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To enhance the oxidation resistance of C/SiC composites, HfSiO 4 was introduced into C/SiC composites to modify the matrix utilizing two cyclic alternating preparation modes, thereby yielding the C/SiC-HfSiO 4 composites with a composite matrix. Using X-ray diffraction (XRD), field emission scanning electron microscope (FE-SEM), energy-dispersive spectrometer (EDS), and thermogravimetric-differential thermal analysis (TG-DTA), a comprehensive investigation was conducted into the oxidation behavior and mechanism of the prepared composites. Results reveal that the C/SiC-HfSiO 4 composites prepared using cyclic alternating preparation modes display the reduced oxidation mass loss and enhanced retention of flexural strength, despite of having higher porosity. In short, the introducing of HfSiO 4 can effectively improve the oxidation resistance of C/SiC composites. The effects of the matrix particle refinement and the synergy between the HfSiO 4 and SiO 2 jointly lead to the enhanced oxidation resistance. [ABSTRACT FROM AUTHOR]

Alumina ceramic samples with complex structures were prepared using a self-made down-mounted surface exposure forming system with a scraping mechanism and a ceramic slurry with an oxygen polymerization effect. A high-solid-phase, low-viscosity alumina slurry (1.55 Pa s viscosity at a 30 s−1 shear rate at 55 vol%) was developed. The effects of exposure time and oxygen pressure on the curing thickness and contour accuracy before and after oxygen permeability were studied. Under the optimal oxygen pressure (0.4 kPa), oxygen generation could effectively reduce the error caused by the scattering of the ceramic powder, improve the contour accuracy of the inner hole, and reduce the size error of the inner hole by 7.2 % compared with the unoxygenated generation. According to the application requirements of aluminum-based ceramic parts, the corresponding degreasing and sintering curves were formulated, and the closed porosity of the ceramic (>40 μm) after sintering was 1.18 %, relative density was 69.3 %, apparent porosity was 29.3 %, and flexural strength was 41.53 MPa. This presents new potential technical avenues for the preparation of ceramic parts with complex structures. • A high-solid content low-viscosity slurry with excellent performance was obtained. • The profile error caused by the scattering of ceramic powder can be effectively reduced and the profile accuracy of the inner hole can be improved by using the oxygen inhibition effect. • The 3D printing products with good mechanical properties and high forming accuracy were prepared by using the self-developed printer. [ABSTRACT FROM AUTHOR]

The ZnO–Al 2 O 3 –B 2 O 3 –SiO 2 (ZABS) glass powder was designed and innovatively employed to join AlN ceramics. The crystallization, thermal expansion and wettability behavior of the ZABS glass and glass-ceramic were investigated. The results shows that Zn 3 B 2 O 6 , ZnSiO 4 and Zn 4 B 6 O 13 were precipitated after heat treatments at different temperature, respectively, resulting in a variation in the coefficient of thermal expansion (CTE) of the ZABS glass ceramic. Then guided by the wetting behavior on the AlN ceramic substrate, the joining of the AlN ceramics by ZABS glass at various temperatures and holding times were conducted. Notably, Zn 3 B 2 O 6 was identified to be the primary product in the joints bonded at temperature of 700–800 °C due to the crystallization within the glass and no discernible reaction was observed between the substrate and the interlayer, while ZnSiO 4 was observed at the periphery of Zn 3 B 2 O 6 after 750 °C. Moreover, the crystalline phase Zn 3 B 2 O 6 gradually grew with the temperature and holding time increasing as the glassy phase gradually diminished, resulting in a reduction of the strength and reliability of the joints. The optimal flexural strength of the joints was 156 ± 11 MPa at 700 °C for 30min. The reason for the high strength can be attributed to the interactions between the glass precipitated crystalline phase interlocking each other and the glass phase tightly bonded with the crystalline phase. [ABSTRACT FROM AUTHOR]

The TiB 2 -TiN-HEA cermet materials were synthesized in-situ reaction hot-pressing sintering at 1450 °C for 1 h, utilizing Ti, BN, and Al 0.3 CoCrFeNi high entropy alloys (HEA) as starting materials. The thermodynamic characteristics of the reaction system and the phase structure, microstructure, and mechanical properties of Ti-BN, Ti-HEA, BN-HEA, and Ti-BN-HEA were investigated. The results demonstrate that in-situ reaction hot pressing sintering phases include TiN, TiB 2 , and FCC structural. The synthesis of TiB 2 involves the diffusion of B to TiB and the subsequent combination of Ti and B in solution. Conversely, the formation of TiN consists of the diffusion of N to TiN 0.3 and Ti 2 N, as well as the subsequent combination of Ti and N in solution. The TiB 2 -TiN-HEA cermet exhibits a relative density of 99.1%, Vickers hardness of 18.91 GPa, flexural strength of 721 MPa, and fracture toughness of 7.61 MPa m1/2. The high strength of cermet was due to a combination of factors, including the synergistic effect of high compactness of composites, reinforced interfacial strength with HEA, reinforcement of fine-grains and TiB 2 rod-like grains, crack bridging and deflection, and transgranular fracture. [ABSTRACT FROM AUTHOR]

Additive manufacturing of ceramics has attracted large interest due to its unique ability to rapidly prototype, low cost, and increased geometric complexity. Material extrusion technique is often considered for processing and shaping fine and dense ceramic structures because of the high solid loading in ink. In this work, 8 mol.% yttria-stabilized zirconia ink with 70 wt% ceramic loadings was prepared to print zirconia samples in horizontal and vertical directions, following two different filament orientations: 0/90° and ±45°. The study's main objective was to evaluate printing design influences on mechanical properties. This was assessed through flexural testing and digital image correlation analysis. Experimental findings showed that samples printed horizontally with ±45° filament orientation displayed the highest strength. A detailed inspection of fracture surfaces revealed that printing defects were the critical failure location sites formed after sintering and intimately related to printing design issues. After that, a conductive sensor was integrated into the surfaces of 3D-printed specimens by screen-printing silver-based conductive ink to analyze the structural health of zirconia samples. The sensing capabilities of printed conductive patterns were investigated using the four-point bending tests. The results demonstrated that the electrical resistance of the printed silver patterns increased as the applied load on zirconia substrates rose. It indicates that hybrid material extrusion and screen printing techniques are favored ways to manufacture sensors for structural detection of advanced 3D-printed ceramics. [ABSTRACT FROM AUTHOR]

Bipolar plates (BPs) are vital components in Proton Exchange Membrane Fuel Cells (PEMFCs), and their performance and cost significantly impact fuel cell stack efficiency and affordability. BPs require excellent conductivity, strength, and corrosion resistance depending on usage conditions. Common graphite and metal-based BPs offer good conductivity, but they have their drawbacks. Graphite lacks strength and is costly to process, while metal-based BPs need additional surface treatments to prevent corrosion. In recent years, composite bipolar plates have gained widespread attention due to their excellent conductivity, mechanical properties, and outstanding corrosion resistance. In this study, we used natural graphite flakes as the main conductive filler and nano-copper as the secondary conductive filler, with epoxy resin as the binder. The composite bipolar plate was prepared using a hot-pressing method. The study found that adding 1 wt% of nmCu can increase the conductivity of the composite BP by 75.2%, but it decreases the flexural strength by 26.84%. The prepared nmCu/G/EP composite BP exhibits an ASR of only 4.00 mΩ cm2 and a corrosion current density of 2.615 × 10−7 A/cm2, meeting the DOE 2025 expectations. After conducting Cu2+ leaching experiments on the prepared composite BP, single-cell performance testing showed a maximum power density of 0.556 W/cm2. This study expands the range of conductive fillers for composite BPs, no longer limited to carbon-based conductive fillers. • Prepared outstanding EP/G/Nano copper BPs with superior performance through hot-press molding. • The electrical conductivity of the prepared EP/G/Nano copper BPs reached 168.1 S/cm, with a flexural strength of 46.0 MPa. • Adding 1% nano copper raised the composite BPs' electrical conductivity by 75%, yet caused a 30% drop in flexural strength. • The composite BPs with added nano copper, under a pressure of 1.6 MPa, exhibited an ASR of 4.00 mΩ cm2. [ABSTRACT FROM AUTHOR]

