The Experts below are selected from a list of 1605 Experts worldwide ranked by ideXlab platform
Litong Zhang - One of the best experts on this subject based on the ideXlab platform.
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mechanical and dielectric properties of porous and wave transparent si3n4 si3n4 composite ceramics fabricated by 3d printing combined with Chemical Vapor Infiltration
Journal of Advanced Ceramics, 2019Co-Authors: Zanlin Cheng, Laifei Cheng, Yongsheng Liu, Hailong Qin, Tianlu Qiao, Litong ZhangAbstract:Porous Si3N4-Si3N4 composite ceramics were fabricated by 3D printing combined with low-pressure Chemical Vapor Infiltration (CVI). This technique could effectively improve the designability of porous Si3N4 ceramics and optimize the mechanical and dielectric properties. The effects of process parameters including the deposition time and heat treatment on the microstructure and properties of porous Si3N4-Si3N4 composite ceramics were studied. The study highlights following: When CVI processing time was increased from 0 to 12 h, the porosity decreased from 68.65% to 26.07% and the density increased from 0.99 to 2.02 g/cm3. At the same time, the dielectric constant gradually increased from 1.72 to 3.60; however, the dielectric loss always remained less than 0.01, indicating the excellent electromagnetic (EM) wave-transparent performance of porous Si3N4-Si3N4 composite ceramics. The maximum flexural strength of 47±2 MPa was achieved when the deposition time attained 6 h. After heat treatment, the porosity increased from 26.07% to 36.02% and the dielectric constant got a slight increase from 3.60 to 3.70 with the dielectric loss still maintaining lower than 0.01. It has been demonstrated that the porous Si3N4-Si3N4 composite ceramics are a promising structural and EM wave-transparent material suitable for high temperature service.
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dielectric and microwave absorption properties of sicnw sibcn composite ceramics deposited via Chemical Vapor Infiltration
Journal of Alloys and Compounds, 2019Co-Authors: Hailong Qin, Laifei Cheng, Yongsheng Liu, Zanlin Cheng, Chao Chen, Litong ZhangAbstract:Abstract Silicon-boron carbonitride ceramics (SiBCN) containing various contents of silicon carbide nanowires (SiCnw) were fabricated via Chemical Vapor Infiltration. The effects of SiCnw content on the morphology, microstructure, phase composition, dielectric and electromagnetic wave (EMW) absorption of the composite ceramics were investigated. Randomly oriented SiCnw contributes to the formation of a conductive network; this leads to an increase in the electrical conductivity. With the increase of the SiCnw content, the dielectric constant and the dielectric loss linearly increased from 3.7 to 0.05 to 4.2 and 0.39, respectively. For the maximum SiCnw mass fraction of 3.8 wt%, the reflection coefficient of composite ceramics attained its minimum value of −15 dB in the X band and the effective absorption bandwidth was 2.88 GHz. After the oxidation, the composite ceramics still had a relatively high dielectric loss. The SiCnw-SiBCN composite ceramics exhibited excellent EMW absorption, indicating their great potential as high-temperature microwave absorption materials.
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improvement of the strength and toughness of carbon fiber sic composites via Chemical Vapor Infiltration grown sic nanowire interphases
Ceramics International, 2018Co-Authors: Yongsheng Liu, Laifei Cheng, Chengyu Zhang, Zhuo Tian, Litong ZhangAbstract:Abstract SiC nanowires (SiCnws) were used to modify the interphase of carbon fiber/pyrocarbon/SiC(Cf/PyC/SiC) composites. These SiCnws were grown in the carbon fiber preform via Chemical Vapor Infiltration(CVI). The effects of these SiCnw interphases on the microstructure and mechanical properties of Cf/PyC/SiC composites were investigated. According to the obtained results, the composites containing SiCnw interphases(i.e., Cf/SiCnw/PyC/SiC and Cf/SiCnw/SiC) showed higher strength and toughness than Cf/PyC/SiC composites at both room and high temperatures. The superior pull-out and bridging crack characteristics of SiCnws can account for the toughening of Cf/SiC and Cf/PyC/SiC upon growth of SiCnw interphases, which resulted in composites with higher crack propagation resistances and superior load with standing capabilities.
