Porous Sheet Research Articles

A Soft Biodegradable Chitosan‐Based Medical Microrobot with Optimized Structural Design and X‐Ray Visibility for Targeted Vessel Chemoembolization

AbstractAlthough many medical microrobots have been developed for treating diseases, their designs have not been optimized for disease environments and their functionality and capabilities have been primarily demonstrated in vitro. In addition, the imaging of microrobots within blood vessels in deep tissues remains a challenge. Herein, a chitosan‐based biodegradable microrobot with optimized structural design and X‐ray imaging for targeted vessel chemoembolization is reported. The design of the microrobot takes into account its magnetizability and stackability in blood vessels. The microrobot is prepared through laser micromachining of a porous chitosan sheet, attachment of nanoparticles, and filling the pores with gelatin. The optimized microrobot is biocompatible, biodegradable, thrombogenic, magnetically targetable, and drug‐loadable, as demonstrated both in vitro and in a blood vessel phantom. X‐ray imaging of the gold nanoparticle‐attached microrobots compares well with using commercial iodinated contrast materials, thereby demonstrating their real‐time long‐term X‐ray imaging capability. The in vivo real‐time imaging and targeted vessel embolization of the microrobot are demonstrated in rat liver. The proposed microrobot overcomes the limitations of embolic microbeads currently used in targeted vessel chemoembolization (i.e., targeted vessel blocking and X‐ray visibility) and expands the capability of microrobots in advanced platforms for treating human diseases.

Investigating the Influence of Chemical Reaction on MHD-Casson Nanofluid Flow via a Porous Stretching Sheet with Suction/Injection

This study aims to investigate the influence of chemical reaction on the flow characteristics of a magnetohydrodynamic (MHD) Casson nanofluid over a porous stretching sheet with suction/injection. The nanofluid (NF) is comprised of a base fluid with suspended nanoparticles (NPs), and the Casson fluid (CF) model is employed to capture the non-Newtonian behavior. The governing partial differential equations (PDEs) for momentum, energy, and NP concentration are derived, incorporating the effects of magnetic field, viscous dissipation, chemical reaction, and porous medium. The resulting system of nonlinear ordinary differential equations (ODEs) is solved numerically using the Runge-Kutta-Fehlberg method together with the shooting process. The effects of various physical parameters, such as magnetic field strength, porous medium, CF parameters, NP volume fraction, suction/injection parameter, and chemical reaction parameter, on the flow characteristics are examined in detail. The results reveal that faster movement is linked to higher Grashof numbers and porous mediums, but weaker magnetic fields slow it down. The suction/injection affect velocity inversely. The Prandtl and Eckert numbers have opposite effects on temperature fields. The thermophoresis and Brownian motion parameters affect the opposite trends of the concentration and temperature distributions. The concentration reduces with chemical reaction parameters and the Lewis number. Heat transfer (HT) is enhanced for higher Brownian and thermophoresis. The findings of this study can have potential applications in various engineering fields, such as microfluidics, chemical processing, and thermal management systems, where precise control of fluid flow and heat transfer is essential.

Non-Newtonian Flow with Heat and Mass Transfer Over a Porous Stretching Sheet Under the Effects of Space Dependent and TGD Heat Sink, Non-Uniform Heat Source and Dissipation of Energy and CGD Mass Diffusion with Suction/Blowing

In the present paper, an analytical study of visco - elastic fluid flow with heat and mass transfer characteristics over a porous stretching sheet has been examined. Heat balance is maintained with space dependent and temperature gradient dependent heat sink/source, viscous dissipation, and non-uniform heat source on the non-Newtonian Walter’s liquid B' model. The mass balance is maintained with chemically reactive species of order I, variable mass diffusivity and concentration gradient dependent mass diffusion. Using similarity transformation technique on the highly non-linear differential equations, several closed form analytical solutions are obtained for non-dimensional temperature and concentration in both PST and PHF cases in the form of confluent hypergeometric (Kummar’s) functions. The effect of permeability parameter, viscoelastic parameter, suction parameter on velocity profiles and various physical fluid situations with different degrees of viscoelasticity, Prandtl number, Eckert number, heat source- sink strength, temperature field are discussed in detail and presented through graphs. Similarly in the mass transfer field the effects of Schmidt number, reaction rate parameters are discussed in detail and presented through graphs.

