Coal gasification fine ash (CGFA) possesses both hydration reaction activity and notable electromagnetic properties. Its application in cement-based materials not only enables the high-value utilization of industrial waste but also helps to addresses the prohibitive cost that has hindered the widespread adoption of traditional cement-based electromagnetic shielding materials. However, research in this area remains relatively scarce. In this study, CGFA was prepared by ball milling into three particle-size distributions: untreated ash (D0.9 = 249.1 mu m), medium particle size (D0.9 = 51.7 mu m), and small particle size (D0.9 = 10 mu m). The effects of CGFA particle size on the structure, hydration behavior, and electromagnetic shielding performance of cement-based materials were investigated systematically. The results indicate that, although reducing CGFA particle size partially damages the porous structure of the carbon component, it markedly improves the dispersibility of CGFA within the cement matrix, thereby enhancing mortar compactness. After grinding, the reactive components in CGFA are further activated, promoting cement hydration and improving mechanical properties. When small-particle CGFA replaces 40% of the cement, the composite mortar still attains a compressive strength of 21.1 MPa, meeting the M20 load-bearing requirement of the standard. In addition, incorporation of CGFA significantly enhances the electrical conductivity and electromagnetic shielding performance of cement mortar. Small-particle CGFA more readily forms a well-developed conductive network in the mortar and lowers the percolation threshold, resulting in superior SE compared with untreated CGFA in the 1.13-3.95 GHz frequency band; conversely, in the 3.95-8.2 GHz band, the untreated CGFA exhibits better shielding performance. This work provides comprehensive and systematic data support for related research, while establishing reference ranges for particle size and content parameters in engineering applications.

Coal gasification fine ash (CGFA) is a byproduct of coal gasification technology, contains approximately 40 % carbon content traditionally considered difficult to utilize effectively in construction materials. However, this carbon exhibits excellent electromagnetic (EM) properties and, if properly developed, could impart excellent EM protective functionality to human settlement. This study systematically investigated the influence of particle size on the structure and EM wave loss mechanisms of CGFA by processing the material into three distinct size fractions via ball milling: Group A (D0.9 = 249.1 mu m), Group B (D0.9 = 51.7 mu m), and Group C (D0.9 = 10.0 mu m). The results indicate that the specific surface area of CGFA is dominated by its porous carbon structure. Reducing particle size leads to destruction of the pore structure and consequently to a decrease in specific surface area. Larger carbon particles exhibit superior electrical conductivity, their abundant porosity and higher specific surface area provide more interfaces, thereby significantly enhancing resistive loss and polarization loss. However, this also causes imbalanced impedance matching in CGFA/paraffin composites, which limits their EM wave absorption performance. As particle size decreases, impedance matching is optimized, among the samples, the group C specimen (30% loading, 15 mm thickness) achieved the best reflection loss of-27.66 dB at 5.8 GHz. These findings demonstrate that particle size modulation can effectively tune the EM loss mechanisms of CGFA to meet different engineering requirements.

This study systematically investigates the effects of varying steel fiber contents on both mechanical and electromagnetic shielding properties of Carbon Black cement mortar. Comprehensive evaluations were conducted, including flexural strength and compressive strength measurements, electrical conductivity tests, and electromagnetic shielding performance simulations across the 1–18 GHz frequency range. The experimental results demonstrate that steel fiber incorporation significantly enhances flexural strength (maximum 10.6 MPa, 22.3% improvement), compressive strength (peak 56.1 MPa, 32.3% increase), and electrical conductivity (optimal 37.8 mS/m, 517.64% enhancement). However, due to the random orientation and distribution characteristics of steel fibers, no consistent correlation between fiber content and conductivity was established. Regarding electromagnetic shielding performance, a progressive improvement was observed with increasing steel fiber content. The composite exhibited an average shielding effectiveness of 14.93 dB at the optimal fiber dosage of 200 kg/m3, while achieving a maximum total shielding effectiveness of 27.25 dB (814% enhancement) at 18 GHz.

