Search Results (195)

In this paper, SiC and Si/SiC ceramics were fabricated using direct laser powder bed fusion with chemical vapor infiltration. Their microstructure, mechanical properties and the impacts of silicon addition were analyzed. The incorporation of silicon led to an increase in the relative density of the silicon carbide ceramics from 76.4% to 78.3% and the compression strength increased from 39 ± 13 MPa to 90 ± 8 MPa after laser powder bed fusion with chemical vapor infiltration. The melting and re-solidification of silicon allows the silicon to encapsulate the silicon carbide grains, changing the microstructure and the failure mechanism of the silicon carbide ceramics, resulting in a small amount of silicon residue. In the LPBF-CVI SiC ceramic specimen, the LPBF-formed SiC exhibits a microhardness of 24.2 ± 1.0 GPa. In LPBF-CVI Si/SiC, the spherical dual-phase structure displays a moderately increased hardness (25.9 ± 4.4 GPa), and the CVI-formed SiC exhibits a hardness of 55.3 ± 9.3 GPa. Full article

This study presents a simulation-based damage modeling and fatigue risk assessment of a reusable ceramic matrix composite thruster designed for short-duration, green bipropellant propulsion systems. The thruster is constructed from a fiber-reinforced ultra-high temperature ceramic matrix composite composed of zirconium diboride, silicon carbide, and carbon fibers. Time-resolved thermal and structural simulations are conducted on a validated thruster geometry to characterize the severity of early-stage thermal shock, stress buildup, and potential degradation pathways. Unlike traditional fatigue studies that rely on empirical fatigue constants or Paris-law-based crack-growth models, this work introduces a simulation-derived stress-margin envelope methodology that incorporates ±20% variability in temperature-dependent material strength, offering a physically grounded yet conservative risk estimate. From this, a normalized risk index is derived to evaluate the likelihood of damage initiation in critical regions over the 0–10 s firing window. The results indicate that the convergent throat region experiences a peak thermal gradient rate of approximately 380 K/s, with the normalized thermal shock index exceeding 43. Stress margins in this region collapse by 2.3 s, while margin loss in the flange curvature appears near 8 s. These findings are mapped into green, yellow, and red risk bands to classify operational safety zones. All the results assume no active cooling, representing conservative operating limits. If regenerative or ablative cooling is implemented, these margins would improve significantly. The framework established here enables a transparent, reproducible methodology for evaluating lifetime safety in ceramic propulsion nozzles and serves as a foundational tool for fatigue-resilient component design in green space engines. Full article

This study demonstrates the successful fabrication of high-performance reaction-bonded silicon carbide (RBSC) ceramics through an optimized liquid silicon infiltration (LSI) process employing multi-modal SiC particle gradation and nano-carbon black (0.6 µm) additives. By engineering porous preforms with hierarchical SiC distributions and tailored carbon sources, the resulting ceramics achieved a compressive strength of 2393 MPa and a flexural strength of 380 MPa, surpassing conventional RBSC systems. Microstructural analyses revealed homogeneous β-SiC formation and crack deflection mechanisms as key contributors to mechanical enhancement. Ultrafine SiC particles (0.5–2 µm) refined pore architectures and mediated capillary dynamics during infiltration, enabling nanoscale dispersion of residual silicon phases and minimizing interfacial defects. Compared to coarse-grained counterparts, the ultrafine SiC system exhibited a 23% increase in compressive strength, attributed to reduced sintering defects and enhanced load transfer efficiency. This work establishes a scalable strategy for designing RBSC ceramics for extreme mechanical environments, bridging material innovation with applications in high-stress structural components. Full article

In the present work, we design a laminated composite composed of molybdenum–rhenium alloy and silicon carbide ceramics for use in space reactors as a candidate structural material with neutron spectral shift properties. The influence of the internal microstructure on the mechanical properties is investigated by finite element simulation based on scale separation. The results of the study showed that the incorporation of gradient transition layers between the metallic and ceramic phases effectively mitigates thermally induced local stresses arising from mismatches in coefficients of thermal expansion. By optimizing the composition of the gradient transition layers, the stress distribution within the composite under operating conditions has been adjusted. As a result, the stress experienced by the alloy phase is significantly reduced, potentially extending the high-temperature creep rupture life. Full article

