共查询到19条相似文献,搜索用时 203 毫秒
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以碳毡为预制体,N2为稀释气体,甲烷为碳源前驱体,其分压为10 kPa,滞留时间为0.15 s的工艺条件下,研究了不同沉积温度对微波热解化学气相渗透(chemical vapor infiltration,CVI)工艺制备碳/碳复合材料的致密化速率、样品的体积密度及其密度均匀性的影响,并对其组织结构进行了观察.分析了沉积温度对微波热解CVI工艺制备碳/碳复合材料的密度与组织结构的变化规律.结果表明:在微波热解CVI工艺中,随着沉积温度的降低,碳毡预制体的致密化速率及最终体积密度呈现先升后降,1100 ℃沉积制备复合材料的密度均匀性最好,并呈现从内到外逐步沉积的规律.热解碳的织构主要为中等织构. 相似文献
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化学气相渗透(CVI)工艺被广泛应用于制备碳基及碳化硅(SiC)基复合材料,CVI工艺是实现制备高纯度和高晶粒度SiC基体的SiCf/SiC复合材料最佳方案。为了优化CVI制备SiC基体的工艺参数,本文主要研究了CVI工艺沉积SiC的动力学机理及数值模拟。对于CVI工艺SiC沉积的动力学,本文提出了SiC沉积过程的反应动力学机理模型,并通过耦合反应器内的流场和浓度场,模拟了甲基三氯硅烷(MTS)在CVI过程中的SiC沉积实验。通过对样品在CVI致密化过程中孔隙率的实验结果与模拟结果比较,表明该SiC沉积动力学模型的合理性。通过模拟获得了在反应器内的速度场和各组分(MTS, CH3,SiCl3)的浓度场分布情况,以及预制体致密化过程的密度分布情况。以上SiC的CVI工艺动力学模拟,对未来优化SiCf/SiC复合材料CVI工艺具有重要的指导意义。 相似文献
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本文综述了碳/碳复合材料力学性能的研究进展,包括碳纤维、基体炭、界面性能、制备工艺及工艺参数等对碳/碳复合材料力学性能的影响。同时简单介绍了当今单向碳/碳复合材料力学性能的表征手段。希望对碳/碳复合材料力学性能的研究及应用提供帮助。 相似文献
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石墨化处理对高压浸渍碳化碳/碳复合材料抗氧化性能的影响 总被引:1,自引:1,他引:0
用超高压液相浸渍和碳化,经石墨化处理制备了毡基碳/碳复合材料。采用等温氧化实验,系统研究了所得试样在不同温度(773~1 173 K)条件下的氧化动力学行为;用X射线衍射和扫描电子显微镜检验观察了石墨化处理前后毡基碳/碳复合材料的氧化形貌和微观结构。结果表明:石墨化处理可明显的提高毡基碳/碳复合材料的抗氧化性能;毡基碳/碳复合材料的基体在氧化反应中优先氧化,氧化反应速率随温度的升高而增大;在高于或低于临界温度973 K时,毡基碳/碳复合材料的氧化反应分别受2种不同的机制控制,其反应活化能E,在石墨化前分别为7.91×10~4 J/mol和2.80×10~4J/mol,石墨化后分别为1.08×10~5J/mol和4.42×10~4J/mol。 相似文献
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一、序言 碳/碳复合材料由于有良好的热物理和力学性能,因而在宇航方面的应用无与伦比。化学气相沉积的碳/碳复合材料性能变化复杂,影响因素也很多,但其最主要的要受材料内部沉积碳微结构的影响,而微结构又是由工艺参数所决定的。笔者以前报导了工艺部分,采用热梯度法,以碳毡为基,不同工艺参数得出不同沉积碳微结构,指出控 相似文献
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结构炭/炭复合材料力学性能及微观结构研究 总被引:13,自引:1,他引:13
采用四向编织、快速化学气相渗透致密化新工艺制备了炭/炭复合材料,其弯曲强度达320MPa。分析研究了这种材料的力学性能特征。利用SEM和高分辨TEM分析了基体炭、炭纤维/基体灰界面的精细结构,发现炭纤维呈单根被基体炭包围,基体现灰呈层片状,为二维有序的乱层石墨结构;在炭纤维与基体炭之间存在着过渡相,这一过渡相厚度的约几十纳米,随着与炭纤维之间距离的增大,它们之间形成的夹角由小变大,这一过渡相即为炭 相似文献
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生命周期评价法(LCA)是指用数学物理方法结合实验分析对某一过程、产品或事件的资源、能源消耗,以及废物排放、环境吸收和消化能力等环境负担性能进行评价,以定量确定该过程、产品或事件的环境合理性及环境负荷量大小的一种新型研究方法。输入/输出法是LCA中的一种重要方法,本研究利用该方法对炭/炭(C/C)复合材料两种制备工艺(等温和热梯度化学气相渗透)中的资源、能源消耗以及污染物排放进行了定量评估。结果表明,与热梯度工艺相比,等温化学气相渗透法消耗了更多的资源、能源,给环境造成了严重的负荷,等温化学气相渗透法需改进,热梯度化学气相渗透工艺有广阔的应用前景。 相似文献
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新型炭纤维/泡沫炭预制体的制备及致密化研究 总被引:1,自引:0,他引:1
由炭纤维/酚醛树脂经过发泡、固化和炭化制备出4种不同炭纤维含量(3%,7%,10%和15%)的泡沫炭作为制备炭/炭复合材料新型预制体,通过等温化学气相沉积对预制体进行致密化处理。研究了炭纤维含量对预制体微观结构、致密化过程及力学性能的影响。结果表明:炭纤维含量增加,使预制体产生更多的微裂纹,并有更多的炭纤维裸露在泡沫炭韧带外,有助于提高化学气相沉积的沉积速率。炭纤维/泡沫炭预制体炭/炭复合材料压缩强度随着预制体中炭纤维含量的增加而增加,当炭纤维体积分数为10%时,压缩强度达到峰值,为43MPa。 相似文献
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The oxidation kinetics of carbon/carbon (C/C) composites prepared using a rapid directional diffused (RDD) CVI process were studied. The results showed that the Arrhenius curve for the RDD CVI C/C composites consists of two straight lines, the intercept of which is at about 700 °C at the linear oxidation stage. The oxidation rates are controlled by the surface reaction at 600-700 °C, and the corresponding activation energy is 121 kJ/mol. Between 700 and 800 °C, the oxidation rates are dominated by chemical reaction and diffusion, and the relevant activation energy is 80 kJ/mol. SEM investigation showed that the oxidation starts with original pores on the C/C composite surface with the carbon fiber and matrix oxidized simultaneously. An inexpensive and easily pasted coating containing epoxy organic silicon resin, borates, refractory particulates, etc. was developed. After isothermal temperature, thermal cycle and immersion water oxidation tests, the coating was demonstrated to exhibit good oxidation-resistance properties. The oxidation-resistant mechanism of the coating is discussed. 相似文献
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Ruiying Luo 《Carbon》2002,40(8):1279-1285
