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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]

The features of avalanche region are of importance of SPAD. An ideal broad and rectangular avalanche field may reduce dark count rate but could hardly be realized by actual fabricating technology. We propose a new fabrication process including successive boron and phosphorus diffusions for building special doping compensated avalanche region. A low dark count rate below 10 cps at −20 °C and high photon detection efficiency about 70% at 850 nm are achieved. The afterpulsing probabilities are 2.3% at 20 °C and 3% at 0 °C. FWHM of time resolution is 340ps. [ABSTRACT FROM AUTHOR]

Thermal protection was always a prominent issue in the aerospace industry. For vehicle safety, reliability and payload requirements, thermal protection materials were usually expected to possess low density, superior mechanical and thermal insulation properties. Here, lightweight and high-strength porous mullite-silica ceramics were manufactured using particle-stabilized foaming technique. The strength and thermal insulation properties of porous ceramics modified with hollow silica spheres were significantly enhanced. A 10 wt% hollow spheres addition achieved a 28.9 % increase in strength and a 33.4 % decrease in thermal conductivity with almost constant porosity (from 86.39 % to 87.04 %). Considering the characteristics of light weight, high compression strength and superior thermal insulation performance, porous ceramics could be applied as thermal protection materials in the aerospace sector. [ABSTRACT FROM AUTHOR]

Abstract Highly porous mullite fiber-based ceramics with a three-dimensional cross structure were successfully designed and fabricated by filtration method. To address the thermal migration of silica sol, polysiloxane was introduced in the bonding system as high temperature binder to form more stable nods in the skeleton as opposed to silica sol which would migrate to the surface of fibers during the sintering process. Due to the lapped structure of mullite fibers, all products showed high porosity(74.1%∼80.9%), low density(0.554g/cm3∼0.608g/cm3) and relatively low thermal conductivity(<0.14 W/(m*K)). The reaction process of in situ porolysis and fracture mechanisms were illustrated, respectively. Besides, results showed that both sintering temperature and binder content had significant influence on the microstructure and mechanical properties of the products. [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]

Novel plastic deformation was exhibited in amorphous oxides, attributed to the metastable state of amorphous phase with free volume and disordering structure; however, metastable degrees can be quite different in amorphous phases, and the effect of metastability on plastic deformation was never reported in amorphous oxides. In this work, the metastable degree of amorphous phase was controlled by adjusting the temperature in powder calcination, and evaluated through free volume and disordering degree, using the true density of amorphous powder, DSC and 27 Al MAS-NMR. Under compression at 500 °C, the sample with lowest metastability exhibited brittle fracture; however, the other two with higher metastable degrees displayed plastic strain of 3.5% and 5.2%. The enhanced plastic deformation benefited from higher metastability was mainly attributed to easier formation of shear bands. For amorphous phase with higher metastability, the atomic mobility and local free volume were larger, which could improve the formation of shear bands and promote the plasticity according to free volume theory. This work could inspire new methods to improve the plastic deformation in amorphous materials. [ABSTRACT FROM AUTHOR]

Silver/amorphous silicon (Ag/a-Si) memristor has attracted extensive attention as a candidate for next-generation nonvolatile memories. The optical constant variations of a-Si layer during switching procedure, which are the key for Ag/a-Si memristor to be used in optical applications, have not been clarified yet. To take a further understanding on the optical feathers of Ag/a-Si memristor, here we report the microstructure, resistivity and dispersion relation of amorphous silicon silver (a-Si 1−x Ag x ) thin films prepared by co-sputtering. Ag nanocrystals are observed in the films with size similar to the Ag filament in memristor, and the obtained resistivities of the films march the typical ON/OFF ratio of memristor. Furthermore, both the film's refraction index and extinction coefficient increase with Ag concentration, suggesting that Ag/a-Si memristor combining with silicon waveguide could be applied in optical switch at 1300 and 1550 nm. [ABSTRACT FROM AUTHOR]

Silicon is widely used in semiconductor industry but has poor performance in near-infrared photoelectronic devices because of its bandgap limit. In this study, a narrow bandgap silicon rich semiconductor is achieved by introducing ruthenium (Ru) into amorphous silicon (a-Si) to form amorphous silicon ruthenium (a-Si 1- x Ru x ) thin films through co-sputtering. The increase of Ru concentration leads to an enhancement of light absorption and a narrower bandgap. Meanwhile, a specific light trapping technique is employed to realize high absorption of a-Si 1- x Ru x thin film in a finite thickness to avoid unnecessary carrier recombination. A double-layer absorber comprising of a-Si 1- x Ru x thin film and silicon random nano-holes layer is formed on the back surface of silicon substrates, and significantly improves near-infrared absorption while the leaky light intensity is less than 5%. This novel absorber, combining narrow bandgap thin film with light trapping structure, may have a potential application in near-infrared photoelectronic devices. [ABSTRACT FROM AUTHOR]