Waste iron powder (WIP) generated from the steel industry poses a considerable environmental threat to a certain extent. The utilization of WIP as a replacement for standard sand in the fabrication of electromagnetic wave (EMW) absorbing cement mortars is investigated. The findings demonstrate that WIP possesses excellent magnetic properties. The mortar containing 30 %WIP achieves a minimum reflection loss (RL) of -12.78 dB at 3.55 GHz, with an effective absorption bandwidth (EAB) of 14.41 GHz for RL < -5 dB. Additionally, carbon black (CB), serving as a resistance loss material, enhances the electrical conductivity and EMW absorbing performance of the WIP-filled mortar in 1.1-18 GHz, while also reducing its density. The mortar with 10 %WIP and 2 %CB demonstrates a minimum RL of -10.41 dB at 1.1 GHz, with an EAB (RL < -5 dB) of 14.91 GHz. The minimum flexural and compressive strength remain above 8.5 MPa and 35 MPa, respectively, meeting the requirements for conventional engineering applications. In short, the mortar incorporating WIP and CB is a candidate as plastering mortar or enclosure materials for non-bearing structure in building engineering, which not only offers an effective EM pollution solution but also provides an environmentally beneficial method for recycling WIP, mitigating pollution associated with industry waste.

Lightweight and flexible electromagnetic wave (EMW) absorbing materials have become increasingly essential for modern electronic equipment operating in complex environments, addressing the growing challenges of EM pollution. This study fabricated an EMW absorbing coating using nano carbon black (CB) and graphene sheets (GSs). The synergistic combination of two-dimensional flakes and zero-dimensional spherical structures established a "point-to-surface" contact configuration, forming a more efficient electron transport network and thereby enhancing interfacial contact efficiency. Furthermore, a flexible absorbing fabric was developed by integrating this coating with basalt fiber fabric (BFF) via a doctor-blading process. The basalt fiber helps to optimize impedance matching, while its unique interwoven structure promotes multiple internal reflections and refractions of EMW, significantly improving the absorption performance. With a CB/GSs filler content of 20%-25%, the fabric achieved optimal EMW absorbing properties. In the X-band, the reflection loss (RL) reached -38.75 dB with a maximum effective absorption bandwidth (EAB) of 3.53 GHz. In the Ku-band, the minimum RL was -32.9 dB with a maximum EAB of 3.36 GHz. Compared to plain basalt fiber fabric, the absorbing fabric exhibits both higher mechanical strength and excellent hydrophobic properties, enabling it to adapt to more complex application environments. This work provides a suitable approach for the industrial development of EMW absorbing materials.

This study first established and experimentally validated an optimal impedance matching model for flat-plate cement-based wave-absorbing materials. Based on this model, finite element simulations were progressively developed from planar structures to impedance gradient structures and finally to geometrically gradient impedance structures. The interactions between electromagnetic (EM) waves and the complex cement-based structures were systematically investigated, yielding design principles for achieving optimal impedance matching through structural parameter optimization. The results indicate that thinner cement-based materials are best suited for planar structures, where EM wave attenuation primarily relies on refraction and multiple reflections at aggregate interfaces, achieving absorption through destructive interference. In contrast, thicker materials are more suitable for impedance gradient structures. Optimal impedance matching and wave absorbing performance are attained when the real part of the characteristic impedance curve exhibits a concave-downward shape while the imaginary part exhibits a convex-upward shape. Furthermore, pyramidal cement-based materials with geometrically gradient impedance structures demonstrate the best overall performance. Convex and concave pyramids showed complementary effects in terms of impedance matching and EM wave absorbing performance. This structural configuration consistently maintains a reflection loss below -5 dB across the 2-18 GHz frequency range, with optimal values reaching below -50 dB. Its performance is significantly influenced by the pyramid height and base length. This simulation method serves primarily for performance prediction and structural design of cement-based wave-absorbing materials, providing theoretical guidance for their intelligent development.

