Lightweight SiC Research Articles

PMMA light channels facilitate the additive manufacturing of complex-structured SiC reflector mirrors

The rapid manufacturing of lightweight SiC reflector mirrors has always posed a formidable challenge. We have successfully solved the problem of SiC slurry’s difficulty in vat photopolymerization by using highly transparent organic particles to construct the light channels for the first time. Through the integration of digital light processing with reaction sintering, we manufactured complex-structured SiC/Si reflector mirrors. Utilizing the light channels constructed with PMMA, ultraviolet light can effectively penetrate SiC slurry, thereby significantly enhancing the curing depth. During subsequent reaction sintering, PMMA particles induce the formation of numerous spherical silicon through dissolution-precipitation mechanism, alleviating stress concentration in the matrix and enhancing the flexural strength of SiC/Si ceramics. The method achieves significantly higher curing depth for SiC slurry and greater flexural strength for ceramic compared to similar materials. Extending the success above further, we have demonstrated their potential as high-quality products for practical applications.

In-situ formed Ni2Si into lightweight SiC(rGO) nanocomposite PDCs to boost load bearing-microwave absorption integration for complex environments

As contemporary aerospace and radar-detecting technologies evolve, load bearing-microwave absorption integration of thermal protection materials for complex environment requirements are urgent. Well known for low density, good high-temperature resistance and superior tunable dielectric properties, polymer-derived ceramics (PDCs) promisingly meet most needs of high-performance aircraft thermal protection system (TPS). Aimed at promoting practical application, we integrate in-situ formed Ni2Si into lightweight SiC(rGO) nanocomposite PDCs via re-pyrolyzing coassembled nano-Ni/SiC(rGO)p/polycarbosilane-vinyltriethoxysilane-graphene oxide (PVG) blends to enhance their mechanical and electromagnetic wave (EMW) absorbing performances. Size effect on phase transition of Ni into Ni2Si (as brazing bonding agents) accompanied by volumetric expansion, ingeniously eliminates stretching stress from PVG precursor inward shrinkage for compact framework during re-pyrolysis. In-situ generated Ni/Ni2Si/C core-shell nanostructure (similar to nodular cast iron) has good chemical compatibility with β-SiC/SiOxCy/Cfree(rGO), thereby enables composites improved compactness and toughness. More interestingly, heterogeneous interfaces/defects among Ni, Ni2Si, carbon shell, β-SiC and SiOxCy/Cfree(rGO) matrix, effectively facilitate interfacial/dipole polarization for robust EMW absorption, and lightweight SiC(rGO, Ni2Si)Ni=4% nanocomposite PDCs exhibit outstanding fracture toughness of 6.56 MPa·m1/2 and high compressive strength of 119.25 MPa. Such composite with structure-function integration maintain stable under butane blowtorch at ∼1300 °C, shedding light on a new route to mass-manufacture aerospace vehicle components.

Preparation, mechanical properties and anti-oxidation behavior of lightweight porosity-controlled SiC(rGO, xZrB2) composite PDCs for thermal protection

Achieving well-balanced light weight with simultaneous improvement in mechanical and antioxidant properties of SiC-based composite polymer-derived ceramics (PDCs) for hypersonic vehicle components is still a huge challenge. Herein, lightweight SiC(rGO, xZrB2) composite PDCs were prepared via re-pyrolyzing ball-milling-induced ZrB2-SiC(rGO)p/polycarbosilane-vinyltriethoxysilane-graphene (PCS-VTES-GO, PVG) blends. Main reinforcements consist of ZrB2, ZrO2(ZrC), ZrOSi and SiO2/β-SiC phases, among which favorable compatibility enables enhanced bear loading performances and high-temperature oxidation resistance. Rigid SiC(rGO)p tightly links with flexible PVG pyrolysis products, and co-assembles into robust SiOxCy/Cfree(rGO) matrix in framework owing to plentiful Si-dangling bonds at their interfaces. More interestingly, interfacial ZrOSi/ZrC transition zone can augment structural disorder of ceramic network, give bridging effects, strengthen interfacial compatibility, and even hinder further crack propagation for self-densification. Particularly, SiC(rGO, 30%ZrB2) composite PDCs possess optimal hardness (6.49 GPa) and outstanding fracture toughness (5.77 MPa⋅m1/2). Porous SiC(rGO, 30%ZrB2) composite PDCs own stable structure integrity within 60-min testing under butane torch flame at 1300 °C. Self-healing protective SiO2-ZrO2 glass layer avoids destructive structure and timely covers defects, thus retains good mechanical performances. Such good synergistic reinforcement and multiscale design of porosity-controlled composite, realizes integration of lightweight/good load-bearing characteristics with improved oxidation resistance for thermal protection system (TPS) of hypersonic vehicles.

