SiC Ceramic Composites Research Articles

3D microstructure characterization of 2D Cf-ZrB2-SiC ultra-high temperature ceramic matrix composites using X-ray microscopy

A study has been carried out to examine the impact of fibre architecture on the infiltration permeability, constituent phase volume fractions, and matrix porosity of the carbon fibre (Cf)-ZrB2-20 vol% SiC ceramic matrix composites prepared through slurry infiltration, followed by hand lay-up and hot pressing. Unidirectional (UD) Cf-fibres in 0/0° and 0/90° orientations, as well as 8H satin woven Cf-fibres, have been utilized as reinforcement in the composites, which were subsequently densified through hot pressing after infiltration. Revelation of the 3D internal structure of the composites by X-ray microscopy has facilitated a thorough qualitative and quantitative evaluation of infiltration. The fraction of matrix (ZrB2 - 20 vol% SiC) present along three orthogonal axes (X, Y and Z) of the scanned composite blocks has been calculated, with Z representing the direction of infiltration. This study has revealed that the composites processed from UD Cf-fibre preform exhibits greater infiltration, because of higher intra-bundle infiltration compared to the 8H woven Cf-fibre, and the accompanying analysis provides insight into the formation mechanisms of matrix porosities.

Additive manufacturing Cf/SiC composites with high fiber content by stereolithography combined with precursor infiltration and pyrolysis

A photocurable ceramic precursor slurry with a carbon fiber content of up to 25 vol% was prepared and carbon fiber reinforced SiC ceramic matrix composites (Cf/SiC composites) were successfully fabricated by stereolithography (SLA) combined with precursor infiltration and pyrolysis (PIP). The photocuring ability of the precursor composite slurry was investigated. The calculated result showed that the penetration depth of the slurry prepared with polycarbosilane (PCS) powder and chopped carbon fiber was 59.98 μm, which was suitable for stereolithography. In addition, the bulk density, porosity, flexural strength and micromorphology of the green body, debinding body and final Cf/SiC composites were analyzed in detail. After eight cycles of PIP, the bulk density and flexural strength of final Cf/SiC composites were 2.03 ± 0.04 g/cm3, 109.99 ± 15.05 MPa, respectively. This work provides a reference for additive manufacturing of Cf/SiC composites by stereolithography.

Effect of TiB2 content on microstructure and mechanical properties of SiC composite ceramics by solid-state spark plasma sintering

Effect of TiB2 content on microstructure and mechanical properties of SiC composite ceramics by solid-state spark plasma sintering

Spark erosion behavior in the machining of MoSi2–SiC ceramic composites for improving dimensional accuracy

The novel applications of MoSi2 and SiC as matrix and reinforcing materials in the creation of high-performance composites were investigated in this work. In particular, Spark Erosion Machining's geometric tolerances were studied in order to shed light on the technique's potential for precision manufacture in the realm of MoSi2–SiC composites. Our research focused on evaluating critical parameters and their impact on machining performance, including material removal rate, surface roughness, wear rate and drilled hole accuracy. In-depth research revealed the critical input factors that had the greatest impact on the machining procedure. Notably, parameters such as current (32%), sparking on time (23%), sparking gap voltage (12%), dielectric pressure (12%), and sparking off time (17%) emerged as the most influential factors, as determined by ANOVA analysis. These findings provide valuable insights into optimizing the Sparking EDM approach for MoSi2–SiC composite materials. This study further demonstrated the improvement in composite desirability ratings across multiple performance criteria, highlighting the effectiveness of Sparking EDM in enhancing machining outcomes (e.g., from 0.8523 to 0.9527). Correlations between the EDM's output responses were found to be quite high when geometric tolerances and the coefficient of determination (R2) were used (0.7858, 0.9625, 0.8427, 0.8678, 0.8474, 0.8368, 0.8344, 0.8671). Consider that, for the sake of a more complete understanding of the procedure's approach, the emphasis is on the methodology rather than the multifaceted metal removal mechanisms involved. This research doesn't dive further into the physical concerns of Spark Erosion Machining, but it does provide insights into the practical application of this technique in the precision manufacturing of MoSi2–SiC composite materials. For real-world medical applications such implanted devices, dental implants, surgical instruments, biological sensors and diagnostics, this study provides a valuable and encouraging approach. A validation experiment verifies the results, proving the feasibility of improved spark erosion in high-precision production. The results of this research show that EDM methods can be fine-tuned to produce ceramic composites with much greater MRR, superior surface finishes and a marked decrease in subsurface cracking and microstructural modifications. This is essential for protecting the integrity of materials used in life-saving medical equipment.