To determine whether water sorption and solubility of a recently introduced self-adhesive cement is comparable to two clinically tested resin composite cements after thermal aging, and if this is affected by the curing mode. Whether water sorption is correlated with color difference and biaxial flexural strength was also investigated. Water sorption and solubility of three resin composite cements {RelyX Universal (RUV), (Panavia V5 (PV5), Panavia SA plus (PSA)} were measured after thermal aging. Disk-shaped specimens were either light-cured or autopolymerized (n = 15 per group). Color difference ΔE 00 and biaxial flexural strength were also obtained. Sorption was highest for RUV (auto: 54.9 ± 9.0 µg/mm3, light: 49.7 ± 4.9 µg/mm3), followed by PSA (auto: 37.7 ± 1.4 µg/mm3, light: 34.5 ± 1.1 µg/mm3) and PV5 (auto: 21.7 ± 0.7 µg/mm3, light: 22.1 ± 0.4 µg/mm3). Light-curing reduced solubility values, particularly for RUV (from 60.7 ± 20.8 µg/mm3 to 6.4 ± 0.8 µg/mm3). Color differences of ΔE 00 > 1.8 (considered clinically not acceptable) were noted after aging for RUV and PSA. Sorption and ΔE 00 values after aging were correlated linearly (R2 = 0.970). Biaxial flexural strength values were highest for PV5 (light: 153.4 ± 15.9 MPa; auto: 133.2 ± 18.0 MPa) and lowest for RUV (light: 99.3 ± 12.8 MPa; auto: 35.1 ± 8.3 MPa). Light-curing has beneficial effects on sorption, color stability, and biaxial flexural strength of resin composite cements. Cements containing 2-hydroxymethacrylate such as RUV and PSA are more prone to water sorption and color changes. • Water sorption and solubility of three resin composite cements were evaluated. • Light-curing decreased water sorption and solubility and increased strength. • Water sorption was linearly correlated with color difference ΔE 00. • Water sorption was linearly correlated with strength depending on curing mode. [ABSTRACT FROM AUTHOR]

Silicon nitride-based bioceramics have been investigated for biomedical applications due to their good thermo-mechanical, tribological and antibacterial properties. However, biological properties, such as bioactivity that promotes the interaction with tissue, are also important. Silicon dioxide has been found to promote bioactivity. With the aim of combining both advantages, a new Si 3 N 4 -SiO 2 glass ceramic was developed. Three different compositions were synthesized and sintered by spark plasma sintering. The results showed that β-Si 3 N 4 crystalline is well distributed in the SiO 2 matrix. 70SiN samples exhibited the highest mechanical properties with a flexural strength of 452 ± 33 MPa and a toughness of 6.4 ± 0.5 MPa∙m1/2. 50SiN samples exhibited the best bacteriostatic effect due to the synergistic effect of surface chemistry and topography. Apatite was observed on the surfaces of all groups. This study shows that the newly developed Si 3 N 4 -SiO 2 glass ceramics exhibit promising mechanical and biological properties for biomedical applications. [ABSTRACT FROM AUTHOR]

Low strength and poor performance of SiC–WC composite for seals, attributable to the use of a large amount of liquid phase sintering additives, limit the application prospects of these materials. This study focuses on preparing high-strength, high-toughness, and wear-resistant SiC–WC composite using a small amount of aluminum and carbon black as sintering additives. The results revealed that the specimen containing 50 wt% WC exhibited the maximum flexural strength and fracture toughness of 645.9 MPa and 7.49 Mpa m1/2, respectively. These improvements were attributed to the deoxidizing and solid-solution effects of Al and the reinforcing effect of the WC second phase. Moreover, the specific wear rate was measured at 8.06 × 10−7 mm3 N−1 m−1, which was 56.9 % lower than that of monolithic SiC. Results from Raman spectral analysis provided evidence of the presence of W–O bonds on the wear surface, indicating that the SiO 2 film could be successfully replaced by a WO 3 film. [ABSTRACT FROM AUTHOR]

Different Hf/Zr-based UHTCs modified C/C composites were fabricated via the reactive melt infiltration (RMI) adopting HfSi 2 , ZrSi 2 , and HfSi 2 -ZrSi 2 hybrid alloys with different molar ratios (3:1, 1:1, 1:3). The microstructural evolution of the composites, variation of mechanical properties, and ablation performance of the composites in the absence of in-situ coating were studied. The C/HfC-ZrC-SiC composites were all divided into the exterior region with more UHTC phases and the interior region with more SiC and silicides, and the UHTC-rich region enlarged with the HfSi 2 content increased in the RMI alloy. The flexural strengths of C/HfC-ZrC-SiC were enhanced to 238.37 ± 20.42 Mpa and 237.26 ± 17.57 Mpa when adopting HfSi 2 -ZrSi 2 alloys with molar ratios of 1:1 and 1:3. As the HfSi 2 content in the RMI alloy increased, the oxide layer became compact with sintering degree increased, enhancing the ablation resistance of the composites and reducing the mass ablation rate. [ABSTRACT FROM AUTHOR]

Composite ceramics are applied widely nowadays by combining superior properties of different ceramic materials. In this study, SiO 2 –Si 3 N 4 composite ceramics with higher mechanical properties and lower dielectric constant were successfully fabricated by nitriding diamond-wire saw silicon waste. The effect of gas atmospheres (N 2 , NH 3 , N 2 –H 2) and SiO 2 content (0%, 10%, 20%, 30%, 40%) on the microstructure and properties of composite ceramics were studied. It shows that the synthesis of SiO 2 –Si 3 N 4 composite ceramics can be obtained in the NH 3 atmosphere, and it is inevitable to form the Si 2 N 2 O phase in N 2 and N 2 –H 2 mixture atmospheres. Furthermore, the shrinkage rate and dielectric constant of the ceramics decreased as SiO 2 content increased from 0% to 40%. As for the porosity of the sintered ceramics, it first decreased and then increased, with a minimum of 1.73% at the SiO 2 content of 20%. However, the flexural strength of the sintered ceramics was the inverse of the porosity, with a maximum of 160.72 MPa at the SiO 2 content of 30%. For the sintered ceramic with 30% SiO 2 , the shrinkage rate, dielectric constant, porosity and flexural strength are 0.3%, 4.62, 1.97% and 160.72 MPa respectively. Thus, this study provides an environment-friendly and value-added approach to recycling photovoltaic waste and reducing the cost of the reactive sintering SiO 2 –Si 3 N 4 composite ceramics with excellent mechanical and dielectric properties. [ABSTRACT FROM AUTHOR]

In this work, the influence of the aspect ratio of graphene-based nanostructures (GBNs) and content on the mechanical properties of 3 mol% yttria tetragonal zirconia polycrystalline 3Y-TZP matrix composites was analysed. The influence of the dispersion method and sintering parameters on the flexural strength and elastic modulus of the composites was studied, and the fracture surfaces were characterized to determine the fracture mechanisms that occur. The results showed that small amounts of exfoliated graphene nanoplatelets, with reduced lateral size, and few layer graphene, up to 1.0 and 2.5 vol%, respectively, slightly increase the 3Y-TZP flexural strength. This has been attributed to the tortuosity of the crack propagation pathways and strengthening mechanisms. Higher contents cause a decrease in flexural strength and stiffness because of overlapped GBNs, which can promote the crack propagation. The pull-out of GBN was more significant in composites with non-exfoliated graphene nanoplatelets, where no increase on the flexural or biaxial strength was measured. [ABSTRACT FROM AUTHOR]

