单向碳／碳复合材料蠕变后的组织分析

用Ｘ射线衍射，激光喇曼光谱，ＳＥＭ和ＴＥＭ对一种单向碳／碳复合材料蠕变后的显微组织和界面作了分析。该材料用Ｔ３００碳纤维增强，用ＣＶＤ法沉积热解碳致密。结果表明，这种票经蠕变后，石墨化程度增加；碳纤维和基本碳的微晶尺寸也都有所增加，这些微晶沿纤维轴向择优取向；部分界面处有脱粘现象。     

液相气化法制备碳/碳复合材料工艺研究

探索了一种快速制备碳 /碳复合材料的新工艺——液相气化 CVI法。该工艺在沉积温度 80 0～ 14 0 0℃内 ,沉积时间 3h,多孔材料表观密度可达到 1.6 8g/ cm3,致密化速率达到 1.4～ 1.7mm/ h,致密化效率比报道的常规等温 CVI工艺要快 2个数量级以上。本文根据多孔介质传质传热学理论初步分析了该工艺快速致密的根本原因 ,采用偏光显微镜及扫描电镜观察了材料的微观组织结构及热解碳的生长特征 ,并测定了材料的表观密度及力学性能     

碳/碳复合材料抗烧蚀涂层工艺与性能研究

采用等离子喷涂方法在碳/碳复合材料上制备了钨/碳化钛复合涂层并进行了涂层抗烧蚀性能研究.结果表明：碳/碳复合材料表面等离子喷涂制备碳化钛涂层时,喷涂工艺参数中净能量是影响涂层组织致密性的主要因素,净能量为15～16 kW时涂层较为致密.碳化钛涂层具有较好的热化学稳定性,烧蚀后没有明显的氧化现象.碳化钛涂层高温烧蚀以机械剥蚀为主,高温、高速的焰流气动力是产生这一现象的主要原因.焰流中加入Al2O3颗粒烧蚀后,机械剥蚀加剧并有裂纹产生.     

催化FBCVI制备碳纳米纤维增强碳/碳复合材料的组织与力学性能研究

采用薄膜沸腾气相沉积(film-boiling chemical vapor infiltration,FBCVI)工艺,制备原位碳纳米纤维增强碳/碳复合材料(carbon nanofibers-reinforced carbon/carbon composites,CNFs-C/C))。研究了致密化过程中CNFs的生长情况和催化剂的引入对材料组织结构和力学性能的影响。研究表明,致密化前期,原位生长CNFs困难;随着沉积时间延长,CNFs大量增多并被碳基体包覆,CNFs主要为碳纳米线(carbon nanowires,CNWs)。CNFs-C/C的碳基体结构为粗糙层(RL),且存在大量的生长锥。相比于未加催化剂的试样,CNFs-C/C的弯曲强度和模量分别提高了30.9%和39.1%,断裂模式为假塑性断裂。     

碳／铜复合材料研究进展

简要回顾了碳／铜复合材料的发展过程,综述了在基体合金化,碳增强的表面处理、制备工艺,性能及应用等方面的研究进展。     

粉末粒度对碳/碳基体上羟基磷灰石涂层的影响

采用等离子喷涂技术在碳纤维增强碳复合材料(简称碳／碳复合材料)上制备了羟基磷灰石涂层,研究了原始粉末粒度对涂层的表面形貌、剪切强度、相组成等方面的影响,并分析了涂层与基体的界面结合状况。结果表明：采用粗粉末喷涂后得到的涂层结合强度较高．结晶程度也较高,但涂层与基体的结合机制仍为机械嵌合。     

沥青基碳/碳复合材料常压浸渍-碳化工艺及组织

对常压下液相浸渍 -碳化法制备沥青基 /碳复合材料工艺及致密规律进行了研究 ,并对所得制件的基体组织结构进行分析 ,从理论上解释其产生的原因 ,为制定工艺规范提供根据和指导     

送粉方式对碳/碳基体上等离子喷涂羟基磷灰石涂层的影响

采用等离子喷涂技术在碳／碳复合材料上制备了羟基磷灰石(HA)涂层，采用扫描电镜、X射线衍射仪、电子探针和电子拉伸机等研究了送粉方式对HA涂层的组织与性能的影响。结果表明：内送粉方式下制得的HA涂层，颗粒熔化程度较高，涂层的晶相含量较低；40kW的喷涂功率和外送粉方式下制得的HA涂层与碳／碳基体的抗剪强度最高；但HA涂层与碳／碳基体之间仍属于机械结合。     

