Search

Vanadium (IV)-oxo-dicyclodithiophosphate (VDTP) was prepared and its additive properties evaluated using a four-ball machine. The results show that VDTP exhibits better extremepressure performance, but lower antiwear activity, when compared with ZDTP. The reaction film composition, characterised by scanning Auger microscopy (SAM), X-ray photoelectron spectroscopy (XPS) and diffractometer surface techniques, reveals that the antiwear and friction layer containing vanadium oxide, phosphate/phosphide, and sulphide, prevent the rubbing pairs from contacting directly, resulting in better extreme-pressure and antiwear behaviour.

The bis(isoquinoline) adduct of bis(O,O′-dibutyldithiophos-phato)nickel (II), Ni(dtp)2 · 2IQ, has been prepared; its crystal structure reveals that the nickel atom is bonded to four sulphur atoms of the dithiophosphate molecule, and two nitrogen atoms in the isoquinoline ring, to form a six-coordinated complex. Evaluation of the adduct's properties as an extreme-pressure (EP) and antiwear (AW) additive was conducted using a fourball machine. The results show that Ni(dtp)2 · 2IQ exhibits better load-carrying capacity than Ni(dtp)2 and Zn(dtp)2, but poorer antiwear abilities. SEMs show that a wear scar surface on the ball lubricated with the adduct was much rougher than for those with isooctanol, Ni(dtp)2 and Zn(dtp)2, respectively. Further, energy dispersive X-ray (EDX) spectra indicates that the sulphur concentration in the wear scar lubricated with the adduct is much less than that of Ni(dtp)2, which leads to a lesser wear reducing ability.

Tungsten dithiolate was synthesised by the reaction of WO3 with toluene-3,4-dithiol (abbreviated to H2TDT), and its extreme-pressure and antiwear properties were investigated on a four-ball tester. The results showed that it possesses fairly good extreme-pressure and antiwear abilities. Based on analytical results obtained by Scanning Auger Microprobe and Scanning Electron Microscopy, as well as Electron Ionisation Mass Spectra fragments, the antiwear mechanism of WTDT suggested that a permeating layer containing WC, WS2, and WO3 played an important role in the antiwear and friction-reducing action.

By mixing 0.5wt.% silver complex with 2-ethylhexyl phosphonic acid mono 2-ethylhexylester (AgL·HL) into a conventional zinc dithiophosphate (ZDTP), a new compounded extreme-pressure and antiwear as well as antiseizure additive was obtained. The antiseizure and load-carrying performance of the mixture (Zn-AgDTP) was significantly improved in comparison with ZDTP and AgL·HL. The synergistic action and tribochemical mechanism is proposed on the basis of the worn surface analysis by scanning Auger microprobe (SAM), X-ray photoelectron spectroscopy (XPS) and X-ray micro-diffraction (XRD).

A series of mixed-ligand complexes of group VIII metals, M(DIAFO)2(NCS)2 and M(DIAFH)2X2 (M = FeII, CoII, NiII, X = NCS−, Cl−) with the 3,3′-bridged derivative of 2,2′-bipyridyl (bipy) (1) were prepared, where DIAFO (2) and DIAFH (3) are 4,5-diazafluoren-9-one and 4,5-diazafluoren-9-hydrazone, respectively. These complexes were investigated by i.r., u.v.-vis-near i.r. spectroscopy and by variable-temperature magnetic susceptibility measurements. The electronic spectra show that the two ligands exert a field strength far removed from the FeII cross-over value. All the complexes are paramagnetic, following the Curie-Weiss law in the 77–300 K range. A typical crystal structure of Co(DIAFO)2(NCS)2 for these compounds was determined with orthorhombic, space group Pcan, a = 10.377(5) A, b = 13.289(6) A, c= 16.629(7) A, V = 2293(2) A3, Dc = 1.563 g cm−3, F(000) = 1091.74, Z = 4, R = 0.043, R∝= 0.047. Steric effects are thought to be operative in both ligands studied, but are weaker than those of the typical bidentate diimine ligand bipy.