The SiC nw /Al 2 O 3 composite powders synthesized through combustion synthesis method were added to the Al 2 O 3 –SiC refractory castables used in waste incinerators to improve their properties. The properties of Al 2 O 3 –SiC refractory castables with SiC nw /Al 2 O 3 composite powders (0–8 wt%) were evaluated which contained apparent porosity, bulk density, mechanical strength, high temperature wear resistance, hot modulus of rupture, thermal shock resistance and slag corrosion resistance. The results showed that various properties of the castables were enhanced with the addition of SiC nw /Al 2 O 3 composite powders. When 6 wt% composite powders were added, the hot modulus of rupture increased by 84.1% from 1.63 to 3.00 MPa, the high temperature wear volume decreased by 71.0% from 6.2 to 1.8 cm³, and the residual strength rate increased by 22.6% from 42.5% to 52.1%. Therefore, the properties of Al 2 O 3 –SiC castables were improved through the synergistic reinforcement effect of SiC nanowires and acicular mullite whiskers on the matrix. [ABSTRACT FROM AUTHOR]

In this study, La-doped BaZrO 3 -based composite ceramics Ba 1-x La x Zr 1-0.25x O 3 (x = 0–0.2) were successfully fabricated. The structure, phase composition, sintering behavior, and mechanical and thermal properties of the materials were investigated, and their thermodynamic stability was evaluated. The results revealed that the doping of La facilitated the formation of solid solution (Ba,La)ZrO 3 , and La 2 Zr 2 O 7 , leading to grain refinement and enhanced structural densification as well as grain boundary bonding of the samples. As La doping x ranging from 0 to 0.20, the average grain size of the specimens decreased from 6.14 μm to a minimum of 2.58 μm, the cold modulus of rupture increased significantly from 84.1 to 155.6 MPa. Moreover, the apparent porosity decreased from 11.2% to a minimum of 1.7% with a thermal conductivity gradually decreased from 5.501 W/mK to 2.802 W/mK. Additionally, thermodynamic calculations indicated the potential application of La-doped BaZrO 3 ceramics in the field of highly reactive alloy melting. [ABSTRACT FROM AUTHOR]

The applications of Si 3 N 4 ceramics are hindered by their brittleness and susceptibility to fracture, despite their high strength and wear resistance. To address this challenge, layered ceramics were prepared using lamination and plasma sintering techniques, inspired by the structure of shell pearl layers. The bio-inspired layered ceramics were alternately arranged with Si 3 N 4 as the matrix layer (hard) and BN as the interfacial layer (soft). During the study, ceramic specimens with different microstructures were obtained by modulating the layer thickness ratio (ratio of Si 3 N 4 to BN) and sintering temperature. The microstructure of the specimens was characterized using SEM (Scanning Electron Microscope) and EDS (Energy Dispersive Spectrometer). The mechanical of various specimens were assessed by measuring the flexural strength and fracture toughness. The results of the investigation revealed that the mechanical characteristics of the samples reached their optimum state (with a toughness of 13.51 ± 1.56 MPa m1/2 and a strength of 429 ± 4.28 MPa) when the ratio of Si 3 N 4 to BN was 5:1, and the sintering temperature was maintained at 2000 °C. [ABSTRACT FROM AUTHOR]

The development of additive manufacturing technique provides possibility to prepare SiC ceramics with complex shapes. However, defect control in the debinding and sintering stages is still a great challenge for the vat photopolymerized components. Here, SiC ceramics were manufactured by vat photopolymerization followed by liquid silicon infiltration, using SiC whiskers as the reinforcement. In the debinding stage, the SiC whiskers prevented the propagation of micro-cracks that induced by the formation and emission of gaseous substance. Also, the SiC whiskers provided channels for the infiltration of liquid silicon during sintering, thus the bulk density of the as-sintered SiC w /RBSC composite reached 2.95 g/cm3 at the whiskers fraction of 8 wt%. Because of the various toughening mechanisms introduced by SiC whisker, the flexural strength and Vickers hardness of the composite increased up to 352.2 MPa and 17.54 GPa, respectively. Thus, this work provides a new strategy to control micro-defects in vat photopolymerized SiC ceramics. [ABSTRACT FROM AUTHOR]

Owing to the harsh working condition, the ZrO 2 –C materials used in the slag line in the submerged entry nozzle are confronted with serious slag erosion. In order to solve this issue, different amounts of TiO 2 addition ranging from 0 to 6 wt% are added and their effects on the erosion resistance of ZrO 2 –C materials in addition to phase composition, microstructure, physical properties and high-temperature mechanical properties are investigated in this work. When the sintering temperature is above 1400 °C, fine TiC grains and SiC whiskers are in-situ formed and distributed around ZrO 2 particles, which can reinforce the matrix and improve the strength of ZrO 2 –C materials. With the amount of TiO 2 addition increasing, the cold strength of ZrO 2 –C materials increases while the high-temperature strength slightly decreases. Combining with the erosion resistance, the optimum amount of TiO 2 in ZrO 2 –C materials is determined to be 4 wt%, in which the cold compressive strength (46.13 MPa), the cold modulus of rupture (35.12 MPa) and the residual strength after thermal shock (15.01 MPa) reach the maximum. Based on this, the promotion mechanism of erosion resistance is further discussed with aid of molecular dynamics simulation. [ABSTRACT FROM AUTHOR]

In this study, the vat photopolymerization (VP) additive manufacture technique was employed to fabricate Si 3 N 4 ceramics implants. A photosensitive suspension with a high solid loading of 40 vol% and a low viscosity of 1.95 Pa•s at a shear rate of 30 s−1 was achieved by optimization of the composition. Particularly, as high as 50 vol% content of PPG was used in the photosensitive suspension, leading to a smooth printing and increased debinding efficiency with a heating rate up to 3 °C/min. The printed body was sintered at 1800 °C under 0.4 MPa nitrogen atmosphere, obtained the Si 3 N 4 ceramic with a relative density of 96.08%, a fracture toughness of 5.88 MPa m1/2, a flexural strength of 677 MPa and a Vickers hardness of 16.26 GPa. A cylindric Si 3 N 4 ceramic implant was made by the optimized suspension and printing parameters, and the implantation test in the histological section was conducted, showing a good biocompatibility after 6 weeks. [ABSTRACT FROM AUTHOR]

Porous Si 3 N 4 has excellent properties such as high temperature resistance, corrosion resistance, high porosity, and high specific surface area, but the inherent brittleness limits the application of Si 3 N 4 in some special environments. Si 3 N 4f /RBSN porous ceramic composites were prepared by reaction bonding method using reaction-bonded silicon nitride(RBSN) as the matrix and continuous Si 3 N 4 fibers (fiber mats) as the reinforcement. The results show that the composite with Si/Si 3 N 4 = 70:30 in the raw material has a superior nitridation rate and flexural strength of 96.5% and 23.5 MPa, respectively. The nitridation process of the Si 3 N 4f /RBSN matrix is dominated by the vapour-phase reaction between SiO and N 2 , and the products are mainly α-Si 3 N 4 whiskers. The residual flexural strength of the composites is essentially unchanged after 10 thermal cycles in air at 800 °C. The composites have excellent thermal shock resistance and can be used as the reusable crucible. [ABSTRACT FROM AUTHOR]

This study involved the synthesis of Si 3 N 4 ceramics, focusing on adjusting TiN content and sintering temperatures to enhance mechanical properties. Utilizing Density Functional Theory (DFT), we examined the microstructure and elastic properties of Ti-doped β-Si 3 N 4 , providing insights into how the Ti atom influences mechanical behavior. Additionally, a machine learning approach was applied to establish a predictive model for Si 3 N 4 fracture toughness, factoring in material composition and the sintering process. Remarkably, TiN incorporation led to a substantial increase in hardness, reaching 16.63 GPa. At 1800 °C, the resulting material at 10 wt% and 5 wt% TiN content exhibited impressive flexural strength (924 MPa) and fracture toughness (8.48 MPa m1/2). The theoretically calculated elastic properties confirmed the benefits of Ti atom doping in enhancing Si 3 N 4 ceramics. By employing the relu activation function in combination with the rmsprop optimizer, we achieved a coefficient of determination (R 2 ) for the test set no less than 0.824, ensuring reliable predictions for TiN–Si 3 N 4 fracture toughness. This study provides valuable guidance for swiftly predicting high-performance Si 3 N 4 ceramics and introduces a novel research avenue for the development of advanced materials. [ABSTRACT FROM AUTHOR]

