Thermal Fatigue Behavior of SiC/MBAS Glass Coated Carbon/Carbon Composites

The thermal fatigue behavior of C/C composites coated with the SiC/MBAS glass (MoSi2 particle-containing boron aluminosilicate glass) coating, prepared by the two-step process of the pack cementation and procoating-sintering, was investigated in present paper. The experimental results indicated that the SiC/MBAS glass coating had an excellent thermal shock resistance in air at temperature up to 1873 K. During quick thermal cycle between 1873K and room temperature in air, the decrease of mass and mechanical ...     

A MoSi2-SiC-Si oxidation protective coating for carbon/carbon composites

To protect carbon/carbon (C/C) composites from oxidation, a dense coating has been produced by a two-step pack cementation technique. XRD and SEM analysis shows that the as-obtained coating was composed of MoSi₂, SiC and Si with a thickness of 80-100 μm. The MoSi₂-SiC-Si coating has excellent anti-oxidation property, which can protect C/C composites from oxidation at 1773 K in air for 200 h and the corresponding weight loss is only 1.04%. The weight loss of the coated C/C composites is primarily due to the reaction of C/C substrate and oxygen diffusing through the penetration cracks in the coating.     

Effect of Mo/Si Ratio on the Microstructure and Oxidation Resistance of Si-Mo Coating for C/C Composites

Oxidation protective Si-Mo coatings were prepared by pack cementation on the surface of C/SiC coated carbon/carbon composites. The influences of Mo/Si mass ratio in the pack powders on the microstructure and oxidation resistance of the coating were investigated. It showed that with the Mo/Si ratio increasing from 0.1 to 0.4, the MoSi2 proportion and the dimension of cracks in the coating increased, and the oxidation protective ability of the coated specimens firstly increased and then decreased. The coating...     

磁控溅射法制备碳/碳复合材料 SiC/MoSi2-ZrB2 涂层的结构及抗氧化性能研究

通过磁控溅射法在碳/碳复合材料表面成功制得了SiC/MoSi2-ZrB2陶瓷涂层并对结构及其在高温有氧环境中的抗氧化性能进行了研究。结果表明制备的SiC/MoSi2-ZrB2陶瓷涂层呈柱状晶结构且均匀性良好,其在1273K和1773K的有氧环境中氧化60min失重率分别是5.6×10-2 g/cm2 和 6.3×10-2 g/cm2。     

TaSi2 Oxidation Protective Coating for SiC Coated Carbon/Carbon Composites

为提高碳/碳复合材料在高温下的氧化防护性能,利用包埋技术在碳/碳复合材料表面制备了TaSi2/SiC复合涂层。通过XRD、SEM 和 EDS分析了涂层的晶相结构和形貌特征,在1773 K的空气介质中对TaSi2/SiC涂层碳/碳复合材料进行等温氧化实验。结果表明,复合涂层厚度为200 μm,涂层中含有SiC, Si 和TaSi2相,并且涂层中没有明显裂纹出现。EDS结果显示外层TaSi2相可有效地填充内层SiC涂层的空隙,使得内外两层涂层之间没有明显的界面,等温氧化实验曲线说明TaSi2/SiC复合涂层在1773 K的空气介质中可有效保护碳/碳复合材料233 h。     

Microstructure and anti-oxidation property of Si-W-Cr coating for SiC coated carbon-carbon composites

To protect carbon/carbon (C/C) composites from oxidation at high temperature, a Si-W-Cr coating was prepared on the surface of SiC coated C/C composites by a simple pack cementation technique. The microstructure and phase composition of the as-received multi-coating were examined by SEM, XRD and EDS. The coating obtained by first step pack cementation was porous α-SiC structure. New phases of WSi₂ and CrSi₂ together with α-SiC deposited on the porous SiC inner layer. Oxidation test shows that the weight loss of single SiC coated C/C is up to 8.21% after 9 h in air at 1773 K, while the weight loss of Si-W-Cr/SiC coated C/C composites is only 2.26% after 51 h. After thermal cycling between 1773 K and room temperature for 40 times, the weight loss is only 3.36%. The weight loss of coated C/C composites was primarily due to the reaction of C/C matrix and oxygen diffusing through the penetrable cracks in the coating.     

