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Material extrusion (ME) 3D printing is an emerging technology to fabricate short carbon fiber reinforced SiC ceramic matrix composites (C sf /SiC CMCs) with highly oriented short carbon fibers. In this study, the C sf /SiC CMCs were fabricated by ME 3D printing combined with the following precursor infiltration and pyrolysis (PIP). The short carbon fibers could be well kept after the PIP process. The effects of solid loading and fiber content on the microstructure and mechanical properties of the C sf /SiC CMCs were also investigated. Higher solid loading was beneficial for obtaining the denser C sf /SiC CMCs with more oriented fibers. The introduction of short carbon fibers brought more pores. The bending strength and fracture toughness of C sf /SiC CMCs first increased and then decreased with the increase in fiber content. The pulling-out and breakage of short carbon fibers contributed to the improvement of mechanical properties. High performance C sf /SiC CMCs with a bending strength of 212.74 MPa and fracture toughness of 5.84 MPa m1/2 were simultaneously achieved when the solid content was 50 vol% and the fiber content was 20 vol%. It is believed that this study can provide some understanding of the 3D printing of fiber reinforced CMCs. [ABSTRACT FROM AUTHOR]

Binary CaO‐MgO‐Al2O3‐SiO2 (CMAS) ceramics composites of anorthite‐cordierite composition were synthesized from natural raw materials (kaolin and dolomite rock). The change of SiO2/Al2O3 ratio in kaolin/dolomite mixtures (12, 24, and 36 wt.%) and synthesized composites along with analysis of their phase composition transformations (X‐ray diffraction) during heat treatment (thermogravimetric and differential thermal analysis) give the controlled design of aluminosilicate matrices. The obtained ceramic composites are represented by anorthite, a cordierite‐like phase whose ratio varies from 1.3:1 to 2.8:1. Mullite crystals, also included in the composition, reinforce the anorthite‐cordierite matrix. The morphostructural features of the samples were studied using optical and scanning electron microscopy. The porosity ranges from 7.8% to 24.2% depending on dolomite content. The impurities of iron and titanium interfering with obtaining a qualitative product are leveled by the presented technique including the heat treatment scheme justified by thermogravimetric analysis. Obtained CMAS‐ceramics of anorthite‐cordierite composition correspond to industrial international standards by their technical characteristics and exceed the requirements for heat‐insulating and chemically resistant materials by compressive strength. [ABSTRACT FROM AUTHOR]

The development and commercialization of aerospace vehicles have posed significant challenges to the performance requirements for the corresponding materials. To meet these challenges, ceramic matrix composites (CMCs) have been developed and are widely used in the aerospace industry. However, their stability under extreme environmental conditions still needs to be improved. In this review, some properties of zirconium carbide (ZrC), which are related to extreme environmental applications of CMC are discussed first. Then, the effect of ZrC on the properties of CMC is comprehensively reviewed. ZrC can be introduced into the matrix and coated on the surface to increase the ablation resistance. The protection mechanisms of ZrC addition to CMCs, and the improvement in ZrC ablation resistance are explained. In addition, some perspectives on future developments are given. [ABSTRACT FROM AUTHOR]

The current study focuses on the role of composition in the oxidation behavior of three commercial SiC fibers (Hi‐Nicalon Type S (HNS), Tyranno ZMI, and Tyranno SA) in a steam‐containing environment at 1000°C. Oxide scales that form on each of the three fiber types differ in morphology, microstructure, and composition. Differences are attributed to O and C contents, crystallinity, and minor alloying elements. Oxidation kinetics of the HNS fibers follow linear/parabolic (Deal–Grove) predictions over the entire range of exposure times (to 96 h). In the other fibers, deviations from the initial linear/parabolic trend occur when either the scale crystallizes in situ during oxidation (as on the ZMI fibers) or when structural changes internal to the fiber alter the chemical environment at the scale/fiber interface (on the SA fibers). Adaptations of the linear/parabolic oxidation model are used to rationalize the growth kinetics in the latter two cases. Collectively, the data and analyses indicate a two‐fold difference in permeabilities of crystalline and amorphous silica scales. Inferred interface reaction rates further suggest faster oxidation for fibers with greater amounts of amorphous Si–O–C. Moreover, crystalline scales are more prone to cracking, because of their higher viscosity at elevated temperatures and a deleterious phase transformation upon cooling. [ABSTRACT FROM AUTHOR]

To understand the effect of processing and prefabricated pores on 2D woven SiCf/SiC composites (2DW‐SiCf/SiC), their crack propagation and mechanical response under tension load at meso‐ and macro‐ scale are investigated by a promising elastoplastic phase field method (EPPFM). Of much interest, the computational results are well consistent with the available experimental results, verifying the reliability of EPPFM. A significant dependence on pores is observed in the relationship between the strength, Young's modulus, work of fracture of 2DW‐SiCf/SiC and porosity when pores exist solely in the matrix out of yarns, and both in the matrix and yarns, respectively. Moreover, the more dangerous processing pores at mesoscale near yarn are attributed to the inconsistent deformation of the yarn and matrix. Finally, the EPPFM is used for the effect of geometry size on the joint failure mode of 2DW‐SiCf/SiC plate with prefabricated open holes under pin‐loading. Of importance, the more safe bearing failure mode occurs in 2DW‐SiCf/SiC plate when edge distance‐to‐hole diameter ratio and width‐to‐hole diameter ratio are greater than 1.5 and 3, respectively. [ABSTRACT FROM AUTHOR]

Specimens from a Hi‐Nicalon Type S/BN/SiC (MI) ceramic matrix composite with multiple machined holes were subjected to a furnace dwell and then tensile tested. The furnace temperature range was 500–900°C, and the atmosphere was pure steam to approximate the temperature and sea level partial pressure of water vapor in the cooling air going through turbomachinery cooling holes. Exposure of control specimens was done in laboratory air at the same temperatures. Tensile results along with microscopy and spectroscopy showed significant strength degradation in some conditions due primarily to oxidation of the boron nitride fiber coating, with coating volatilization at lower temperatures and probable fiber‐to‐matrix bonding and imposed fiber stresses at higher temperatures. The greatest strength degradation occurred in the 500–600°C steam range. The fiber coating oxidation/volatilization was especially evident near the holes and was exacerbated in the lower temperature tests by porosity networks that were open to the atmosphere at fiber tow ends at the specimen edges and along the inner walls of the holes. [ABSTRACT FROM AUTHOR]

