Carbon spheres prepared via solvent-thermal reaction method and their microstructures after high temperature treatment

Carbon spheres with size of 50–300 nm were synthesized via a solvent-thermal reaction with calcium carbide and chloroform as reactants in a sealed autoclave. The morphologies and microstructures of carbon spheres before and after high temperature treatment (HTT) were characterized by X-ray diffractometry (XRD), scanning electronic microscopy (SEM), energy diffraction spectroscopy (EDS), and transmission electron microscopy (TEM). The formation mechanism of carbon spheres was discussed. The results indicate that the carbon spheres convert to hollow polyhedron through HTT. Carbon spheres are composed of entangled and curve graphitic layers with short range order similar to cotton structure, and carbon polyhedron with dimension of 50–250 nm and shell thickness of 15–30 nm. The change of solid spheres to hollow polyhedron with branches gives a new evidence for formation mechanism of hollow carbon spheres.     

Wet friction performance of C/C-SiC composites prepared by new processing route

C/C-SiC composites with SiC island distribution were prepared via a new processing route. The fabrication process mainly included silicon infiltration by ultrasonic vibration, chemical vapor deposition (CVD), siliconizing, liquid phase impregnation and carbonization. The wear and friction properties were tested by an MM-1000 wet friction machine. The results show that SiC phases are mainly distributed between carbon fibers and pyrocarbons as well as among the pryocarbons. The dynamic friction coefficient of the composites decreases gradually from 0.126 to 0.088 with the increase of the surface pressure from 0.5 to 2.5 MPa at the same rotary speed. Furthermore, under the constant surface pressure, the dynamic friction coefficient increases from 0.114 to 0.126 with the increase of the rotary speed from 1 500 to 2 500 r/min. However, the coefficient decreases to 0.104 when the rotary speed exceeds 4 500 r/min. During the friction process, the friction coefficient of C/C-SiC composite is between 0.088 and 0.126, and the wear value is zero after 300 times brake testing. Foundation item: Project(2006CB600901) supported by the Major State Basic Research and Development Program of China; Project(0991015) supported by Guangxi Science Found, China; Project(200808MS083) supported by Guangxi Education Department Found     

金属陶瓷离合器片的研制开发

试验研究了金属陶瓷离合器片的压制工艺、烧结工艺 ,分析了各工艺参数对离合器片摩擦性能的影响 ,确定离合器片的最佳生产工艺为 :压制压力 2 4 5MPa ,烧结温度 ( 86 0± 1 0 )℃ ,烧结保温压力 1 .4 7～ 1 .96MPa ,烧结保温时间 3h。     

高能电子束辐射对硼酚醛树脂的影响

对硼酚醛树脂进行了高能电子束辐射,并进行了差热分析、热失重分析、残炭率和炭化后的粉末电阻率测试.结果表明硼酚醛树脂辐射前在100～200 ℃之间有一个明显的吸热反应峰,固化温度范围较大;而经过辐射后,100～300 ℃反应峰较少,硼酚醛树脂的固化温度范围明显减小,且固化温度降低.炭化后粉末电阻率由辐射前的3899.6 μΩ·m显著提高为辐射后的4951.6 μΩ·m;残炭率由60.6%降低为58.1%.     

模压成形制备高电阻率炭材料

利用浸渍炉内残留或废弃的呋喃树脂,采用温压成形技术制备高电阻率炭材料。研究了粘结剂质量分数对材料性能(密度、电阻率、石墨化度)的影响,用扫描电镜观察了材料断口的微观形貌。结果表明,采用30%的酚醛树脂做粘结剂时,材料的综合性能最优,其平均密度为1.47g.cm-3,电阻率为224μΩ.m;制品中加入粘结剂时,石墨化度明显增加,为37.5%;试样断口扫描电镜照片表明粘结剂的质量分数为30%时,材料致密,孔隙细小且分布均匀,没有明显裂纹。     

摩擦组元对粉末冶金摩擦材料摩擦性能的影响

实验研究了不同种类摩擦组元对粉末冶金摩擦材料摩擦磨损性能的影响。结果表明摩擦组元的显微硬度对摩擦因数和摩擦因数稳定度影响显著。随着摩擦组元显微硬度的提高，摩擦材料的耐磨性提高，而对偶材料的磨损量增大；摩擦材料的表观硬度主要取决于基体组元，摩擦组元的显微硬度对其影响不人。单独依靠一种摩擦组元不能使摩擦材料取得较佳的摩擦性能，综合使用几种摩擦组元，才能得到满意的效果。     

炭/炭复合材料湿式制动过程中的温度场模拟

摩擦过程中的温度场和热应力分布状况是摩擦学研究领域的一个重要课题.基于炭/炭复合材料制动盘湿式制动试验,将制动过程中的摩擦生热等效为瞬时移动面热源,按传动学理论计算制动盘与冷却润滑油的对流传热系数,建立三维循环对称有限元模型,运用有限元软件ANSYS分析制动盘的温度分布,给出典型时刻的温度场分布云图及温度升高引起的热应力场.利用有限元分析刹车制动过程的温度场,可为摩擦材料的研制及制动盘的设计提供有效的参考.     

热解炭的微观结构及其测试方法

主要介绍了利用正交偏光显微镜（PLM）、X射线衍射（XRD）、透射电镜（TEM）和喇曼光谱（RS）等测试方法,对采用化学气相沉积（CVD）法制备的C/C复合材料的热解炭的表面微观形貌、沉积炭层间距d002、微晶尺寸Lc及其石墨化度等参数进行表征和测量,从而判断沉积的热解炭的织构类型（光滑层、粗糙层和各向同性炭）,并且分析了上述各种测试手段的优缺点。     

粉末冶金摩擦材料的应用现状及对原材料的要求

粉末冶金技术在中国的应用获得快速发展。系统介绍了粉末冶金摩擦材料在飞机刹车、坦克制动、离合器片、风电制动器主轴、高速列车制动闸片等领域的国内外应用现状,并对粉末冶金摩擦材料的原材料提出了具体要求,以期对粉末冶金技术的进一步发展提供参考。     

添加ZrO2对铜基摩擦材料摩擦磨损性能的影响

采用粉末冶金方法制备了高速列车用铜基摩擦材料,研究了添加ZrO2的量对材料的摩擦因数、磨损量的影响规律。结果表明:在添加ZrO2的材料中,含5%(质量分数,下同)ZrO2的材料摩擦因数较高,磨损量也较大;添加8%ZrO2的材料在高速下的摩擦因数较高,磨损率较小且变化平稳。材料的磨损在较低的速度下以粘着磨损为主;随着速度的上升,磨损也逐渐变成以剥层脱落和氧化磨损的混合机制为主。