基于流变学特性的磁性纳米粒子作为润滑添加剂的可控润滑研究

Due to the viscosity properties, lubricant can not arrive at the micro-area of tribo-pairs, but the effective lubricating components can be carrying then enter the location when magnetic nanoparticles used as lubricating additives. Thus, lubricant could be accurately and fully filled on tribo-surface, to pervious continuous lubrication and to avoid the lack of lubricant. The Applied load, the external magnetic field, the concentration of nanoparticles, friction surface state, as well as ambient temperature, can all impact on the lubricating ability of lubricant, the viscosities of which is the main factor. Moreover, the viscosity of lubricant containing magnetic nanoparticles depends on the composition of the lubrication system and the magnetic field strength. The project from the start of magnetic nanoparticles on the rheological properties of the lubrication system, by the adjusting of the magnetic field strength to investigate the rheological properties of lubricant containing magnetic nanoparticles, and then control the viscosity,shear stress,yield stress and viscosity-temperature characteristics of the lubricant, changing the friction coefficient and lubricating film thickness of the lubrication system, to avoid friction surface asperity peak contact each other and to achieve active control of the lubrication state. In practical application, by adjusting the mechanical properties of friction components operating conditions, such as the magnetic induction density, the rheological properties of lubricant, it can be realized that the lubrication of key friction components are adjustable and controllable.

磁性纳米颗粒作为润滑添加剂，可以携带有效润滑组分到达由于润滑剂粘度特性导致的不能进入的摩擦副微区，准确充分地填充于摩擦表面，实现连续润滑并避免出现润滑剂贫乏的问题。影响含磁性纳米颗粒润滑剂润滑能力的因素很多，如外加载荷、外加磁场、纳米颗粒浓度、摩擦副表面状态以及环境温度等，这其中粘度特性是影响润滑剂润滑效果重要因素，而含磁性纳米粒子润滑体系的粘度特性又取决于润滑体系的成分和所受磁场的强度。本项目从磁性纳米颗粒对润滑体系的流变性能的影响入手，通过外加磁场强度的改变考察含磁性纳米颗粒润滑剂的流变特性，进而合理控制润滑剂的粘度、剪切应力、屈服应力、粘温特性等，改变润滑体系的摩擦系数和润滑膜厚度，避免摩擦副表面微凸峰接触，实现润滑状态的主动控制。在指导实际应用中，可以通过调节摩擦部件运行环境的磁感应强度、磁流变液体的流变学性能，实现可调节、可控制的对关键润滑部位的定位润滑。

实验室制备了不同类型的可油溶的磁性纳米粒子，使用透射电子显微镜（TEM）、EDS、Ｘ射线衍射仪(XRD)、红外光谱仪和振荡样品磁强计（VSM）对其形貌、结构组成及磁学性质进行表征。使用MCR302旋转流变仪考察了纳米颗粒作为润滑添加剂的流变学及磁流变行为。自行研制了磁感应强度从2.5mT-30mT 连续可调的磁感应发生器，并与UMT-2微摩擦磨损试验机相结合用于考察磁性纳米粒子在外加磁场条件下的润滑性能。结果表明纳米粒子作为润滑添加剂在常规条件下均具有明显的抗磨减摩性能，而在外加磁场条件下，大部分磁性纳米粒子的ECR对磁场具有响应性，Ni、CuNi-2和FeNdB纳米粒子具有较好的磁场响应性。本项目从磁性纳米颗粒对润滑体系的流变性能的影响入手，通过外加磁场强度的改变考察含磁性纳米颗粒润滑剂的流变特性、摩擦学特性，为磁性纳米粒子作为润滑添加剂在可控润滑领域的应用提供理论和数据支持。