Weimin Liu

The tribological study of a tetrazole derivative as additive in liquid paraffin

In order to investigate the tribological properties of the tetrazolyl group, one oil-soluble N-alkylated tetrazole derivative was synthesized. Its load-carrying capacity, anti-wear and friction reduction properties added to liquid paraffin were evaluated using a four-ball test machine and an Optimal SRV tester. The results indicate that the N-alkylated tetrazole derivative as an additive in liquid paraffin possesses good load-carrying capacity, excellent anti-wear and friction reduction properties. The chemical states of the nitrogen element on the worn surface were investigated using X-ray photoelectron spectroscopy (XPS).

Study on tribological properties of the complex of rare earth dialkyldithiocarbamate and phenanthroline in lubricating grease

Abstract Three complexes of rare earth dialkyldithiocarbamate (DTC) and phenanthroline (Phen) were synthesized. Their tribological properties as additives in lithium grease were evaluated using a four-ball machine and a SRV machine. As a comparison, the tribological properties of molybdenum dialkyldithiocarbamate (MoDTC) as an additive in lithium grease were also investigated. The thermal stabilities of rare earth complexes were also investigated with a thermal gravity analyzer. The results indicate that these rare earth complexes possess excellent load-carrying capacity, antiwear and friction reduction properties, and high thermal stability. Their extreme pressure properties are superior to that of MoDTC. At lower concentration and lower load, the antiwear properties of lanthanum and neodymium complexes are superior to those of MoDTC. At lower concentration and higher load, the antiwear properties of the these rare earth complexes are inferior to those of MoDTC. But the wear increases, as the increase of concentration of rare earth complex. The results of Auger electron spectroscopy and X-ray photoelectron spectroscopy analyses indicate that these rare earth complexes as additives in lithium grease can form a protective film containing rare earth oxide, sulfate and an organic compound containing sulphur and nitrogen on a rubbed surface. Especially, the lubricating film rich in rare earth and sulphur contributed largely to the excellent tribological properties of EDTC. Ln. Phen.

Friction and wear behavior of nodular cast iron modified by a laser micro-precision treatment sliding against steel under the lubrication of liquid paraffin containing various additives

Abstract Nodular cast iron was modified by means of a laser micro-precision treatment. The surface roughness of the treated sample was determined with a profilometer. The friction and wear behavior of the modified specimens sliding against SAE-52100 steel under the lubrication of liquid paraffin (LP) containing various anti-wear and extreme pressure additives was investigated on an Optimol SRV oscillating friction and wear tester. The morphologies and elements distribution of the worn surfaces were observed with a scanning electron microscope and an energy dispersive X-ray analyzer, in an attempt to reveal the wear mechanisms of the surface-modified cast iron. The phase composition of the laser treated nodular cast iron was examined by means of X-ray diffraction. As the results, the friction coefficients for the laser treated cast iron are slightly higher than that for the untreated one. The wear volume loss of the treated cast iron specimen sliding against SAE-52100 steel under lubrication of LP containing various additives is only about 5–10% of that of the untreated one. The nodular cast iron specimens after laser surface modification show good surface shape and high rigidity. The substantial increase in the wear-resistance of the cast iron after laser treatment can be attributed to a significant increase in the surface hardness of the laser-modified layers and to the friction-reducing and wear-resistant action of the extreme pressure and anti-wear additives.

Investigation on the tribological properties of boron and lanthanum permeated mild steel

Abstract AISI 1045 steel was permeated with boron and co-permeated with boron and lanthanum by means of solid permeation technique. The tribological behavior of boron and lanthanum co-permeated AISI-1045 steel under dry sliding in air was investigated and compared with that of the boron permeated and tempered AISI-1045 steel specimens with a reciprocal friction and wear tester. The cross-section of the permeated and co-permeated coatings and the morphologies of the worn surface and wear debris were examined by means of scanning electron microscopy, and the chemical states of the wear debris examined by means of X-ray photoelectron spectroscopy. Then the wear mechanisms of the permeated and co-permeated layers were discussed. As the results, boron and lanthanum co-permeated specimen shows much better wear resistance than the boron permeated and tempered specimens under a load of 20 to ∼100 N and a frequency of 20 to ∼60 Hz. However, the permeation has little effect on the coefficient of friction, but liquid paraffin is significantly reducing coefficient of friction. The treated specimens contain Fe 2 B phase and exhibit more compact structure and higher hardness, and the corresponding wear debris is smaller than that of the tempered ones. The surface layers of the boron-permeated and the boron and lanthanum co-permeated specimens show some kind of solid lubricity and hence prevent the direct metallic contact of the frictional pair, thus the improved wear-resistance is reached. Moreover, Fe 2 B and B 2 O 3 in the surface layers of the boron-permeated and boron and lanthanum co-permeation specimens restrain wear during the friction process, with the generation of iron oxide and boron oxide. This leads to wear of the specimens at extended test duration.

Nickel(II) and cobalt(II) complexes with a mixed donor acyclic ligand bearing heterocyclic moieties as terminal groups

New nickel(II) and cobalt(II) complexes of a symmetric acyclic mixed O,N,S-donor ligand, S,S′-bis(8-quinolyl)-4-oxo-1,7-dithiaheptane (OESQ), with quinoline as the terminal group, [M(OESQ)(H2O)](NO3)2 [M = NiII(1) and CoII(2)], have been prepared and characterized by elemental analyses, u.v.–vis. and i.r. spectra, and by magnetic susceptibility measurement. Single X-ray diffraction analyses show that (1) and (2) are isomorphous. The nickel (or cobalt) ion in (1) [or (2)] is hexa-coordinated and the complex cation exhibits a slightly distorted-octahedral geometry defined by all five donor atoms of the ON2S2 of OESQ and a water, molecule with N2S2 in equatorial and two oxygens in axial position.