This work presents a Finite Element approach to model the in-plane mechanical behavior of C/C-SiC fabrics at the lamina level, including the non-linear response of diverse lay-ups and the bending-to-tensile strength ratio at failure. The material model employs a decomposition into two idealized phases, which can be exploited to capture matrix- and fiber-dominated responses at a high level of abstraction. The constitutive law of the matrix phase adopts a Continuum Damage approach driven by two Tsai-Wu surfaces, while a quasi-brittle behavior is attributed to the fibers phase. This decomposition effectively represents the influence of matrix degradation on the response and failure of the laminates. Moreover, simulations reveal that a statistical distribution of the strength is required to represent some of the experimental outcomes. The correlation with experimental data that was achieved points out that the technique is a promising tool for supporting the early design phase of CMC structures. [ABSTRACT FROM AUTHOR]

In this paper, test results for woven ceramic matrix composites (CMCs) based on an oxide matrix and oxide fiber are presented. Stress–strain curves under cyclic loading for different in‐plane fiber orientations as well as strength values for different fiber orientations under tension and compression and under pure shear are presented. Based on the experimental data, a nonlinear damage model is derived which allows to determine the progressive degradation of the elastic moduli and the nonelastic remanent strain in a satisfactory manner. It has been implemented into the finite element code ANSYS and shows excellent convergence behavior. To predict the failure of CMC components, the failure mode concept proposed by Cuntze is extended to include friction effects due to tension and compression on the in‐plane shear failure mode. The predicted failure onset matches the experimental data very well, whereas existing models like the max‐stress or the Tsai–Hill criteria show larger deviations. [ABSTRACT FROM AUTHOR]

AbstractPolymer-derived ceramics (PDCs), synthesized through the thermal conversion of preceramic polymers, represent a unique class of materials characterized by their remarkable amorphous nature at elevated temperatures, reaching up to 1800 °C. This unique property allows PDCs to retain the memory of their precursor organic molecular networks, opening up exciting possibilities for tailoring their macroscopic, chemical, and physical properties to meet specific requirements. Among the various preceramic polymers, polycarbosilanes stand out as crucial precursors for silicon carbide ceramics. These versatile materials have been extensively modified with metals, nonmetals, and organic groups, enabling the development of advanced ceramic materials with tailored characteristics. This comprehensive review paper provides an in-depth exploration of the synthesis strategies employed to modify polycarbosilanes, including the incorporation of various metal, nonmetal, and organic groups. Furthermore, it delves into the wide-ranging applications of these modified polycarbosilanes and the resulting ceramic materials. The synthesis routes are elucidated, offering readers a thorough understanding of the synthetic conditions and underlying reaction mechanisms. For the first time, this review comprehensively outlines the diverse applications of modified polycarbosilanes and PDCs across multiple fields, including their potential as thermal protection systems for space vehicles, advanced electrode materials in batteries, advanced filter apparatus, photocatalytic materials, and 3D printing inks for advanced ceramics. Finally, the review concludes by discussing future directions and opportunities for advancing modified PCS in terms of applications, chemistries, and synthesis methods. [ABSTRACT FROM AUTHOR]

The thermal protection materials of ultra-high speed aircraft need the stealth performance, and it require the microwave absorbing materials should have high ablation resistance to serve under extreme conditions (>2000 °C). In this work, amorphous ZrOC–SiCN and SiCN were introduced into the inter-bundle matrix of SiC fiber reinforced Si 3 N 4 matrix composites to improve the ablation resistance while retaining the wave-absorbing properties. For SiC f /Si 3 N 4 , the SiC nanocrystallines in SiC fiber are oxidized into SiO 2 and accumulate on the surface, and the Si 3 N 4 matrix is first transformed into SiC grains and then the SiC grains are gradually ablated into spherical SiO 2 in the ablation process. After the introduction of ZrOC–SiCN and heat-treated at 1500 °C, the ZrCN can be formed to increase the scouring resistance of each woven layer, and the oxide film with high viscosity also can be formed, preventing the fiber bundles from being blown away in the central region, leading to the decrease of mass and line ablation rate from 12.2 mg/s and 27.3 μm/s to 7.3 mg/s and 16 μm/s, respectively. Meanwhile, the minimum reflection coefficient of the composite decreases from −4.9 to −10.6 dB. [ABSTRACT FROM AUTHOR]

Reactive melt infiltration (RMI) is a typical method to produce carbon fiber-reinforced ultra-high temperature ceramic matrix composites (C f /UHTCs), for which the molten Si is a very general and practical infiltrator. High-entropy carbide (HE-carbide) is a newly developed promising matrix phase of C f /UHTCs. Understanding the phase equilibrium relation in the HE-carbide and Si reaction system can provide accurate guidance on designing the RMI process for preparing HE-carbide matrix composites with controlled phases and microstructure. This study systematically investigates W-containing HE-carbide and Si addition reactions at high temperatures. Samples with nominal starting compositions of (Ti 0. 2 Zr 0.2 Hf 0.2 Ta 0. 2 W 0.2)C- x Si (HEC- x Si, x = 2.5, 5 and 10 wt%) are prepared by spark plasma sintering technique at 1500 °C and 1700 °C with an axial pressure of 40 MPa for 10 min. The results show that adding 2.5 wt% or 5 wt% Si removes carbon from the HEC matrix, forming SiC and stable equimolar (Ti 0. 2 Zr 0.2 Hf 0.2 Ta 0. 2 W 0.2)C 1- x phase with carbon deficiency at high temperatures. In contrast, besides the SiC phase, the addition of 10 wt% Si in the HEC matrix may form unstable transient phases of (Ti 0. 2 Zr 0.2 Hf 0.2 Ta 0. 2 W 0.2)C 1- x with supersaturated carbon deficiencies at high temperatures, which finally decomposes into non-equimolar HE-carbide (Ti 0. 2 Zr 0.2 Hf 0.2 Ta 0. 2 W 0.2- y)C 1- z and metal silicide WSi 2 phases. The effects of the HEC and Si reactions on the microstructure evolution of the samples during sintering are discussed. Meanwhile, the mechanical properties of the samples with the reaction resulting microstructure are measured and briefly discussed. [ABSTRACT FROM AUTHOR]

