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ISSN 1005-0302
CN 21-1315/TG
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      05 December 2019, Volume 35 Issue 12 Previous Issue    Next Issue
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    Orginal Article
    A review of third generation SiC fibers and SiCf/SiC composites
    Pengren Wang, Fengqi Liu, Hao Wang, Hao Li, Yanzi Gou
    J. Mater. Sci. Technol., 2019, 35 (12): 2743-2750.  DOI: 10.1016/j.jmst.2019.07.020
    Abstract   HTML   PDF

    Compared with the first and second generations SiC fibers, the third generation SiC fibers have obvious improvement in heat-resistance, oxidation-resistance and creep-resistance, which promote the development of SiCf/SiC composite materials. Therefore, the third generation SiC fibers have more advantages and broader prospects in engineering applications. In this paper, the fabrication and properties of the third generation SiC fibers are compared and discussed. The preparation processes of the third generation SiC fibers reinforced SiC matrix composites and their application in aeroengine and nuclear energy fields are summarized, while their future development is prospected as well.

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    Additive manufacturing alumina components with lattice structures by digital light processing technique
    Qingfeng Zeng, Changhao Yang, Dingyi Tang, Jiayao Li, Zhiqiang Feng, Jiantao Liu, Kang Guan
    J. Mater. Sci. Technol., 2019, 35 (12): 2751-2755.  DOI: 10.1016/j.jmst.2019.08.001Get rights and content
    Abstract   HTML   PDF

    Digital light processing technique was applied to manufacture alumina ceramic parts with two types of lattice structure units, i.e. vertex interconnect structure and edge structure. The internal porosity of the unit is 40%. The printed parts were sintered and the grain size is about 1.1?μm. The bending strength of the vertex interconnect structure is much larger than that of the edge structure. Materials genome initiative (MGI) aims to digital design and intelligent manufacture for advanced components. This research shows us an example to achieve this goal.

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    Preparation and characterization of pure SiC ceramics by high temperature physical vapor transport induced by seeding with nano SiC particles
    Yuchen Deng, Yaming Zhang, Nanlong Zhang, Qiang Zhi, , Jianfeng Yang
    J. Mater. Sci. Technol., 2019, 35 (12): 2756-2760.  DOI: 10.1016/j.jmst.2019.04.039
    Abstract   HTML   PDF

    High temperature physical vapor transport (HTPVT) was employed to grow polycrystalline SiC ceramics with high density and purity, induced by nano SiC particles as seeds. The obtained SiC ceramics were identified as 6H-SiC with a mainly preferred orientation along the (0 0 0 6) plane, and an obvious refinement of grain size was demonstrated for the SiC seeds. Mean grain sizes of the obtained SiC ceramics were 112?μm and 314?μm, by using the SiC seeds with the mean particle size of 50?nm and 500?nm, respectively, which were obviously smaller than that of the seed-free sample (960?μm). The samples obtained with the seeds also demonstrated enhanced flexural strength and hardness, attributing to the reduced mean grain size. Furthermore, SiC ceramics without seeds via HTPVT exhibited a high thermal conductivity of 242?W·(m·K)-1 at room temperature due to the highly preferred orientation. While the degree of preferred orientation of seed-induced samples was lower, the thermal conductivity of SiC ceramics induced by seeding still maintained at least 200?W·(m·K)-1 at room temperature, this level was much higher than most other methods. Therefore, seed-induced method appears to be an effective way to control structures and behavior of SiC ceramics through HTPVT.

