SiC-based Composites Research Articles

Silicon Carbide-based Materials from Rice Husk

Background: Rice husk is an important agricultural waste that contains organic mass and bio-silica. Although some rice husks have been used as fuel, animal food, filler for wine fermentation, and fertilizer, the majority are discarded as agricultural waste, which does great harm to the environment. The conversion of rice husk to silicon carbide (SiC)-based materials satisfies the demand for the reutilization of solid wastes. Methods: The article reviews recent progress and patents on the SiC-based materials from rice husk. The possible development directions of the SiC-based materials from rice husks are also analyzed. Results: SiC materials with different morphologies, including microscale and nanoscale particles, nanoscale whiskers, and nanowires, can be prepared by high-temperature carbothermal reduction reaction from rice husk at the temperature of 1200-1800 °C, reaction time of 0.5-8 h, respectively. SiC-based composites, including SiC nanowires/C, Al/SiC, SiC/Si3N4, and SiC/Al2O3, can be obtained using rice husk as main source materials at 800-1800 °C. SiC-based materials exhibit great application potential in the fields of absorbents, optical devices, mechanical products, photocatalysts, semiconductors, and Li-ion batteries. Conclusion: The low cost of preparing SiC-based materials from rice husk, combining them with different compositions, and exploring new applications are important research directions in the future.

“Appropriate dressing” non-fluorination strategy: Dopamine coating CuSiF6 framework derived F-rich SiC/CuF2@C electromagnetic wave absorber

For enhancing the electromagnetic wave (EMW) absorbing performance of SiC-based composites, constructing multiple interface polarization and defects through doping highly electronegative fluoride (F) is of great significance. However, integrating F constituent into SiC composites using presently available fabrication techniques of fluorination with high-temperature sintering really remains a challenge due to the pronounced temperature sensitivity and the chemical activity of fluoride. Herein, we present a facile one-step “non-chemical fluorination” strategy on a PDA-coated CuSiF6 framework with optimal “chemical dressing”, which generated a high-performance EMW absorber (denoted as SiC/CuF2@C-5) with intense reflection loss (RLmin) of −42.74 dB and broad effective absorption bandwidth (EAB) of 5.6 GHz (9.12–14.72 GHz). The proper PDA-coated on CuSiF6in situ induced the uniform distribution of SiC and doping of electronegative F-sites in the carbon matrix, eliminating the extra fluorination procedure and preventing the gasification of fluoride. Moreover, generated abundant hetero-interfaces, and the enriched defects regulated polarization loss and impedance matching. This work presents a promising synthesis strategy for high-performance SiC-based EMW absorbing material.

In-situ construction of oxidation resistant porous Mo4.8Si3C0.6/SiC(rGO) composite PDCs served as thermal insulation components of hypersonic vehicles

Actualization of well-balanced high porosity with simultaneous increase in hardness/fracture toughness for thermal insulation composites in hypersonic aerospace vehicle components is always of great challenge. Considering significant toughening effect of unique Mo4.8Si3C0.6-SiC composites microstructure, an agile strategy is proposed to prepare porous Mo4.8Si3C0.6/SiC(rGO) polymer-derived ceramics (PDCs) via re-pyrolysis of ball-milling-induced MoSi2-SiC(rGO)p/polycarbosilane-vinyltriethoxysilane-graphene oxide (PVG) precursors blends with polystyrene (PS) as pore-forming agent. In-situ formed Mo4.8Si3C0.6-β-SiC nanocrystals, possessing eminent mechanical properties and good compatibility with SiOxCy/Cfree, can significantly strengthen interface bonding and increase disorder of ceramic network. Such effective hindrance to crack propagation moderates the inherent brittleness while retaining high hardness of SiC PDCs. Moreover, dense Mo4.8Si3C0.6-β-SiC/SiOxCy/Cfree(rGO) framework, with spontaneous regular pore structure, well balances loading/thermal insulation capacity. Particularly, samples with 10 wt.% PS exhibit outstanding mechanical performances (hardness: 5.10 GPa; fracture toughness: 2.24 MPa·m1/2; compressive strength: 58.15 MPa) and low thermal conductivity (0.8427 W·m-1·K-1). As demonstrated, products remain decent structural integrity after ablation of butane blowtorch flame for 1-20 min. The synergy oxidation with fast response of Mo4.8Si3C0.6 and durability of β-SiC facilitates great anti-oxidation ability, opening up manufacture of SiC-based composites for thermal protection system (TPS) of hypersonic vehicles and re-entry spacecraft with ultra-high speed.