密度梯度碳/碳复合材料的制备及性能

采用强制流动热梯度化学气相渗透法在1000～1 250℃制备了密度梯度碳/碳复合材料;借助三点弯曲试验和激光闪烁法测定了复合材料的弯曲性能与导热系数,用偏光显微镜及扫描电子显微镜观察了基体热解碳的组织结构及断口形貌。结果表明:该复合材料上层的最大密度为1.65g·cm~(-3),下层的最小密度为1.10g·cm~(-3),具有明显的密度梯度;复合材料的密度越大,抗弯强度越高;其导热系数也随密度的增加而增大;沉积温度是影响基体热解碳组织的主要因素,高温有利于粗糙层热解碳的生成,而低温有利于光滑层热解碳的生成。     

单向C／C复合材料第一阶段蠕变与松弛

用均热化学气相渗透法制备了一种单向碳／碳复合材料。在保护气氛下测定了不同温度应力下的第一阶段蠕变行为。结果表明，第一阶段蠕变符合关系工ε０＝ａｌｇｔ＋ｂ。由同一温度下不同应力的蠕变曲线簇获得先进地蠕变图，进而绘制出第和阶段松弛曲线，用σ＝σｔ＾－ｍ可较好地描述该松弛曲线。     

预制体添加BN对炭/炭复合材料性能的影响

在炭纤维预制体中添加六方氮化硼(h-BN),采用等温化学气相渗透(CVI)和超高压沥青浸渍/碳化混合工艺制备了炭/炭(C/C)复合材料。研究了材料的组织结构和力学性能,采用XD-MSM定转速摩擦试验机对材料的摩擦磨损性能进行了测试;分析了h-BN含量对摩擦磨损性能的影响。实验表明:预制体添加h-BN可以明显降低材料的摩擦系数,稳定材料的摩擦磨损性能。其中以9wt%时,材料的摩擦磨损性能最佳。     

The Solid Particle Erosion Behavior of Carbon/Carbon and Carbon/Phenolic Composite Used in Re-entry Vehicles

Several engineering components made of carbon-based heat-resistant composites are subjected to severe erosive wear. In view of the above, the solid particle erosion behavior of two and four dimensionally reinforced carbon/carbon (C/C) composites as well as that of carbon/phenolic (C/P) composite has been characterized at the ambient temperature. The investigated C/C composites have been produced through a liquid-phase infiltration method followed by hot isostatic pressing, while the C/P composite prepegs have been cured inside an autoclave. The erosion rates of these composites have been determined for two different impact angles and two different impact velocities using silica sand with average particle diameter of 200 μm. The morphologies of as-received and eroded surfaces of test specimens have been examined with the help of scanning electron microscopy to understand the mechanism of material removal. The erosion response, erosion efficiency, and erosion micromechanisms of these composites have been studied in detail. While the erosion resistance of the C/P composite is found to be superior to that of the investigated C/C composites, the four dimensionally reinforced C/C composite have shown the highest erosion efficiency. All the composites have exhibited a semi-ductile erosion response. Their mechanical properties have little correlation with the erosion rates.     

CSCVI法快速制备C纤维增韧SiC基复合材料及其微观结构

采用一种改进的 CVI工艺 (CSCVI法 )制备连续炭纤维增韧 Si C基复合材料 ,使预制体的编织与 Si C基体的沉积同步复合进行。在不同的工艺条件下 ,制备了 C/Si C复合材料 ,观察了其微观结构。结果表明 :CSCVI- C/Si C中的残留孔隙很小且明显小于 ICVI- C/Si C中的残留孔隙 ;CSCVI具有快速制备孔隙率低、体积密度较高的 C/Si C复合材料的能力 ;纤维束缠绕转轴的线速度直接影响到 C/Si C的显气孔率、纤维束间 Si C基体墙的厚度和 C/Si C复合材料的最终体积密度。     

Effect of Resin-Derived Carbon on the Friction Behavior of Carbon/Carbon Composites

Three different C/C composites with rough laminar (RL) pyrocarbon, RL pyrocarbon with added resin-derived carbon, and pure resin-derived carbon have been evaluated and tested for friction performance. A laboratory dynamometer was used to simulate different braking speeds utilizing a single stator and rotor pair. The morphologies and microstructures of the raw materials, wear surfaces, and wear debris at different braking levels were observed by polarized light microscopy, scanning electron microscopy, and transmission electron microscopy. The results have shown that the friction coefficients of the three C/C composites display the same characteristics with increasing braking speed. They increased to a maximum value at medium braking speed and thereafter decreased with increasing braking speed, and their mean values under the same braking conditions were similar. The C/C composite with pure resin-derived carbon showed the highest loss due to wear under all conditions, while the C/C composite with the RL pyrocarbon showed the lowest loss. Resin-derived carbon in C/C composites does not have a significant effect on the friction coefficient, but the wear rate increases greatly with increasing resin-derived carbon content. Wear debris is composed of flocculent particles with polycrystalline structure, along with the matrix carbon, which is worn off directly from the composites.     