Effect of fiber orientation on tribological properties of fiber‐reinforced C/C–SiC composites mated with ceramic ball

AbstractCarbon fiber–reinforced SiC ceramic matrix composites (C/C–SiC composites) with advantages of high wear resistance and corrosion resistance are of high application potential as ceramic bearings. In this study, the frictional and wear behaviors of C/C–SiC with different fiber orientations mating with Al2O3 and SiC balls, respectively, have been investigated. Results reveal that fiber orientation effectively affects the friction and wear properties of carbon–ceramic composites in paired friction experiments with ceramic balls. In comparison to C/C–SiC with unidirectional fiber orientation, C/C–SiC pads with randomly arranged fibers exhibited a more stable coefficient of friction and lower volume wear, presenting the best performance among the pads considered herein, which may have the potential to be applied to bearing materials. The factors affecting the formation of continuous tribo‐film, which influence the comprehensive performance, are researched. It is proposed that the amount of wear debris and the formation of SiC/SiC micro‐hard frictional pairs may inhibit or promote the formation of continuous friction film. The dominant wear mechanisms for friction pairs of C/C–SiC and ceramic are abrasive wear and oxidation wear.

Microstructure and mechanical properties of SiC composite ceramics modified by (TixZr1–x)B2 solid solution

Dense SiC-(TixZr1–x)B2 composite ceramics were prepared via solid-state spark plasma sintering (SPS) by controlling the proportion of ZrB2 (in the range of 5–25 vol%). Through data fitting, a linear functional relationship was established between x and 2θ for the (TixZr1–x)B2 solid solution, which rendered it amenable to characterization analysis. The results show that the 2-D morphology of (TixZr1–x)B2 tended to transform from angular to round as the ZrB2 proportion was increased, which was beneficial in crack deflection and increasing the fracture toughness. Moreover, the growth of SiC grains around the solid solution was inhibited, which improved its mechanical properties. The composite ceramic containing 15 vol% of ZrB2 had the best mechanical properties, with its Vickers hardness, bending strength and fracture toughness reaching 26.12 GPa, 499 MPa, and 6.45 MPa•m1/2, respectively.

Лейкоксеновый концентрат как эффективное сырье для получения высокотемпературных керамических композитов на основе MAX-фаз

The authors have developed a three-stage technology for making dense Ti3SiC2–TiB2–(TiC)–SiC ceramic composites of a leucoxene concentrate being a product of previous treatment of titanium-containing sandstones. The first stage means the synthesis of agglomerated Ti3SiC2–TiB2–SiC powders which may significantly differ in SiC content. The synthesis proceeds by the method of the vacuum carbosilicothermic reduction of leucoxene concentrate using SiC as a reducing agent with addition of B4C as a solid boron-containing component. The second stage is etching the obtained powders with hydrofluoric acid in order to remove the by-products of silicide composition having been formed of impurities in leucoxene concentrate. At the final third stage, the purified Ti3SiC2–TiB2–(TiC)–SiC powders are hot-pressed in a graphite die under 30 MPa at a temperature of 1500-1550 °C. The end product is Ti3SiC2–TiB2–(TiC)–SiC ceramic composites with nearly absolute pore-free microstructure.

Matrix cracking onset stress and strain as a function of temperature, and characterisation of damage modes in SiCf/SiC ceramic matrix composites via acoustic emission

The complex damage mechanisms that accumulate within SiC f /SiC ceramic matrix composites (CMCs) subject to thermal and mechanical stress are being investigated in anticipation of the material’s introduction into high performance gas turbine engines. Acoustic emission (AE) is recognised as a leading non-destructive evaluation (NDE) tool to this end, and was used in this study to determine the so-called matrix cracking onset stress under tensile load as a function of temperature up to a maximum of 1100°C. Onset stress was interpreted using three traditional measurements based on AE energy characteristics during monotonic tests to failure. Pattern recognition (PR) analysis was performed on the AE data, revealing a specific cluster of signals that correlated closely with the initial matrix cracking region of the stress-strain curve. Taken in isolation, the onset stress of this activity was significantly lower than the conventional value. PR results were investigated further, and isolated clusters were linked to damage modes anticipated at other specific regions of the stress history. A secondary series of experiments was performed on specimens representing the individual constituents of the CMC (single-phase SiC flexural bars, Hi-Nicalon™ fibre bundles and SiC f /SiC mini-composites) in attempts to further validate the corresponding AE signal characteristics. Matrix cracking and interphase debonding/sliding damage modes could be identified consistently, while fibre breaks remained difficult to isolate under the current experimental conditions.