In a classical chemical vapor infiltration (CVI) process, the competing effects of chemical kinetics and reagent gas transport lead to non‐uniform depositions such that outer layers of a preform densify faster leaving the core highly porous. Currently, CVI must be performed at a sufficiently low temperature to achieve good densification quality which leads to high processing time and cost. Volumetric heating of the preform, especially through microwaves, can create temperature inversion such that the core is hotter than the outer surface and potentially, overcome the challenges associated with isothermal CVI. Direct numerical simulations (DNS) of densification under various such temperature distributions indicate that microwave heating in CVI processing can lead to better (uniform) densification of porous preforms. The role of key parameters describing the temperature distributions on the densification behavior is investigated. Strategic temporal control of the temperature distribution shows that processing times can be reduced by almost half while maintaining a good densification quality similar to that of low‐temperature isothermal processing. Inside‐out densification due to the inverted temperature profile is a key distinguishing characteristic of microwave assisted CVI. [ABSTRACT FROM AUTHOR]

Background: In-situ micro-computed tomography (µCT) technology is an attractive approach to investigate the evolution process of damage inside ceramic matrix composites (CMCs) during high-temperature service. The evolution process is highly time-sensitive under temperature-induced loads, and fast scanning is very necessary for in-situ µCT tests. Objective: The objective of this work is to provide a fast scanning method for in situ µCT tests on CMCs with complex microstructures by the innovation of a reconstruction algorithm. Method: To overcome the severe degradation of the reconstructed image quality resulting from sparse CT scans, a deep-learning-based multi-domain sparse reconstruction method was proposed. Three sub-networks including the projection-domain, image-domain, and fusion network were constructed in the multi-domain method to make full use of the information from the projection and image domain. Results: The proposed deep-learning-based sparse reconstruction method provided satisfactory µCT images on C/SiC composites with acceptable quality. The scanning time was reduced by 6 times. All selected evaluation metrics of the proposed method are higher than those of other single-domain methods and traditional iterative method. The segmentation accuracy of the µCT images obtained by the proposed method can meet the subsequent quantitative analysis. An in-situ tensile test of CMCs is conducted to further evaluate the performance in the practical application of in-situ experiments. The results indicate that the weak and thin micro-cracks can still be effectively retained and recovered. A detailed workflow to implement the method generally is also provided. Conclusions: Based on the deep-learning-based multi-domain sparse reconstruction method, the process of in-situ µCT tests can be greatly accelerated with little loss of the reconstructed image quality. [ABSTRACT FROM AUTHOR]

Achieving an optimal balance between mechanical properties, dielectric properties, and thermal shock resistance presents a significant challenge in the development of advanced ceramics. This study investigates Si 3 N 4 -BN composite materials, prepared by hot-press sintering with magnesium aluminum silicate (MAS) as the sintering additive, to assess the impact of varying hexagonal boron nitride (h -BN) content on their mechanical and dielectric properties, as well as their thermal shock resistance. At an h -BN content of 20 wt%, the BN layers act as a toughening phase through a pull-out mechanism, minimally impacting the composite's density. This composition results in superior fracture toughness (7.4 MPa m1/2), high strength (598 MPa), low dielectric constants (∼6.8), and dielectric loss (∼7.4 × 10−3). Notably, after a thermal shock at 1000 °C, the composite exhibits a peak residual strength of 621 MPa, surpassing its initial strength. This enhanced performance is attributed to the formation of a dense Mg–Al–Si–B–O oxide glass layer on the surface during thermal shock, which not only repairs surface defects but also induces compressive stress. The development of the Si 3 N 4 -BN-MAS composite, with its outstanding comprehensive performance, marks a significant advancement for materials used in high-temperature wave transmission applications. [ABSTRACT FROM AUTHOR]

Copyright of Acta Materiae Compositae Sinica is the property of Acta Materiea Compositae Sinica Editorial Department and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Acta Materiae Compositae Sinica is the property of Acta Materiea Compositae Sinica Editorial Department and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Sodium cobaltite (NaxCoO2) is one of the most renowned and thermoelectrically promising p‐type cobalt oxide materials, showing exceptional performance in this domain. Nonetheless, its thermal instability in air renders it unsuitable for high‐temperature applications such as energy harvesting from industrial waste heat. To utilize the beneficial properties of NaxCoO2, microscale NaxCoO2 template particles of significantly larger size were effectively embedded within a thermally stable Ca3Co4−yO9+δ–NaxCoO2–Bi2Ca2Co2O9 triple‐phase matrix. This approach additionally aimed to enhance the texture and boost the thermoelectric performance of the ceramic composite. Highly textured p‐type ceramic composites were fabricated via uniaxial cold‐pressing and pressureless sintering in air. The unique hexagonal NaxCoO2 template particles, produced through molten‐flux synthesis, allowed precise control over their shape and dimensions, while the matrix was synthesized via a sol–gel synthesis. The integrated NaxCoO2 particles of the textured composite exhibited increased thermal stability, showing no sign of decomposition at 1173 K in air, whereas the sole template particles decomposed at 1073 K during sintering. A 20 wt% template particle content in the textured composites resulted in a remarkably high and nearly temperature‐independent power factor of 8.8 µW cm−1 K2, corresponding to an improvement of 13% compared to that of the pure matrix material. [ABSTRACT FROM AUTHOR]

