Thick SiO2 Research Articles

Hydrophobic interfaces regulate iron carbide phases and catalytic performance of FeZnOx nanoparticles for Fischer-Tropsch to olefins

Fischer-Tropsch to olefins (FTO) with controllable iron carbide phase and high carbon utilization efficiency for Fe-based nanocatalyst attracts great interest but remains challenge. Herein, we report that the metastable Fe7C3 phase can be effectively tailored by altering shell thickness of hydrophobic SiO2 over a core-shell nanostructured FeZn@SiO2-c nanocatalyst. χ-Fe5C2 was the dominated iron carbide phase for FeZnOx and FeZn@SiO2 nanocatalysts, while numerous Fe7C3 phases existed for hydrophobic FeZn@SiO2-c nanospheres. Compared with FeZnOx, the CO2 selectivity of FeZn@ 4.1-SiO2-c decreased by > 70%, while 1.7-fold higher olefins selectivity was simultaneously obtained during syngas conversion process. The hydrophobic interface greatly suppressed the water-gas-shift reaction by promoting the quick diffusion of water, and the as-formed H2-lean and CO-rich local chemical environment benefits the formation of Fe7C3 and olefins products. This work provides a promising strategy to design phase-stable Fe7C3 with improvement of carbon efficiency for Fe-based nanocatalysts.

The improved thermoelectric properties of Mg2Sn/Mg multilayer films with nano-sized period by layer interface

The Mg2Sn/Mg multilayer films with different nano-sized modulation period were successfully prepared on single crystalline Si substrate with 500 ​nm thickness SiO2 layer by alternately sputtering using high pure metal Mg target and Mg–Sn alloy target. The chemical composition, surface and cross-sectional morphology, phase composition, carrier transport process and thermoelectric properties of deposited films were deeply investigated. The results show that the deposited films possess obvious layered structure, which is composed of metal Mg layer and antifluorite cubic Mg2Sn layer. The atom ratio [Mg]/[Sn]<2.0 in Mg2Sn layer between metal Mg layers and deposited films are p-typed semiconductor due to the existence of Mg vacancy in Mg2Sn lattice. The carrier concentration, mobility and thermal conductivity at room temperature decrease with reducing the modulation period of the multilayer films due to scattering of layer interface, at which depletion layer and built-in electric field form, impeding motion of the carriers. The electrical conductivity slightly decrease, but the Seebeck coefficient, power factor and figure of merit (ZT) greatly increase with reducing modulation period due to the scattering of the carriers. The ZT value of the film with the smallest modulation period of 171 ​nm reaches 0.51. The introduction of the layer interface greatly strengthens the carrier scattering process and improves the thermoelectric properties of the deposited films. This work demonstrates that introduction of heterogeneous interfaces composed of the same elements into films can effectively improve its thermoelectric properties.

Link between anisotropic electrochemistry and surface transformations at single‐crystal silicon electrodes: Implications for lithium‐ion batteries

AbstractSilicon is a promising negative electrode material for high‐energy‐density Li‐ion batteries (LiBs) but suffers from significant degradation due to the mechanical stress induced by lithiation. Volume expansion and lithiation in Si are strongly anisotropic but associated early interfacial transformations linked to these phenomena and their implications for electrode performance remain poorly understood. Here we develop a novel correlative electrochemical multi‐microscopy approach to study local interfacial degradation at the early stages for three different surface orientations of Si single crystals: Si(1 0 0), Si(1 1 0) and Si(3 1 1), after Li‐ion electrochemical cycling. The experimental strategy combines scanning electrochemical cell microscopy (SECCM) measurements with subsequently recorded scanning transmission electron microscopy images of high‐quality cross sections of Si electrodes, extracted at selected SECCM regions, using a novel Xe+ plasma‐focused ion beam procedure. These studies reveal significant surface orientation–dependent nanoscale degradation mechanisms that strongly control electrode performance. Si(1 0 0) was immune to interfacial degradation showing the best lithiation reversibility, whereas local nanoscale delamination was observed in Si(1 1 0) leading to a lower Coulombic efficiency. Continuous electrochemical deactivation of Si(3 1 1) was associated with delamination across the whole interface, Li trapping and formation of thick (ca. 60 nm) SiO2 structures. These results demonstrate surface crystallography to be a critical factor when designing Si‐based battery materials and strongly suggest that promoting Si(1 0 0) facets could potentially provide longer cycling life and performance due to a higher resistance to degradation.