Microstructure and strengthening behavior in high content SiC nanowires reinforced SiC composites

AbstractIn this study, the high‐content SiCnw reinforced SiC ceramic matrix composites (SiCnw/SiC CMC) were successfully fabricated by hot pressing β‐SiC and sintering additive (Al2O3‐Y2O3) with boron nitride interphase modification SiCnw. The effects of sintering additive content and mass fraction (5–25 wt%) of SiCnw on the density, microstructure, and mechanical properties of the composites were investigated. The results showed that with the increase of sintering additives from 10 wt% to 12 wt%, the relative density of the SiCnw/SiC CMC increased from 97.3% to 98.9%, attributed to the generated Y3Al5O12 (YAG) liquid phase from the Al2O3‐Y2O3 that promotes the rearrangement and migration of SiC grains. The comprehensive performance of the obtained composite with 15 wt% SiCnw possessed the optimal flexural strength and fracture toughness of 524 ± 30.24 MPa and 12.39 ± 0.49 MPa·m1/2, respectively. Besides, the fracture mode of the composites with 25 wt% SiCnw content revealed a pseudo‐plastic fracture behavior. It concludes that the 25 wt% SiCnw/SiC CMC was toughened by the fiber pull‐outs, debonding, bridging, and crack deflection that can consume plenty of fracture energy. The strategy of SiC nanowires worked as a main bearing phase for the fabrication of SiC/SiC CMC providing critical information for understanding the mechanical behavior of high toughness and high strength SiC nanoceramic matrix composites.

A uniform rule between hardness and structure hierarchy of ceramics in both direct and inverse Hall–Petch regimes

AbstractThe MicroStructure Hierarchy Descriptor (SHD) has built a bridge in linking the structure hierarchy and properties of ceramic materials. Here, a new variable , which stands for the average of scales present in a ceramic microstructure, based on the SHD, is constructed and calibrated. It is found that the is not only related to the size scales, but also the morphological features in microstructures, due to an inheritance from the SHD. The is positively linear correlated with the average grain size d, but the relationship changes to be nonlinear when the morphology of grains is considered. In the Hall–Petch regime, the Vickers hardness HV of both, ZrO2–SiC composite ceramics and a class of high entropy metallic borides, is found to increase with the decrease of index. For the case study of ZrO2 ceramic, a uniform rule is found to be valid in both the direct and inverse Hall–Petch regimes that the varies in an opposite trend as the HV varies with d.

Mechanical and tribological properties of C/C–SiC ceramic composites with different preforms

Abstract The C/C–SiC composites were fabricated by the liquid silicon infiltration method. The mechanical and tribological properties of C/C–SiC composites were assessed and compared based on different C/C densities and the carbon fiber textile architecture. The results demonstrated that the bending and shear strengths of C/C–SiC were lower than those of C/C composites, which resulted from the carbon fibers being corroded during the process of infiltration of liquid silicon. In contrast to C/C composites, the compressive strength of C/C–SiC exhibited higher values due to the presence of SiC ceramics. Moreover, the mechanical strength of C/C composites increased gradually with the increase of the C/C preform density. The tribological properties of various C/C–SiC composites showed a stable friction phase at an intermediate braking stage. When the density of C/C preforms was around 1.78 g/cm3, the C/C–SiC composites exhibited excellent friction coefficients (0.438 and 0.465), and low wear rates (linear and weight wear rates were 0.450 µm/time and 0.123 g/cycle, respectively). Furthermore, the C/C–SiC composites fabricated with non-woven carbon fiber needling preforms showed relatively a higher friction value and wear rate than those of C/C–SiC with PANOF integral C/C preforms. Therefore, C/C–SiC composites have been considered promising friction materials for braking system applications.

