Durability failure is a challenge facing the sustainable development of society. How to improve the durability of structural concrete with low cost and high efficiency is a key problem to be solved. This review represents the research progress on durability enhancing admixtures in concrete crack control, microstructure regulation and reinforcement rust resistance improvement, and points out the existing problems of various admixtures.

1) Concrete crack control is a premise of structural concrete durability improvement. However, how to further improve the effectiveness and adaptability of admixtures according to the changes of concrete material system characteristics and environmental requirements is a major development direction. In addition, toughness enhancement and self-healing admixtures are still in the research stage, and the key properties are still unclear. How to realize the application needs, further reveal the structure-activity relationship of key materials and achieve the improvement of toughness and self-healing properties is a problem worthy of in-depth study.

2) The control of concrete microstructure is a key to improving the durability of concrete. Air entraining agent, pore hydrophobic agent and nano-pore compacting agent are effective technical means to enhance concrete microstructure, which can solve the durability failure problem of concrete under freeze-thaw, sulfate attack and chloride ion attack. However, for coupled corrosion environment, there are still insufficient mutual adaptability of various admixtures applied together, and a further research is needed. In addition, the relations among air entrainment agent, pore hydrophobic agent, nano densifier, cement hydration, stable regulation/optimization of pore structure, and the resulting durability impact mechanism are still unclear, which need to be further investigated.

3) The improvement of rust resistance of steel bars is a fundamental to the improvement of structural concrete durability. Inorganic and organic rust inhibitors are important components of rust inhibitors, and the reasonable use of different kinds of rust inhibitors is a key to achieve the improvement of rust resistance performance of steel bars in complex systems. The corrosion protection and repair of structural concrete can be improved via different application methods such as internal mixing, external coating, electromigration and pressure penetration. The future development direction of rust inhibitors can be green and intelligent, but it still needs to be further studied in combination with practical applications.

Although the durability of concrete is extremely complex, admixtures have some technical advantages in improving the durability of concrete. In the future, it is necessary to further analyze the micro-action mechanism and structure-activity relationship of admixtures, and propose an effective method of structural design and preparation of admixtures by theoretical calculation (i.e., molecular simulation, artificial intelligence and other theoretical analysis). Also, slow and controlled release technologies such as microcapsule coating, layered and porous material loading are used with the characteristics of cement hydration to enhance the durability and improve the adaptability of admixtures to cement concrete, thus realizing the efficient use of admixtures in concrete systems at regular and fixed points, avoiding the influence of admixtures on cement hydration, microstructure formation and long-term performance, and achieving an accurate control of structural concrete durability throughout the life cycle.

The preparation of B₄C-SiC ceramics via reaction sintering is a low-cost method, and this route is suitable for large-sized and complex-shaped products. Although significant progress is achieved in the preparation of reaction sintered B₄C-SiC ceramics, some challenges still remain in the scientific research and practical application. The reaction sintered B₄C-SiC ceramics have reached the industrial production stage; however, the residual Si phase with low hardness and stiffness contained in the B₄C-SiC ceramics can lead to a decrease in the performance, restricting their applications in the high-temperature field. New methods and processes still need to be explored to produce low Si or Si free reaction sintered B₄C-SiC ceramics. The formation mechanism of the microstructure of reaction sintered B₄C-SiC ceramics and its effect on the mechanical properties of B₄C-SiC ceramics are unclear yet, and the further in-depth exploration is needed through theoretical calculations and characterization techniques. The existing investigation for reaction sintered B₄C-SiC ceramics mostly focuses on conventional mechanical properties evaluation, and other mechanical properties are seldom reported. The impact strength and tribological properties of reaction sintered B₄C-SiC ceramics also need to be investigated deeply.