SiC-based materials have been hot research topic in the field of high-temperature electromagnetic wave (EMW) absorption materials. SiC–Al 2 O 3 composite EMW absorption materials were prepared via casting process using carbon nanofibers/calcium aluminate cement (CNFs@CAC) as the binder. Effects of CNFs@CAC content on EMW absorption properties of SiC–Al 2 O 3 composites were investigated. Results show that the effective absorption bandwidth (EAB) of SiC–Al 2 O 3 composites first increases and then decreases with the increase in CNFs@CAC content. SiC–Al 2 O 3 composites with 10 wt% CNFs@CAC (denoted as F10) have excellent EMW absorption properties in X-band (8.2–12.4 GHz), with minimum reflection loss (RL) of −66.12 dB at a thickness of 2.1 mm and a wide EAB of 3.27 GHz. This is attributed to synergistic effects of the network of SiC nanowires generated with CNFs as templates during sintering process and irregular porosity of the structure, which results in SiC–Al 2 O 3 composites having good impedance matching and multiple EMW attenuation mechanisms. In addition, sample F10 exhibits exceptional mechanical properties and oxidation resistance, as indicated by its flexural strength of 25.6 MPa. After oxidation at temperatures in the range of 800 °C-1000 °C for 8 h, EAB of sample F10 is in the range of 3.15–3.30 GHz. Above results indicate that SiC–Al 2 O 3 composites are promising EMW absorption materials for use in harsh environments. [ABSTRACT FROM AUTHOR]

A novel method was proposed to prepare Ti(C,N)-based cermets with a cellular structure by controlling the drying conditions and subsequent vacuum sintering, the as-prepared cermets combine the advantages of fine grains with those of coarse grains, and show superior mechanical properties compared to conventional cermets. The microstructure, interface characteristics and mechanical properties of cellular cermets were systematically investigated. The SEM analysis revealed that cellular cermets comprised fine-grained aggregates and coarse-grained matrix; these aggregates were distributed in the matrix, which formed obvious interfaces between them. With increasing drying temperature and decreasing drying gas pressure, the volume fraction of aggregates in vacuum-sintered cermets first increased and then decreased. In addition, semi-coherent and coherent relationships were formed at the ceramic/binder phase boundaries in the aggregates and matrix, respectively, leading to the improvement of toughness. By optimizing the drying conditions, significant grain refinement was observed in the cellular cermets; these cermets exhibited excellent mechanical properties, i.e., hardness of 93.2 ± 0.1 HRA, transverse rupture strength of 2030 ± 32 MPa, and fracture toughness of 8.8 ± 0.1 MPa m1/2. The refinement of ceramic grains was found to be the dominant factor responsible for the increased hardness and strength, while the improvement of toughness was mainly due to the unique characteristics of the aggregates and matrix. [ABSTRACT FROM AUTHOR]

A method of Al 2 O 3 whiskers addition is provided to simultaneously enhance the forming accuracy, and mechanical and tribological performances of translucent glass-ceramics manufactured through vat photopolymerization 3D printing. Al 2 O 3 whiskers (0–15 wt%) were added to a self-prepared fluorapatite glass-ceramic as a raw material. The results demonstrated that the addition of Al 2 O 3 whiskers significantly improved the forming accuracy, mechanical and tribological performances of fluorapatite (FAp) glass-ceramics. The dimensional error of the formed samples decreased by approximately 56% with the addition of 15 wt% Al 2 O 3 whiskers. The glass-ceramics containing 10 wt% Al 2 O 3 whiskers exhibited a flexural strength and fracture toughness of 220.3 ± 13.7 MPa and 1.81 ± 0.18 MPa·m1/2, respectively, representing a 44.1% and 111.8% increase compared to pure FAp glass-ceramics. Furthermore, the addition of Al 2 O 3 whiskers led to reduced wear volume in both the glass-ceramics and titanium balls used as counterparts, indicating improved tribological compatibility. [ABSTRACT FROM AUTHOR]

Mullite-bonded SiC porous ceramics are of potential in hot gas infiltration while the insufficient mechanical performance limits its application. In-situ mullite whisker reinforcement is a potential solution but the formation temperature mismatch between mullite whisker and bonding layer is a challenge. In that case, mullite whiskers massively form ahead of the bonding layer excessively consuming alumina leading to poor bonding layers between SiC particles and thus, the mechanical performance. Herein, the mismatch was solved by using CaF 2 as a temperature-controlled reaction switch. As a result, both the bonding layer and whisker synchronously formed. The material showed significant reinforcement effects, and exhibited a flexural strength of 124.8 MPa and a fracture toughness of 1.53 MPa·m1/2 with an open porosity of 36.6 vol%, realizing a breakthrough in the mechanical performance. Interestingly, an increase in oxygen vacancy concentration with the sintering temperature was first reported, which may benefit the whisker growth. [ABSTRACT FROM AUTHOR]

An alumina rich Al 2 O 3 –ZrO 2 –TiO 2 compound was used for the preparation of self-supporting parts via the rod flame spraying technology. The as-sprayed material was compared to self-supporting parts, fabricated from commercially available alumina rods. For both materials, the flexural strength, the fracture resistance, and the behaviour under subcritical loading was evaluated and compared, either before as well as after cold thermal shock. While the flexural strength and the subcritical damaging of both materials were basically affected through thermal shock in a similar manner, the Al 2 O 3 –ZrO 2 –TiO 2 compound showed an outstanding behaviour in terms of its fracture resistance, which was only barely reduced after thermal shock quenching. [ABSTRACT FROM AUTHOR]

Lithium silicate-based glass ceramics have evolved as a paramount restorative material in restorative and prosthetic dentistry, exhibiting outstanding esthetic and mechanical performance. Along with subtractive machining techniques, this material class has conquered the market and satisfied the patients' needs for a long-lasting, excellent, and metal-free alternative for single tooth replacements and even smaller bridgework. Despite the popularity, not much is known about the material chemistry, microstructure and terminal behaviour. This article combines a set of own experimental data with extensive review of data from literature and other resources. Starting at manufacturer claims on unique selling propositions, properties, and microstructural features, the aim is to validate those claims, based on glass science. Deep knowledge is mandatory for understanding the microstructure evolution during the glass ceramic process. Fundamental glass characteristics have been addressed, leading to formation of time-temperature-transformation (TTT) diagrams, which are the basis for kinetic description of the glass ceramic process. Nucleation and crystallization kinetics are outlined in this contribution as well as analytical methods to describe the crystalline fraction and composition qualitatively and quantitatively. In relation to microstructure, the mechanical performance of lithium silicate-based glass ceramics has been investigated with focus on fracture strength versus fracture toughness as relevant clinical predictors. Fracture toughness has been found to be a stronger link to initially outlined manufacturer claims, and to more precisely match ISO recommendations for clinical indications. [ABSTRACT FROM AUTHOR]

Novel (Ti, W)C–SiC–WSi 2 ceramics were fabricated by in situ reaction spark plasma sintering (SPS) at 1600 °C using (Ti, W)C and Si powders. The effect of Si content on densification behavior, microstructures, and mechanical properties was investigated. The in situ reaction and the formation of carbon vacancies reduced the sintering temperature. The densification mechanism of (Ti, W)C-based ceramics transforms from reaction to grain-boundary sliding and diffusion. The WSi 2 and primary SiC generated by in situ reactions are distributed along the grain boundaries and have a specific crystallographic orientation relationship. Intragranular secondary SiC formed because of rapid densification, grain-boundary diffusion, and (Ti, W 1− y)C 1− x particle migration. This multiscale particle-reinforced microstructure can improve the mechanical properties of (Ti, W)C ceramics, giving the TW10S (4.80 wt% SiC–5.01 wt% WSi 2) good sintering performance, a fine-grained microstructure, high hardness (23.3 ± 1.6 GPa), and flexural strength (425 ± 24 MPa). The SiC and WSi 2 produced through in situ reactions have exceptional intrinsic oxidation resistance, allowing the ceramics to achieve outstanding oxidation resistance. [ABSTRACT FROM AUTHOR]

