界面对浆料浸渍裂解Cf/SiC复合材料性能的影响

利用强制脉冲CVI工艺在2.5D纤维编织体上沉积C-SiC双层界面,然后通过浆料浸渍裂解方法得到了Cf/SiC复合材料,并考察界面中C层、SiC层厚度变化对Cf/SiC复合材料性能的影响.界面中C层、SiC层厚度变化对浸渍过程影响不大,得到的Cf/SiC复合材料密度基本相当,约2.0 g/cm3.但随C层厚度的增加,强度减小;随着SiC层厚度的增加,强度增加,到达一定厚度后,其强度几乎不变,为290.0 MPa.在C层厚度为50 nm,SiC层厚度为600 nm时,表现出强的非脆性断裂.     

陶瓷先驱体聚硅氮烷连接Cf/SiC工艺及连接性能

采用陶瓷先驱体转化法连接Cf／SiC复合材料。针对Cf／SiC复合材料的不同连接界面特性,采用不同的连接配方和工艺。结果表明：对于第一类以SiC相为主的连接界面,采用单一的聚硅氮烷即可实现Cf／SiC复合材料的连接,当连接温度为1300℃,经两次浸渍／裂解增强处理的连接件接头抗剪强度达最大值29．6MPa;连接层厚度为2～3μm,其结构较为均匀致密,由无定型SiNC陶瓷组成;对于第二类以C纤维端面为主的连接界面,采用聚硅氮烷并加入活性填料纳米Al粉来实现其连接：当连接温度为1150℃,经两次浸渍／裂解增强处理的连接件抗剪强度达最大值22．5MPa;连接层厚度约为30μm,连接层中含有SiC、Si3N4和AlN等相。     

Cf／ZrC—ZrB2-SiC—C超高温陶瓷复合材料的显微结构表征

利用X-射线衍射、扫描电子显微镜和透射电子显微镜对Cf／ZrC-ZrB2-SiC-C超高温陶瓷复合材料的相组成、纤维／热解碳层的界面特征和超高温陶瓷基体的显微结构特征进行了表征。在碳纤维表面有一层厚度为2～3μm石墨化程度较高的热解碳界面层,该界面层可以避免采用PIP工艺制备超高温陶瓷基体时可能对碳纤维造成的损伤。热解碳层与碳纤维之间为弱机械结合,其界面间分布着20～30nm的ZrC纳米颗粒。Cf／ZrC—ZrB2-SiC—C超高温陶瓷复合材料基体主要由ZrC,ZrB2,SiC和石墨相（Cg）组成。基体中石墨的（002）面沿着ZrC,ZrB2或SiC的表面生长。在石墨与ZrB2和石墨与SiC的界面没有观察到取向关系,界面处既没有反应层也没有非晶相存在。在石墨与ZrC之间存在ZrC（111）／／Cg（002）,ZrC[110]／／Cr[010]的取向关系。ZrB,和SiC之间也没有界面反应和非晶层存在。     

Cf／SiC陶瓷基复合材料的制备工艺研究

以先驱体浸渍裂解（PIP）工艺制备了2DC／SiC复合材料，研究了低温裂解工艺（裂解温度低于1000℃）对2D Cf/SiC复合材料结构和性能的影响，为Cf／SiC复合材料的低温制备探索可行之路。研究表明，采用900℃裂解工艺制备的复合材料其力学性能达到或高于目前同类工艺制备的2D Cf／SiC复合材料力学性能，其弯曲强度达到329．6MPa，剪切强度32．1MPa，断裂韧性14．7MPa·m^1/2。并采用差热（TG-DTA）、红外光谱（IR）、X射线衍射（XRD）等对先驱体聚碳硅烷（PCS）及其低温裂解产物的结构和性能进行了研究。     