Although the favourable dielectric property of ceramic aerogel and fiberboard is proved in the selection of lining materials for microwave sintering, some problems of operating temperature still remain in the practical application. For ceramic firebrick, compared with nitride ceramics (i.e., Si₃N₄、SiAlON and Si₂N₂O), some porous oxides ceramics (i.e., fused quartz, alumina, silicate and hosphate ceramics) become a research hotspot because of the lower cost and better antioxidant properties. All the materials show some advantages in mechanical properties and dielectric properties. For instance, fused quartz with relatively stable dielectric properties has a lower operating temperature. Alumina ceramics have a higher operating temperature, but their thermal shock resistance needs to be improved and its dielectric properties have a temperature dependence. Mulite ceramics have excellent characteristics such as high melting point (i.e., 1830 ℃), low thermal expansion coefficient (i.e., 4.5×10^-6 K^-1), and low thermal conductivity, which can be used in air at 1750 ℃ without high temperature oxidation. In addition, mulite ceramics also have the superior dielectric properties (i.e., ε is about 3-6, tanδ is about 10^-3). Some refractory materials with mullite as a main component are commonly used as lining materials in conventional high-temperature furnace. Furthermore, according to the existing studies, the increase of porosity can effectively reduce the dielectric constant of materials, and has a negative impact on the mechanical properties of materials. In this case, mullite ceramics are easy to form grains with acicular morphology during sintering, which is beneficial to maintaining high mechanical properties of the material at a high porosity. However, some challenges still remain in the scientific researches and practical application, such as some related studies on the dielectric properties at high temperatures are limited at<1200 ℃, but it is far from enough for the lining materials of microwave kiln, in which the working temperature can often reach 1700 ℃. The change of the transmittance of materials at higher temperatures is still of great research value. Also, it is necessary to optimize the dielectric constant test system at high temperatures. Finally, some novel material systems of oxides ceramic in a largescale need to be further explored for the microwave sintering application. Meanwhile, exploring the relevance between microstructure and properties and further accelerating the upgrading and application of ceramic based wave-transmitted materials in microwave sintering technology become some research hotspots, which can reduce the pollution and carbon emissions caused by the use of industrial kilns and lay a foundation for the realization of 'carbon neutrality'.

This review represents the research advancements in high-temperature insulation materials (i.e., water-resistant ceramic fiber insulation tiles, insulation blankets, and aerogels). Some strategies for enhancing their water resistance, such as the application of high-emissivity coatings, chemical vapor deposition, and modification with organic hydrophobic groups, are described. These materials possess a significant application potential at multiple fields due to their low density, robust water resistance, and efficient thermal insulation properties. Nevertheless, some challenges persist in maintaining water resistance at high temperatures, simplifying manufacturing processes, and developing novel materials. A future research should prioritize enhancing the water resistance of materials at elevated temperatures, streamlining production processes, and innovating novel materials. In addition, the stability and durability of these materials in practical applications also need to be further investigated to facilitate the technological advancements and industrial upgrading.

One of the major reasons for the failure of thermal barrier coating materials is the corrosion caused by the reaction between aeroengine thermal barrier coating materials (TBC) and V₂O₅+Na₂SO₄ in fuel under high-temperature service conditions. Conventional TBCs are difficult to meet the increasingly harsh high-temperature service environment. It is thus necessary to develop new and more corrosion-resistant thermal barrier coating materials. Among the materials to replace conventional TBC, La₂(Zr_0.7Ce_0.3)₂O₇(LZC) ceramics are considered as potential TBC candidates due to their high sintering resistance, low thermal conductivity and high thermal expansion coefficient. Also, the thermal conductivity of LZC can be effectively reduced by using Re³⁺ with large mass and small radius doping at La³⁺. Therefore, the modified (La_0.5Gd_0.5)₂(Zr_0.7Ce_0.3)₂O₇ (LGZC) doped with Gd³⁺, which is a rare-earth element and has a smaller ionic radius, can further reduce the thermal conductivity of the material and improve the mechanical properties of the material through fine-grain strengthening. However, the existing reports on the hot corrosion resistance of V₂O₅+Na₂SO₄ molten salt of LZC and LGZC materials are more limited to the strong corrosive properties at < 1050 ℃, while the actual service temperature of the coating often exceeds 1200 ℃.

In this work, ZrO₂, La₂O₃, Gd₂O₃, CeO₂ and other oxide powders were used as raw materials, and LZC and LGZC ceramic samples were prepared by a high-temperature solid-state reaction method. A typical mixed salt of V₂O₅+Na₂SO₄ (in a molar ratio of 1∶1) was used as a corrosive medium. V₂O₅ and Na₂SO₄ powders were mixed. The mixed powder was evenly spread on the surface of the ceramic sample at a concentration of 10 mg/cm², and then the coated ceramic sample was placed in a box-type resistance box and treated at 900, 1000, 1100 and 1250 ℃ for 5 h for thermal corrosion, respectively. The phase composition of LZC and LGZC samples before and after hot corrosion was determined by a model D8 X-ray diffractometer (XRD, Bruker Co., Germany). The microstructure and morphology were characterized by a model Sigma 500scanning electron microscope (SEM, ZEISS Co., Germany) equipped with energy dispersive spectrometer (EDS).