Re-examination of nonlinear vibration, nonlinear bending and thermal postbuckling of porous sandwich beams reinforced by graphene platelets

This paper re-examines the nonlinear free vibration, nonlinear bending and thermal postbuckling behaviors of porous sandwich beams with graphene platelets (GPL) reinforcements rested on elastic foundations. We remove the equivalent isotropic model (EIM) and introduce an inhomogeneous model. The shear modulus together with the Young’s moduli for porous GPLRC core is determined by a generic Halpin–Tsai model with porosity. Mechanical properties of both porous GPLRC core and metal face sheets are temperature dependent. Based on the framework of higher order shear deformation beam theory, the motion equations of porous sandwich beams with GPL reinforcements are established. In the modeling, the von Kármán kinematic nonlinearity, beam-foundation interaction and thermal effect are considered. By employing the two-step perturbation method, the analytical solutions are obtained for the nonlinear vibration and nonlinear bending as well as thermal postbuckling problems. Numerical investigations are performed for comparing the results obtained from the EIM and the present model. The outcomes reveal that the EIM is invalid for linear free vibration, thermal buckling and postbuckling analyses of porous sandwich beams with GPL reinforcements, but the EIM is valid in some cases for nonlinear bending and nonlinear vibration analyses of the same beam.

Micropolar Fluid Flow Through a Porous Stretching/Shrinking Sheet with Mass Transpiration: An Analytical Approach

In this paper, the flow of a micropolar fluid over a stretching or shrinking sheet is investigated under magnetohydrodynamic (MHD) conditions. Such a flow is described by highly nonlinear PDEs. Using the similarity transformation technique, the PDEs governing the flow are reduced to a system of nonlinear ODEs, which further allows a closed-form analytical solution. The effect of the microrotation on the skin friction coefficient, the dimensionless forms of the velocity, and the temperature flow fields in the neighborhood of the stretching or shrinking sheet are discussed for various combinations of the dimensionless parameters. The numerical results reveal that the micropolar flow may accelerate or deaccelerate depending upon the numerical values of the mass transpiration and the permeability of the porous sheet. An increase in the tangential and the angular flow velocities is found to occur with an increase in the microrotation. Further, it is observed that the increase in the microrotation increases the skin friction coefficient.

Effect of Chemical Reaction on Unsteady Mhd Convective Transport Passing a Vertical Porous Sheet

An analysis of the effect of chemical reactions on unsteady MHD convective transport passing a vertical porous sheet has been introduced in this research paper. The model formed of highly nonlinear governing equations are converted by inserting the similarity transformations. The numerical solutions of the fluid properties like concentration, temperature, and velocity are presented graphically. This paper also presented the heat transfer rate, mass transfer rate, and the local skin friction coefficient which are analyzed in tabular forms. The dimensionless parameters or numbers used in this problem are suction parameter, magnetic parameter, Prandtl number, Schmidt number, and chemical reaction parameter. Results give the improvement of concentration and motion of the fluid for growing values of the chemical reaction, but the reverse trends are found for the Schmidt number. The local skin-friction coefficient and the mass transfer rate are increased by about 23 % and 283%, respectively for growing amounts of the chemical reaction from 0.5 to 2.0. Journal of Engineering Science 14(1), 2023, 85-93

Cork-Derived Carbon Sheets for High-Performance Na-Ion Capacitors.

S-doped carbon sheets have been easily prepared by deconstructing the 3D cellular structure of a fully sustainable and renewable biomass material such as cork through a mild ball-milling process. S-doping of the material (>14 wt % S) has been achieved by using sulfur as an earth-abundant, cost-effective, and environmentally benign S-dopant. Such synthesized materials provide large Na storage capacities in the range of 300-550 mAh g-1 at 0.1 A g-1 and can handle large current densities of 10 A g-1, providing 55-140 mAh g-1. Their increased packing density compared to the 3D pristine structure allows them to also provide good volumetric capacities in the range of 285-522 mAh cm-3 at 0.1 A g-1 and 53-133 mAh cm-3 at 10 A g-1. In addition, highly porous carbon sheets (SBET > 2700 m2 g-1) have been produced from the same carbon precursor by rationally designing the chemical activation approach. These materials are able to provide good anion storage capacities/capacitances of up to 100-114 mAh g-1/163-196 F g-1. A sodium-ion capacitor assembled with the optimized S-doped carbon sheets and the highly porous carbon sheets with mass matching ratios provided the best energy/power characteristics (90 Wh kg-1 at 29 kW kg-1) in combination with robust cycling stability over 10,000 cycles, with a capacity fade of only 0.0018% per cycle.

