Zhengfeng Jia

Synthesis, characterization, and tribological behavior of oleic acid capped graphene oxide

Graphene oxide (GO) nanosheets were prepared by modified Hummers and Offeman methods. Furthermore, oleic acid (OA) capped graphene oxide (OACGO) nanosheets were prepared and characterized by means of Fourier transforminfrared spectroscopy (FT-IR), transmission electron microscopy (TEM), and X-ray diffraction (XRD). At the same time, the friction and wear properties of OA capped graphite powder (OACG), OACGO, and oleic acid capped precipitate of graphite (OACPG) as additives in poly-alpha-olefin (PAO) were compared using four-ball tester and SRV-1 reciprocating ball-on-disc friction and wear tester. By the addition of OACGO to PAO, the antiwear ability was improved and the friction coefficient was decreased. Also, the tribological mechanism of the GO was investigated.

Synthesis, Characterization, and Tribological Behavior of Oleic Acid–Capped Calcium Borate Hydrate

In this article, a series of calcium borate, molecular formula 4CaO·5B2O3·7H2O (CB), was hydrothermally synthesized using borax and calcium nitrate. Furthermore, a of oleic acid–capped calcium borate (OAMCB) was prepared and characterized by means of Fourier transform infrared spectroscopy (FTIR), field emission scanning electron microscopy (FE-SEM), thermogravimetry (TG), and X-ray diffraction (XRD). In addition, the friction and wear properties of OAMCBs as additives in poly-alpha-olefin (PAO) were investigated using Cu-Cr-Zr alloy–AISI 52100 steel couples. Our results showed that the OAMCB improved the friction and wear by forming an interfacial boundary lubrication layer.

The Electrical conductivities and Tribological properties of Vacuum Hot-Pressed Cu/Reduced Graphene Oxide Composite

The nanoscale reduced graphene oxide/copper (rGO/Cu) pellets were synthesized by reducing aqueous solution of graphene oxide and CuSO4. The Cu/rGO composite disks with high conductivity were fabricated by a vacuum hot-pressing sintering method. The composites were characterized by transmission electron microscopy, field emission scanning electron microscopy, x-ray diffraction. The results show that the vacuum hot-pressing sintering process can produce Cu/rGO composite successfully. The conductivities and wear resistance of the sintered Cu/rGO disks are improved, respectively, as rGO nanosheets being added into the matrix and/or increasing sintering temperatures, which are attributed to the destruction of the pores and the increasing compactness.

Tribological Characteristics of Magnesium Alloy Using BN-Containing Additives under Boundary Lubricating Condition

Three kinds of BN-containing compound have been synthesized and a stable ring of B with N coordination has been formed in the molecule of borate esters. The BN-containing compounds and MoDTC were added into poly-alpha-olefin (PAO) as additives, and then the friction and wear characters were evaluated with these four lubrications by sliding AZ91D magnesium alloy discs against SAE52100 steel balls with an Optimol SRV reciprocating friction and wear tester. The morphologies of the worn surfaces of the AZ91D magnesium alloy discs were observed by a scanning electron microscope (SEM). At the same time, the elemental compositions and chemical states of several typical elements on the worn surfaces of the AZ91D magnesium alloy discs were investigated by means of X-ray photo election spectroscopy (XPS). Comparing with MoDTC, the three borate esters exhibited lower and stabler friction coefficients as low as 0.04–0.05 at 40–50 Hz reciprocating frequency, and the wear volume was one tenth of the MoDTC at 50 Hz reciprocating frequency. According to the XPS analyses, the formation of tribological chemical reaction compounds seemed to lead to lower friction coefficient and higher wear resistance.