炭黑/双马来酰亚胺复合材料的性能研究

采用浇铸成型法制备了炭黑填充双马来酰亚胺(BM I-BA)复合材料,研究了炭黑的填充量对复合材料力学性能和摩擦学性能的影响。在M-200型磨损机上测试该复合材料的摩擦学性能,利用扫描电镜(SEM)观察了摩擦副的表面形貌。结果表明:炭黑能够有效提高复合材料的力学性能和摩擦学性能。当炭黑的添加量为4.0wt%时,复合材料的综合力学性能最好;当炭黑的的添加量为6.0wt%时,复合材料的耐磨性能最好。SEM显示复合材料主要是粘着磨损,能在对磨环上形成薄而连续均匀的转移膜,而BM-BA树脂主要发生的是疲劳磨损,并伴有塑性变形。     

聚丙烯、炭黑和碳纤维共混填充超高分子量聚乙烯复合材料的力学和摩擦磨损性能

采用模压成型的方式制备超高分子量聚乙烯(UHMWPE)复合材料,通过AG-1型电子万能实验机和MM-200型摩擦磨损试验机分别研究填料对复合材料力学性能和摩擦磨损性能的影响,采用光学显微镜分析复合材料磨损表面的形貌。结果表明:聚丙烯(PP)和无机填料炭黑(CB)或CB与碳纤维(CF)混杂填料的加入使UHMWPE复合材料的拉伸强度降低,弯曲模量和硬度增加,其中UHMWPE/PP/CB/CF复合材料的弯曲模量和硬度增幅大于UHM-WPE/PP/CB复合材料。填料的加入可改善UHMWPE复合材料的摩擦磨损性能,当填料的质量分数为5%时,UHMWPE复合材料的摩擦磨损性能最好,且UHMWPE/PP/CB/CF复合材料的耐磨性能优于UHMWPE/PP/CB复合材料。与UHM-WPE相比,UHMWPE/PP/CB/CF复合材料的摩擦因数和磨痕宽度分别下降了10%和44%,UHMWPE/PP/CB复合材料则分别下降了12%和42%。光学显微镜观察表明填料的加入大大改善了UHMWPE的磨粒磨损,复合材料表面以较浅的犁沟磨损为主要特征。     

碳碳复合材料界面热力学研究

化工材料是化工业及工业生产制造的基本元素,各种材料的性能特点决定了复合产品加工制造质量的好坏。分析碳碳复合材料界面热力学特点,主要是为了保证化工材料性能的正常发挥,使得化工生产的流程更加顺利。采用了理论研究与生产实践相结合的方式分析了碳碳复合材料的基本性质与优势,从四大热力学定律分析了材料详细的热学特点,得出了温度高低变化是影响复合材料性能的重要因素。     

Impact Abrasive Wear Response of Carbon/Carbon Composites at Elevated Temperatures

Three types of carbon/carbon composites were fabricated using pitch as matrix material. Performance of these composites was evaluated under continuous impact abrasion tests (CIAT). Towards this purpose, a novel testing equipment was designed and developed at AC²T. Tests were carried out at room temperature and 500 °C. The angle of impact was chosen to be 45° and 90°. Analysis of tribological performance was carried out by mass loss. Characterization of the worn surface was done by means of scanning electron microscopy (SEM) and optical 3D profilometry. In this work, it was shown that wear rates are higher for 45° impact angle compared to 90° for all composites investigated. Fibre debonding and fibre pull out was observed to be the dominating wear mechanisms for these composites during CIAT procedure under normal impact abrasion. Removal of chunk of material contributes to wear under oblique impact abrasion.     

Friction and Wear Properties of 3D Carbon/Silicon Carbide Composites Prepared by Liquid Silicon Infiltration

Carbon/silicon carbide (C/SiC) composites were prepared by a liquid silicon infiltration (LSI) process and their microstructure and friction and wear properties studied. The matrices of the C/C green bodies were found to be reinforced with dense carbon fiber bundles hanging together. The density of the composites before and after the LSI process was 1.25 and 1.94 g/cm³, respectively. However, the open porosity of C/SiC composites was about 16% due to the opening of closed pores during the machining process. The C/SiC composites exhibited excellent tribological properties in the dry condition, with an average coefficient of friction (COF) and wear rate of about 0.29 and 16.15 μg/m MPa, respectively. In comparison, the average COF was about 0.13 in the moist condition, with a wear rate of 5.87 μg/m MPa. The main wear mechanism of the C/SiC composites was worn particles and debris with a high degree of hardness, producing a plough effect on the friction surface in the dry condition and an adhesive effect in the moist condition.     

碳纳米管/环氧树脂复合材料研究

将碳纳米管加入到环氧树脂中，经超声分散处理制得复合材料。研究了碳纳米管的加入量与分散程度对材料抗拉强度的影响。研究表明：碳纳米管的加入量小于3％时可有效提高复合材料的抗拉强度，加入量为1．7％，抗拉强度达到最高值52．38MPa，比纯环氧树脂(26．40MPa)提高98．4％。