Impact of common face mask regeneration processes on the structure, morphology and aerosol filtration efficiency of porous flat sheet polysulfone membranes fabricated via nonsolvent-induced phase separation (NIPS)

The potential of flat sheet polymeric membranes as a sustainable solution for reusable facemask filters was investigated by analyzing the effect of common face mask regeneration processes on polysulfone (PSf) membranes’ structure, morphology, and aerosol filtration efficiency. The impact of regeneration processes, such as isopropanol (IPA), detergent and bleach washes, and ultraviolet light exposure, was for the first time compared between surgical masks, N95 masks and flat sheet PSf membranes. The PSf membranes were fabricated via non-solvent induced phase separation (NIPS), and demonstrated a higher particulate filtration efficiency (99.06 ± 1.38%) for PM0.3 i.e., particulate matter of 0.3 µm aerodynamic diameter compared to surgical mask (70.93 ± 2.82%) and N95 (N95-1: 97.09 ± 7.37%; N95-2: 91.46 ± 1.45%). Scanning electron microscopy (SEM) analysis revealed no significant changes in morphology of treated membrane pores. Fourier transform infrared spectroscopy (FTIR), contact angle goniometry, and Xray photoelectron spectroscopy (XPS) analyses revealed retained membrane surface composition, hydrophobicity, and showed no residual elements from sterilizing chemicals after rinsing for 30 min. Statistically insignificant differences in treated and untreated PSf membrane pore size, porosity, and mechanical strength obtained in this work suggest the absence of chain scission due to radical formation, which can arise from polymer chains exposure to UV and bleach (NaClO), and change in polymer chain conformation. Treatment with IPA and detergent, which resulted in 46.7 ± 5.5% and 64.3 ± 12.9 % reduction of 0.3 µm aerosol filtration efficiency, respectively, for commercially available face masks, showed an insignificant decrease in PSf membrane filtration performance, which was attributed to dissipation of electrostatic charges responsible for the high filtration efficiency of non-woven face masks.

Controllable Crystal Growth and Improved Photocatalytic Activity of Porous Bi2O3-Bi2S3 Composite Sheets.

Porous Bi2O3-Bi2S3 composite sheets were constructed through a combinational methodology of chemical bath deposition and hydrothermal reaction. The Na2S precursor concentration in the hydrothermal solution was varied to understand the correlation between the vulcanization degree and structure evolution of the porous Bi2O3-Bi2S3 composite sheets. The control of the etching rate of the Bi2O3 sheet template and the regrowth rate of Bi2S3 crystallites via suitable sulfide precursor concentration during the hydrothermal reaction utilizes the formation of porous Bi2O3-Bi2S3 sheets. Due to the presence of Bi2S3 crystallites and porous structure in the Bi2O3-Bi2S3 composites, the improved visible-light absorption ability and separation efficiency of photogenerated charge carriers are achieved. Furthermore, the as-synthesized Bi2O3-Bi2S3 composite sheets obtained from vulcanization with a 0.01M Na2S precursor display highly enhanced photocatalytic degradation toward methyl orange (MO) dyes compared with the pristine Bi2O3 and Bi2S3. The porous Bi2O3-Bi2S3 sheet system shows high surface active sites, fast transfer, high-efficiency separation of photoinduced charge carriers, and enhanced redox capacity concerning their constituent counterparts. This study affords a promising approach to constructing Bi2O3-based Z-scheme composites with a suitable microstructure and Bi2O3/Bi2S3 phase ratio for photoactive device applications.

Uracil derivative-assisted universal synthesis of defective 2-dimensional porous flaky carbon nitride for efficient photocatalytic CO2 reduction

