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1.
界面改性涂层对调节复合材料的力学性能起到重要作用。特别是在气相渗硅(GSI)制备C_f/SiC复合材料时,合适的界面改性涂层一方面保护C纤维不受Si反应侵蚀,另一方面调节C纤维和SiC基体的界面结合状况。通过在3D-C纤维预制件中制备先驱体浸渍-裂解(PIP)SiC涂层来进行界面改性,研究了PIP-SiC涂层对GSI C_f/SiC复合材料力学性能的影响。结果表明:无涂层改性的GSI C_f/SiC复合材料力学性能较差,呈现脆性断裂特征,其弯曲强度、弯曲模量和断裂韧性分别为87.6 MPa、56.9GPa和2.1 MPa·m~(1/2)。具有PIP-SiC界面改性涂层的C_f/SiC复合材料力学性能得到改善,PIP-SiC涂层改性后,GSI C_f/SiC复合材料的弯曲强度、弯曲模量和断裂韧性随着PIP-SiC周期数的增加而降低,PIP-SiC为1个周期制备的GSI C_f/SiC复合材料的力学性能最高,其弯曲强度、弯曲模量、断裂韧性分别为185.2 MPa、91.1GPa和5.5 MPa·m~(1/2)。PIP-SiC界面改性涂层的作用机制主要体现在载荷传递和"阻挡"Si的侵蚀2个方面。  相似文献   

2.
Si3N4-BN-SiC复合材料以其良好的力学性能和抗氧化性能而具有良好的工程应用前景。本研究以Si、Si3N4稀释剂、B4C和Y2O3为原料, 采用燃烧合成法成功制备了Si3N4-BN-SiC复合材料。通过Si、B4C和N2气之间的反应, 在Si3N4陶瓷中原位引入BN和SiC, 制备的Si3N4-BN-SiC复合材料由长棒状的β-Si3N4和空心球形复合材料组成。实验研究了空心球微结构的形成机理, 结果表明, 生成的SiC、BN颗粒及玻璃相覆盖在原料颗粒上, 当原料颗粒反应完全时, 形成空心球形微结构。并进一步研究了B4C含量对Si3N4-BN-SiC复合材料力学性能的影响。原位引入SiC和BN在一定程度上可以提高复合材料的力学性能。当B4C添加量为质量分数0~20%时, 获得了抗弯强度为28~144 MPa、断裂韧性为0.6~2.3 MPa·m 1/2, 杨氏模量为17.4~54.5 GPa, 孔隙率为37.7%~51.8%的Si3N4-BN-SiC复合材料。  相似文献   

3.
Oxidation behaviors of three-dimensional woven C/PyC/SiC and SiC/PyC/SiC prepared by CVI processing were investigated in an O2-Ar atmosphere at 600 °C, 900 °C and 1200 °C, respectively, by using thermogravimetric analysis. After machining, both composites should be protected by CVD SiC coating, which was demonstrated effectively in improving the oxidation resistance of both composites. The oxidation behavior of SiC/PyC/SiC was different from that of C/PyC/SiC. The oxidation kinetics of C/PyC/SiC was controlled by the rate of the reaction between carbon and oxygen at 600 °C and by the oxygen diffusion through the coating microcracks at 900 °C. The oxidation kinetics of SiC/PyC/SiC at both 600 °C and 900 °C were assumed to be controlled by the oxygen diffusion through channels of coating and matrix defects and looped pipelines instead of PyC interphase. At 1200 °C, the oxidation was controlled by oxygen diffusion through the SiO2 scale, which took place mainly on the surfaces of both composites.  相似文献   

4.
In this paper, a numerical model which incorporates the oxidation damage model and the finite element model of 2D plain woven composites is presented for simulation of the oxidation behaviors of 2D plain woven C/SiC composite under preloading oxidation atmosphere. The equal proportional reduction method is firstly proposed to calculate the residual moduli and strength of unidirectional C/SiC composite. The multi-scale method is developed to simulate the residual elastic moduli and strength of 2D plain woven C/SiC composite. The multi-scale method is able to accurately predict the residual elastic modulus and strength of the composite. Besides, the simulated residual elastic moduli and strength of 2D plain woven C/SiC composites under preloading oxidation atmosphere show good agreements with experimental results. Furthermore, the preload, oxidation time, temperature and fiber volume fractions of the composite are investigated to show their influences upon the residual elastic modulus and strength of 2D plain woven C/SiC composites.  相似文献   