Anti-oxidation behavior of chemical vapor reaction SiC coatings on different carbon materials at high temperatures

To protect carbon materials from oxidation, SiC coatings were prepared on carbon/carbon(C/C) composites and graphite by chemical vapor reaction. SEM and XRD analyses show that the coatings obtained are composed of SiC grains and micro-crystals. The influence of different carbon substrates on oxidation behavior of coated samples was investigated, and then their oxidation mechanisms were studied. Oxidation test shows that the SiC coated graphite has a better oxidation resistance than SiC coated C/C composites at high temperatures (1 623 K and 1 823 K). In the oxidation process, the oxidation curves of SiC coated C/C composites are linear, while those of SiC coated graphite follow a quasi-parabolic manner. The oxidation mechanism of the former is controlled by chemical reaction while the latter is controlled by oxygen diffusion based on the experimental results. The variation of oxidation behavior and mechanism of SiC coatings on two kinds of carbon substrates are primarily contributed to their structure differences.     

Double SiC coating on carbon/carbon composites against oxidation by a two-step method

To improve the oxidation resistance of C/C composites, a double SiC protective coating was prepared by a two-step technique. Firstly, the inner SiC layer was prepared by a pack cementation technique, and then an outer uniform and compact SiC coating was obtained by low pressure chemical vapor deposition. The microstructures and phase compositions of the coatings were characterized by SEM, EDS and XRD analyses. Oxidation behaviour of the SiC coated C/C composites was also investigated. It was found that the double SiC coating could protect C/C composites against oxidation at 1773 K in air for 178 h with a mass loss of 1.25%. The coated samples also underwent thermal shocks between 1773 K and room temperature 16 times. The mass loss of the coated C/C composites was only 2.74%. Double SiC layer structures were uniform and dense, and can suppress the generation of thermal stresses, facilitating an excellent anti-oxidation coating.     

热循环对SiCp／MoSi_2复合材料性能的影响

研究了热循环对ＳｉＣｐ／ＭｏＳｉ_２复合材料抗弯强度和断裂韧度的影响，并测定了材料的宏观残余应力。实验材料是用热压方法制备的ＭｏＳｉ_２和不同体积百分数（１０，２０，３０ｖｏｌ％）ＳｉＣ_ｐ增强ＭｏＳｉ_２复合材料。实验结果表明，复合材料的抗弯强度和断裂韧度都随ＳｉＣ含量的增加而增加，经过热循环以后，四种材料的抗弯强度都有不同程度的增加，而断裂韧度则下降约２０％左右。这是由于材料经过热循环以后，造成ＳｉＣｐ和ＭｏＳｉ２界面结合过强和基体晶界过弱。尽管ＳｉＣ_ｐ和ＭｏＳｉ_２热膨胀系数相差很大，但在复合材料中未发现由此而产生的裂纹和宏观残余应力。     

涂层孔隙对基体碳/碳材料的氧化损伤模拟

碳/碳（C/C）复合材料广泛应用于高超声速飞行器,其表面有碳化硅（SiC）基的保护涂层,旨在将氧气与底层基体C/C隔离。涂层中存在的孔隙成为氧气直达底层C/C材料的通道。C/C材料被氧化,侵蚀出空穴,严重时造成局部热防护失效。针对原有的气体扩散两步模型进行了改进,去掉了O₂/CO反应界面固定的限制,考虑了空穴中扩散的影响,提出了折合孔隙深度与弯曲因子的处理方法。采用改进模型模拟涂层下面C/C材料氧化空穴半径,计算值与试验测量值吻合良好,验证了模型的有效性。改进模型可用于预测涂层保护的基体C/C材料的氧化空穴尺寸和评估氧化损伤。     

ZrSiO4 Oxidation Protective Coating for SiC-Coated Carbon/Carbon Composites Prepared by Supersonic Plasma Spraying

To protect carbon/carbon (C/C) composites against oxidation, ZrSiO₄ oxidation protective coating was prepared on SiC-coated C/C composites by supersonic plasma spraying. X-ray diffraction and scanning electron microscopy were used to analyze the phase and microstructure of the coating. The results show that the as-prepared ZrSiO₄ coating is continuous and well bonded with the SiC inner layer without penetrating crack, which exhibits good oxidation-resistant properties. After oxidation at 1773 K in air for 97 h and nine thermal shock cycles between 1773 K and room temperature, the weight loss of the coated C/C composites was only 0.08%. The excellent oxidation-resistant properties of the coating were attributed to its dense structure and the formation of the stable ZrO₂-SiO₂ glassy mixture on the surface of ZrSiO₄ coating.     

