| Friction and wear are major challenges that humanities have always faced.They are one of the most common and huge present situations influencing modern manufacturing industry.They are a critical issue to solve energy loss.Lubrication is the most effective technology to reduce friction and wear,and is one of the main methods to govern the energy crisis.The core additive in the lubricant is an antifriction or antiwear agent,which can greatly improve the performance and operating conditions.Due to special physical and chemical properties of MoS2,it has better antifriction and antiwear properties and is one of the preferred nanomaterials for lubricant additives.However,the dispersion and stability of inorganic nanomaterials in lubricants and interface science issues remain key technical bottlenecks.The specific research works of this thesis are as follows:(1)One-dimensional MoS2 nanotubes were successfully synthesized through pyrolysis method by using the halloysite nanotubes(HNTs)as templates.MoS2 nanotubes were hollow tubular structures with 2.52 nm of pore size and 89.34 m2/g of specific surface area through a series of characterizations.It was proposed that MoS2 nanotubes were formed on the inside of HNTs.The tribological performances of MoS2 nanotubes with good dispersibility and stability were tested.The results indicated that average friction coefficient(COF)and average wear scar diameter(AWSD)of MoS2 with different content in the base oil were lower than that of the base oil.Especially,the average COF and AWSD of 0.08 wt.%MoS2 nanotubes in the base oil were about 39.2%and 35.0%lower than those of the 150 SN base oil at 25?.The results showed that MoS2 nanotubes with thinner walls and smaller dimensions exhibited excellent tribological properties as lubricating additives.Finally,the lubrication mechanism of MoS2 nanotubes in base oil was proposed.(2)Two-dimensional MoS2 nanosheets were successfully synthesized through hydrothermal method by using HNTs as templates.A series of characterizations determined that MoS2 with 200-300 nm of size and 5 layers was a plate structure,and it was proposed that MoS2 nanosheets were formed on the outer surface of HNTs nanotubes.By testing the tribological properties of MoS2 nanosheets,it was found that 0.08 wt.%MoS2 nanosheets had the lowest average COF and AWSD in the base oil,which were about 17.1%and 23.9%lower than the base oil.The results showed that MoS2 nanosheets exhibited good antifriction and antiwear properties as lubricating additives.(3)In order to study the structure-activity relationship and solve the problems of cost,scale and environment in the existing methods,four new combined exfoliation techniques were designed and studied,which included lithium sodium hydrothermal-shear,lithium sodium reflux-ultrasound,ammonium carbonate hydrothermal-shear and oxalic acid expansion-liquid nitrogen freezing.The bulk MoS2 were successfully exfoliated to obtain MoS2 nanosheets.The thickness of these nanosheets were 3.12-3.20 nm,1.00-5.48 nm,2.70-3.59 nm and 3.37-4.00 nm,respectively,and the number of layers were about 5 layers,2-9 layers,4-6 layers and 5-7 layers.The tribological performances of the four groups of MoS2 nanosheets were detected and found that the tribological properties of 0.08 wt.%MoS2 were better than those of the base oil.The average COF and AWSD were about 35.13%and 41.18%,21.87%and 38.09%,20.66%and 47.27%,26.46%and 44.55%,respectively,which indicated that MoS2 nanosheets with relatively well-proportioned vertical size performed excellent tribological performances.(4)In order to solve the interface problem between inorganic nanomaterials and lubricants and improve load carrying ability,the ODAB-MoS2 and ZB/MoS2 nanocomposites were prepared by using oleic acid diethanolamide borate(ODAB)as modifier and zinc borate(ZB)as antifriction and antiwear nanoparticles.A series of characterizations confirmed that the MoS2 nanosheets were modified by chemical bonding,and the ZB nanoparticles with three-dimensional polyhedral appearance were successfully loaded on the surface of the MoS2 nanosheets.Then,the lubrication performances of ODAB-MoS2 and ZB/MoS2 were inspected.The results showed that 0.06 wt.%ODAB-MoS2 has the lowest average COF and AWSD in base oil,which were about 27.9%and 22.9%lower than those of 500 SN base oil.average COF and AWSD of 0.06 wt%ZB/MoS2 in grease was decreased by about 28.2%and 23.1%relative to the base grease.The PB value of the 0.06 wt.%ZB/MoS2 in grease was promoted by about 23.1%relative to base grease.These proved that ODAB-MoS2 and ZB/MoS2 had better tribological performances,and ZB/MoS2 nanocomposites exhibited good load bearing ability. |
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