Powder Surface Research Articles

Enhancing interfacial kinetics and stability of LiMn2O4 cathode by fabricating an artificial cathode electrolyte interphase of LiNbO3

LiMn2O4 (LMO) cathode material has received continuous attention due to its low price, environmental friendliness, high voltage platform, and high safety. However, the structure distortion is usually caused by the Jahn-Teller effect of Mn3+ in LMO, in which Mn3+ undergoes disproportionation reaction, resulting in the dissolution of Mn element and leading to the problems of fast capacity decay and short cycle life of battery. In this study, a thin (∼3 nm) artificial cathode electrolyte interphase (CEI) of LiNbO3 (LNO) is uniformly covered on the surface of LMO powder (LMO@LNO) by magnetron sputtering method. Compared with the bare LMO, LMO@LNO delivers a higher discharge capacity and better cycling stability. The capacity retention rate of bare LMO/Li cell reaches 80 % in 150 cycles, while LMO@LNO/Li cell can cycle up to 700 cycles, greatly prolonging the cycle life of battery. According to the experimental tests, it is found that the CEI layer of LNO not only improves the interfacial kinetics of electrode, but also inhibits the dissolution of Mn element and side reactions between electrolyte and electrode, thus effectively enhances the rate capability and cycling stability of batteries even at 55 °C and high-voltage of 4.8 V.

Ultrahigh‐Ni Cathode with Superior Structure Stability Enabled by a Covalent Bonding Strategy

AbstractUltrahigh‐nickel layered oxide cathodes are the most promising cathode materials for high‐energy lithium‐ion batteries. However, the rapid structural degradation during cycling charge‐discharge process limits its commercial application. Herein, we report a covalent pinning strategy to enhance structure stability of ultrahigh‐Ni cathode LiNi0.9Co0.06Mn0.04O2 (NCM90). Zr is gradient diffused into the lattice of NCM90 and forms Zr−O bonds during the sintering process, which can effectively alleviate the lattice distortion like introducing pinning centers due to the stronger bond energy, enhancing its structure stability during charge‐discharge process. In the meanwhile, the Zr−O on the surface of NCM90 powder forms LixZryOz coating layer due to the reaction with lithium residue, which prevents from the edge reconstruction and mitigates the occurrence of side reactions, as well as ensuring a fast Li+ diffusion pathway crossing the interface. As a result, the Zr−O modified NCM90 (Zr‐NCM) achieves 88.8 % remarkable capacity retention at 1 C after 200 cycles over 2.8–4.3 V, which is superior to the pristine NCM90 with 71.2 % retention. This work demonstrates that the Zr−O bonding can provide an effective structure pinning for the ultrahigh‐Ni cathode, which will largely guide the development of high‐performance lithium‐ion battery cathode materials.

The role of magnetite for enhancing reduction of N-nitrosodimethylamine by zero-valent iron

Mixed-valent iron mineral has significant effects in redox reaction and engineering applications. Magnetite (Fe3O4) combined with zero-valent iron (ZVI) were chosen to reduce N-nitrosodimethylamine (NDMA). Enhancement had been shown in ZVI-Fe3O4 system than the sum of removals of ZVI and Fe3O4 systems. Lower solution pH value facilitated the removal of NDMA, the concentration of dissolved oxygen (DO) had little effect. The main reduction products of NDMA by ZVI-Fe3O4 were 1,1-dimethylhydrazine (UDMH) and dimethylamine (DMA). The total nitrogen mass was unbalanced. By capturing the active species in the ZVI-Fe3O4 system, active hydrogen atoms had been determined. Catalytic hydrogenation was proposed to be the mechanism. Electrochemical tests showed that ZVI-Fe3O4 had a lower open circuit potential and a higher corrosion current than ZVI, the presence of Fe3O4 promoted the corrosion of ZVI. Scanning electron microscope (SEM) and X-ray diffraction (XRD) analyses of solid powders showed that the corrosion was more serious and no other substances were formed on the surface of powders in ZVI-Fe3O4 system after reaction. X-ray photoelectron spectroscopy (XPS) showed that the value of ratio of peak area of Fe(III) to Fe(II) of ZVI-Fe3O4 surfaces was lowest. The Fe(III) on the powders’ surface could be reduced by ZVI and the surface passivation of ZVI would be prevented, which would be benefit for the generation of active hydrogen atoms.