In this paper, three novel defective two-dimensional lamellar carbon nitride were successfully synthesized by molecular self-assembly using melamine and cyanuric acid as supramolecular aggregates and introducing three different uracil derivatives (5-formyluracil, 5-acetyluracil, uracil-5-carboxylic acid). In our previous work, we found that the introduction of thymine into supramolecular precursors has good photocatalytic oxidation ability for NO. On this basis, we discovered that by introducing uracil derivatives as ligands for supramolecular aggregates, not only two-dimensional porous sheet nanostructures can be constructed, but also abundant nitrogen and oxygen defects can be introduced, which is supported by various characterizations. These defects can effectively modulate the electronic structure of carbon nitride and thus improve the separation of photogenerated carriers. In addition, the introduction of uracil derivatives affects the energy band structure of the catalyst, and these are important factors affecting the catalytic activity. Compared with bulk carbon nitride, the synthesized materials exhibited significantly enhanced photocatalytic CO2 reduction activity under mild conditions, with CO yields of 10.34, 28.65, 32.28, and 36.48 μmol g−1h−1 for BCN, CNU2.5, CNF2.5, and CNY2.5, respectively. More importantly, with the support of in situ DRIFTS, we proposed the reaction mechanism of photocatalytic reduction of CO.

Biomass waste derived heteroatom doping porous carbon sheets for high performance supercapacitor

Porous carbon sheets exhibit a big open flat layer with large surface area, short ion transfer distance, which has attracted massive research as electrode materials for supercapacitors. Here, O, N, and P co-doped porous carbon sheets (ONPC) were developed by one-step activation way using sunflower straw as the carbon source, NH4H2PO4 as phosphorus the source, and nitrogen source, and then activated by KHCO3. Benefiting from the suitable specific surface area and massive O (13.98 at%), N (7.43 at%), and P (0.81 at%) functional groups, the ONPC-700 electrode exhibits a specific capacitance of 340 F g−1 at 0.5 A g−1, superior electrochemical stabilization with the capacitance retention rate of 100.5% after 10,000 cycles. More interestingly, the assembled symmetric supercapacitor (ONPC-700//ONPC-700) achieves an energy density of 22.0 Wh Kg−1 and superior electrochemical stabilization. The above excellent results indicate that this paper offers a feasible and simple strategy for preparing biomass-based heteroatom doped porous carbon sheets for supercapacitors.

Hydrogel Microrobots Self‐Assembled into Ordered Structures with Programmable Actuation

Sub‐millimeter robots—microrobots—that can autonomously perform mechanical work at the microscale would radically change new areas of human activity such as micromanipulation, microfabrication, or healthcare. Sets of identical microrobots that can connect into different, larger structures open the possibility for a “universal” microrobotic unit that fulfills a large variety of functions derived from the structure that multiple units can be assembled into. The capability of individual hydrogel microcrawlers to self‐assemble under confinement into periodically ordered planar structures is demonstrated. Subsequently, these can be bound together using light to form a solid porous sheet. The lateral shape of the sheet is imprinted during the binding process. Furthermore, the sheets bend into 3D structures, where the bending direction can be programmed. The resulting structures actuate anisotropically when exposed to heat or laser illumination and can be designed for various modes of operation, such as manipulation or untethered locomotion. The formation of ordered microstructures from individual mobile robots enables easier transport and remote assembly of these structures at the place of interest without the need for direct intervention.

Preparation of novel porous hydroxyapatite sheets with high Pb2+ adsorption properties by self-assembly non-aqueous precipitation method

Herein, novel porous hydroxyapatite sheets with high pore homogeneity are prepared via a self-assembly nonaqueous precipitation method. The optimized calcium source, phosphorus source and solvent are calcium acetate, disodium hydrogen phosphate and glycerin, respectively. Hexagonal plate-like hydroxyapatite polycrystals form in the replacement-rearrangement groups of raw materials and grow along the (002) crystal plane of the hydroxyapatite phase. Large hydroxyapatite sheets have homogeneous pore sizes of approximately 110 nm and thicknesses of approximately 20 nm. The hydroxyapatite sheets prepared via the nonaqueous precipitation method are highly active carbonate apatite. In a nonaqueous environment, assembly units of hexagonal plate-like hydroxyapatite polycrystals are triggered by the replacement and rearrangement of groups in the raw materials, and they self-assemble to form large hydroxyapatite sheets in the form of edge sharing. The degree of curvature in the process of plate-like hydroxyapatite self-assembly triggers the formation of porous hydroxyapatite sheets. This material has excellent adsorption performance for Pb2+ ions. The material developed in this work has wide application prospects in the fields of adsorption treatment of wastewater containing toxic ions (such as Pb2+), and it is expected to become a novel type of lead ion adsorbent.