Carbon fiber-reinforced composites (CFRCs) have attracted considerable attention in recent years due to their excellent properties, enabling their use across various sectors. However, their application at high temperatures is limited by the fibers’ lack of oxidation resistance. This study demonstrates a significant advancement in enhancing the oxidation stability performance of carbon fiber-reinforced composites (CFRCs) by developing a silicon carbide (SiC) coating through the ceramization of carbon fibers using silicon (Si) powder. For the first time, this method was applied to recycled carbon fibers from CF thermoplastic composites. The key findings include the successful formation of a uniform SiC coating, with coating thickness increasing with process duration and decreasing at higher temperatures. The treated fibers exhibited substantially improved oxidation resistance, maintaining structural stability above 700 °C—markedly better than that of their uncoated counterparts. Thermogravimetric analysis confirmed that oxidation resistance varied depending on the CF/Si ratio, highlighting this parameter’s critical role. Overall, this study offers a viable pathway to enhance the thermal durability of recycled carbon fibers for high-temperature applications. Full article

Silicon carbide (SiC) ceramics were brazed with Ni-Ti fillers at 1350 °C for 10 min. The experimental results show that with the increase in Ti content in the fillers, the interface layer composed of Ni₂Si, Ni₃Si₂, graphite, and TiC becomes thinner due to the inhibition of the Ti/SiC reaction on the Ni/SiC reaction. When Ni-45Ti filler is used, TiC becomes the only phase of the interface layer in the brazing seam. The elimination of graphite improves the mechanical property of the joints. The shear strength of the SiC joints brazed by Ni-15Ti, Ni-30Ti, and Ni-45Ti fillers is 33 MPa, 92 MPa, and 125 MPa, respectively. From the point of thermodynamics, the calculated component point of the Ni/SiC reaction transition to the Ti/SiC reaction is x_Ti = 31 at.%. When the Ti content is higher than 31 at.%, the ΔG_Ni/SiC > ΔG_Ti/SiC, and TiC will be preferentially generated at the interface. Therefore, the Ni/SiC reaction is inhibited and the harmful graphite is eliminated. Full article

The reactive soldering of silicon-carbide (SiC) ceramics to a Ni-SiC composite was investigated using an Sn-5Sb-3Ti active solder and electron-beam heating at 750 °C, 850 °C and 950 °C. Wettability: The average contact angle decreased from 94 ± 4° (750 °C) to 60 ± 3° (850 °C) and further to 24 ± 2° (950 °C), demonstrating progressively improved spreading of the filler with increasing temperature. Interfacial reactions: Continuous layers of Ni₃(Sn,Sb)₄ and Ti₆(Sn,Sb)₅ formed along the Ni-SiC/filler interface, the latter confirming Ti diffusion that activates the wetting of the composite surface. Mechanical performance: Shear-lap tests on three joints per condition yielded 39 ± 6 MPa (750 °C), 27 ± 2 MPa (850 °C) and 36 ± 15 MPa (950 °C). The highest and lowest individual values at 950 °C were 51 MPa and 21 MPa, respectively. These results show that a higher soldering temperature lowers the contact angle and promotes interfacial reaction, but only a moderate improvement in average joint strength is obtained. These findings demonstrate a flux-free route to bond SiC ceramics with Ni-SiC composites, which is highly relevant for next-generation power-electronics modules and other high-temperature applications. Full article

Choosing the appropriate cutting tool material is essential for enhancing machining processes because it directly affects product quality, surface finish, dimensional accuracy, tool longevity, and overall efficiency. Different materials are used for cutting tools, i.e., for cutting inserts. Due to their high hardness and high temperature resistance, ceramics cutting inserts allow for increased cutting speeds, resulting in shorter manufacturing times and reduced costs, despite being pricier than traditional cemented carbide and facing certain technical challenges due to their brittleness. Alumina-based ceramics dominate the market, accounting for about two-thirds of usage, followed by silicon nitride and zirconia. This paper provides a comprehensive overview of recent advances in alumina ceramic materials used as cutting inserts, focusing on research conducted in the last five years to optimize static and dynamic mechanical and thermal properties, wear resistance, density, etc. They ways in which the properties are altered through the incorporation of whiskers, nanoparticles, or nanotubes; the modification of the structure; the optimization of sintering parameters; and the application of advanced sintering techniques are demonstrated. The paper also addresses sustainability, environmental impact, and the management of critical raw materials associated with cutting inserts, which pertains to the future development of cutting insert materials. Full article