The mechanochemistry of lanthanum dihydride (LaH\(_{2}\)) with hydrogen (H\(_{2}\)) using the ball-mill process and the effect of oxidation on the resulting products

The complex behavior of LaH2 during ball milling was investigated in this study, with its mechanical, chemical, and morphological changes explored. The relationship between milling time and hydrogen pressure reduction was uncovered through detailed experiments, reflecting the dynamic nature of the process. A transient yet significant event was observed upon unsealing the milling jar post-milling: the emergence of a minor fire ember, indicative of the interplay between mechanical forces and chemical reactivity within the LaH2 powder. Profound changes in the structure, composition, and shape were unraveled using advanced techniques such as X-ray diffraction (XRD), scanning electron microscopy coupled with energy-dispersive X-ray spectroscopy (SEM/EDX), and particle size distribution analysis. The resulting powder exhibited a dual-phase composition of lanthanum dihydride (LaH2, 68.1% to 71.5%) and lanthanum oxide (La2O3, 28.5% to 31.9%), reflecting a dynamic chemical equilibrium during milling. Particle size distribution analysis revealed a notable increase in average diameter to 6420 nm, accompanied by a polydispersity index (PDI) of 0.831, signifying a broadening compared to the initial LaH2 powder. The morphological evolution of the powder was elucidated through SEM imaging, showing predominantly spherical and rounded forms, indicating extensive particle agglomeration and plastic deformation during milling. Additionally, the formation of oxide layers on the powder surface, intertwined with pronounced particle agglomeration, was highlighted through EDX mapping, shedding light on the mechanical aspects of morphological evolution during milling. These findings contribute to our understanding of LaH2 behavior under extreme mechanical and chemical conditions and have implications for materials processing, hydrogen storage technologies, and broader applications in materials science and engineering.

Microstructure and magnetic properties of the FeSiBCuNb nanocrystalline soft magnetic composites coated with oil-phase single Fe3O4 nanoparticles by thermal decomposition method

Here, the core-shell structured FeSiBCuNb/Fe3O4 soft magnetic composites (SMCs) were successfully designed and fabricated by coating Fe3O4 magnetic nanoparticles on the surface of phosphorylated FeSiBCuNb powder. The effects of Fe3O4 and Polyvinylpyrrolidone (PVP) contents on the micromorphology, interface structure, and soft magnetic properties of SMCs were systematically investigated. The results demonstrate that the Fe3O4 magnetic nanoparticles are uniformly distributed on the surface of magnetic powders, which fill up the air gap in-between the magnetic powder and increase the resistivity. It shows that the permeability gradually decreases with the increase of Fe3O4 from 0 wt% to 1 wt%, while the loss decreases first and then increases. The loss separation of SMCs indicates that the Fe3O4 nanoparticles effectively reduce the hysteresis loss and eddy current loss. Furthermore, the FeSiBCuNb/Fe3O4 SMCs with the addition of PVP as a binder enhance the binding force between Fe3O4 nanoparticles and the powder matrix, which facilitates the formation of a uniform and dense interface structure. When adding 0.3 wt% PVP + Fe3O4 nanoparticles, the FeSiBCuNb/Fe3O4 SMCs exhibit excellent soft magnetic properties with ultra-low loss of 138.5 kW/m3 (100 mT/50 kHz), high permeability of 54, and good frequency stability. The presented results provide a new strategy for synthesizing ultra-low core loss and frequency stability of core-shell structured SMCs, which has great potential for applications at high frequencies.