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    Fabrication and oxidation resistance of silicon nitride fiber reinforced silica matrix wave-transparent composites
    Xuejin Yang, Bin Li, Duan Li, Changwei Shao, Changrui Zhang, Chunrong Zou, Kun Liu
    J. Mater. Sci. Technol., 2019, 35 (12): 2761-2766.  DOI: 10.1016/j.jmst.2019.05.068
    Abstract   HTML   PDF

    Wave-transparent ceramic matrix composites for the high temperature use should possess excellent oxidation resistance. In this work, Si3N4f/SiO2 composites with different fiber content were fabricated by filament winding and sol gel method. The oxidation resistance was investigated by tracking the response of flexural strength to the testing temperature. The results show that the flexural strength and toughness of the composites with fiber content of over 37% can reach high levels at around 175.0?MPa and 6.2?MPa?m1/2, respectively. After 1?h oxidation at 1100?°C, the flexural strength drops a lot but can still reach 114.4?MPa, which is high enough to ensure the safety of structures. However, when the oxidation temperature rises to 1200-1400?°C, the flexural strengths continue to fall to a relatively low level at 50.0-66.4?MPa. The degradation at high temperatures is caused by the combination of over strong interfacial bonding, the damage of fiber and the crystallization of silica matrix.

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    Preparation and interface modification of Si3N4f/SiO2 composites
    Yubo Hou, Xuejin Yang, Bin Li, Duan Li, Shitao Gao, Zhongshuai Wu
    J. Mater. Sci. Technol., 2019, 35 (12): 2767-2771.  DOI: 10.1016/j.jmst.2019.05.069
    Abstract   HTML   PDF

    In order to modify the interface, SiON coating was introduced on the surface of silicon nitride fiber by perhydropolysilazane conversion method. Si3N4f/SiO2 and Si3N4f/SiONc/SiO2 composites were prepared by sol-gel method to explore the influence of SiON coating on the mechanical properties of composites. The results show that with the protection of SiON coating, Si3N4 fiber enjoys a strength increase of up to 24.1% and Si3N4f/SiONc/SiO2 composites have a tensile strength of 170.5?MPa and a modulus of 26.9?GPa, respectively. After 1000?°C annealing in air for 1?h, Si3N4f/SiONc/SiO2 composites retain 65.0% of their original strength and show a better toughness than Si3N4f/SiO2 composites. The improvement of mechanical properties is attributing to the healing effect of SiON coating as well as its intermediate coefficient of thermal expansion between Si3N4 fiber and SiO2 matrix.

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    Salt-fog corrosion behavior of C/SiC and its effect on ablation resistance
    Su Cheng, Xing Zhao, Guang Yang, Yiguang Wang
    J. Mater. Sci. Technol., 2019, 35 (12): 2772-2777.  DOI: 10.1016/j.jmst.2019.04.037
    Abstract   HTML   PDF

    Carbon fiber-reinforced silicon carbide (C/SiC) composites are significantly important candidates for thermal protection materials. The corrosion mechanism of C/SiC composite materials is the basis of their optimization and application. In this study, structural evolution of C/SiC composites fabricated by chemical vapor infiltration was investigated in the salt-fog storage environment. Furthermore, the effect of salt-fog on their ablation behaviors under oxyacetylene flame environment was studied. The ablation morphologies and corrosion mechanisms of C/SiC composites were analyzed and discussed. The results indicated that silica layer with size of c.a. 20 nm was formed on the surface of composite. The extent of corrosion in salt fog was limited, and it had little effect on the ablation behavior of the C/SiC composites, as well on the tensile strength and bending strength.

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    Low thermal conductivity and high porosity ZrC and HfC ceramics prepared by in-situ reduction reaction/partial sintering method for ultrahigh temperature applications
    Heng Chen, Huimin Xiang, Fu-Zhi Dai, Jiachen Liu, Yanchun Zhou
    J. Mater. Sci. Technol., 2019, 35 (12): 2778-2784.  DOI: 10.1016/j.jmst.2019.05.044
    Abstract   HTML   PDF

    Porous ultra-high temperature ceramics (UHTCs) are potential candidates as high-temperature thermal insulation materials. However, high thermal conductivity is the main obstacle to the application of porous UHTCs. In order to address this problem, herein, a new method combining in-situ reaction and partial sintering has been developed for preparing porous ZrC and HfC with low conductivity. In this process, porous ZrC and HfC are directly obtained from ZrO2/C and HfO2/C green bodies without adding any pore-forming agents. The release of reaction gas can not only increase the porosity but also block the shrinkage. The as-prepared porous ZrC and HfC exhibit homogeneous porous microstructure with grain sizes in the range of 300-600?nm and 200-500?nm, high porosity of 68.74% and 77.82%, low room temperature thermal conductivity of 1.12 and 1.01?W·m-1?K-1, and compressive strength of 8.28 and 5.51?MPa, respectively. These features render porous ZrC and HfC promising as light-weight thermal insulation materials for ultrahigh temperature applications. Furthermore, the feasibility of this method has been demonstrated and porous NbC, TaC as well as TiC have been prepared by this method.