SiC颗粒增强Al-Fe-V-Si复合材料的SiC/Al界面形貌

采用喷射沉积工艺制备SiCp/Al-Fe-V-Si复合材料,并通过热压和热轧工艺对沉积坯进行致密化;通过高分辨电镜观察其SiC/Al界面形貌,并对比热暴露后的界面形貌。结果表明:复合材料主要存在两种SiC/Al界面,一种是厚度为3nm左右的晶态Si界面层,且在界面附近的基体中生成细小的Al4C3相;另一种是厚度为5nm的非晶态SiO2界面层,部分溶解的SiC颗粒向附近Al基体中注入游离态的Si,在界面附近形成Si的浓度梯度;两种界面都具有良好的润湿性,界面结合强度高;经640℃热暴露10h后,SiC/Al界面处生成的粗大Al4C3脆性相降低界面结合强度,从而降低复合材料的力学性能。     

SiCf/Ti-6Al-4V复合材料界面反应动力学

SiC纤维增强Ti基复合材料（SiCf／Ti）容易发生界面反应，从而影响其力学性能。开展界面反应和动力学的研究，对于SiCdTi复合材料的制备和服役具有指导意义。采用扫描电镜、透射电镜和X射线衍射分析了SICf／Ti-6Al—4V复合材料的界面反应及其动力学，发现SiC纤维的C涂层与Ti-6Al—4V反应形成粗晶粒的和细晶粒的TiC，长期高温热处理使得界面反应加剧，TiC层加厚，当C涂层完全消耗后，界面反应层中除了TiC外，还出现了Ti3SiC2。研究表明，界面反应层的加厚受元素扩散控制，服从抛物线规律，求出的动力学参数Q为268．8kJ／mol，k为0．0057m/s1/2。     

C_f/SiC复合材料与钛合金Ag-Cu-Ti-C_f复合钎焊

采用Ag-Cu-Ti-Cf(Cf:碳纤维)复合钎料作中间层,在适当的工艺参数下真空钎焊Cf/SiC复合材料与钛合金,利用SEM,EDS和XRD分析接头微观组织结构,利用剪切试验检测接头力学性能.结果表明,钎焊时复合钎料中的钛与Cf/SiC复合材料反应,在Cf/SiC复合材料与连接层界面形成Ti3SiC2,Ti5Si3和少量TiC化合物的混合反应层.复合钎料中的铜与钛合金中的钛发生互扩散,在连接层与钛合金界面形成不同成分的Cu-Ti化合物过渡层.钎焊后,形成碳纤维强化的致密复合连接层.碳纤维的加入缓解了接头的残余热应力,Cf/SiC/Ag-Cu-Ti-Cf/TC4接头抗剪强度明显高于Cf/SiC/Ag-Cu-Ti/TC4接头.     

(Ag-Cu-Ti)+(Ti+C)复合钎料钎焊Cf/SiC复合材料与TC4钛合金

Ag-Cu-Tj复合钎料中加入Ti粉和石墨碳粉作为中间层,在适当的工艺条件下真空钎焊Cf/SiC复合材料与TCA.利用SEM,EDS,XRD分析接头微观组织,利用剪切试验检测接头力学性能.结果表明:钎焊时,复合钎料中的Ti与Cf/SiC复合材料反应,在Cf/SiC复合材料与连接层界面形成由Ti3、SiC2相、Ti5Si3相和少量TiC化合物组成的混合反应层.复合钎料中的Cu与Ti合金中的Ti发生互扩散,在连接层与Ti合金界面形成不同Ti含量的Cu-Ti化合物过渡层.钎焊后,连接层中Ti和石墨碳反应形成的TiC微粒均匀分布在复合连接层中,缓和了接头的热应力.当连接温度为910℃,保温时间为25 min时,可得到接头剪切强度为145 MPa.     