Si-W-Mo coating for SiC coated carbon/carbon composites against oxidation

In order to prevent carbon/carbon (C/C) composites from oxidation at 1773 K, a Si-W-Mo coating was prepared on the surface of SiC coated C/C composites by a simple pack cementation technique. The microstructures and phase composition of the as-received multi-coating were examined by SEM, XRD and EDS. It was seen that the compact multi-coating was composed of α-SiC, Si and (W_xMo_1 − x)Si_2. Oxidation behaviour of the SiC/Si-W-Mo coated C/C composites was also studied. After 315 h oxidation in air at 1773 K and thermal cycling between 1773 K and room temperature for 17times, no weight loss of the as-coated C/C composites was measured. The excellent anti-oxidation ability of the multi-coating is attributed to its dense structure and the formation of the stable glassy SiO₂ film on the coating surface during oxidation.     

C/C复合材料航空刹车副表面防氧化涂料的研制

以磷酸,磷酸盐,ＳｉＣ,ＳｉＯ２,Ｂ４Ｃ和含硼化合物等为原料研制了以硅、硼化合物为主的多组分陶瓷混合物涂料。采用该涂料以刷涂的方式制备的Ｃ／Ｃ复合材料复合涂层具有显著的防氧化效果。研究表明,涂覆有涂层的Ｃ／Ｃ复合材料试样在９００℃氧化１０ｈ后,其氧化损失率为１０．３７％;试样在空气中９００℃,３ｍｉｎ＝室温,２ｍｉｎ急冷急热,如此在１０ｈ内循环１００次后,氧化损失率为８．４１％,涂层与基体结合牢固     

SiC nanowire-toughened SiC-MoSi2-CrSi2 oxidation protective coating for carbon/carbon composites

To prevent carbon/carbon (C/C) composites from oxidation, a dense SiC nanowire-toughened SiC-MoSi₂-CrSi₂ multiphase coating was prepared by the two-step technique composed of chemical vapor deposition (CVD) and pack cementation. The coatings were characterized by scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS) and X-ray diffraction (XRD). SiC nanowires could decrease the dimension of cracks and improve the oxidation and thermal shock resistance of SiC-MoSi₂-CrSi₂ multiphase coating. Oxidation test shows that, after introducing SiC nanowires, the weight loss of the coated sample can be reduced from 1.06% to 0.64% after oxidation at 1773 K for 155 h and decreased from 6.92% to 3.42% after thermal cycling between 1773 K and room temperature for 30 times.     

碳纤维增强Cu-Ti3SiC2自润滑复合材料的研究

介绍了碳纤维的表面处理及碳纤维增强铜基复合材料的制备工艺与性能的研究进展.三元层状碳化物Ti3SiC2兼具金属和陶瓷的优良性能,更有意义的是它具有很好的自润滑性能和比传统的固体润滑剂石墨、二硫化钼更低的摩擦系数.将Ti3SiC2弥散强化Cu与碳纤维复合强化Cu结合,制备出的复合材料,可望有效提高其自润滑性能,被认为在许多领域有着广泛的应用前景.     

SiC–MoSi2/ZrO2–MoSi2 coating to protect C/C composites against oxidation

To improve the oxidation resistance of carbon/carbon (C/C) composites in air at high temperatures, a SiC–MoSi₂/ZrO₂–MoSi₂ coating was prepared on the surface of C/C composites by pack cementation and slurry method. The microstructures and phase compositions of the coated C/C composites were analyzed by scanning electron microscopy and X-ray diffraction, respectively. The result shows that the SiC–MoSi₂/ZrO₂–MoSi₂ coating is dense and crack-free with a thickness of 250–300 μm. The preparation and the high temperature oxidation property of the coated composites were investigated. The as-received coating has excellent oxidation protection ability and can protect C/C composites from oxidation for 260 h at 1773 K in air. The excellent anti-oxidation performance of the coating is considered to come from the formation of ZrSiO₄, which improves the stability of the coating at high temperatures.     