LZC and LGZC ceramic specimens with a single pyrochlorite structure were synthesized. After corrosion, the diffraction peak of LGZC reduces, compared to that of LZC ceramic samples. There are mainly (La, Ce, Gd) VO₄, t-ZrO₂ and m-ZrO₂ on the surface according to the SEM images and EDS results. The content of (La,Ce,Gd) VO₄ increases with the increase of temperature in the range of 900-1100 ℃, and decreases after corrosion at 1250 ℃. From the micromorphology after corrosion, the ceramic surface of LZC specimens after corrosion at 900-1100 ℃ is mainly rod-like grains and granular clusters, while LGZC has more rod-like grains rather than granular grains. After corrosion at 1250 ℃, the surface of the LGZC specimen is granular crystals with intracrystalline pores. LZC and LGZC both forman obvious corrosion layer at 900-1100 ℃, and the thickness of the corrosion layer increases with the increase of temperature, and the corrosion layer becomes the thickest at 1100 ℃ (i.e., 38 μm and 35 μm), respectively. However, after corrosion at 1250 ℃, the corrosion layer does not form and the corrosion depth decreases, and the darker molten salt penetrates further downward, showing two completely different microscopic morphologies. Also, the corrosion depth of LGZC is smaller than that of LZC at different temperatures.

LZC and LGZC ceramic materials reacted with V₂O₅+Na₂SO₄ at 900-1100 ℃ to form a relatively dense corrosion reaction layer, and the corrosion reaction degree increased with the increase of temperature, and the reaction was most intense at 1100 ℃. The hot corrosion mechanism of LZC and LGZC ceramic materials at 900-1250 ℃ followed Lewis's acid-base law and Gibbs's free energy. The relative alkalinity of LGZC decreased, and the corrosion depth of LGZC was smaller than that of LZC at different temperatures due to the doping of Gd₂O₃. The corrosion resistance of ceramic materials was reflected in the corrosion depth, the smaller the corrosion depth, the stronger the corrosion resistance of the ceramic materials. Therefore, LGZC was more resistant to V₂O₅+Na₂SO₄ corrosion than LZC in this case. After the temperature increased to 1250 ℃, neither of the two samples formed a dense corrosion reaction layer, and the corrosion depth was smaller than that after corrosion at 1100 ℃ because the viscosity of NaVO₃ decreased with the increase of the corrosion temperature to 1250 ℃ and blocked the pores in a short time, thus preventing a further penetration of the molten salt.

Sm²⁺ ion exhibits a broad absorption band in the ultraviolet-visible region due to its 5d state absorption, which can be tuned by crystal field effects and co-doping with other ions without causing self-absorption during 4f→4f emission transitions. Sm²⁺ ion also holds significant research interest in fields such as fluorescence lighting, photocatalysis, scintillation, temperature sensing, pressure sensing, and radiation dose monitoring. Fluorosilicate glasses doped with Sm²⁺ ions have promising applications in optical storage and information encryption. However, the efficient reduction of Sm³⁺ ion to Sm²⁺ ion remains a challenge due to the relatively low reduction potential of Sm³⁺/Sm²⁺. This paper proposes a simple and cost-effective method for preparing Sm²⁺-doped fluorosilicate glass in ambient air atmosphere.

The nominal base molar composition was 52SiO₂-16Al₂O₃-6AlF₃-7.5BaF₂-18NaF-0.5Sm₂O₃. Al particles were added to a raw material at different mass fractions (i.e., 0%, 0.04%, 0.08%, 0.20%, 0.60%, and 0.80%, respectively). 25 g of analytical-grade raw material was mixed in required proportions and ground in an agate mortar for 15 min. The ground mixed material was placed in an alumina crucible covered with alumina and graphite plates and heated in a high-temperature elevator furnace in air at 1 550 ℃ for 30 min. Afterwards, the molten glass was poured onto a graphite plate and rapidly pressed flat using a stainless steel mold to form glass samples. These glass samples were labeled as G0, G0.04, G0.08, G0.20, G0.60, and G0.80, corresponding to the amount of elemental Al added in the raw materials. Finally, the glass samples were cut and polished to a thickness of 1 mm for the spectral measurements.

To investigate the effect of annealing temperature on the stability of Sm²⁺ ion, the samples G0.04 and G0.60 were selected for heat-treatment at 440, 460, 480, 500 and 520 ℃, respectively. We also investigated the effect Sm²⁺ doping concentration on the luminescence properties of glass samples. To ensure the effective reduction of Sm ions, the concentration of Sm ions in the glass samples was varied at a metallic Al content of 0.80%. The nominal molar composition of the glass was 52SiO₂-16Al₂O₃-6AlF₃-7.5BaF₂-18NaF-xSm₂O₃ (i.e., x=0, 0.062, 0.125, 0.250, 0.500, and 1.000, respectively).

