Synthesis and tribological investigation of carbon nanotube, onion-like carbon and nanodiamond reinforced nickel matrix composites

碳纳米管、洋葱状碳和纳米金刚石被认为是金属基复合材料极具发展前景的增强颗粒。这是由于其出色的物理性能，如高强度，硬度，导电性和导热性，以及减少摩擦和磨损。本提案涉及碳纳米颗粒增强镍基复合材料的生产及其微观结构，化学和摩擦学特性。这将提供不同复合材料在干摩擦下摩擦学性能的直接比较。第一个里程碑将是优化制造的粉末冶金参数，以最佳地适应每种增强。因此，必须实现和分析稳定且均匀的颗粒/溶剂分散。随后的复合材料将在密度、微观结构、硬度、形貌、颗粒/基体分散和烧结后结构颗粒质量方面进行分析、比较和优化。第二个目标是通过进一步表征产生的磨损轨迹来解释和比较复合材料的摩擦学行为。这包括微观结构、氧化物形成和颗粒位移，以及磨损速率和磨损机制。此外，将监测颗粒降解甚至石墨化。如果观察到，负责转换的负载范围将是有趣的。因此，作为相对湿度和载荷的函数，在上述转换前后的摩擦学行为将为控制机制提供进一步的线索。下一步是预测镍基体的平均晶粒尺寸作为颗粒类型和体积分数的函数。随之而来的明显的颗粒基质钉钉效应与颗粒和晶粒大小有关。为此，Zener方程将采用实验显微结构表征来适应相应的镍基复合材料。因此，平均晶粒尺寸和复合材料的磨损性能之间的直接关联将是可能的。实现了目前的目标，最合适的颗粒可用于镍基复合材料的摩擦学应用。目前的研究可能是使用其他基质材料在该领域进行进一步科学研究的基础，因为据我们所知，没有这样的出版物比较不同的碳纳米颗粒作为增强相在同一金属体系中的摩擦学性能。

Carbon nanotubes, onion-like carbon and nanodiamonds are considered as highly promising reinforcement particles for metal matrix composites. This is justified by their outstanding physical properties like high strength, hardness, electrical and thermal conductivity as well as friction and wear reduction. The present proposal deals with the production of carbon-nanoparticle-reinforced nickel matrix composites and their microstructural, chemical and tribological characterisation. This will provide a direct comparison of the different composites concerning their tribological properties under dry friction.The first milestone will be to optimise the powder-metallurgical parameters of the fabrication, best adapted to each reinforcement. A stable and homogeneous particle/solvent dispersion must thus be achieved and analysed. The subsequent composites will be analysed, compared and optimised in terms of density, microstructure, hardness, topography, particle/matrix dispersion and post-sintering structural particle quality.The second objective consists in interpreting and comparing the tribological behaviour of the composites through further characterisation of the produced wear tracks. This involves the microstructure, oxide formation and particle displacement as well as the wear rate and wear mechanisms. Furthermore, particle degradation or even graphitisation will be surveilled. If observed, the load range responsible for the transformation will be of interest. Consequently, the tribological behaviour, as a function of the relative humidity and load, before and after said transformation will bring further clues as to the governing mechanisms.The next step is the prediction of the mean grain size of the nickel matrix as a function of particle type and volume fraction. A consequent and pronounced particle-matrix pinning effect correlates particle and grain size. For this purpose, the Zener equation will be adapted using experimental microstructural characterisation to fit the corresponding nickel matrix composite. Thus, a direct correlation between the mean grain size and the wear behaviour of the composites will be possible.The present objectives achieved, the most fitting particle can be favoured for tribological applications in nickel matrix composites. The presented study could be the starting grounds for further scientific work in this field using other matrix materials, since, to the best of our knowledge, no such publication compares the tribological properties of different carbon nanoparticles as reinforcement phases in the same metal system.