Silicon carbide (SiC) materials have demonstrated promising application prospects in modern manufacturing due to their outstanding physical and chemical properties. With its process flexibility and formation feasibility, binder jetting 3D printing technology has become a crucial technical approach to meet the demand for mass production of complex, high-performance SiC components. Addressing the technical challenges of traditional manufacturing techniques in achieving high-quality, complex-shaped SiC components, this paper systematically reviews the application of binder jetting 3D printing technology in fabricating high-quality SiC-based ceramic components, with a particular focus on the regulation of key process parameters affecting SiC green body formation quality and the optimization of post-densification processes. Firstly, this paper elaborates on the powder pretreatment, green part formation process, and post-processing chain involved in this technology, establishes an evaluation index system for formation quality, and provides research directions for rapid prototyping of SiC powders. Secondly, it provides an in-depth analysis of the influence patterns of jetting parameters (e.g., jetting conditions, powder characteristics, binder properties) and various post-processing techniques on the quality of SiC-based components, along with optimization methods to enhance the dimensional accuracy and mechanical properties of 3D-printed SiC components. Furthermore, this paper systematically summarizes advanced characterization methods for evaluating formation quality and demonstrates the technology’s application potential across multiple industrial fields through representative engineering cases. Finally, it predicts the future development trends of this technology and discusses potential application expansion directions and key scientific issues in current research, aiming to provide theoretical references for promoting in-depth development of this technology. Full article

The chemical and microstructural transformation of the surface of a 31.5 vol.% ZrB₂-31.5 vol.% HfB₂-27 vol.% SiC-10 vol.% C_CNT ultrahigh-temperature ceramic sample (where C_CNT refers to carbon nanotubes) was studied under the influence of a subsonic N₂-plasma flow with the addition of 5 mol% methane, simulating aerodynamic heating in the atmosphere of Titan. As in the case of pure nitrogen flow, it was found that silicon carbide is removed from the surface. Zirconium and hafnium diborides are partially transformed into a Zr-Hf-B-C-N solid solution in the experiment conducted. XRD, Raman spectroscopy, and SEM-EDX analysis show that the presence of C₂ in the N₂-CH₄ plasma flow leads to surface carbonization (formation of a graphite- and diamond-like coating with a high proportion of amorphous carbon), resulting in significant changes in the microstructure and emissivity, potentially affecting the catalytic properties of the surface. Full article

Wafer carriers, as one of the key components in semiconductor manufacturing processes, have strict purity requirements. In this work, high-strength and high-purity SiC ceramics were fabricated using hot pressing sintering (HPS) combined with particle gradation. After hot pressing sintering with the addition of 15 wt% nano-SiC, a sintering temperature of 2200 °C, and a pressure of 40 MPa, the resultant SiC ceramics demonstrated excellent comprehensive properties with a high purity of 99.967%, a flexural strength of 458.71 MPa, a Vickers hardness of 23.31 GPa, and a fracture toughness of 4.06 MPa·m^1/2. The high-strength and high-purity SiC ceramics show potential to function as wafer carrier materials in semiconductor manufacturing processes. Full article

This paper demonstrates a novel method for preparing electrically conductive silicon carbide (SiC) ceramics by combining hot-press sintering and nitrogen pressure heat treatment. By incorporating graphite and AlN-Y₂O₃ sintering additives, conductive SiC ceramics with intergranular regions containing Y, C, and O elements were fabricated via low-temperature hot-pressing in a hot-press furnace. Following this, the samples were subjected to heat treatment in nitrogen atmosphere at varying temperatures using a gas pressure sintering furnace. It is revealed that Y and N elements were successfully dissolved into SiC grains, enhancing electrical conductivity. Additionally, localized nitridation occurred, and the Y₂Si₄CN₆ phase—a newly identified phase in nitrided regions—was discovered for the first time, potentially contributing to reduced resistivity. After heat treatment, the sample resistivity decreased significantly from an initial 3.1 × 10⁻¹ Ω·cm to the minimum of 7.56 × 10⁻³ Ω·cm. Full article

