感应烧结石墨/铜铁基高温自润滑复合材料摩擦学性能研究

通过基体合金化和添加不同含量的石墨,采用感应加热烧结的方法制备了石墨/铜铁基高温自润滑复合材料,在力学性能试验机和MRH-3摩擦磨损试验机上考察了复合材料从室温～500℃温度条件下的力学和摩擦磨损性能,利用扫描电镜观察分析了磨损表面形貌,进而探讨了摩擦磨损机理。结果表明,复合材料的力学和摩擦磨损性能与感应加热频率和石墨含量有关;在室温条件下,随着石墨含量的升高复合材料的力学性能变差而减磨自润滑效果变好,在室温～500℃条件下,选用合适的感应加热频率和石墨的含量可以使石墨/铜铁基自润滑材料保持良好的耐磨性;而复合材料的磨损机制由粘着磨损变为犁沟磨损。     

电铸制备铜-石墨复合材料的研究

在酸性硫酸铜溶液中采用电铸技术制备了铜-石墨复合材料.表面活性剂、微粒浓度、电流密度和搅拌速度等工艺条件对微粒含量具有不同的影响.非离子表面活性剂对微粒共沉积具有较好的效果;随着微粒浓度增大,微粒含量也逐渐增大,最后趋于稳定值;电流密度增大使微粒含量降低;搅拌速度增大时微粒含量存在最大值.铜-石墨复合材料的硬度和摩擦系数随着微粒含量增大而减小,但是磨损量先是减小而后增大.摩擦过程中纯铜发生粘着磨损,铜-石墨复合材料却表现为剥层磨损.     

铜石墨复合材料改性研究进展

综述了铜石墨复合材料在改性方面进行的界面、添加剂和纤维增强等方面的研究.研究认为,界面改性、添加剂及纤维特别是纳米碳管等能显著提高铜石墨复合材料导电性能及摩擦磨损性能.     

石墨含量对铜-石墨-乳化沥青复合材料组织和性能的影响

以电解铜粉与石墨粉为原料,阴离子乳化沥青为粘结剂,采用粉末冶金技术制备了铜-石墨-乳化沥青复合材料,并通过XRD、EDS和SEM对石墨含量为2wt%~8wt%的铜-石墨-乳化沥青复合材料微观组织进行表征,研究了铜-石墨-乳化沥青复合材料的摩擦磨损性能、力学和电学性能,并与不含乳化沥青的铜-石墨复合材料进行比较。结果表明,乳化沥青可以有效防止石墨颗粒的聚集,对石墨和铜基体起粘结作用;在两相界面处几乎没有间隙,并且产生了层片状石墨;石墨含量为4wt%的试样磨损量最小,仅为0.0049 g,摩擦系数约为0.025;增加载荷和石墨含量会增大磨损量,但会降低摩擦系数;在滑动摩擦期间,磨损表面会出现裂纹、犁沟、凹陷、小颗粒和层片状结构,但其程度要比不含乳化沥青的复合材料低。      

热压烧结制备SiC增强石墨复合材料及其性能

以天然鳞片石墨为起始原料,SiC颗粒为增强相,采用热压烧结工艺制备了SiC增强石墨复合材料。研究了SiC含量对SiC增强石墨复合材料微观结构、力学性能和摩擦性能的影响。结果表明:SiC颗粒均匀分布在石墨基体中,降低了基体中的孔隙率;随着SiC含量增加,SiC增强石墨复合材料的相对密度和弯曲强度相应增加,开孔率显著降低,当SiC含量达到40vol%时,SiC增强石墨复合材料中形成了SiC网络骨架结构,相对密度达到了94.2%,比商品高强纯石墨材料提高了11.8%,弯曲强度达到了146 MPa,比商品高强纯石墨材料提高了147%;基体石墨保持了层状结构;SiC含量低于40vol%时,SiC增强石墨复合材料的摩擦系数随SiC含量的增加轻微增加,与纯石墨材料的摩擦系数相当,具有良好的摩擦性能。     

感应烧结Fe-Cu-Al-石墨复合材料的力学性能和摩擦学性能

为了进一步提高材料的力学性能和摩擦学性能,以感应加热烧结的方法,制备了Fe-Cu-Al-石墨复合材料。利用XRD,EDS,SEM等分析了复合材料的组成、结构、表面形貌;研究了其力学性能、摩擦学性能及磨损机理。结果表明：Fe-Cu-A1-石墨复合材料具有多孔结构;随着石墨含量的增加,复合材料的力学性能降低,摩擦学性能提高...     

