石墨表面镀铜对铁基粉末复合材料摩擦性能影响的研究

石墨与铜的界面结合及石墨在基体中的分布方式,是影响铁基粉末复合材料摩擦性能的重要因素。用镀铜石墨制备铁基粉末复合材料,并测定了材料的摩擦系数、磨损性能。结果表明石墨经镀铜处理后,使复合材料的摩擦系数有所降低,磨损性能提高20%～30%。     

镀铜石墨含量对Fe-25Cu基摩擦材料组织结构及摩擦性能的影响

目的 为改善石墨与铜铁基摩擦材料的结合方式,探究不同含量的镀铜石墨对铜铁基摩擦材料组织结构的影响,并研究加入不同含量的镀铜石墨时,摩擦材料的摩擦性能和摩擦机理。方法 采用热压烧结法制备Fe-25Cu基摩擦材料,利用扫描电镜、X射线衍射等表征手段进行表征,并利用摩擦磨损试验机测试摩擦材料的摩擦性能,分析摩擦因数。摩擦试验后的材料利用扫描电镜进行表面观测,分析摩擦磨损机理。计算材料摩擦后的磨损量,以此分析镀铜石墨含量对摩擦材料的影响。结果 相同转速下随着镀铜石墨含量的增加,平均摩擦因数降低,当镀铜石墨的质量分数为9%时,摩擦因数曲线最平稳;随着镀铜石墨含量的增加,摩擦因数逐渐降低,磨损率先减少后增加。当加入9%的镀铜石墨时,该材料的摩擦性能最好,此时材料的摩擦因数为0.436,磨损率最低为0.023 mm;黏着磨损和磨粒磨损是添加镀铜石墨的摩擦材料的主要摩擦机理。结论 在Fe-25Cu基摩擦材料中镀铜石墨与基体的结合情况优于石墨与基体的结合,同时加入镀铜石墨Fe-25Cu基摩擦材料的摩擦因数高,磨损量小。     

铜镀层对石墨-铜复合材料摩擦磨损性能的影响

通过在石墨表面镀铜预处理获得Cu包覆的石墨粉末,并以电解铜粉、鳞片石墨粉和Cu包覆石墨粉末为原料,利用ZT-40-20Y真空热压烧结炉制备了鳞片石墨-铜和镀铜石墨-铜复合材料,随后在不同载荷(5、7、9和11N)下对复合材料进行往复摩擦磨损试验,研究两种复合材料的微观结构、力学性能和不同载荷下的摩擦磨损性能.结果 表明:在相同的制备条件下,镀铜石墨有效地改善了镀铜石墨-铜复合材料中C、Cu之间润湿性的问题,使得其致密度、硬度显著提高;在相同的摩擦条件下,镀铜石墨-铜复合材料平均摩擦系数略有提高、而磨损率显著降低,表现出优良的耐摩擦磨损性能;在不同载荷下的往复摩擦试验中,鳞片石墨-铜复合材料主要磨损机制为磨粒磨损、剥落磨损和粘着磨损;而镀铜石墨-铜复合材料主要的磨损机制为磨粒磨损和少量剥落磨损.     

温度对铜基自润滑材料减摩耐磨特性的影响

采用常规的粉末冶金方法制备了铜基石墨固体自润滑复合材料, 通过基体合金化和改变石墨粒度探讨了复合材料的力学性能和在不同温度条件下的摩擦磨损性能及机理. 实验结果表明: 温度对铜基石墨固体自润滑复合材料的自润滑性能有较大的影响, 在较高温度条件下, 铜基石墨固体自润滑复合材料的耐磨性主要取决于铜合金基体的强度; 选用合适的石墨粒度和多元基体合金化, 可使铜基石墨固体自润滑复合材料在0～500.℃温度条件下保持较好的自润滑特性.     

