SiC-Si-ZrSiO_4 Multiphase Oxidation Protective Coating for Carbon/Carbon Composites

In order to improve the anti-oxidation property of carbon/carbon （C/C） composites, a novel SiC-Si-ZrSiO4 multiphase oxidation protective coating was produced on the surface of C/SiC coated carbon/carbon compo ites by a pack cementation technique. The phase composition and microstructure of the as-prepared coatings were characterized by XRD （X-ray diffraction）, SEM （scanning electron microscopy） and EDS （energy dispersive spectroscopy）. Oxidation behavior of the multiphase coated C/C composites was also investigated. It showed that the as-prepared coating characterized by excellent oxidation resistance and thermal shock re- sistance could effectively protect C/C composites from oxidation at 1773 K for 57 h in air and endure the thermal cycle between 1773 K and room temperature for 12 times, whereas the corresponding weight loss is only 1.47%. The excellent oxidation protective ability of the SiC-Si-ZrSiO4 coating could be attributed to the C/SiC gradient inner layer and the multiphase microstructure of the coating.     

W-Mo-Si/SiC Oxidation Protective Coating for Carbon/Carbon Composites

A W-Mo-Si/SiC double-layer oxidation protective coating for carbon/carbon （C/C） composites was prepared by a two-step pack cementation technique. XRD （X-ray diffraction） and SEM （scanning electron microscopy）results show that the coating obtained by the first step pack cementation was a thin inner buffer layer of SiC with some cracks and pores, and a new phase of （WxMo1-x）Si2 appeared after the second step pack cementation. Oxidation test shows that, after oxidation in air at 1773 K for 175 h and thermal cycling between 1773 K and room temperature for 18 times, the weight loss of the W-Mo-Si/SiC coated C/C composites was only 2.06%. The oxidation protective failure of the W-Mo-Si/SiC coating was attributed to the formation of some penetrable cracks in the coating.     

高温氧化及热震对SiC/ZrB2-SiC/SiC涂层炭/炭复合材料力学行为的影响

为提高炭/炭(C/C)复合材料的高温抗氧化性能,同时分析涂层制备及高温氧化对涂层材料力学行为的影响,在C/C复合材料表面采用反应熔渗、料浆涂刷结合化学气相沉积工艺制备了SiC/ZrB2-SiC/SiC三层高温抗氧化涂层。利用SEM和XRD分析复合涂层的微观结构和相组成,考察涂层复合材料1500℃高温抗氧化和1500℃-室温的抗热震性能,研究高温氧化及热震对涂层C/C复合材料力学行为的影响。结果表明,复合涂层试样1500℃静态空气环境下具有优异的抗氧化及抗热震性能:1500℃氧化20 h后试样保持增重,1500℃至室温热震50次后增重为0.69%。因涂层制备过程中粉料的渗入反应,复合材料弯曲强度增长了7.08%。在经历1500℃氧化20 h和1500℃至室温50次热震后,涂层复合材料弯曲强度有所下降,且因材料界面结合力的减弱使得纤维拔出特征明显,材料塑性断裂特征增强。     

Si-Al-Ir Oxidation Resistant Coating for Carbon/Carbon Composites by Slurry Dipping

A Si-Al-Ir oxidation resistant coating was prepared for SiC coated carbon/carbon composites by slurry dipping. The phase composition, microstructure and oxidation resistance of the as-prepared Si-Al-Ir coating were studied by XRD (X-ray diffraction), SEM (scanning electron microscopy), and isothermal oxidation test at 1773 K in air, respectively. The surface of the as-prepared Si-Al-Ir coating was dense and the thickness was approximately 100 μm. Its anti-oxidation property was superior to that of the inner...     

