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Mullite fibrous porous ceramics is one of the most commonly used high temperature insulation materials. However, how to improve the strength of the mullite fibrous porous ceramics dramatically under the premise of no sacrificing the low sample density has always been a difficult scientific problem. In this study, the strategy of using mullite nanofibers to replace the mullite micron-fibers was proposed to fabricate the mullite nanofibrous porous ceramics by the gel-casting method. Results show that mullite nanofibrous porous ceramics present a much higher compressive strength (0.837 MPa) than that of mullite micron-fibrous porous ceramics (0.515 MPa) even when the density of the mullite nanofibrous porous ceramics (0.202 g/cm3) is only around three quarters of that of the mullite micron-fibrous porous ceramics (0.266 g/cm3). The obtained materials that present the best combination of mechanical and thermal properties can be regarded as potential high-temperature thermal insulators in various thermal protection systems. [ABSTRACT FROM AUTHOR]

The feature of "curing at low temperature, directly used in extreme conditions" made the adhesion technique more suitable for engineering application. The superalloy was successfully bonded at high temperatures by a multi-components modified, phenix-silicone-based adhesive, through forming various ceramics and intermetallics. The intermetallization process not only modified the thermal expansibility of adhesive, but also improved the compositional continuity and reaction extent around bonding interface. With the heating temperature increasing from 500 °C to 1000 °C, various high-temperature-resistant phases in turn generated in adhesive, and the chemical reactions on interfaces became more and more intense. Eventually, the room temperature shear strength of joints calcined at 700 °C reached the maximum value of 28.3 MPa, and the high temperature strength was still up to 18.4 MPa at 800 °C. Moreover, after 6 thermal cycles, the residual strength for joints calcined at 700 °C almost remained ∼13 MPa. The exclusive adhesive absolutely facilitated the repair and connection of engineering superalloy. Image 1 • The convenient use is "one-time connection at room-temperature, valid to 1000 °C without post-processing". • The CTE of adhesive is matched well with superalloys. • The reaction transition layer greatly guaranteed the bonding performance. [ABSTRACT FROM AUTHOR]

Abstract Here, we developed silica/mullite fiber composite membranes with double-layer structure by a simple vacuum procedure for the removal of sub-micrometer dust. The support with three-dimensional skeleton structure exhibited high porosity (higher than 90%), low density (lower than 0.25 g/cm3) and high compressive strength (higher than 0.55 MPa) at 1000 °C. By controlling the mass ratio of silica sol to mullite fiber, we can obtain uniform and complete filtering layers with different thicknesses. The composite membranes exhibited high PM filtration efficiency with 99% for 1–10 µm, 97% for 0.5 µm and 90% for 0.3 µm. These samples had high air flow with very low pressure drop (lower than 600 Pa when airflow velocity reached 1 m/s). These results indicated that the silica/mullite fiber composite membranes were very promising for PM pollution control in the field of hot gas filtration. [ABSTRACT FROM AUTHOR]

Highlights • Mullite-based nanofibrous aerogels were firstly fabricated. • The aerogels show a unique multilevel pore structure. • The aerogels exhibit an ultralow density and ultralow thermal conductivity. • The aerogels show an excellent high-temperature thermal stability. Abstract The fabrication of insulation materials with ultralow thermal conductivity and excellent thermal stability at high temperatures (higher than 1200 °C) has remained an extremely challenging. In this study, we reported the manufacturing of mullite-based nanofibrous aerogels via the gel-casting and freeze drying methods using the electrospun nanofibers with different alumina/silica molar ratios (3:2, 3:1 and 3:0) as the matrix and silica sols as the high temperature binders. The formation process of the mullite-based fibrous aerogel and effect of aerogel composition on the sample physical and mechanical properties were investigated. All mullite-based nanofibrous aerogel show a similar multilevel pore structure. The minor pores were formed by the overlaps of nanofibers and were the fundamental porous structure of the aerogel, while the major pores was caused by the sublimation of the ice crystal. This unique multilevel pore structure make the mullite-based nanofibrous aerogels exhibit an ultralow density (34.64–48.89 mg/cm3) and low thermal conductivity (0.03274–0.04317 Wm−1 K−1) although the sintering temperature was as high as 1400 °C much higher than the service temperature of the traditional nanoparticle aerogel. In addition, besides controlling the fabrication parameters, the physical and mechanical properties could be also tuned by adjusting the composition of the nanofibers. The research of this work provides a new insight into the development of high efficient thermal insulation materials used at high temperatures. [ABSTRACT FROM AUTHOR]