The method of in situ synthesis of mullite whiskers by gas-phase deposition and reaction was applied to improve the compressive strength of the mullite fiber brick. During the preparation process, silica sol, Al(NO 3 ) 3 solution and NH 4 F solution were introduced into the fibrous brick in the form of ions or sol through vacuum impregnation and freeze drying, and the silica sol, Al(NO 3 ) 3 and NH 4 F served as the silica sources, aluminum source and catalyst, respectively. Effects of process parameters (concentration of impregnation solutions, holding time, sintering temperature) on compressive strength and elastic modulus of the fibrous brick during the in situ toughening process were analyzed. SEM and XRD analysis results demonstrated that the mullite whiskers were synthesized on the surface of mullite fibers based on the reaction of AlOF and SiF 4 . What is more, the whiskers on adjacent fibers intersected with each other and formed many unfixed lap-jointing points, resulting in the increase of compressive strength and elastic modulus. Although the density and thermal conductivity of the sample after the generation of mullite whiskers fabricated with the optimum process were 0.406 g/cm 3 and 0.1262 W/(m K), respectively, which were slightly higher than that of the raw fibrous brick (0.375 g/cm 3 density and 0.1069 W/(m K) thermal conductivity, respectively), the corresponding compressive strength and elastic modulus of the sample reinforced with the whiskers increased to 1.45 MPa and 42.03 MPa, respectively, which were much higher than that of the raw fibrous brick (0.39 MPa compressive strength and 6.5 MPa elastic modulus). [ABSTRACT FROM AUTHOR]

A novel temperature resistance buoyancy material with hollow glass microspheres (HGMs) as the filler and borosilicate glass (BG, similar chemical composition to the HGMs) as the high temperature matrix was prepared by a tert-butyl alcohol based on gelcasting process. The effect of solid loading and sintering temperature on microstructure and mechanical properties were investigated. The results showed that HGMs were bonded together by borosilicate glass and 45 wt.% solid loading and 700 °C were the optimal processing parameters to fabricate the samples with the best mechanical and thermal properties, and the corresponding bulk density, compressive strength, thermal conductivity and Young’s modulus were 0.92 g/cm 3 , 14.46 MPa, 0.15 W/m K and 1.24 GPa, respectively. The exponent m value for the samples fabricated in this work was 1.18, lower than that of open- or closed-cell foams, because the sample possess both the closed and open pores. The experimental values of thermal conductivity from 0.07 to 0.16 W/m K were lower than the prediction with the Hashin–Shtrikman upper bound and almost close to that predicted by the Landauer’s relation. Only modulus value of SSL45 sample which possessed the maximum value was closer to Hashin–Shtrikman upper bound, while the modulus value of other samples agreed well with Ashby–Gibson model applied for a porosity ranging from 65% to 89%. The HGMs/BG composite exhibited a low density, low thermal conductivity and excellent temperature resistance, and can be used as the thermal insulation for undersea pipeline or submarine. [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]

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]

The structural variation and electrical properties in both as-deposited and annealed amorphous silicon ruthenium thin film are investigated. Results indicate that the introduced Ru atoms further degrade the amorphous network order and Ru 2 Si nanocrystals are found in the as-deposited sample. The phase transformation of ruthenium silicide and the formation of Si nanocrystals are observed after annealing treatment. Significant resistivity reduction is obtained with the increase of Ru concentration. This material is a potential candidate for infrared detectors. [ABSTRACT FROM AUTHOR]

Hierarchically structured polymer-derived ceramic fibers were successfully produced by electrospinning a commercially available preceramic polymer to which a cobalt-based catalyst precursor was added, followed by pyrolysis in nitrogen at temperatures ranging from 1250 to 1400°C. The nanowires formed via the vapor–liquid–solid (VLS) mechanism, involving the reaction of SiO and CO gases, generated from the decomposition of the polymer-derived-ceramic at high temperature, with the heating atmosphere assisted by the presence of nano-sized CoSi droplets. The main crystalline phase for the nanowires was Si3N4 below 1350°C, and Si2N2O at 1400°C, and the amount of nanowires increased with increasing heating temperature. Hierarchically structured fiber mats possessed a higher specific surface area (14.45m2/g) than that of a sample produced without the cobalt catalyst (4.37m2/g). [ABSTRACT FROM AUTHOR]