Wet chemical surface functionalization of AA2017 powders for additive manufacturing

Laser Powder Bed Fusion (L-PBF) is an important route for processing aluminum alloys, nevertheless, the high laser reflectivity and thermal conductivity and lower powder flowability of the aluminum alloys remain a challenge for their processing. Aiming to overcome these issues, AA2017 powders were surface-functionalized using chemical etchings. The powders' physical and rheological characterization revealed a decrease in the laser reflectance and an improvement in the flowability of the surface-functionalized powders, when compared to the gas-atomized powder. The higher amount of keyhole porosity in the as-printed L-PBF samples using the surface-functionalized powders also suggests an improvement in the laser absorption of these powders. However, the formation of a thick oxide layer on the surface-functionalized powders led to oxidation porosity in the as-printed samples. Therefore, the chemical etching should be improved to avoid the formation of a thick oxide layer on the powder surface and oxidation porosity in the as-printed L-PBF samples.

Knowing the spectral directional emissivity of 316L and AlSi10Mg PBF-LB/M surfaces: gamechanger for quantitative in situ monitoring

For a deep process understanding of the laser powder bed fusion process (PBF-LB/M), recording of the occurring surface temperatures is of utmost interest and would help to pave the way for reliable process monitoring and quality assurance. A notable number of approaches for in-process monitoring of the PBF-LB/M process focus on the monitoring of thermal process signatures. However, due to the elaborate calibration effort and the lack of knowledge about the occurring spectral directional emissivity ε′λ\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$${{\\varepsilon }^{\\prime}}_{\\lambda }$$\\end{document}, only a few approaches attempt to measure real temperatures. In this study, to gain initial insights into ε′λ\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$${{\\varepsilon }^{\\prime}}_{\\lambda }$$\\end{document} occurring in the PBF-LB/M process, measurements on PBF-LB/M specimens and metal powder specimens were performed for higher temperatures up to T = 1290 °C by means of the emissivity measurement apparatus (EMMA) of the Center for Applied Energy Research (CAE, Wuerzburg, Germany). Also, measurements at ambient temperatures were performed with a suitable measurement setup. Two different materials—stainless steel 316L and aluminum AlSi10Mg—were examined. The investigated wavelength λ ranges from the visible range (λVIS\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$${\\lambda }_{VIS}$$\\end{document} = 0.40–0.75 µm) up to the infrared, λ = 20 µm. The influence of the following factors were investigated: azimuth angle φ, specimen temperature TS, surface texture as for PBF-LB/M surfaces with different scan angles α, and powder surfaces with different layer thicknesses t\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$t$$\\end{document}.

ФИЗИКО-ХИМИЧЕСКИЕ СВОЙСТВА ПОЛИМЕРНО-БИТУМНЫХ ВЯЖУЩИХ, МОДИФИЦИРОВАННЫХ ШУНГИТОМ РАЗЛИЧНЫХ МЕСТОРОЖДЕНИЙ КАРЕЛИИ

The use of polymer-bitumen binders as part of an asphalt concrete mixture allows to improve the quality of road surfaces. The most commonly used polymer is styrene and butadiene copolymer, however, it does not provide sufficient durability of asphalt concrete and has a high cost. There is a positive experience in solving these problems through the use of polymer composites filled with fine powders. One of the promising polymer fillers is shungite. The purpose of this work was to study the effect of shungite from various deposits of Karelia on the structure and properties of polymer-bitumen binder. It was found that the introduction of shungite in the amount of 5 wt.% changes the physico-chemical characteristics of polymer-bitumen binders: the viscosity and softening temperature increase markedly, the temperature of brittleness, as well as extensibility and elasticity change to a lesser extent. Changes in these properties indicate the structuring of the binder by finely dispersed shungite. This phenomenon may be associated with the transfer of bitumen from a volumetric to a structured state due to its interaction with the surface of the shungite powder, as well as due to the diffusion of low-molecular components of the binder into the pores of the filler. Moreover, shungite samples from different deposits do not affect the studied characteristics in the same way. The explanation for this may lie in the different content of active adsorption centers on the surface of shungite, which is in a linear relationship with the main characteristics of the polymer-bitumen binder modified with shungite.