C/SiC/Si-Mo-Cr复合涂层碳/碳复合材料力学性能研究

采用包埋法和涂刷法在碳/碳复合材料表面制备了一种新型的C/SiC/Si-Mo-Cr复合高温抗氧化涂层. 借助XRD和SEM等测试手段对所制备复合涂层的微观结构进行了表征, 采用三点弯曲试验研究了涂层处理及热震试验对碳/碳复合材料力学性能的影响规律. 结果表明: 制备的多相涂层结构致密, 涂层后碳/碳复合材料弯曲强度有所增大, 断裂特征由假塑性向脆性转变. 涂层试样经1500℃至室温20次热震后, 涂层试样的弯曲强度降低, 塑性增强.     

包埋浸渗/气相沉积二步法在C/C复合材料表面制备SiC涂层

采用包埋浸渗法和化学气相沉积(CVD)法相结合在炭/炭(C/C)复合材料表面制备了SiC涂层, 借助扫描电镜、能谱分析以及X射线衍射等检测手段对涂层的微观组织形貌、元素分布和物相组成进行了观察与分析. 结果表明:包埋法制备的SiC涂层与C/C复合材料基体的界面处形成了梯度过渡层, CVD法制备的涂层十分致密, 有效填充了包埋SiC涂层中的孔隙, 因此, 二步法制备的SiC涂层具有良好的防氧化性能, 涂层试样在1500℃静态空气中氧化60h失重率仅为2.01%. 试样失重的主要原因是其在高低温热循环过程中氧气从涂层中的微裂纹扩散至基体表面, 从而引起基体氧化所致.     

用气相反应法制备C/C复合材料的梯度SiC涂层

本文采用化学气相反应法（CVR）制备了C/C复合材料的梯度SiC涂层,对该梯度涂层的形成机理及抗氧化性能进行了试验研究.研究结果表明：Si渗入基体的速率对梯度涂层的形成产生直接的影响,当采用体密度较高的C/C基体时,得到了完整致密的梯度SiC涂层,生成的SiC为β-SiC,该涂层具有较好的高温抗氧化能力,在1500℃静态空气气氛中,氧化26小时后失重不超过2%.     

掺杂改性C/C复合材料研究进展

陶瓷掺杂改性碳/碳(C/C)复合材料在保持C/C复合材料原有优异高温力学性能及尺寸稳定性等特性的前提下,显著提高了C/C复合材料的高温抗氧化、抗烧蚀性能,且其具有可设计性和良好的抗热震性能等优势,是新型高超声速飞行器和新一代高性能发动机热防护部件的理想候选材料。综述了国内外在SiC陶瓷掺杂改性C/C复合材料,ZrC,ZrB2超高温陶瓷掺杂改性C/C复合材料以及TaC,HfC超高温陶瓷掺杂改性C/C复合材料等方面的最新研究进展和应用情况,并分析了陶瓷掺杂改性C/C复合材料目前研究及应用中存在的主要问题和今后潜在的研究发展方向。     

C/C复合材料SiC-MoSi2-TiSi2涂层的设计与性能

为了提高C/C复合材料的高温抗氧化性能,设计了网状的SiC填充高性能的MoSi2和微量的TiSi2涂层。用包埋法制备了C/C复合材料SiC-MoSi2-TiSi2复相陶瓷单层涂层,对制备涂层的化学形成机理进行了分析。结果表明,在选择的实验条件下,制备设计的涂层是完全可行的,实验制备的涂层在1773K有氧环境下具有良好的抗氧化性能。涂层抗氧化性能的提高是因为在高温氧化下涂层表面产生了致密、连续、稳定的玻璃质氧化物。     

Multi-layer CVD-SiC/MoSi2–CrSi2–Si/B-modified SiC oxidation protective coating for carbon/carbon composites

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.     