Abstract: Porous silica ceramics were successfully prepared from silica spinning solution and introduced silica particles by electrospinning. After sintering, the sample was mainly composed of the introduced silica particles instead of the electrospun ceramic fibers. Therefore, the role of the introduced particles in this work was quite different from that of the introduced fillers in other electrospinning works. The porosity of the samples sintered at 1000°C and 1200°C were 62.4% and 55.6%, respectively. Furthermore, the porosity of the sintered sample can be adjusted by changing the content of the introduced silica particles. This method can be extended to prepare other porous ceramics just by changing the kinds of introduced particles. [Copyright &y& Elsevier]

Thermal protection has always been an important issue in the energy, environment and aerospace fields. Porous ceramics produced by the particle-stabilized foaming method have become a competitive material for thermal protection because of their low density and low thermal conductivity. However, the study of porous ceramics for composite systems using particle-stabilized foaming method was relatively rare. Here, silica-alumina composite porous ceramics were prepared by particle-stabilized foaming method, which was achieved by tailoring the surface charges of silica and alumina through adjustment of the pH. Porous ceramics exhibited porosity as high as 97.49% and thermal conductivity (25 °C) as low as 0.063 W m−1 K−1. The compressive strength of porous ceramics sintered at 1500 °C with a solid content of 30 wt% could reach 0.765 MPa. Based on the light weight and excellent thermal insulation properties, the composite porous ceramic could be used as a potential thermal insulation material in the spacecraft industry. [ABSTRACT FROM AUTHOR]

Abstract: Porous mullite ceramics was fabricated by a combination of electrospinning and pressure molding method. Different from the previous reports, the electrospinning in this experiment was just a method of arranging the whiskers into a non-woven structure and coating the whiskers with the TEOS; the pressure molding was used as the final forming method. The sample''s microstructure and phase compositions were investigated by means of scanning electron microscopy (SEM) and X-ray diffraction (XRD). In addition, their physical and mechanical properties were also measured. The prepared porous ceramics exhibited an interesting microstructure: The main body was built of layer-by-layer mullite whiskers with the silica as the high temperature binder, and the whiskers on each layer showed a non-woven structure. [Copyright &y& Elsevier]

Abstract: A novel technique of flyash utilization was presented and mullite ceramics were prepared from flyash and desilication-flyash. The effect of desilication process was analyzed and the result shows that the only difference between flyash and desilication-flyash lies in the silica content, which is caused by the removal of silicate glassy phase during the desilication process. The physical and mechanical properties of flyash sample and desilication-flyash samples were measured. All results indicate that the desilication-flyash is more suitable to be used to prepare the mullite ceramics than flyash. The inner structure of flyash particle was first discovered, which can help us form a new description of the flyash particle and finally benefit the utilization of flyash. Lath-like mullite crystals appeared in high-iron samples and needle-like mullite crystals were observed in low-iron samples. The flexural strength of high-iron sample was higher than that of low-iron sample because of the formation of network structure consisting of many interlocked lath-like mullite crystals in high-iron samples. [Copyright &y& Elsevier]

High emissivity coatings on hypersonic vehicle surfaces dissipate heat by emitting thermal radiation. While the difficulty of increasing emissivity limits the performance of coatings to improve heat-dissipation of the thermal insulation felt. Herein, a novel high-reflectivity and high-emissivity integrated double-layer coating was developed to enhance the thermal insulation performance of the alumina fiber fabric. The coating comprised of TiO 2 @SiO 2 (T@S) as reflective agent and ZrO 2 /SiC w (ZSC) as emittance agents, was applied on the surface of alumina fiber fabric (AFF). The reflecting effect of radiation heat from the high reflective agent enhanced the thermal insulation properties of the double-layer coating. In the wavelength range of 0.4–2.5 μm, the average emissivity of the ZSC coating was 0.83 and the average reflectivity of the T@S coating was 0.63. With continuous heating at 1400 °C for 10 min with a butane torch, the temperature on the backside of the T@S–ZSC-coated AFF remained relatively stable at 225 °C, which is notably decreased by 80 °C compared to that of the single-layer ZSC-coated AFF. The tensile strength of AFF with T@S–ZSC coating reached 35 MPa after being heat treated at 1200 °C. Moreover, the bonding strength between the coating and the AFF substrate was measured to be 0.15 MPa. The double-layer coating with high emissivity and reflectivity, along with a flexible AFF substrate, offers a promising solution for addressing the challenging of surface heat-dissipation in hypersonic vehicles. [ABSTRACT FROM AUTHOR]