Comparative investigation of insulation techniques based on APTES for different structures and magnetic properties of soft magnetic composites

FeNi powders were insulated with APTES by solution method and solidification method, respectively. Different coating mechanisms have been systematically studied according to analysis on microstructure, surface charge state, thermal stability of magnetic powders and magnetic properties of corresponding soft magnetic composites (SMCs). It was found that a slight amount of polysiloxane and amorphous silica would be deposited on FeNi powders in solution method, resulting in an ultra-thin insulation layer. In contrast, continuously increasing concentration of polysiloxane in reaction zone gives rise to a thick and smooth SiO2 layer in solidification method. Owing to unique growth mechanisms of solidification method, it is easy to control the thickness of SiO2 layer by adjusting the concentration of APTES, which is in favor of improving insulation quality. Accordingly, FeNi SMCs prepared in solidification method own much higher resistivity, lower μ″ and lower tanδ (particularly at high frequency), compared with samples obtained by solution method with the same volume of APTES. Besides, increasing volume of APTES in solidification method leads to the decrease of both μ′ and μ″. This work may not only provide novel insights into APTES-based insulation process, but also offer powerful technique for fabricating high-frequency SMCs.

Performance improvement of a tunnel junction memristor with amorphous insulator film

This study theoretically demonstrated the oxygen vacancy (VO2+)-based modulation of a tunneling junction memristor (TJM) with a high and tunable tunneling electroresistance (TER) ratio. The tunneling barrier height and width are modulated by the VO2+-related dipoles, and the ON and OFF-state of the device are achieved by the accumulation of VO2+ and negative charges near the semiconductor electrode, respectively. Furthemore, the TER ratio of TJMs can be tuned by varying the density of the ion dipoles (Ndipole), thicknesses of ferroelectric-like film (TFE) and SiO2 (Tox), doping concentration (Nd) of the semiconductor electrode, and the workfunction of the top electrode (TE). An optimized TER ratio can be achieved with high oxygen vacancy density, relatively thick TFE, thin Tox, small Nd, and moderate TE workfunction.

Parametric Optimization and Numerical Analysis of GaAs Inspired Highly Efficient I-Shaped Metamaterial Solar Absorber Design for Visible and Infrared Regions

Renewable energy demand is increasing as fossil fuels are limited and pollute the environment. The solar absorber is an efficient renewable energy source that converts solar radiation into heat energy. We have proposed a gallium arsenide-backed solar absorber design made with a metamaterial resonator and SiO2 substrate. The metamaterial resonator is investigated with thin wire metamaterial and I-shaped metamaterial designs. The I-shape metamaterial design outperforms the thin wire metamaterial design and gives 96% average absorption with a peak absorption of 99.95%. Structure optimization is applied in this research paper using parametric optimization. Nonlinear parametric optimization is used because of the nonlinear system results. The optimization method is used to optimize the design and improve the efficiency of the solar absorber. The gallium arsenide and silicon dioxide thicknesses are modified to see how they affect the absorption response of the solar absorber design. The optimized parameter values for SiO2 and GaAs thicknesses are 2500 nm and 1000 nm, respectively. The effect of the change in angles is also investigated in this research. The absorption is high for such a wide angle of incidence. The angle of 30° only shows a lower absorption of about 30–50%. The effect of the change in angles is also investigated in this research. The design results are verified by presenting the E-field results for different wavelengths. The optimized solar absorber design applies to renewable energy applications.

A 1 × 2 Two-Dimensional Slanted Grating Based on Double-Layer Cylindrical Structure

Diffraction gratings play an increasingly important role in various planar optical systems, such as near-eye display systems for virtual reality (VR) and augmented reality (AR). The slanted gratings have more advantages than other elements. A 1 × 2 transmission two-dimensional (2D) slanted grating based on a double-layer cylindrical structure was proposed in this paper. In the initial phase of this study, this kind of grating was proposed and designed. We used rigorous coupled-wave analysis (RCWA) and simulated annealing algorithm (SA) to optimize the grating parameters. The effects of the grating geometric parameters on the diffraction efficiency were investigated using rigorous coupled-wave analysis (RCWA). The simulated annealing algorithm (SA) optimization results show that the diffraction efficiency of the (0, −1) and (−1, 0) order exceed 35% under normal incidence in the range of 429–468 nm wavelength for TE and TM polarization. Meanwhile, the total diffraction efficiency can reach up to 78%. In the last section, we discuss the tolerances for the grating parameters to ensure high quality manufacturing processes. The total effective efficiency is greater than 75% when the MgF2 thickness is from 300 nm to 350 nm and the SiO2 thickness is from 525 nm to 550 nm. Moreover, the grating period has a 53 nm fabrication tolerance, and the slanted angle has a 8.8-degree fabrication tolerance. The relatively large tolerances ensure that it is easy to fabricate the two-dimensional slanted grating and to achieve the targeted objectives. The proposed 2D slanted grating can be applied to 2D exit pupil expansion, which is of great importance in AR/VR applications.

