Papers by Author: Yi Xu

Abstract: The nano-effects of nano-Cu lubricating material in equipment maintenance were researched from reducing friction effect, antiwear effect and repairing effect by comparing tribology properties of nano-Cu lubricating material with micro-Cu material. The nano-effect mechanism was discussed. The results indicated that the reducing friction effect and the antiwear effect can make the friction coefficient and the worn track width of lubricant reduce to 16% and 40% respectively. The repairing effect can make the nano-Cu lubricating material forms repairing film on wore surface. That of all is decided by the characteristics of nano-Cu lubricating material.

Abstract: The prepared n-Cu particles with the particle size about 20 nm by KBH4 reduction method in aqueous solution was surface modified using silane coupling agent. The surface modification mechanics was researched. The tribological performances of n-Cu particles were tested by friction wear test machine. The results show that the modified n-Cu paritcles by silane coupling agent have high purity, good dispersion performances and wonderful surface activity. In friction process, the modified n-Cu particles can form a layer of organic-inorganic compound film with synergistic effect on worn surface, which improves the tribological performances of friction material.

Abstract: Nano-scale hydroxyl magnesium silicate was synthesized successfully by using hydrothermal method. The composition of as-prepared powder was proved chrysotile which adheres to monoclinic crystal system (a kind of hydroxyl magnesium silicate) by using X-ray Diffraction (XRD) technology. The morphology and microstructure of chrysotile powder were characterized by using scanning electron microscope (SEM) and transmission electron microscope (TEM). Nano-particles and nano-rods were observed in SEM micrograph. Moreover, smaller-size nano-particles and nano-fibres were observed by using TEM. Based on results of SEM and TEM, the growth mechanism of chrysotile powder under hydrothermal conditions was discussed.

Abstract: In the present work, surface-coated Cu nanoparticles with FCC structure and an average size of 40 nm were prepared by reducing reaction and surface modification technique. The morphology and phase structure of the nano-copper were characterized by transmission electron microscope (TEM). The ball-on-disc tester and ring-on-block tester were performed to study the tribological properties of surface-coated Cu nanoparticles as oil additive. The tests were carried out under the lubrication of 50CC oil alone and oil containing surface-coated nano-copper additives. The morphologies and elementary distributions of the worn surfaces were analyzed by scanning electron microscope (SEM) and energy dispersive spectrometry (EDS), respectively. Results indicate that surface-coated nano-copper additives can significantly improve the wear resistance and load-carrying abilities of 50CC oil, as well as reduce friction coefficient. A soft copper protective film is formed on the worn surface lubricated with oil containing nano-copper additives, which separates the worn surfaces, avoids their direct contact and reduces friction and adhesive wear. Besides, the grooves and small valleys on the worn surfaces are found to be partly filled and repaired by nano-copper, as makes the worn surface repaired and smoother.

Abstract: A new type of composite coating (321—Al coating) was prepared by using the 321 austenitic stainless steel wire feed stock as the anode and aluminum wire as the cathode in arc spraying process. In order to compare with the new composite coating, the traditional 321 coating with twin 321 stainless steel wires was fabricated. The microstructure and wear resistance of the coatings were characterized by means of scanning electron microscopy (SEM), X-ray diffraction (XRD), energy dispersion spectroscope (EDS) and MM-200 ring-block type sliding wear tester. Results showed that, except for the aluminum phase addition in the 321—Al coating, no other extra phases produce in comparing with the 321 coating. However, due to the additional aluminum, the 321—Al coating performs quite different microstructure characteristics and tribological behavior. The oxygen content and microhardness of the 321—Al coating are lower than that of the 321 coating, but wear losses are pretty much under the oil lubricated sliding condition. The effect of the microstructure on the wear behavior of the 321—Al coating was also discussed, which is mainly relevant to the characteristic of “ductile aluminum and hard stainless steel composite phases inter-depositing”.

Abstract: A special kind of surface modified copper nanoparticles was selected as the auto-reconditioning materials to in situ generate a copperized protective film on iron-base metal surfaces under designed tribological conditions. The morphologies and element distributions of the formed film were observed and determined by scanning electron microscopy (SEM) and energy dispersive spectrometry (EDS). The micro mechanical properties and tribological behaviors were investigated by nano test system and ball-on-disc tribotester. The results show that the morphology of the protective film is smooth, the nano-hardness decreases by 46% and the friction coefficient of the copperized protective film is about 0.10. The forming mechanism of the auto-reconditioning film can be described that the copper nanoparticles deposit on the worn surfaces and form iron-copper alloy film with lower hardness and shear strength, which has better friction-reducing, antiwear and surface-optimizing behaviors.