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The purpose of this study is to evaluate the potentials of nano-additives in enhancement of oxidation and thermal stability of biolubricants thereby, improving the resistance of dispersed nanolubricants to thermal degradation under elevated temperature.

This study evaluates the oxidation stability and tribological performance of nano-enhanced biolubricants. Graphene and maghemite nanoparticles at 0.1% volume concentration were dispersed into coconut oil. Oxidation stability was analysed using a thermal analyser to understand the effect of nano-additives on thermal degradation of lubricants under increasing temperature. In addition, tribological performance and viscosity of the tested lubricants were evaluated using a four-ball friction tester and viscometer according to American Society for Testing and Materials standards.

The results reveal that the oxidation stability of biolubricants dispersed with nano-additives improves due to delayed thermal degradation. The nano-enhanced biolubricants’ oxidation onset temperature was delayed by 18.75 °C and 37.5 °C, respectively, for maghemite (MGCO) and graphene (XGCO) nanolubricants. This improvement imparts the performance viscosity and tribological performance positively. For graphene-enhanced nanolubricant, 10.4% and 5.6% were reduced, respectively, in coefficient of friction (COF)and wear scar diameter (WSD), whereas 3.43% and 4.3% reduction in COF and WSD, respectively, for maghemite-enhanced nanolubricant compared with coconut oil. The viscosity index of nanolubricants was augmented by 7.36% and 13.85%, respectively, for maghemite and graphene nanolubricants.

The excellent performance of nanolubricants makes them suitable candidate as sustainable lubricants for machining with regard to environmental benefits and energy saving.

The effect of graphene and maghemite nanoparticles on the oxidation stability and tribological performance of biolubricants has been investigated. It is an original work and yet to be published elsewhere.

This paper presents a sustainability assessment model to holistically guide sustainable construction and green retrofitting of affordable housing from the Ghanaian perspective.

A comprehensive review was carried out, which yielded 16 sustainability indicators. Then, a questionnaire survey was conducted among respondents in the Ghanaian housing sector. Forty-seven valid responses were received and analysed using fuzzy synthetic evaluation (FSE) technique.

A four-index model was developed that includes: Housing and Transportation (H + T) index, household-satisfaction index, efficient stakeholder-management index and quality-related index. These indices account for 25.3%, 26.3%, 23.6% and 24.9% of sustainability attainment in affordable housing, respectively. Accordingly, household-satisfaction has the greatest contribution to sustainability attainment in affordable housing.

Due to challenges in obtaining responses to the questionnaire, the study was conducted with relatively small number of responses.

The model serves as a tool that could be used to objectively and comprehensively assess sustainability performance in affordable housing. Besides, it could be used as a baseline to calibrate future projects and for benchmarking success levels of comparable housing projects. Finally, the estimated indices are applicable in decision making for optimum resource allocation for sustainable low-cost housing in the Ghanaian perspective.