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Mullite fiber felt is a promising material that may fulfill the demands of advanced flexible external thermal insulation blankets. However, research on the fabrication and performance of mullite fiber felt with high-temperature resistance and thermal stability is still lacking. In this work, mullite fibers were selected as raw materials for the fabrication of mullite fibrous porous materials with a three-dimensional net structure. Said materials' high-temperature resistance and thermal stability were investigated by assessing the effects of various heat treatment temperatures (1100 °C, 1300 °C, and 1500 °C) on the phase composition, microstructure, and performance of their products. When the heat treatment temperature was below 1300 °C, both the phase compositions and microstructures of products exhibited stability. The compressive rebound rate of the product before and after 1100 °C reached 92.9% and 84.5%, respectively. The backside temperature of the as-prepared products was 361.6 °C when tested at 1500 °C for 4000 s. The as-prepared mullite fibrous porous materials demonstrated excellent high-temperature resistance, thermal stability, thermal insulation performance, and compressive rebound capacity, thereby indicating the great potential of the as-prepared mullite fibrous porous materials in the form of mullite fiber felt within advanced flexible external thermal insulation blankets. [ABSTRACT FROM AUTHOR]

Mullite fiber-based porous ceramics is one of the most commonly used high-temperature insulation materials. However, how to further reduce the thermal conductivity and improve the strength of such materials has been a challenge in the field of high-temperature insulation. In this paper, mullite micro/nano fiber-based porous ceramic was prepared by introducing mullite nanofibers into mullite microfiber-based porous ceramics and the effect of microfiber/nanofiber weight ratio on the samples properties were characterized and analyzed. Results showed that the compressive strength and high-temperature thermal insulation properties of the porous ceramics increased significantly with an increase in the nanofiber content. For the porous ceramics with similar density (about 0.50 g/cm3), the compressive strength of the sample with a microfibers/nanofibers weight ratio of 1:2 was 1.43 MPa, which was much higher than that of the porous ceramics prepared with only microfibers (0.26 MPa). Meanwhile, the backside thermal equilibrium temperature of the sample with a microfiber/nanofiber weight ratio of 1:2 at 900 °C environment was 355.8 °C, which was much lower than that of the porous ceramic prepared with only microfibers (476.5 °C). In addition, in order to investigate the temperature resistance of mullite micro/nano fiber-based porous ceramics, the sintering temperatures was increased from 1400 °C to 1500 °C. Results shows that the high-temperature thermal insulation performance of mullite micro/nano fiber-based porous ceramics with high mullite nanofiber content decays more seriously. The back-temperature test showed that the thermal equilibrium temperature of the samples with a mullite micron/nanofiber weight ratio of 1:1 in 900 °C environment increased rapidly from 386.3 °C to 454.2 °C when the sintering temperature was increased from 1400 °C to 1500 °C. The preparation of mullite micro/nanofiber-based porous ceramics provides a new strategy to improve the performance of fiber-based porous ceramics. [ABSTRACT FROM AUTHOR]

How to improve the strength of fibrous porous ceramics dramatically under the premise of no sacrificing its low density and thermal conductivity has remained a challenge in the high-temperature thermal insulation field. In this paper, a new kind of high-strength mullite fiber-based ceramics composed of interlocked porous mullite fibers was prepared by nanoemulsion electrospinning and dry pressing method. Results show that as to the porous ceramics with the same density (∼ 0.8 g/cm3), the three-dimensional skeleton structure composed of porous mullite fibers was much denser than that composed of solid mullite fibers. Therefore, porous mullite fiber-based ceramics exhibited a higher compressive strength (5.53 MPa) than that of solid mullite fiber-based ceramics (3.21 MPa). In addition, porous mullite fiber-based ceramics exhibited a superior high-temperature heat insulation property because the porous structure in fibers could reduce the radiant heat conduction. This work provides new insight into the development of high-temperature thermal insulators. [ABSTRACT FROM AUTHOR]

Fiber-reinforced aerogel composites are extensively used in thermal insulation and energy-saving fields, while the inherently weak interface combination between fiber and aerogel undermines the effect of fiber reinforcement. To deal with this problem, mullite whiskers were in-situ synthesized on the surface of alumina silicate fiber through a facile and environmentally benign method. The nanoscale mullite whiskers growing on the fiber strengthen the interfacial bonding, thereby improving the mechanical properties of the composite. The alumina silicate fiber/mullite whisker/silica aerogel composites delivered ultrahigh compression stress and modulus of 6.45 MPa and 69.74 MPa at 50% strain, which is 6.14 times and 9.07 times higher than those of bare fiber reinforced silica aerogel. Meanwhile, the composite maintained a high retention rate of maximum stress of 97.8% after being compressed at 30% strain for 200 cycles. Moreover, the composite exhibits an ultralow thermal conductivity of 27.5 mW m−1 K−1 and a low density of 0.26 g cm−3. The strong, resilient, lightweight composite with ultralow thermal conductivity is applicable for heat preservation and energy saving. [Display omitted] • Mullite nanowhiskers were in-situ synthesized on alumina silicate fiber without F catalysts contaminating environment. • The stress (6.45 MPa) and modulus (69.74 MPa) at 50% strain increased dramatically due to interfacial enhancement. • The tough and resilient composite can be compressed at 30% strain for 200 cycles. • The composite also exhibited a low density (0.26 g cm−3) and a low thermal conductivity (27.5 mW m−1 K−1). [ABSTRACT FROM AUTHOR]

• Complex-shaped mullite components were DLP printed based on a hydroxysiloxane/Al 2 O 3 preceramic precursor strategy. • The introduction of hydroxysiloxane can improve the homogeneity and rheological properties of mullite slurry. • The introduction of hydroxysiloxane can reduce the sintering temperature of 3D-mullite precursor. • A sintering aid AlF 3 was employed to promote the sintering reaction between the hydroxysiloxane and the Al 2 O 3 filler. By taking advantage of the low sintering temperatures of the preceramic polymers, stereolithography printed mullite components derived from preceramic polymer precursor containing alumina particles can be sintered at low temperatures. However, due to their high specific surface, nano alumina particles are difficult to be dispersed into the photocurable polysiloxane. Herein, to prepare mullite slurry, a photosensitive hydroxysiloxane was employed as the preceramic polymer matrix while γ-Al 2 O 3 nanoparticle was added as the active filler. The introduction of photocurable hydroxysiloxane not only improved the homogeneity and rheological properties of mullite slurry but also shorted the ionic diffusion distance of Si-ion and Al-ion during the sintering process. Therefore, 3D mullite preceramic precursor stereolithography printed from hydroxysiloxane-Al 2 O 3 slurry was endowed with a low sintering temperature around 1400 °C. During the sintering process of preceramic precursor, sintering aid AlF 3 can participate in the reaction and further promote the formulation of mullite grains. [ABSTRACT FROM AUTHOR]