The friction and wear behavior and mechanism as well as the mechanical properties of polytetrafluoroethylene (PTFE) composites filled with potassium titanate whiskers (PTW) and short carbon fibers (CF) under dry, wet and alkaline conditions were investigated. Experiments indicated that owing to appropriate cooling and boundary lubricating effects, the filled PTFE composites showed much lower frictional coefficient and better wear resistance under alkaline than dry and wet sliding conditions. The wear resistance of carbon-fiber-filled PTFE was much better than that of potassium titanate-whisker-filled PTFE composites in water. Results also showed that the transfer film on counterpart rings was significantly hindered by water and alkali. Hydrophilic-filler-reinforced PTFE composites yield higher wear rate when sliding under water.
Humidification is an important step in humid air turbine system. The calculation on humidification is carried out at 423.15—573.15K, 5—15MPa. The results suggest that to produce high-enthalpy moist air, high water temperature and large water flow are needed. The water temperature is the most sensitive parameter to the humidification tower. And it is better for the humidification tower to work at temperature higher than 523 K when the system pressure is higher than 5 MPa. The comparison between the model used in this paper and ideal model shows that the ideal model can be used in simulation to simply the calculation when the temperature is lower than 473 K and pressure is lower than 5 MPa.
The surface of nano-La2O3 was modified. Effects of various amount of treated nano-La2O3 on the mechanical and tribological properties of PTFE were investigated. Mechanisms that contribute to the properties of PTFE composites are also studied. Results indicate that treated nano-La2O3 can increase the mechanical and tribological properties of PTFE simultaneously. With 1wt.% of treated nano-La2O3, the rigidity, tensile strength, notched impact and wear resistance of PTFE nanocomposites were increased by 25.1%, 14.1%, 20.3% and 36.7% respectively over pure PTFE. The degradation temperature of PTFE was improved by 14 ℃ by adding only 5% nano-La2O3. The wear resistance reached the highest value when the composite contained 10% treated nano-La2O3, which is about 110 times higher than pure PTFE. Furthermore, treated nano-La2O3 strengthened the bonding between the transfer film and the counterpart surface. A coherent and smooth transfer film on the counterpart surface of PTFE composites can be observed, while pure PTFE can not do.