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modelling shear behaviors of 2d c sic z pinned joint prepared by Chemical Vapor Infiltration
Ceramics International, 2018Co-Authors: Yi Zhang, Laifei Cheng, Litong Zhang, Chao Chen, Yongsheng LiuAbstract:Abstract Progressive failure model is developed to investigate shear behaviors of 2D C/SiC z-pinned joint prepared by Chemical Vapor Infiltration (CVI). It includes progressive failure model of 2D C/SiC composites and cohesive model of faying plane, in order to describe joint nonlinear shear behaviors and z-pin shear-off failure mode, respectively. All cohesive parameters are directly obtained from mechanical properties of 2D C/SiC composites. Results show that the model can almost reproduce joint shear behaviors and z-pin shear-off failure process. Joint failure results from coupled fiber tensile and fiber–matrix shearing damages at faying plane. The model also successfully demonstrates that joint shear properties can be effectively improved by changing z-pin density and diameter. The relationship between joint properties and mechanical properties of 2D C/SiC composites are subsequently obtained with the model. In this sense, joint shear strength increases with cohesive or in-plane shear strengths of 2D C/SiC composites.
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enhanced densification and mechanical properties of carbon fiber reinforced silicon carbide matrix composites via laser machining aided Chemical Vapor Infiltration
Ceramics International, 2017Co-Authors: Jing Wang, Laifei Cheng, Litong Zhang, Yi Zhang, Qing ZhangAbstract:Abstract In this study, laser machining aided Chemical Vapor Infiltration (LA-CVI) was developed to improve the density and mechanical properties of carbon fiber reinforced silicon carbide matrix (C/SiC) composites. Results showed that the density of C/SiC composites increased to 2.25 g cm−3 due to the generation of additional Infiltration channels. Compressive strength and shear strength were improved by 50.7% and 11.8%, respectively, compared to those of classical CVI-C/SiC composites. Moreover, tensile strength showed similar value as that of classical CVI-C/SiC composites. These effects were attributed to re-opened Infiltration channels which could provide more paths for precursor gases, thus promoting the densification in central region of composites. Furthermore, channels themselves were filled with SiC matrix and formed a dense SiC coating, which reflected convolution effects under uniaxial compression and exhibited damage-tolerant behavior under shear load.
Laifei Cheng - One of the best experts on this subject based on the ideXlab platform.
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fabrication of sic whisker reinforced sic ceramic matrix composites based on 3d printing and Chemical Vapor Infiltration technology
Journal of The European Ceramic Society, 2019Co-Authors: Laifei Cheng, Shangwu Fan, Yongsheng LiuAbstract:Abstract Spray drying, binder jetting and Chemical Vapor Infiltration (CVI) were used in combination for the first time to fabricate SiC whisker-reinforced SiC ceramic matrix composites (SiCW/SiC). Granulated needle-shaped SiCW was spray dried into SiCW spherical particles to increase flowability and thereby increase printability. Then, binder jetting was employed to print a novel SiCW preform with two-stage pores using the SiCW spherical particles. The subsequent CVI technology produced pure, dense, and continuous SiC matrix with high modulus and strength. Consequently, SiCW/SiC with appropriate mechanical properties was obtained. Finally, the challenges of the novel method and the ways to improve the mechanical properties of SiCW/SiC are discussed.