Synthesis and characterization of W-Y2O3 composites with core-shell structure via wet chemical method in an acidic solution

W-Y2O3 materials are the ideal PFMs in fusion reactors because of their excellent performance, however, due to the limitation of traditional powder preparation methods, W-Y2O3 materials face the challenges of coarse particles, high brittleness and low strength, and cannot meet the applications. The synthesis of high-quality powder is the first and crucial step in preparing high-performance tungsten based materials. Therefore, in this manuscript, W-Y2O3 powders with a nano and core-shell structure were synthesized by wet-chemical method in an acidic solution, and then the fine-grained W-Y2O3 composites was fabricated by spark plasma sintering (SPS) under 1873 K. The performance of W-Y2O3 composites and powders were analyzed by XRD, SEM and TEM. In particular, the existence form, distribution characteristics, evolution behavior of the second phase of Y2O3 and the interface characteristics of W/Y2O3 in powders and bulks were systematically discussed. H+ makes the self-assembly be inhibited in sol and produces the holes on surface of precursor powder during the reduction reaction. This structure of the precursor powder creates lots of paths which allow H2 to react with deep particles, resulting in ultrafine particle size, a core-shell structure and uniform element distribution. The powder of W-Y2O3 show obvious core-shell structure, and the thickness of the shell structure is uneven, about 7.7–15.2 nm, while the average grain size of these powders is 62.7 nm. Meanwhile, the W-Y2O3 alloys prepared from these powders show refinement and uniformity, the average grain size is 700 nm. Moreover, the new phase of Y2WO6 was observed at the W/Y2O3 interface, which has a semi-coherent relationship with Y2O3 and W, respectively. This is very conducive to improving the W/Y2O3 interface and thus significantly improving the performance. These results indicate that wet-chemical method in an acidic solution is a promising way to approach for synthesizing nano W-Y2O3 powders with core-shell structure and improve W/Y2O3 interface performance.

Exploring sustainable forensics: silica nanoparticle powder derived from rice husk waste for aged fingermark development and the chemistry of surface interactions

BackgroundPowder-based fingermark ridge visibility enhancement is a common technique employed in crime scenes due to ease of application and robustness of the application method. Pigmented powders created a contrast between the surfaces and developed ridgelines and are generally metals or metal oxides based. Previous research showed the successful development of fresh latent fingermarks using rice husk-derived silica nanoparticles on various surfaces. Nevertheless, there has been less previous evidence for the efficiency of the silica nanoparticle powder on aged fingermark development. Therefore, the aim here is to investigate the efficacy of the powder on aged fingermarks relative to commercial formulation to gauge the feasibility of having naturally derived powder as a possible alternative for field application and commercialisation.ResultsRigorous testing over a range of non- and semi-porous surfaces at varied ageing conditions revealed a minimal disparity in the performance of both powders on most surfaces. Still, silica nanoparticles exhibited superiority in terms of selectivity on silica-based surfaces. Close up analysis of developed fingermarks using electron microscope exposed clear demarcation between fingermark ridges and valleys using silica nanoparticles.ConclusionsFindings revealed that the interaction chemistry between powder particles and surface material either enhances or lowers the fingermark development capacity depending on the type of surface tested.

Microstructure and properties of oxide-reinforced FeCrAl matrix alloy manufactured by selective laser melting

In this work, nano-Y2O3 dispersed FeCrAl powders (NYD-Fe) were used to produce oxide dispersion strengthened (ODS) alloy by selective laser melting (SLM), and their microstructures and properties were investigated in detail by the kinds of characterization techniques. The results indicate that the Y2O3 particles adhered to the surface of FeCrAl powder absorb more laser, thus increasing the laser energy demand. High quality ODS deposits can be obtained at 600 mm/s and 180 W parameters. The ODS samples deposited by SLM exhibit coarse columnar grains with [001] texture. The Ti-rich nanoparticles and core-shell structured nanoparticles (Y- and O-rich core surrounded by a Ti-rich shell) are observed in ODS alloys. The precipitation formation of core-shell structured nanoparticles involves ball milling amorphization and dissolution reprecipitation. The ODS-180 alloy exhibits a higher ductility compared to FeCrAl-180 alloy, which is caused by the cellular structure with high density dislocations and the nano-sized precipitates inhibit the dislocation motion. The wear rate of the ODS-180 alloy is 51% lower than that of FeCrAl-180 alloy, which is mainly ascribed to the hardness and interface oxide layer resulting from its specific microstructural features.