Influence of post heat treatment on the high-temperature performances of multi-layered thermal/environmental barrier coatings on SiC-based composites

Multi-layered LaMgAl11O19/Yb2Si2O7/Yb2Si2O7–Si/Si (LMA/YbDS/YbDS–Si/Si) thermal/environmental barrier coatings (T/EBCs) on SiC fibre-reinforced SiC ceramic matrix composites (SiCf/SiC–CMCs) were subjected to post heat treatment at 1200 or 1350 °C for 5 h. The thermal cycling and water-vapour/oxygen corrosion of the multi-layered T/EBCs after annealing at different temperatures were studied. The results showed the thermal cycling lifetime of the 1350 °C-annealed T/EBCs was shorter than those of the 1200 °C-annealed and as-sprayed T/EBCs, while the 1350 °C-annealed T/EBCs exhibited relatively outstanding resistance to steam corrosion. The degraded thermal cycling lifetime may be associated with horizontal cracks generated at the interfaces of the LMA and YbDS layers after annealing at 1350 °C, which weakened the bonds between the coating layers. The outstanding resistance to steam corrosion of the 1350 °C-annealed T/EBCs could be attributed to the formation of a Yb3Al5O12 reaction layer with low-oxygen permeability on the upward sides of the YbDS layers in the 1350 °C-annealed T/EBCs. This could reduce the oxidation of Si inclusions within the YbDS layers, leading to less silica volatilisation.

Surface morphology and drilled hole accuracy of conductive ceramic composites Si3N4–TiN and MoSi2–SiC on EDMed surfaces

Electro-discharge machining (EDM) was employed to cut conductive ceramic composites consisting of Silicon Nitride-Titanium Nitride (Si3N4–TiN) and intermetallic ceramic composite (MoSi2–SiC), with the geometrical properties of the machined hole and the measurement of performance metrics of essential concern in the EDM process being recorded. Machining characteristics including current, spark on time, spark off time, and dielectric pressure are compared for both conductive ceramic composites. For multiple responses to geometrical errors such circularity, cylindricity and perpendicularity, as well as to performance metrics like metal removal rate (MRR), electrode wear ratio (EWR), machining time and workpiece and electrode surface integrity, spark gap time is preferable. The experimental runs to determine the optimal parameters of Si3N4–TiN and MoSi2–SiC ceramic composite are carried out using Taguchi's L9 OA based on the design of experiments (DOE). SEM with EDAX analysis of the machined surface of both composites allows for in-depth research into the machining process and a comparison of the removal mechanism and surface topography. The surface textures of 9 different holes and electrodes for ceramic composites are analysed by comparing the machined surface of the best hole with the best electrode to the machined surface of the worst hole with the worst electrode. As a consequence, the EDM process seems to be a promising method for manufacturing excellent surfaces in an electrically conductive Si3N4–TiN and MoSi2–SiC composite under the slow process parameters condition of conductive ceramic composites. This was demonstrated by the comparative analysis and establishing that was previously discussed.

Design of lightweight and antioxidant SiCnws/SiC(Mox, rGO) nanocomposite from molybdenum-modified precursors for aerospace vehicle components

Making lightweight SiC composite ceramics with good load-bearing and remarkable surficial antioxidant capacity for use in thermal protection system is challenging. In this contribution, an ingenious strategy is reported to produce SiC(Mox, rGO) nanocomposite polymer-derived ceramics (PDCs) for the first time by reactively re-pyrolyzing flexible polymolybdenumcarbosilane-vinyltriethoxysilane-graphene oxide (PMVG)/rigid SiC(Mox, rGO)p fillers blends. Highly cross-linked PMVG precursors connect up to five polycarbosilane (PCS) to optimize their formability. In-situ formed MoSi2 and Mo4.8Si3C0.6, compatible with β-SiC/SiOxCy/Cfree(rGO) matrix, can effectively strengthen interface bonding, promote nailing cracks, and even hinder β-SiC grain growth. More interestingly, using in-situ SiC nanowires (SiCnws) by Mo-containing catalyst to decorate samples is an efficient route to reinforce the ceramic network, and SiCnws/SiC(Mo0.1, rGO) nanocomposite PDCs display optimal Vickers hardness (5.19 GPa), enhanced fracture toughness (4.26 MPa·m1/2), high compressive strength (151.73 MPa), and low linear shrinkage (4.75%). Such products remain stability/integrity under flame scouring, their surface is covered by a dense SiO2 passivation layer with good self-healing capacity owing to unique non-destructive oxides of embedded MoSi2/Mo4.8Si3C0.6. This work can further provide a feasible way to overcome the critical fabrication process in lightweight porous PDCs with well-balanced high load-bearing and good thermal insulation integration for aerospace vehicle components.