SiC界面涂层对碳纤维针刺毡增强Al_2O_3复合材料力学性能的影响（英文）

分别采用3D碳纤维针刺毡为增强体以及聚碳硅烷(PCS)衍生SiC涂层为界面相,通过溶胶-浸渍-干燥-热处理(SIDH)技术制备C/Al_2O_3复合材料,研究SiC界面涂层对C/Al_2O_3复合材料力学性能、抗氧化性能和抗热震性能的影响。结果表明,C/Al_2O_3复合材料的断裂韧性显著优于Al_2O_3单体陶瓷,引入SiC界面涂层后,尽管断裂功有一定程度下降,但C/Al_2O_3复合材料的强度得到明显提高;得益于SiC涂层和C纤维之间的强结合,C/SiC/Al_2O_3复合材料在静态空气中表现出明显优于C/Al_2O_3复合材料的抗氧化和抗热震性能。     

Cf/SiC复合材料与钛合金(Ti-Zr-Cu-Ni)+W复合-扩散连接

采用(Ti-Zr-Cu-Ni)+W复合钎料作为连接层,在连接温度930℃,保温时间5min的工艺参数下真空钎焊Cf/SiC复合材料与钛合金.利用SEM,EDS和XRD分析接头微观组织结构,利用剪切试验测试接头力学性能.结果表明,钎焊时复合钎料中的钛、锆与C/SiC复合材料反应,在Cf/SiC复合材料与连接层界面生成Ti3SiC2,Ti5Si3和少量TiC(ZrC)化合物的混合反应层,连接层的铜、镍与钛合金中的钛发生相互扩散,在连接层与钛合金界面形成Ti-Cu化合物过渡层.对钎焊接头进行900℃,保温60 min扩散处理后,连接层组织达到均一化,母材TC4合金侧过渡层增厚.扩散处理后接头强度为99 MPa,较钎焊接头强度65 MPa提高了52％.     

碳化硅复合材料与碳钢钎焊接头的抗剪强度及微观结构

采用磁控溅射镀膜技术对碳/碳化硅复合材料(C/SiC)表面进行镀Ti金属化,以AgCu₂₈为钎料,无氧铜为中间层与碳钢进行钎焊连接. 研究无氧铜中间层、Ti膜厚度和钎焊温度对接头组织形貌和力学性能的影响. 结果表明,采用无氧铜中间层可有效降低接头的残余应力,提高接头强度,并阻挡C/SiC复合材料中的Si元素在钎焊过程中扩散至碳钢侧,防止了碳钢界面FeSi_x恶性反应层的形成. 在试验范围内,钛膜厚度和钎焊温度与接头抗剪强度之间均存在峰值关系. 860 ℃,3 μm Ti膜接头平均抗剪强度最高,达到25.5 MPa. 由剪切试样碳钢侧断口,可观察到大量平行断口方向的碳纤维和碳纤维脱粘坑. 断裂发生在C/SiC复合材料内部距界面约300 μm处. C/SiC界面反应产物以Ti₅Si₃为主,含少量TiC. 钎缝中有TiCuSi相生成.     

表面硅化对C/C复合材料组织结构的影响

采用表面固相渗硅工艺在C/C复合材料表面制备SiC涂层 ,研究了制备工艺对涂层和C/C复合材料组织结构的影响。结果表明 :硅化反应时间对C/C复合材料的SiC涂层厚度影响不大 ;C/C复合材料组织中热解碳基体与碳纤维相比 ,更易与Si反应生成SiC ,说明碳纤维的稳定性高于热解碳 ,Si通过界面和材料缺陷扩散深入基体内部。     

Microstructure of a Mo-Si-C-N multi-layered anti-oxidation coating on carbon/carbon composites by fused slurry

A Mo-Si-C-N multi-layered anti-oxidation coating was in-situ fabricated by introducing nitrogen atmosphere during the fused sintering of Mo-Si slurry pre-layer on carbon/carbon composites. The phase composition and microstructure of the Mo-Si-C-N coating were character-ized by X-ray diffractometry, optical microscopy, scanning electron microscopy with energy dispersive spectroscopy, X-ray photoelectron spectroscopy, and transmission electron microscopy. The Mo-Si-C-N coating exhibited a three-layered structure. Besides the MoSi2/Si main-layer and the SiC bonding-layer, a surface layer of about 10 μm in thickness was synthesized on the coating surface. The surface layer mainly consisted of SiC nanowires and contained some Si3N4 and Si phases. SiC nanowires of 10 to 200 nm in diameter presented a terrace and distortion structure. Transmission electron microscopy indicated that the SiC nanowires grew along the preferred <111> direction. Dur-ing oxidation test, SiC nanowires transmuted into Sit2 glass, which can play an important role in improving the oxidation resistance of C/C composites.     