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mechanical and dielectric properties of porous and wave transparent si3n4 si3n4 composite ceramics fabricated by 3d printing combined with Chemical Vapor Infiltration
Journal of Advanced Ceramics, 2019Co-Authors: Zanlin Cheng, Laifei Cheng, Yongsheng Liu, Hailong Qin, Tianlu Qiao, Litong ZhangAbstract:Porous Si3N4-Si3N4 composite ceramics were fabricated by 3D printing combined with low-pressure Chemical Vapor Infiltration (CVI). This technique could effectively improve the designability of porous Si3N4 ceramics and optimize the mechanical and dielectric properties. The effects of process parameters including the deposition time and heat treatment on the microstructure and properties of porous Si3N4-Si3N4 composite ceramics were studied. The study highlights following: When CVI processing time was increased from 0 to 12 h, the porosity decreased from 68.65% to 26.07% and the density increased from 0.99 to 2.02 g/cm3. At the same time, the dielectric constant gradually increased from 1.72 to 3.60; however, the dielectric loss always remained less than 0.01, indicating the excellent electromagnetic (EM) wave-transparent performance of porous Si3N4-Si3N4 composite ceramics. The maximum flexural strength of 47±2 MPa was achieved when the deposition time attained 6 h. After heat treatment, the porosity increased from 26.07% to 36.02% and the dielectric constant got a slight increase from 3.60 to 3.70 with the dielectric loss still maintaining lower than 0.01. It has been demonstrated that the porous Si3N4-Si3N4 composite ceramics are a promising structural and EM wave-transparent material suitable for high temperature service.
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dielectric and microwave absorption properties of sicnw sibcn composite ceramics deposited via Chemical Vapor Infiltration
Journal of Alloys and Compounds, 2019Co-Authors: Hailong Qin, Laifei Cheng, Yongsheng Liu, Zanlin Cheng, Chao Chen, Litong ZhangAbstract:Abstract Silicon-boron carbonitride ceramics (SiBCN) containing various contents of silicon carbide nanowires (SiCnw) were fabricated via Chemical Vapor Infiltration. The effects of SiCnw content on the morphology, microstructure, phase composition, dielectric and electromagnetic wave (EMW) absorption of the composite ceramics were investigated. Randomly oriented SiCnw contributes to the formation of a conductive network; this leads to an increase in the electrical conductivity. With the increase of the SiCnw content, the dielectric constant and the dielectric loss linearly increased from 3.7 to 0.05 to 4.2 and 0.39, respectively. For the maximum SiCnw mass fraction of 3.8 wt%, the reflection coefficient of composite ceramics attained its minimum value of −15 dB in the X band and the effective absorption bandwidth was 2.88 GHz. After the oxidation, the composite ceramics still had a relatively high dielectric loss. The SiCnw-SiBCN composite ceramics exhibited excellent EMW absorption, indicating their great potential as high-temperature microwave absorption materials.
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improvement of the strength and toughness of carbon fiber sic composites via Chemical Vapor Infiltration grown sic nanowire interphases
Ceramics International, 2018Co-Authors: Yongsheng Liu, Laifei Cheng, Chengyu Zhang, Zhuo Tian, Litong ZhangAbstract:Abstract SiC nanowires (SiCnws) were used to modify the interphase of carbon fiber/pyrocarbon/SiC(Cf/PyC/SiC) composites. These SiCnws were grown in the carbon fiber preform via Chemical Vapor Infiltration(CVI). The effects of these SiCnw interphases on the microstructure and mechanical properties of Cf/PyC/SiC composites were investigated. According to the obtained results, the composites containing SiCnw interphases(i.e., Cf/SiCnw/PyC/SiC and Cf/SiCnw/SiC) showed higher strength and toughness than Cf/PyC/SiC composites at both room and high temperatures. The superior pull-out and bridging crack characteristics of SiCnws can account for the toughening of Cf/SiC and Cf/PyC/SiC upon growth of SiCnw interphases, which resulted in composites with higher crack propagation resistances and superior load with standing capabilities.
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modelling shear behaviors of 2d c sic z pinned joint prepared by Chemical Vapor Infiltration
Ceramics International, 2018Co-Authors: Yi Zhang, Laifei Cheng, Litong Zhang, Chao Chen, Yongsheng LiuAbstract:Abstract Progressive failure model is developed to investigate shear behaviors of 2D C/SiC z-pinned joint prepared by Chemical Vapor Infiltration (CVI). It includes progressive failure model of 2D C/SiC composites and cohesive model of faying plane, in order to describe joint nonlinear shear behaviors and z-pin shear-off failure mode, respectively. All cohesive parameters are directly obtained from mechanical properties of 2D C/SiC composites. Results show that the model can almost reproduce joint shear behaviors and z-pin shear-off failure process. Joint failure results from coupled fiber tensile and fiber–matrix shearing damages at faying plane. The model also successfully demonstrates that joint shear properties can be effectively improved by changing z-pin density and diameter. The relationship between joint properties and mechanical properties of 2D C/SiC composites are subsequently obtained with the model. In this sense, joint shear strength increases with cohesive or in-plane shear strengths of 2D C/SiC composites.