5.
Understanding the in‐plane shear behaviour of composites is essential to establish the design basis for practical applications. This study aims to investigate the shear damage behaviours of 2D needled C/SiC composites by various characterization techniques. The effect of layer arrangement on shear modulus and strength was discussed via shear stress‐strain responses. The shear strain field evolution and uniformity variation were studied by digital image correlation. It shows that the uniformity of shear strain field changes with the shear load, and the shear strain field evolution consist of 5 stages. The electrical resistivity measurement results indicate that structural deformation and damage evolution caused the electrical resistivity change. Furthermore, the damage evolution has a double effect on the electrical resistivity variation. The acoustic emission monitoring shows that the shear damage evolution is a 3‐stage nonlinear process before failure. The shear damages were categorized via acoustic characteristics. Besides, the postfailure behaviours were also discussed in this study.  相似文献   

6.
Mo-Si-B系原位复合材料的研究   总被引:1,自引:0,他引:1  
Mo-Si-B系原位复合材料是一族新型的高温结构材料,目前的研究主要集中在其中的α-Mo Mo3Si Mo 5SiB2(T2)、Mo 5Si3Bx(T1) Mo3Si Mo5SiB2(T2)和Mo5Si3Bx(T1) MoSi2 MoB 3个体系.详细介绍了Mo-Si-B系原位复合材料的研究进展及应用前景,并在此基础上提出了进一步研究的重点和方向.  相似文献   

7.
Layered compounds play pivotal roles as precursors for producing 2D materials through mechanical exfoliation(micro-mechanical cleavage) or chemical approaches. Therefore, searching for layered compounds with sharp anisotropic chemical bonding and properties becomes emergent. In this work, the stability, electronic structure, elastic properties, and lattice dynamics of YB_2C_2 were investigated. Strong anisotropy in elastic properties is revealed, i.e., high Young's modulus in a-b plane but low Young's modulus in c direction. The maximum to minimum Young's modulus ratio is 2.41 and 2.45 for YB_2C_2 with P42/mmc and P4/mbm symmetry, respectively. The most likely systems for shear sliding or microdelaminating are(001)[100] and(001)[010]. The anisotropic elastic properties are underpinned by the anisotropic chemical bonding, i.e., strong bonding within the B_2C_2 nets and weak bonding between Y atom layers and B_2C_2 nets. YB_2C_2 is electrically conductive and the contributions to the electrical conductivity are from delocalized Y 4de_g as well as B _2p_z and _ pzelectrons. The layered crystal structure, sharp anisotropic mechanical properties, and metallic conductivity endorse YB_2C_2 promising as a precursor for new 2D B_2C_2 nets.  相似文献   

8.
To further improve the oxidation resistance of coating for carbon/carbon (C/C) composites, a multi-layer CVD-SiC/MoSi2–CrSi2–Si/B-modified SiC coating was prepared on the surface of C/C composites by pack cementation and chemical vapour deposition method, respectively. The microstructures, oxidation and thermal shock resistance of the coating were studied. The influence of B content in pack powder on the microstructure and oxidation resistance of B-modified SiC coating was also investigated. The results show that the B-modified SiC coating prepared with 10 wt.% B exhibited the best oxidation protection ability for C/C composites at 1173 K. The multi-layer coatings could protect the C/C composites at 1173 K for 30 h and 1873 K for 200 h, and endure 30 thermal cycles between 1873 K and room temperatures. The oxidation resistance and thermal shock resistance is mainly attributed to their dense structure and self-sealing property.  相似文献   

9.
采用先驱体浸渍裂解工艺制备无界面、SiC、PyC和PyC/SiC等界面相SiC/SiC复合材料, 研究了SiC/SiC复合材料的微观结构及静态力学性能, 并通过强迫振动法系统分析了界面相对复合材料内耗行为的影响。研究结果表明, 引入界面相有效改善了复合材料的微观结构及力学性能, 并降低了复合材料的内耗。其中, PyC/SiC复相界面中亚层SiC限制了PyC界面相与纤维的结合及塑性形变, 提高了复合材料的力学性能; 同时, 界面相对SiC/SiC复合材料内耗行为有显著影响, 材料内耗水平与界面剪切强度成反比。对比50和350 ℃时的材料内耗变化率发现, 随界面剪切强度增大, 材料内耗呈降低的趋势, 且含有PyC的PyC/SiC界面复合材料具有较低的内耗变化率, 说明PyC/SiC复相界面的SiC/SiC复合材料更适于高温振动环境。  相似文献   

10.
碳纤维增强C—SiC梯度基复合材料研究   总被引:3,自引:0,他引:3  
采用CVI工艺均热法共沉积技术制备了碳纤维增强C-SiC梯度基复合材料。C和SiC的原料氛分别是C2H2t CH3SiCl3,Ar和H2分别是载流和稀释气体。基体微观结构的变化通过控制原料气体的成分配比藜得。测试了材料的力学性能、抗氧化性能和摩擦磨损性能。利用金相技术、电子探针成分分析技术、TEM和SEM技术观察和分析了材料的微观结构。试验结果表明,这种材料的组织结构特点是:在微观上是梯度的,即围  相似文献   