Integration of thermal insulation and electromagnetic wave absorption was crucial in stealth technology and hypersonic vehicles but challenging. Herein, silicon carbide nanofibers were synthesized by in situ chemical vapor deposition within a carbon foam skeleton to form a wave absorbing and heat insulating integrated composite aerogel with a hierarchical porous structure. The unique hierarchical porous structure provided an excellent platform for the absorption of electromagnetic waves, achieving a minimum reflection loss (RL min) of −51.46 dB at 17.20 GHz. Meanwhile, the C/SiC nanofiber aerogel maintained a low density of 0.013 g/cm3, an ultra-low thermal conductivity of 0.030 W/(m⋅K) and a high thermal stability up to 1000 °C. Furthermore, to enhance the electromagnetic wave (EMW) absorption property of the aerogel, polypyrrole (PPy) was coated on the surface of C/SiC nanofiber aerogel by facile impregnation and chemical polymerization. The multiple conductor-semiconductor-conductor structure of C/SiC-PPy composite aerogel leads to various EMW loss mechanisms and excellent impedance match, resulting in an outstanding EMW absorption performance, with a RL min of −60.31 dB at 2.96 GHz. [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]

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]

Ensuring a consistently high-strength connection in superalloy components of space shuttles from 25 to 1200 °C is essential yet challenging. To achieve the objective, we developed an adhesive using silicon-boron modified phenolic resin (Si-BPF) as the matrix and inorganic fillers as additives. The continuous Si– O –Si– O –B– O –B skeleton endowed the Si-BPF with excellent thermal stability. In addition, the inorganic fillers inhibited the thermal decomposition of Si-BPF. The generation of low-melting-point glass phases compensated for the defects in the adhesive. Therefore, within the "300–600 °C weak strength interval", the synergistic effect of Si-BPF and inorganic additives increased the adhesive strength to 17.26 MPa. The formation of intermetallic compounds and the ceramization of the adhesive resulted in a gradual increase in the bonding strength of the composite adhesive with increasing temperature, reaching 34.23 MPa after 1200 °C. The adhesive enabled high-strength bonding for superalloys throughout the wide temperature range, enhancing the application of superalloy components in space shuttles. [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]

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]

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]

Carbon fiber (CF) reinforced SiBCN composites were generally considered as key candidates for thermal protection under severe aerodynamic heating in aerospace due to their excellent high-temperature properties, but they were also faced with challenges in stably monitoring the structural integrity of themselves under extreme conditions. Herein, with the introduction of SiC coating, multifunctional CF-SiC/SiBCN composites were fabricated which integrated functions of the thermal protection and the structural health monitoring. Compared to the untreated CF/SiBCN composites, the stability of sensing of CF-SiC/SiBCN composites was greatly improved and the sensitivity of CF-SiC/SiBCN composites maintained at a high level with a gauge factor of 652.65. Furthermore, additional researches revealed that the CF-SiC/SiBCN composites enjoyed a high compressive strength (155.33 MPa), a light weight (1.07–1.61 g/cm3), and a relatively low thermal conductivity (4.02 W/(m·K)), which showed a potentiality of CF-SiC/SiBCN composites to be applied as multifunctional structural components in thermal protection systems. [ABSTRACT FROM AUTHOR]

The mechanical behaviors of single mullite fiber and binder/mullite fiber interface were experimentally investigated. The growth of the mullite grains of the fiber with the increasing calcination temperature greatly affected the tensile and compression strengths of the mullite fibers. As the calcination temperature went up from 1000 °C to 1500 °C, the average tensile strength decreased from 0.954 GPa to 0.191 GPa, and the Weibull modulus decreased from 5.1 to 1.8. The compressive strength was 50–60% of the average tensile strength under the same calcination temperature. The bonding strength of the binder/fiber interface increased with the increase of the calcination temperature. The mechanical properties and fracture mechanism of the mullite fiber-based porous ceramics with different binder contents were comprehensively analyzed based on the mechanical behavior of the single mullite fiber and the binder/fiber interface. [ABSTRACT FROM AUTHOR]

