Synthesis Of Layered Silicates, Phosphates And Their Tribological Properties Investigation

The energy consumption caused by friction and wear of mechanical drive accounted for one third of total energy consumption global annual. Effective lubrication is the key to solve this problem. With the rapid development of transportation, aerospace and other industries, harsh conditions lubrication needs of heavy-duty, high-speed, and strong shock has been brought. Molybdenum disulfide has a lamellar structure, which is essential to select solid lubricant in the harsh lubrication conditions. Due to the scarcity of molybdenum resources and easily oxidized failure, it is an issue of significance to search alternatives for molybdenum disulfide. From the characteristics of the crystal structure, previous research mainly involves layered oxides such as layered sodium silicate and layered zirconium phosphate. Although it has made some progress, there are some different defects for each substance. So further study is needed.On the basis of preliminary work, layered compounds such as layered sodium silicate, layered zirconium phosphate, layered magnesium phosphate,and their modified materials were prepared in this paper. Also, their tribological properties in lithium grease were studied. Single or powder diffraction technology and the modern instrument analytical method as PXRD, SEM,TG-DSC, FT-IR were employed to determine and characterize the crystal structures and physicochemical properties of the layered compounds. The main findings are as follows:1. Layered sodium silicates ?-Na2Si2O5 (particle size of about 3 - 10 ?m)was synthesized via facile methods under mild conditions (260 - 300?). High energy consumption and the presence of vitreous sintered product problems in the traditional high-temperature synthesis process were overcomed. The tribological properties of ?-Na2Si2O5 utilized as an additive in lithium grease were evaluated with a four-ball tester. The results showed that ?-Na2Si2O5 exhibit better antiwear, friction-reduction, and load-carring capacity than MoS2 under the same friction and wear test conditions. PB value of ?-Na2Si2O5 lithium grease was 951 N higher than MoS2. In a long run time experiments, the maximum load-carring capacity of ?-Na2Si2O5 lithium grease was 686 N,significantly higher than MoS2(only 294 N). Wear scar diameter of ?-Na2Si2O5 lithium grease under maximum load bearing was 0.46 mm, compared with the wear scar diameter of base lithium grease and MoS2 lithium grease under 294 N were reduced 0.04 mm and 0.06 mm, respectively. The friction coefficient of(3-Na2Si2O5 lithium grease in the load range 98 - 686 N was significantly reduced from 0.096 to 0.057.2. Owing to the strong hygroscopic problem of layered sodium silicates,this paper focus on the inorganic layered materials that crystal structure can be stably in a solvent system. Layered zirconium phosphate a-ZrP with high crystallinity, uniform diameter (600 nm) and regular hexagon forms was synthesized in a mild NaF - ZrO - P2O5 - H20 system under hydrothermal conditions. a-ZrP has the characteristic of ion exchange, the interlaminar hydrogen ion could be exchanged by various metal ions, causing the layer spacing or force between layers changes, which would influence on its tribological properties. In this article, copper, magnesium, and sodium ion exchanged a-ZrP materials were synthesized by pressurizing exchange method,the exchange degree reached 93.90 %, 91.93 %, and 98.72 %, respectively.Tribological Properties of a-ZrP materials before and after ion exchange were examined in lithium grease. Experimental results indicated that, adding 2.0 wt.%a-ZrP and different metal ion-exchanged a-ZrP materials can significantly improve the load-carrying capacity (PB) of lithium grease. The PB value of lithium grease increased from base grease 353 N to ?-ZrP 980 N, Cu-a-ZrP 1235 N, Mg-a-ZrP 1098 N, and Na-a-ZrP 1098 N, respectively; compared with MoS2549 N, have obvious advantages. There is some difference in lubricity for a-ZrP exchanged by different ions (Cu2+, Mg2+, Na+), among which Cu-a-ZrP performs the best. In a long run time experiments, the maximum load-earring capacity of Cu-?-ZrP lithium grease can reach 784 N, a-ZrP, Mg-a-ZrP, and Na-?-ZrP lithium grease was only 588 N.3. For there has low efficiency problem in the preparation of Cu-?-ZrP in the conventional ion exchange method. Cu-a-ZrP with high crystallinity and regular morphology was synthesized directly in hydrothermal synthesis system NaF - CuO - ZrO - P2O5 - H2O. Cu2+ exchange degree is 97.52 %. Cu2+ is proved in exchangeable position of Cu-?-ZrP crystals by elemental analysis and H+ ion exchange. The crystal structure of Cu-a-ZrP was determined ab initially via the X-ray powder diffraction data, determining the optimal formula Cu(OH)2Zr(HPO4)2·2H20. The tribological properties of Cu-?-ZrP utilized as an additive in lithium grease were evaluated with a four-ball tester. Test results showed that the load-carrying and anti-wear capacity of Cu-?-ZrP superior to MoS2 under the same working conditions. Compared to a-ZrP, the films formed by Cu-?-ZrP are more tighter in the resistance to wear under the heavy load.4. The pursuit of the product engineering is selecting the resource-rich elements to get cheaper materials. A layered magnesium phosphate was prepared in ionothermal synthesis system oxalic acid/choline chloride. Diethylamine(denoted DEA) can control the particle size of sample effectively for it adjust the basic of the synthesis system. When adding the appropriate amount DEA (DEA /Mg = 0.62), a single crystal was obtained. The single crystal diffraction technology was employed to determine the crystal structure, determining the optimal formula Mg4(P207)2·6H20. Also, it proved to be a novel Mg2+ion-exchanged layered magnesium phosphate material for both the layer and the interlaminar containing magnesium ions.5. Mg4(P2O7)2·6H20 was synthesized in hydrothermal synthesis system Na2O - MgO - P2O5 - H2O, when adding the appropriate amount of sodium hydroxide (Na2O / Mg (molar ratio) = 0.6-1.0). The tribological properties of Mg4(P2O7)2·6H20 utilized as an additive in lithium grease were evaluated with a four-ball tester. The results showed that adding 3.0 wt.% Mg4(P2O7)2·6H20 exhibit better load-carring and antiwear capacity. PB value of Mg4(P2O7)2·6H20 lithium grease was 1098 N. In a long run time experiments, the maximum load-carring capacity was 882 N. Also, its antiwear properties was significantly better than MoS2 grease under the same experimental conditions. The wear scar diameter of MoS2 grease is 0.46 mm, while the wear scar diameter of Mg4(P207)2·6H20 grease is 0.34 mm. The layered structure of Mg4(P207)2·6H20 is stable in the friction process.