Accurate modeling of thermal-optical performance for a lightweight SiC mirror

The SiC mirror has excellent structural rigidity and thermal stability, making it widely applicable in high-power optical systems. This manuscript aims to establish a coupled analysis model of thermal-optical performance for a lightweight SiC reflector under high-power laser irradiation. First, based on the Fourier principle, the transient temperature rise of the mirror is analyzed using the finite element method, considering boundary conditions such as heat source and convective radiation. A transient thermal response model for the mirror is established. Then, the reflective surface deformation is solved based on the mirror temperature field. By processing the data of node deformation, the decrease in the mirror surface shape accuracy (RMS) value is obtained. Finally, the experimental platform is built to measure the transient temperature rise and wavefront aberration change of the mirror after high-power laser excitation. Based on the deviation between the calculated data of the analysis model and the measured data, thermodynamic parameters in the analysis model are adjusted according to the principle of minimum residual. The research findings of this manuscript can be utilized for accurately predicting the temperature rise and optical degradation of SiC mirrors under high-power laser irradiation and provide a theoretical basis for the subsequent design of actively compensating methods for thermal-induced distortions.

Designed fabrication of lightweight SiC(Hf, rGO) bulk composites derived from Hafnium-modified precursors for hypersonic vehicle components

Demand for SiC-based polymer-derived ceramics (PDCs) employed as hypersonic vehicle components with light weight, high strength, excellent high-temperature/ablation resistance is increasingly urgent. Herein, bulk SiC(Hf, rGO) nanocomposite PDCs were fabricated via re-pyrolyzing ball-milling blends of unique SiC(Hf, rGO)p/polyhafniumcarbosilane-vinyltriethoxysilane-graphene oxide (PHVG). Highly cross-linked PHVG can effectively optimize compact formability and improve ceramic yield. In-situ formed HfO2 embedded in ceramic network toughens microstructure, while interfacial HfOSi increases structure disorder to improve high-temperature properties. As demonstrated, SiC(Hf, rGO) modified by 3 wt.% Hf and re-pyrolyzed at 1300 °C possess good mechanical performances including hardness (5.83 GPa), fracture toughness (4.29 MPa·m1/2), compressive strength (181.83 MPa) and flexural strength (46.55 MPa). More interestingly, self-healing HfO2(HfSiO4)/SiO2 protective layer emerging during 20 min surface ablation test at 1300 °C, timely covers defects and avoids destructive structure, thus retains stable structure and mechanical properties of specimens. Such nanocomposites can promote uses in thermal protection systems (TPS) for hypersonic vehicles against extreme high-temperature environments.

Ultra-precision grinding of light-weighted SiC aspheric mirror

Based on the approximate 3D model of light-weighted SiC aspheric mirror, the deformation and stress at different positions along the radius caused by the grinding force on the mirror surface was analysed. Then the influence of processing parameters on grinding force was experimentally studied, and the prediction model of grinding force was established. Finally, the grinding experiment of light-weighted SiC aspheric mirror was carried out. The PV value of the aspheric surface form error was 4.15μm, and the Ra of surface roughness was about 28nm. The experimental results verified the feasibility of ultra-precision forming of lightweight SiC mirror by controlling grinding force based on process parameters.

Design Optimization and Mechanical Properties of SiC Particle Reinforced Ti-Based Metallic Glass Matrix Composite.

