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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]

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 MoSi2 and SiC as emissive agents. The incorporation of borosilicate glass into the outer coating during high-temperature oxidation of ZrB2 results in superior encapsulation of emitter particles, effectively filling the pores of the coating and significantly reducing the oxidation rate of MoSi2 and SiC. Furthermore, the addition of an intermediate ZrO2 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 ZrB2-modified double-layer coating, exhibit significant potential for broad applications in the field of thermal protection. [ABSTRACT FROM AUTHOR]

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/SiO2 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. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

Fibrous porous materials are one of the most commonly used high-temperature insulation materials because of their high porosity and low thermal conductivity. Due to their wide applications in the aerospace and energy industries, the investigation of high-elastic thermally insulating porous materials has attracted increasing attention. In order to improve the elasticity of fibrous porous materials, quartz fibers with high aspect ratio were used as matrix, sodium hexametaphosphate (SHMP) was selected as dispersant. We innovatively reported that a unique three-dimensional skeleton structure was constructed by adjusting the dispersion of fibers in the slurry, and the lightweight, thermal insulating and elastic SiO2 fibrous porous material was then prepared by the compression molding method. The characterization results of zeta potential and absorbance showed that the addition of SHMP was an effective method to enhance the dispersibility of quartz fibers in the slurry. SiO2 fibrous porous materials with 0.4 wt% SHMP content exhibited an ideal three-dimensional skeleton structure, which endowed the porous material with high porosity (89.39%), low density (0.04751 g/cm3), and low thermal conductivity (0.0356 W·m−1·K−1). The three-dimensional skeleton structure formed by overlapping fibers with high aspect ratios endowed the porous material with excellent elasticity. SiO2 fibrous porous materials with 0.4 wt% SHMP content could undergo large strains of 30% and achieved a resilience ratio of 81.69% under the 30th compression cycle. Moreover, after heat treatment at 800 °C, SiO2 fibrous porous materials also maintained good elasticity with a resilience ratio of more than 80%. [ABSTRACT FROM AUTHOR]

Metal-doped polymer derived ceramics (PDCs) exhibits multifunctional properties due to the introduction of special metal element; however as one of the cheapest metal element carriers, metal inorganic salts have rarely been reported for the fabrication of metal-doped PDCs. In this article, a novel hydrophilic photosensitive γ-methacryloxypropyl trimethoxy modified polyhydroxymethylsiloxane preceramic polymer was firstly synthesised and three different metal-doped SiOC ceramic lattices with a strut thickness of 200 μm were successfully fabricated using inorganic metal salts as the metal source by digital light processing. The photosensitive coefficient, initial photocuring coefficient and the corresponding working curves were employed to evaluate the photocurable ability of preceramic polymers with different recipes. Results showed that both the metal-containing polymer lattices and the metal-doped SiOC ceramic lattices exhibited high-resolution microstructure and homogeneous metal element distribution, indicating that the inorganic metal salt is an effective metal source for the fabrication of metal-doped PDCs. [ABSTRACT FROM AUTHOR]

Abstract: Silica sol is one of the frequently used binders in high‐temperature resisting fibrous porous ceramics, but in the drying process, it can diffuse with water and influence the uniformity of ceramics. To solve this diffusion problem and fabricate homogeneous fibrous porous ceramics, cationic starch was firstly introduced in mullite fibrous system. The effects of starch content and high‐temperature binder content on microstructure, physical, and mechanical properties were also investigated. The results indicate that starch consolidated mullite fibrous ceramics owned a homogeneous 3D skeleton structure, since the introduced starch can absorb both water and silica particles by gelatinization and ensure the even distribution of binders. Compared with the mullite fibrous ceramics fabricated without starch addition, starch consolidated ceramics owned better microstructure and higher interior compression strength. Furthermore, both the starch and silica sol content had great impact on the microstructure, density, porosity, thermal conductivity, and compressive strength of the fibrous ceramic. [ABSTRACT FROM AUTHOR]

Fine-grained mullite nanofibers derived from the diphasic mullite sol were successfully fabricated by electrospinning and subsequent pyrolysis at 1500°C. Polymethylsiloxane and aluminum tri-sec-butoxide were selected as the silicon and aluminum source to synthesize the diphasic sol. Results show that the weight loss of mullite precursor fibers in our work was about 60 wt.%, which is similar with that of fibers fabricated using the monophasic sol. This low weight loss was mainly attributed to the high ceramic yield of polymethylsiloxane and low introduced polyvinylpyrrolidone content, which ensures the integrity of fiber morphology during the sintering process. Mullite fibers with 216 nm average diameter were fabricated after sintered at 1500°C and the corresponding grain size was only ~100 nm, much smaller than that in mullite fibers derived from monophasic sols. Therefore, it can be predicated that mullite fibers in this work should possess a higher mechanical strength than those derived from monophasic sols when the sintering temperature was higher than 1400°C and therefore was an ideal starting materials for the fabrication of mullite nanofibrous ceramics used as the high-temperature thermal insulation materials. [ABSTRACT FROM AUTHOR]