At Sm doping amount of 1% (in mole fraction), the characteristic emission of Sm²⁺ increases, while that of Sm³⁺ decreases with increasing Al content in the raw materials. At Al doping content of 0.60% (in mass fraction), the characteristic emission peak of Sm³⁺ ion completely disappears. These results demonstrate that the incorporation of metal Al during glass melting enables efficient, stable and controllable conversion of Sm³⁺ ion to Sm² ion.

At Al doping content of 0.04%, no crystallization peaks appear in either the original sample or the heat-treated samples at various temperatures. However, at Al doping content of 0.60%, the crystallization peaks appear even before heat-treatment, corresponding to the diffraction plane (220) of Si. The addition of metallic Al in the raw materials can affect the crystallization behavior of the glass. The sample G0.04 exhibits a dramatic decrease in the fluorescence intensity as the heat treatment temperature increases. During this process, a reversal phenomenon occurs in the relative intensities of the fluorescence peaks at 600 nm and 683 nm. This indicates that some of the Sm²⁺ ions in the G0.04 sample were oxidized during the heat treatment process. In contrast, for the sample G0.60, the relative intensities of the fluorescence peaks at 683 nm and 600 nm remain unchanged after heat- treatment at various temperatures. An increase in Al doping content contributes to maintaining the stability of the Sm²⁺ valence state at higher temperatures. This phenomenon may be attributed to the formation of a number of low-valence silicon species surrounding Sm²⁺ ions in the glass at a greater Al doping content. This arrangement potentially prevents the oxidation of Sm²⁺ ion by Si⁴⁺ ion during heat-treatment.

The results show that the transmittance of the glass samples in the 300-600 nm range rapidly decreases, and the absorption bands gradually red-shift towards longer wavelengths as Sm doping content increases. Under 350 nm excitation, the fluorescence intensity at 683 nm gradually increases with increasing Sm doping content. However, it suddenly decreases when the Sm doping concentration reaches 1% (in molar fraction, same hereafter), which can be attributed to concentration quenching. The effect of concentration quenching on the luminescence is further corroborated by the fluorescence lifetime decay curves. As the Sm²⁺ concentration in the samples increases, the fluorescence lifetime at 683 nm gradually decreases.

Sm²⁺-doped fluorosilicate luminescent glasses were prepared via adding an appropriate amount of metallic aluminum as a reducing agent in raw materials. The results showed that Sm³⁺ could be fully reduced when Al doping content reached 0.60% (in mass fraction, same hereafter). Furthermore, the influence of heat treatment temperature on Sm²⁺ stability was investigated. The oxidation of Sm²⁺ during heat-treatment could be prevented at Al doping content of 0.60%. In addition, the impact of Sm²⁺ doping content on the luminescence performance was also explored. The fluorescence intensity of the sample reached its maximum value at Sm doping content of 0.5% (in molar fraction).

An issue of electromagnetic pollution has escalated with the proliferation of electronic devices, thus posing a significant threat to human health and electronic equipment. Consequently, there is an increasing interest in materials possessing robust electromagnetic wave absorption capabilities. Based on the absorption mechanisms of electromagnetic wave materials, they can be categorized into dielectric loss and magnetic loss types. The loss mechanisms of magnetic loss materials encompass damping and hysteresis losses. Dielectric loss materials absorb electromagnetic waves through polarization and electrical conductivity losses, typically having elevated dielectric constants. Such materials include ferroelectrics, metal oxides, and inorganic ceramics. Polymer-derived ceramics (PDCs) represent a pivotal technology for the design and fabrication of functional ceramics. This methodology effectively harnesses the advantages of both polymer and ceramic materials. In contrast to conventional ceramic preparation techniques that consume energy, PDCs enable the production of ceramic materials with tunable elemental compositions and controllable crystalline structures through meticulous design and synthesis of the molecular structures of polymer precursors, coupled with precise control in the pyrolysis process. In this paper, polyborosilazanes with different boron contents were synthesized via modulating the quantity of added boron source. The impact of boron content on the structure and properties of polyborosilazanes and the phase composition/microstructure of ceramics was investigated.