Abstract A modified superalloy-used heat-resistant adhesive, which can cure at room temperature and provide excellent bonding effect in a wide temperature range from RT to 1000 °C, was prepared from silicone resin as matrix, and Ni, Al, B 4 C, low-temperature-melting glass powder as additives. After pre-calcination, the bonding strength of adhesive reached 30.1 MPa after 700°C-calcination and maintained above 15.7 MPa during the whole heating process as the mixture of Ni-based intermetallics, heat-resistant ceramic generated and high viscosity glass generated in the adhesive. Without pre-calcination, the bonding strength still kept above 10.5 MPa during test from RT to 900 °C and decreased to 4.3 MPa at 1000 °C. Graphical abstract Image 1 Highlights • This adhesive provides excellent bonding strength from room temperature to 1000 °C for superalloys joining. • The bonding effect of adhesive at high temperatures is estimated by high-temperature shear test. • The practical use is "one-time joining at room temperature, valid to 1000 °C without post-processing". • This adhesive can be used not only for the manufacture of superalloy components but also for the repair of broken parts. [ABSTRACT FROM AUTHOR]

Abstract In this study, alumina hollow sphere-based ceramics were successfully prepared using the dimethyl silicone rubber, a kind of preceramic polymer, as the forming binder. A mixture of inorganic fillers, including SnO-SiO 2 -P 2 O 5 (SSP) glass powder, boron carbide (B 4 C) powder, silicon (Si) powder and aluminum (Al) powder, were introduced into the silicone rubber to compensate for the weight loss caused by the ceramization of the silicone rubber. The green body exhibited an excellent flexibility and machinability due to the formation of the Si-O-Si polymeric network in the green sample. During the sintering process, the silicone rubber decomposed and transformed into the amorphous silica, occurring a large weight loss, while the oxidization reaction of the introduced inorganic fillers (B 4 C, Al and Si powders) could effectively compensate for this large weight loss to some content. The addition of SSP and B 4 C powders could decrease the melting point of the binder, and therefore improve the strength of the sample sintered at low temperatures (lower than 1300 °C); the addition of Si and Al powders could promote the formation of mullite phased, consequently introducing a high bonding strength between the alumina spheres. The sample with the addition of the mixed inorganic filler after sintered at 1500 °C exhibited a low density of 1.18 g/cm3, low thermal conductive of 0.83 W/mK and high compressive strength of 23.32 MPa and could be used as the high temperature thermal insulation materials in various thermal protection systems. [ABSTRACT FROM AUTHOR]

Abstract High-emissivity MoSi 2 -SiC-Al 2 O 3 -SiO 2 coating with MoSi 2 and SiC as emittance agents, Al 2 O 3 as base skeleton, and silica sol as both dispersive medium of the coating slurry and binder of the coating, was prepared on mullite fibrous insulations via slurry coating and non-firing process. The non-firing coatings were calcined at high temperatures to reveal their reusability after high temperature service. Microstructure, phase composition, interface bonding strength and impact resistance of the non-firing coating and the calcined coatings were investigated comprehensively. Thermal shock resistance, thermal endurance and infrared radiation property of the coatings were studied. The results show that the non-firing coating was dense and flat with all particles bonded together by silica sol; no clear interface existed between the coating and the substrate due to the penetration of the coating slurry; the whole coating was composed of a porous inner layer of about 300 µm in thickness and a top layer of about 100 µm in thickness. The calcined coatings exhibited ideal microstructure with newly formed high temperature phases. Both interface bonding strength and impact resistance of the calcined coatings increased with elevated calcination temperatures, benefited from the good binding effect of silica sol, the gradient structure and the formation of mullite. The coatings remained intact without peeling and spalling after thermal shock tests, and the main defects in the coating surface after thermal shock tests at 1400 °C and 1500 °C were cracks and holes, respectively. The coatings exhibited better long-term thermal endurance at 1400 °C than at 1500 °C, resulted from the weaker oxidation of emittance agents at lower temperature. The emissivity of the non-firing coating at the wavelength range of 3–5 µm and 8–12 µm was as high as 0.9, benefited from the non-firing process, and the emissivity of the calcined coatings were higher than 0.8. [ABSTRACT FROM AUTHOR]

