When the groundwater contains a high concentration of carbonate and chloride ions, the corrosion of carbonic acid solution on underground concrete structures will lead to a faster migration of chloride ions in concrete. Migration characteristic of chloride ions in mortar exists in carbonic acid solution environment. The corrosion products and microstructure of paste under the attack of carbonic acid solution and chloride ions were analyzed by X-ray diffraction (XRD), thermogravimetric analysis (TG-DTG) and scanning electron microscopy-energy dispersive spectroscopy (SEM-EDS). The results show that in the early stage of carbonic acid water corrosion, calcium hydroxide and C-S-H gel decalcifies to form calcium carbonate filling the pore structure of the mortar, and inhibits the migration of chloride ions in the mortar. At the later stage of corrosion, the dissolution of calcium carbonate and the conversion of C-S-H gel with a low calcium-silicon ratio into amorphous silica gel lead to the increase of mortar porosity and the acceleration of chloride ion migration in mortar. Carbonic acid water corrosion results in the decomposition of Friedel's salts and the decrease of the adsorption capacity of C-S-H gel for chloride ions. Reducing water-cement ratio can increase the corrosion resistance of mortar to carbonic acid water and reduce the migration rate of chloride ions.

Printed circuit boards (PCBs) are usually required to be integrated and miniaturized by a variety of applications, such as 5G microstrip antenna and millimeter wave radar, which require the used dielectric substrate materials with a low dielectric loss (D_f) and a high dielectric constant (D_k). The composite substrate prepared by filling dielectric ceramics into organic polymers has good machinability and superior dielectric properties, which is regarded as the most promising solution. However, the physical and chemical indexes, dielectric properties of the ceramic filler and its compatibility with organic resins are three key factors affecting the comprehensive properties of organic/inorganic composites. In this paper, a micron-spherical filler with a high sphericity and a high crystallinity was prepared by a special spheroidization technology with titanium dioxide material with superior dielectric properties (i.e., D_k ≈110, D_f ≈ 0.001, dielectric constant temperature coefficient (α) ≈ -700×10^-6 ℃^-1). The compatibility between the filler and organic resin is improved after the surface modification of TiO₂ filler. Also, the dielectric constant temperature coefficient of TiO₂ filler is regulated by Al₂O₃ doping. The composite substrate filling with 20% (in mass) Al₂O₃ exhibits the superior properties (i.e., D_k=10.2, D_f=0.001 9, and α= -405×10^-6 ℃^-1). This indicates that the as-prepared ceramic filler has the promising characteristics for potential applications of 5G high-frequency, high-dielectric PCBs.

Novel high-temperature thermal barrier materials become the key materials for the development of new generation aeroengines. In this paper, a monoclinic high-entropy rare-earth tantalate material (Y_0.2Gd_0.2Dy_0.2Ce_0.2La_0.2)TaO₄[(5RE_0.2)TaO₄] was synthesized via solid-state reaction. The thermal, the mechanical and the molten silicate environmental deposits (CMAS) corrosion resistance were investigated. The results indicate that (5RE_0.2)TaO₄ exhibits a low thermal conductivity (i.e., 1.22 W·m^-1·K^-1, 600 ℃) and a high thermal expansion coefficient (i.e., 10.3×10^-6 K^-1, 1 200 ℃), Compared with YSZ material (i.e., 2.1-2.7 W·m^-1·K^-1, 100-900 ℃), the thermal conductivity is decreased by 42%. The fracture toughness reaches 2.8 MPa·m^1/2, which is superior to most thermal barrier coating materials because of its unique ferroelastic toughening effect. The thickness and penetration depth of the (5RE_0.2)TaO₄ reaction layer are smaller than those of the YSZ material after being corroded by CMAS at 1 350 ℃ for different durations. This material is a developed thermal barrier coating material with a great application potential.

The Al₂O₃-ZrO₂-Cr₂O₃-SiO₂ (AZCS) material as a new type of fused-cast refractory has better corrosion resistance than other fused refractories under high-temperature and high-corrosion resistance conditions. To investigate the erosion resistance behavior of the material to the borosilicate glass melt, the AZCS material was subjected to an erosion test at 1 500 ℃, by using borosilicate glass waste-forms containing B₂O₃ of 12% (in mass fraction). The samples before and after erosion were analyzed by chemical analysis, X-ray diffraction, scanning electron microscopy and energy disperse spectroscopy. The results show that AZCS material can be divided into the metamorphic layer, transitional layer and central layer based on the degree of corrosion. The central layer changes little, there are still a large amount of aluminum-chromium solid solution and baddeleyite, and only a small amount of newly formed magnesia-alumina spinel. MgO infiltrating the material reacts with the solid solution to form the MA spinel in situ and partially replaces the aluminum-chromium solid solution in the original position. In the transitional layer, the maximum amount of MA spinel is formed, and the Al-Cr solid solution dissolves and disappears. Therefore, the phases in this layer are MA spinel and baddeleyite. In the metamorphic layer, there is basically only undissolved Cr₂O₃ phase with a loose Cr₂O₃ structure and a worm-like morphology. Aluminum-chromium solid solution, baddeleyite and MA spinel dissolve and disappear.