To prepare a coating with a high emissivity and low solar absorption ratio on the surface of aluminum silicate fiber cloth, the sol-gel method was used with silica sol as a binder. In this study, the effects of two white fillers, titanium oxide and zirconia, on the substrate and radiation properties of coatings were compared after heat treatment at 800–1200 °C. The ZrO 2 -based coating had good stability after heat treatment at 800–1200 °C, and maintained its white color, exhibiting solar absorption ratio of approximately 0.14 and emissivity of 0.84. ZrO 2 -based coatings prevented harmful cracking, as observed for the TiO 2 -based coatings after heat treatment, because of the ZrO 2 phase transformation. The ZrO 2 -based coating did not have strong bonding with the substrate, and the substrate strength was improved by maintaining a weak bonding interface. Compared with the TiO 2 -based coatings, which exhibit reduced substrate strength above 1000 °C, the ZrO 2 -based coating was more suitable for the surface of flexible fiber cloths as a temperature-resistant coating with good development prospects. [ABSTRACT FROM AUTHOR]

To improve the oxidation inhibition of TaSi 2 -based high-emissivity coatings at high temperatures, TaSi 2 –SiC coating modified by SiB 6 was prepared on the surface of alumina fibre fabrics. The effects of the SiB 6 content on the surface appearance and emissivity of the coating were investigated, and the mechanical properties of the coated fabrics were compared. When the SiB 6 content in the coating was 2.5%, the borosilicate glass liquid phase generated by SiB 6 oxidation effectively prevented the oxidation of TaSi 2. The bond strength between the coatings and fibre fabric was 207 kPa after calcination at 1200 °C, which was 39% higher than that of the coated fabric without SiB 6. The emissivity of the TaSi 2 –SiC coating, modified by a SiB 6 content of 2.5%, reached above 0.92 after calcination at 1200 °C for 5 h. Therefore, the TaSi 2 –SiC high-emissivity coating modified by SiB 6 has good application prospects in the field of thermal protection. [ABSTRACT FROM AUTHOR]

Porous alumina ceramics with inter-locked plate-like structure were successfully fabricated by the tert -butyl alcohol-based gel-casting method. The effects of Al/Si mole ratio on the structure and properties of the obtained products were investigated. The formation process of the inter-locked structure was analyzed. The products fabricated with the one-step method, in which the growth of plate-like alumina and the formation of the inter-locked structure were combined together, exhibited a high porosity of 76.21%, a compressive strength of 0.525 MPa and a low thermal conductivity of 0.495 W/mK, while the products fabricated by the two-step method after sintered at 1500 °C using the grinded powders after 700 °C heat-treatment as the starting materials possessed a relatively high compressive strength of 4.80 MPa. The obtained porous alumina ceramics were promising flexible insulant materials for the application in high-temperature field. [ABSTRACT FROM AUTHOR]

Mullite fibrous ceramics with different types of binders (silica particles, SiO 2 -B 2 O 3 mixture and silicon particles) were successfully fabricated by a TBA-based gel-casting. The influence of the above three types of binder on the microstructure and properties of the ceramics were investigated. The results show the resource of the binders played an important role in tailoring the inner structure of the ceramics, consequently influencing the product properties. All products showed high porosity, low density and low thermal conductivity, attributed to the special 3D fibrous skeleton structure. The products with silica as binder sintered at 1500 °C exhibited relatively low compressive strength because of the high melting point of the silica particles. On the contrary, the products with silicon and SiO 2 -B 2 O 3 as the binder sintered at 1500 °C showed higher compressive strength owing to the low viscosity of the binders during the sintering process. Compared with the products SiO 2 -B 2 O 3 as the binder, the products with silicon as the binder was more suitable for being used in the high-temperature environment (above 1500 °C), since the silicon could transform into the silica phase with high melting point. Besides, with the increase of the silicon content, the compressive strength and the thermal conductivity of the products increased gradually. [ABSTRACT FROM AUTHOR]

In order to maintain the strength of flexible substrate while applying the oxidation resistance dense glass coating, a scale structure coating on aluminum silicate fiber cloth was prepared with fused silica powder and silica sol as the binder and MoSi 2 as the emissive agent. The scale structure of the coating with large cracks along the braided grain and small random cracks on the fiber bundles allowed the fiber cloth to retain its flexible properties. Due to the block effect of dense SiO 2 glass phase on oxygen diffusion, the mass loss was only 0.35% after oxidation at 800 °C for 24 h while the average normal emissivity (2–14 μm) remained about 0.88. The MoSi 2 -silicon glass coating could avoid the generation of excessively strong interface with the substrate and improve the tensile strength of the sample to 140.52 MPa. [ABSTRACT FROM AUTHOR]