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.

SiC-Based Composite Material Reinforced with Molybdenum Wire

Silicon carbide (SiC) possesses a unique combination of properties such as high mechanical strength at elevated temperatures, wear resistance, low thermal expansion coefficient, high temperature oxidation resistance, corrosion stability, radiation hardness, high chemical inertness, and thermal conductivity. Unfortunately, SiC is very brittle and cannot, therefore, be used “as is”. SiC’s crack resistance, due to the prevention of crack propagation, can be increased by the reinforcing of SiC. In this paper, a novel method for manufacturing SiC-based composites reinforced with Mo wire is developed. The composites are produced by infiltrating porous carbon blanks with molten silicon. The molten silicon reacts with the molybdenum wire embedded in the carbon blanks. As a result, a complex interfacial silicide layer with a predominant MoSi2 phase is formed on the surface of the Mo wire. In addition, a thin layer of Mo5Si3 is formed between the residual metal in the core of the wire and the disilicide. A stable bond of the interfacial layer with both the residual metal and the SiC-based ceramic matrix is observed. Mechanical tests on the obtained samples for three-point bending at 20 and 1500 °C showed quasi-plastic damage. The reinforcing elements act as stoppers for propagating cracks in the event of a matrix failure. The developed method for producing composites with a ceramic matrix reinforced with metal wire makes it possible to reduce the cost of machining and manufacturing products with complex geometric shapes. It also opens the way for broader applications of SiC-based composites.

Computational investigation of the dynamic response of silicon carbide ceramic under impact loading

It is estimated that by 2027, the global ballistic ceramic composites market would reach a value of US$3.67 billion. Many nations are increasing their military spending in order to better safeguard their military personnel, which has resulted in a tremendous increase in the market. As a result of the growing need for lighter, stronger, and harder ballistics, SiC-based composites are predicted to be the most lucrative of all ceramic materials. The study describes a finite-element model for ceramic carbide based on Johnson and Holmquist’s well-suited constitutive model for ceramics. The dynamic material tests of Strassburger et al [Strassburger, E., H. Senf, and H. Rothenhäusler, 1994 Fracture propagation during impact in three types of ceramics. Le Journal de Physique IV. 4: C8-653-C8-658.] were replicated computationally to develop further insight about the material behavior under impact loading. Materials. were simulated using the elastic properties and Johnson-Holmquist (JH-2) material models, respectively, for metal and ceramic materials. The stress distribution, damage progression, and failure of the material were accurately predicted by the results. The damage pattern, failure type, and method of failure are all examined as a result of altering projectile velocity. Computational data is utilized to verify the model’s accuracy and offer insight into the ceramic’s reaction to high strain.

Preparation of graphene nanoplatelets reinforced SiC composites by oscillatory pressure sintering

Preparation of SiC-based composites with higher relative density and mechanical properties remains challenging. Herein, we report the fabrication of a category of high performance SiC-based composites using oscillatory pressure assisted sintering (OPS) and 0.5 wt% graphene nanoplatelets (GNPs) as reinforced agents. As the sintering temperature changed from 1860 to 1950 °C, the relative density and mean grain size of the composites increased from 98.79% to 99.95% and 1.02 μm to 1.98 μm, respectively. The SiC-GNPs composites fabricated by OPS possessed much better mechanical properties in comparison with some published data obtained by other sintering methods. The optimal OPS-prepared temperature of the composites was 1920 °C; correspondingly, the relative density, flexural strength, hardness and fracture toughness were 99.72%, 488 MPa, 28.94 GPa and 6.73 MPam1/2, respectively. The crucial toughening mechanisms of crack deflection, crack branching, crack bridging and GNPs bridging were also confirmed.