Abstract Silica sol, one of the most commonly used binders in the fabrication of fibrous porous ceramics, can diffuse as the solvent evaporates during the drying stage, leading to an uneven structure of ceramics. To prevent the diffusion of silica particles and prepare homogeneous mullite fibrous porous ceramics, propylene oxide (PO) was introduced into the fabricating procedures. The effects of solid content of silica sol and the molar ratio of PO /silica phase (PO/SiO 2) on the microstructure and physical properties of mullite fibrous porous ceramics were also investigated. The results demonstrated that PO addition strongly consolidated the mullite fibrous skeleton and helped to obtain a homogenous property, because silica phase had been consolidated in situ around the fibers during the gelation stage. Furthermore, the mullite fibrous ceramics prepared with PO addition showed an even microstructure and a much better compressive strength (1.489 MPa), compared with the ones prepared without PO addition (0.868 MPa). Finally, the solid content of silica sol showed a very strong relevance to the properties of the ceramics: the compressive strength raised from 0.731 MPa to 1.715 MPa with the solid content of silica sols increasing from 9 wt% to 18 wt%; while the molar ratio of PO/SiO 2 had little: the compressive strength was around 1.480 MPa, with the corresponding molar ratios of PO/SiO 2 ranging from 0.43 to 1.72. [ABSTRACT FROM AUTHOR]

Abstract Here we report a novel aerogel material assembled by the electrospun SiOC fibers with a hierarchical pore structure. The fibrous aerogels were successfully fabricated by the gel-casting and freeze-drying method using the SiOC fibers as the matrix and the silica sols as the binders. The effect of the SiOC fiber content and the silica sol content on the properties of the samples were investigated. The SiOC fibrous aerogels after calcined at 1000 °C exhibited low densities of 46.87–128.48 mg/cm3, low thermal conductivities of 0.0302–0.0440 W/m K, high compressive strengths of 18–167 kPa and relatively high specific surface areas of 12.48–34.87 m2/g. Such unique fibrous aerogel materials are foreseen as the promising high-temperature insulators, absorbents and supports. [ABSTRACT FROM AUTHOR]

Fly ash cenosphere/mullite (FACs/M) composites with excellent high-temperature resistance were prepared through a tert-butyl alcohol gelcasting process, using the mullite and FACs as the matrix and the filler, respectively, and the matrix of mullite was derived from phase transformation of the raw material of kaolin. Results show that the FACs/M exhibited low density and high specific compressive strength and the thermal conductivity was distributed over in the range of values predicted from Maxwell-Eucken model 2 and Effective Medium Theory (EMT) equation. Exponent m describing the relationship between compressive strength and porosity was 2.37. Young’s moduli of the composites were lower than that predicted from the Hashin-Shtrikman model. The high-temperature testing results revealed that the FACs/M composite exhibited high compressive strength and the 50% FACs/M composite displayed compressive strength of 14.11 MPa after testing at 800 °C. The FACs/M composites with excellent mechanical properties both at room and high temperatures may possibly be used in the deep sea and other fields in the near future. [ABSTRACT FROM AUTHOR]

High emissivity coatings on fibrous insulation tiles played an important role in thermal protection systems and thereby intrigued many researchers; however, there was little emphasis on the mechanical properties of the coatings. In this study, a gradient MoSi 2 -borosilicate glass coating with a dense surface layer and a porous interlayer was designed for mullite fibrous ceramics. Mechanical properties and structure parameters of the coating layers and the substrate were studied. The gradient coating was compared with a monolayer dense coating of the same composition and same surface density in contact damage resistance, impact resistance and emissivity. Compared with monolayer dense coating coated substrates, the gradient coating coated ones exhibited two times higher load bearing capacity in Hertzian indentation test at the same displacement of 1 mm; they appeared to be stiffer and harder at constant load of 20 N, and showed better impact resistance at impact energy range of 0.25–0.75 J in the falling weight test; besides, fatal radial cracks were not observed in gradient coatings after the tests. In addition, the gradient coating had higher emissivity (0.838) than the monolayer dense coating (0.816) because of the significant absorptivity increase and reflectivity decrease by small gradual slopes in the rough surface. [ABSTRACT FROM AUTHOR]

Directional ice-templated ceramics have unique lamellar porous channels between ceramic walls which run from bottom to top of the samples. This highly oriented morphology results in the anisotropy in mechanical properties both parallel and perpendicular to freezing direction. In this research, fiber-enhanced ice-templated porous ceramics were fabricated by introducing fibers into alumina slurry for freezing. The trans-lamellar fiber bridges connecting adjacent ceramic walls were formed by adjusting the aspect ratio of fibers and freezing velocity, which greatly enhanced the compressive response in two directions and weakened the anisotropy in mechanical properties of the directional ice-templated ceramics. The results showed that the of fiber bridges increased with the increase of fiber aspect ratio and the longitudinal and transverse mechanical properties increased by 73.5% and 232.6%, respectively. [ABSTRACT FROM AUTHOR]