Effect of element infiltration on radial composition/structure and magnetic/electrical properties of Fe-B amorphous powders prepared by spark erosion

Before confirming spark erosion as an effective technique for producing Fe-based amorphous powders, it is crucial to thoroughly investigate their magnetic/electrical properties and the impact of different elements infiltration on composition, microstructure, and performances. Limited research has been conducted on the magnetic and electrical properties of spark-eroded Fe-based amorphous powders, and there is a dearth of studies on the influence of different elements' infiltration. In this work, a series of binary Fe83B17 amorphous powders were synthesized using water (as a source of O), ethanol (as a source of C and O), and silicone oil (as a source of O, Si, and C). The elements O, C, and Si exhibit different concentration distributions along the radial direction in the synthesized powders. The depth of O infiltration varies between 10 and 35 nm, C from 190 to 280 nm, and Si barely diffuses inward. For powders prepared in water (WF), the formation of nanoclusters throughout the particle leads to an improved saturation magnetization. Besides, the infiltrated mass ratio of O is merely 1.38 wt% and is predominantly concentrated in the surface of WF powder, resulting in a significant increase in resistivity. The resistivity of WF powder is approximately four orders of magnitude higher compared to powders prepared in ethanol (EF) and silicone oil (SF). Nanoclusters are also observed in EF and SF powders, where the significant infiltration of non-magnetic C leading to a reduction in the saturation magnetization of both EF and SF powders. Inside EF powder, a remarkable peak of C content appears at ∼30 nm away from the powder surface in the radial direction, accompanied by an increase in structural order. This suggests a synchronous relationship between the variations of structural order in the radial direction and the concentration of the infiltration element. These findings demonstrate the practical feasibility of tuning composition and microstructure via dielectrics to develop high-performance Fe-based amorphous powders.

Influence of powder surface chemistry on the defect formation in AlSi10Mg alloy processed via laser powder bed fusion additive manufacturing

In laser powder bed fusion(LPBF) additive manufacturing(AM) of Al alloys, surface chemistry and dissolved gas composition(oxygen/oxides/hydroxides, hydrogen and moisture) of AM powders is a major influencing factor for porosity formation. Therefore, in the present investigation, this aspect is addressed using two sets of virgin AM AlSi10Mg powders, namely, Hi-Ox (2770 ppm oxygen) and Lo-Ox (660 ppm oxygen), to assess the printability under various processing parameters and defect formation in printed parts. Comprehensive and in-depth metallurgical analysis of both powders utilizing multiple characterisation techniques established the presence of various types of oxides/hydroxides with different complex chemistries on the powders’ surface. Enhanced spherical gas porosity and oxide inclusions were witnessed in Hi-Ox print coupons in contrast to the least defects in Lo-Ox coupons rationalized due to surface chemistry difference between the virgin powders. Consequently, the mechanical properties of the Hi-Ox print coupons, even with minimum defect density, are significantly inferior to Lo-Ox specimens. These observations suggest a competing influence of surface chemistry/dissolved gas composition and laser parameters for the processing of both powders. Overall, by correlating the microstructures with processing conditions and oxide concentration, defects morphology, the probable melt pool formation mechanism in LPBF of AlSi10Mg alloy (for high and low oxygen concentration) is elucidated.

