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Refractory matrix is a key factor in determining the properties and performance and thus the lifetime of refractory materials. The particle gradation affected both the matrix composition and microstructure. In this study, six particle gradations of high‐alumina castables were prepared based on Andreasen's model (q = 0.22, 0.24, 0.26, 0.28, 0.30, and 0.32). The influence of particle gradation on properties of high‐alumina castables bonded with 4.0 wt% reactive MgO (RM) was investigated with respect to the difference in matrix composition and microstructure. The results show that castables with q values of 0.24 and 0.26 exhibited better physical and mechanical properties after curing and drying. The castables with a q value of 0.22 showed the best volume stability after firing at 1600°C, whereas, castables with a q value of 0.24 exhibited the highest mechanical strength, and residual CMOR ratio after thermal shock testing. Based on the property analyses of castables, the optimal q value of RM‐bonded castables would be around 0.24. [ABSTRACT FROM AUTHOR]

To meet the emission standard of nitrogen oxides (NOx) in the flue gas of batch furnaces through dry adsorption, a calcium-silica inorganic adsorbent was prepared with limestone and quartz as raw materials. Sample Cu-BTC 1# was obtained by solvothermal synthesis, drying and purification in vacuum at 120 ℃ using trimesic acid (H3BTC) and copper nitrate trihydrate (Cu(NO3)2·3H2O) as raw materials; likewise, sample Cu-BTC 3# was obtained at 200 ℃. Sample Cu-BTC 2# was obtained by hydrothermal synthesis, drying and purification in air (metal-organic frameworks, 1,3,5-benzene tricarboxylic acid copper). The two types of materials were tested in terms of the NO2 adsorption, and then the specific surface area, pore volume, NO2 adsorption performance, phase composition, microstructure and thermal stability of the adsorbent materials were explored via N2 physical adsorption-desorption, SEM, XRD and TG characterization. The results show that: (1) the Cu-BTC samples have higher adsorption capacity than the calcium-silica adsorbent, in which sample Cu-BTC 3# has the largest specific surface area and pore volume, thus adsorption capacity for NO2; (2) the calcium-silica adsorbent has better thermal stability and lower total mass loss during the entire process than the Cu-BTC samples; sample Cu-BTC 2# has the best thermal stability among the three Cu-BTC samples, and the metal Cu active sites of the Cu-BTC samples can be exposed at least above 150 ℃. [ABSTRACT FROM AUTHOR]

In order to improve the performance of magnesia dolomite materials, magnesium dolomite refractory materials whose iron oxide content (mass fraction) of 0, 0.5%, 1.0%, 1.5%, respectively, were prepared from natural dolomite, high silicon magnesite, silica and iron oxide powder by two-stage calcination and slaking process. The influence of iron oxide content on the physical properties, hydration resistance and coatability adherence of the samples was investigated. The phase composition and microstructure of the specimens were characterized. The results showed that, as the iron oxide content increased, the room temperature flexural strength and the room temperature compressive strength increased, the high temperature flexural strength and the adherence strength decreased, and the retention rate of the thermal shock strength of the sample first increased and then decreased. With the iron oxide content increasing to 1.5%, the hydration weight gain rate of the sample decreased to 0. 12%, and the hydration resistance improved. According to the XRD spectrum analysis, the main crystal phases of the sample were periclase, dicalcium silicate and tricalcium silicate. With the increase of iron oxide content, the diffraction peaks of C2S and C3S became stronger and the peak shapes were sharp. It showed that iron oxide could promote the growth of C2S and C3S crystals and increase the density of the sample. [ABSTRACT FROM AUTHOR]

In view of the development demand of biomaterials for bone substitute, the development status of polymer materials, metal materials, bioceramic materials and composite materials for bone replacement were summarized. The advantages of bioceramic materials in mechanical properties, chemical properties and biological properties as bone substitute materials were emphatically introduced. The bioceramic materials play an important role in the field of bone substitute materials due to their similar density and composition to human bone, significant bio-compatibility, high mechanical strength, and stable chemical properties. In this study, the research status of bioceramic materials represented by phosphate, silicate, oxides and non-oxides was systematically discussed, and the advantages and limitations of bioceramic materials and their composites as bone substitute biomaterials study were discussed. Finally, the future development direction of bioceramic materials was prospected. [ABSTRACT FROM AUTHOR]