In this work, the metal salts were introduced into the resin-solvent gel system to leverage their ortho-substitution effect, thereby accelerating the polymerization-induced phase separation process. Subsequent in-situ carbonization resulted in the preparation of porous carbon materials with three-dimensional interconnected pores. By precisely tuning the parameters of the resin-solvent-metal ion system, control over the pore structure of the porous carbon was achieved, with a porosity range of 16.5% to 66.5% and a pore diameter range of 8 to 248 nm. The addition of metallic salts can simply and effectively increase the pore structure after carbonization, making the infiltration of molten silicon easier. This is beneficial to the joining process of silicon carbide ceramics. Based on these findings, a high-reliability joining technique for large-sized (135 mm × 205 mm) silicon carbide ceramics was developed. The resulting interlayer was dense and defect-free, exhibiting a joining strength of 309 ± 33 MPa and a Weibull modulus of 10.67. These results highlight the critical role of structured porous media in advancing the field of large-sized ceramic joining. Full article

In recent years, there has been increasing interest in new materials such as ceramic matrix composites (CMCs) for power generation and aerospace propulsion applications through hydrogen combustion. This study employed a deep artificial neural network (DANN) model to predict the ablation performance of CMCs in the hydrogen torch test (HTT). The study was conducted in three phases to increase the accuracy of the model’s predictions. Initially, to predict the thermal behavior of ceramic composites, two linear machine learning models were used known as Lasso and Ridge regression. In the second step, four decision tree-based ensemble machine learning models, namely random forest, gradient boosting regression, extreme gradient boosting regression, and extra tree regression, were used to improve the prediction accuracy metrics, including root mean square error (RMSE), mean absolute error (MAE), correlation coefficient (R² score), and mean absolute percentage error (MAPE), relative to the previously introduced linear models. Finally, to forecast the thermal stability of CMCs with time, an optimized DANN model with two hidden layers having rectified linear unit activation function was developed. The data collection procedure involved preparing CMCs with continuous Yttria-Stabilized Zirconia (YSZ) fibers and silicon carbide (SiC) matrix using a polymer infiltration and pyrolysis (PIP) technique. The samples were exposed to a hydrogen flame at a high heat flux of 183 W/cm² for a duration of 10 min. A good agreement between the DANN model’s predictions and experimental data with an R² score of 0.9671, RMSE of 16.45, an MAE of 14.07, and an MAPE of 3.92% confirmed the acceptability of the developed neural network model in this study. Full article

Additive manufacturing (AM) technologies allow for the creation of components with greater design flexibility. The complexity in geometry and composition can enhance functionality, while parts made from multiple materials have the capacity to deliver improved performance. Nonetheless, most multimaterial printing methods are still in their infancy and face numerous challenges. Numerous materials require individual post-treatment, and some may not be compatible with each other regarding shrinkage, melting or sintering temperatures, and interactions. In this study, we introduce a technique for producing a metal–ceramic multimaterial prototype for electronic packages through powder-bed additive manufacturing technology. Silicon carbide-based ceramic substrate was manufactured by selective laser melting, on which molybdenum-based conductive tracks were printed. The results indicated that the SiC-based samples exhibit a relatively uniform microstructure with homogeneously distributed porosity. Mo-based powder containing 5% silicon was successfully SLM-ed on the SiC layer. The microstructural and chemical analyses show that Mo reacted with Si during selective laser melting, resulting in formation of molybdenum silicides. The surface of Mo-based layer surface is smooth; however, there are few cracks on it. The Vickers hardness was measured to be 7.6 ± 1 GPa. The electrical resistivity of the conductive track is 2.8 × 10⁻⁵ Ω·m. Full article