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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]

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]

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]

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]

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: 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: Self-reinforced porous mullite ceramics were fabricated by a starch consolidation method with flyash, different aluminium sources (Al(OH)3 and Al2O3) and the additive AlF3 as raw materials. The reinforcement mechanism of needle-like mullite whiskers through in situ synthesis in ceramic body was investigated. The bulk density, apparent porosity and bending strength of the samples were tested. Phase compositions and microstructures of the sintered samples were measured by XRD and SEM, respectively. It showed that AlF3 as additive was helpful to the formation of mullite whiskers at a low temperature. As the aluminium sources, Al(OH)3 was more suitable for the preparation of mullite whiskers than Al2O3. The in situ synthesized mullite whiskers formed an interlocking structure, which enhanced the mechanical strength of the porous mullite ceramics. Porous mullite ceramics with bending strength of about 100MPa and apparent porosity of about 55% were made at 1550°C. [Copyright &y& Elsevier]

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]

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]

A temperature resistant buoyant material, namely, fly ash cenospheres-hollow glass microspheres/borosilicate glass (FACs-HGMs/BG) for high temperature application, was prepared through a tert-butyl alcohol-based gelcasting process, with FACs and HGMs as the fillers and BG as the matrix, respectively. The effect of FACs addition on the mechanical and high-temperature performance of the FACs-HGMs/BG composites was studied. The composites containing different amounts of FACs displayed low density (0.44–0.89 g/cm 3 ), low Young's modulus (0.05–1.10 GPa), and relatively high compressive strength (2.78–9.75 MPa). Three stages, namely, elastic, plateau, and fracture stages, could be observed in the stress-strain curves. The compressive strength of the samples at high temperature was lower than the ones at room temperature, and the 10%FACs-HGMs/BG composite tested at 500 °C displayed a compressive strength of 6.03 MPa. The FACs-HGMs/BG composites demonstrating excellent mechanical properties both at room and high temperatures may be used as promising candidates for structural materials or temperature resistant buoyant materials in the near future. [ABSTRACT FROM AUTHOR]

In this work, Al 2 O 3 -ZrO 2 (Y 2 O 3 ) nanoceramics were prepared via pressureless sintering of powders with different degrees of crystallinity. It was demonstrated that, the crystallization of amorphous phase in starting powders highly enhanced the densification during sintering. When the crystal content was 25 vol%, the powders exhibited better sinterability than other powders, and they could be sintered into bulk nanoceramics with relative densities higher than 98% at 1400 °C and 1500 °C. The superior sinterability of C25 powders was due to the crystallization of amorphous phase promoted by the as-existed nanocrystalline powders as nucleation seeds. The obtained nanoceramic exhibited homogenously distributed ZrO 2 and Al 2 O 3 particles with grain size of about 450 nm, and displayed excellent mechanical property with Vickers hardness of 15.3 GPa, fracture toughness of 5.2 MPa m 1/2 , and flexure strength of 1190 MPa. This work may provide new guidance for optimization in preparing bulk nanoceramics by managing the crystallinity of starting powders. [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]

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]

Abstract: Porous silica ceramics with relatively high mechanical strength can be successfully fabricated via a novel tert-butyl alcohol-based gel-casting method. The microstructure similar to stone arch bridges and the sintering neck can be easily observed due to the evaporation of tert-butyl alcohol (TBA) during the drying process. The porosity of samples with different solid loading sintered at 1150°C varied within the range of 56.4% and 70.1%, as the bulk density from 0.67 to 1.04g/cm3. The compressive strength of sintered silica ceramics increased from 4.32MPa to 8.82MPa, which was attributed to the 3D-framework structure and the connection of silica particles. By setting the solid loading (15wt.%) and changing the sintering temperature from 1050 to 1200°C, the porosity of the sintered samples varied within the range of 51% and 72.4%, as the bulk density remarkably varied from 0.59 to 1.18g/cm3 and pore sizes from 3.31 to 2.89nm. [Copyright &y& Elsevier]

Abstract: Sub-micron porous yttria-stabilized zirconia (ZrO2–5mol% Y2O3, YSZ) ceramics with ultra low density were successfully fabricated by a novel tert-butyl alcohol (TBA)-based gel-casting method. In this work, polymerization of acrylamide was realized in tert-butyl alcohol (TBA)/ZrO2 slurries with solid loading ranging from 10 to 30wt.%. Green bodies with ultra-low density (from 1.18 to 1.65g/cm3) could be dried with very small shrinkage (from 0.36% to 0.10%), and relatively high bending strengths (from 26.26 to 112.92MPa) were achieved. By choosing different initial solid loadings, the green bodies were sintered at different temperatures and subsequently characterized in terms of both microstructure and properties to study effects of solid loading and sintering temperature. Both microstructure and properties exhibited obvious dependence on solid loading. By setting the solid loading (20wt.%) and changing the sintering temperature from 1350 to 1500°C, the porosity of the sintered samples varied within the range of 69.9% and 54.1%, as the linear shrinkage varied from 15.8% to 25.2% and pore sizes from 0.58 to 0.44μm. Due to the neck formation between particles, there were also some smaller pores around 1.7 and 3.0nm. But the most important characteristics of the porous structure were the uniformity and the interconnection of pores with sizes about 0.5μm. [Copyright &y& Elsevier]