Ceramic matrix composites (CMCs) on one level are excellent materials for acoustic emission (AE) analysis. They are excellent waveguides for AE waveform transmission due to the high modulus to density ratio. CMC inelastic behavior is due to micro‐ and macrocrack formation from matrix crack interaction with the fibers via a relatively weak fiber/matrix interface which create ideal stress waves. Because of this, AE is an excellent detector of microcracks in general, and most importantly in the case of CMCs, the initial or lowest stress crack formation. This property can be related to long time stressed‐oxidation degradation of nonoxide composites, in particular. In addition, AE has been used to effectively determine the stress distribution for matrix cracks which cause the nonlinear stress–strain behavior. However, a key to quantitatively correlating AE with sources is first and foremost to locate where the AE originated. For a tensile test, most AE comes from the near‐grip region and the radius region outside the gage area of interest. Outside the gage region AE would not be considered useful data pertaining to stress/strain behavior and must be sorted out from the AE dataset. Location is determined by the difference in time of arrivals (TOAs) of waveforms received on each sensor from a given AE source. Automated TOA techniques such as threshold voltage crossing or Akaike information criteria (AIC) have limitations in overall accuracy of differences in TOA (Δt) of two different sensors required for location analysis. This study has incorporated several signal filter and enhancement techniques and an approach toward increasing the accuracy of the classic TOA techniques. First TOA was determined for the two sensors of the AE tests "manually" based on first extensional peak of the waveform, this served as the "exact" difference in TOA. Δt's were then determined for the various filter/TOA techniques and compared to those from the manual determined Δt. The best filter/TOA techniques resulted in more than two times better accuracy (defined as percentage of events within 0.1 µs of the exact Δt) than the conventional threshold crossing or AIC technique. [ABSTRACT FROM AUTHOR]

High Mach flight has put forward more stringent requirements for the material and structure design of new generation of high-speed vehicles. This paper reviews the application of ceramic matrix composites（CMCs） in the structural design of aircraft from the aspects of selection，application，and evaluation，and then the future development direction is put forward to provide reference for aircraft ceramic matrix composite structure design. The selection criteria and corresponding preparation methods of CMCs in different application scenarios are comprehensively reviewed，the typical applications of CMCs in aircraft structures are systematically introduced，and the evaluation criteria and ground test methods of the materials under near-service conditions are analyzed. To order to meet the future demands of aircraft，it is necessary to integrate computer-aided optimization technology and innovative preparation methods to enhance the temperature resistance and fatigue performance of CMCs. Developing highly reliable，long-life joining techniques and integrated design solutions will fully leverage the advantages of these materials. Additionally，in-situ characterization techniques under multi-physical field coupling need to be developed to obtain the performance evolution behaviour of CMCs in actual use，providing a reliable basis for the lightweight structural design of aircraft.

The dovetail of ceramic matrix composites（CMC）turbine blade is the key to the assembly and ability to withstand centrifugal loads of the blade. In order to study the mechanical behaviour of the blade dovetail prepared by the melt infiltration（MI）method under the tensile load in the radial direction of rotating，and verify the influence of the internal quality of the dovetail on its static tensile strength and failure mode，the CMC high pressure turbine dovetail element specimens were designed and fabricated，and a uniaxial static tensile test was conducted，the internal quality of the test specimens was scanned using non-destructive X-ray CT. The test process was monitored using DIC and acoustic emission method. The results show that the CMC dovetail is able to maintain in complete contact under uniaxial static tensile loads，and its static strength and failure are very sensitive to its internal quality，especially to the delamination defects. When there are no delamination defects in the dovetail，the damage generally starts from the neck and quickly spreads，the damage starting load is near the maximum fracture load，and the fracture surface is zigzag. When there are delamination defects in the dovetail，the fracture starts from the defects，and the delamination gradually spread and cause the fracture surface of the dovetail，the damage starting load is decreased by 99.05%，and the maximum failure load is decreased by 14.29% compared to the case of no delamination defects，and the fracture surface is consistent with the delamination defects.

With the widespread application of ceramic matrix composites in hot end components of advanced aeroengines，it becomes particularly important to conduct efficient and accurate nondestructive characterization of defects/ damages formed during the whole life cycle. Due to the complex preparation and forming process of ceramic matrix composites and the high heterogeneity and anisotropy caused by multiphase composite，the traditional nondestructive testing technology based on the assumption of global homogenization faces many challenges. Based on the application of ceramic matrix composites in aeroengine field，the typical defect/damage types and characteristics in the whole life cycle of ceramic matrix composites are analyzed. The research progress and application of nondestructive characterization techniques of ceramic matrix composites in recent years are reviewed，the main challenges faced by existing nondestructive characterization techniques are summarized，and the future development trend is prospected.

Previously conducted studies determined that the reactive sintering of B 4 C and stoichiometric additions of TiSi 2 or Ti 5 Si 3 intermetallics created a dense TiB 2 -SiC double-phase system that could be classified as ultra-high temperature ceramics (UHTC). In this work, a spark plasma sintering (SPS) technique was used to improve the sintering process and thus further reduce the obtaining temperature and improve the final microstructure and mechanical properties of the proposed, double-phase TiB 2 -SiC UHTC systems. To evaluate the effects of the experiment, a comprehensive study of phase composition, microstructure and mechanical properties was added. As a result, minimal sintering temperatures were further reduced from 1420 - 1650 ºC to a range of 1200–1400 ºC. Among the prepared composites those sintered at 1400 ºC achieved the best properties. The prepared composites maintained high hardness (up to 24.85 GPa), high tensile strength (up to 309 GPa), relatively high fracture toughness (up to 4.80 MPa∙m1/2) and relatively low density, all of which characterized TiB 2 -SiC UHTC systems. [ABSTRACT FROM AUTHOR]

In this study, two types of porous Cf/Cm composites were obtained by introducing pyrolytic carbon (PyC) and pyrolytic carbon/furan resin carbon (PyC/FRC). Subsequently, Cf/Cm-SiC-(ZrxHf1−x)C composites with different carbon matrices were prepared by introducing SiC and (ZrxHf1−x)C matrices into the porous Cf/Cm composites via the reactive melt infiltration method, specifically termed as Cf/PyC-SiC-(ZrxHf1−x)C and Cf/PyC/FRC-SiC-(ZrxHf1−x)C composites. The microstructures of the porous Cf/Cm and Cf/Cm-SiC-(ZrxHf1−x)C composites with different carbon matrices were examined, and a comprehensive analysis was conducted on microstructural evolution and mechanical behaviors of the Cf/Cm-SiC-(ZrxHf1−x)C composites. The results indicate that both Cf/Cm-SiC-(ZrxHf1−x)C composites underwent similar microstructural evolution processes, differing only in terms of evolution kinetics and final microstructure. Differences in the pore structures of porous Cf/Cm composites, as well as in the reactivities of carbon matrices, were identified as primary influencing factors. Additionally, both Cf/Cm-SiC-(ZrxHf1−x)C composites exhibited "pseudo-ductile" fracture characteristics, with flexural strengths of 214.1 ± 8.8 MPa and 149.6 ± 12.2 MPa, respectively. In the Cf/PyC-SiC-(ZrxHf1−x)C composite, crack initiation during loading primarily originated from the ceramic matrix, while in the Cf/PyC/FRC-SiC-(ZrxHf1−x)C composite, failure initially arose from the residual FRC matrix. Excessive fiber corrosion and the presence of residual low-modulus FRC matrix resulted in lower mechanical performance. [ABSTRACT FROM AUTHOR]