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    Ablation characteristics of mosaic structure ZrC-SiC coatings on low-density, porous C/C composites
    Yonglong Xu, Wei Sun, Xiang Xiong, Fuqun Liu, Xingang Luan
    J. Mater. Sci. Technol., 2019, 35 (12): 2785-2798.  DOI: 10.1016/j.jmst.2019.08.004
    Abstract   HTML   PDF

    Mosaic structure ZrC-SiC coatings were fabricated on low-density, porous C/C composites via thermal evaporation and an in-situ method. ZrC was packed in a typical lamellar mode, and the mosaic structure was formed by the deposition of Zr and Si atoms on the shallow surface of the porous C/C composites. Ablation analysis showed that the defects in the coatings originate from the boundary between the ZrC and holes created by the consumption of SiC at 2500?°C. After ablation for 200?s at 3000?°C, a dense ZrO2 layer formed on the coating surface, and the defects were sealed owing to the continuous supply of ablative components. The mass and line ablation rates of the ZrC-SiC coatings were -0.46?±?0.15?mg?cm-2·s-1 and -1.00± 0.04?μm?s-1, respectively.

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    Selective growth of SiC nanowires in interlaminar matrix for improving in-plane strengths of laminated Carbon/Carbon composites
    Qiang Song, Qingliang Shen, Qiangang Fu, Hejun Li
    J. Mater. Sci. Technol., 2019, 35 (12): 2799-2808.  DOI: 10.1016/j.jmst.2019.07.001
    Abstract   HTML   PDF

    β-SiC nanowires (SiCNWs) were selectively grown in the interlaminar matrix with a volume fraction of 0.65% by applying a pyrocarbon coating on carbon fibers, which realizes the proper reinforcement of C/C composites. The thickness of the pyrocarbon is optimized to 0.5?μm based on the analysis of in-situ fiber strengths with the fracture mirror method. The pyrocarbon coating increased the in-situ fiber strength by ˜7% and prevent brittle fracture of the composites. Compared with C/C, the interlaminar shear and flexural strength of SiCNW-C/C (10.06?MPa and 162.44?MPa) increase by 158% and 57%. Incorporating SiCNWs changes the crystallite orientations and refines the crystallite size of pyrocarbon matrix. The functions of SiCNWs vary with their loading density. When SiCNWs are sufficient in the matrix, they help reinforcing and improving the critical failure stress of the matrix. When their density decreases to a certain degree, SiCNWs help changing the crystallite orientations of pyrocarbon and toughening the matrix.

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    Mechanical and electromagnetic wave absorption properties of Cf-Si3N4 ceramics with PyC/SiC interphases
    Wei Zhou, Lan Long, Yang Li
    J. Mater. Sci. Technol., 2019, 35 (12): 2809-2813.  DOI: 10.1016/j.jmst.2019.07.002
    Abstract   HTML   PDF
    Aim

    ing to obtain microwave absorbing materials with excellent mechanical and microwave absorption properties, carbon fiber reinforced Si3N4 ceramics (Cf-Si3N4) with pyrolytic carbon (PyC)/SiC interphases were fabricated by gel casting. The influences of carbon fibers content on mechanical and microwave absorption properties of as-prepared Si3N4 based ceramics were investigated.