The present study explores the relationship between coal gas fine ash(CGFA)content and the electromagnetic performance of cement-based composites,and the modification effects of carbon black(CB),with particular focus on the electromagnetic property evolution in CB-CGFA systems at different formulation ratios.The experimental findings demonstrate that CGFA has a substantial impact on enhancing the electrical conductivity and complex permittivity of the composite material.The cement mortar demonstrates enhanced low-frequency(1-8 GHz)wave-absorbing characteristics.The numerical value of reflection loss(RL)exhibited a positive correlation with CGFA content,reaching an optimal value of-11.9 dB at 1.1 GHz for 2％CGFA con-tent.The addition of CB to CGFA cement mortar facilitates to enhance its electromagnetic performance through synergistic effects within the cement matrix.This addition exhibits enhanced complex permittivity,characterised by combined polarization and resistive loss mechanisms.The absorbing performance exhibited a non-monotonic relationship with CB content,achieving an optimal RL of-18.95 dB at 4.24 GHz for 2％CGFA with 0.75％CB.

The electromagnetic wave (EMW) absorption frequency band of cement-based materials lacks designability. Vitreous aggregates, as wave-transmitting materials, can improve the impedance matching of the cement matrix and adjust the absorption frequency band. To investigate the relationship between vitreous aggregates and absorption frequency bands, cement-based EMW absorbing materials were prepared using aggregates of varying particle sizes and volume ratios, supplemented by finite element simulations. The absorption performance and mechanisms were systematically analyzed. The results indicate that, at higher frequency bands, increasing the volume ratio or particle size of the vitreous aggregates can optimize impedance matching characteristics, enhance reflection loss (RL), and broaden the effective absorption bandwidth (EAB). Conversely, at lower frequency bands, reducing the volume ratio or particle size is necessary to improve overall performance. Throughout the entire frequency band, the average RL is minimally affected by the aggregates, with a difference of no more than -1.54 dB. When the absorption rate of EMW exceeds 90 %, effective protection is established in the high-frequency band, with the EAB reaching up to 6.57 GHz; when the absorption rate exceeds 80 %, effective protection can be achieved across the entire frequency band, with the EAB reaching up to 12.4 GHz. Finite element simulation results indicate that vitreous aggregates can alter the transmission direction and increase the loss paths of EMWs. The larger the particle size, the greater the angle of refraction for the EMWs. The strongest EM loss occurs between adjacent aggregates, followed by loss within the cement matrix. The thermal insulation performance of cement-based materials improves with increasing particle size of aggregates. Although there is a slight reduction in mechanical strength, it still exceeds the standard specifications for strength. This work provides guidance for the design of absorption frequency bands and the selection criteria for vitreous aggregates in cement-based EMW absorbing materials.

In order to address the challenge of balancing strength and high shielding performance in concrete, an ultrawideband electromagnetic shielding concrete was developed in this work by incorporating nano-scale carbon black, micro-scale graphite, and millimeter-scale steel fibers to construct a multi-scale hierarchical conductive network. The results demonstrate that the shielding concrete exhibits excellent mechanical and shielding properties. The electrical conductivity of the shielding concrete reaches up to 0.17 S/m. In the MHz frequency range, the average SE exceeds 30 dB, while in the GHz range, the SE is significantly higher, ranging between 65-109 dB. Meanwhile, the 28-day compressive strength of the shielding concrete remains above 45 MPa, complying with the Chinese National Standard GB50010.

In this paper, the effect of carbon black (CB) on the mechanical and electromagnetic performance of cement-based materials was investigated using modified polyether for CB dispersion. Results show that, with suitable CB content and dispersant ratio, the average pore diameter and compressive strength will be decreased and improved with the adding of CB. Moreover, as CB content increases, the electrical conductivity of cement mortar decreases notably. Notably, at a 3% CB content, changes in the electromagnetic properties of cement mortar were observed. Below 3% CB content, dispersants reduce electromagnetic parameters and increase electrical conductivity.