界面反应对SiC纤维增强钛基复合材料界面剪切强度的影响

利用考虑界面反应层的有限元模型,分析了界面反应对复合材料界面剪切强度的影响.有限元预测得出,界面剪切强度随着界面反应增强而增大.并且,建立了界面反应层厚度和界面剪切强度的关系式.     

Joining of C/C Composites and GH3128 Ni-based Superalloy with Ni-Ti Mixed Powder as an Interlayer

通过包埋工艺在C/C复合材料表面制备了改性SiC涂层.采用Ni-Ti粉末作中间层连结材料,利用真空热压扩散工艺成功制备了SiC涂层改性C/C复合材料与GH3128镍基高温合金的连接样件.借助X射线衍射仪、扫描电子显微镜、能谱分析仪和材料万能试验机,研究了SiC涂层改性C/C复合材料与GH3128镍基高温合金连接接头及其界面的元素分布、微观结构及力学性能.结果表明,在C/C复合材料表面制备SiC涂层,不仅充分改善了C/C复合材料对Ni-Ti中间层连结材料的润湿性,而且还有效缓解C/C复合材料与GH3128连接界面因热膨胀不匹配而造成的热应力.经过SiC涂层改性处理的连接接头,其室温剪切强度可达22.49 MPa;而没有经过SiC涂层改性处理的连接接头,其室温剪切强度几乎为零.     

Microstructure and mechanical properties of 3D fine-woven punctured C/C composites with PyC/SiC/TaC interphases

The 3D fine-woven punctured C/C-(P_yC/SiC/TaC) composites, composed of P_yC/SiC/TaC interphases and pyrocarbon (PyC) matrix, were synthesized by isothermal chemical vapor infiltration (ICVI) methods. The alternating layers and the structure of these composites were examined by polarized light microscopy (PLM), X-ray diffractometry (XRD) and scanning electron microscopy (SEM). It is found that the P_yC matrix has rough laminar (RL) structure, the TaC layer has NaCl-type cubic structure, and the SiC layer has few wurtzite type 10H-SiC besides β-SiC structure. The effects of fiber coating and the bulk density on the tensile and flexural properties of composites along X or Y and Z direction were investigated. It is shown that fiber coated 3D woven punctured C/C composites have good tensile and flexural strength, and the maximum of flexural strength is 375 MPa in X or Y direction at density of 1.89 g/cm³, which is about three times higher than that of samples without TaC/SiC fiber coating. The flexural strength and bending strength increase with increasing the density of the composites. The analysis of fracture surfaces reveals that fibers and fiber bundles are pulled out in composites, indicating that the composite exhibits a non-linear failure behavior through propagation and deflection of the cracks.     

Effect of C/SiC Volume Ratios on Mechanical and Oxidation Behaviors of Cf/C-SiC Composites Fabricated by Chemical Vapor Infiltration Technique