ZrB2-MoSi2/SiC涂层C/C复合材料的制备及氧化性能（英文）

为了提高C/C复合材料的抗氧化性,在C/C复合材料基体上制备了ZrB2-MoSi2/SiC涂层。采用包埋法制备SiC中间层,采用喷涂法制备ZrB2-MoSi2外涂层。用XRD和SEM分别分析、测试所制备涂层的物相组成和显微结构,研究涂层复合材料的高温抗氧化性能。结果表明:C/C复合材料的外涂层由ZrB2、MoSi2和SiC三相组成;在1273K和1773K下分别氧化30h和10h后ZrB2-MoSi2/SiC涂层试样的质量损失分别为5.3%和3.0%,涂层表面长有纳米SiC晶须。C/C复合材料ZrB2-MoSi2/SiC涂层具有自愈合特性和良好的高温抗氧化性能。     

ZrO2–SiO2 gradient multilayer oxidation protective coating for SiC coated carbon/carbon composites

In order to eliminate the mismatch of thermal expansion coefficient between the ZrO₂ outer layer and the internal bonding SiC layer, ZrO₂–SiO₂ composition-gradient transition layers were prepared by a sol–gel technique using tetraethoxysilane (TEOS) and zirconyl chloride as source materials. Energy dispersive spectroscopy (EDS) analysis displays that the gradient composition ZrO₂–SiO₂ outer coating could be obtained by immersing the SiC precoated carbon/carbon (C/C) composites into the gradient composition zirconia-silica sols (ZS sol) in turn. Oxidation test shows that, after 10 h oxidation in air at 1773 K, the weight loss of the gradient ZrO₂–SiO₂ coating coated SiC-C/C is only 1.97%.     

多孔C泡沫预制体液相渗硅制备C/SiC复合材料研究

以多孔C泡沫为预制体,利用液相渗Si工艺制备了C/SiC复合材料。采用酚醛树脂浸渍-裂解工艺对C泡沫预制体的孔隙率进行调整,考察浸渍-裂解周期对C泡沫预制体孔隙率的影响,研究了C泡沫预制体孔隙率对C/SiC复合材料密度、力学性能、组成和结构的影响。结果表明:预制体孔隙率为72%时制备的C/SiC复合材料性能较好,其密度为2.58g/cm3、弹性模量为81.39GPa,抗弯曲强度为83.88MPa;随着预制体孔隙率的降低,复合材料的密度、弹性模量和抗弯曲强度不断降低,预制体孔隙率的降低影响液相Si充分扩散与C反应,造成复合材料内部存在大量闭孔,这是导致C/SiC复合材料性能下降的主要原因。     

Oxidation behavior of oxidation protective coatings for C/C-SiC composites at 1 500℃

Porous carbon/carbon preforms were infiltrated with melted silicon to form C/C-SiC composites. Three-layer Si-Mo coating prepared by slurry painting and SiC/Si-Mo multilayer coating prepared by chemical vapor deposition(CVD) alternated with slurry painting were applied on C/C-SiC composites, respectively. The oxidation of three samples at 1 500 ℃ was compared. The results show that the C/C-SiC substrate is distorted quickly. Three-layer Si-Mo coating is out of service soon due to the formation of many bubbles on surface. The mass loss of coated sample is 0.76% after 1 h oxidation. The sample with SiC/Si-Mo multilayer coating gains mass even after 105 h oxidation. SiC/Si-Mo multilayer coating can provide longtime protection for C/C-SiC composites and has excellent thermal shock resistance. This is attributed to the combination of dense SiC layer and porous Si-Mo layer. Dense SiC layer plays the dual role of physical and chemical barrier, and resists the oxidation of porous Si-Mo layer. Porous Si-Mo layer improves the thermal shock resistance of the coating.