Thermodynamic Multi-Field Coupling Optimization of Microsystem Based on Artificial Intelligence

An efficient multi-objective optimization method of temperature and stress for a microsystem based on particle swarm optimization (PSO) was established, which is used to map the relationship between through-silicon via (TSV) structural design parameters and performance objectives in the microsystem, and complete optimization temperature, stress and thermal expansion deformation efficiently. The relationship between the design and performance parameters is obtained by a finite element method (FEM) simulation model. The neural network is built and trained in order to understand the mapping relationship. Then, the design parameters are iteratively optimized using the PSO algorithm, and the FEM results are used to verify the efficiency and reliability of the optimization methods. When the optimization target of peak temperature, bump temperature, TSV temperature, maximum stress and maximum thermal deformation are set as 100 °C, 55 °C, 35 °C, 180 Mpa and 12 μm, the optimization results are as follows: the peak temperature is 97.90 °C, the bump temperature is 56.01 °C, the TSV temperature is 31.52 °C, the maximum stress is 247.4 Mpa and the maximum expansion deformation is 11.14 μm. The corresponding TSV structure design parameters are as follows: the radius of TSV is 10.28 μm, the pitch is 65 μm and the thickness of SiO2 is 0.83 μm. The error between the optimization result and the target temperature is 2.1%, 1.8%, 9.9%, 37.4% and 7.2% respectively. The PSO method has been verified by regression analysis, and the difference between the temperature and deformation optimization results of the FEM method is not more than 3%. The stress error has been analyzed, and the reliability of the developed method has been verified. While ensuring the accuracy of the results, the proposed optimization method reduces the time consumption of a single simulation from 2 h to 70 s, saves a lot of time and human resources, greatly improves the efficiency of the optimization design of microsystems, and has great significance for the development of microsystems.

Deposition of Thick SiO2 Coatings to Carbonyl Iron Microparticles for Thermal Stability and Microwave Performance.

Thick dielectric SiO2 shells on the surface of iron particles enhance the thermal and electrodynamic parameters of the iron. A technique to deposit thick, 500-nm, SiO2 shell to the surface of carbonyl iron (CI) particles was developed. The method consists of repeated deposition of SiO2 particles with air drying between iterations. This method allows to obtain thick dielectric shells up to 475 nm on individual CI particles. The paper shows that a thick SiO2 protective layer reduces the permittivity of the 'Fe-SiO2-paraffin' composite in accordance with the Maxwell Garnett medium theory. The protective shell increases the thermal stability of iron, when heated in air, by shifting the transition temperature to the higher oxide. The particle size, the thickness of the SiO2 shells, and the elemental analysis of the samples were studied using a scanning electron microscope. A coaxial waveguide and the Nicholson-Ross technique were used to measure microwave permeability and permittivity of the samples. A vibrating-sample magnetometer (VSM) was used to measure the magnetostatic data. A synchronous thermal analysis was applied to measure the thermal stability of the coated iron particles. The developed samples can be applied for electromagnetic compatibility problems, as well as the active material for various types of sensors.

