlorination by nanoscale zero-valent iron, and degradation by Bacillus marisflavi. In conclusion, PEG-nZVI/GAC@B is an excellent immobilized microorganism for the removal of 2,4-DCP.

Directional control of electromagnetic parameters of Fe@Ni nanowires for ultrathin and low-frequency microwave absorbing

How to prepare materials according to the target properties has been a hot research topic. In this paper, the target electromagnetic parameters are obtained according to the performance requirements, and the nanoflower rod-like, low-density mulberry-like and high-density mulberry-like one-dimensional (1D) core–shell structured Fe@Ni(x) nanowires (NWs) are prepared by liquid-phase reduction method. The effective absorption bandwidth (EAB) of sample Fe@Ni(40) in the low-frequency (2–8 GHz) is up to 1.89 GHz (3.1 mm). Sample Fe@Ni(60) is able to reach a maximum EAB of 3.18 GHz at a thickness of 0.9 mm. Concisely, the sample has the ability to absorb microwaves in low frequency bands and ultra-thin thicknesses. The reason can be attributed to the strong magnetic coupling brought by the bimetallic composition to strengthen the resonance level and the excellent 1D core–shell structure to enhance the efficiency of polarization loss. In conclusion, Fe@Ni(x) provides a technological route for the preparation of low-frequency and ultra-thin-thickness absorbers.

A new attempt to remove toluene using nickel–iron bimetallic particle electrode reactor

A new attempt of removing toluene waste gas using a three-dimensional electrode reaction device with nickel–iron bimetallic particle electrode is presented in this paper. The particle electrode was prepared by a simple liquid phase reduction method. Through bimetal modification, the particle electrode mass transfer rate is increased to 1.29 times, and the degradation efficiency of the reactor is increased by nearly 40%, which makes it possible to remove toluene waste gas by other electrochemical methods in addition to plasma method. The removal efficiency of the particle electrode can be stabilized at more than 80% after 5 cycles (50 h). At the same time, the relationship between independent working parameters and dependent variables is analyzed using the central composite design, and the operating parameters are optimized. Based on this study, the removal mechanism and possible degradation pathway of toluene were investigated. This study provides a supplement to the possibility and theoretical basis of new technology application for electrocatalytic oxidation removal of VOCs.

Nano zero-valent iron/montmorillonite composite for the removal of Cr(VI) from aqueous solutions: Characterization, performance, and mechanistic insights

Infiltration of hexavalent chromium (Cr(VI)) into the human body poses significant health risks, including the risk of developing cancer and increased mortality rates. The discharge of chromium-contaminated wastewater from industrial processes exacerbates environmental pollution, highlighting the necessity for efficient, cost-effective, and environmentally friendly treatment methods. In recent years, there has been a growing emphasis on the application of nanoscale zero-valent iron particles (NZVI) for mitigating Cr(VI) water pollution. In the present study, NZVI was synthesized using a liquid-phase reduction method employing sodium borohydride (NaBH4), and natural montmorillonite (Mt) was incorporated as a carrier, resulting in the creation of NZVI/Mt., a composite material. Characterization of this composite was performed using scanning electron microscopy (SEM), Transmission Electron Microscope (TEM), Specific surface area and pore size (BET), X-ray diffraction (XRD), and Fourier-transform infrared (FT-IR) techniques. The investigation encompassed an exploration of the influence of initial pollutant pH levels, adsorbent dosages, and initial pollutant concentrations on the adsorption process. The research findings indicate that, at an initial pH of 4.0, NZVI/Mt. achieves a removal efficiency of 92.41% for a Cr(VI) solution with an initial concentration of 40 mg/L. The NZVI/Mt. composite adheres to both a pseudo-second-order kinetic model and the Langmuir isotherm model, showcasing a significant maximum adsorption capacity of 67.75 mg/g for Cr(VI). Furthermore, thermodynamic analysis revealed an exothermic nature of the adsorption process. This experimental approach effectively resolved issues related to NZVI particle agglomeration, offering a simplified, cost-effective, and environmentally friendly preparation method. Consequently, the NZVI/Mt. composite material demonstrates effective treatment of Cr(VI) mildly contaminated wastewater.

Clay minerals modified nickel boride for electrochemical supercapacitor electrode application

Nickel boride has attracted great interest in the field of energy storage due to its superior electrochemical performance, However, particles agglomeration and poor electability have limited its wider application. Clay minerals with high specific surface area and excellent wettability can reduce the agglomeration of particles. We synthesized eight kinds of composites Ni3B@montmorillonite (Ni3B@Mt), Ni3B@chlorite (Ni3B@Chl), Ni3B@vermiculite (Ni3B@Ver), Ni3B@kaolinite (Ni3B@Kaol), Ni3B@palygorskite (Ni3B@Pal), Ni3B@halloysite (Ni3B@Hal), Ni3B@sepiolite (Ni3B@Sep), and Ni3B@talc (Ni3B@Tal) materials with different morphologies and structures by simple liquid phase reduction method. We explored the influence of a series of clay minerals on the electrochemical performance of Ni3B. The results show that the specific capacitance of the Ni3B@clay minerals composites has been improved in different degrees. In addition, the Ni3B@Mt. shows the best specific capacitance of 1406 F g−1 at a current density of 0.5 A g−1, and still maintains a high specific capacitance of 944 F g−1 at a current density of 5 A g−1. The assembled asymmetric supercapacitor Ni3B@Mt.//AC using an activated carbon (AC) and the Ni3B@Mt. showed excellent electrochemical performance with achieving the maximum energy density of 92.60 W h kg−1 at the power density of 350 W kg−1, which suggests the practical application of clay minerals in the electrochemical energy storage field.