Water-glass-based pastes show good prospect for high-temperature applications, but they are subject to substantial dry-shrinkage. Silicon and aluminum powders were added to prevent the dry-shrinkage. The influence of them on compressive strength, bonding strength and volume of the pastes was discussed. SEM, XRD, and TG/ DSC were employed to study the influencing mechanisms. The results show that Si and Al effectively prevented the dry-shrinkage; Al improved compressive strength and bonding strength, while Si was bad for bonding strength. When Al dosage was 6%, the pastes presented mild expansion of 1.05%, the compressive strength increased by 8.9%, and the bonding strength by 33.4%. [ABSTRACT FROM AUTHOR]

NiCo2O4/CNT nanocomposite films were fabricated by in-situ growing ultrafine NiCo2O4 nanoparticles on acid-modified carbon nanotube (CNT) films. The effects of CNT-film pretreatment were investigated thoroughly by various characterization outfits including Fourier Transform Infrared spectroscopy (FT-IR), X-ray photoelectron spectroscopy (XPS), Raman spectroscopy, RTS-9 four-point probes resistivity measurement system, X-ray powder diffraction (XRD), scanning electron microscopy (SEM) and CHI660D electrochemical workstation. These results suggested that carbon nanotubes were uniformly wrapped by NiCo2O4 nanoparticles forming a hierarchical core-shell structure. And the crystallinity, conductivity of the CNTs and detail structure (both morphology and size) of the NiCo2O4 nanoparticles varied with prolonged acid treatment time which resulted in increased functional groups and defects on CNT films and further affected the electrochemical properties. The composite film composed of the CNT film pretreated by mixed acid for 12 h exhibited excellent electrochemical properties: 828 F/g at 1 A/g and 656 F/g at 20 A/g, and maintained over 99 % of its capacitance after 3000 cycles of charge/discharge at 5 A/g. Acid treatment for either too long or too short is detrimental to the electrochemical properties of the composite films. Such work should be of fundamental importance for tailoring electrochemical properties by elaborate design of acid treatment on CNTs. [ABSTRACT FROM AUTHOR]

We use metal-assisted chemical etching (MCE) method to fabricate nanostructured black silicon on the surface of C-Si. The Si-PIN photoelectronic detector based on this type of black silicon shows excellent device performance with a responsivity of 0.57 A/W at 1060 nm. Silicon nanocone arrays can be created using MCE treatment. These modified surfaces show higher light absorptance in the near-infrared range (800 to 2500 nm) compared to that of C-Si with polished surfaces, and the variations in the absorption spectra of the nanostructured black silicon with different etching processes are obtained. The maximum light absorptance increases significantly up to 95 % in the wavelength range of 400 to 2500 nm. Our recent novel results clearly indicate that nanostructured black silicon made by MCE has potential application in near-infrared photoelectronic detectors. [ABSTRACT FROM AUTHOR]

Continuous carbon nanotube (CNT) networks were formed in Cf/SiC composites via freeze-drying method. Composites were fabricated by precursor infiltration and pyrolysis (PIP) process afterwards. The different distribution morphologies of CNTs in the preforms originating from the different CNT contents were analyzed while the influence of the distribution of CNTs was discussed in detail. Compared to composites without CNTs, the interfacial shear strength (ILSS) and the flexural strength of Cf/1%CNTs/SiC were increased by 31% and 27%, respectively, but the values of Cf/2.5%CNTs/SiC decreased as a result of lots of defects caused by excess CNTs. With the analysis of ILSS, the flexural strengths, and the fracture morphologies, CNTs effectively improved the weak interfacial strength between T700SC carbon fibers and SiC matrix. [ABSTRACT FROM AUTHOR]

We report the Raman analysis of both as-deposited and annealed amorphous silicon ruthenium thin films embedded with nanocrystals. In the Raman spectra of as-deposited films, variations of TO peak indicate a short-range disorder of a-Si network with an increase of Ru concentration. The substitutional Ru atoms lower the concentration of Si-Si bonds and suppress the intensity of TO peak, but have less effect on TA, LA and LO peaks. In the Raman spectra of annealed films, characteristic parameters confirm the upgrade of a-Si network at a low annealing temperature and the emergence of both ruthenium silicide and silicon nanocrystals at 700 °C. Although ruthenium silicide nanocrystals present no Raman peaks in the Raman spectra of as-deposited samples, the non-linear variations of intensity ratios ILA + LO/ ITO and ITA/ ITO still suggest their existence, and these nanocrystals are subsequently verified by high-resolution transmission electron microscopy. Copyright © 2015 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