Fabrication and soft magnetic properties of FeSiB based flakes with insulating surface layer suitable for high frequency power applications

FeSiB based soft magnetic flakes (SMFs; ϕ: 63-106 µm, t: 2-5 µm) coated with optimally thick (∼10 nm) SiO2 were fabricated as the potential magnetic material for pressed cores suitable for use in power inductors operating beyond 10 MHz. Such thin SMFs were produced by mechanical ball milling of commercially available thick (∼27 µm) ribbons followed by an optimized sol-gel coating in presence of a silane coupling agent. Milling helped to reduce ribbon thickness below the skin depth to minimize eddy current loss at high frequencies. The effect of milling (medium, duration, rotation speed, and ball-to-powder ratio) and coating conditions on the soft magnetic properties of the SMFs were investigated. An optimally tiny fraction of the milled flakes was allowed to become nanocrystalline, which augments saturation flux density (BS) and permeability (µ) without incurring additional losses. The results from X-Ray photoelectron spectroscopy and magnetization measurement confirm that a stress-releasing post-annealing process reduced coercivity from ∼62 Oe to ∼6 Oe and enhanced the magnetic saturation moment from 126 emu/g to 142 emu/g without affecting the thin yet robust insulating SiO2 layer.

Annealing process of Co-Fe-B based multilayers showing skyrmion Brownian motion

Skyrmions are topological spin textures that exhibit Brownian motion in solids. They have attracted increasing research interest in terms of realizing a device that utilizing stochastic behavior and investigating new physical phenomena. However, skyrmions that exhibit Brownian motion are sensitive to changes in magnetic properties and are easily affected by aging variation. For instance, although skyrmions appear in a sample immediately after fabrication, they sometimes disappear after few weeks. This characteristic prevents the reproducibility experiment and affects device stability. In this study, we demonstrated that aging variation can be suppressed by annealing in air for only 3 min, which is an easy and rapid method. We investigated the change in the magnetic properties by annealing and air exposure and found that the main mechanism of aging variation is oxidation of the sample surface. The magnetic properties of samples with Pt and thick SiO2 capping were analyzed, and we demonstrated that aging variation can be suppressed by avoiding surface oxidation. Our work accelerates the research of fundamental physics regarding skyrmion Brownian motion and of device applications utilizing stochastic system.

Large-Scale Fabrication of High-Performing Single-Crystal SiC Nanowire Sponges Using Natural Loofah

This study presents large-scale fabrication of single-crystal SiC nanowire (SiCnw) sponges through a carbothermal reduction approach using agricultural residue loofah, which is believed to be a perfect alternative to traditional petrochemical materials as the carbon source in industrial fabrication of SiC nanowires, without additional chemical C sources or catalysts. The single-crystal ultralong SiCnw are observed to have diverse morphologies with diameters of 50–400 nm, which possess a significant anisotropic and hierarchical microstructure with planar-aligned bamboo joints. A roughly 2 nm thick amorphous SiO2 layer is identified wrapping the crystalline 3C-SiC. The underlying vapor–solid mechanism is systematically investigated via thermodynamic calculations on the formation and interactions of SiO, CO, and SiC. Noteworthily, the fabricated loofah-based SiCnw sponge exhibits prominent high-temperature performance after thermal insulation tests of alcohol lamp flame and butane blowtorch flame, which is attributed to the stacking faults, SiO2 layer, SiC/SiO2 interface of the nanowires, and the overlength pathway in the porous aerogel–sponge domain synergetically acting as a phonon barrier to enhance phonon scattering, prolong phonon diffusion, and eventually reduce solid thermal conductivity in the sponge architecture. Our current work has great potential to be applied in the eco-friendly industrial preparation of high-performing SiCnw as thermal protection materials in harsh environments.

Nanoindentation deformation and fracture mechanisms of SiC/SiO2 thermally oxidized in plasma wind tunnel

Mechanical strain and delamination of surface oxide from substrate are important mechanisms leading to failure of thermal protection systems in hypersonic vehicles. In this work, the deformation and fracture mechanisms of a thermally oxidized SiC/SiO2, formed by dynamic oxidations inside a plasma wind tunnel, are studied by nanoindentation experiments and finite element modeling. The results show an amorphous and uniform SiO2 formation on β-SiC at 1200∼1400 °C in the plasma flow (pressure ≈6.5 kPa), after long-term single/repeated oxidations. In the plasma environment the passive oxidation of SiC is slow, as a result the as-formed SiO2 is very thin. The SiO2 thickness is only ≈680 nm after 8 × 500 s dynamic oxidation. SiC/SiO2 exhibits a strong depth dependent indentation behavior, and at a critical indentation depth, delamination of SiO2 oxide scale is triggered. Finite element modeling helps decouple the effects of SiC substrate, residual thermal stress and interfacial delamination on the nanoindentation response of SiC/SiO2. The results evidence that delamination has a negligible effect on the nanoindentation response, and the main contributions are the SiC substrate and residual thermal stress. This work may forward the fundamental understanding of deformation and fracture mechanisms of oxide scales on thermal protection materials in response to localized loading conditions.