Ti-based bulk metallic glass (BMG) alloys have attracted widespread attention due to their strong glass forming ability, high specific strength, and good corrosion resistance. However, the poor plasticity of BMGs limits their further application in the aerospace and aircraft fields, as well as others. We optimized the composition of SiC-reinforced, Ti-based metallic glass matrix composites (MGMCs) through finite element modeling (FEM). FEM of MGMCs containing irregularly shaped SiC particles with different contents was conducted. Stress and strain analyses were conducted to evaluate the effect of the particle volume fraction on the mechanical behavior of MGMCs, and an optimization value of 30% was obtained, which is conducive to plasticity improvement. Arc melting copper mold injection casting was used to verify the optimized SiC content. The results show that the electroless nickel plating treatment effectively improves the wettability between SiC particles and the amorphous matrix, enabling the successful preparation of SiC/MGMC with a volume fraction of 29.5% through traditional injection casting. The volume fraction of SiC plays a crucial role in the transition of fracture mode from splitting to shear in MGMCs. After adding lightweight SiC particles, the yield strength, plasticity, modulus, and specific strength were improved by 25%, 1471%, 46%, and 33%, indicating that the use of nickel-plated SiC particles in MGMCs is an effective strengthening and toughening method for BMGs.

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.

Microstructural tailoring, mechanical and thermal properties of SiC composites fabricated by selective laser sintering and reactive melt infiltration

Poor flowability of printable powders and long preparation cycles are the main challenges in selective laser sintering (SLS) of chopped carbon fiber reinforced silicon carbide composites (SiC composites) with complex structures. In this study, we develop an efficient and novel processing route in the fabrication of lightweight SiC composites via SLS of phenolic resin (PR) and C_f powders with the addition of α-SiC particles combined with one-step reactive melt infiltration (RMI). The effects of α-SiC addition on the microstructural evolution of the C_f/SiC/PR printed bodies, C_f/SiC/C green bodies, and derived SiC composites were investigated. The results indicate that the added α-SiC particles play an important role in enhancing the flowability of raw powders, reducing porosity, increasing the reliability of the C_f/SiC/C green bodies, and contributing to improving the microstructure homogeneity and mechanical properties of the SiC composites. The maximum density, flexural strength, and fracture toughness of the SiC composites are 2.749±0.006 g×cm⁻³, 266±5 MPa, and 3.30±0.06 MPa·m^1/2, respectively. The coefficient of thermal expansion (CTE) of the SiC composites is approximately 4.29×10⁻⁶ K⁻¹ from room temperature (RT) to 900 °C, and the thermal conductivity is in the range of 80.15-92.48 W·m⁻¹·K⁻¹ at RT. The high-temperature strength of the SiC composites increase to 287±18 MPa up to 1200 °C. This study provides a novel as well as a feasible tactic for the preparation of high-quality printable powders as well as lightweight, high strength, and high thermal conductivity SiC composites with complex structures by SLS and RMI.

In-situ formed intergranular TiB2 into lightweight SiC(rGO) composite PDCs enable elevated temperature resistance for aerospace components

Strengthening interface bonding for superior mechanical/ablation performances of SiC-based aerospace vehicle components remains a major challenge. Attractively, polycarbosilane-vinyltriethoxysilane-graphene oxide with addition of TiN/B (PVG(TiN, B)) were successfully synthesized for the first time. An ingenious route via re-pyrolyzing ball-milling-induced SiC(rGO, TiB2)p fillers/PVG(TiN, B) precursors blends was introduced to prepare lightweight SiC(rGO, TiB2) composite polymer-derived ceramics (PDCs). Interestingly, both SiC(rGO, TiB2)p and PVG(TiN, B) pyrolysis products, composed of β-SiC/SiOxCy/Cfree(rGO, TiB2), are tightly coupled by each other owing to plentiful Si-dangling bonds. In-situ formed intergranular TiB2/B4C, well compatible with amorphous ceramic network, can prevent β-SiC grain growth, strengthen interface bonding, and even hinder further crack propagation along the grain boundaries. Particularly, samples re-pyrolyzed at 1300 °C possess unique combination of good hardness (5.44 GPa), excellent fracture toughness (4.70 MPa·m1/2), high flexural strength (41.90 MPa) and outstanding compressive strength (126.33 MPa). Improved high-temperature and ablation resistance gives them distinct advantages of interlocked microstructure under exposure of butane flame. As demonstrated, SiC(rGO, TiB2) composite PDCs were developed into porous ceramics with good thermal insulation, focusing on manufacturing large-size bulk PDCs for thermal protection system of hypersonic vehicles.