    Results

    show that chemical compatibility between carbon fibers and Si3N4 matrix in high temperature environment can be significantly improved after introduction of PyC/SiC interphases. As carbon fibers content increases from 0 to 4?wt%, flexural strength of Si3N4 based ceramics decreases slightly while fracture toughness obviously increases. Moreover, both the real and imaginary parts of complex permittivity increase with the rising of carbon fibers content within the frequency range of 8.2-12.4?GHz. Investigation of microwave absorption shows that the microwave attenuation ability of Cf-Si3N4 ceramics with PyC/SiC interphases is remarkably enhanced compared with pure Si3N4 ceramics. Effective absorption bandwidth (<-10?dB) of 10.17-12.4?GHz and the minimum reflection less of -19.6?dB are obtained for Si3N4 ceramics with 4?wt% carbon fibers in 2.0?mm thickness. Cf-Si3N4 ceramics with PyC/SiC interphases are promising candidates for microwave absorbing materials with favorable mechanical property.

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    Composite ceramics thermal barrier coatings of yttria stabilized zirconia for aero-engines
    Qiaomu Liu, Shunzhou Huang, Aijie He
    J. Mater. Sci. Technol., 2019, 35 (12): 2814-2823.  DOI: 10.1016/j.jmst.2019.08.003
    Abstract   HTML   PDF

    Composite ceramics thermal barrier coatings (TBCs) are widely used in the aero-engines field due to their excellent thermal insulation, which improves the service life and durability of the inherent hot components. The most typical, successful and widely used TBCs material is yttria stabilized zirconia (YSZ). In this paper, fabrication methods, coating structures, materials, failure mechanism and major challenges of YSZ TBCs are introduced and reviewed. The research tendency is put forward as well. This review provides a good understanding of the YSZ TBCs and inspires researchers to discover versatile ideas to improve the TBCs systems.

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    Microstructures and mechanical behaviors of CVI-based C/C composites containing h-BN powdered additives
    Peng Xiao, Zhichao Li, Zeyan Liu, Zhuan Li, Bengu Zhang, Jinwei Li, Yang Li
    J. Mater. Sci. Technol., 2019, 35 (12): 2824-2831.  DOI: 10.1016/j.jmst.2019.07.003
    Abstract   HTML   PDF

    Hexagonal boron nitride (h-BN) powders were introduced into carbon fiber preform by powder addition and subsequent combined with chemical vapor infiltration (CVI) for densification to prepare carbon fiber reinforced/carbon and boron nitride dual matrix composites (C/C-BN). Microstructures and mechanical properties of C/C composites with three different volume contents of h-BN powders were investigated in comparison to pure C/C composites. Results indicated that the introduction of h-BN powders into C/C composites significantly reduced the size of PyC and the anisotropy of thermal contraction in matrix, leading to a gradual disappearance of ring defects as the h-BN content increased. In addition, an enhanced interfacial bonding between fiber and matrix obtained due to higher-textured PyC and rougher fiber surface. Thereby, the flexural strengths and modulus of as-prepared composites decreased firstly and then increased, while the impact toughness presented a decreasing tendency as the content of BN powders increased. Furthermore, with the increasing of h-BN content, anisotropies of compressive properties were weakened, and the compressive strength of C/C-BN composites were always higher than that of pure C/C composit. However, when C/C composites modified by 13.5?vol% content of h-BN, excessive loose BN aggregates appeared in C/C-BN composites, leading to a relatively slight reduction of compressive strength.

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    Electromagnetic interference shielding properties of polymer derived SiC-Si3N4 composite ceramics
    Xiaoling Liu, Xiaowei Yin, Wenyan Duan, Fang Ye, Xinliang Li
    J. Mater. Sci. Technol., 2019, 35 (12): 2832-2839.  DOI: 10.1016/j.jmst.2019.07.006
    Abstract   HTML   PDF

    SiC-Si3N4 composite ceramics are successfully fabricated by pyrolysis of ferrocene-modified polycarbosilane (PCS) mixed with inert filler Si3N4 powders, followed by thermal treatment from 1100?°C to 1400?°C in Ar atmosphere. The porosity of SiC-Si3N4 ceramics decreases to 6.4% due to the addition of inert filler Si3N4. And the content and crystallization degree of free carbon and SiC derived from PCS are improved simultaneously with the increase of thermal treatment temperature. Finally, the free carbon and SiC interconnect, forming the conductive network. As a result, the electromagnetic interference (EMI) shielding performance of the as-prepared ceramic annealed at 1400?°C reaches up to 36?dB, meaning more than 99.9% of EM energy is shielded. The low porosity and high EMI shielding performance enable SiC-Si3N4 composite ceramics to be a promising electromagnetic shielding and structural material.