Si 3 N 4 ceramics, due to their exceptional comprehensive performance, have potential applications in electronic products under the 5th generation mobile communication technology. However, their development is hindered by a lack of color variety and inherent brittleness. To address these issues, we propose the use of an appropriate colorant-sintering additive to enhance densification, promote the growth of β grains and facilitate the formation of a chromogenic phase. This approach aims to simultaneously adjust the color and mechanical properties of Si 3 N 4 ceramics. STEM-EDS results indicate the presence of Re-enriched hollow structures within the Si 3 N 4 matrix. These hollow structures may serve as one of the color centers of silicon nitride. The combined effects of the stress field surrounding the hollow structure, elongated β-Si 3 N 4 grains and intensive dislocations result in strong mechanical properties of Si 3 N 4 ceramics, in which the flexural strength is 852.7 ± 55.8 MPa and the fracture toughness is 11.7 ± 1.0 MPa m1/2. [ABSTRACT FROM AUTHOR]

In this research endeavor, we report the successful synthesis of an aminosulfonic-based ceramic additive, HLDSA, was prepared by replacing part of phenol with HLDLP, a depolymerization product of hydrolysis lignin, through Co@C metal catalysts in the synergistic alkali-catalyzed depolymerization of hydrolysis lignin to achieve high-value lignin utilization. The preparation and application conditions of the depolymerized hydrolysis lignin HLDLP and its modified product HLDSA were studied, together with a brief analysis of their mechanism of action. During application of ceramic additive, the HLDSA showed a rather excellent dispersing and flexural strength performance, with a minimum slurry outflow time of 20.81 s and a maximum flexural strength of 2.79 MPa, which was a significant improvement over that of the blank sample (59.29 s and 1.77 MPa). Meanwhile, HLDSA was contrasted with other 8 ceramic additives that are widely available on the market. The application performance of HLDSA was also better than that other ceramic additives on the market, indicating that HLDSA has a promising application. • Depolymerized hydrolysis lignin (HLDLP) was produced from hydrolysis lignin (HL) for phenolic compound. • In the depolymerization products of HL, the selectivity of phenol and 2-methoxyphenol reached 33.69% and 23.50%, respectively. • HLDSA is a kind of lignin aminosulfonic-based ceramic additive with excellent properties prepared from HLDLP instead of partial phenol. • The grinding aid, dispersion and stability of HLDSA is superior to most ceramic additives on the market. [ABSTRACT FROM AUTHOR]

Porous Si 3 N 4 –SiC composites are potentially very attractive for various advanced applications such as aerospace and solar thermal power plants. However, processing of these porous composites is difficult and expensive due to the requirement of very high temperatures. In the present work, porous Si 3 N 4 –SiC composites were fabricated at only 1200 °C using phosphoric acid both as a pore former and binder. Porous composites with a constant SiC content were fabricated using various H 3 PO 4 content and the morphology and mechanical properties of the porous composites were systematically investigated. The addition of SiC particles resulted in significant improvement of stiffness, compressive strength, and flexural strength over monolithic porous Si 3 N 4 , and porous composites fabricated using 40 vol% H 3 PO 4 yielded the best properties of longitudinal elastic constant >50 GPa, flexural strength >80 MPa, and compressive strength >180 MPa. The achieved mechanical properties have been discussed in light of the analytical micromechanical models for Young's modulus and minimum solid area theory. Finally, the influence of processing temperature on the evolution of porosity and crystalline phases has been systematically studied and the dependence of porous composites' stiffness on these parameters has been investigated in detail. [ABSTRACT FROM AUTHOR]

To address the challenge of poor fracture toughness of lithium disilicate glass-ceramics, which hinders their application as posterior single crowns and three-unit fixed bridges, the concept of fiber toughening was employed. In this study, Li 2 Si 2 O 5 fibers were successfully prepared through an electrospinning technology combined with sol-gel followed by a heat treatment. The fibers could be further densified by adding SiO 2 nano-powder to partially replace TEOS as a silicon source and the possible mechanism was put forward. By using the fibers as the reinforcement phase, the uniform fiber-toughened Li 2 Si 2 O 5 glass-ceramic composites were successfully produced by hot pressing sintering. These composites exhibited significant enhancements in mechanical properties, including a flexural strength of 315 ± 10 MPa, fracture toughness of 4.57 ± 0.35 MPa m1/2, and Vickers hardness of 5.61 ± 0.28 GPa, respectively. Notably, the highest fracture toughness of the composite increased by 41 % compared to the samples without fiber reinforcement, which was attributed to the toughening mechanisms including crack deflection, fiber bridging, and fiber pull-out. The results demonstrated the advantages of Li 2 Si 2 O 5 fibers in toughening glass-ceramic materials, thereby expanding the application areas of this material. [ABSTRACT FROM AUTHOR]

The hydratable magnesium carboxylate (HMC) bonded castables have a high-level gas permeability while the mechanical strength decreased sharply during drying process. Silica-gel with high activity is a porous structure after drying and can potentially increase the intermediate-temperature strength without reducing the gas permeability of the castables. In this study, the mechanism of silica-gel modified the HMC, and the effects on the properties of the castables were investigated. The surface of the hydration products of HMC is covered with a thin protective layer of siloxane network. The proportion of fine permeable pores (0.1 μm ∼1 μm) increased, optimizing the connected network channels in the castables. Compared to the pure HMC bonded castables, with the HMC/silica-gel mass ratio of 2, the cold modulus of rupture of the castables increased by 2 times after heat treatment in the range of 400 °C ∼600 °C. Especially, the permeability constants Darcian k 1 and non-Darcian k 2 increased by 37 times and 38 times after heat treatment at 600 °C, respectively. [ABSTRACT FROM AUTHOR]

A simple and low-cost method for preparing SiC f /mullite composites with high density, mechanical, and absorbing performance using a vacuum pressure impregnation (VPI) system has been developed. The densification mechanism of the mullite matrix was investigated, and the effects of impregnation pressures on the flexural strength, interfacial bonding strength, and the electromagnetic wave (EMW) absorbing performance of SiC f /mullite composites were also studied. The dense composite was prepared under 3 MPa pressure with a porosity of 6.23 % and median pore diameters (MPDs) of 13.02 nm. The preparation efficiency was improved with the impregnation circles decreased from 20 times to 13 times. The flexural strength of SiC f /mullite composites prepared by VPI is 297 MPa, which is improved 230 % of the one prepared by the traditional vacuum impregnation method. Benefiting from the synergistic effects of appropriate impedance matching and multiple polarization loss, the effective absorption bandwidth (EAB, RL < −10 dB) of the SiC f /mullite composites increases from 2.17 GHz to 2.80 GHz in the X band. This work has a positive application value for the manufacture of high-strength EMW absorbing composites in terms of significantly reducing the preparation cost and cycle duration. [ABSTRACT FROM AUTHOR]

Ti 3 SiC 2 , as one of the most typical MAX ceramics, has been extensively studied as a potential high-temperature structural material. However, the restrictive relations between strength and toughness of Ti 3 SiC 2 and Ti 3 SiC 2 -based materials have hampered their industrial applications. Herein, we reported the successful fabrication of Ti 3 SiC 2 –(Ti 3 SiC 2 –C f) functionally graded materials (FGM) via hot-press sintering Ti 3 SiC 2 and short C f -derived preceramic papers. The microstructure evolution as well as the effect of sintering temperature on phase composition and interfacial reaction were investigated. Flexural strength and fracture toughness from ambient temperature to 1000 °C of the graded composites were determined to evaluate the mechanical performance. The results have shown that chemical reactions occurred between carbon fibers and Ti 3 SiC 2 matrix, which leads to the formation of SiC interfaces with strong covalent bonds. The newly developed Ti 3 SiC 2 –(Ti 3 SiC 2 –C f) graded composite materials exhibited excellent comprehensive performance as compared to that of monolithic Ti 3 SiC 2. The flexural strength and fracture toughness of the graded composite at room temperature can be reached to 526 MPa and 7.46 MPa m1/2, respectively. However, there is no significant change in flexural strength and fracture toughness from RT to 1000 °C. The fracture micrographs also reveal that fiber breaking、pulling out and debonding are the primary mechanisms that contribute to the superior mechanical properties of composites. The exceptional performance demonstrated in Ti 3 SiC 2 –(Ti 3 SiC 2 –C f) graded materials also makes them attractive choices for a variety of heatproof devices in aerospace sectors. [ABSTRACT FROM AUTHOR]