石墨对钒钛铁精矿原位制备铁基摩擦材料的影响

在真空条件下以钒钛铁精矿为原料原位碳热还原烧结制备铁基摩擦材料,研究石墨含量对铁基摩擦材料显微组织、硬度、摩擦性能以及磨损形貌的影响。结果表明,利用钒钛铁精矿可制备出性能优良的铁基摩擦材料;少量石墨促进烧结过程,石墨含量为5%时,材料组织最致密,且孔隙趋于球形,过量石墨阻碍烧结颈的形成,割裂基体;当石墨含量从3%增加到7%时,材料硬度降低约36%,摩擦系数降低约25%,材料的磨损机制由粘着磨损和轻微的磨粒磨损转变为石墨自润滑磨粒磨损,最后转变为犁削磨损;适当的石墨含量和孔隙度能有效降低磨损率,石墨含量为6%时耐磨性最好,其磨损率为2.00×10-7cm3/J。     

镀镍石墨粉对铜基石墨复合材料力学性能的影响

采用粉末冶金工艺制备铜基石墨复合材料,考察烧结工艺、石墨粉颗粒表面镀镍及强化相对铜基石墨复合材料的力学性能和组织结构的影响,并对材料的组分、显微组织形态结构及断口形貌等进行系统的观察和分析,测试材料的硬度、冲击韧性和在室温、300℃、500℃各温度的压溃强度。结果表明:采用镀镍石墨粉改善了石墨和铜合金基体界面结合状态,界面结合更加牢固紧密,明显提高铜基石墨复合材料的力学性能,室温压溃强度和冲击韧性提高了30%~50%,高温强度提高了35%~60%,而对复合材料的硬度影响不大,复压复烧工艺更有利于发挥镀镍石墨粉的优越性。     

镀镍石墨颗粒增强耐磨CuCrZr基复合材料组织及性能研究

采用金属熔化铸造工艺制备了体积分数为2%、6%、8%的镀镍石墨颗粒增强铬锆铜基复合材料,分析测试了其组织、硬度、耐磨性及磨损特征,并与基体铬锆铜进行了对比研究。结果表明:镀镍石墨颗粒均匀分布在基体中,并与基体紧密结合,无其他明显反应物生成;未经热处理的体积分数为8%的镀镍石墨颗粒增强铬锆铜基复合材料的硬度最低,为HV135.75,仅比基体铬锆铜硬度减少了2.9%;体积分数为8%的镀镍石墨颗粒增强铬锆铜基复合材料的耐磨性高于体积分数为2%和6%的镀镍石墨颗粒增强铬锆铜基复合材料,其耐磨性较基体提高了76%;磨损表面较为平坦,无明显的犁沟及抛削坑,颗粒组织均匀,表现为磨粒磨损。     

石墨/铜铁基自润滑复合材料的摩擦学性能研究

采用感应加热烧结粉末冶金的方法,以铜铁合金为基体,添加石墨制备石墨/铜铁基自润滑复合材料,对比研究了添加石墨前后2种材料的组成、结构、表面形貌及摩擦学性能,并分析了磨损机理。研究结果表明:添加石墨能起到润滑作用,使材料的摩擦因数减小,磨损率降低;添加的石墨一部分转化成新态,其余则进入材料的空隙中,在摩擦过程中形成润滑膜起到减摩的作用;添加石墨后,摩擦材料的磨损机制由粘着磨损变为磨粒磨损。     

铜包石墨对酚醛树脂基复合材料摩擦学性能的影响

目的 提高石墨与酚醛树脂的界面结合强度,改善酚醛树脂基复合材料的摩擦学性能。方法 用高温浸渗法制备铜包石墨,并制备铜包石墨-酚醛树脂基复合材料。通过摩擦磨损实验,研究铜包石墨对酚醛树脂基复合材料摩擦学性能的影响,并对比相同成分铜/石墨混合填充酚醛树脂基复合材料的摩擦学性能。通过扫描电子显微镜、能谱仪和光学显微镜对摩擦磨损表面进行分析,研究材料摩擦磨损机理。结果 石墨表面经过金属铜处理后,金属铜由分散的聚集态转变为附着态,制备的铜包石墨颗粒整体分散度高、形状好。铜包石墨-酚醛树脂基复合材料中石墨与基体界面结合紧密,保持了酚醛树脂的连续相结构,摩擦磨损表面相对平整,复合材料平均比磨损率为3.98×10^?6 mm³/(N.m),瞬时摩擦系数波动幅度小,摩擦磨损机理以粘着磨损为主。相同成分制备的铜/石墨混合填充酚醛树脂基复合材料的界面结合度较差,摩擦磨损表面有较多裂痕,复合材料平均比磨损率为7.80×10^?6 mm³/(N.m),瞬时摩擦系数波动幅度大,摩擦磨损机理以磨粒磨损和粘着磨损为主。结论 石墨通过表面金属铜处理,不仅能提高与基体界面结合强度,还能同时有效提高酚醛树脂基复合材料的耐磨性能和摩擦稳定性。     