As a critical structure of thermal protection systems, flexible fibre insulation felts are widely used on the leeward surface of spacecrafts. To enhance the thermal resistance of flexible fibre felts, SiC w -ZrO 2 coatings with different SiC whisker (SiC w) contents were fabricated on the surface of a high-silica-fibre fabric (HSFF) by employing a sol-gel method combined with a spraying route. The introduction of SiC w having a length of 10–50 μm effectively improved the coating integrity. After calcination at 1000 °C for 1 h, the SiC w -ZrO 2 coating containing 8 wt% SiC w did not damage the tensile strength and flexibility of the fibre fabric, and the interfacial bonding strength between the coating and HSFF reached 0.40 MPa, benefitting from the whisker toughening mechanism. The SiC w -ZrO 2 coating with a high emissivity of 0.96 in the 2–14 μm wavelength range reduced the surface temperature of the flexible insulation felt by approximately 300 °C when a butane torch was applied at above 1300 °C. [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]

A temperature resistance buoyancy material was fabricated through a tert-butyl alcohol gelcasting process with borosilicate glass (BG) and hollow glass microspheres (HGMs) as the matrix and filler, respectively. The effects of the mass ratio of HGMs to BG and sintering temperature on the microstructure, thermal conductivity, and mechanical properties of the composite were studied. The results show that HGMs were bonded together by the BG, and the sample sintered at 750 °C exhibited a broad pore size distribution, from several microns to more than one hundred microns. The thermal conductivity experimental values of all the samples were less than that of Hashin-Shtrikman upper bound (HS + ) prediction but agreed well with that predicted from effective medium percolation theory. The relationship between compressive strength and relative density was predicted by the Gibson-Ashby model, with the calibration factor phi below 0.7. Young′s modulus values obtained from the experiment were below that of HS + prediction. The modulus values of the four types of samples sintered at 650 °C agreed well with the Pabst model prediction, while the values of the samples sintered at 700 °C and 750 °C were distributed in a zone between Ashby-Gibson model and HS + prediction. [ABSTRACT FROM AUTHOR]

Heat-resistant syntactic foams with relative high compressive strength, elastic modulus and low density were successfully fabricated through binding hollow glass microsphere by phosphate adhesive. The effects of additive B 4 C on the mechanical behavior of syntactic foams were investigated. The bulk density, compressive strength and elastic modulus of the syntactic foams could be tailored by varying the content of additive and the sintering schedule. The results revealed that the additive B 4 C was useful in regulating the mechanical behavior of the syntactic foams due to the volume compensation from B 4 C's oxidation and the formation of glassy state B 2 O 3 , which promoted the bonding of hollow glass microspheres. The compressive strength, bulk density, and elastic modulus of the syntactic foams were 10.80–20.38 MPa, 0.525–1.198 g/cm 3 and 0.81–1.23 GPa, respectively, when the samples containing 5–15 wt.% B 4 C sintered at 700–900 °C for 2 h. Therefore, the heat-resistant syntactic foams possess the potential application in aerospace, aviation and oil exploitation. [ABSTRACT FROM AUTHOR]

Ceramics are hard and brittle due to the complex crystalline structure, and the plastic deformation in amorphous oxides at moderate temperature may provide new ideas for achieving plasticity in ceramic materials. In this article, deformations in bulk amorphous Al 2 O 3 –ZrO 2 –Y 2 O 3 precipitated with different amounts of nanocrystallite were investigated under moderate temperature compression. Almost no plastic deformation occurred in fully amorphous AZY at 500 °C; however, a large plastic strain of 10.5% was achieved in sample with 3.65 mol% nanocrystallite, and the plasticity degraded as the crystallinity increased to 24.80 mol%. Plasticity enhanced by nanocrystallite in bulk amorphous oxides was achieved at temperature as low as 500 °C, and the deformation exhibited an unusual behavior of brittle-plastic-brittle transition with increasing crystallinity. The plastic strain was mainly resulted from shear banding along with further densification, and shear banding was confirmed as the dominating mechanism. Shear banding as well as the brittle-plastic-brittle transition was explained in terms of free volume theory. This work might provide a profound understand of plastic deformation and shear banding in bulk amorphous oxides, and inspire new methods to improve plasticity in amorphous materials. [ABSTRACT FROM AUTHOR]