The optimization of the sintering process for ceramic stereolithography-based additive manufacturing is attracting high interest important due to its correlation with the final properties of the fabricated parts. In this work, a photosensitive zirconia suspension with low viscosity and high solid loading (48 vol%) was prepared using surface-modified zirconia ceramic powders, resulting in an improvement in long-term stability. The correlations between the sintering temperature (1400–1520 °C) and mechanical properties were investigated. The results showed that and the as-sintered zirconia parts exhibited a relatively high density of 99.5 ± 0.1 % and three-point flexural strength of 821 ± 65 MPa as well as excellent fracture toughness (4.37 ± 0.22 MPa m1/2) sintering at 1480 °C, which was attributed to the highly homogeneous microstructure without obvious pores or crack. The obtained insights regarding the correlation between sintering temperature, relative density, and flexural strength can provide practical guidance for the future applications of zirconia ceramics. [ABSTRACT FROM AUTHOR]

Crack propagation at the aggregate/matrix interfaces of refractories favors their brittleness reduction and better thermal shock resistance. Design of suitable interfaces is highly desirable in refractories. With coating of magnesium citrate and nickel nitrate hexahydrate catalyst on corundum aggregates, a thin MgAl 2 O 4 /CNTs interfacial layer of porous structure was formed between aggregate and matrix in low-carbon Al 2 O 3 -C refractories. The formation mechanisms of this interfacial layer are pyrolysis of magnesium citrate, reaction with corundum into MgAl 2 O 4 and growth of CNTs. Comparison study of mechanical results shows that this compound interfacial layer contributes to an increase in cold crushing strength, and brittleness reduction assessed with wedge splitting tests. The 3-times water quenching tests testified that brittleness reduction brings about a mild loss of cold modulus of rupture. The results support the conclusion that aggregate/matrix interface design is an effective method to reducing the brittleness and eventually improving the thermal shock resistance of refractories. • In-situ MgAl 2 O 4 /CNTs interfacial layer between aggregate and matrix. • The unique structure and composition of the interfacial layer reduce the brittleness. • Thermal shock resistance improvement by aggregate/matrix interface design. [ABSTRACT FROM AUTHOR]

RH degassing device is a crucial high-temperature equipment used for the production of high-quality and environmentally friendly steel. The majority of steel metallurgical companies utilize magnesia-chrome (MgO-Cr 2 O 3) refractories as linings in the RH degassing device. However, MgO-Cr 2 O 3 refractories have the potential risk of generating hexavalent chromium ions during usage, which have a carcinogenic effect. We developed novel periclase-Mg 1.08 Al 1.84 Ti 0.08 O 4 spinel (M-MATss) refractories, as a replacement for conventional MgO-Cr 2 O 3 refractories. Investigations focused on the effect of MATss content on the mechanical strength at ambient and high temperatures and thermal shock resistance of the M-MATss refractories. The results showed that MATss significantly improved the modulus of rupture at 1500 ℃ (HMOR) and the refractoriness under load (RUL), which exhibited comparable or even superior performance compared to MgO-Cr 2 O 3 refractories. M-MATss refractories with 15 wt% MATss content displayed the highest HMOR and RUL values of 4.6 MPa and 1655 ℃, respectively. This can be attributed to the reduction in silicate phase, which reduced the formation of liquid phase. Furthermore, the M-MATss refractories exhibited exceptional resistance to thermal shock due to the nonlinear mechanical behavior of microcracks caused by the thermal expansion mismatch between periclase and MATss, which contributed to enhanced resistance against crack propagation. [ABSTRACT FROM AUTHOR]

A high-strength, high-porosity and low-shrinkage Al 2 O 3 ceramics was prepared by direct ink writing method (DIW) using CaCO 3 as a mineralizer. The effect of CaCO 3 size and content on the phase formation, microstructural evolution and properties of porous Al 2 O 3 ceramics sintered at 1400 ℃ were systematically investigated. The results showed that the properties of the porous Al 2 O 3 ceramics were significantly affected by the particle size and content of CaCO 3. The fine particle size and increased CaCO 3 content could enhance the effective contact area between CaCO 3 and Al 2 O 3 , facilitating the reaction at high temperatures during the sintering at 1400 ℃. It was found that the favorite sintering condition promoted the formation of calcium hexaluminate (CA 6) and calcium dialuminate (CA 2). Microstructure analysis revealed that CA 6 exhibited a lamellar and tabular morphology, concentrated primarily at the pore boundaries, while some CA 6 were adhered on the surface of Al 2 O 3 particles. CA 2 were mainly embedded around Al 2 O 3 particles. The increase of CA 6 and CA 2 contents improved the flexural strength and porosity, and decreased the shrinkage rate. The Al 2 O 3 ceramics with high flexural strength, high porosity and low shrinkage rate were successfully fabricated by adding 20 wt% CaCO 3 with the particle size D 90 below 7.8 µm. The resulting flexural strength and porosity were 8.9 MPa and 71.9%, respectively, representing an improvement of 21.9% and 19.8% compared to Al 2 O 3 ceramics without CaCO 3. Additionally, the shrinkage rate in the X (0.9%), Y (1.1%), and Z (1.5%) directions decreased significantly, and the corresponding reductions were 75.0%, 73.2%, and 74.1%, respectively. [ABSTRACT FROM AUTHOR]

To evaluate the influence of printing orientation on flexural strength (σf) and elastic modulus (E) of different 3D printing dental restorative resins. Bar-shaped specimens (n = 20) were fabricated from two SLA-printed resins (FT- Formlabs Temporary, and FP- Formlabs Permanent) and two DLP-printed resins (DFT- Detax Freeprint Temp, and GCT- GC Temporary) using two building orientations (0º and 90º). The 3D-printed structures were aged (14 d) before submitted to three-point bending in 37ºC distilled water at a crosshead speed of 1.0 ± 0.3 mm/min until fracture to calculate the σf and the E values. The fractured surfaces were evaluated using stereomicroscopy and scanning electron microscopy (SEM) following fractography principles. Data were statistically analyzed using two-way ANOVA and Tukey post-hoc (α = 0.001). FP and FT showed significantly higher E values than DFT and GCT, irrespectively of printing orientation (p < 0.001). There was no statistical difference between the building orientations (0º and 90º) for the mean σf and E values for the resin materials evaluated. Fractographic characteristics were similar for the surface fracture from all the materials evaluated, showing typical brittle fracture behavior. Printing orientation did not influence of flexural strength and elastic modulus values for the 3D-printed resin structures evaluated. Surface topography was mostly governed by the 3D printer type. • Mechanical properties such as flexural strength and elastic modulus were not affected by the printing angle. • The surface topography of the evaluated 3D-printing resins is mostly governed by the printer type. • Typical brittle fracture features were found for the evaluated 3D-printing resins. [ABSTRACT FROM AUTHOR]