Ti3C2Tx MXene-based composites are attractive for use as electromagnetic wave absorption (EMA) materials due to their high conductivity and abundant dipoles on the surface. Nevertheless, the controlled synthesis of MXene foams with tailored dielectric properties for high-performance microwave absorption is still a challenge. Herein, the porous structure of MXene foams has been realized through a freeze–thaw assembly strategy in the presence of reduced graphene oxide (rGO). By adjusting the amounts of magnetic units of NiO particles, the complex permittivity and permeability of MXene/rGO can be tuned. The developed uniform cellular structure enables multiple reflections and scattering of electromagnetic waves among the microcellular network while the cooperation of NiO particles generated through calcination contributes to dielectric loss and magnetic loss. The obtained Ti3C2Tx/rGO/NiO composites achieve a minimal reflection loss of −62.98 dB at 7.5 GHz. This work provides a promising strategy for designing light weight and multifunctional MXene foam-based microwave absorbers. [ABSTRACT FROM AUTHOR]

To improve the sintering performance of silicon nitride bioceramics, we explored the effect of β-SiAlON's Z-value on the physical, chemical, and biological properties of β-SiAlON–Si3N4 composites. Results showed that the phase product was β-Si3N4. As the Z-value increased, the X-ray diffraction peaks gradually shifted to a smaller angle, the material grains were more tightly packed, and the bulk density and compressive strength increased, reaching the highest values (2.71 g/cm3 and 1157 MPa, respectively) at Z = 4. Soaking and ion-release experiments show that in an aqueous environment, a small amount of Al and Si ions were released, and no obvious decomposition occurred on the surface of the material. The biological performance showed that the growth of cultured cells in each group was in good condition, there was no obvious difference in morphology and adhesion, and the materials had good biological performance. An increase in the Z-value promotes the formation of mineralized nodules and osteogenic differentiation of MC3T3-E1 cells, which may be because the release of Si can promote osteogenic differentiation. Therefore, the addition of β-SiAlON could improve the sintering performance of β-Si3N4 without degrading its biological properties. The prepared β-SiAlON–Si3N4 composite ceramic is a latent bioceramic material. [ABSTRACT FROM AUTHOR]

To investigate the effects of CaO on the physicochemical and biological properties of β‐SiAlON, β‐SiAlON ceramics containing CaO were prepared using the direct nitriding method. The results of X‐ray powder diffraction and scanning electron microscopy demonstrated that β‐SiAlON remained in the material phase because the addition of Ca did not result in the formation of Ca‐α‐SiAlON. However, CaO promoted the sintering of β‐SiAlON grains and significantly decreased porosity and increased bulk density and compressive strength. According to a chemical stability study, when β‐SiAlON ceramics powder was soaked in deionized water and a cell culture medium, it was noted to have negative electricity. A reaction occurred with the H+ and OH− ions in the deionized water, leading to the formation of surface structures, such as Si‐OH, Al‐OH, and N‐H. Moreover, the addition of CaO caused a different chemical reaction among ions or ion groups in the culture medium, and new chemical groups formed on the material surface that interacted with the culture medium, which resulted in an alteration of the zeta potential and surface chemical properties of β‐SiAlON. MC3T3‐E1 cells cultured on the surface of ceramics proved that the cells cannot adhere well to the surface of β‐SiAlON ceramics with CaO, although they could proliferate well around those with only β‐SiAlON. Therefore, the change in the surface chemical properties provides good anticell adhesion ability, which makes β‐SiAlON with CaO a biocompatible material that can be used to prevent contamination caused by cell adhesion, with possible applications in biosensors or biomedical equipment that must be used in sterile environments. [ABSTRACT FROM AUTHOR]

Layered materials are promising candidates to serve for thermal insulation coatings because of their low out‐of‐plane thermal conductivity. The thin film preparation of the layered materials in layer‐by‐layer fashion can be realized by several solution processes. However, the layered materials suffer low thermal stability after the solution processes. Herein, we report a strategy to improve the thermal stability of the layered materials processed in solution. In this work, we studied the thermal stability of the lepidocrocite‐type titanate with various interlayer ions (Li+, Na+, K+, and Cs+) at elevated temperatures. We proved that the thermal stability of the titanate increased with the increase of the ionic radius. The Cs+ intercalated titanate can remain in its layered structure up to 1000°C, while the Li+ interacted titanate loses its structural stability at ~280°C. Our work suggests that increasing the size of the interlayer ions is an effective strategy to enhance the structural stability of layered titanates. [ABSTRACT FROM AUTHOR]