泡沫铝相对密度对泡沫铝-聚氨酯复合材料吸能性能的影响

目的通过准静态压缩试验研究泡沫铝-聚氨酯复合材料(AF-PU)的压缩性能,并利用试验数据探究泡沫铝(AF)相对密度对整体材料吸能性能的影响规律。方法首先使用相关仪器和材料制备AF-PU复合材料,其次用相关仪器对其进行准静态压缩试验。结果 AF-PU复合材料通过相关仪器进行准静态压缩试验,计算得到相对应的应力-应变曲线,同时通过计算得到相对应的吸能-应变曲线。当泡沫铝相对密度从5.6%增加到6.7%时,整体复合材料的屈服强度提升了22.18%。在压缩过程中,当复合材料的压缩应变为0.8时,整体复合材料的总吸能增加了70.08%。结论 AF-PU复合材料的吸能性能随着AF相对密度的增加而增强。     

铜-石墨自润滑触头材料的研究进展

综述了铜-石墨滑动触头材料的研究进展,包括制备工艺、石墨含量、石墨粒度、添加组分和化学镀铜包覆石墨因素对铜石墨材料性能的影响以及铜石墨材料的摩擦学问题,最后指出了铜石墨自润滑触头材料的发展趋势.     

一种新的自润滑铜-石墨-NbSe2复合材料的合成及摩擦性能研究

研究了NbSe2的添加对铜-石墨固体自润滑材料的影响,采用粉末冶金法将制备的不同质量百分比含量的纤维状或片层状的纳米NbSe2材料与铜粉、石墨粉混合均匀,冷压制成小圆盘.采用光学显微镜,SEM(JSM-7001F扫描电子显微镜)等手段表征表面形貌.并在超低温摩擦磨损机和UMT-2摩擦试验仪上测试其摩擦性能.实验结果表明...     

碳纤维不同分布的碳纤维-铜复合材料的电导率

将碳纤维按不同方式分布与铜粉混合热压, 制取复合材料, 测定了碳纤维含量与分布方式对复合材料电导率的影响。给出了测定结果, 为复合材料的结构设计提供了一定的依据。      

放电等离子烧结制备Diamond/Al复合材料

采用放电等离子烧结法（SPS）制备了Diamond/Al复合材料,研究了金刚石粒径、成分配比、工艺参数等对复合材料的导热性能的影响。结果表明,SPS可以得到导热性能较好的Diamond/Al复合材料,致密度是影响该材料导热性能的最重要因素。在实验确定的金刚石体积分数50%,金刚石粒径70 μm,温度550℃、压力30 MPa的工艺条件下,所制备的材料致密度较高,热导率为182 W/(m·K),比相同条件下纯铝粉烧结体的热导率提高了34.8%,表明金刚石的添加对烧结铝基材料导热性能有明显的改善作用。      

Microstructure and mechanical properties of CNT/Ag nanocomposites fabricated by spark plasma sintering

Carbon nanotube/silver (CNT/Ag) nanocomposites include CNT volume fraction up to 10?vol.% were prepared by chemical reduction in solution followed by spark plasma sintering. Multiwalled CNTs underwent surface modifications by acid treatments, the Fourier transform infrared spectroscopy data indicated several functional groups loaded on the CNT surface by acid functionalisation. The acid-treated CNTs were sensitised and activated. Silver was deposited on the surface of the activated CNTs by chemical reduction of alkaline silver nitrate solution at room temperature. The microstructures of the prepared CNT/Ag nanocomposite powders were investigated by high-resolution scanning electron microscopy (HRSEM), transmission electron microscopy and X-ray powder diffraction analysis. The results indicated that the produced CNT/Ag nanocomposite powders have coated type morphology. The produced CNT/Ag nanocomposite powders were sintered by spark plasma sintering. It was observed from the microstructure investigations of the sintered materials by HRSEM that the CNTs were distributed in the silver matrix with good homogeneity. The hardness and the tensile properties of the produced CNT/Ag nanocomposites were measured. By increasing the volume fraction of CNTs in the silver matrix, the hardness values increased but the elongation values of the prepared CNT/Ag nanocomposites decreased. In addition, the tensile strength was increased by increasing the CNTs volume fraction up to 7.5?vol.%, but the sample composed of 10?vol.% CNT/Ag was fractured before yielding.     

Processing of alumina-based composites via conventional sintering and their characterization

The present work relates to the processing of dense alumina-based composites, their microstructural characterization and study of mechanical properties. Alumina ceramic material and alumina-based composites with m-Zirconia and Ceria addition are sintered at 1600°C, 1650°C and 1700°C temperatures via conventional sintering. Solid-state diffusion during sintering led to volume diffusion in alumina, and volume and grain boundary diffusion in alumina composite. In the present sintering conditions alumina is found to be the least dense as improper solid-state diffusion resulted in porosity, whereas alumina–zirconia composite achieved the highest density of 97%. Scanning electron microscope (SEM) micrograph shows homogeneous distribution of fine zirconia particles inside the alumina matrix, filling the voids of the alumina skeletal structure. Zirconia connects to alumina particles, restricting its abnormal grain growth. It results in strong bonding and grain refinement. Alumina–zirconia composite exhibits the highest hardness and fracture toughness of 14.37?GPa and 4.6?MPa?·?m^1/2 at 1700°C. Alumina suppresses the transformation of m-t zirconia, resulting in high toughness of alumina composites. Alumina–zirconia–ceria composite revealed the presence of porosity, which led to less densification and low mechanical properties.     