Yongsheng Liu - One of the best experts on this subject based on the ideXlab platform.
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fabrication of sic whisker reinforced sic ceramic matrix composites based on 3d printing and Chemical Vapor Infiltration technology
Journal of The European Ceramic Society, 2019Co-Authors: Laifei Cheng, Shangwu Fan, Yongsheng LiuAbstract:Abstract Spray drying, binder jetting and Chemical Vapor Infiltration (CVI) were used in combination for the first time to fabricate SiC whisker-reinforced SiC ceramic matrix composites (SiCW/SiC). Granulated needle-shaped SiCW was spray dried into SiCW spherical particles to increase flowability and thereby increase printability. Then, binder jetting was employed to print a novel SiCW preform with two-stage pores using the SiCW spherical particles. The subsequent CVI technology produced pure, dense, and continuous SiC matrix with high modulus and strength. Consequently, SiCW/SiC with appropriate mechanical properties was obtained. Finally, the challenges of the novel method and the ways to improve the mechanical properties of SiCW/SiC are discussed.
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mechanical and dielectric properties of porous and wave transparent si3n4 si3n4 composite ceramics fabricated by 3d printing combined with Chemical Vapor Infiltration
Journal of Advanced Ceramics, 2019Co-Authors: Zanlin Cheng, Laifei Cheng, Yongsheng Liu, Hailong Qin, Tianlu Qiao, Litong ZhangAbstract:Porous Si3N4-Si3N4 composite ceramics were fabricated by 3D printing combined with low-pressure Chemical Vapor Infiltration (CVI). This technique could effectively improve the designability of porous Si3N4 ceramics and optimize the mechanical and dielectric properties. The effects of process parameters including the deposition time and heat treatment on the microstructure and properties of porous Si3N4-Si3N4 composite ceramics were studied. The study highlights following: When CVI processing time was increased from 0 to 12 h, the porosity decreased from 68.65% to 26.07% and the density increased from 0.99 to 2.02 g/cm3. At the same time, the dielectric constant gradually increased from 1.72 to 3.60; however, the dielectric loss always remained less than 0.01, indicating the excellent electromagnetic (EM) wave-transparent performance of porous Si3N4-Si3N4 composite ceramics. The maximum flexural strength of 47±2 MPa was achieved when the deposition time attained 6 h. After heat treatment, the porosity increased from 26.07% to 36.02% and the dielectric constant got a slight increase from 3.60 to 3.70 with the dielectric loss still maintaining lower than 0.01. It has been demonstrated that the porous Si3N4-Si3N4 composite ceramics are a promising structural and EM wave-transparent material suitable for high temperature service.
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dielectric and microwave absorption properties of sicnw sibcn composite ceramics deposited via Chemical Vapor Infiltration
Journal of Alloys and Compounds, 2019Co-Authors: Hailong Qin, Laifei Cheng, Yongsheng Liu, Zanlin Cheng, Chao Chen, Litong ZhangAbstract:Abstract Silicon-boron carbonitride ceramics (SiBCN) containing various contents of silicon carbide nanowires (SiCnw) were fabricated via Chemical Vapor Infiltration. The effects of SiCnw content on the morphology, microstructure, phase composition, dielectric and electromagnetic wave (EMW) absorption of the composite ceramics were investigated. Randomly oriented SiCnw contributes to the formation of a conductive network; this leads to an increase in the electrical conductivity. With the increase of the SiCnw content, the dielectric constant and the dielectric loss linearly increased from 3.7 to 0.05 to 4.2 and 0.39, respectively. For the maximum SiCnw mass fraction of 3.8 wt%, the reflection coefficient of composite ceramics attained its minimum value of −15 dB in the X band and the effective absorption bandwidth was 2.88 GHz. After the oxidation, the composite ceramics still had a relatively high dielectric loss. The SiCnw-SiBCN composite ceramics exhibited excellent EMW absorption, indicating their great potential as high-temperature microwave absorption materials.
