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很有前途的金属基复合材料增强颗粒。这是因为它们具有优异的物理性能，如高强度、高硬度、导电性和导热性，以及摩擦和磨损减少。本提案涉及碳纳米颗粒增强镍基复合材料的制备及其微观结构、化学和摩擦学特性。这将提供不同复合材料在干摩擦下的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，最适合每种增强材料。因此，必须实现稳定和均匀的颗粒/溶剂分散，并对其进行分析。随后的复合材料将从密度、显微组织、硬度、表面形貌、颗粒/基质分散性和烧结后结构颗粒质量等方面进行分析、比较和优化。第二个目标是通过对产生的磨痕的进一步表征来解释和比较复合材料的摩擦学行为。这涉及到显微组织、氧化物的形成和颗粒位移以及磨损率和磨损机制。此外，还将对颗粒降解甚至石墨化进行监控。如果观察到，负责转换的负载范围将是感兴趣的。因此，转变前后的摩擦学行为，作为相对湿度和载荷的函数，将为控制机制提供进一步的线索。下一步是预测作为颗粒类型和体积分数的函数的镍基质的平均颗粒尺寸。随之而来的显著的颗粒基质钉扎效应使颗粒和颗粒尺寸相互关联。为此，将使用实验微结构表征对齐纳方程进行修正，以适应相应的镍基复合材料。因此，平均颗粒尺寸与复合材料的磨损行为之间可能存在直接的关联。根据目前的目标，最适合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这一领域进一步科学工作的起点，因为据我们所知，还没有这样的出版物比较不同碳纳米颗粒作为同一金属系统中增强相的摩擦学性能。

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.