Additive manufacturing of Csf/SiC composites with high fiber content by direct ink writing and liquid silicon infiltration

Direct ink writing (DIW) provides a new route to produce SiC-based composites with complex structure. In this study, we additive manufactured short carbon fiber reinforced SiC ceramic matrix composites (Csf/SiC composites) with different short carbon fiber content through direct ink writing combined with liquid silicon infiltration (LSI). The effects of short carbon fiber content on the microstructure and mechanical properties of the DIW green parts and the final Csf/SiC composites were investigated. The results showed that the Csf content played an important role in maintaining the structure of the green parts. As the Csf content increases, the dimension deviation ratio of the sample decreased at all stages. With the Csf content of 40 vol%, the final Csf/SiC composite had low free Si content and high β-SiC content. The maximum density, tensile strength and bending strength of the Csf/SiC composites were 2.88 ± 0.06 g/cm 3 , 53.68 MPa and 253.63 MPa respectively. It is believed that this study can give some understanding for the additive manufacturing of fiber reinforced ceramic matrix composites.

Thermo-mechanical behavior of SiC-based composites for gas turbine engines

The silicon carbide-based ceramic composites have been increasingly used due to their low density and ability to withstand high temperatures, improving the fuel efficiency of gas turbine aero engines. This study investigates the mechanical and thermal behavior of silicon carbide (SiC) based ceramic composites with two different particle sizes 50 µm and 10 µm, with a combination of boron carbide(B₄C) and Silicon carbide nanofillers. The ceramic composites were fabricated using the powder metallurgy technique and followed by sintering at a high temperature of 1400 °C. The oxy-acetylene flame test results show that the mass and linear ablation rates of ceramic composites with 50 µm silicon carbide were lower. The linear and mass ablation rates of the composite were reduced by 67% and 70%, respectively, by the addition of SiC filler. When the B4C filler was added, the linear and mass ablation rates both considerably dropped by 24% and 20%, respectively. Comparing the samples with the addition of SiC nanofillers to other samples, a 63% reduction in rear surface temperature was observed. The Ultrasonic test results concluded that sample 5, silicon carbide nanofiller added with 50 µm grain size SiC, shows fewer defects compared to other samples.

Low temperature seamless joining of SiC using a Ytterbium film

Monolithic SiC, for the first time, was seamless joined at a low temperature of 1200 °C using electric field-assisted sintering technology. A 300 nm Yb coating on SiC was used as the joining filler to form Yb3Si2C2 via an in-situ reaction with the SiC. A liquid phase was formed by an eutectic reaction between Yb3Si2C2 and SiC. Almost completely seamless joints were formed by the precipitated SiC grains, which were fully consolidated with the SiC matrix with the help of in-situ formed liquid phase, followed by its elimination under the uniaxial pressure. The bending strength of the seamless joint joined at 1500 °C for 15 min was as high as 257.2 ± 31.1 MPa, which was comparable to the strength of the SiC matrix. As a result, the failure occurred in the matrix indicated a sound joint was obtained. The proposed low temperature seamless joining could potentially be used for joining of SiC-based composite.

Interface Design in Lightweight SiC/TiSi2 Composites Fabricated by Reactive Infiltration Process: Interaction Phenomena between Liquid Si-Rich Si-Ti Alloys and Glassy Carbon.