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improvement of the strength and toughness of carbon fiber sic composites via Chemical Vapor Infiltration grown sic nanowire interphases
Ceramics International, 2018Co-Authors: Yongsheng Liu, Laifei Cheng, Chengyu Zhang, Zhuo Tian, Litong ZhangAbstract:Abstract SiC nanowires (SiCnws) were used to modify the interphase of carbon fiber/pyrocarbon/SiC(Cf/PyC/SiC) composites. These SiCnws were grown in the carbon fiber preform via Chemical Vapor Infiltration(CVI). The effects of these SiCnw interphases on the microstructure and mechanical properties of Cf/PyC/SiC composites were investigated. According to the obtained results, the composites containing SiCnw interphases(i.e., Cf/SiCnw/PyC/SiC and Cf/SiCnw/SiC) showed higher strength and toughness than Cf/PyC/SiC composites at both room and high temperatures. The superior pull-out and bridging crack characteristics of SiCnws can account for the toughening of Cf/SiC and Cf/PyC/SiC upon growth of SiCnw interphases, which resulted in composites with higher crack propagation resistances and superior load with standing capabilities.
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modelling shear behaviors of 2d c sic z pinned joint prepared by Chemical Vapor Infiltration
Ceramics International, 2018Co-Authors: Yi Zhang, Laifei Cheng, Litong Zhang, Chao Chen, Yongsheng LiuAbstract:Abstract Progressive failure model is developed to investigate shear behaviors of 2D C/SiC z-pinned joint prepared by Chemical Vapor Infiltration (CVI). It includes progressive failure model of 2D C/SiC composites and cohesive model of faying plane, in order to describe joint nonlinear shear behaviors and z-pin shear-off failure mode, respectively. All cohesive parameters are directly obtained from mechanical properties of 2D C/SiC composites. Results show that the model can almost reproduce joint shear behaviors and z-pin shear-off failure process. Joint failure results from coupled fiber tensile and fiber–matrix shearing damages at faying plane. The model also successfully demonstrates that joint shear properties can be effectively improved by changing z-pin density and diameter. The relationship between joint properties and mechanical properties of 2D C/SiC composites are subsequently obtained with the model. In this sense, joint shear strength increases with cohesive or in-plane shear strengths of 2D C/SiC composites.
Jing Wang - One of the best experts on this subject based on the ideXlab platform.
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enhanced densification and mechanical properties of carbon fiber reinforced silicon carbide matrix composites via laser machining aided Chemical Vapor Infiltration
Ceramics International, 2017Co-Authors: Jing Wang, Laifei Cheng, Litong Zhang, Yi Zhang, Qing ZhangAbstract:Abstract In this study, laser machining aided Chemical Vapor Infiltration (LA-CVI) was developed to improve the density and mechanical properties of carbon fiber reinforced silicon carbide matrix (C/SiC) composites. Results showed that the density of C/SiC composites increased to 2.25 g cm−3 due to the generation of additional Infiltration channels. Compressive strength and shear strength were improved by 50.7% and 11.8%, respectively, compared to those of classical CVI-C/SiC composites. Moreover, tensile strength showed similar value as that of classical CVI-C/SiC composites. These effects were attributed to re-opened Infiltration channels which could provide more paths for precursor gases, thus promoting the densification in central region of composites. Furthermore, channels themselves were filled with SiC matrix and formed a dense SiC coating, which reflected convolution effects under uniaxial compression and exhibited damage-tolerant behavior under shear load.