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    Reactive sintering of B4C-TaB2 ceramics via carbide boronizing: Reaction process, microstructure and mechanical properties
    Junfeng Gu, Ji Zou, Peiyan Ma, Hao Wang, Jinyong Zhang, Weimin Wang, Zhengyi Fu
    J. Mater. Sci. Technol., 2019, 35 (12): 2840-2850.  DOI: 10.1016/j.jmst.2019.04.029
    Abstract   HTML   PDF

    Carbide boronizing is a promising approach to obtain fine grained boron carbide based ceramics with improved mechanical properties. In this work, reaction process, microstructural characteristics and mechanical properties of BxC-TaB2 (x?=?3.7, 4.9, 7.1) ceramics were comprehensively investigated via this method. Dense BxC-TaB2 ceramics with refined microstructure were obtained from submicro tantalum carbide and boron powder mixtures at 1800?°C/50?MPa/5?min by spark plasma sintering. The stoichiometry of boron carbide was determined from lattice parameters and Raman shift. It was found that uniformly distributed TaB2 grains in the BxC matrix is favor of the densification process and restricting grain growth. Besides, planar defects with high density were observed from the as-formed B7.1C grains and transient stress was considered to contribute to the densification involved with plastic deformation. Microstructural observations indicate the dissolution of oxygen in the TaB2 lattice and most of the B7.1C/TaB2 phase boundaries were clean. Owing to the highly faulted structure and finer grain size, as-obtained BxC-TaB2 ceramics exhibit high Vickers hardness (33.3-34.4?GPa at 9.8?N) and relatively high flexural strength ranging from 440 to 502?MPa.

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    Initial nucleation of amorphous Si-B-C-N ceramics derived from polymer-precursors
    Ling-yan Li, Hui Gu, Vesna Šrot, Peter van Aken, Joachim Bill
    J. Mater. Sci. Technol., 2019, 35 (12): 2851-2858.  DOI: 10.1016/j.jmst.2019.07.004
    Abstract   HTML   PDF

    Nucleation behavior of amorphous Si–B–C–N ceramics derived from boron-modified polyvinylsilazane procusors was systematically investigated by transmission electron microscopy (TEM) combined with spatially-resolved electron energy-loss spectroscopy (EELS) analysis. The ceramics were pyrolyzed at 1000°C followed by further annealing in N2, and SiC nano-crystallites start to emerge at 1200°C and dominate at 1500°C. Observed by high-angle annular dark-field imaging, bright and dark clusters were revealed as universal nano-structured features in ceramic matrices before and after nucleation, and the growth of cluster size saturated before reaching 5nm at 1400°C. EELS analysis demonstrated the gradual development of bonding structures successively into SiC, graphetic BNCx and Si3N4 phases, as well as a constant presence of unexpected oxygen in the matrices. Furthermore, EELS profiling revealed the bright SiC clusters and less bright Si3N4-like clusters at 1200–1400°C. Since the amorphous matrix has already phase separated into SiCN and carbon clusters, another phase separation of SiCN into SiC and Si3N4-like clusters might occur by annealing to accompany their nucleation and growth, albeit one crystallized and another remained in amorphous structure. Hinderance of the cluster growth and further crystallization was owing to the formation of BNCx layers that developed between SiC and Si3N4-like clusters as well as from the excessive oxygen to form the stable SiO2.