Coordination chemistry-assisted ecofriendly preparation of Fe2O3 nanoparticles embedded in hierarchical carbon for improved lithium storage

The green and facile synthesis of high performance anodes is of significant importance for development of lithium ion batteries (LIBs). Herein, a novel coordination chemistry-assisted method is demonstrated to successfully prepare a superior performance Fe2O3/C composite anode for LIBs. This method does not involve time-consuming pre-preparation of carbon materials and use of expensive sophisticated instruments and multiple harmful reagents, exhibiting relatively green and facile features over most of other methods. This Fe2O3/C composite consists of Fe2O3 nanoparticles embedded in a porous carbon sheets assembled hierarchical matrix. Moreover, it finds that this beneficial architecture endows as-prepared Fe2O3/C with improved conductivity, enhanced kinetics, high capacitive contribution and good structure stability. In consequence, this Fe2O3/C anode exhibits superior electrochemical properties such as high capacity, long life and good rate performance, with 756.1 and 545.4 mA h g−1 after 200 cycles at 200 and 1000 mA g−1, respectively. The relatively ecofriendly and simple preparation process as well as superior electrochemical performance make this Fe2O3/C anode promising for LIB application. This work also offers a guiding significance for designing and developing ecofriendly and facile preparation methods of other metal oxides/carbon composites for advanced LIB anodes.

Development of Natural Active Agent-Containing Porous Hydrogel Sheets with High Water Content for Wound Dressings

This work was concerned with the fabrication of a porous hydrogel system suitable for medium to heavy-exudating wounds where traditional hydrogels cannot be used. The hydrogels were based on 2-acrylamido-2-methyl-1-propane sulfonic acid (AMPs). In order to produce the porous structure, additional components were added (acid, blowing agent, foam stabilizer). Manuka honey (MH) was also incorporated at concentrations of 1 and 10% w/w. The hydrogel samples were characterized for morphology via scanning electron microscopy, mechanical rheology, swelling using a gravimetric method, surface absorption, and cell cytotoxicity. The results confirmed the formation of porous hydrogels (PH) with pore sizes ranging from ~50–110 µm. The swelling performance showed that the non-porous hydrogel (NPH) swelled to ~2000%, while PH weight increased ~5000%. Additionally, the use of a surface absorption technique showed that the PH absorbed 10 μL in <3000 ms, and NPH absorbed <1 μL over the same time. Incorporating MH the enhanced gel appearance and mechanical properties, including smaller pores and linear swelling. In summary, the PH produced in this study had excellent swelling performance with rapid absorption of surface liquid. Therefore, these materials have the potential to expand the applicability of hydrogels to a range of wound types, as they can both donate and absorb fluid.

Steady 3-D Magneto Hydrodynamics-Casson Moving Fluid Across a Porous Sheet as it is Being Linearly Stretched Out Thermal Radiation and Prandtl Number: FEM Approach

In this research paper, the study focuses on results of heat radiation on Casson fluid flowing in three dimensions toward a linearly stretched sheet packed with porous media when a magnetic field is present, as well as when Prandtl number effects when there is a porous medium involved. The Roseland approximation, which integrates a heat radiation’s impact into the energy equation, is used to incorporate thermal radiation into this research endeavour. To be used in this fluid flow the basic governing partial equations for this fluid flow were changed from linear ordinary differential equations by converting non-linear partial equations with similarity variables are utilised. The numerical solutions to the resultant linear ordinary duality equations are obtained by the use of the finite element approach. Graphical representations of the effectiveness and accuracy of this finite element approach are provided for a variety of characteristics as the permeability (K), Casson fluid (β), and magnetic field (M) parameters Stretching sheet parameter (C), Prandtl number (Pr) and Thermal radiation component (R). and conditions. A comparison of our numerical findings with previously published data (S. Nadeem, R. U. Haq, N. S. Akbar, and Z. H. Khan, Alexandria Eng. J. 52, 577 (2013)) reveals a a high level of consistency among the two sets of data.

Unveiling Superior Capacitive Behaviors of One-Pot Molten Salt-Engineered B, N Co-Doped Porous Carbon Sheets.