A novel lightweight foamed cement-based electromagnetic wave (EMW) absorbing material (Density<0.5 g/cm(3)) is prepared using secondary aluminum ash (SAA) as a foaming agent and carbon black (CB) as an efficient EMW absorbent, providing a new way to recycle SAA. The pore structure parameters, reflection loss (RL), mechanical strength and thermal conductivity are systematically investigated. The experimental test results indicate that the pore structure of cement matrix prepared by SAA exhibits better EMW loss performance than those prepared by traditional foaming agent. The analysis of the pore structure images indicates that the average pore size is reduced, and pore size distribution shifts towards smaller sizes due to the addition of CB. Furthermore, the roundness of pores is increased due to the formation of more irregular pores. Increasing CB content and thickness can reduce RL, enhance absorbing performance at low frequencies, and broaden effective absorbing bandwidth (EAB). The absorbing performance was tested using the arch reflection method in the frequency range of 1.1-18 GHz, the excellent absorbing performance and the widest EAB (RL<-10 dB) reach -36.34 dB and 14.46 GHz, respectively, at a thickness of 4 cm. Benefiting from excellent pore structure, the foamed cement-based material also exhibits better mechanical strength, and good thermal insulation properties are maintained after adding CB. The compressive and flexural strength can reach 2.18 MPa and 1.02 MPa, respectively, while the thermal conductivity remains below 0.122 W/(m center dot K).

The geometric gradient structure can meet the continuous gradient of impedance and realize the impedance matching between materials and free space. Thus, pyramidal absorbing cement mortar with a simple process and higher strength is designed and prepared to attenuate electromagnetic radiation. The reflection loss (RL) of wave absorbing cement mortar is measured in 1.1-18 GHz. The transmission process of electromagnetic wave (EMW) is analyzed using finite element method (FEM) and the idea of equivalent oblique incidence is proposed. The results show that carbon black (CB) is used to greatly increase EMW absorbing performance. The effective absorption bandwidth (EAB, RL < -5 dB) of flat mortar is higher than 12 GHz when the content of CB exceeds 1 % and the minimum RL is -19.4 dB. Compared with flat mortar, pyramidal composites have a sudden increase in high-frequency loss capacity through increasing the pyramid height and CB content. The RL of pyramidal composites with a 30 mm height and 3 %CB is less than -5 dB in the full frequency band and the minimum RL is -40.26 dB. The simulation results in 8-18 GHz indicate that the electric field within flat mortar presents a layered distribution which is hierarchical and predictable, and the pyramidal surface changes this distribution state of electric field. When EMW is incident vertically, it is refracted on the side face of pyramid, which is equivalent to EMW changing from transverse electromagnetic (TEM) wave at normal incidence to transverse magnetic (TM) wave or transverse electric (TE) wave at oblique incidence of EMW on the flat surface, which provides theoretical guidance for the design of absorbing mortar. Besides, the minimum compressive and flexural strength are still higher than 44 MPa and 8 MPa. Thus, the pyramidal absorbing mortar is a promising EMW absorber with broadband absorbing performance and high strength, which could be used for protecting buildings from electromagnetic radiation.

The microstructure, pore structure and changes in electromagnetic parameters of cement paste prepared with nano carbon black (CB) were analysed. The results showed that the addition of CB significantly influenced the pore structure of the cement paste, increasing the content of pores less than 100 nm and improving the overall pore structure. The use of dispersant further enhanced the dispersion of the CB and increased its filling effect. The addition of CB also had a significant impact on the compressive strength of the cement paste, with the presence of certain CB agglomerates reducing the compressive strength. However, when the CB content (CBC) was 0.5 wt%, the use of dispersant decreased the size of CB agglomerates and effectively increased the compressive strength. Scanning electron microscopy was conducted to assess the dispersion of the CB agglomerates within the cement paste; it was found that the size and quantity of the CB agglomerates could be reduced with the addition of dispersant. The change in the CB dispersion state slightly affected the electromagnetic parameters and wave absorption properties of the cement paste. These research results offer valuable insights for the design and application of CB-dosed cement pastes.