Electrode materials with high specific capacity and cycle stability are the key factors that determine the overall performance of lithium ion batteries (LIBs) for new smart electronic device, and such materials with high performance are still challenging. Here, we report a composite material Carbon nanotube @ Iron oxide @ Carbon (γ-CNTs@γ-Fe 2 O 3 @C) with coaxial cable structure in hydrothermal method with the assistance of glucose. The as-prepared composite materials show superior electrochemical properties with good rate capability and excellent cycling performance, which show the great potential of CNTs@γ-Fe 2 O 3 @C for practical production and application in energy devices. [ABSTRACT FROM AUTHOR]

Mullite fibrous ceramics with a two-dimensional planar random structure was prepared via a pressure infiltration method. The in-plane and out-of-plane mechanical properties, thermal expansion coefficients and thermal conductivities were compared. MoSi 2 -borosilicate glass coatings were applied on two adjacent surfaces of the as-prepared mullite fibrous ceramics via an in-situ reaction method. The bonding strength and thermal shock resistance of the two coatings were compared. Results show that higher crosslinking degree and more fiber orientating in the planes resulted in the fact that the in-plane compressive and tensile strength of the ceramics were 4.6 times and 2.1 times higher than the out-of-planes values, respectively. The in-plane CTE (Coefficient of Thermal Expansion), thermal conductivity and permeability were also higher than the out-of-plane ones. The interface bonding strength of Coating B (coated perpendicular to the planes) was higher than that of Coating A (coated parallel to the planes), because of the better mechanical locking at the interface and the higher tensile strength of the substrate. Besides, Coating B presented a better thermal shock resistance because the CTE of the substrate parallel to Coating B was closer to the CTE of the coating, and the substrate was more complaint parallel to Coating B so that could absorb some of the thermal stress by deformation. [ABSTRACT FROM AUTHOR]

A room temperature curable heat-resistant adhesive with broad working temperature range was prepared through organic and inorganic modification. The preceramic polymethylsiloxane showed low bonding strength for silicon carbide from 400 °C to 600 °C because of the decomposition of polymer network. So the modification with epoxy resin was used to generate strong blending and copolymerization network which decomposed at higher temperature over 500 °C. The ceramization of active fillers and preceramic polymer compensated the bonding strength with rising temperature, thus eliminating the weak stage from 400 °C to 600 °C. The modification with fillers greatly improved its bonding strength at high temperature over 1000 °C. Consequently, the modified adhesive exhibited outstanding bonding strength tested at room temperature between 9.29 ± 0.56 MPa and 37.28 ± 1.33 MPa after heat-treatment from 25 °C to 1500 °C and the bonding strength directly tested at the temperature from 25 °C to 800 °C over 8.21 ± 0.40 MPa. The adhesive shows the potential to extend the application for engineering ceramic joining. [ABSTRACT FROM AUTHOR]

Hydrogenated amorphous silicon (a-Si:H) thin film has important applications in optoelectronic devices. In this work, a new analytical method of spectroscopic ellipsometry has been proposed, which can be used to calculate the density of electronic states and the optoelectronic parameters in a-Si:H. Meanwhile, the material structures, the optoelectronic properties and the relationship between them have been analyzed. Results show that the variation in electronic structure is directly related to the thin film structure. The increase of disorder in amorphous network has a strong impact on the DOS in band tails, especially in the valence band tail. The main source of variation in the peak position of dielectric function and the optical gap is the content of bonded hydrogen in the thin film. Likewise, the decrease in the amplitude of dielectric function is due primarily to the reduction in effective valence electrons induced by density deficit. Moreover, the optical absorption exhibits a contrary trend in the energy region below and above ∼1.7 eV. This is because the sample s with higher deposition temperature have larger DOS in band tails and lower optical gap. [ABSTRACT FROM AUTHOR]

Buoyancy material with high temperature resistance was successfully prepared through a tert-butyl alcohol gelcasting process. Borosilicate glass (BG) and hollow glass microspheres (HGMs) with different average diameters were used as the matrix and the filler, respectively. Results show that the compressive strength increased with the decrease of the mean diameter of HGMs, and the sample consisting of the filler of HGMs with a small average diameter exhibited high compressive strength of 25.04 MPa. Young's modulus values of the composite sintered at 700 °C and 750 °C were distributed over in the range of the values predicted from Ashby-Gibson model to Hashin-Shtrikman model and other moduli values agreed well with that of Past model prediction. Weibull moduli ( m ) reflecting the variation degree of the sample compressive strength were in the range of 5–15. The compressive strength of the composites composed of the HGMs with small average particle size tested at 500 °C was as high as 7.94 MPa. [ABSTRACT FROM AUTHOR]

