Degree Name

Doctor of Philosophy


School of Civil, Mining and Environmental Engineering


This research delves into the exploration of layered double hydroxides (LDHs) as potential lubricant additives, aiming to understand their tribological potential and effectiveness in reducing friction and wear. While LDHs have been extensively studied in catalysis, absorbents, and biomedical applications, their tribological potential remains least explored. Some studies suggest LDHs as potential lubricant additives, but tribochemical mechanisms and the effects of specific anions and cations in tribofilm formation are not fully understood. Incorporating LDH lamellar structures with beneficial intercalated species holds a strong promise for significant friction and wear reduction. Although phosphate-based additives demonstrated excellent friction and wear performance, the effect of phosphate-intercalated LDH additives on tribological behaviors has not been fully understood. Therefore, the thesis focused on an in-depth exploration of intercalated phosphate anions, including inorganic phosphates (hydrogen phosphate, orthophosphate, pyrophosphate, and hexametaphosphate) and phosphate esters (methyl phosphate, isopropyl phosphate, phenyl phosphate, and dodecyl phosphate), in LDHs as lubricant additives in oil media.

The research employed a systematic approach, utilizing various methods for the comprehensive evaluation of LDH lubricant additives. Tribological performance tests were conducted under different conditions, including oil media and specific additive concentrations. Advanced characterization techniques such as X-ray diffraction (XRD), scanning transmission electron microscopy (STEM), electron energy loss spectroscopy (EELS), and Raman spectroscopy, nanomechanical testings were employed to analyze the structure, composition, and mechanisms underlying the observed tribological behaviors.

FoR codes (2008)




Unless otherwise indicated, the views expressed in this thesis are those of the author and do not necessarily represent the views of the University of Wollongong.