The electromagnetic wave (EMW) absorbing performance of cement-based materials incorporating expanded polystyrene (EPS) with varying particle sizes is comprehensively studied through a combination of experimental and simulation methods. The addition of conductive carbon black (CB) to the cement matrix significantly increases the conductivity and dielectric constant, thereby improving the loss capacity. The frequency shift behavior of single and three-layer absorbing materials adheres to the effective medium theory and interference cancellation principle. The enhancement in overall EM parameters leads to a shift of the reflection loss (RL) peak towards lower frequencies. For three-layer materials, an increase in the thickness of absorbent layer proves beneficial for enhancing absorption performance. Simulations can effectively model cement-based materials by employing uniform material settings, with the size of EPS particles serving as the primary variable. The simulation results reveal that an increase in EPS particle size, in both single-layer and multi-layer materials, causes a shift of the RL peak towards lower frequencies. Additionally, analysis of electric field mode distribution and EM power loss density distribution indicates that scattering at the curved EPS interface alters the propagation direction of EMWs, increasing opportunities for loss inside the cement-based material. Moreover, the three-layer absorbing material, with a density ranging from 850 to 900 kg/m3 and compressive strength exceeding 4 MPa, is suitable for EMW absorption in building envelope structures. In conclusion, an increase in EPS particle size and CB content leads to a low-frequency shift of the RL absorption peak. This discovery not only provides an empirical foundation for the development of absorption materials tailored to specific frequency bands but also offers an efficient approach for repurposing waste EPS of diverse sizes. Furthermore, the grading of EPS with different particle sizes has important practical significance for increasing the content of EPS and preparing lightweight cement-based materials.

Basalt fibers (BF)-reinforced double-layered resin composite with excellent absorption performance in X band (8.2-12.4 GHz) has been designed, choosing carbon black (CB) and nano-Fe3O4 as absorbent for absorbing layer and matching layer, respectively. The electromagnetic parameters of the composites were measured by vector network analyzer using waveguide method. The calculated result suggests that an increased amount of absorbent could significantly improve the microwave absorbability of the single-layered composites in the measured frequency. For double-layered composites, the optimum microwave absorption performance can be obtained by tailoring the electromagnetic parameters and thicknesses of each layer. The minimum reflection loss of -43.97 dB and full X band effective absorption can be achieved when the thickness of the matching layer (BF/Fe(3)O(4)10) and absorbing layer (BF/CB7.5) were 0.3 mm and 2.7 mm, respectively. Therefore, utilization of dielectric loss, magnetic loss absorbent and BF/resin double-layered structure has designed flexibility, and contributes to promote the development of high-performance microwave absorbing composites.

A novel electromagnetic (EM) wave absorption and heat storage dual-functional cement composite was developed by incorporating with carbon nanotubes (CNTs) and phase change microcapsule (PCM). The reflection loss (RL), EM parameter, latent heat, thermal inertia and mechanical properties were investigated in detail, the obtained results indicate that the PCM particles can improve the impedance matching of cement composites and introduce extra EM attenuation path of scattering and multiple reflection, broadening the bandwidth of RL less than −7 dB. An obvious heat storage capacity and better thermal inertia of cement composite can be attained by the addition of PCM, and the heating rate can be reduced approximately 47% when PCM content selected as 20%. The compressive strength and flexural strength of cement composites can be reduced observably, because of the increase of porosity and limitation of cement hydration process caused by PCM. However, considering the comprehensive properties of the developed dual-functional cement composite, the strength loss is acceptable, and it can be a candidate as plastering mortar or enclosure materials for non-bearing structure in building engineering.