A type of buoyancy material with excellent temperature resistance was successfully prepared through a molding method, and the hollow glass microspheres (HGMs) and silicon oxide (SiO 2 ) were used as the filler and the matrix, respectively. The effect of sintering temperature on mechanical performance, microstructure, and high-temperature performance of the HGMs/SiO 2 composite were investigated in the study. The HGMs/SiO 2 composite exhibited low density (0.47–0.53 g/cm 3 ), high porosity (66.7–75.6%), low thermal conductivity (0.18–0.27 W/(m·K)), and relatively high compressive strength (3.8–5.2 MPa) properties. The values of Weibull moduli m used to predict the variation degree of compressive strength during the compression process was in the range of 5–15 and its values for the samples sintered at 850 °C was 14.64. Two stages namely elastic stage and fracture stage were shown in the stress-strain curves and in the elastic stage, the stress increased linearly with increasing of the strain until reaching the maximum stress. In the fracture stage, the sample gradually destroyed with further increasing of the strain until complete failure. The compressive strength of the HGMs/SiO 2 composites tested at high-temperature was larger than that of the one tested at room temperature. The HGMs/SiO 2 composite exhibited low density, low thermal conductivity and excellent temperature resistance properties and can be used as the structural material or buoyancy material in the deep sea field in the near future. [ABSTRACT FROM AUTHOR]

TaSi 2 -MoSi 2 -borosilicate glass coatings with high emissivity were prepared on mullite fibrous ceramics via a slurry technique to enhance surficial thermal radiation and serve in the thermal protection systems for aircrafts. The effect of TaSi 2 dosages on the coatings' structure, phase composition, emissivity, thermal shock resistance and thermal endurance were investigated. The results show that all the coatings were flat and uniform, while the surface roughness and porosity increased with TaSi 2 dosages. Part of TaSi 2 was oxidized into Ta 2 O 5 during the coating preparation, and finally, the coating with TaSi 2 dosage of 45 wt% (C-45Ta) had the highest TaSi 2 content. Emissivity of the coatings increased with TaSi 2 contents. The total emissivity of C-45Ta was 0.855 in the range of 3–14.5 μm at 150 °C, while that of the coating without TaSi 2 (C-0Ta) was 0.809. However, compared with C-0Ta, C-45Ta showed worse thermal shock resistance because of its higher CTE mismatch with the substrate and higher porosity. The thermal endurance of C-45Ta was worse due to the limited oxidation resistance of TaSi 2 and the lower borosilicate glass content. [ABSTRACT FROM AUTHOR]

Two infrared radiating coatings with borosilicate glass as binder and MoSi 2 as emittance agent were prepared on mullite fibrous ceramics by an in-situ reaction method and a two-step method, respectively. The in-situ reaction coating was prepared from Si, B 2 O 3 and MoSi 2 , in which borosilicate glass was obtained through the in-situ reaction of Si, B 2 O 3 and O 2 . By contrast, the two-step method included the preparation of borosilicate glass powders by a melt-quench technique and then coating preparation with MoSi 2 and the glass powders. The structure, phase composition, thermal endurance, infrared radiation property and impact resistance of the two coatings were compared. The results showed that the in-situ reaction coating was denser, and much less MoSi 2 therein was oxidized during sintering (11.3%) than that in the two-step coating (67.0%), resulted from the oxygen diffusion barrier formed by molten B 2 O 3 at approximately 450 °C. The in-situ reaction coating possessed better thermal endurance due to its higher MoSi 2 content and denser structure. In addition, the in-situ reaction coating had higher emissivity (0.787) and better impact resistance (0.051 J) than the two-step coating (0.706, 0.038 J). [ABSTRACT FROM AUTHOR]

Here a facile method to fabricate closed-cell alumina ceramics by binding hollow alumina spheres with high-temperature binder was introduced. Hollow alumina spheres as the pore-forming agent were bonded together by silica and phosphate binder to form closed-cell structure at the high temperatures. The mechanical properties of as-received closed-cell alumina ceramic can be tailored by the volume fraction of hollow alumina spheres and sintering schedule. Besides, the effects of fusing agent B 2 O 3 and chopped mullite fiber on bulk density and compressive strength of closed-cell alumina ceramics were investigated, respectively. The results indicated that the addition of chopped mullite fiber can effectively enhance the compressive strength of the closed-cell alumina ceramic without significant change in bulk density. The compressive strength of the closed-cell alumina ceramics with 62.5% total porosity was 11.97 MPa when 5 wt% B 2 O 3 and 6 wt% chopped mullite fibers were added in the sample. [ABSTRACT FROM AUTHOR]