Additive Manufacturing of Resilient SiC Nanowire Aerogels.

Resilient ceramic aerogels are emerging as a fascinating material that features light weight, low thermal conductivity, and recoverable compressibility, promising widespread prospects in the fields of heat insulation, catalysis, filtration, and aerospace exploration. However, the construction of the resilient ceramic aerogels with rational designed multiscale architectures aiming for tunable physical and mechanical performances remains a major challenge. Here, 3D constructed resilient SiC nanowire aerogels possessing programmed geometries and engineered mechanical properties are created via additive manufacturing. The Young's modulus of the fabricated SiC nanowire aerogel lattices are tuned systematically from 0.012 MPa to 5.800 MPa spanning over 2 orders of magnitude. More importantly, the customized lightweight and resilient SiC nanowire aerogels show a low thermal conductivity (0.046 W m-1 K-1). The present work provides another approach to the design and rapid fabrication of resilient ceramic aerogels toward flexible thermal management devices, lightweight engineered structures, and other potential applications.

The Optimization of a Convex Aspheric Lightweight SiC Mirror and Its Optical Metrology

Space telescopes with large diameters or with wide fields require convex secondary mirrors which are mounted at the front of telescope. In this paper, a convex aspheric lightweight SiC mirror and Hindle detection method are presented. A parameter optimization method is utilized in the mirror design process in which the mirror surface accuracy is taken as the objective. As the mirror has a relative high diameter-to-thickness ratio, an S-type flexure support is proposed to maintain the surface figure under gravity, thermal change and assembly error. To minimize the surface figure under these loads, the design principle is studied separately. The optical metrology is performed by the Hindle ball supported by a gravity offloading system. The tested surface had an accuracy of λ/100 root mean square (λ = 632.8 nm). In addition, the mechanical design was validated by dynamic testing.

Finite element-based machine learning approach for optimization of process parameters to produce silicon carbide ceramic complex parts

Design and fabrication of silicon carbide ceramic complex parts introduce considerable difficulties during injection molding. Due to the great importance in processing optimization, an accurate prediction on the stress and displacement is required to obtain the desired final product. In this paper, a conceptual framework on combination of finite element method (FEM) and machine learning (ML) method was developed to optimize the injection molding process, which can be used to manufacture large-aperture silicon carbide mirror. The distribution characteristics of temperature field and stress field were extracted from FEM simulation to understand the injection molding process and construct database for ML modeling. To select the most appropriate model, the predictive performance of three ML models were estimated, including generalized regression neural network (GRNN), back propagation neural network (BPNN) and extreme learning machine (ELM). The results show that the developed ELM model exhibits exceptional predictive performance and can be utilized to predict the stress and displacement of the green body. This work allows us to obtain reasonable technique parameters with particular attention to the loading speed and provides some fundamental guidance for the fabrication of lightweight SiC ceramic optical mirror.

Preparation and characterization of lightweight SiC frameworks by connecting SiC fibers with SiC joints

The increasing energy challenges and the rapidly developing astronautic technology require thermal insulators with low density and thermal conductivity, high–temperature thermal, chemical and mechanical stabilities. Herein, highly porous SiC frameworks were fabricated through procedures of assembling SiC fibers and formation of SiC joints by carbothermal reduction, which were named as SiC–bonded SiC fiber (SBSF) composites. The porosities were controlled in the range of 76–93% by varying aspect ratios of the SiC fibers. The SBSF composites exhibited outstanding corrosion resistance, oxidation resistance, and high–temperature thermal stability, as the inherent advantages of SiC ceramics. High strength and reversible compressibility were obtained in the out–of–plane compression load tests, and low thermal conductivity of 0.036–0.102 W/m · K at 25–800 °C was achieved. The results of this study suggest that the SBSF composites are a good candidate for high–temperature thermal insulators.