This study investigated the influences of WC and HfB2 additives along with SiC reinforcement (with various particle sizes) on densification, microstructure, and mechanical properties of ZrB2–SiC composites. The results showed that WC and HfB2 addition formed a solid solution of (Zr,W,Hf)B2 with a core–shell structure, whereas the remaining WC transformed into WB. Moreover, nano‐sized SiC caused a much better impact on densification compared to micro‐sized SiC. A small fraction of localized phases like ZrC, HfB, and (Hf,Zr)C in the form of solid solution were also formed. The maximum room temperature flexural strength and the fracture toughness of the sample containing 150 nm SiC and 8.9 wt.% WB were measured to be 682 ±$ \pm $ 17 MPa and 6.5 ±$ \pm $ .3 MPa m1/2, respectively. [ABSTRACT FROM AUTHOR]

This paper presents an investigation into the water permeability of an all-oxide ceramic matrix composite. To determine the parameters and characterize the water permeability of the ceramic composite material, an experimental study was carried out in which a dedicated test rig was constructed and commissioned. A total of five different configurations of composite tubes were tested. They differed in fibre roving strength, winding angle, fibre bundle arrangement during winding, and matrix grain size distribution. To better understand the internal structure of the analysed ceramic matrix composite material, the experimental study used scanning electron microscopy for microstructure and porosity observation. The tested tubes will be used as liners in an oxy-combustion chamber in future studies. The experiments obtained new and interesting results regarding the water permeability of the ceramic matrix composite with different structural parameters. It was also observed that, as with some porous materials, the permeability of ceramic matrix composites decreases with time as more and more liquid is pressed through it. [ABSTRACT FROM AUTHOR]

In fiber-reinforced components, the fiber alignment and orientation have paramount influence on the thermo-mechanical properties of the resulting composite, for both short and continuous fiber. Here we present the case of an ultra-refractory matrix intended for extreme environment applications, ZrB 2 , reinforced with 20 vol% and 50 vol% short carbon fibers. In both cases, fibers tend to align perpendicular to the uniaxial pressure applied during shaping and sintering of a pellet, although the fiber tilt across the pellet thickness is difficult to determine. Moreover, for high volume fractions of reinforcement, the spatial distribution of the fibers is heterogeneous and tends to have domains of preferential orientations. We compare the information on the fiber distribution as collected by scanning electron microscopy images, X-ray computed tomography and synchrotron X-ray refraction radiography (SXRR). The three techniques prove to be complementary. Importantly, we demonstrate that SXRR yields the most statistically significant information due to the largest field of view, yet with a sensitivity down to the nanometer, and that can be successfully applied also to heavy matrix materials, such as zirconium boride. [ABSTRACT FROM AUTHOR]

The computer‐aided analysis of microstructure evolution during the sintering process of self‐lubricating ceramic tools can unveil the underlying sintering mechanism and optimize experimental parameters. In this study, a novel self‐lubricating ceramic tool material, Al2O3/SiC/h‐BN@Al2O3, was fabricated with Al2O3 as the matrix, SiC as the reinforcement phase, and h‐BN@Al2O3 as the solid lubricant. The Monte Carlo (MC) method was employed to construct a model of self‐lubricating ceramic tool material, consisting of Al2O3/SiC/h‐BN@Al2O3. Subsequently, the sintering process was analyzed to investigate the influence of particle size and content of reinforced SiC, as well as the content of coated solid lubricant h‐BN@Al2O3, sintering pressure, and temperature on the microstructure of the tool. Optimal composition and sintering parameters were determined: 3 vol% for SiC additive amount with a particle size of 0.05 μm; 5 vol% for h‐BN@Al2O3 additive amount; and an optimal sintering temperature at 1650°C. The development of self‐lubricating ceramic tool materials, Al2O3/SiC/h‐BN@Al2O3, was realized through the employment of the aforementioned parameters. Their mechanical properties and microstructure were comprehensively characterized. The bending strength, fracture toughness, and Vickers hardness of the experimentally‐prepared Al2O3/3 vol%SiC/5 vol%h‐BN@Al2O3 self‐lubricating ceramic tool material were determined to be 722.42 MPa, 6.5 MPa·m1/2, and 20.65 GPa, respectively. [ABSTRACT FROM AUTHOR]

To achieve Si‐free refractory ceramic matrix composites exposed to an oxidizing atmosphere at approximately 2000°C, a Ti–Zr–Mo ternary alloy melt‐infiltration (MI) method was developed for the production of carbon fiber‐reinforced refractory high‐entropy ceramic matrix composites (C/RHECs), with high‐entropy carbides serving as the matrix. This approach was designed using calculation phase diagrams (CALPHADs) and the calculation of thermodynamic parameters. The combination of CALPHAD and the calculation of alloy and carbon reactivity enabled the prediction of reaction and infiltration behavior into a preform comprising carbon fiber, carbon black, and transition metal carbide powders. Furthermore, C/RHECs featuring a (Ti, Zr, Hf, Nb, Ta, Nb, Mo)C matrix were experimentally fabricated through the Ti–Zr–Mo alloy MI method in accordance with the design. The arc‐wind tunnel tests on the C/RHECs conducted at approximately 2000°C revealed surfaces covered with complex oxides. The apparent oxidation rate of the C/RHECs was similar to that of Si‐containing ceramics and composites. These results indicate that complex oxides act as a barrier to oxygen diffusion toward unoxidized regions, making Si no longer essential for protecting materials from oxidation above 2000°C. [ABSTRACT FROM AUTHOR]