To investigate the impacts of speed and high-speed sintering on the densification, microstructure, phase composition, translucency, and flexural strength of yttria-stabilized zirconia (YSZ). A total of 162 disc-shaped specimens (n = 18) were cold-isostatically pressed from 3YSZ (Zpex), 4YSZ (Zpex 4), and 5YSZ (Zpex Smile) powders (Tosoh Corporation) and sintered according to the following protocols: conventional (control, ∼12 h), speed (∼28 min for 3YSZ; ∼60 min for 4YSZ and 5YSZ), and high-speed (∼18 min) sintering. Dimensions of zirconia specimens after sintering and polishing (1-μm diamond grit finish) were Ø13.75 × 1 mm. Density, microstructure, phase content, translucency parameter, and biaxial flexural strength were evaluated using Archimedes', SEM, XRD, spectrophotometric, and piston-on-3-ball methods, respectively. Data were analyzed with either one-way ANOVA and Tukey's test or Kruskal–Wallis with Dunn's test (α = 0.05). For all YSZ compositions, conventional sintering yielded the highest density followed by speed then high-speed sintering. All sintering protocols resulted in similar strength values; however, speed and high-speed sintering protocols afforded significantly lower translucency relative to conventional sintering. XRD analysis revealed similar spectra for YSZs sintered by various protocols. The speed sintered specimens had the smallest grain size whereas the high-speed sintered 5YSZ possessed the largest grain size among all groups. SEM examination of all YSZ compositions revealed that the average pore size was an order of magnitude smaller than the average grain size. Speed and high-speed sintering of YSZs yield similar strength but diminished density and translucency relative to their conventionally sintered counterparts. • Zirconia grain size increases from speed to conventional to high-speed sintering. • Zirconia porosity increases from conventional to speed to high-speed sintering. • The pore size is 1/10 of the grain size in speed and high-speed sintered zirconia. • Even a small number of tiny pores can have a big impact on zirconia translucency. • Low porosities and small pores have little bearing on zirconia flexural strength. [ABSTRACT FROM AUTHOR]

The objective of this study was to 1) compare the stress corrosion coefficient (n) of a Y-TZP obtained by two fatigue tests: cyclic and dynamic and 2) evaluate the effect of frequency in the characteristic lifetime and the existence of interaction between the cyclic fatigue and slow crack growth. A total of 145 Y-TZP specimens were produced in accordance with the manufacturer's instructions. These specimens, measuring 4.0 × 3.0 × 25.0 mm, were used for dynamic (n = 70) and cyclic fatigue tests (n = 75). The specimens were obtained from CAD/CAM blocks, sectioned, and sintered in a furnace at 1530 °C with a heating rate of 25 °C/min. They were tested in their "as-sintered" form without any additional surface treatment. The fatigue tests were conducted using a four-point bending to obtain the slow crack growth parameters (n). The cyclic fatigue test was also conducted in two frequencies (2 and 10 Hz), using stress levels between 350 and 600 MPa. Data from these tests were analyzed using ASTM C 1368–00 formulas and Weibull statistics. Scanning electron microscope (SEM) was used for fracture surface analysis to identify the origin of the fracture. Critical defect size was measured and used, along with flexural strength values, to estimate fracture toughness. Dynamic fatigue test data were used to obtain subcritical crack growth (SCG) parameters and perform Weibull statistical analysis. The cyclic fatigue data were used in the General Log-linear Model equation using the ALTA PRO software. Data were analyzed using one-way ANOVA followed by Tukey post-hoc tests and Student's t-test at a significance level of p ≤ 0.05. In the dynamic fatigue test, the values obtained for σ fo and n were 667 and 54, respectively. This parameter indicates how the strength of the material diminishes over time due to internal cracks. The Weibull parameters obtained from the same test results were m = 7.9, σ 0 = 968, 9 and σ 5% = 767, which indicates the reliability of the material. The Weibull parameters obtained by cyclic fatigue were statistically similar for the two frequencies used, the m * was 0.17 (2 Hz) and 0.21 (10 Hz); characteristic lifetimes (η) were 1.93 × 106 and 40,768, respectively. The n values obtained by cyclic fatigue were 48 and 40 at frequencies of 2 and 10 Hz, respectively. There was no effect of the frequency, the stress level or the interaction of the two in the Y-TZP lifetime, when analysed by General Log Linear Model. the n values obtained by cyclic and dynamic fatigue tests showed no statistically significant difference and the effect of frequency in the characteristic lifetime and the existence of interaction between the cyclic fatigue and subcritical growth were not observed in the tested specimens. • The type of fatigue test did not affect the coefficients of susceptibility to subcritical growth (n) for a dental Y-TZP. • The frequency used in the cyclic fatigue test had no influence on the fatigue parameters of the Y-TZP tested. • There was an increase in the defect size with decreasing loading rate, which explains the drop in strength. [ABSTRACT FROM AUTHOR]

This study aimed to compare the four-point flexural strength of CAM-milled and sintered (as-sintered, AS) specimens with those of high-polished (HP) specimens using chairside polishing systems to simulate clinical surface conditions. Seven full-contour zirconia CAM/CAM blanks with various yttria contents (3, 4, 5 mol%) including three high-translucent groups (5Y) were selected to prepare flexural specimens. The bend bar specimens (2.0 × 4.0 × 25.0 mm3) were fabricated by using STL file and dental CAM machine with the respective zirconia blanks (98 mm ϕ and 10–14 mm in height). Twelve bar specimens were machined from one zirconia puck and a total of 24 specimens were prepared from each group. The pre-sintered bar specimens were sintered by using a dental zirconia furnace at 1530–1550 °C for 2 h according to the instructions. All sintered specimens were divided into two groups: as-sintered (AS) group and high-polished (HP) groups (n = 12). HP groups were subjected to polishing one surface of specimens using a three-step polishing system and finally finished with diamond polishing. After cleaning and drying, the flexural strength of all specimens was determined by a fully articulating four-point flexure fixture consisting of a 1/4-point test configuration with an inner/outer span of 10/20 mm. Statistical differences between AS and HP groups were conducted with Weibull analysis. The fractured surfaces of zirconia specimens were observed using a field emission SEM and EDS to detect failure origins. The mean AS flexural strength values were significantly lower than those of HP counterparts. However, Weibull moduli expressing the reliability of HP groups were generally decreased although not significantly in comparison to their AS. The fracture of the AS specimens mostly originated from extrinsic CAM-milling defects, while the HP specimens were fractured from intrinsic subsurface or volume defects including pores, large grain clusters, inclusions, and corner-located critical flaws. Two high-translucent (5Y) zirconia groups were not affected in their strength and reliability after polishing, whereas one 5Y zirconia significantly increased its strength but significantly lowered its reliability. The extrinsic and intrinsic strength-limiting defects should be considered in evaluating the flexural strength and reliability of dental CAD/CAM zirconia ceramics for full-contour restorations. For the materials tested in this study, more optimized processing of blanks and milling protocols of pre-sintered zirconia blanks should be developed including post-sintering surface finishing to reduce the flaw population regulating strength and reliability which will affect the survivability of dental zirconia prostheses. [Display omitted] [ABSTRACT FROM AUTHOR]

This paper studied titanium diboride (TiB 2) effects on the structure and properties of AlMgB 14 ceramics. AlMgB 14 –TiB 2 samples with 30 wt% and 50 wt% TiB 2 were obtained by the self-propagating high-temperature synthesis. The addition of 30 wt% TiB 2 did not significantly change the phase composition of the AlMgB 14 ceramics, which remained comparable with the initial powder mixture composition. However, increasing the TiB 2 amount to 50 wt% resulted in the MgAl 2 O 4 spinel phase appearance. The addition of TiB 2 significantly increased the microhardness of AlMgB 14 from 7 GPa to 19.9 GPa, compared to the initial material, and also increased its flexural strength to 314 MPa. [ABSTRACT FROM AUTHOR]

For reaction-bonded silicon carbide (RB-SiC) ceramics, the use temperature cannot exceed 1300 °C due to the existence of free silicon. In order to improve its high temperature performance, RB-SiC ceramics were treated by vacuum heat treatment above 1300 °C to remove free silicon, and then modified by post-impregnation pyrolysis (PIP) process with polycarbosilane (PCS). The porosity, bulk density, and flexural strength of the ceramics were measured system atacially. The results show that the RB-SiC can completely remove the free Si, when the temperature exceeds 1700 °C. But its mechanical strength is significantly reduced. The strength of RB-SiC heat-treated after 1900 °C is generally higher than that of materials heat-treated below 1800 °C. In the PIP process, the pyrolysis products of PCS are evenly distributed in the pores of vacuum-heat-treated ceramics (VHT-SiC) to replace the initial free silicon. After 5 PIP cycles, the bulk density of the VHT-SiC increased from 2.56 g cm−3 to 2.70 g cm−3, the porosity reduced from 17.22 % to 12.04 %, and the flexural strength increased by 35.56 %. Therefore, this work provides a simple and efficient method for the preparation of complex SiC components with high temperature resistance (>1400 °C). [ABSTRACT FROM AUTHOR]