In-situ fabrication of lightweight SiC(Al, rGO) bulk ceramics derived from silicon oxycarbide for aerospace components

Abstract An ingenious strategy to prepare in-situ formed SiC(Al, rGO) bulk polymer-derived ceramics (PDCs) from re-pyrolyzing SiC(Al, rGO)p/polyaluminocarbosilane-vinyltriethoxysilane-graphene oxide (PACS-VTES-GO, PAVG) blends is highlighted. Flexible PAVG modified by Al with highly cross-linked structure effectively improves molecular weight and formability of precursors. Rigid SiC(Al, rGO)p fillers provide high mechanical properties owing to their unique microstructure which is consistent with SiC(Al, rGO) bulk PDCs. β-SiC nanocrystals are well dispersed in amorphous SiOxCy/Cfree, and rGO exhibits good compatibility with SiOxCy/Cfree. Besides, possible Al2O3 is beneficial to relaxing thermal stress at β-SiC nanocrystalline boundaries. Interestingly, introduction of Al could avoid coarsening of β-SiC grains to enhance elevated temperature resistance. Furthermore, effect of re-pyrolysis temperature on the formation and microstructure of SiC(Al, rGO) bulk PDCs was also investigated. Particularly, lightweight samples re-pyrolyzed at 1300 °C display optimal fracture toughness (3.32 MPa m1/2), compressive strength (177.16 MPa) and flexural strength (51.25 MPa), high ceramic yield (94.46%) and low linear shrinkage (4.38%), by far superior to those of most PDCs. As treated via precursor infiltration and pyrolysis (PIP) route and heated by butane gun flame in air, such products possess stable structures under elevated temperatures and have potential emerging uses in aerospace components.

Making lightweight SiC(rGO, xMoSi2) bulk ceramics via polymeric precursor route

AbstractUnique properties of MoSi2 open new opportunities for preparing bulk polymer‐derived ceramics (PDCs) displaying favorable structural‐functional capabilities. Herein, an ingenious production route via re‐pyrolysis process of ball‐milling‐induced rigid SiC(rGO, xMoSi2)p fillers/flexible polycarbosilane‐vinyltriethoxysilane‐graphene oxide (PCS‐VTES‐GO, PVG) precursors blends is proposed to obtain in situ formed SiC(rGO, xMoSi2) bulk PDCs. Interestingly, the possible dense β‐SiC/SiOxCy/Cfree(rGO, xMoSi2) framework suffers load and tiny microsized pores relaxes stress, which is beneficial to providing optimized hardness and fracture toughness, ceramic yield, and linear shrinkage. Attractively, MoSi2 prominently enhances thermal and electrical conductivities of the products owing to increased continuity and compactness. To the best of our knowledge, lightweight SiC(rGO, 20%MoSi2) bulk PDCs own brilliant ceramic yield (92.13%), liner shrinkage (6.69%), hardness (10.34 GPa), fracture toughness (4.35 Mpa·m1/2), and thermal conductivity (8.57 W·m–1·K–1), opening potential emerging uses in aerospace fields.

Orthogonally structured graphene nanointerface for lightweight SiC nanowire-based nanocomposites with enhanced mechanical and electromagnetic-interference shielding properties

Interface design is an effective strategy for developing advanced composite materials, especially nanocomposites with optimized structural nanointerfaces with better properties. Herein, smart orthogonally structured graphene (OSG) nanointerfaces with designed multi-functions were fabricated for the first time in three-dimensional (3D) SiC nanowires (SiCnw) foam to yield hybrid nano-preforms. The as-obtained OSG nanointerfaces showed excellent electrical conductivity and unique orthogonal structure, which did not only act as highways for electron transport but also as smart interfacial energy traps for the capture and deflection of cracks. Hence, hybrid nano-preforms provided dual outstanding advantage over conventional SiCnw foam for reinforcing pyrocarbon (PyC) and yield materials with higher mechanical strength and electromagnetic-interference (EMI) shielding effectiveness. Compared to baseline without nanointerface, the 0.12 wt% OSG nanointerface significantly increased the flexural strength and EMI shielding effectiveness by 101% and 54%, respectively. These findings demonstrated the promising prospects of OSG nanointerface as necessary components for advanced mechanical-strong and high-performance EMI shielding nanocomposites.