C/C复合材料高温长寿命抗氧化复合涂层研究

采用包埋技术在C/C复合材料表面制备SiC-WSi₂/MoSi₂抗氧化复合涂层; 通过恒温氧化实验以及X射线衍射分析、扫描电镜观察及能谱分析, 研究了W、Mo含量对复合涂层微观结构和高温抗氧化性能的影响. 结果表明: 随着包埋粉料中W、Mo含量的增加, 所制备复合涂层的厚度先增加后减小; 含有10.0at％ W和Mo制备的复合涂层具有相对较大的厚度和较为致密的结构, 且WSi₂和MoSi₂含量相对较高; 氧化过程中在涂层表面形成致密和稳定的SiO₂玻璃保护膜; 在1500℃氧化315h后, 带有该涂层的C/C试样仍然没有失重, 且经过18次1500℃←→室温急冷急热后涂层没有开裂和脱落, 说明该涂层具有优异的抗氧化和抗热震性能.     

High-temperature stability of Nicalon under Ar or O2 atmosphere

The thermal stability of Nicalon NL400 at 1573, 1673 and 1773 K has been studied by TGA and XRD. Under an Ar atmosphere, Nicalon pyrolysed severely to crystallize into -SiC involving the generation of both SiO and CO. Under an O₂ atmosphere, the oxide film which formed around Nicalon retarded the pyrolytic reaction of the core. Nicalon coated with a silica film by the previous oxidation treatment pyrolysed hardly at all under an Ar atmosphere, because the film restricted the escape of SiO and CO. Nicalon which was oxidation-treated at 1773 K retained 63% of its original strength after heating at 1773 K under an Ar atmosphere. The amorphous silica film was found to resist rapid thermal cycling between room temperature and elevated temperatures.     

超高温本体抗氧化碳/碳复合材料研究

通过向碳/碳复合材料基体中掺杂难熔金属化合物,研制出了一类集碳/碳材料优异的高温力学、热物理性能和超高温陶瓷材料非烧蚀性能于一体的超高温本体抗氧化碳/碳复合材料。攻克了难熔金属化合物在复合材料中分布以及组元与碳纤维反应控制关键技术,提高了复合材料的力学性能。静态和动态高频等离子风洞超高温本体抗氧化试验表明,在驻点温度达到2 500℃,600 s烧蚀后烧蚀量仅为碳/碳复合材料的1/5,给出了超高温本体抗氧化碳/碳复合材料氧化烧蚀抑制机理。     

化学气相沉积碳／碳复合材料性能研究

分析了化学气相沉积碳／碳（Ｃ／Ｃ）复合材料的刹车力矩和刹车速度的关系曲线及影响因素，结果表明，刹车力矩一刹车速度曲线上的初始力矩峰值随着摩擦界面温度的升高而增大，提高材料的石墨化度、改变刹车盘的结构、降低刹车比压的施加速度都可以降低初始力矩峰值，改善Ｃ／Ｃ材料的摩擦性能．Ｃ／Ｃ复合材料具有良好的自润滑性能，其磨损率仅为１．２×１０－３ｍｍ／次．它们具有较高的机械性能和热物理性能，完全可以满足飞机刹车的要求．     

The degradation behavior of SiC coated PIP-C/SiC composites in thermal cycling environment

C/SiC composites had been considered as structural material in complex and harsh environments, thermal stability was one of the key issues for C/SiC composites. This study aimed to investigate C/SiC composites in thermal cycling environment. SiC coating on carbon fibers via chemical vapor deposition at time from 0.5 h to 5 h was studied, and then the degradation behavior of coated C/SiC composites had been measured by thermal cycling tests. The results showed that the coating was continuous and uniform, with good surface adhesion. The interface of carbon fibers and SiC coating was partially destroyed during thermal shock tests. The degradation of mechanical properties was closely related to the evolution of the damage in the composites.     

