Preparation of platy Co/Al hydrotalcites using aluminum hydroxide and investigation of their tribological properties in base oil

Abstract

In this study the synthesis of Co/Al hydrotalcite (layered double hydroxides: LDH) using insoluble Al(OH) 3 by hydrothermal method is described. The syntheses were conducted under various conditions. The as-prepared Co/Al-CO 3 2--LDH was characterized by X-ray diffraction (XRD) and scanning electron microscope (SEM). The tribological properties of the products were evaluated in base oil using four-ball and plint friction testers. The LDH thus synthesized displays perfect hexagonal plate-like morphology having a disk diameter in a range of 0.2-1.5µm with a thickness of 40nm. Addition of the product Co/Al-CO 3 2--LDH, as additive to the base oil, significantly reduces the friction coefficient (22.3%) and wear (26.1%), compared to base oil alone. The morphology and chemistry of the worn surface were characterized by SEM, atomic force microscope (AFM) and X-ray absorption near edge structures (XANES) spectroscopy. The results show that the structural distortion of LDH induced by mechanochemical processes during friction consumes the friction force between the rubbed surfaces and as a result the friction and the wear is reduced. Thus our results show that the LDH sheets absorbed on the worn surface can prevent direct contact between the friction pairs (surfaces) and decreases the roughness of the worn surface.

Comprehensive Investigation of Various Organophosphate Intercalated CoAl-LDHs As Additives in Polyalphaolefin

“…16,17,19 Transmission electron microscopy (TEM) and X-ray absorption near-edge structure (XANES) spectroscopy characterizations in those studies indicate that the in situ tribofilm constitutes mixed cobalt (Co) oxides. 13,19 However, the tribotests were conducted at room temperature, whereas the engine oil can reach 100 °C or more in practice. 29 Therefore, we tested a series of carbonate-LDHs with different binary cation systems at 100 °C for 1 h. 30 It was found that the CoAl-and CoFe-LDHs achieved outstanding antiwear performance by forming a thick oxide tribofilm.…”

“…Furthermore, the choices of divalent and trivalent cations are numerous, facilitating diverse chemical compositions. Nevertheless, most of the studies in oil lubrication research opted for carbonate-intercalated LDH additives − because carbonate has a strong attraction to the hydroxide layers, which complicates the synthesis procedures. Particularly, an inert atmosphere is commonly required in LDH synthesis involving anions other than carbonate.…”

Influence of Structural Disorders on the Tribological Behavior of Phosphate-Intercalated Layered Double Hydroxide Additives in Polyalphaolefin

“…However, the number of LDH studies in the tribology field is still limited. Zhao et al 23 studied the friction behaviors of CoAl-CO 3 2− -LDHs and concluded that the addition of 0.5 wt % additives significantly reduced the wear size by 26.1% and COF by 22.3% in four-ball and Plint friction tests. 23 Li et al 24 compared the lubrication performance of MgAl-, ZnAl-, and ZnMgAl-LDHs with MoS 2 and graphite.…”

“…Zhao et al 23 studied the friction behaviors of CoAl-CO 3 2− -LDHs and concluded that the addition of 0.5 wt % additives significantly reduced the wear size by 26.1% and COF by 22.3% in four-ball and Plint friction tests. 23 Li et al 24 compared the lubrication performance of MgAl-, ZnAl-, and ZnMgAl-LDHs with MoS 2 and graphite. MgAl-LDHs had the best performance among the three LDHs due to their good thermal stability under severe conditions.…”

Composite Nanoparticles Based on Hydrotalcite as High Performance Lubricant Additives

“…As a typical two-dimensional material, layered double hydroxides (LDH) is composed of charged brucite-like hydroxide layers and charge-balancing exchangeable anions in the interlayer. − The special structural composition and physicochemical properties impart LDH nanoparticles with good tribological properties as lubricant additives, and LDH is promising for next-generation nanoadditives. − While the lubricating property of single LDH nanoparticles is insufficient in practical working conditions, therefore, the study of composite materials based on LDH have become a new research field. Owing to the rich positive charge on the surface, the LDH nanoparticles are prone to absorb the nanoparticles with rich negative charge (such as graphene, graphene oxide, MoS 2 , and so on) to form corresponding composite materials with better lubricating performance …”