Heteroatom-doped porous carbon materials with distinctive surface properties and capacitive behavior have been accepted as promising candidates for supercapacitor electrodes. Currently, the researches mainly focus on developing facile synthetic method and unveiling the structure-activity relationship to further elevate their capacitive performance. Here, the B, N co-doped porous carbon sheet (BN-PCS) is constructed by one-pot pyrolysis of agar in KCl/KHCO3 molten salt system. In this process, the urea acts as directing agent to guide the formation of 2D sheet morphology, and the decomposition of KHCO3 and boric acid creates rich micro- and mesopores in the carbon framework. The specific capacitance of optimized BN-PCS reaches 361.1 F g-1 at a current density of 0.5 A g-1 in an aqueous KOH electrolyte. Impressively, the fabricated symmetrical supercapacitor affords a maximum energy density of 43.5Wh kg-1 at the power density of 375.0W kg-1 in 1.0mol L-1 TEABF4 /AN electrolyte. It also achieves excellent long-term stability with capacitance retention of 91.1% and Columbic efficiency of 100% over 10000 cycles. This study indicates one-pot molten salt method is effective in engineering advanced carbon materials for high-performance energy storage devices.

Green synthesis of mesoporous 2D Mn2O3/rGO nanocomposite for effective removal of methyl orange

Abstract Green synthesis of di-manganese trioxide mesoporous structure (super nano porous) sheets (Mn2O3-rGO-NS), Graphene oxide nano sheets (GO) and Mn2O3-rGO-NS nano sheets composite (Mn2O3-rGO-NS) were prepared via Thermal decomposition, seconds timescale water electrolytic oxidation and sonication method respectively. The prepared samples were characterized via X-ray diffraction, FESEM, TEM , and FTIR. Average crystallite size was found about 38 and 26 nm for Mn2O3-NS and Mn2O3-rGO-NS, respectively. Mn2O3-rGO–NPs morphology reveal nano porous sheets within average 35 nm and 26 nm in pores diameter and thickness respectively. Mn2O3-NS act distributed on and between graphene sheets creating macro and nano pores. The obtained results showed that the characteristics of the α-Mn2O3-rGO-NS sheets were improved by the addition of rGO sheets. Methyl orange (MO) dye adsorption onto Mn2O3-rGO-NS composite was investigated at various adsorption parameters, including pH, adsorbent quantity, and time. It was discovered that the adsorption behavior complies with the intra-particle diffusion model and the Friedendlich isotherm. Methyl orange in aqueous media may be eliminated 99.3% by Mn2O3-rGO-NS composite.

Preparation of Hierarchical Porous and Tunable Silicon Microenvironment SAPO-18 Sheets for Methanol-to-Olefins

In this study, hierarchically porous SAPO-18 catalysts with abundant intracrystalline mesopores were designed and fabricated with a cost-effective non-surfactant cationic surfactant (polydimethyldiallylammonium chloride, PDADMAC) as a pore-forming agent, morphology regulator, and silicon inducer by a one-step method. PDADMAC promoted the introduction of silicon atoms in the SAPO-18 framework, making the hierarchical porous SAPO-18 sheets present abundant optimized acidity. With the combination of porous structure and suitable acid density, the hierarchical porous SAPO-18 sheets exhibited a threefold improvement in catalytic lifetime and a 4% increase in ethylene and propylene selectivity during the methanol-to-olefin (MTO) reaction, compared with the conventional SAPO-18 zeolite.

Hierarchically nitrogen-doped carbon hollow microspheres assembled with loose and porous magnetic carbon sheets for enhanced microwave absorption

Combining hollow materials with magnetic particles to construct hierarchical structures favors enhancement of microwave absorption properties. However, the fabrication of the well-defined materials possessing both hollow and hierarchical features still faces a huge challenge. Herein, a facile two-step method is developed to synthesize hierarchically nitrogen-doped carbon hollow microspheres assembled with loose and porous magnetic carbon sheets. Especially, many magnetic Fe/Fe3C NPs covered with N-doped graphitic layers are embedded in the mesoporous N-doped carbon sheets layers. Benefited from the special structure, the optimal nitrogen-doped carbon hollow microspheres exhibit an excellent microwave absorption property with an EAB of ∼4.00 GHz at a thickness of 2.5 mm and the minimal reflection loss of −39.87 dB at a frequency of 7.76 GHz, while the filler ratio is only 10 wt% in the paraffin wax. Electromagnetic parameters analysis reveals that unique hierarchical structure and rich heterogeneous interfaces result in the enhancement of dielectric and magnetic losses as well as optimized the impedance matching. The computer simulation technology (CST) simulation further verifies the practical applicability of the optimal nitrogen-doped carbon hollow microspheres. This work provides an effective way for the efficient synthesis of hierarchical and hollow materials for microwave absorption.