Al-pillared montmorillonite/carbon nanocomposites were prepared by a hydrothermal method using Al-pillared montmorillonite as a template and chitosan as a carbon source, and then hot-pressed to obtain Al-pillared montmorillonite-based ceramic/carbon composites. The effect of carbon content on the densities, mechanics, electrical conductivity and wave absorption properties of the composites was investigated by X-ray diffraction, scanning electron microscopy, universal material tests and vector network analysis. The results show that the Al-pillared montmorillonite/carbon is transformed into mullite/carbon ceramic material by hot-press sintering, and the carbon is further graphitized in the hot pressing. The introduction of carbon enhances the electrical conductivity and toughness of the composites, while a large amount of interfacial polarization is formed inside the material, which enhances the dielectric loss of the composites and transforms the ceramic material from a wave-transparent body to an electromagnetic wave absorbing material. The internal microcracks of the composites increase and the flexural strength gradually decreases with the further increase of carbon mass fraction in aluminum column-supported montmorillonite. The fracture toughness of the composite material is the maximum value when the mass ratio of montmorillonite to chitosan is 32 at 1 300 ℃, 20 MPa and 120 min of holding time, which is 11.41% greater than that of ceramics without carbon addition. The maximum electrical conductivity of the composite material is 17.53 S·m^-1 when the mass ratio of montmorillonite to chitosan is 4. According to the simulation calculations through wave absorption performance tests, the minimum R_L value of the obtained material reaches -44.93 dB when the coating thickness is 1.4 mm. The minimum R_L value is -36.28 dB and the effective absorption bandwidth is 5.0 GHz when the coating thickness is 1.6 mm.

The emission of electromagnetic wave is a fundamental property of any substance at a temperature higher than 0 K. However, the capability of thermal radiation is not an immutable property of materials, and the static and dynamic modulations of thermal emission are realized by different methods in recent years. This review represented the general principles of thermal emission, and recent work on the static and dynamic modulation of infrared thermal emission by using nanophotonic structures. Besides, the emerging applications of spectrally modulated selective infrared emitters in fields such as energy were highlighted. In addition, this review also summarizedthe current problems and outlined the potential future direction in the modulation of infrared emission of inorganic materials.

Achieving a biocompatible joint between titanium alloy and ZrO₂ ceramic is of great significance to extend its application in the biomedical field. In this paper, the joining between Ti-13Nb-13Zr alloy and ZrO₂ ceramics was achieved with Sn-Zr filler metal. The interfacial microstructure and reaction products of TNZ/ZrO₂ joints were analyzed by X-ray diffraction, scanning electron microscopy and energy disperse spectroscopy, and the shear test was carried out to evaluate the mechanical properties of joints. The effect of Zr content on the interfacial microstructure and mechanical properties of the joints was also investigated. The results show that the typical microstructure of the joints brazed at 600 ℃ for 30 min with Sn-6Zr (atomic fraction) filler metal is TNZ/Ti₆Sn₅/β-Sn+Zr(s,s)+ ZrSn₂/m-ZrO₂/ZrO₂. Among all of the reaction phases, the formation of m-ZrO₂ facilitates the metallurgical bonding between ZrO₂ substrate and brazing seam. The amounts of both Zr solid solution and ZrSn₂ phase increase, but the proportion of β-Sn in the brazing seam gradually decreases with the increase of Zr content. The maximum average shear strength of brazing joints reaches 25.6 MPa when the Zr content is 6%. According to the analysis of fracture path, the joints brazed with Sn-6Zr mainly fracture along the β-Sn in the brazing seam.

(Ni, Sb)-codoped rutile yellow (NiSb-RTi) pigment with a high near-infrared (Near infrared, NIR) reflectance was prepared by a solid-phase method, and then (Ni, Sb)-codoped rutile/silica aerogel (NiSb-RTi/silica aerogel) hybrid pigment with a high NIR reflectance and a network structure was prepared with SiO₂ aerogel substrate. The structural characteristics, color rendering performance, NIR reflectance, and thermal insulation performance of the hybrid pigment were characterized. The results show that NiSb-RTi pigment synthesized at 1% (in mass fraction) NaF as a sintering aid has superior color rendering performance (b*=54.24) and NIR reflectance. NiSb-RTi/silica aerogel hybrid pigment with a network structure has a good color rendering performance, a low transmittance, a high NIR reflectance (i.e., 96.60%) and a low thermal conductivity (i.e., 0.068 54 W/(m·K)), indicating a superior thermal insulation performance. In addition, the preparation process and thermal insulation mechanism of the hybrid pigment with a network structure were also discussed.

Microwave absorbing materials refer to a class of materials that can absorb or weaken the electromagnetic wave energy on their surface, thereby reducing electromagnetic interference. In recent years, various high-entropy ceramic absorbing materials have emerged in the exploration of absorbing materials. These materials exhibit a better absorbing performance than single-component materials due to their thermodynamic high-entropy effect, lattice distortion effect in structure, hysteresis diffusion effect in kinetics, and synergistic enhancement effect of components. This review summarized recent research results on the component design, preparation, and absorbing performance relationship of different types of high-entropy absorbing ceramics, and analyzed the influence of high-entropy effect on its absorbing performance. In addition, this review also summarized the corresponding scientific issues and challenges in research work and prospected the future development directions of high-entropy absorbing ceramics.

The blue and cyan amorphous photonic color glazes were prepared with the addition of 2%-7% niobium pentoxide to Na₂O-K₂O-MgO-CaO-Al₂O₃-SiO₂ ceramic glaze. The effect of Nb₂O₅ addition on the glaze color, phase-separated structure and elemental distribution was investigated by UV-Vis reflection spectroscopy, Fourier transform infrared spectroscopy, scanning electron microscope, transmission electron microscope, and the regulation mechanism on the structural color of amorphous photonic was analyzed. The results indicate that the [NbO₄] tetrahedra transforms into [NbO₆] octahedra as the content of Nb₂O₅ increases, which exists as network oxides, causing a decreased viscosity of the glaze melt at high temperatures and an increased size of the phase-separated droplets. Also, a large enrichment of Nb₂O₅ improves the refractive index difference between the two phases, leading to the wavelength of amorphous photonic structural coloration moving to the long-wave direction and a transition of the glaze color from blue to cyan.