Characteristic analysis of high-speed steel powder prepared by gas atomisation

The performance of high-speed steel (HSS) powder is a prerequisite for the preparation of high-performance powder metallurgy HSS. The physical properties, microstructure, and solidification characteristics of HSS powder prepared by nitrogen gas atomisation were systematically studied and analysed in detail. For the atomised TPM558 HSS powder, the morphology is spherical and the particle size distribution is wide. The smooth small particles of satellite powder attach to the surface of large particles. Shrinkage pits caused by solidification shrinkage exist on the surface of large particles. The average cooling rate is between 104 and 106 K·s−1, with the increase of cooling rate, the powder surface tends to be smooth, and the grain structure is transformed in the order of cellular to dendritic to radial. The single powder particle surface shows fine-equiaxed grains, while the internal presents columnar grains. The crystalline phases of the powder are austenite, ferrite, martensite, and carbide, and the carbide includes MC carbide with face-centred structure and M2C carbide with hexagonal structure. The average nano-hardness of the powder is 9.93 GPa, resulting in poor formability, and it can be pressed and formed only after adding binder.

Co-hydrolysis of TEOS and DDS to obtain a modified hydrophobic SiO2 insulation layer for FeSiBC amorphous magnetic powder core with low energy loss

The hysteresis effect and eddy currents caused by alternating magnetic fields greatly impede the improvement of the working efficiency and performance stability of soft magnetic powder cores. In this work, modified hydrophobic SiO2 nanoparticles were prepared by tetraethyl orthosilicate (TEOS) and dimethyl-diethoxy-silane (DDS) as co-precursors through sol–gel methods. The effect of different proportions of DDS and TEOS on the amorphous magnetic powder cores performance was studied. It was demonstrated that the insulation layer in DDS and TEOS co-precursors hydrolyzed composite powders exhibited more uniform distribution compared with TEOS hydrolyzed alone counterpart. The introduction of methyl groups reduced the accumulation of hydrolysis intermediates on the surface of FeSiBC powders. Furthermore, the addition of DDS reduced eddy current loss significantly with a low hysteresis loss. The total energy loss of the DDS and TEOS co-hydrolysis powder core were reduced by 16.1 % and 7.7 % at 1 MHz, 0.05 T compared to the uncoated powder core and the TEOS hydrolysis alone counterpart, respectively. The presented results provide insights into improving the application range and energy utilization efficiency for the magnetic powder cores.

Cold spray deposition of high density polyethylene composite powders

In this paper, we investigate the use of the cold spray additive manufacturing technique to deposit micron-sized composite particles of high-density polyethylene (HDPE) compounded with either micron or nanometer sized particles of silicon dioxide (SiO2) or copper (Cu). In this study, the mass fraction of the SiO2 and copper particles added into the final composite powders was varied between 0.5 % and 9.1 % and the deposition efficiency of each composite powder was measured. Deposition of the composite powders onto an HDPE substrate was successful even at the highest particle loadings tested. In each case, an optimal mass fraction of silicon dioxide or copper particles was observed with a maximum value of deposition efficiency larger than that of the pure HDPE. For the silicon dioxide composite powders, the deposition efficiency nearly doubled compared to the pure HDPE powders. The improvement of deposition efficiency at moderate particle loadings is likely due to the increase in the impact kinetic energy of the particles resulting from the increase in the density of the composite powders. While the decrease in deposition efficiency at high particle loadings is likely the result of the increased coverage of the silicon dioxide and copper particles on the surface of the HDPE powders limiting the interaction between the HDPE of the composite powder with the HDPE substrate. SEM images show that it is possible to create a smooth, dense, and uniform thin-film polymer composite coating using cold spray.

RESEARCH AND DEVELOPMENT OF HEAT TECHNOLOGY OF PREBIOTIC COMPLEX-FORMING POWDER PRODUCTION

The process of dehydration of the prebiotic squash-apple mixture is investigated, taking into account the properties of the material and drying modes. Prebiotic raw materials are maximally represented by dietary fibers, which include pectin substances, the content of which in raw materials is from 6 to 12%. Optimal modes of grinding and separation into different fractions of dry prebiotic materials for obtaining functional powders were determined. The complexing property of prebiotic mixtures is determined, which is 15-20% higher than pure pectin, due to an increase in the open surface of powders and the nativity of pectin substances.