A B4C reinforced phosphate adhesive for bonding C/C composites was developed. The mechanical properties were tested at room temperature after bonded specimens were treated at different temperatures from room temperature to 1500 °C. The results showed that the addition of B4C could greatly improve adhesive's mechanical properties due to the formation of borosilicate glass and the volume compensation came from B4C's oxidation. The shear strength of bonded specimens decreased gradually from 7.9 MPa at RT to 3.3 MPa at 900 °C; then it increased up to 4.1 MPa at 1300 °C; however, when the temperature was over 1300 °C, the value decreased again but still remained above 2 MPa. [ABSTRACT FROM AUTHOR]

In order to prevent the embrittlement of high emissivity coating coated quartz fiber fabric applied in Thermal Protection System, LaPO 4 fiber coating was prepared on the fiber fabric by a repeated dip-sintering method using a liquid precursor. The formation process of La-monazite from the precursor was investigated, and on this basis, a high-temperature and short-time sintering schedule (1200 °C/60 s) was determined. Pure La-monazite fiber coating with a thickness of 80–300 nm was obtained, and cristobalite crystallization in the fibers was avoided. The La-monazite coated quartz fiber fabric retained the flexibility of the original quartz fiber fabric. By precoating La-monazite fiber coating, the quartz fiber fabric coated with SiC–SiO 2 high emissivity coating showed significantly increased ultimate bending deflection in three-point bending test, and fiber pull out and fabric distortion were observed at the fracture surface. • La-monazite fiber coating was prepared on quartz fabric by a dip-sintering method. • Repeated short-time sintering schedule at relatively high temperature was adopted. • Coating impurities and fabric crystallization/embrittlement were prevented. • High-temperature embrittlement of high emissivity coating coated fabric was relieved. [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]

Abstract: Porous Si2N2O ceramics was synthesized by the tert-butyl alcohol-based gel-casting method at a relatively low temperature using Si3N4 and SiO2 powders as the starting materials and spodumene (LiAl(SiO3)2) as the sintering additive. Porous Si2N2O ceramics with relative high compressive strength (10.80MPa) and high porosity (65.5%) were successfully fabricated. The microstructure of porous Si2N2O after sintering at different sintering regimes was studied. The fibers observed in the pores can increase the compressive strength and the specific surface area of the sample. [Copyright &y& Elsevier]

Abstract: Porous Y2SiO5 ceramics with relative high compressive strength (as high as 24.45MPa) and ultra-low thermal conductivity (∼0.08W/mK) were successfully fabricated by a tert-butyl alcohol based gel-casting method. The formation mechanism of the 3D interconnected pores and the properties of the green body are discussed. The porosity, pore size, compressive strength and thermal conductivity could be controlled by varying the initial solid loading and the sintering temperature. When regulating the initial solid loading (from 20 to 50wt%) and sintering temperature (from 1200 to 1500°C), the porosity can be controlled between 47.74% and 73.93%, and the compressive strength and the thermal conductivity of porous Y2SiO5 ceramics varied from 3.34 to 24.45MPa and from 0.08 to 0.55W/mK, respectively. It should be noted that the porous Y2SiO5 ceramics with 30wt% solid loading and sintering at 1400°C had an open porosity of 61.80%, a pore size of 2.24μm, a low room-temperature thermal conductivity of 0.17W/mK and a relatively high compressive strength of 13.91MPa, which make this porous Y2SiO5 ceramics suitable for applications in high-temperature thermal insulators. [Copyright &y& Elsevier]

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.

