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Recently, high-performance ceramic aerogels (CAs) have become a research hotspot because of their multi-functional properties. Compared to their oxide counterparts, non-oxide CAs show better thermal shock resistance and other high-temperature properties, making them suitable for applications in harsh environments. In this work, Si 3 N 4 -BC x N-TiN ceramic aerogels (SBCNT CAs) with molar ratios of B/C/Si/Ti = 2:1:5:5 were synthesized at 1623 K for 3 h via foam-gelcasting, from Si, Ti, melamine and boron acid raw materials. The prepared SBCNT CAs containing 91.0% porosity exhibited the highest compressive strength up to 1.0 MPa, and thermal conductivity of 0.144 W/(m·K) at 298 K. They also exhibited excellent service performance at 1473 K in Ar, demonstrating their great potential for high-temperature applications. [Display omitted] [ABSTRACT FROM AUTHOR]

High strength SiC reinforced Si 3 N 4 ceramics aerogels (SCSNCAs) were fabricated via foam-gelcasting and subsequent catalytic reaction, utilizing industrial Si and melamine as raw materials, a small amount of incidental Fe impurities in Si powder as the catalyst and cetyltrimethylammonium bromide (CTAB, the amount of 0.075 wt%) as foaming agent. The effects of solid loading level and reaction temperature on phase composition, microstructure and mechanical properties of the as-prepared SCSNCAs were examined. The aerogels prepared at 1423 K using a slurry of solid loading level of 30 wt% (Si:melamine = 3:1, mass ratio) had porosity of 91.9%, having compressive and specific strength of 0.8 MPa and 3.8 MPa·cm3·g−1 exhibited the lowest thermal conductivity of 0.066 W/(m·K) at 473 K. Compared with the control sample (without melamine, i.e., Si 3 N 4 aerogels without the formation of SiC), the specific strength of the SCSNCAs increased by about 10%, which was attributed to the additional reinforcement from SiC whiskers formed in the Si 3 N 4 matrix of the aerogels. [ABSTRACT FROM AUTHOR]

Multifunctional aerogels with high porosity and good thermal insulation have attracted much attention in the field of energy and aerospace engineering. In this work, a three-dimensional BN fiber aerogel with hierarchically porous structure was prepared through a freeze-drying combined with in-situ carbothermal reduction nitridation route. The synthesized BN fiber aerogel exhibits a specific surface area of 154.3 m2/g, a high porosity of 96.8% and hydrophobicity. Moreover, the BN fiber aerogel shows a low thermal conductivity of 0.051 W/(m·K) and excellent thermal insulation properties owing to its hierarchical porous structure. Particularly, the BN fiber aerogel still maintains its low thermal conductivity and a rather high mechanical strength after re-heated at 1473 K for 3 h in Ar atmosphere, suggesting excellent high-temperature service performance. The successfully developed multifunctional BN fiber aerogel holds promising potential in high-temperature thermal insulation fields. [ABSTRACT FROM AUTHOR]

With the rapid development of energy sources and aerospace engineering, high-performance thermal insulation materials with multiple functions are attracting more and more attentions. Non-oxide ceramic aerogels have application potential in thermal insulation under harsh conditions owing to their good thermal insulation performance and chemical stability. In this work, TiN aerogels were prepared by a combined freeze-casting and carbothermal reduction-nitridation method utilizing TiO 2 and chitosan as raw materials, at 1473 K for 3 h, with a C/TiO 2 molar ratio of 3/1. They showed a specific surface area of 167 m2/g and ultralow density of 0.07 g/cm3 (the relative density of 1.3 %). Their thermal conductivity value was only 0.166 ± 0.0054 W/(m K at 673 K (TiO 2 solid content of 5 wt%). Moreover, the prepared aerogels possessed reasonably high mechanical strength and good high-temperature service performance, suggesting that they can be used under high-temperature conditions as an insulation material. [ABSTRACT FROM AUTHOR]

[Display omitted] • GNP/BNA were prepared by a one-pot foam-gelcasting/nitridation route for CIP removal. • GNP/BNA exhibited a high efficiency and good recyclability in CIP removal, even used at a low dose of 250 mg/L. • BN and GNP showed selective adsorptions of functional groups in CIP. • Synergistic adsorption effects on functional groups improve the adsorption property. Pharmaceuticals are emerging contaminants causing a lot of concerns and posing a threat to the aquatic environment and human health. In this study, graphene nanoplatelet/Boron Nitride composite aerogels (GNP/BNA) comprising BN ribbon fibers and multilayered graphene were prepared at a relatively low temperature of 1423 K for 3 h via a one-pot foam-gelcasting/nitridation route, and tested as an adsorbent for the removal of pharmaceutical ciprofloxacin (CIP) from its aqueous solutions. The density, porosity and compressive strength of the as-prepared GNP/BNA were respectively 28–34 mg/cm3, ~99% and 40–52 kPa. They exhibited a rapid adsorption rate and effective removal performance (99%) for CIP under the experimental conditions of C 0 = 10.5 mg/L, pH = 7 and 295 ± 3 K, even at a low adsorbent dose of 250 mg/L. The maximum adsorption capacity and normalized adsorption capacity of the composite foam were respectively 185 mg/g and 2.03 mg/m2 at the CIP concentration of 10.5 mg/L. Based on the density functional theory calculations, the adsorption mechanism was clarified. BN and GNP exhibited evident selective adsorption for the functional groups of CIP. The COO (C O, the carbonyl group in the carboxyl group) and CO were adsorbed stably on the BN nanosheets and GNP, respectively. The combined interactions of BN and GNP with the functional groups of CIP were responsible mainly for the excellent adsorption performance of the prepared composite foam. The as-prepared GNP/BNA composites with robust strength, good recyclability and high efficiency in the CIP removal, could be a promising candidate for efficient removal of a range of similar emerging contaminants. [ABSTRACT FROM AUTHOR]