Study On Preparation And Tribological Proporties Of Cu/Ni-Mg-Al Hydrotalcite-like Compounds

In this paper, Cu/Ni-Mg-Al-CO3 hydrotalcite were synthesized by hydrothermal. And discussed the metal cationic concentration of reaction solution, the mole ratio of Cu²⁺/Mg²⁺ (or Ni²⁺/Mg²⁺) and reaction time on structure of the Cu/Ni-Mg-Al-CO3 hydrotalcite. The optimum conditions of the Cu-Mg-Al-CO3 hydrotalcite were obtained: the mole ratio of Cu²⁺: Mg²⁺: Al3+= 2:8:5, 0.5 mol / L for the metal cationic concentration of reaction solution, 8 h for reaction time. The optimum conditions of the Ni-Mg-Al-CO3 hydrotalcite:the mole ratio of Ni²⁺: Mg²⁺: Al3+ = 2:8:5, 1.0 mol / L for the metal cationic concentration of reaction solution, 6 h for reaction time. The structure, morphology and thermal stability of Cu/Ni-Mg-Al-CO3 hydrotalcite were studied. The results showed that Cu/Ni-Mg-Al-CO3 hydrotalcite prepared by hydrothermal was the single crystalline phase.Their crystallinity was good, and their particle sizes were in range of 40⁵0 nm. When they were heated to 300℃, the structure collapsed, in the meantime dehydroxylation of lays.Cu/Ni-Mg-Al hydrotalcite-like compounds intercalated by dodecyl sulfonate were prepared by ion exchange method, sodium dodecyl sulfate as intercalator. And discussed solution pH value and reaction time on the structure of Cu/Ni-Mg-Al hydrotalcite-like compounds, the optimum conditions of Cu-Mg-Al hydrotalcite-like compounds were determined: pH = 4, 2 h for reaction time. The optimum conditions of Cu-Mg-Al hydrotalcite-like compounds pH = 4, 5 h for reaction time. XRD results showed that the height Cu-Mg-Al-CO3 hydrotalcite interlayer channel changed to 2.043nm from 0.285nm, and the height Cu-Mg-Al-CO3 hydrotalcite interlayer channel changed to 1.959nm from 0.284nm. Cu/Ni-Mg-Al hydrotalcite-like compounds intercalated dodecyl sulfonate were prepared successfully. However, due to weakening of the force between laminates, their thermal stability decreased. The contact angle and dispersibility in the base oil of Cu/Ni-Mg-Al hydrotalcites and Cu/Ni-Mg-Al hydrotalcite-like compounds were compared. The results showed that the dispersibility of Cu/Ni-Mg-Al hydrotalcite-like compounds in the base oil were better.The tribological properties of Cu/Ni-Mg-Al hydrotalcite-like compounds were studied. The results showed that, compared with the base oil, Cu/Ni-Mg-Al hydrotalcite-like samples could reduce coefficient of friction more than 30%, the rubbing pairs mayed repaired significantly. The tribological properties of Ni-Mg-Al hydrotalcite-like compounds was the best one. In addition, Cu/Ni-Mg-Al hydrotalcite-like samples can reduce operating power of equipments and oil temperature. Studies suggest that repairing of hydrotalcite-like compounds is closely related to its layed structure. It contains a large number of active groups （such as hydroxyl, etc.）, can effectively cover the rubbing pair, shear slip occurs between layers, thereby reducing the friction coefficient. In addition, micron-nano spherical powder hydrotalcite play a role of "ball bearing" on the rubbing pairs, reducing the coefficient of friction.