11.
Matrix compositions based on Si2N2O, with Al2O3 and CaO additions, were used to hot press Nicalon SiC fibre-reinforced composites at 1600 °C. With both CaO and Al2O3 additions, eutectic melting formed an appreciable volume of liquid phase during hot pressing, which remained as a stable glassy phase in the cooled composites. This liquid phase fostered formation of 240 nm thick carbon-rich interphases between the fibres and the matrix. These interphases showed relatively low interfacial shear strength and resulted in composites which showed non-catastrophic, notch-independent fracture. Matrices using either Al2O3 or CaO did not form adequate liquid phase to form coarse interphases, and fracture was catastrophic in nature. Post-heat treatment of the composites at 1000 °C showed peripheral oxidation (removal of the carbon content of the interphase) indicating limited protection afforded when glassy phase was present in the matrix. Controlled cooling in the hot press did not cause the liquid regions to devitrify.  相似文献   

12.
TiN/Si3N4纳米多层膜的生长结构与超硬效应   总被引:3,自引:1,他引:3  
采用磁控溅射方法制备了一系列不同Si3N4和TiN层厚的TiN/Si3N4纳米多层膜,采用X射线衍射、高分辨电子显微分析和微力学探针表征了薄膜的微结构和力学性能,研究了Si3N4和TiN层厚对多层膜生长结构和力学性能的影响.结果表明:当Si3N4层厚小于0.7 nm时,原为非晶的Si3N4在TiN的模板作用下晶化并与之形成共格外延生长的柱状晶,使TiN/Si3N4多层膜产生硬度和弹性模量异常升高的超硬效应.最高硬度和弹性模量分别为34.0 GPa和353.5 GPa.当其厚度大于1.3 nm时,Si3N4呈现非晶态,阻断了TiN的外延生长,多层膜的力学性能明显降低.此外,TiN层厚的增加也会对TiN/Si3N4多层膜的生长结构和力学性能造成影响,随着TiN层厚的增加,多层膜的硬度和弹性模量缓慢下降.  相似文献   

13.
《Materials Letters》2003,57(22-23):3387-3391
The C40 Mo(Si0.75Al0.25)2 and Mo(Si0.75Al0.25)2/SiC materials containing micro-, nano-scale structure and Mo/Mo5Si3 phases have been prepared by spark plasma sintering (SPS) of mechanically alloyed (MA) powders. Sintered composites have hardness around 14 GPa. The 1.84 MPa m1/2 toughness of C40 Mo(Si,Al)2 can be 30% improved by addition of 20 vol.% SiC.  相似文献   

14.
结合复合材料氧化质量损失率模型和混合率公式, 发展了单向C/SiC复合材料在无应力氧化下的弹性模量预测方法。对400~700 ℃和700~900 ℃两种氧化机制下C/SiC复合材料的弹性模量进行了预测, 分析了氧化温度、氧化时间和纤维体积含量对C/SiC复合材料弹性模量的影响。开展了单向C/SiC复合材料在650 ℃和800 ℃空气环境下的无应力氧化试验, 建立了复合材料质量损失率与氧化时间的变化关系, 得到了氧化后材料拉伸应力-应变曲线。同时, 将理论预测值与试验结果进行对比, 发现理论值与试验值基本吻合, 从而验证了该方法能够有效地预测无应力氧化下陶瓷基复合材料的弹性性能。  相似文献   

15.
通过观察 C/ C2SiC复合材料组元分布的扫描电子显微镜(SEM)照片 , 获得了 C/ C2SiC复合材料化学气相渗透(CVI)制备过程中产生孔隙和微裂纹的几何信息。在此基础上 , 建立了包含孔隙和微裂纹的 C/ C2SiC微结构有限元模型 , 并利用均匀化等效计算方法预测了平纹编织 C/ C2 SiC复合材料的模量。针对 CVI沉积方式制备的 2组不同的 C/ C2SiC复合材料 , 实验测试与等效计算结果表明 : 基于 SEM照片建立的 C/ C2SiC纤维束和复合材料微结构有限元模型 , 能够反映 CVI工艺制备 C/ C2SiC中孔隙和微裂纹的分布状况; 计算结果与实验数据有良好的一致性 , 数值计算可有效预测 C/ C2SiC编织复合材料的模量。  相似文献   