A novel mullite fibers-based hierarchical heterostructure were fabricated using a sol–gel method. The porous performs were fabricated by mixing the mullite fibers with the aluminum borate xerogel which is derived from the gelation of Al(OC 4 H 9 ) 3 and boric acid. After calcination, the preforms with different mole ratio of Al/B, transformed into the composites with hierarchical structures of the aluminum borate nanowhiskers/mullite fiber and alumina plate/aluminum borate nanowhiskers/mullite fiber. The formed aluminum borate nanowhiskers showed a uniform distribution on the mullite fibers, and the growth process may follow a self-catalysis mechanism. The fabricated hierarchical mullite fiber-based products possessed low density of 0.448 g/cm 3 , low thermal conductivity of 0.132 W/mK, high specific surface area of 230.7 m 2 /g and excellent elastic property with high compression-resilience of 92.7%, and were promising flexible insulant materials for the application in high-temperature heat sealing field. [ABSTRACT FROM AUTHOR]

Porous alumina microspheres have attracted significant attention owing to their high mechanical strength and excellent chemical and thermal stability. The emulsion method is considered as a simple and controllable method for the preparation of inorganic microspheres. However, preparing alumina microspheres with the emulsion method is challenging because the emulsification of the precursor is inhibited by the rapid hydrolysis of aluminum alkoxide. Herein, we report a new emulsion method for the preparation of high-porosity alumina microspheres using a combination of ionic and non-ionic surfactants; in this method, the compound surfactants act as a template agent to guide aluminum alkoxide to form a lamellar structure through self-assembly. The decomposition of the templating agent and transformation of the alumina crystal at a high temperature result in structural collapse and formation of lamellar pores. Compound surfactants increased the spheroidization rate of the emulsion from 47% to 63% after hydrolysis, whereas the particle size was decreased by almost half. Additionally, the morphology and porosity of the alumina microspheres were changed. With increasing anionic surfactant content, the porosity increased initially and then decreased. The porosity of the alumina microspheres reached a maximum value of 76% at the 1:1 mass ratio of the non-ionic to anionic surfactants. Heat treatment was found to change the size of lamellar pores, with the pore diameter reaching maximum value at 1300 °C. The compound surfactants also increased the compressive stress and specific surface area of the porous alumina microspheres. [ABSTRACT FROM AUTHOR]

Aluminum silicate fiber fabric (ASFF) has been widely used in the outer surface of flexible insulation felt on the leeward side of aerospace vehicle. In order to improve the temperature resistance of ASFF, a kind of SiC–ZrC composite coating was prepared on the surface of fiber fabric via spraying method with SiC as emittance agent and ZrC as additive. The surface morphology and mechanical properties of the coating were studied. Compared with the single-component SiC coating, the composite coating could effectively avoid coating spalling and improve the surface integrity at high temperature. After thermal treatment at 1100 °C for 2 h, the interface bond strength of the composite coating/substrate was 52.41% higher than that of SiC coating/substrate. The tensile strength of fiber fabric with SiC–ZrC composite coating could reach 91.75 MPa, which was 101.76% higher than that of raw ASFF. Therefore, the SiC–ZrC coating could greatly improve the temperature resistance of ASFF, and has an attractive application prospect in the field of thermal protection system. [ABSTRACT FROM AUTHOR]

To satisfy the ever-increasing demand for aluminum borate porous ceramics with complex shapes and tunable pore structures in a diverse set of fields, aluminum borate whisker-based lattices with hierarchical pore structures were fabricated by a combination of in situ reaction and digital light processing three-dimensional (3D) printing. The optimal dispersant concentration and exposure parameters for 3D printing were determined based on analyses of the rheological properties and working curves of the Al 2 O 3 –B 2 O 3 photosensitive slurries. The effects of the B 2 O 3 /Al 2 O 3 molar ratio on the morphology and properties of aluminum borate lattices were investigated. The results showed that the addition of an excess of B 2 O 3 was beneficial to the growth of aluminum borate whiskers. When the B 2 O 3 /Al 2 O 3 molar ratio was set to 6:9, the resultant aluminum borate lattices exhibited a typical hierarchical pore structure, including inherent large pores in the lattices and small pores formed by interlocked aluminum borate whiskers generated in situ within the struts. This unique hierarchical pore structure endowed the ceramic lattices with a high compressive strength (1.18 MPa) and porosity (82.58%), as well as non-brittle fracture characteristics. Owing to these outstanding properties, aluminum borate whisker-based lattices are promising candidates for high-temperature thermal insulation, catalyst supports, acoustic absorption, and particle filtration. [ABSTRACT FROM AUTHOR]