Comb-Like Hybrid Plasmonic Ring Resonator for Large and Voltage Tunable Group Delay

A nanophotonic ring resonator based on hybrid plasmonic waveguide is numerically proposed. Introduction of a comb-like structure in the resonator results in large group delay which can be tuned electrically. The proposed silicon-based nanophotonic structure incorporates comb-like design with copper-air subwavelength grating on SiO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> which supports resonance enhanced propagation of hybrid plasmonic mode confined in 50 nm thick SiO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> . The device with its engineered design shows an ultra-large group delay of 208 ps for 1 mm length. The proposed device also exhibits a voltage tunable group delay with a tuning of 48 ps on varying the voltage from −5 V to 5 V. The proposed device with its CMOS compatible and scalable design is useful for integrated optoelectronic circuits. The reported large delay and wide tuning make it a perfect candidate for applications in optical delay lines, signal processing, beam steering in phase array antennas and in microwave photonics.

High-Sensitivity and Wide-Range Antenna Sensor Based on EBG and SiO2 for Soil Water Content Monitoring

There are many problems with agricultural technology around the world, such as extensive irrigation which causes the waste of water. To significantly improve the efficiency of irrigation water, an antenna sensor, with high sensitivity and wide range, is proposed to measure the soil water content wirelessly. When the soil water content changes, the resonant frequency of the antenna will shift. By reading the resonant frequency of the antenna sensor, the soil water content can be measured and transmitted wirelessly. The antenna sensor has a wider detection range of soil water content, ranging from 10% to 44%, and a novel metamaterial structure (electromagnetic bandgap, EBG) is designed and its function in improving sensitivity is verified. Furthermore, by sputtering 60 nm thick SiO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> film on the surface of the antenna patch, its sensitivity has also been greatly improved. When the SiO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> film is sputtered on the antenna sensor, its sensitivity is 7.2 MHz/% and 7.6 MHz/% when the soil water content is 10%~29% and 30%~44%, respectively. In summary, this work contributes to methods and instruments for wireless measurement of the soil water content.

Thermo-optic phase shifter based on amorphous silicon carbide

We report the preliminary experimental results for an amorphous silicon carbide (a-SiC) thermo-optic phase shifter (TOPS). This device is based on microring resonator (MRR) structure with a titanium (Ti) heater placed on the top of the device, separated by 1.5 μm thick SiO2 to reduce the optical loss. The proposed a-SiC microring has a thickness and a radius of 1.1 μm and 33 μm, respectively. By applying an electrical power in the Ti heater, a resonance wavelength shift at an optical wavelength of λ=1550 nm is shown, and the extracted thermal tunability is 52.2 pm/mW.

Enhancement of Light Absorption in the Active Layer of Organic Solar Cells using Ag:SiO2 Core-Shell Nanoparticles

Organic solar cells still suffer from relatively low conversion efficiency despite significant progress. An Ag:SiO2 core-shell nanoparticle embedded inside the active layer of an organic solar cell is expected to enhance light absorption. Light absorption within the active layer consisting of 70 nm thickness PEDOT: PSS and P3HT: PCBM was calculated using the finite element method for a variable diameter of the silver core, the thickness of the SiO2 shell, and the relative position of nanoparticle inside the active layer. The diameter of the Ag nanoparticle varies from 20 to 50 nm, the thickness of SiO2 varies from 1 to 4 nm, and the position was shifted vertically to 70 nm. The maximum light absorption in the active layer is obtained for silver nanoparticles with a diameter of 40 nm and a SiO2 thickness of 1 nm. The optimum position of the core-shell nanoparticle was found to be not at the interface between the PEDOT: PSS and P3HT: PCBM layers but a little bit shifted down into P3HT: PCBM layer. The highest increase of light absorption, compared to without Ag:SiO2, is 210%, much higher than reported in the literature. Increasing absorption is related to the excitation of surface plasmon resonance of Ag:SiO2 nanoparticles leading to the local field and scattering enhancement in the active layer of the organic solar cell

Silicon Cutting Waste Derived Silicon Nanosheets with Adjustable Native SiO2 Shell for Highly‐Stable Lithiation/Delithiation