To properly design and optimize liquid-assisted processes, such as reactive infiltration for fabricating lightweight and corrosion resistant SiC/TiSi2 composites, the extensive knowledge about the interfacial phenomena taking place when liquid Si-rich Si-Ti alloys are in contact with glassy carbon (GC) is of primary importance. To this end, the wettability of GC by two different Si-rich Si-Ti alloys was investigated for the first time by both the sessile and pendant drop methods at T = 1450 °C. The results obtained, in terms of contact angle values, spreading kinetics, reactivity, and developed interface microstructures, were compared with experimental observations previously obtained for the liquid Si-rich Si-Ti eutectics processed under the same operating conditions. As the main outcome, a different Si content did not seem to affect the final contact angle values. Contrarily, the final developed microstructure at the interface and the spreading kinetics were observed as weakly dependent on the composition. From a practical point of view, Si-Ti alloy compositions with a Si content falling in the simple eutectic region of the Si-Ti phase diagram might be potentially used as infiltrating materials of C- and SiC-based composites.

Solid particle erosion of a plasma spray – physical vapor deposition environmental barrier coating in a combustion environment

Environmental barrier coatings (EBCs) were developed to reduce the susceptibility of SiC-based composites to the rapid volatilization and surface recession that occurs in the presence of water vapor. Extensive research and development has been performed on EBCs, and their corresponding failure mechanisms under different environmental conditions. However, one key failure mechanism, solid particle erosion (SPE), has not been thoroughly investigated. As a result, the present work investigates the SPE behavior of a ytterbium disilicate (Yb2Si2O7) environmental barrier coating (EBC) deposited via plasma spray-physical vapor deposition (PS-PVD). Erosion testing was performed at elevated temperature (1200 °C) in a simulated combustion environment at the NASA Glenn Research Center Erosion Burner Rig Facility. Alumina (Al2O3) particles were used as the eroding media. A range of particle kinetic energies and impingement angles were investigated along with the effect of coating surface roughness. The post-erosion damage morphology was characterized using scanning electron microscopy (SEM). The SPE behavior of the PS-PVD EBC was shown to be comparable to other EBC systems reported in the literature.

Machine-Learning-Based Atomistic Model Analysis on High-Temperature Compressive Creep Properties of Amorphous Silicon Carbide.

Ceramic matrix composites (CMCs) based on silicon carbide (SiC) are used for high-temperature applications such as the hot section in turbines. For such applications, the mechanical properties at a high temperature are essential for lifetime prediction and reliability design of SiC-based CMC components. We developed an interatomic potential function based on the artificial neural network (ANN) model for silicon-carbon systems aiming at investigation of high-temperature mechanical properties of SiC materials. We confirmed that the developed ANN potential function reproduces typical material properties of the single crystals of SiC, Si, and C consistent with first-principles calculations. We also validated applicability of the developed ANN potential to a simulation of an amorphous SiC through the analysis of the radial distribution function. The developed ANN potential was applied to a series of creep test for an amorphous SiC model, focusing on the amorphous phase, which is expected to be formed in the SiC-based composites. As a result, we observed two types of creep behavior due to different atomistic mechanisms depending on the strain rate. The evaluated activation energies are lower than the experimental values in literature. This result indicates that an amorphous region can play an important role in the creep process in SiC composites.

Monitoring Damage in Nonoxide Composites at High Temperatures Using Carbon-Containing CVD SiC Monofilament Fibers as Embedded Electrical Resistance Sensors