空间有序石墨/铝基自润滑复合材料的制备北大核心CSCD

利用选择性激光烧结技术制备了空间有序的石墨骨架,并对石墨骨架进行二次固化、浸渍强化、镀铜等处理,进而将镀铜石墨骨架和铝合金进行铸造复合,制备了空间有序石墨/铝基自润滑复合材料,并对复合材料及铝合金基体的摩擦系数进行研究。结果表明:载荷为100~200 N时,随着载荷的增加,石墨/铝基自润滑复合材料稳定摩擦阶段的摩擦系数增大,当载荷为100 N,石墨含量10%时,复合材料的稳定摩擦阶段的摩擦系数低至0.30左右,铝合金基体的稳定摩擦阶段的摩擦系数为0.65左右。     

Synthesis and studies of properties of graphite oxide and thermally expanded graphite

Graphite oxide is synthesized using various reaction parameters. Stagewise evaluation of graphite oxidation dynamics in the course of synthesis is carried out using the method of sample collection and thermogravimetric analysis. Thermally expanded graphite with high texture characteristics was obtained from graphite oxide. Properties of graphite oxide and thermally expanded graphite were determined using scanning electron microscopy, X-ray diffraction, thermogravimetry, differential scanning calorimetry, energy dispersive spectroscopy, and low-temperature adsorption of nitrogen. The values of capacity of supercapacitors based on graphite oxide and expanded graphite are found.     

Influence of graphite morphology on dry sliding wear of flake graphite cast irons

Abstract

Four flaky graphite cast irons of different graphite structures with a pearlitic matrix were prepared to clarify the graphite structure's influence on the dry sliding wear property. Two melts of cast iron with different carbon contents were solidified at two different cooling rates. The four resultant samples had type A flaky graphite or type D eutectic graphite structure with different graphite volume fractions and fully pearlitic matrixes. A pin on the disc type wear test evaluated the four samples' dry sliding wear properties. Results showed that the type D graphite structure wore down faster than the type A graphite structure did. The type of graphite morphology influenced the specimen wear rate as strongly as the graphite volume fraction did in flaky graphite cast irons of this experimental range.     

Effect of graphite content on electrochemical performance of Sn-SnSb/graphite composite powders

Sn-SnSb alloy was synthesized by reducing a aqueous solution containing Sn（Ⅱ） and Sb（Ⅲ） salts with NaBH4 in the presence of sodium citrate. The product was characterized by X-ray diffractometry（XRD） and scanning electron microscopy（SEM）. Sn-SnSb/graphite composite powders were prepared by mechanical milling and the mass fraction of graphite was increased from 20% to 50%. The effect of graphite content on the electrochemical performance of Sn-SnSb/graphite composite electrode was investigated. The results show the increase of graphite content is in favor of enhancing the first charge-discharge efficiency and improving the cycle performance, but the capacity of the composite electrode decreases with increasing content of graphite.     