Fabrication and characterization of graphene oxide (GO)-modified micro-nano composite magnetic microspheres

Addressing the contradiction between the magneto-rheological properties and dispersion stability of MRFs poses a significant challenge in the preparation process. This paper proposes a micro-nano composite material design scheme using graphene oxide as a grafting agent to encapsulate nanoscale magnetite (Fe3O4) particles onto the surface of carbonyl iron powders. The prepared micro-nano composite magnetic microspheres achieve a reduction in density for enhanced stability while ensuring no compromise in magnetic performance. The effectiveness of the preparation process is ensured through the analysis of the microscopic morphology, crystal structure, and elemental characteristics of all process products using Field Emission Scanning Electron Microscopy (FE-SEM), powder X-ray diffraction (XRD), Raman Spectroscopy, and Fourier Transform Infrared Spectroscopy (FTIR). To obtain MRFs more suitable for magneto-rheological damper applications, this study synthesized micro-nano composite MRFs with different base liquids and varying volume fractions. The stability and magneto-rheological properties of each sample were analyzed through visual techniques and rheological testing platforms. The results indicated that micro-nano composite MRFs based on 40% to 50% silicone oil exhibit superior stability in various aspects, including sedimentation stability, redispersion stability, and temperature stability. Additionally, the micro-nano composite MRFs demonstrated significantly enhanced magnetic performance compared to pure micrometer-sized, pure nanometer-sized, and micro-nano hybrid MRFs.

Low core loss and high DC bias performance of FeSiAl soft magnetic composites cores with hybrid insulating layers of MgO/SiO2

Soft magnetic composites (SMCs) play an indispensable role in electromagnetic conversion, transmission, and storage. However, in order to achieve miniaturization, energy conservation, and meet the application requirements of premagnetisation in direct-current (DC) components, SMCs are required to have low core loss and high DC bias performance. In this work, FeSiAl SMCs with hybrid insulating layers of MgO/SiO2 have been successfully prepared by the decomposition of magnesium acetate tetrahydrate and silicone resin. The presence of MgO and SiO2 insulating layers can effectively compensate for each other's coating defects, thereby forming complete insulating layers on the surface of FeSiAl powders to reduce the core loss. Finally, the FeSiAl@MgO/SiO2 SMC gets remarkable comprehensive magnetic properties with a low core loss (Pcv) of 163.7 mW/cm3 at 50 mT/100 kHz, a high DC bias performance of 53.7 % at 100 Oe, and an effective permeability (μe) of 46, which is promising for high-frequency and high-power applications.

Precision Interface Engineering of CuNi Alloys by Powder ALD Toward Better Thermoelectric Performance

AbstractThe main bottleneck in obtaining high‐performance thermoelectric (TE) materials is identified as how to decouple the strong interrelationship between electrical and thermal parameters. Herein, a precise interface modification approach based on the powder atomic layer deposition (ALD) technology is presented to enhance the performance of CuNi alloys. ZnO and Al2O3 layers as well as their combinations are deposited on the surface of powders, typically in 10–100 ALD cycles, and their effects on the TE performance of bulks is thoroughly investigated. The enhancement of the Seebeck coefficient, caused by the energy filtering effect, compensates for the electrical conductivity deterioration due to the low electrical conductivity of oxide layers. Furthermore, the oxide layers may significantly increase the phonon scattering. Therefore, to reduce the resistivity of coating layer, a multilayer structure is deposited on the surface of powders by inserting Al2O3 into ZnO. The accurate microstructure characterization shows that the Al atoms diffused into ZnO and realized the doping effect after pressing. Al diffusion has the potential to increase the electrical conductivity and complexity of coating layers. Compared to pure CuNi, zT increases by 128% due to the decrease in resistivity and stronger phonon scattering in phase boundaries.