The main aim of this paper is to mitigate the supercooling of erythritol using organic salts as nucleating agents. The pure erythritol exhibits significant volume effects and a strong supercooling tendency. When the aspect ratio of the ET is small, a metastable phase transition plateau at 105 degree celsius can be observed, and then, the metastable crystal slowly transforms into a stable crystal. Experimental results reveal that calcium pimelate (CaPi) has a positive influence on the supercooling elimination of erythritol. The 1 % CaPi/erythritol composite phase change material (CPCM) melts at 118 degree celsius and solidifies at 109 degree celsius with the latent heat of 344.86 J/g and 281.8 J/g, respectively. Due to the improved crystallization kinetics, the supercooling phenomenon measured by T-history method is basically eliminated. The melting heat is >300 J/g and the change of phase change temperature is less after 50 cycles. In order to simulate the real environment, the CPCM cools down by room temperature in air, and the chemical stability is good. The thermal conductivity of 1 % CaPi/ET increases by 23.2 %. In total, the CaPi/ erythritol CPCM is a new candidate to be used in waste heat recovery, solar energy medium temperature heat collection and other fields.

Based on impedance gradient principle, a three-layered lightweight and broadband electromagnetic wave (EMW) absorbing cement-based composite is designed and prepared using expanded polystyrene (EPS) and carbon black (CB) as wave-transparent and absorbent medium, respectively. The three-layer absorber indicates excellent EMW absorbing properties in 1.1-18 GHz frequency range due to the good impedance matching and attenuation capacity. The minimum value of reflection loss (RL) is -49.6 dB with a 7 cm thickness and an effective absorbent bandwidth (RL < -20 dB) of 14.32 GHz can be achieved at a thickness of 8 cm. Furthermore, the idealized EPScement/CB structure model is established and simulated by finite element method in X-band. The propagation process of EMW is visual and greatly affected by EPS, and the electric field distribution presents a circular loop. Here the Smith chart can be used to analyze the impedance source of each circular loop at different frequencies. What's more, the density of three-layered composites is between 170-250 kg/m3, meeting the requirements of lightweight, and the compressive strength of single-layer composite reaches about 0.65 MPa when the density is 350 kg/m3. Thus, the three-layer lightweight EPS-cement/CB composite is a promising EMW absorber with broadband absorption performance, which could be used for protecting buildings from electromagnetic interference.

The development of practical and efficient electromagnetic wave (EMW) absorbing materials is a challenging research problem. A mussel-inspired molecular structure regulation strategy using polydopamine to increase the roughness and functional groups of basalt fiber (BF) surface, which can improve the fiber interfacial adhesion. Herein, a novel BF-Fe3O4/CNTs heterostructure is synthesized through a dip-coating adsorption process. The three-dimensional network structure of Fe3O4/CNTs hybrid in situ anchored on the surface of BF, which endows the composite to have good intrinsic magnetic and dielectric properties. Modulation of EMW absorption performance by controlling the addition of CNTs, the minimum RL of BF-Fe3O4/7C reaches to -40.57 dB at a thickness of 1.5 mm with CNTs addition of 7%. The enhanced EMW absorption performance of BF-Fe3O4/7C heterostructure may be attributed to the synergistic effects of interfacial polarization between the hollow magnetic Fe3O4 spheres and CNTs, conduction loss, magnetic resonance loss and multiple reflection/scattering inside the BF. This work provides a simple pathway to design EMW absorbing materials with good environmental stability.

Abstract: Due to the complexity of the design of multilayer electromagnetic (EM) wave absorbing materials, it is difficult to establish the relationship between material parameters (type and filling ratios) and EM properties using traditional trial and error methods. Based on the measured EM parameters within a few materials and Boltzmann mixing theory, a database of EM parameters was thereafter built up. In this study, the genetic algorithm (GA) was used to design the multilayer wave-absorbing cement mortar. In order to verify this method, a multilayer mortar was fabricated and measured. The simulated and measured results are well consistent, which convincingly verifies computer-aided design. In addition, the optimized result expresses that the first layer as a matching layer guides EM waves into the interior of the material, while the other layers as absorption layers attenuate EM waves. The multilayer material may not meet the impedance gradient principle but still exhibits better EM wave absorption performance. The reflection loss (RL) of all optimized three layer sample is below –6.89 dB in the full frequency band and the minimum RL is –26.21 dB. This composite absorbing material and the GA method provide more design ideas for the design of future cement-based wave-absorbing materials and save a lot of time and material cost.