Effect of bismuth on refinement of graphite in thin wall spheroidal graphite cast iron

Abstract

Although it is known that the addition of bismuth refines the graphite nodule in spheroidal graphite cast iron, the refinement mechanism has not yet been clarified. In this research, the effect of bismuth on the refinement has been investigated by examining the microstructure of the spheroidal graphite cast iron containing a small amount of bismuth. Bismuth was added at 0˙01 mass% to the spheroidal graphite cast iron melt containing 3˙5–3˙7 mass% carbon and 2˙0– 2˙8 mass% silicon, then the melt was poured into the mould to obtain the stepped test bar with 2, 3, 5 and 10 mm thicknesses. The graphite nodule increased as the bismuth content increased. The diameter of the graphite nodule decreased as the thickness decreased, namely, as the cooling rate increased. The graphite nodule was further refined by the addition of bismuth. The increase in silicon content increased the graphite nodule count and the ferrite in the matrix. It postulated that bismuth exists as simple substance or a compound in the vicinity of the nucleus of the graphite.     

Topology of nanometric graphite films

This work submits the results of a study in which the combinational scattering (CS) spectroscopy and electronic and optical microscopy of nanometric single-crystal graphite films obtained by precipitating in gas phase were used. It is shown the graphite material samples synthesized in this manner are fine, highly streamlined films that grow alongside of the substrate surface. The films feature a fairly smooth surface and thicknesses of 100-1 atomic layers. The study of the topologic properties of the material, such as the formation of folds along the entire surface and the occurrence of waveform ripples on some surface areas, showed that they may appear due to large differences in the carbon film and nickel substrate thermal expansion factors. The film thickness was assessed for the observed parameters of the periodic structures and the results comply with data obtained using other techniques. In some areas of the material in study, the graphene layers spontaneously split and form bubbles. The results of the CS analysis of various bubbles on studied film surfaces are evidence that, similar to the film itself, the walls of bubbles are composed of different numbers of graphite layers. It is shown that transparent bubbles in which meshlike topology is observed are formed with a single atomic layer.     

Irradiation induced creep of graphite

The status of graphite irradiation induced creep strain prediction is reviewed and major creep models are described. The ability of the models to quantitatively predict the irradiation induced creep strain of graphite is reported. Potential mechanisms of in-crystal creep are reviewed as are mechanisms of pore generation under stress. The case for further experimental work is made and the need for improved creep models across multi-scales is highlighted.     

Effect of sulfur on graphite aspect ratio and tensile properties in compacted graphite irons

In this research, the effect of sulfur content on graphite aspect ratio and tensile properties of compacted graphite iron (CGI) was investigated. Different samples with sulfur levels ranging from 0.023 to 0.080% were produced in which the amount of magnesium was the same. Magnesium was added as FeSiMg by sandwich method and sulfur was added as pyrite powder in reaction chamber of the mold. In order to study the microstructure and mechanical properties, metallographic examination and mechanical tests were conducted on specimens. The metallographic results showed that increasing of sulfur level from 0.023 to 0.080% in constant magnesium level of 0.057% increases the graphite aspect ratio from 0.6 to 12.4. Evaluation of the mechanical test results indicated that increasing of sulfur level, decreases the tensile properties of compacted graphite iron.     

Studies of ultrasonication of exfoliated graphite

The present study is devoted to ultrasonication of exfoliated graphite in different organic solvents (dimethyl sulfoxide, propanol-2, and chloroform). Graphite nanoplatelets are obtained as a result of strong acoustic treatment (10 W/cm³). The obtained samples are investigated by scanning electron microscopy, energy-dispersive X-ray spectroscopy, X-ray diffraction, low-temperature nitrogen adsorption, FTIR and Raman spectroscopies. It is found that the structural and texture characteristics of the obtained materials significantly depend on the type of a solvent.     

石墨表面钛金属化微观组织分析

利用XRD、SEM和EDX对石墨表面钛金属化微观组织进行了分析研究。结果表明，微观组织依次为内层（石墨）、过渡层（620μm）、致密层（40μm）及外层（α-Ti），XRD及EDX分析证实了致密层的物相为碳化钛，SEM分析证实了致密层与过渡层及w层结合牢固。但还发现，在Ti层与致密层界面处发现微裂纹，可能是因热膨胀系数差异大而产生的热应力所致，可通过缓冷方式来减小热应力。在致密层与过渡层界面处却未发现，主要因为Ti与石墨发生界面反应，形成碳化钛。