16.
李锦涛  王波  杨扬  张程煜 《复合材料学报》2021,38(10):3432-3442
分析了化学气相渗透(CVI)工艺制备的陶瓷基复合材料的氧化损伤演化规律,基于基体的微裂纹分布规律及界面、纤维、基体等组分氧化历程,建立了考虑温度、氧化时间影响的纤维和单胞两个尺度的弹性模量预测模型。预测结果表明,碳纤维(Cf)/SiC和SiC纤维(SiCf)/SiC复合材料的拉伸弹性模量随氧化温度升高和氧化时间的增长,下降趋势越明显。通过复合材料高温氧化后的力学性能试验,验证了弹性性能预测模型的正确性:BN界面的SiCf/SiC材料在1000℃不同时间氧化后预测结果与试验结果误差不超过2%;PyC界面的Cf/SiC在700℃不同时间氧化后预测结果与试验结果误差不超过7%。   相似文献   

17.
A new kind of oxidation protection coating of Si-MoSi2 was developed for three dimensional carbon fiber reinforced silicon carbide composites which could be serviced upto 1550 °C. The overall oxidation behavior could be divided into three stages: (i) 500 °C < T < 800 °C, the oxidation mechanism was considered to be controlled by the chemical reaction between carbon and oxygen; (ii) 800 °C < T < 1100 °C, the oxidation of the composite was controlled by the diffusion of oxygen through the micro-cracks, and; (iii) T > 1100 °C, the oxidation of SiC became significant and was controlled by oxygen diffusion through the SiC layer. Microstructural analysis revealed that the oxidation protection coating had a three-layer structure: the out layer is oxidation layer of silica glass, the media layer is Si + MoSi2 layer, and the inside layer is SiC layer. The coated C/SiC composites exhibited excellent oxidation resistance and thermal shock resistance. After the composites annealed at 1550 °C for 50 h in air and 1550 °C 100 °C thermal shock for 50 times, the flexural strength was maintained by 85% and 80% respectively. The relationship between oxidation weight change and flexural strength revealed the criteria for protection coating was that the maximum point of oxidation weight gain was the failure starting point for oxidation protection coating.  相似文献   

18.
本文对ZrO2增韧10%SiC/Al2O3基复合材料和SiC颗粒弥散强化5%Al2O3/ZrO2基复合材料的冲蚀磨损的研究,实验表明:相交增初有助于断裂韧性的改善,从而缓和了材料的高角冲蚀率;高弹模量的SiC二相粒子引入后基体材料的硬度增加,提高了材料的抗低角磨损能力.显微结构(SEM)分析表明,不同的冲蚀角度条件下材料表面的损伤行为和磨损微观机制也不相同,通过PUD计算,定量表征材料的抗切向磨损能力.  相似文献   

19.
To reveal the shear properties of SiC matrix composites, interlaminar shear strength (ILSS) of three kinds of silicon carbide matrix composites was investigated by compression of the double notched shear specimen (DNS) at 900 °C in air. The investigated composites included a woven plain carbon fiber reinforced silicon carbide composite (2D-C/SiC), a two-and-a-half-dimensional carbon fiber-reinforced silicon carbide composite (2.5D-C/SiC) and a woven plain silicon carbon fiber reinforced silicon carbide composite (2D-SiC/SiC). A scanning electron microscope was employed to observe the microstructure and fracture morphologies. It can be found that the fiber type and reinforcement architecture have significant impacts on the ILSS of the SiC matrix composites. Great anisotropy of ILSS can be found for 2.5D-C/SiC because of the different fracture resistance of the warp fibers. Larger ILSS can be obtained when the specimens was loaded along the weft direction. In addition, the SiC fibers could enhance the ILSS, compared with carbon fibers. The improvement is attributed to the higher oxidation resistance of SiC fibers and the similar thermal expansion coefficients between the matrix and the fibers.  相似文献   

20.
利用三维编织炭纤维预制件通过先驱体浸渍裂解法制备C/SiC复合材料。研究了热解碳(PyC)/SiC界面相对复合材料的微观结构和力学性能的影响。弯曲性能通过三点弯曲法测试,复合材料的断口和抛光面通过扫描电镜观察。结果表明:通过等温化学气相沉积法在纤维表面沉积PyC/SiC界面相以后,复合材料的三点抗弯强度从46MPa提高到247MPa。沉积界面的复合材料断口有明显的纤维拔出现象,纤维与基体之间的结合强度适当,起到了增韧作用;而未沉积界面相复合材料的断口光滑、平整,几乎没有纤维拔出,纤维在热解过程中受到严重的化学损伤,性能下降严重,材料表现为典型的脆性断裂。  相似文献   

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