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silicon carbide whisker reinforced silicon carbide composites by Chemical Vapor Infiltration
Materials Science and Engineering A-structural Materials Properties Microstructure and Processing, 2006Co-Authors: Yunfeng Hua, Laifei Cheng, Litong Zhang, Jing WangAbstract:Abstract Silicon carbide (SiC) whisker reinforced SiC ceramic matrix composites were prepared by Chemical Vapor Infiltration. Microstructure and mechanical properties of the composites were investigated. The fracture toughness of the composites was improved to 5.65–7.21 MPa m 1/2 , and its flexural strength value was between 196 MPa and 305 MPa, depending on the relative density. The pullout of rough whisker, crack deflection and whisker bridging are responsible for the improvement in fracture toughness. The randomly oriented whiskers that paralleled to the crack plane, and the weak bonding strength between whisker and matrix could not have much stress transfer from the matrix, leading to the low flexural strength.
Sufang Tang - One of the best experts on this subject based on the ideXlab platform.
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sandwich structured c c sic composites fabricated by electromagnetic coupling Chemical Vapor Infiltration
Scientific Reports, 2017Co-Authors: Wenhu Hong, Sufang Tang, Huiming ChengAbstract:Carbon fiber (CF) reinforced carbon-silicon carbide (C/C-SiC) composites are one of the most promising lightweight materials for re-entry thermal protection, rocket nozzles and brake discs applications. In this paper, a novel sandwich-structured C/C-SiC composite, containing two exterior C/SiC layers, two gradient C/C-SiC layers and a C/C core, has been designed and fabricated by two-step electromagnetic-coupling Chemical Vapor Infiltration (E-CVI) for a 20-hour deposition time. The cross-section morphologies, interface microstructures and SiC-matrix growth characteristics and compositions of the composites were characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM) and X-ray diffraction (XRD), respectively. Microstructure characterization indicates that the SiC growth includes an initial amorphous SiC zone, a gradual crystallization of SiC and grow-up of nano-crystal, and a columnar grain region. The sandwich structure, rapid deposition rate and growth characteristics are attributed to the formation of thermal gradient and the establishment of electromagnetic field in the E-CVI process. The composite possesses low density of 1.84 g/cm3, high flexural strength of 325 MPa, and low linear ablation rate of 0.38 μm/s under exposure to 5-cycle oxyacetylene flame for 1000 s at ~1700 °C.
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fabrication and characterization of c sic composites with large thickness high density and near stoichiometric matrix by heaterless Chemical Vapor Infiltration
Materials Science and Engineering A-structural Materials Properties Microstructure and Processing, 2007Co-Authors: Sufang Tang, Jingyi Deng, Shijun WangAbstract:Abstract The C/SiC composites with a 7–8 mm thickness, a 2.3–2.4 g/cm 3 density, and a Si/C ratio 1.08–1.09 matrix have been fabricated by heaterless Chemical Vapor Infiltration (CVI) in a 25-h deposition time. The C/SiC composites exhibited a damage-tolerant fracture behavior, and its average flexural strength, longitudinal/transverse compressive strength and fracture toughness were 163 MPa, 304/276 MPa and 6.5 MPa m 1/2 , respectively. The composites presented a thermal expansion of (1.09–1.93) × 10 −6 °C −1 and a thermal conductivity (TC) of 8.34–6.56 W/m °C in the range 200–1000 °C.
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fabrication and microstructure of c sic composites using a novel heaterless Chemical Vapor Infiltration technique
Journal of the American Ceramic Society, 2005Co-Authors: Sufang Tang, Jingyi Deng, Wenchuan Liu, Ke YangAbstract:Fabrication of C/SiC composites by using the heaterless Chemical Vapor Infiltration (HCVI) technique, which is an improved technology based on the conventional Chemical Vapor Infiltration, is reported for the first time in this paper. In the HCVI process, a gradient temperature field formed in the fiber preform overcomes the problems of slow diffusion and restricted permeability of gaseous reactant species to some extent, and the electro-deposition is necessary to accelerate the SiC deposition rates. The highest linear deposition rates of SiC matrix within inter-fiber pores are 0.33 mu m/h. Microstructures of the C/SiC composites are uniform, and the inter-fiber and inter-ply pores can be well infiltrated. The longitudinal and circumferential microcracks are found in the composites.