Application of SiO2-coated SiC powder in stereolithography and sintering densification of SiC ceramic composites

Stereolithography additive manufacturing of SiC ceramic composites has received much attention. However, the forming efficiency and mechanical properties of their products need to be improved. This study aimed to prepare SiC ceramic composites with complex shapes and high flexural strength using a combination of digital light processing (DLP) and reactive solution infiltration process (RMI). A low-absorbance SiO2 cladding layer was formed on the surface of SiC powder through a non-homogeneous precipitation process. With the densification of the cladding layer at high temperatures, SiO2-coated SiC composite powder was used to formulate a photosensitive ceramic slurry with a solid content of 44 vol%. The resulting slurry exhibited a considerable improvement in curing thickness and rate and was used to mold ceramic green body with a single-layer slicing thickness of 100 μm using DLP. The ceramic blanks were then sintered and densified using a carbon thermal reduction combined with liquid silica infiltration (LSI) process, resulting in SiC ceramic composites with a density of 2.87 g/cm3 and an average flexural strength of 267.52 ± 2.5 MPa. Therefore, the proposed approach can reduce the manufacturing cycle and cost of SiC ceramic composites.

Xenotime-type high-entropy (Dy1/7Ho1/7Er1/7Tm1/7Yb1/7Lu1/7Y1/7)PO4: A promising thermal/environmental barrier coating material for SiCf/SiC ceramic matrix composites

Rare-earth phosphates (REPO₄) are regarded as one of the promising thermal/environmental barrier coating (T/EBC) materials for SiC_f/SiC ceramic matrix composites (SiC-CMCs) owing to their excellent resistance to water vapor and CaO–MgO–Al₂O₃–SiO₂ (CMAS). Nevertheless, a relatively high thermal conductivity (<i>κ</i>) of the REPO₄ becomes the bottleneck for their practical applications. In this work, novel xenotime-type high-entropy (Dy_1/7Ho_1/7Er_1/7Tm_1/7Yb_1/7Lu_1/7Y_1/7)PO₄ (HE (7RE_1/7)PO₄) has been designed and synthesized for the first time to solve this issue. HE (7RE_1/7)PO₄ with a homogeneous rare-earth element distribution exhibits high thermal stability up to 1750 ℃ and good chemical compatibility with SiO₂ up to 1400 ℃. In addition, the thermal expansion coefficient (TEC) of HE (7RE_1/7)PO₄ (5.96×10⁻⁶ ℃⁻¹ from room temperature (RT) to 900 ℃) is close to that of the SiC-CMCs. What is more, the thermal conductivities of HE (7RE_1/7)PO₄ (from 4.38 W·m⁻¹·K⁻¹ at 100&nbsp;℃ to 2.25 W·m⁻¹·K⁻¹ at 1300 ℃) are significantly decreased compared to those of single-component REPO₄ with the minimum value ranging from 9.90 to 4.76 W·m⁻¹·K⁻¹. These results suggest that HE (7RE_1/7)PO₄ has the potential to be applied as the T/EBC materials for the SiC-CMCs in the future.

SHS of Highly Dispersed Si3N4–SiC Ceramic Composites from Si–NaN3–Na2SiF6–C Powder Mixture

SHS of Highly Dispersed Si3N4–SiC Ceramic Composites from Si–NaN3–Na2SiF6–C Powder Mixture

Preparation and properties of Ti3SiC2 preform reinforced SiC ceramic matrix composites

Ti3SiC2 preform reinforced SiC ceramic matrix composites (Ti3SiC2/SiC) were successfully fabricated through a novel near-net-shape process strategy combining molten salt synthesis with subsequent polymer infiltration and pyrolysis (PIP) for the first time. The effects of temperature and molten salt ratio on the phase composition, pore structure, and flexural strength of Ti3SiC2 preform were investigated in detail. The morphology and microstructure evolution of the composites during the PIP process were observed by SEM and TEM. The mechanical properties, electromagnetic interference shielding effectiveness (EMI SE) and thermal conductivity of Ti3SiC2/SiC were significantly improved compared to PDC-SiC, which benefits from the connected network skeleton of Ti3SiC2 preform. The flexural strength and fracture toughness of Ti3SiC2/SiC are 198.7 MPa and 4.5 MPa∙m1/2. The EMI SE remains above 30 dB covering the entire X-band and its average value is 46.92 dB. The thermal conductivity is 6–7 W/(m·k) (25–1000 °C).

Recent progress in B4C–SiC composite ceramics: processing, microstructure, and mechanical properties

B4C–SiC composite ceramics exhibit a combination of the desirable performance of B4C and SiC, making them a better candidate material for engineering applications as structural ceramic materials.

Effect of Y2O3 Additive on Mechanical and Wear Behaviour of hBN Reinforced SiC Ceramic matrix composite

Effect of Y2O3 Additive on Mechanical and Wear Behaviour of hBN Reinforced SiC Ceramic matrix composite