Fibers crystallize and become brittle at high temperatures for a long time, so the surface coating must maintain long-lasting emission performance, which requires superior antioxidant properties of the high-emissivity fillers. To improve the radiation performance of the coating and the tensile strength of the fiber fabric, a double-layer coating with high emissivity was prepared on the surface of flexible aluminum silicate fiber fabric (ASFF) using MoSi 2 and SiC as emissive agents. The incorporation of borosilicate glass into the outer coating during high-temperature oxidation of ZrB 2 results in superior encapsulation of emitter particles, effectively filling the pores of the coating and significantly reducing the oxidation rate of MoSi 2 and SiC. Furthermore, the addition of an intermediate ZrO 2 layer enhances the fiber bundle's toughness. The obtained double-coated ASFF exhibits an exceptionally high tensile strength of 57.6 MPa and a high bond strength of 156.2 kPa. After being subjected to a 3 h heating process, the emissivity exhibits a minimal decrease of only 0.032, while still maintaining a high value above 0.9. The thermal insulation composites, consisting of a flexible ASFF matrix and a ZrB 2 -modified double-layer coating, exhibit significant potential for broad applications in the field of thermal protection.

High-entropy ceramics exhibit various excellent properties owing to their high configurational entropy, which is caused by multi-principal elements sharing one lattice site. The configurational entropy will further increase significantly if multi-principal elements randomly share two different lattice sites. For this purpose, pseudobrookite phase containing two cationic lattice sites (A and B sites) is selected, and corresponding high-entropy pseudobrookite (M 2+ 0.4 M 3+ 1.2 )Ti 1.4 O 5 is synthesized. Herein, the distribution of the 2-valent and 3-valent cations in the A and B sites are analysed in depth. The distance between the A and B sites in the crystal structure models which are constructed by the Rietveld analysis is calculated and defined as distance d. Meanwhile, the atomic column positions in the STEM images are quantified by a model-based mathematical algorithm, and the corresponding distance d are calculated. By comparing the distance d, it is determine that the 2-valent and 3-valent cations are jointly and disorderly distributed in the A and B sites in high-entropy (M 2+ 0.4 M 3+ 1.2 )Ti 1.4 O 5 . The density functional theory (DFT) simulations also demonstrate that this type of crystal structure is more thermodynamically stable. The higher degree of cationic disorder leads to a higher configurational entropy in high-entropy (M 2+ 0.4 M 3+ 1.2 )Ti 1.4 O 5 , and endows high-entropy (M 2+ 0.4 M 3+ 1.2 )Ti 1.4 O 5 with very low thermal conductivity (1.187-1.249 W m -1  K -1 )., (© 2024 Wiley‐VCH GmbH.)

The Applications of silica aerogel are limited due to its brittleness and low strength. As a result, it is essential to strengthen and toughen it. Organic nanofibers are one of the preferred reinforcement materials. In this work, we designed and fabricated flexible and compressible nanostructure-assembled aramid nanofiber/silica composites aerogel (ANF/SiO 2 aerogel) to improve the mechanical strength and flexibility of silica aerogel without compromising thermal insulation properties. The aramid nanofiber/silica composite aerogels were prepared by immersing the aramid nanofiber wet gel into the silica sol for a certain period of time followed by freeze drying without solvent replacement. The surface modifier 3-aminopropyltriethoxysilane (APTES) was used as a coupling agent to form chemical linkage between the ANF fiber and silica gel. It was observed that APTES can effectively drive the silica sol to infuse into ANF hydrogel, promoting the assembly of silica gel onto the fiber surface and a uniform distribution in the network of ANF. The compressive resilience, thermal stability, and thermal insulation properties of the composite aerogels were evaluated by inducing the silica aerogel into the ANF network to form a protective layer on the fiber and change the pore structure in the ANF network.

Ceramic fiber thread is one of the key components in flexible external thermal insulation blankets, and it has been applied in various fields as a flexible ceramic fibrous material with excellent deformability and high-temperature resistance. However, ceramic fiber threads are often subjected to reciprocating friction motion at specific bending angles, making them highly susceptible to abrade and fracture. Enhancing the abrasion resistance performance of ceramic fiber threads under bending conditions is the future trend and remains a significant challenge. Hence, we design and construct a novel polyurethane-modified coating on the ceramic fiber threads to improve their abrasion resistance performance. The effects of the types and concentrations of modifiers on the microstructure, abrasion resistance property, and tensile property of ceramic fiber threads are systematically investigated. The ceramic fiber threads, after modification with hexamethylene diisocyanate waterborne polyurethane (HDI-WPU) with a concentration of 3%, exhibit excellent abrasion resistance properties. The number of friction cycles at fracture of the modified ceramic fiber thread is more than three times, and the tensile strength is more than one and a half times, that of the original ceramic fiber thread, demonstrating the great potential of the HDI-WPU modifier for enhancing the abrasion resistance performance of ceramic fiber threads.