Silicon carbide fiber–reinforced silicon carbide (SiCf/SiC) composites have been expected to be used as next‐generation heat resistant structural materials with high reliability. The fiber/matrix interface for SiCf/SiC composites plays an important role for toughening and strengthening, and it is important to form the optimal interphase for SiCf/SiC composites. In this study, hexagonal‐boron nitride (h‐BN), which shows better oxidation resistance than carbon, was selected as the interphase for SiCf/SiC composites, and h‐BN coating was formed on low‐conductive SiC fibers by the electrophoretic deposition (EPD) method using flaked h‐BN suspension prepared by wet‐jet milling. Unidirectional SiCf/SiC composites with the BN interphase formed by the EPD method were prepared by polymer impregnation and pyrolysis (PIP) method, and their mechanical properties were evaluated. The uniform h‐BN interphase was successfully formed on the low‐conductive SiC fibers by EPD when thin polypyrrole (Ppy) coating, that is, conductive polymer, was formed on the SiC fibers. The h‐BN coating became denser by heat‐treatment at 1000°C, and the h‐BN coating deposited tightly on the SiC fibers was confirmed. It was demonstrated that the SiCf/SiC composites with the uniform and relatively dense h‐BN interphase formed by EPD using flaked h‐BN particles exhibited pseudo‐ductile fracture behavior with large amount of fiber pullout and higher fracture energy. [ABSTRACT FROM AUTHOR]

BN interphases with different microstructures and a structural gradient were prepared by chemical vapor deposition (CVD) within SiC/SiC minicomposites. The interfacial shear stress (ISS) measured by the fiber push‐out test and the debonding location in the fiber/matrix interface zone during mechanical loading depends on the BN interphase structure. The ISS is higher when the structural organization of the BN interphase is poor, in which case debonding occurs on the fiber side. The Hi‐Nicalon S fiber surfaces were gas‐treated to strengthen the bond with the interphase. BCl3‐based reactive CVD treatments have produced a thin boron carbide layer on the fiber surface, resulting in a 30% increase in ISS. However, the minicomposites are brittle in tensile tests due to fiber bridging by parasitic boron clusters. Short‐time CVD of SiC increases the fiber surface roughness and doubles the ISS, but again the minicomposites are brittle, indicating the need to better modulate the resulting roughness and adjust the interphase. Finally, ammonia treatments have nitrided the fiber surface and increased the ISS by 12%. While the increase in interfacial bonding measured at the microscopic scale was small, this nitriding treatment did not embrittle the minicomposites at the macroscopic scale. [ABSTRACT FROM AUTHOR]

Crack propagation in ceramic matrix composites is very difficult to observe and to quantify. To investigate crack formation in all‐oxide ceramic composites, single edge notched bending tests were performed including loading‐unloading cycles and online monitoring of surface deformation using digital image correlation. The crack length was calculated by the compliance method with the crack opening displacement determined optically using digital image correlation. Obtained crack length values were found to be too small considering the sample geometry. Secondly, surface strain monitoring was used to investigate the crack growth. Analysis of cyclic force‐crack opening displacement curves and the results from strain monitoring indicated no major crack growth for loads below maximum force but still a moderately decay of force after onset of cracking. Graphical analysis of the surfaces of broken samples showed crack flank lengths ranging from 3 to 6 mm. Due to highly individual crack deflection mechanisms throughout the thickness of the oxide ceramic composites, deviations between front and back of specimens are found. The results demonstrate the necessity to use individual crack length measurements of each specimen for quantitative fracture mechanical evaluation. Strain monitoring during testing was shown to be a valuable tool for online crack path investigation. [ABSTRACT FROM AUTHOR]

The (TiZrHfNbTaMo)C‐15 wt.% Co ceramics with excellent comprehensive properties were successfully prepared by vacuum liquid phase sintering. The effects of WC content on the grain size, microstructure, and mechanical properties were investigated. The results showed that WC was dissolved into (TiZrHfNbTaMo)C phase to form a seven‐component solid solution, and the independent WC phase disappeared. The addition of WC improved the wettability between the ceramic phase and the metal phase and promoted the densification of the ceramics. In addition, WC played a role in refining grains and inhibiting the grains growth to a certain extent. The comprehensive properties of ceramics were improved by solid solution strengthening and high entropy effect. When the WC content was 5 wt.%, the toughness reached the maximum of 9.41 ± 0.15 MPa·m1/2, and the hardness of the ceramic with 10 wt.% WC achieved the highest value of 18.18 ± 0.20 GPa. [ABSTRACT FROM AUTHOR]

The first figure of merit for environmental barrier coating (EBC) materials was designed through a ranking system for material properties pertaining to established EBC failure modes in service. Seven past, present, and novel EBC candidate materials were used in the figure of merit design: SiO2, Ba0.75Sr0.25Al2Si2O8 (BSAS), HfSiO4, Yb2Si2O7, Yb2SiO5, Yb2O3, and YbPO4. Utilizing compiled data from the literature, the presented figure of merit verified Yb2Si2O7 as the state‐of‐the‐art candidate with optimal EBC properties and inferred that YbPO4 should be considered as a potentially viable EBC material candidate. The figure of merit allows for a holistic comparison of EBC candidates and informs experimental and computational search efforts for next‐generation complex EBCs. Clear knowledge gaps found through this work include CaO–MgO–Al2O3–SiO2 (CMAS)‐resistant coatings, EBC lifetimes before delamination, and oxidant diffusion rates in relevant EBC microstructures. It was shown that while some materials show promise for solving a single key failure mode for EBCs (i.e., CMAS reactivity), a community‐wide goal should be placed on materials development to achieve acceptable resistance against all major failure modes, which are interconnected. Novel compositionally complex EBC materials, in addition to layered EBC architectures, show promise for the optimization of material properties for long‐lifetime EBCs in combustion environments. [ABSTRACT FROM AUTHOR]