A technology used to prepare C/C composites using a rapid directional diffused (RDD) chemical vapor infiltration process has been investigated. General RDD technologies were explored, and optimal parameters were determined. The friction and wear properties of this material were researched. The results showed that in the RDD process, propylene and nitrogen were rapidly and directionally diffused into the carbon preforms enabling carbon deposition to occur from the inside of the preform to the outside. This method prevents the formation of an outer crust on the surface of preforms and facilitates uniformity of densification. With the RDD process no surface machining was required between chemical vapor infiltration (CVI) cycles thereby enabling continuous densification and reducing the CVI cycle times. The optimum processing conditions for RDD CVI were as follows; furnace temperature 950 °C; and furnace pressure 6.7 kPa. The C/C composites produced using RDD CVI processing exhibited good friction performance. Their curves of the brake moment with the velocity are stable under dry conditions, and their wet brake moment is greatly reduced. The average thickness wear is decreased to 9.5×10−4 mm/surface/stop. 相似文献
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In this paper carbon fiber reinforced carbon–boron nitride binary matrix composites (C/C–BN) were prepared by chemical vapor infiltration (CVI). The infiltration of BN in the CVI process was controlled by the diffusion of BCl3, and BN matrix was distributed homogeneously in the porous carbon fiber reinforced carbon matrix composites (C/C) due to the good infiltration ability of BN. The as-received C/C–BN composites were composed of 92 vol% C and 8 vol% BN. Both the friction coefficient and wear rate of C/C composites decreased significantly by the incorporation of BN. After heat-treated at 1600 °C, the interlayer spacing of CVI BN decreased to 3.36 Å, and CVI BN with high crystalline degree displayed the excellent lubricating effect, leading to the decrease of friction coefficient and wear rate. The improvement of the tribological properties also was partially attributed to the improved oxidation resistance and the formation of friction film by the incorporation of BN matrix. 相似文献
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C/C复合材料的高温抗氧化研究进展 总被引:20,自引:1,他引:20
以设计思路的发展演化为线索,结合国内外近年的研究报道,从选材的性能要求、组成、抗氧化机理、成功范例及制备工艺的角度出发,分别对抗氧化涂层技术以及抗氧化基体改性技术进行了介绍。特别选取了近年在碳/碳复合材料抗氧化研究中报道较少的制备技术进行详细介绍,其中包括涂层技术中的超临界态流体工艺、溶胶-凝胶法、熔浆法、PACVD法以及基体改性技术的快速致密化工艺。这一领域内的中外研究也进行了对比,并在文章最后提出了对于碳/碳复合材料高温氧化保护研究方向的一些看法。 相似文献
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Wen Yang Akira Kohyama Yutai Katoh Hiroshi Araki Jinnan Yu Tetsuji Noda 《Journal of the American Ceramic Society》2003,86(5):851-856
Several CVI-SiC/SiC composites were fabricated and the mechanical properties were investigated using unloading–reloading tensile tests. The composites were reinforced with a new Tyranno-SA fiber (2-D, plain-woven). Various carbon and SiC/C layers were deposited as fiber/matrix interlayers by the isothermal CVI process. The Tyranno-SA/SiC composites exhibited high proportional limit stress (∼120 MPa) and relatively small strain-to-failure. The tensile stress/strain curves exhibited features corresponding to strong interfacial shear and sliding resistance, and indicated failures of all the composites before matrix-cracking saturation was achieved. Fiber/matrix debonding and relatively short fiber pullouts were observed on the fracture surfaces. The ultimate tensile strength displayed an increasing trend with increasing carbon layer thickness up to 100 nm. Further improvement of the mechanical properties of Tyranno-SA/SiC composites is expected with more suitable interlayer structures. 相似文献