Silicon is an excellent candidate for the next generation of ultra-high performance anode materials, with the rapid iteration of the lithium-ion battery industry. High-quality silicon sources are the cornerstone of the development of silicon anodes, and silicon cutting waste (SCW) is one of them while still faces the problems of poor performance and unclear structure-activity relationship. Herein, a simple, efficient, and inexpensive purification method is implemented to reduce impurities in SCW and expose the morphology of nanosheets therein. Furthermore, HF is used to modulate the abundant native O in SCW after thermodynamic and kinetic considerations, realizing the mechanical support for the internal Si in the form of an amorphous SiO2 shell. Afterward, SCNS@SiO2 -2.5 with a 1.0nm thick SiO2 shell exhibits a reversible capacity of 1583.3 mAhg-1 after 200 cycles at 0.8 Ag-1 . Ultimately, the molecular dynamics simulations profoundly reveal that the amorphous SiO2 shell is transformed into the extremely ductile Lix SiOy shell to ditch stress and relieve strain during the lithiation/delithiation process.

Preparation and thermogenic performance of monodisperse ferromagnetic Fe/SiO2 nanoparticles for magnetic hyperthermia and thermal ablation*

Ferromagnetic nanoparticles have great potential to be used in the field of magnetic hyperthermia and thermal ablation due to its high saturation magnetization (Ms) and high heating efficiency. In this paper, monodisperse spherical α-Fe2O3 nanoparticles were prepared by hydrothermal method using FeCl3, NaHCO3 and Na2SO4 as reactants. Then monodisperse Fe/SiO2 nanoparticles with core/shell structure were obtained by coating SiO2 on the surface of α-Fe2O3 nanoparticles and reducing at 500℃ in hydrogen atmosphere. The diameter of Fe core is about 230 nm and the thickness of SiO2 coating is about 75 nm. Magnetic measurements show that Fe/SiO2 nanoparticles exhibit typical ferromagnetic properties with Ms about 132.5 emu/g at 25 ℃. As-obtained Fe/SiO2 nanoparticles have higher heating efficiency than superparamagnetic ferrite nanoparticles. The high heating ability of the Fe/SiO2 nanoparticles is estimated to be related to the hysteresis loss and Brownian relaxation mechanism during alternating magnetization. The results show that Fe/SiO2 nanoparticles are promising for the applications of magnetic hyperthermia and thermal ablation.

Structural, magnetic and microwave absorption properties of novel hollow core–shell (SrMnCoFe10 O19/MnCoFe2O4)/SiO2 composite microfibers synthesized via electrospinning

Ferrites were among the earliest types of microwave absorbers due to their high magnetic dissipation and low cost. Ferrites, on the other hand, have some disadvantages, such as a low natural resonance frequency (fr), a lack of dielectric loss, and a high density. We effectively generated (SrMnCoFe10O19/MnCoFe2O4)/SiO2 samples with hollow microfiber morphologies and most of the effective parameters suggested to overcome these disadvantages and increase the microwave dissipation properties of ferrites. Hard and soft SrMnCoFe10O19/MnCoFe2O4 hollow microfibers were obtained using sol-gel and electrospinning technology. After heat treatment at 1050 °C for 3 h, the binary ferrites are formed. (Hard ferrite/soft ferrite)/SiO2 core-shell structures were fabricated by the Stober process, so their microwave absorption performance is greatly influenced by the hard/soft mass ratio and SiO2 thickness of the sample. The fabricated fibers were characterized by x-ray diffraction (XRD), vibrating sample magnetometer (VSM), field emission scanning electron microscopy (FESEM), FTIR spectroscopy, and vector network analyzer (VNA). The single-phase structure of all microfibers was determined by X-ray diffraction (XRD) analysis. The phase formation of the coated microfibers is also elaborated using Fourier transform infrared spectroscopy (FTIR) based on identified chemical bonds. According to the (FESEM) analysis results, the microfibers manufactured have a homogeneous core–shell structure. A vector network analyzer was used to investigate the samples' dielectric constants and microwave absorption properties between 12 and 18 GHz at room temperature. The results showed that when the mass ratio is hard/soft (8: 2) and the mass ratio of ferrite/SiO2 (1:1), the maximum reflectance loss is −27 dB and the absorption bandwidth is 2 GHz. The magnetic saturation (Ms) was calculated at 43.44 emu/g and the calculated coercivity values (1163.07 Oe) confirm the hard ferrite/soft ferrite/SiO2 core-shell structures.