SiCf/SiC composites have gained significant attention as a highly promising material for engine thermal structures, primarily due to their remarkable high-temperature mechanical properties, along with their low density and outstanding resistance to oxidation. In the development background of sustainable and green manufacturing technology, how to realize the low-damage machining of SiCf/SiC ceramic matrix composites is an urgent problem to be solved. In this study, the effect of dry grinding, flood grinding, minimum quantity lubrication, and nanofluid minimum quantity lubrication (MoS2 and carbon nanotubes (CNTs)) on the surface quality at different grinding depths was thoroughly investigated. The results showed that the surface quality of grinding was better, and the grinding force was lower under carbon nanotube nanofluid lubrication compared to the other four lubrication methods. Compared with dry grinding, carbon nanotube nanofluid lubrication significantly reduced the grinding temperature by 79.3%, 86.1%, and 83.5% at grinding depths of 0.2 mm, 0.4 mm, and 0.6 mm, respectively. In addition, the stable lubrication film formed by NMQL-CNTs can significantly increase the service life of grinding wheels, improve surface quality, and help obtain a surface morphology with fewer surface defects. Although brittle removal was observed in different lubrication methods, NMQL-CNTs significantly reduced surface damage due to their "filling effect" and excellent friction reduction. This study provides theoretical guidance for the low-damage processing of SiCf/SiC composites. [ABSTRACT FROM AUTHOR]

Machining composite to achieve the desired surface and sub-surface condition, whether through conventional or non-conventional techniques, presents persistent challenges due to their anisotropic thermal characteristics. These challenges escalate when dealing with ceramic matrix composites (CMC) due to their high melting and boiling temperature. This study investigates the surface and sub-surface characteristics of SiC-Al 2 O 3 CMC laser-cut components, produced using a 2 kW quasi-continuous wave laser. The influence of laser parameters such as focal position, cutting speed, number of cutting passes, average power, and assist gas type on surface and sub-surface characteristics have been investigated in detail. The laser cut samples were analysed using white light interferometer, Scanning Electron Microscopy (SEM), Energy Dispersive X-ray Spectroscopy (EDX) and 3D X-ray Computer Tomography (XCT) for both surface and sub-surface characteristics. The effect of laser process parameters on the surface composition, surface topology, and sub-surface thermal defects have been studied in detail. The results revealed that multi-pass cutting (16 pass) can be used to achieve lower thermal affected zone (~200 µm) and reduced surface roughness with an overall cutting speed of 625 mm/min. No delamination was observed with multi-pass cutting. Nitrogen was found to be the most suitable assist gas, as it prevented oxide layer formation across the laser cut SiC-Al 2 O 3 CMC surface. [ABSTRACT FROM AUTHOR]

Copyright of Journal of Aeronautical Materials is the property of Editorial Board of Journal of Aeronautical Materials and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Journal of Aeronautical Materials is the property of Editorial Board of Journal of Aeronautical Materials and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Structural analysis is a challenge for the application of ceramic matrix composite at present. On one hand, the macro-homogenization method cannot consider mesoscopic non-periodicity, therefore it is difficult to ensure accuracy. On the other hand, directly performing finite element calculations on the mesoscopic model is unacceptable since the model is too large to be solved. The super-element method is developed in the present study to balance the calculation accuracy and efficiency. The modification of the stress-strain field by the material properties is considered, and the modified strain method and the modified stress method are proposed. Establishment of the super-element method for weighted averaging of the two methods according to the degree of damage. The simulation calculations of the super-element model for the non-periodic CMC dovetail were carried out, which verified that the super-element method proposed is accurate. [ABSTRACT FROM AUTHOR]

For this study, orthogonal three dimensional (3D) woven silicon carbide (SiC) fiber (Hi-Nicalon, Hi-Nicalon Type S) -reinforced Si-CoSi2 matrix composites (SiC fiber/Si-CoSi2 composites) were fabricated and the microstructures and mechanical properties were characterized. The SiC fibers (28% fiber volume fraction) woven into orthogonal 3D fabrics and used as reinforcement were coated with chemical vapor infiltration (CVI)-carbon to control the fiber–matrix interface. The composite material infiltrated with Si-CoSi2 was produced using a melt-infiltration process. Four-point bending tests conducted at room temperature showed bending strength exceeding 300 MPa and tensile fracture strain exceeding 0.7%. Furthermore, bending strength greater than 400 MPa was found from a high-temperature four-point bending test under an Ar atmosphere. The failure mode was quasi-ductile. Fiber pull-out and fiber cross-linking were observed clearly. Melt infiltration of the Si-Co alloy caused little damage to the SiC fibers, confirming CVI-C layer protection of the fibers during melt infiltration and confirming that the layer can control mechanical properties at the fiber–matrix interface. [ABSTRACT FROM AUTHOR]

Polymer‐derived ceramics (PDCs) have become promising candidates for electromagnetic wave (EMW) absorption due to their high thermal stability, design flexibility, and versatile functionality. However, the inevitable porous structure formed during pyrolysis greatly limits its mechanical performance. In this work, Ni–Fe–C/HfO2/SiCN ceramic was prepared by simultaneously doping nickel and iron‐containing metal‐organic framework (Ni–Fe–MOF) nanoparticles and hafnium dioxide (HfO2) nanoparticles into the ceramic precursor, thereby improving its intrinsic brittle structure while granting it extraordinary EMW absorption performance. The flexural strength, flexural modulus, and Vickers hardness of Ni–Fe–C/HfO2/SiCN ceramic were 101.06 MPa, 40.19 GPa, and 13.31 GPa, respectively. These values were 1 132%, 749%, and 191% higher than those of the initial SiCN ceramics. In addition, by optimizing the content of Ni–Fe–MOF, the Ni–Fe–C/HfO2/SiCN ceramic demonstrated satisfying EMW absorption performance from 25°C to 500°C. At 25°C, the minimum reflection loss (RLmin) and effective absorption bandwidth (EAB) were −54.07 dB and 3.95 GHz, covering 94% of the X‐band at a thickness of 2.27 mm. At 500°C, the RLmin and EAB were −33.72 dB and 1.82 GHz, still covering 43% of the X‐band at a thickness of only 1.65 mm. This work provides valuable insight into the integration of mechanical and EMW absorbing functions of PDC materials. [ABSTRACT FROM AUTHOR]