C/SiC volume ratios in carbon fiber-reinforced carbon-silicon carbide (C_f/C-SiC) composites may influence greatly mechanical and oxidation properties of the composites, but have not been well investigated yet. Herein, C_f/C-SiC composites with different C/SiC volume ratios were fabricated by chemical vapor infiltration (CVI) technique through alternating the thickness of a pyrocarbon (PyC) interlayer. The composites with C/SiC volume ratios of 0.37 and 0.84 exhibited the better comprehensive mechanical properties. The CS0.37 showed the highest flexural strength of 340.6 MPa, and CS0.84 had the maximum tensile strength of 139.1 MPa. The excellent mechanical properties were closely related to the relatively low C/SiC volume ratios and porosities, optimum interfacial bonding and reduced matrix micro-cracks. The composite with a low C/SiC volume ratio of 0.10 showed the best anti-oxidation performance due to its high SiC content. The oxidation mechanisms at 1100 °C and 1400 °C were discussed by considering the effect of the C/SiC volume ratios, pores and matrix micro-cracks, oxidation of carbon phase and SiC.     

C/SiC复合材料表面状态对其与Nb钎焊的影响

采用等原子比Ti-Ni复合箔对C/SiC复合材料与Nb进行了真空反应钎焊,研究了焊前C/SiC表面状态对接头界面组织和力学性能的影响.结果表明,线切割态的C/SiC与Nb的接头界面(Ti,Nb)C反应层呈现锯齿状,而抛光和砂纸打磨状态的C/SiC接头界面处的反应层平直.锯齿状的界面反应层降低了界面处的应力集中程度,有助于提高接头的力学性能,使得线切割态的C/SiC与Nb的接头强度明显高于抛光和打磨状态的接头,达到188MPa.线切割态的C/SiC与Nb的接头断裂同时发生在C/SiC母材、界面和钎缝中,而抛光和打磨状态的C/SiC与Nb的接头断裂主要发生在界面处.     

W-SiC-C/C复合材料制备及等离子烧蚀性能

目的提高C/C复合材料在超高温下的抗烧蚀性能。方法采用化学气相沉积法,在C/C复合材料表面制备SiC过渡层,然后以惰性气体保护等离子喷涂工艺在带有SiC过渡层的C/C材料表面制备W涂层,研究所制备的W-SiC-C/C复合材料的微观形貌与结构特征。以200 kW超大功率等离子焰流,考核W-SiC-C/C材料的抗烧蚀性能,并与无涂层防护的C/C材料进行对比分析。结果W涂层主要为层状的柱状晶结构。W涂层与SiC过渡层、过渡层与基体界面呈镶嵌结构,结合良好。SiC过渡层阻止了W、C元素相互迁移与反应。在驻点压力为4.5 MPa、温度约5000 K、热流密度为36 MW/m²的烧蚀条件下,当烧蚀时间小于10 s时,涂层对C/C材料起到了较好的保护作用,W涂层发生氧化烧蚀,基体未发现烧蚀,平均线烧蚀率为0.0523 mm/s;当烧蚀时间超过15 s后,涂层防护作用基本失效,基体C/C材料发生烧蚀现象。结论以W涂层、SiC过渡层为防护的C/C复合材料,能够适用于短时间超高温的烧蚀环境,如固体火箭发动机等。W涂层的熔融吸热、氧化耗氧以及SiC过渡层的氧化熔融缓解涂层热应力和氧扩散阻碍的联合作用,提高了C/C材料的抗烧蚀性能。     

SiC Coatings for Carbon/Carbon Composites Fabricated by Vacuum Plasma Spraying Technology

SiC coatings for carbon/carbon (C/C) composites have been prepared by the combination process of vacuum plasma spraying technology and heat treatment. The SiC coatings were formed by the reaction of C/C substrates with as-sprayed silicon coatings deposited by vacuum plasma spraying. The preparation temperature and the thickness of original silicon coatings have great influence on the microstructure and the thickness of the synthesized SiC coatings. The results indicated that a continuous and dense SiC coating has been produced on the surface of C/C substrates. The SiC coatings prepared at 2073 K with the silicon coatings of 230 μm thickness, exhibited a low mass loss of 2.56% in the plasma jet with temperature about 2473 K and duration of 420 s in atmosphere. The present results implied that vacuum plasma spraying technology combined with heat treatment was an acceptable method for synthesis of protective SiC coatings for C/C composites.