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    Weave geometry generation avoiding interferences for mesoscale RVEs
    Daniel Höwer, Shengkai Yu, Trenton M. Ricks, Brett A. Bednarcyk, Evan J. Pineda, Bertram Stier, Stefanie Reese, Jaan-Willem Simon
    J. Mater. Sci. Technol., 2019, 35 (12): 2869-2882.  DOI: 10.1016/j.jmst.2018.12.027
    Abstract   HTML   PDF

    An algorithm which allows the generation of representative volume elements (RVEs) for complex woven and warp-interlaced fiber-reinforced composite topologies while avoiding unphysical tow intersections is presented. This is achieved by extending an existing RVE generation strategy in two significant ways: (1) the local cross section shape of the tow is adjusted depending on the local tow curvature in a way that preserves the cross sectional area of the tow, and (2) the elementary crimp interval is separated into a planar and a transition region. The modifications facilitate the generation of a wide range of elaborate textile topologies without tow intersections, which are present without the proposed modifications unless complex tow to tow contact models are introduced. The mechanical properties of plain weaves were predicted based on the topology generated with the proposed algorithm as well as based on RVEs which were constructed based on actual micrographs, i.e. a “digital twin” of the actual microstructure. A comparison of the predicted mechanical properties based on finite element and Multiscale Generalized Method of Cells techniques shows close agreement. However, some differences exist with respect to experimentally determined material parameters due to the finite dimensions of the specimens. Lastly, mechanical properties of multilayered weaves are predicted with the finite element method. The considered material systems are carbon fiber in epoxy matrix as well as C/C-SiC. However, the procedure is applicable to a wide range of material systems.

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    High strength and high porosity YB2C2 ceramics prepared by a new high temperature reaction/ partial sintering process
    Heng Chen, Huimin Xiang, Fuzhi Dai, Jiachen Liu, Yanchun Zhou
    J. Mater. Sci. Technol., 2019, 35 (12): 2883-2891.  DOI: 10.1016/j.jmst.2018.09.071
    Abstract   HTML   PDF

    Porous ultrahigh temperature ceramics (UHTCs) are potential candidates as reusable thermal protection materials of transpiration cooling system in scramjet engine. However, low strength and low porosity are the main limitations of porous UHTCs. To overcome these problems, herein, a new and simple in-situ reaction/partial sintering process has been developed for preparing high strength and high porosity porous YB2C2. In this process, a simple gas-releasing in-situ reaction has been designed, and the formation and escape of gases can block the shrinkage during sintering process, which is favorable to increase the porosity of porous YB2C2. In order to demonstrate the advantages of the new method, porous YB2C2 ceramics have been fabricated from Y2O3, BN and graphite powders for the first time. The as-prepared porous YB2C2 ceramics possess high porosity of 57.17%-75.26% and high compressive strength of 9.32-34.78?MPa. The porosity, sintered density, radical shrinkage and compressive strength of porous YB2C2 ceramics can be controlled simply by changing the green density. Due to utilization of graphite as the carbon source, the porous YB2C2 ceramics show anisotropy in microstructure and mechanical behavior. These features render the porous YB2C2 ceramics promising as a thermal-insulating light-weight component for transpiration cooling system.

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    Effect of heat treatment temperature on microstructure and electromagnetic shielding properties of graphene/SiBCN composites
    , Yongsheng Liu, Mingxi Zhao, Fang Ye, Laifei Cheng
    J. Mater. Sci. Technol., 2019, 35 (12): 2897-2905.  DOI: 10.1016/j.jmst.2019.07.018
    Abstract   HTML   PDF

    Three-dimensional (3D) graphene/SiBCN composites (GF/SiBCN) were prepared by depositing SiBCN ceramics in 3D graphene foam via the chemical vapor infiltration technique. The effect of the heat treatment temperature on the microstructure, phase composition, and electromagnetic properties of the GF/SiBCN composite was investigated. The SiBCN ceramics maintained an amorphous structure in the composite below 1400?°C above which the crystallinity of the free carbon phase gradually increased. While the Si3N4 and B4C phases started to crystallize at 1500?°C and their crystallinity increased with temperature, SiC was observed at 1700?°C. The electromagnetic shielding effectiveness of GF/SiBCN increased with the heat treatment temperature.

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