碳纤维在高温下的结构、性能演变研究

针对碳纤维在碳/碳烧蚀防热复合材料中应用的基础问题,论述了不同碳纤维结构、成分、表面特征,及其力学性能和热物理性能的高温演变规律,揭示了碳纤维灰分含量对碳纤维力学性能和热氧化性能的影响。确定了在碳/碳复合材料复合成型过程中,碳纤维结构受基体碳影响的变化规律和碳纤维表面特征对碳/碳材料宏观力学性能的影响。阐明了碳/碳复合材料中碳纤维的力学性能对纤维发生折断烧蚀的阻碍作用和通过控制碳/碳成型最高温度实现提高性能的途径。     

Electroactive Shape Memory Effect of Polyurethane Composites Filled with Carbon Nanotubes and Conducting Polymer

We report the electroactive shape memory composites obtained by shape memory polyurethane block copolymer (PU) and multi-walled carbon nanotubes (MWNTs), and polypyrrole (PPy). An addition of combined MWNTs and PPy contributed to an enhancement in conductivity of PU-MWNTs composites. PU containing 2.5% MWNTs showed better mechanical and thermal properties than other composites, but conductivity was not sufficient for showing the shape memory effect by applying electrical voltages. However, when the composite was lightly coated by PPy (2.5%), its conductivity was the highest than other composites. Such the conductivity of this composite was enough to show electroactive shape recovery by heating above transition temperature of 40-48°C due to melting of polycaprolactone soft segment domain. The good shape recovery of 90-96% could be obtained in the shape recovery test when an electric field of 25 V was applied.     

The effect of thermoplastic coating on the mechanical properties of woven fabric carbon/epoxy composites

The effect of a polyetherimide (PEI) coating on the mechanical properties of woven fabric carbon/epoxy composites was investigated by thermal mechanical analysis, fractographical analysis and mechanical properties measurements. PEI coating enhanced the mechanical properties of carbon/epoxy composites mainly through the improvement of matrix properties. This was because most of the PEI coated on the carbon fiber diffused into the bulk of epoxy matrix due to its good miscibility with epoxy resin. As for mechanical properties of woven fabric carbon/epoxy composites, the extent of improvement by PEI coating highly depended on the applied stress state. Among the mechanical properties, mode II delamination resistance of carbon/epoxy composites showed the highest increment because matrix shear property played an important role in delamination resistance of woven fabric carbon/epoxy composite. Because of the woven geometry of carbon fiber, the improvement in impact property of carbon/epoxy composite was trivial except the large amount of PEI coated case.     

微波烧结制备ZrO2-AlN复合陶瓷的微观结构与性能研究

氧化锆(ZrO₂)陶瓷具有出色的机械性能, 但其应用受到低热导率(Thermal Conductivity, TC)的限制。本研究设计并通过微波烧结制备了高热导率氧化锆-氮化铝(AlN)复合陶瓷, 优化制备条件后, 抑制了两种物质之间的反应, 获得了致密的复合陶瓷(相对密度>99%), 详细研究了该复合陶瓷的组织演变、热学性能和力学性能。研究结果表明, 随着AlN含量的增加, 复合陶瓷的室温下热导率、热扩散系数和热容增加, 分别达到41.3 W/(m·K)、15.2 mm²/s和0.6 J/(g·K)。这种具有高热导率和抗热震性的ZrO₂-AlN复合复合陶瓷在能源系统的高温热交换材料领域具有广阔的应用前景。     

炭/炭复合材料表面C/SiC/Si-Mo-Cr多层复合防氧化涂层研究(英文)

为提高炭/炭(C/C)复合材料的高温抗氧化性能,采用料浆涂刷法首先在C/C复合材料表面制备了预炭层,然后以Si粉及石墨粉(Si粉与石墨粉的质量配比为:60～80:10～25)为原材料采用包埋法经高温热处理获得C/SiC内涂层,最后在涂有C/SiC内涂层的C/C复合材料表面采用包埋法制备Si-Mo-Cr外涂层。借助扫描电镜、X射线衍射、电子能谱等分析测试手段对涂层试样的微观结构进行了分析,研究了涂层C/C复合材料在1 873 K和1 973 K下的氧化行为。结果表明:由于涂层氧化过程中表面生成了SiO2和Cr2O3复合玻璃层,其在1 873 K温度下表现出优异的防氧化性能,可以有效保护C/C复合材料达135 h。当氧化温度提高至1 973 K并氧化30 h后,该复合涂层氧化过程玻璃层完整性被破坏,涂层失效。