A novel Cu@Ag nano paste with low porosity for rapidly sintering in air condition

The emergence of Cu@Ag core-shell nanoparticles presents a promising solution to address issues such as copper oxidation, the high cost of silver, and electro-chemical migration in high-power electronic devices, showcasing their potential for practical applications. In this study, Cu@Ag nanoparticles were synthesized via a liquid-phase reduction method, resulting in an average size of 30 nm. A low-boiling-point mixed organic solvent was meticulously prepared following Raoult's law, enabling the creation of a nano paste utilizing Cu@Ag nanoparticles. This innovation facilitated the sintering of fully dense joints under ambient air conditions, effectively mitigating the oxidation issue caused by silver dewetting behavior in Cu@Ag core-shell nanoparticles. Subsequently, the shear strength and microstructure of the joints were comprehensively studied under various sintering temperatures and durations. Notably, the joint exhibited a shear strength of 17.3 MPa when sintered at 250 °C for 30 min, while achieving full density at a sintering temperature of 300 °C for 30 min. These findings underscore the capacity of Cu@Ag core-shell nano paste to enable the production of high-performance joints under air conditions, utilizing thoughtfully selected organic components.

NiCoCrFeY High Entropy Alloy Nanopowders and Their Soft Magnetic Properties.

High entropy alloy nanopowders were successfully prepared by liquid-phase reduction methods and their applications were preliminarily discussed. The prepared high entropy alloy nanopowders consisted of FeNi alloy spherical powders and NiFeCoCrY alloy spherical powders with a particle size of about 100 nm. The powders have soft magnetic properties, the saturation magnetization field strength were up to 5000 Qe and the saturation magnetization strength Ms was about 17.3 emu/g. The powders have the excellent property of low high-frequency loss in the frequency range of 0.3-8.5 GHz. When the thickness of the powders coating was 5 mm, the powders showed excellent absorption performance in the Ku band; and when the thickness of the powders coating was 10 mm; the powders showed good wave-absorbing performance in the X band. The powders have good moulding, and the powders have large specific surface area, so that the magnetic powder core composites could be prepared under low pressure and without coating insulators, and the magnetic powder cores showed excellent frequency-constant magnetization and magnetic field-constant magnetization characteristics. In the frequency range of 1~100 KHz; the μm of the magnetic powder core heat-treated at 800 °C reached 359, the μe was about 4.6 and the change rate of μe with frequency was less than 1%, meanwhile; the magnetic powder core still maintains constant μe value under the action of the external magnetic field from 0 to 12,000 A/m. The high entropy alloy nanopowders have a broad application prospect in soft magnetic composites.

The Design and Preparation of Permittivity-Adjustable FeNi@SrFe-MOF Composite Powders

When the thickness of the wave-absorbing material is low, there exists the problem of the narrow wave-absorbing frequency band, making it difficult to regulate the position of the wave-absorbing peak. In this study, FeNi@SrFe-MOF composite powders were synthesized using a hydrothermal method and a liquid-phase reduction method. The composite powder was spherical, with a particle size of about 50 μm–60 μm; the core layers of the powders were porous SrFe-MOF powders with permanent magnetization, and the outer layers were FeNi alloy nano-powder coatings with a particle size of 100 nm–120 nm, which took into account both the soft magnetization and the permanent magnetization properties of the composite powders. Additionally, a directional magnetic field was applied to the powder coating. By regulating the intensity and direction of the magnetic field, the electromagnetic parameters of the composite powder coating underwent sensitive changes, allowing for the precise regulation of the electromagnetic wave absorption performance of the composite powders. With the increase in magnetic field intensity, the ε′ value decreased significantly. The ε′ values were 8.56–7.35 for H453mT and 6.73–6.12 for H472mT. When no magnetic field was applied, the Snoke limit frequency of the μ′ value was 6.0 GHz. When the magnetic field intensity increased, the Snoke limit frequency of the μ′ value increased from 6.0 GHz, without the magnetic field, to 8.3 GHz; the Snoke limit of the composite powders was shattered. After the H453mT magnetic field regulation treatment, the powder coating exhibited good impedance matching characteristics with air. When the magnetic field intensity was 453mT and the thickness of the composite powders coating was 3.5 mm, the composite powders coating showed the strongest absorption peak when the R-value was −59 dB at 7.8 GHz, and the effective absorption bandwidth reached 3.2 GHz, exhibiting superb absorbent qualities. The wave absorption property of the coating can be sensitively changed by the magnetic field regulation treatment at the condition without changing the powder structure or coating structure, which provides a new strategy for the regulation of the wave absorption property and has broad application prospects.