The long-term periodicity and uncontrollable interface properties during the preparation process for silicon carbide fiber reinforced silicon carbide-based composites (SiCf/SiC CMC) make it difficult to thoroughly investigate their mechanical damage behavior under complex loading conditions. To delve deeper into the influence of the interface strength and toughness on the mechanical response of microscopic representative volume element (RVE) models under complex loading conditions, in this work, based on numerical simulation methods, a microscale representative volume element (RVE) with periodic symmetric boundary conditions for the material is constructed. The phase-field fracture theory and cohesive zone model are coupled to capture the brittle cracking of the matrix and the debonding behavior at the fiber/matrix interface. Simulation analysis is conducted for tensile, compressive, and shear loading as well as combined loading, and the validity of the model is verified based on the Chamis theory. Further investigation is conducted into the mechanical response behavior of the microscale RVE model under complex loading conditions in relation to the interface strength and interface toughness. The results indicate that under uniaxial loading, increasing the interface strength leads to a tighter bond between the fiber and matrix, suppressing crack initiation and propagation, and significantly increasing the material's fracture strength. However, compared to the transverse compressive strength, increasing the interface strength does not continuously enhance the strength under other loading conditions. Meanwhile, under the condition of strong interface strength of 400 MPa, an increase in the interface toughness significantly increases the transverse compressive strength of the material. When it increases from 2 J/m2 to 20 J/m2, the transverse compressive strength increases by 28.49%. Under biaxial combined loading, increasing the interface strength significantly widens the failure envelope space under σ2-τ23 combined loading; with the transition from transverse compressive stress to tensile stress, the transverse shear strength shows a trend of first increasing and then decreasing, and when the ratio of transverse shear displacement to transverse tensile/compressive displacement is −1, it reaches the maximum. This study provides strong numerical support for the investigation of the interface properties and mechanical behavior of SiCf/SiC composites under complex loading conditions, offering important references for engineering design and material performance optimization. [ABSTRACT FROM AUTHOR]

The nanoindentation test is utilized to measure the hardness and elastic modulus of various components within Ceramic Matrix Composites (CMCs), including continuous stiffness measurement (CSM) and quasi-static testing. To further characterize the elastic-plastic properties of CMCs, an efficient method is proposed by using backpropagation (BP) neural network inversion, which is based on the relationship between load and depth obtained by the nanoindentation experiment and Abaqus finite element simulation. As part of the analysis, the load-depth (p-h) curve is simplified to six characteristic parameters through the fitting of the experimental results. The pre-estimated elastic-plastic characteristics are utilized to model the nanoindentation test for CMCs. A BP neural network is used to perform deep learning on simulation data, which leads to a network structure that matches the trained parameters of the p-h curve and elastic-plastic properties. The experimental data for fiber is inputted into the network to acquire the elastic-plastic properties required in practice. The accuracy of the proposed method is verified by comparing the inversion results with the simulation outcomes. [ABSTRACT FROM AUTHOR]

Integrating ceramic matrix systems into coreless filament winding (CFW) enables the creation of sustainable, heat- and fire-resistant fiber composite lightweight structures. This study introduces a chemically bonded ceramic matrix system based on metakaolin, tailored for space applications utilizing lunar resources. The system employs acidic activation for processing with basalt/mineral fibers and alkaline activation for carbon fibers composites. Initially, the constituents of the matrix system are outlined, alongside potential synthesis pathways from lunar resources. Various formulations, incorporating different additives, are proposed. Through coupon compression testing, the most performative formulations for each activation type are selected for further investigation. The addition of zirconium silicate resulted in a higher compressive strength without significantly affecting the compressive modulus. The study then proceeds to experimentally characterize the matrix system’s viscosity. Subsequently, the processability of the proposed matrix system with CFW is demonstrated through the fabrication of generic medium-size lattice samples. Finally, these samples undergo destructive structural testing in compression. While emphasizing material development aspects, the investigation concludes that the feasibility of the proposed concept is validated through the successful fabrication and testing of generic CFW samples, affirming its potential use in space-related structural applications.

The paper explores the tensile behaviour of plain weave ceramic matrix composites (CMCs) by employing a nonlinear constitutive model for fibre tow composites, driven by in-situ X-ray computed tomography data. Through the application of a deep-learning-based image segmentation method, the study successfully identified material damage modes, including matrix cracks, fibre pull-out, and interface debonding. Three-dimensional characterisation and quantitative analyses of damage have been conducted. At the mesoscopic level, a theoretically derived nonlinear constitutive model for fibre tow composites, accounting for continuous damage to both fibre and matrix, is established by using damage data. At the macroscopic level, a unit cell model is constructed for the numerical simulation of plain weave CMCs. Material's initial defects are prone to induce crack initiation. External matrix cracks can propagate to tows, and crack deflection may occur during this process. Furthermore, adjacent microcracks have the potential to connect, forming a larger one under high stress. Theoretical results predicted by the nonlinear constitutive model for fibre tow composites under tension exhibit good agreement with test data. The built unit cell model accurately predicts the tensile mechanical behaviour of plaine weave CMCs. [ABSTRACT FROM AUTHOR]

C/C–SiC composites with four different preform structures were prepared via chemical vapor infiltration and reactive melt infiltration (RMI). The effects of preform structure on the microstructure and mechanical properties of the C/C–SiC composites were thoroughly investigated. The results indicate that the porous C/C composites with multidirectional long/short fiber‐coupling exhibited consistent pore size distribution (diameter: 5–300 µm) and periodicity pore distribution characteristics. As the effective fiber volume fraction in the loading direction of the C/C–SiC composites increased from 11.71% to 21.04%, the tensile and flexural strength significantly increased by 64.44% and 44.03%, respectively, with minimal effect on compressive and interlaminar shear properties. The introduction of Z‐direction fiber, such as stitched structure, increased the compressive and interlaminar shear strength of the composites by 10.87% and 15.67%, respectively. A theoretical predictive model of ultimate tensile strength after modification was validated for application to the C/C–SiC composites prepared by RMI, through characterization of the volume fraction of each layered unit and the content of each component. However, the presence of defects caused by the stitched structure, such as fiber bending, occupancy, and pores, reduced tensile and flexural strength by 30.45% and 28.56%, thereby impacting the effectiveness of the predictive model negatively. [ABSTRACT FROM AUTHOR]