20 g of n-hexane was added to a reaction flask in ice bath. Methyl dichlorosilane, vinylmethyl dichlorosilane, boron trichloride, and hexamethyldisilane were sequentially added to the reaction flask at different molar ratios. The mixture was stirred in an argon atmosphere for 24 h. The temperature was then raised to 100 ℃ and maintained for 3 h to remove n-hexane and other by-products. Subsequently, the temperature was further increased to 160 ℃, and maintained for 3 h. The mixture was subjected to three cycles of filtration to obtain a light yellow resin-like polyborosilazane. A series of polyborosilazanes with different boron contents were prepared at different amounts of boron trichloride added. The samples synthesized with boron and nitrogen in a molar ratio of 1∶6, 1.3∶6.0, and 1.5∶6.0 were named as P-BTC-1, P-BTC-1.3, and P-BTC-1.5, with boron contents of 3%, 4%, and 5% (in mass), respectively. The obtained precursor samples were subjected to curing treatment. The curing conditions involved heating in an argon atmosphere at a rate of 2 ℃/min at 280 ℃ for 2 h. Afterwards, the cured samples were heated in an argon atmosphere at a rate of 5 ℃/min at 1000 ℃ for 1 h, and then heated at a rate of 2 ℃/min at 1600 ℃, for 2 h to obtain samples P-BTC-1-1600, P-BTC-1.3-1600, and P-BTC-1.5-1600, respectively.

The chemical bonds and functional groups in the samples were identified by a model Vertex 70 Fourier transform infrared spectrometer (FT-IR, Bruker Co., Germany). ¹H, ¹³C, and ¹¹B were determined by a model Avance NEO 600 nuclear magnetic resonance spectrometer (NMR, Bruker Co., Germany). The phase composition of the ceramic samples was determined by a model X'Pert MPD Pro X-ray diffractometer (XRD, Philips Co., the Netherlands) with Cu K_α radiation source, scanning angles ranging from 10° to 90°. The microstructure of the ceramic samples was analyzed by a model 400 Nano scanning electron microscope (SEM, Nova Co., USA), and the elemental composition analysis of the samples was performed by an energy dispersive spectrometer (EDS, INCA Energy Co., UK). The thermal decomposition process of the polyborosilazane was analyzedby a model STA 449 F3 thermal analyzer (Netzsch Co., Germany). The electromagnetic parameters of the materials were tested by a model E5071C vector network analyzer (Keysight Tech., Co., USA).

A series of polyborosilazanes were synthesized via controlling the amount of boron, resulting in SiBCN ceramics with different atomic compositions. Boron effectively suppresses the fracture of Si—N bonds and the formation of Si—C bonds, inhibits the decomposition of Si₃N₄ and the generation of SiC as well as facilitates the transformation of amorphous carbon into graphite carbon, thereby increasing the proportion of graphite carbon in SiBCN ceramics. The polarization losses generated by various dielectric crystals such as Si₃N₄, SiC and graphite carbon enhance the electromagnetic wave absorption performance of SiBCN ceramics. At a boron content of 5% (in mass), the minimum reflection loss reaches -55.67 dB at 8 GHz for a thickness of 3.5 mm.

1) In the precursor synthesis process, the precursor structure became more stable with an increase in boron content, mainly composed of chemical bonds such as Si—N, B—N, Si—C, Si—H, N—H, and C—H. The ceramic yield increased from 56% to 66.7%.

2) After heat treatment at 1600 ℃, boron in polyborosilazanes suppressed the decomposition of Si₃N₄ and the formation of SiC in SiBCN ceramics, and enabled the control of the conductive phase and dielectric loss phase in SiBCN ceramics, thereby enhancing the impedance matching performance of the ceramics to electromagnetic waves. The polarization losses generated by various dielectric materials such as Si₃N₄, SiC and graphite carbon further enhanced the electromagnetic wave attenuation performance of SiBCN ceramics. At a boron content of 5%, SiBCN ceramics exhibited a minimum reflection loss of -55.67 dB at 8 GHz for a thickness of 3.5 mm, indicating that SiBCN ceramics could be an excellent candidate material in the field of electromagnetic wave absorption.