In this paper the long-term oxidation resistance of SiC f /SiC composites manufactured by a single PIP technique and a hybrid CVI-PIP technique at 1200 °C in a static air has been systematically studied. It has been found that after oxidation at 1200 °C for 200 h, SiC f /SiC composites by the hybrid CVI-PIP technique can retain flexural strength as high as 76% and still exhibit a typical quasi-plastic fracture. In contrast, after oxidation for 100 h, SiC f /SiC composites produced by the single PIP technique can only keep 31.8% of their initial flexural strength and demonstrate a typical brittle fracture. An insertion of a dense and crystalline CVI derived SiC layer between fibers/interphase and PIP derived matrix makes the difference. To be specific, for those single PIP derived composites, i.e. without this CVI SiC layer, the fibers/interphase are totally exposed to oxidative environments due to the nature of PIP derived matrix that is porous and full of micro-cracks. Worse still, the oxidized products of PIP derived matrix, viscous and sticky SiO 2 , tends to tightly wrap up fibers, forming a strong fiber/matrix bond. On the contrary, for those hybrid CVI-PIP derived composites, the dense CVI SiC layer serves as an oxidation barrier, not only blocking the inward flowing of oxygen to invade interphase/fibers, but also precluding the viscous and sticky SiO 2 reach fiber surface. The superior properties of SiC f /SiC composites produced by hybrid CVI-PIP technique suggest it be a desirable manufacture technique for industrial applications. [ABSTRACT FROM AUTHOR]

Direct ink writing (DIW) is a promising additive manufacturing technique for fabricating structural ceramics, including alumina-toughened zirconia (ATZ), heavily reliant on the rheological properties of the paste. The rheological properties of aqueous ATZ pastes with 25 wt% Pluronic® F127 hydrogel and solid loadings of 28–44 vol% were investigated, complemented by characterization of the parts, including relative density and shrinkage measurements, to assess the printability. The 42 vol% paste was identified as most suitable for producing high-density parts with minimal shrinkage. A controlled drying process gradually decreased humidity from 90% to 30% while raising temperature from 25 to 60°C over 4 days to prevent drying defects. Mechanical testing showed DIW-printed high-density (97.2±2.2%) parts with a mean flexural strength of 670±270 MPa, Vickers hardness of 13.6±2.8 GPa, and fracture resistance of 4.4±0.2 MPa, highlighting the potential for DIW to create high-density ATZ ceramic parts with favorable mechanical properties. [ABSTRACT FROM AUTHOR]

The fluorite-perovskite dual-phase Ce 0.9 Pr 0.1 O 2- δ -Pr 0.6 Sr 0.4 Fe 0.9 Al 0.1 O 3- δ (CP-PSFA) oxygen transport membrane (OTM) was developed to explore the properties and interaction of the two phases on the crystal structure, sintering behavior, thermochemical expansion, and oxygen release property, mechanical strength, and stability of the dual-phase membrane. The migration of oxygen vacancies between two phases causes the shrinking and expansion of the lattice of CP and PSFA phases, and the lattice of PSFA with higher TEC is compressed while the CP is stretched in the dual-phase membrane at the high-temperature range. The CP phase can significantly improve the mechanical properties of the dual-phase membrane, among which the flexural strength of the CP-PSFA reaches 303±42 MPa, almost twice that of PSFA membrane. Moreover, the high reducing gas resistance of the CP phase gives the CP-PSFA membrane more excellent high-temperature chemical stability. These results offer new insights into developing mixed ionic-electronic conducting dual-phase OTMs. • The CP and PSFA phases form separately but affect each other's sintering behavior. • The migration of oxygen vacancy from CP to PSFA distorts the lattice of phases. • The stress in the two phases does not affect the migration ability of oxygen ions. • The densifying of the CP and fining grain of the PSFA improve mechanical properties. • The CP phase enhances the structural and chemical stability of the CP-PSFA OTM. [ABSTRACT FROM AUTHOR]

Potassium sodium niobates (KNNs) have garnered significant attention owing to their lead-free nature and potential for use in self-cleaning membranes. This paper presents the synthesis of (K 0.5 Na 0.5)NbO 3 materials for the fabrication of porous membranes, which enable in situ ultrasonic resonance to effectively eliminate contaminants from the membrane surface. KNN powder was synthesized via solid-state reactions, and the membranes were prepared using conventional sintering techniques. The effects of ball-milling time and calcination temperature on the phase structure, pore size, permeance, flexural strength, chemical stability, and piezoelectric properties were comprehensively investigated. The optimal membranes exhibited an average pore size of approximately 300 nm, a porosity of 23 %, and permeance of 220 L m−2 h−1 bar−1 at a sintering temperature of 1050 °C. A polarized electrical field with a strength of 1 kV/mm was applied to the membranes, resulting in an ultrasonic response of 20 mV at an excitation voltage of 20 V with a frequency of 200 kHz. Furthermore, the in situ anti-fouling performance was evaluated by conducting filtration tests on a 500 ppm oil-in-water (O/W) emulsion, demonstrating that the stationary flux increased by 46.7 % when subjected to an excitation voltage of 60 V. [ABSTRACT FROM AUTHOR]

The Bi 2 O 3 –B 2 O 3 –SiO 2 –ZnO–Al 2 O 3 (BBSZA) glass/Al 2 O 3 composites are prepared by quenching and quenching-free methods and conducted a comparative analysis of their microstructures and properties. The results reveal that the BBSZA/Al 2 O 3 composite obtained by quenching free method has smaller pores and superior performance. Specifically, at a BBSZA content of 50 wt%, the composite exhibits a thermal conductivity of 5.352 W/m·K and a flexural strength of 193.54 MPa, which are 1.38 times and 2.08 times those obtained using the quenching method, respectively. XRD and TEM analyses, along with parallel experiments using other glasses, suggest that presintering crystallization may be the prerequisite for achieving denser composites via the quenching-free method. BBSZA glass reacts with Al 2 O 3 at the presintering process to generate a great amount of ZnAl 2 O 4 crystals, which enhances grain boundary energy and increases sintering density. This work provides insights into the low-cost and high-performance development of low temperature co-fired ceramics (LTCC). [ABSTRACT FROM AUTHOR]

In this study, the synthesis of C f /(Hf 1/2 Zr 1/3 Ti 1/6)C non-equimolar middle-entropy composites was reported through precursor infiltration and pyrolysis processing for the first time. The pyrolysis process of the (Hf 1/2 Zr 1/3 Ti 1/6)C precursor was examined by XRD, while the resultant ceramic was characterized by SEM, EDS, and TEM. The results showed that precursor-derived (Hf 1/2 Zr 1/3 Ti 1/6)C powders were characterized by single-phase and uniformly distributed elements from microscale to nanoscale. The C f /(Hf 1/2 Zr 1/3 Ti 1/6)C composites exhibited a density of 2.741 g/cm3 and a porosity of 11.49 vol%. The various elements were uniformly distributed throughout the material. It also demonstrated outstanding mechanical properties, with a flexural strength of 219.34 MPa and a modulus of 24.82 GPa. At the heat flux of 3 MW/m2, the oxides after ablation were inadequate to fully envelop the substrate. When the heat flux increased to 4 MW/m2, a dense Hf-Zr-Ti-O multiphase oxide layer was formed on the surface of the sample, providing the internal C f /(Hf 1/2 Zr 1/3 Ti 1/6)C composites against further ablation. At the heat flux of 5 MW/m2, (Hf, Zr)TiO 4 was severely consumed. Our research expands the application scope of non-equimolar middle-entropy composites in the domain of ultra-high temperature ablation resistance. [ABSTRACT FROM AUTHOR]