The paradoxical effects of cobalt in biological processes have caused controversy regarding the application of cobalt-based biomaterials. Cobalt has recently been shown to be a trace element that promotes bone growth. Qingzhuan Dark Tea polysaccharides (TPS) has been shown to be a biomaterial with antioxidant and immunomodulatory effects. In order to develop a novel immunomodulatory biomaterial, we synthesized polysaccharide cobalt complex (TPS-Co) to prevent the paradoxical effects of cobalt while maintaining its beneficial effects, and evaluated its morphology, structure, and antioxidant activity. Fourier-transform infrared spectroscopy, X-ray diffraction and X-ray photoelectron spectroscopy demonstrated that cobalt complexed successfully with TPS. Scanning electron microscopy and atomic mechanical microscopy demonstrated that TPS-Co has a more homogeneous and concentrated morphological distribution compared to TPS. Thermal performance analysis demonstrated that TPS-Co has higher thermal stability. Atomic absorption spectroscopy showed a cobalt content of 3.8%. Ultraviolet spectroscopy indicated that TPS-Co does not contain nucleic acids and proteins. Antioxidant activity assays showed that TPS-Co has better antioxidant activity than TPS in the concentration range of 0.4-2 mg/mL. Proliferation assay of MC3T3-E1 cells demonstrated that TPS-Co has the best cell proliferation effect at a cobalt concentration of 2 ppm. Therefore, TPS-Co may have potential applications in bone regeneration., Competing Interests: The authors declare no conflict of interest., (© 2023 The Authors.)

Porous fiber-based ceramics have been widely applied in various fields because of their excellent thermal insulation property and high thermal stability property. However, designing porous fibrous ceramics with enhanced comprehensive performances, such as low density, low thermal conductivity, and high mechanical properties at both room temperature and high temperature, is still a challenge and the future development trend. Hence, based on the lightweight cuttlefish bone that possesses a "wall-septa" structure with excellent mechanical performance, we design and fabricate a novel porous fibrous ceramic with the unique fiber-based dual structure of lamellas by the directional freeze-casting method and systematically investigate the effects of lamellar components on the microstructure and mechanical performances of the product. For the desired cuttlefish-bone-structure-like lamellar porous fiber-based ceramics (CLPFCs), the porous framework formed by the overlapping of transversely arranged fibers helps to reduce the density and thermal conductivity of the product, and the longitudinally arranged lamellar structure replaces traditional binders and plays an important role in improving the mechanical properties in the direction parallel to the X - Z plane. Compared with traditional porous fibrous materials reported in the literature, the CLPFCs with an Al 2 O 3 /SiO 2 molar ratio of 1:2 in the lamellar component exhibits prominent comprehensive performances, such as low density, excellent thermal insulation property, and outstanding mechanical performances at both room temperature and high temperature (3.46 MPa at 1300 °C), indicating that the CLPFCs are a promising candidate for applications in high-temperature thermal insulation systems.

Several vascular embolization materials are commonly used in clinical practice, however, having application defects of varying degrees, such as poor intraoperative imaging and easy recanalization of embolized blood vessels, they are challenging for application during Transcatheter arterial embolization (TAE). Thus, an intraoperative visible vascular embolization material with good embolization effect and biocompatibility can improve transcatheter arterial embolization clinical efficacy to some extent. Our study aimed to synthesize a novel vascular embolization material that can achieve complete embolization of arterial trunks and peripheral vessels, namely poly (N-isopropyl acrylamide)- co -acrylic acid nanogel (NIPAM- co -AA). Iohexol 200 mg/mL was co-assembled with 7 wt% NIPAM- co -AA nanogel to create an intelligent thermosensitive radiopaque nanogel (INCA), which achieves a good intraoperative imaging effect and is convenient for transcatheter arterial bolus injection due to its good fluidity and temperature-sensitive sol-gel phase transition. The normal rabbit kidney embolism model further confirmed that INCA could effectively use Digital subtraction angiography (DSA) to achieve intraoperative imaging, and real-time monitoring of the embolization process could avoid mis-embolization and leakage. Meanwhile, in a 42-day study, INCA demonstrated an excellent embolization effect on the right renal artery of New Zealand white rabbits, with no vascular recanalization and ischemic necrosis and calcification remaining. As a result, this radiopaque thermosensitive nanogel has the potential to be an intelligent thermosensitive medical vascular embolization material, providing dual benefits in TAE intraoperative imaging and long-term postoperative embolization while effectively addressing the shortcomings and challenges of commonly used clinical vascular embolization agents., Competing Interests: No potential conflict of interest was reported by the author(s)., (© 2023 The Author(s). Published by Informa UK Limited, trading as Taylor & Francis Group.)