烧结气氛对Ni-Fe尖晶石陶瓷致密化和导电性能的研究

制备了不同气氛下烧结的NiFe2O4陶瓷材料,研究了烧结气氛和烧结温度对NiFe2O4。陶瓷物相组成、致密度、导电率和显微组织的影响。结果表明：NiFe2O4在N2气氛下烧结时,晶格发生部分畸变,但物相组成不发生改变;与空气条件下烧结过程相比,N2气氛在保证材料获得较高的致密度和导电率的同时,有效降低了烧结温度。NiFe2O4陶瓷在N2气氛中1250℃烧结时,致密度为93．20％,960℃下的导电率20．83S／cm,气孔率为6．80％,平均晶粒粒径为4～5μm。     

热压烧结一步法制备C_f/Cu复合材料的组织和性能

为了简化工艺及提高性能,采用热压烧结一步法制备Cf/Cu复合材料。研究了Cf/Cu复合材料的界面反应原理、微观形貌及不同的Ti添加量对复合材料密度、硬度、强度等性能的影响。结果表明:Cu-C-Ti三元体系,在低于1100℃,碳纤维表面生成TiC层,该反应层降低了液态Cu与碳纤维的润湿角,改善了Cu与碳纤维的界面结合。探讨了TiC层的形成机制,提出了溶解在Cu液中的Ti原子与碳纤维接触生成TiC的微观反应模型。TiC层的形成有利于提高复合材料的性能。当Ti的质量分数为16.7%时,Cf/Cu复合材料的综合性能最好,其肖氏硬度高达HS66.94,抗弯强度为97.59 MPa。     

The dynamic properties of SiCp/Al composites fabricated by spark plasma sintering with powders prepared by mechanical alloying process

The dynamic compressive properties of SiC particle reinforced pure Al matrix composites, fabricated by spark plasma sintering technique with mixture powders prepared by mechanical alloying process, were tested in this paper. Two different average SiC particle sizes of 12 μm and 45 μm were adopted, and the compressive tests of these composites at strain rates ranging from 800/s to 5200/s were conducted by split Hopkinson pressure bar. The damage mechanism of the SiC_p/Al composites was analyzed through the microstructural observations and high-precision density measurements. Results show that the dynamic properties and damage accumulation of these composites are significantly affected by the particle distribution, size, particle cracking, particle/matrix interface debonding and adiabatic heat softening. The composites containing smaller SiC particles exhibit higher flow stress, lower strain rate sensitivity, and less damage at high strain rate deformation.     

On the thermal conductivity of bimodal SiC/A356 composites fabricated via powder metallurgy route

The present study investigates the thermal conductivity of bimodal SiC particulate distribution in aluminum matrix composites fabricated via powder metallurgy route. The effects of the SiC_p reinforcement size distribution and processing parameters such as sintering time and temperature on the thermal conductivity have been examined. The Box–Behnken experimental array was employed to identify the effects of selected variables on the thermal conductivity of the composite. A reasonable augmentation in the thermal conductivity was observed with an increase in sintering time and %volume fraction of fine SiC particulates. It has been demonstrated that the matrix doped with fine SiC particulates (37?µm) occupied interstitial positions and formed continuous SiC–matrix network resulting in minimizing the micropores that contributed for good thermal conductivity, that is, 235?W/mK. Scanning electron microscopy (SEM) and x-ray diffraction (XRD) were conducted to evaluate the microstructure architecture and interfacial phase formation.     

Thermophysical properties of porous SiC ceramics fabricated by pressureless sintering

Highly porous SiC with approximately 30–41% porosity was fabricated by pressureless sintering without sintering additives at temperatures in the range 1700–2000 °C. Thermal diffusivities, specific heats, thermal conductivities and thermal resistivities of sintered samples are reported for temperatures from room temperature to 1000 °C. The thermal diffusivities and thermal conductivities of all samples decreased significantly with increasing temperature over this range, whereas specific heats and thermal resistivities increased. At any given temperature, the greater the porosity of the SiC, the lower the thermal conductivity.     

Thermophysical properties of porous SiC ceramics fabricated by pressureless sintering

Highly porous SiC with approximately 30–41% porosity was fabricated by pressureless sintering without sintering additives at temperatures in the range 1700–2000 °C. Thermal diffusivities, specific heats, thermal conductivities and thermal resistivities of sintered samples are reported for temperatures from room temperature to 1000 °C. The thermal diffusivities and thermal conductivities of all samples decreased significantly with increasing temperature over this range, whereas specific heats and thermal resistivities increased. At any given temperature, the greater the porosity of the SiC, the lower the thermal conductivity.