With the rapid development of industry, the discharge of dye wastewater from the textile and printing industries poses a huge threat to aquatic ecosystems and human health. Exploring efficient catalytic technologies to reduce water pollution is highly anticipated. Photocatalysis, as an efficient and environmentally friendly advanced oxidation technology for decomposing organic dyes, has attracted considerable attention. However, the low utilization rate of solar energy and severe photogenerated carrier recombination restrict the practical application of photocatalysis. In addition to solar energy, the thermal energy generated by cold-hot alternation can be also used as a clean and renewable energy source to induce positive and negative charges and generate pyroelectric potential, thereby achieving pyrocatalysis. Combining pyrocatalysis with photocatalysis can simultaneously collect solar energy and alternating heat energy, and the pyroelectric potential can serve as an internal driving force for dissociating photo generated exciton. This work constructed g-C₃N₄/NaNbO₃ composite materials for the absorption of g-C₃N₄ to visible light to enhance the utilization efficiency of sunlight. The Mott-Schottky curve was obtained by electrochemical workstation to analyze the conduction type and flat band potential of g-C₃N₄ and NaNbO.

A hydrated NaNbO₃ sample was obtained via hydrothermal reaction at 160 ℃ for 4 h with Nb₂O₅ and NaOH as raw materials. The hydrated NaNbO₃ prepared was then mixed, ground with a certain mass of melamine powder (in a mass ratio of 1∶2), and sintered at 500 ℃ for 2 h to obtain g-C₃N₄/NaNbO₃ composite material. The phase, morphology, and optical properties of the product was analyzed by X-ray diffraction (XRD), scanning electron microscopy (SEM), and ultraviolet-visible spectroscopy (UV-Vis). The pyrophotocatalytic performance of g-C₃N₄/NaNbO₃ composite materials was evaluated via degrading mixed dyes (i.e., methylene blue MB, methyl orange MO, rhodamine RhB, and acid orange AO7) under light irradiation and cold-hot cycling. The environmental adaptability of g-C₃N₄/NaNbO₃ composite materials was analyzed by changing the concentration, pH value, and water source of the mixed dye solution. The stability of g-C₃N₄/NaNbO₃ composite material was estimated through five repeated uses and the XRD patterns before and after use. The influence of g-C₃N₄/NaNbO₃ on the degradation performance of the mixed dyes was analyzed via adding different active substance trapping agents, and the main active species in the catalytic reaction was determined. The work function was calculated based on density functional theory (DFT) to analyze the electron transfer after contacting g-C₃N₄ and NaNbO₃.

The g-C₃N₄/NaNbO₃ composite material prepared by a two-step method of hydrothermal and mixed sintering is sheet-like g-C₃N₄ covering the surface of NaNbO₃ nanorods with the diameters of 100-300 nm. The photocatalytic degradation efficiencies of g-C₃N₄, NaNbO₃, and g-C₃N₄/NaNbO₃ composite materials for RhB are 19%, 71%, and 84%, respectively. Combined with the pyroelectric catalysis, the photocatalytic efficiency of g-C₃N₄/NaNbO₃ increases to 97.3%. The results show that the formation of g-C₃N₄ and NaNbO₃ composites can enhance the photocatalytic performance, and the pyroelectric potential generated by temperature fluctuations can further separate the photo-generated electron hole pairs, thus improving the photocatalytic degradation efficiency. Under illumination and cold-hot cycling, g-C₃N₄/NaNbO₃ exhibits a pyrophotocatalytic degradation efficiency of 96.9% for mixed dyes, with a degradation reaction rate of 0.038 6 min^-1. The degradation efficiency of g-C₃N₄/NaNbO₃ decreases with the increase of initial concentrations of mixed dye solution (i.e., 2×10^-5 mol/L, 4×10^-5 mol/L, 6×10^-5 mol/L and 8×10^-5 mol/L). The pyro-photocatalytic degradation efficiency of the mixed dye is 96.9%, 70.8%, and 54.3% when the pH value of the solution is 2.6, 7.1 and 11, respectively, indicating that g-C₃N₄/NaNbO₃ composite catalyst is suitable for working in acidic and neutral environments. Also, g-C₃N₄/NaNbO₃ composite material has a better catalytic activity in deionized water and tap water, while its pyrophotocatalytic performance reduces in river water and lake water. The experimental results of adding sacrificial agents show that ·O₂^-, ·OH, and h⁺ are all active substances in the thermal electric photocatalytic degradation, among which ·O₂⁻ and ·OH play a particularly significant role in the catalytic degradation. The results of UV-Vis spectra, the Mott-Schottky curve and DFT calculations indicate that g-C₃N₄/NaNbO₃ composite material broadens the absorption range of the solar spectrum, forms an S-type heterojunction, and the pyroelectric potential generated by the pyroelectric effect promotes the dissociation of photo generated carriers, thus improving the pyrophotocatalytic performance.