Abstract Electrical resistance (ER) has become a technique of interest for monitoring SiC-based ceramic composites. The typical constituents of SiC fiber-reinforced SiC matrix composites, SiC, Si, and/or C, are semiconducive to some degree resulting in the fact that when damage occurs in the form of matrix cracking or fiber breakage, the resistance increases. For aero engine applications, SiC fiber reinforced SiC, sometimes Si-containing, matrix with a boron nitride (BN) interphase are often the main constituents. The resistivity of Si and SiC is highly temperature dependent. For high temperature tests, electrical lead attachment must be in a cold region which results in strong temperature effects on baseline measurements of resistance. This can be instructive as to test conditions; however, there is interest in focusing the resistance measurement in the hot section where damage monitoring is desired. The resistivity of C has a milder temperature dependence than that of Si or SiC. In addition, if the C is penetrated by damage, it would result in rapid oxidation of the C, presumably resulting in a change in resistance. One approach considered here is to insert carbon “rods” in the form of CVD SiC monofilaments with a C core to try and better sense change in resistance as it pertains to matrix crack growth in an elevated temperature test condition. The monofilaments were strategically placed in two nonoxide composite systems to understand the sensitivity of ER in damage detection at room temperature as well as elevated temperatures. Two material systems were considered for this study. The first composite system consisted of a Hi-Nicalon woven fibers, a BN interphase and a matrix processed via polymer infiltration and pyrolysis (PIP) which had SCS-6 monofilaments providing the C core. The second composite system was a melt-infiltrated (MI) prepreg laminate which contained Hi-Nicalon Type S fibers with BN interphases with SCS-ultramonofilaments providing the C core. The two composite matrix systems represent two extremes in resistance, the PIP matrix being orders of magnitude higher in resistance than the Si-containing prepreg MI matrix. Single notch tension–tension fatigue tests were performed at 815 °C to stimulate crack growth. Acoustic emission (AE) was used along with ER to monitor the damage initiation and progression during the test. Post-test microscopy was performed on the fracture specimen to understand the oxidation kinetics and carbon recession length in the monofilaments.

Effects of TiN content on the properties of hot pressed TiB2–SiC ceramics

This research intended to study the impacts of different contents of the TiN additive on the mechanical properties and microstructural features of the TiB2–SiC-based composites. Three different samples of TiB2-15 vol% SiC- x vol% TiN (x = 0, 3.5, and 7) were produced by hot-pressing at 2000 °C under 35 MPa for 120 min. Thanks to advancement of some reactions among the TiB2 surface oxides and the SiC reinforcement, two in-situ phases of TiC and SiO2 were produced during the sintering. Nevertheless, the TiN incorporation resulted in generating another in-situ compound (TiC0.3N0.7) in the relevant as-sintered ceramics. Moreover, introducing TiN significantly refined the microstructure of the composites, leading to higher mechanical characteristics. Finally, the highest flexural strength (781 MPa) and Vickers hardness (27.1 GPa) values were attained for the sample introduced by 7 vol% TiN.

A stereolithographic diamond-mixed resin slurry for complex SiC ceramic structures

Over the years, stereolithography has been successfully used to prepare complex, strong silicon carbide (SiC) structures. However, most raw materials are dark in color and therefore have broad-spectrum absorbing properties, making the curing steps during stereolithography highly inefficient. Here, diamond powders were mixed with a light-curing resin, yielding a slurry with excellent curability. The slurry was then used to prepare SiC-based composites with complex morphologies using pyrolysis and reaction melt infiltration (RMI) process. The influence of the diamond volume fraction in the slurry on each process stage was investigated. The infiltration of molten Si into diamond body during RMI was greatly enhanced compared to traditional carbon bodies. SiC ceramic-based composites with complex morphologies and a maximum strength of ∼460 MPa was prepared rapidly and efficiently. This study demonstrates the great potential of the slurry for efficiently manufacturing SiC-based composites in mechanical parts where high strength and complex structures are needed.