Optimal design of a Φ760 mm lightweight SiC mirror and the flexural mount for a space telescope.

A flexural support technique for lightweighted Primary Mirror Assembly (PMA) of a space telescope is presented in this article. The proposed three-point flexural mount based on a cartwheel flexure can maintain the surface figure of the PMA in a horizontal optical testing layout. The on-orbit surface error of the PMA causes significant degradation in image quality. On-ground optical testing cannot determine the zero-gravity figure of the PMA due to surface distortion by gravity. We unveiled the crucial fact that through a delicate mounting structure design, the surface figure can remain constant precisely without inducing distinguishable astigmatism when PMA rotates with respect to the optical axis, and the figure can be considered as the zero-gravity surface figure on the orbit. A design case is described to show the lightweight design of a SiC mirror and the optimal flexural mounting. Topology optimization and integrated opto-mechanical analysis using the finite element method are utilized in the design process. The Primary Mirror and mounting structures were fabricated and assembled. After the PMA mirror surface was polished to λ/50 RMS, optical testing in different clocking configurations was performed, respectively, through rotating the PMA by multiple angles. Test results show that the surface figure remained invariant, indicating that gravity release on the orbit will not cause an additional surface error. Vibration tests including sweep sine and random vibration were also performed to validate the mechanical design. The requirements for the mounting technique in space were qualified.

Local Degradation Mechanisms by Tarnishing of Protected Silver Mirror Layers Studied by Combined Surface Analysis.

In this work, we addressed the local degradation mechanisms limiting the prelaunch environmental durability of thin-layered silver stacks for demanding space mirror applications. Local initiation and propagation of tarnishing were studied by combined surface and interface analysis on model stack samples consisting of thin silver layers supported on lightweight SiC substrates and protected by thin SiO2 overcoats, deposited by cathodic magnetron sputtering and submitted to accelerated aging in gaseous H2S. The results show that tarnishing is locally initiated by the formation of Ag2S columns erupting above the stack surface. Ag2S growth is promoted at high aspect ratio defects (surface pores) of the SiC substrate as a result of an imperfect protection by the SiO2 overcoat. Channels most likely connect the silver layer to its environment through the protection layer, which enables local H2S entry and Ag2S growth. The silver sulfide columns grow in number and size eventually leading to coalescence with increasing H2S exposure. In more advanced stages, tarnishing slows down owing to saturation of all pre-existing imperfectly protected sites of preferential sulfidation. However, it progresses radially at the basis of the Ag2S columns underneath the protection layer, consuming the metallic silver layer and deteriorating the protecting overcoat.

Deposition of thick Si coating with low residual stress on SiC ceramics by fabricating multilayer with compressive/tensile stress layer-pairs

Surface modification can significantly improve surface properties of lightweight SiC ceramics as optical component for Large Space Optical Telescope. Usually, thick Si-modified coatings can be applied to cover surface defects and decrease polishing cost/time of SiC ceramics. However, it is one great challenge for depositing thick Si-coating with low residual stress on large-scale SiC ceramics by physical vapor deposition (PVD) method because too large residual stress often leads to the stress cracking of thick coatings. Here, silicon multilayer with alternate compressive/tensile stress layer pairs was designed and deposited alternately onto SiC substrates in order to prepare thick Si-coatings with low residual stresses. The silicon multilayer with compressive/tensile stress pairs were obtained by plasma ion assisted deposition and electron beam physical vapor deposition, respectively. The total thickness of as-deposited Si-multilayer can reach as much as 20μm. Remarkably, the residual stress of silicon-multilayer tends to be negligible. Meanwhile, thick Si-coating bonds tightly with SiC substrate, and shows ultra-flat mirror surface with surface roughness of 0.69nm RMS after polishing. It is demonstrated that silicon multilayer with low residual stress is a promising way to realize surface modification of SiC ceramics for optical mirror application.