The constructed g-C₃N₄/NaNbO₃ composite material utilized a wide solar spectral absorption range and a photothermal effect of g-C₃N₄. The formation of S-type heterojunction between g-C₃N₄ and NaNbO₃ was conducive to the separation and migration of photo generated carriers. Also, the pyroelectric potential induced by temperature fluctuation could result in band bending, and further promoted the separation of photo generated carriers in NaNbO₃, demonstrating an enhanced pyrophotocatalytic performance. This work could provide an efficient catalyst that simultaneously utilized solar energy and environmental thermal energy to achieve sewage treatment and environmental remediation.

With the rapid development of wireless communication technology, electromagnetic waves are regarded as a main medium for energy and information transmission. Absorbing materials, as a focus of scientific research in recent years, play a key role in effectively reducing electromagnetic radiation pollution in the environment, thereby reducing the negative effect of electromagnetic waves. The design of absorbing materials follows the principles of "thin, light, wide, and strong" to meet practical applications. At present, there are various types of absorbing materials, mainly including magnetic metals, polymer based composite materials, ferrites, and carbon-based materials. However, all the materials have their limitations. For instance, magnetic materials have a superior performance, but they have a poor oxidation resistance, which are prone to eddy current losses, thus affecting the absorption efficiency. The preparation cost of polymer-based composite materials is high, and their application fields are limited. Ferrite materials have an insufficient temperature stability and a high surface density. In addition, carbon-based materials suffer from poor impedance matching and narrow absorption frequency bands. These inherent limitations hinder a widespread applicability of absorbing materials in diverse application scenarios. Therefore, developing novel absorbing materials with superior oxidation resistance and high-temperature stability has an important practical significance.

High-entropy multiphase oxide ceramics was prepared by a solid-state reaction method. In the preparation process, FeO, CoO, NiO, CuO, ZnO and Co₂O₃ as raw materials in a molar ratio of 1∶1∶1∶1∶1∶5 were ground with anhydrous ethanol in a mill at 200 r/min for 8 h, and then dried at 80 ℃ to obtain a mixed powder. Subsequently, 8 g of the mixed powder was pressed into a round billet with a diameter of 30 mm at 10 MPa. The obtained round billet was then heated and reacted in a model BR-12N muffle furnace at different temperatures (i.e., 800, 900, 1000 ℃ and 1100 ℃) for 6 h to obtain the samples of (Fe_0.2Co_0.2Ni_0.2Cu_0.2Zn_0.2)Co_xO_y high-entropy ceramics (HEO), which were named samples HEO-800, HEO-900, HEO-1000, and HEO-1100, respectively.

The results show that the obtained samples HEO-800, HEO-900, HEO-1000, and HEO-1100 all exhibit spinel and rock salt phases, as well as pore structures and irregular blocks. The degree of crystallization gradually increases with increasing temperature, which can be attributed to the accelerated diffusion of atoms at the interface and the gradual increase in grain size due to the presence of oxygen vacancies. The XPS analysis indicates that the high-entropy multiphase oxide ceramics sintered at different temperatures all have oxygen vacancies, and the maximum oxygen vacancies occur at 900 ℃. The conductivity test shows that the sample HEO-900 has the maximum conductivity. The electromagnetic wave absorption test results reveal that the RL_min values of the samples HEO-800, HEO-900, HEO-1000, and HEO-1100 are -9.85, -36.14, -13.73 dB, and -4.61 dB, respectively. The sample HEO-900 obtained via sintering at 900 ℃ has the optimum absorbing property. Except for the sample HEO-900, the reflection loss of other samples is not high mainly due to the weak dielectric loss caused by low oxygen vacancy, while the magnetic loss is opposite to the dielectric loss. The magnetic loss and dielectric loss synergistically promote the improvement of absorption performance of the material. In addition, the impedance matching area also firstly increases and then decreases as the temperature increases. The impedance area of the sample HEO-900 is relatively large, indicating that there are more electromagnetic waves incident on the interior of the material and the absorption efficiency increases.

The results indicated that oxygen vacancies were easily generated in (Fe_0.2Co_0.2Ni_0.2Cu_0.2Zn_0.2)Co_xO_y high-entropy ceramics due to the multivalent state and multiple transformations of element Co, which was conducive to electron transfer. The presence of multiphase structure and oxygen vacancies increased the dielectric loss of the material and the interface polarization and defect polarization of the system, thus significantly improving the absorption capacity of electromagnetic waves. This study found that the sample HEO-900 sintered at 900 ℃ had the optimum absorption performance (i.e., the RL_min value of -36.14 dB and an optimal bandwidth of 2.86 GHz at a matching thickness of 3.0 mm and a frequency of 9.37 GHz).