Porous Al 2 TiO 5 ceramics have drawn increasing attention in diverse applications owing to their low thermal expansion coefficient, and good resistance to thermal shock; however, Al 2 TiO 5 ceramics prepared in previous studies still exhibited a relatively high density, which limited their further application in the field of high-temperature thermal insulation. Herein, we reported the successful fabrication of hierarchically porous Al 2 TiO 5 ceramics with a unique three-dimensional skeleton structure formed by overlapped ceramic nanofibers. Results show that the introduction of SiO 2 into Al 2 TiO 5 nanofibers could significantly improve their thermal stability and meanwhile reduce their formation temperature. Al 2 TiO 5 nanofibers with 10 mol% SiO 2 exhibited a superior microstructure and excellent thermal stability, and were selected as the raw material in the subsequent preparation of corresponding porous ceramics. Porous Al 2 TiO 5 ceramics prepared by the freeze-gel casting exhibited a unique hierarchical pore structure with large pores originating from the sublimation of ice crystal and small pores formed by the overlapped of fibers. This unique microstructure endowed porous ceramics with an ultra-high porosity (97.59–95.59%), ultra-low thermal conductivity (0.0456–0.0754 W m−1 K−1) and excellent thermal stability. Owing to these outstanding characteristics, the resulting porous Al 2 TiO 5 ceramics are expected to be employed as the high-temperature thermal insulation material in a wide spectrum of advanced applications. [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 recent years, the need for robust thermal protection for reusable spacecraft and vehicles has spurred strong demand for high-performance lightweight thermal insulation materials that exhibit high strength. Herein, we report silica porous ceramics prepared via the direct foaming technique with lightweight, ultra-low thermal conductivity and enhanced compressive strength. Silica particles (particle size: 500 nm and 2 μm) were used as the raw materials. The nano-sized silica particles were easily sintered, thereby improving the compressive strength of the ceramics, whereas the micro-sized silica particles maintained the pore structure integrity without deformation. The addition of nano-silica enhanced the compressive strength by 764% (from 0.039 to 0.337 MPa). In addition, the thermal conductivity of the ceramics was as low as 0.039 W m−1 K−1. Owing to these outstanding characteristics, these porous silica ceramics are expected to be employed as thermal insulation material in diverse fields, especially aerospace and space where weight is an important constraint. [ABSTRACT FROM AUTHOR]

Abstract: In this article, we described an unusual plastic deformation of Al2O3–ZrO2 ceramics under uniaxial compression at 500°C with constant engineering strain rate of 3.5×10−3 s−1. The Al2O3–ZrO2 ceramics displayed different deformations from either the traditional ceramics or the amorphous material. The Al2O3–ZrO2 ceramics started to yield at about 1.5GPa. A large elastic strain of about 27% had been achieved when the material began to yield. The elastic deformation transited to yield smoothly without any evident peak stress. The compressive stress continuously increased to about 2.2GPa before unloading. This unusual deformation might be related to the porous structure of the sample and coexistence of the amorphous phases and crystalline phases. [Copyright &y& Elsevier]

Abstract: Silica ceramic foams with controllable microstructure were produced by direct foaming method. The silica foams were prepared through three different systems: individual cationic surfactant stabilized system, individual anionic surfactant stabilized system, and the mixed cationic/anionic surfactant stabilized system. The foaming ability and foam stability of the three systems were investigated and the related mechanisms were discussed. The results showed that the mixed system had both long-term stability and good foaming ability compared with the others. In addition, the role of the anionic surfactant (SDS) on microstructure of the ceramic foams was studied. The results showed that the foam structure changed from closed pores to open pores with the increasing concentration of SDS. [Copyright &y& Elsevier]

Abstract: Porous silica ceramics with relatively high strength and novel bi-modal pore structure can be successfully fabricated via a facile tert-butyl alcohol-based gel-casting process by use of silica extracted from coal fly ash. Based on the evaporating of tert-butyl alcohol (TBA) during the drying process, the microstructure with bi-modal pores was obtained. By setting the solid loading (15wt.%) and changing the sintering temperature from 1050 to 1150°C, the porosity of the porous silica ceramics varied within the range of 70.1% and 72.4%, as the bulk density varied from 0.59 to 0.67g/cm3 and small pore sizes from 3.31 to 2.89nm. The compressive strength of sintered silica ceramics increased from 4.38MPa to 5.82MPa, which was attributed to the 3D-framework structure and the connection of silica particles. [Copyright &y& Elsevier]