Synergistic influence of SiC and C3N4 reinforcements on the characteristics of ZrB2-based composites

ABSTRACT In this work, ZrB2–SiC and novel C3N4-doped ZrB2–SiC composites were manufactured at 1850°C under an external load of 40 MPa for 6 min via spark plasma sintering. The effects of C3N4 on the mechanical characteristics (flexural strength, Vickers hardness, and fracture toughness) and microstructure of the ZrB2–SiC-based composites were investigated. By adding 5 wt% g-C3N4, a fully dense ceramic composite was fabricated, compared to the C3N4-free ZrB2–SiC composite with a relative density of 95%. Removal of ZrO2 and B2O3 from the surface of ZrB2 particles via chemical reactions with C3N4, and the in-situ synthesis of ZrC and BN as new phases were studied by XRD and SEM analyses. Indentation fracture toughness, flexural strength, and Vickers hardness improved from 4.5 MPa.m1/2, 460.2 MPa and 17.4 GPa to 6.1 MPa.m1/2, 580.2 MPa and 21.2 GPa, respectively, by adding g-C3N4 to the ZrB2–SiC ceramic.

Building SiC-based composites from polycarbosilane-derived 3D-SiC scaffolds via polymer impregnation and pyrolysis (PIP)

Direct ink writing combined with subsequent polymer impregnation and pyrolysis (PIP) was adopted to prepare 3D SiC-based composites via the polymer-derived ceramic (PDC) route. Five types of 3D SiC scaffolds with different structural parameters, i.e. fillers of inert SiC powder and active Ti powder, predesigned interconnected pores and in-situ grown SiC coatings, were fabricated and employed in the following PIP process. The PIP process exhibited linear weight-increase stage in the first ten cycles, followed by the parabolic stage with decreased weight gain rate. Interconnected pores or coated SiCw in/on the 3D scaffolds increased the interfacial bonding strength, leading to improved strength of SiC-based composites. The current work demonstrated that dense 3D PDCs with adjustable macro-/micro-structures and compositions could be achieved via direct ink writing and the following PIP process.

Electron microscopy characterization of porous ZrB2–SiC–AlN composites prepared by pressureless sintering

This study explores the impact of AlN on the propagation of residual porosity and microstructure of porous ZrB2–SiC-based composites. Several ZrB2–SiC composites were fabricated with various amount of AlN by pressureless sintering method at 1900 °C. The specimens were kept at the maximum temperature for 120 min. Although the AlN-free composite possessed ~13% porosity, the incorporation of AlN to the ZrB2–SiC composites elevated this value for approximately twofold. The prepared porous samples were precisely characterized using X-ray diffraction (XRD), transmission electron microscopy (TEM), and field emission scanning electron microscopy (FESEM). XRD analysis revealed the presence of ZrB2, SiC, and C peaks in the pattern of the sample containing 5 wt% AlN. However, no Al compound could be detected therein. The thermodynamic study suggested the formation of a liquid phase comprising the SiO2–B2O3 with Al-based ingredients for the ZrB2–SiC–AlN composites. FESEM fractographs showed that the intergranular fracture was predominant in the specimens. Furthermore, the high resolution TEM images confirmed the progress of the liquid phase sintering, resulted in the formation of clean interfaces.

Transition from penetration cracking to spallation in environmental barrier coatings on ceramic composites

The article addresses the competition between driving forces for penetration cracking and for spallation in bilayer environmental barrier coatings on SiC-based composites. Coatings of interest consist of an outer rare-earth monosilicate (MS) and an inner rare-earth disilicate (DS). Finite element analysis is used to compute energy release rates (ERR) for cracking as functions of misfit strains, layer thicknesses and size of putative cracks. The results indicate that, for certain property combinations, ERRs for spallation in the DS layer exceed those for continued penetration. The implication is that penetration cracks could branch and cause coating spallation. A case study comparing bilayers of Yb- and Y-silicates reveals domains in which (i) the tolerable thickness of MS is high, but eventual spallation could potentially remove the entire DS coating along with the adjoining MS, and (ii) the tolerable thickness of MS is low, but, if it were to occur, spallation would follow a path near the MS/DS interface, leaving most of the DS intact. The behaviors prove to be sensitive to the thermal expansion coefficient of the underlying composite, even over the rather narrow range of values typical of SiC-based composites.