Steel building is a form of construction. Non-intumescent fireproofing materials have superior fireproofing effects and can provide effective fireproofing and thermal insulation protection for steel structures. However, the modification and innovation of non-intumescent fireproofing materials are insufficient in China at present. Seafoam has a good thermal stability and a low thermal conductivity, having a thermal insulation effect, which can be used as a filler for fireproof coating or fireproof board. Seafoam can effectively improve the fire resistance of fireproof coating or fireproof board. Seafoam mineral fibers dispersed in a low concentration solution can form a stable high-viscosity suspension, so they can be dispersed and modified with other fillers and added to fireproof coating or fireproof board slurry. Therefore, the fire performance of seafoam fiber fireproofing materials can be improved. In this work, a modified seafoam fiber was added to fireproof coatings for improving the fire performance of non-intumescent fireproof coatings. This modified fiber as a kind of modified fiber was prepared via mixing seafoam fiber, magnesium hydroxide fiber and silicon oxide fiber under high-speed mixing and adding polymer modifier. In addition, the physical and chemical properties and fire performance of the finished product were also analyzed.

In this work, 5-70 mm hydromagnesite fibers were ground in a mill to obtain the fibers with the lengths of < 5 mm. Subsequently, 1-5 mm seafoam fibers and 3-6 mm silicon oxide fibers were selected, and 50% seafoam fibers, 30% hydromagnesite fibers, 8% silicon oxide fibers, 5% organic bentonite, 1% polymer water-absorbent resins, 1% starch ether, 5% hydroxypropyl methyl cellulose ether were mixed as raw materials in a dry mixer for 30 min to obtain the modified seafoam fibers. The modified seafoam fibers were analyzed based on the physical phase characterization. Cement, kaolin, modified fiber, and fire protection additives in different weight ratios were added to the dry mixer and stirred for 300 s, and then an expanded vermiculite was added to the mixer and stirred for 120 s, and six groups of fireproofing coating samples were obtained. Afterwards, the samples were then stirred slowly in a cement sand mixer according to a mass ratio of fireproofing coating:707 emulsion: water of 1.0∶0.2∶0.8 and mixed for 5 min to make the mixture homogeneous. After mixing, the fire resistance, bond strength and compressive strength of the samples were characterized.

Based on the fire resistance test analysis of fireproofing materials doped with six different contents of modified seafoam fibers (i.e., 10%, 12.5%, 15%, 17.5%, 20% and 22.5%), the fireproofing and thermal insulation properties of fireproofing coatings are gradually improved with the increase in the addition of modified seafoam fibers. Their fireproofing and thermal insulation properties enhance with the increase in the doping of modified seafoam fibers, indicating that modified seafoam fibers play a key role in the fireproofing coatings. Seafoam fibers play a key role in fireproof coatings. The fireproof performance is obviously better than that of two commercial fireproof materials. The analysis by X-ray diffraction patterns shows that Mg(OH)₂ is added to the modified seafoam fiber. According to the TG-DTG analysis, Mg(OH)₂ decomposes into MgO during the heat process, and MgO is a kind of superior heat-insulating and insulating material, indicating that the modified seafoam fibers greatly improve the fire-insulating and heat-insulating performance. The FTIR analysis shows that there are a large number of Si—O—Si bonds in the sample, and that there is a large number of Si—O—Si bonds in the sample. There are a lot of Si—O—Si bonds in the sample, so that the modified seafoam fibers maintain its original adsorption and rheological properties. The appearance and morphology of the fireproof coating after combustion show that the silicon oxide fibers improve the crack resistance of the fireproof coating.

In this paper, the modified seafoam fiber was prepared via mixing seafoam fiber, magnesite fiber, silicon oxide fiber and some polymer modifiers in a certain proportion. The modified seafoam fiber had a better fireproofing and thermal insulation performance, the magnesite fiber could further reduce the thermal conductivity of the material, and the silicon oxide fiber could ensure that the fireproofing coating was not easy to crack. To meet the national standards of bonding strength and compressive strength of the basis, the fireproof coating with 20% of the modified seafoam fibers had the optimum fire insulation performance. At the effective fire prevention time of 185 min, the coating had a bonding strength of 0.042 MPa and a compressive strength of 0.461 MPa. Compared with some other commercial fireproofing materials, the coating had a fireproofing effect and some application prospects.