Carbon/carbon( C/ C) composites were bonded with a phosphate adhesive prepared from H3 PO4 (orthophosphoric acid) and Al( OH)3 as the matrix and Si and Cu O as the inorganic fillers. The mechanical properties were tested at room temperature after the bonded specimens were treated from RT to 1500°C. The results showed that the addition of Cu O could greatly improve the adhesive's mechanical properties due to the formation of Cun Si (copper silicides). The shear strength of bonded specimens could be up to 8.2 MPa without heat treatment and remain above 2 MPa within the whole heat-treatment temperature range. [ABSTRACT FROM AUTHOR]

In this study, silicon oxycarbide (SiOC) ceramic fiber mats obtained by electrospinning of two different preceramic polymers (MK and H44 resin) were evaluated in terms of their total porosity and other structural characteristics using three different characterization tools. The tensile strength and the permeability of the fiber mats were also investigated. The results indicated that the porosity could be easily calculated based on the apparent density and true density of the fiber mats obtained by gas pycnometry. A modified mercury intrusion porosimetry, in which the bulk volume of the fiber mats was calculated based on its independently measured bulk density, also allowed for an accurate evaluation of the porosity and the pore size distribution of the fiber mats. X-ray computed tomography was able to provide various structural characteristics of the 3D morphology of the fiber mats, but it was less effective in the determination of the total porosity due to resolution limits. All results showed that the MK-derived SiOC fiber mats possessed a higher porosity than the H44-derived SiOC fiber mats, resulting in a higher gas permeability. The ceramic fiber mats possessed a suitable permeability for filtration applications in harsh environments. [ABSTRACT FROM AUTHOR]

Various electrospun metal/SiOC (Ag/SiOC, Co/SiOC, and Cu/SiOC) composite fibers were synthesized via a carbon thermal reduction of four kinds of metal source (silver oxide nanoparticles, silver acetate, cobalt acetate, and copper trifluoro acetylacetonate). XRD results indicate that both common metal-organic metal precursors and seldom used metal oxide particles were successfully carbon thermally reduced to the corresponding metallic particles embedded in SiOC fibers, indicating that the range of metal source choices suitable for this method is quite broad. Further SEM and TEM analysis revealed that the shape and size of the formed metal particles were determined by the characteristics of the metal source in the electrospinning solution, which means these features of the metal particles can be adjusted by taking into account the solubility of the precursors in the chosen solvents. The prepared Ag/SiOC composite fibers possessed antibacterial activity for both Gram-negative E. coli bacteria and Gram-positive S. aureus bacteria and suitable permeability (~1 × 10 m), constituting a promising material for antibacterial filtration application. [ABSTRACT FROM AUTHOR]

ABSTRACT Silicon oxycarbide (SiOC) fibers with different chemical compositions were successfully fabricated by electrospinning a mixture of polyvinylpyrrolidone (PVP) and commercially available polymethylsilsesquioxane (MK) or polymethylphenylsilsesquioxane (H44) preceramic polymers, followed by cross-linking and pyrolysis at 1000°C in Argon. The influence of the processing procedure (solvent selection, cross-linking catalyst and additives) on the morphology of the produced fibers was investigated. For the MK/isopropanol system, the introduction of 20 vol% N,N-dimethylformamide (DMF) enabled to decrease the diameter of the as-spun fibers from 2.72 ± 0.12 μm to 1.65 ± 0.09 μm. For the H44/DMF systems, beads-free fibers were obtained by adding 50 vol% choloroform. After pyrolysis, the resultant SiOC fibers derived from MK and H44 resins possessed uniform morphology, with an average diameter of 0.97 ± 0.07 μm and 1.07 ± 0.08 μm, respectively. Due to their different chemical compositions, the MK-derived and H44-derived SiOC ceramic fibers could find different potential applications. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014, 131, 39836. [ABSTRACT FROM AUTHOR]

The mullite ceramic/fiber brick system was bonded by two kinds of phosphate adhesives. The specimens were treated from 200 to 1400°C. The mechanical properties were tested at room temperature and at high temperature, and the relevant bonding mechanism was also discussed. The results show that the addition of silicon can greatly improve the adhesive's mechanical properties. The room-temperature shear strength of the component bonded by adhesive with the silicon calcined at 800°C can reach 6.58 MPa. The shear strength of the adhesive with silicon tested at 800°C can reach 0.42 MPa. [ABSTRACT FROM AUTHOR]