DBHP-Functionalized ZnO Nanoparticles with Improved Antioxidant Properties as Lubricant Additives

Abstract

In this article, 3-(3,5-di-tert-butyl-4-hydroxyphenyl) propionic acid (DBHP)-functionalized ZnO (DBHP−ZnO) nanoparticles were synthesized by decomposing the organometallic precursor Zn(DBHP) 2 under alkaline conditions. This in situ surface modification method can induce small-sized ZnO nanoparticles (5 nm) and form strong linkage between DBHP and ZnO nanoparticles. DBHP as an organic compound hindered phenol antioxidant that not only improved the dispersion stability of the prepared DBHP−ZnO nanoparticles in the lubrication oil but also scavenged free radicals produced during the oxidation process of oil. Compared with DBHP, the thermal stability of the prepared composite antioxidant was greatly enhanced by introducing inorganic ZnO nanoparticles, which was proved by the results of the thermogravimetric analysis test. A rotary oxygen bomb test, pressurized differential scanning calorimetry, and free-radical-scavenging method all showed that DBHP−ZnO nanoparticles had better antioxidant properties than DBHP under high temperature in the base oil of di-iso-octylsebacate (DIOS). The activation energy of the oxidation process was used to analyze this result by the model-free methods, including the Flynn−Wall−Ozawa method and the Kissinger equation. The calculated results showed that DIOS containing DBHP−ZnO nanoparticles have the lowest reaction constant and the longest half-life period compared to those of individual DBHP and ZnO nanoparticles, which is attributed to the combined action of the organic−inorganic composites. Besides, DBHP−ZnO nanoparticles as the additive are able to improve the antiwear ability of DIOS to some extent. Therefore, the as-prepared DBHP−ZnO nanoparticles with desired dispersibility as well as better thermal stability and antioxidant ability than DBHP in the DIOS base oil could be a potential high-performance nanocomposite additive for a synthetic lubricant base oil like DIOS.

Robust Interfacial Tribofilms by Borate- and Polymer-Coated ZnO Nanoparticles Leading to Improved Wear Protection under a Boundary Lubrication Regime

“…Among these additives, zinc oxide (ZnO) nanoparticles have received considerable interest reflecting their nontoxicity; high surface energy; and unique antioxidant, electrical, and thermal conductivity properties. Several researchers have attributed the tribological properties of ZnO nanoparticles to their size and concentration in the base oils. ,,− ZnO nanoparticles can improve antiwear performance by creating a lubricant film and reduce the friction of moving surfaces. Kalyani et al examined the effect of the particle size of ZnO nanoparticles on the tribological behavior of paraffin oil and, using SEM–EDX elemental analysis of worn surfaces, confirmed the adsorption of ZnO nanoadditives on the rubbing surfaces .…”

Preparation of a Chitosan-Lead Composite Carbon Aerogel and Its Catalytic Thermal Decomposition Performance on Ammonium Perchlorate

“…The FWO and KAS methods were used to calculate the activation energies of AP and AP+CS-Pb-3.5 during the thermal decomposition process in relation to the conversion rate, and the relationship curves are shown in Figure . Figure a–d shows the experimentally measured ln­(β i ) versus 1000/ T α and ln­(β i / T α 2 ) versus 1000/ T α with AP and AP+CS-Pb-3.5 (10%), respectively. ,,− The activation energies of their regression curves and their corresponding R 2 values in the range of 0.1–0.9 are shown in Table . It can be seen that the activation energies of pure AP and AP+CS-Pb-3.5 at the same degree of conversion are dramatically different, indicating that the catalyst has the ability to reduce the activation energy of pure AP.…”

Tuning Autoxidation and Friction of Mineral Oil by Fullerene Cluster Properties

“…One of the main limitations of lubricant oils is their autoxidation with air, a reaction that is catalyzed by ion metals and is accelerated when oils are heated or exposed to light. − This reaction starts with the rupture of a carbon–hydrogen bond, creating free radicals of carbon and hydrogen. Then, the carbon radicals easily react with dissolved oxygen creating peroxy-radicals that later react with another hydrocarbon molecule, yielding another carbon radical and an oxidized molecule, and these hydrocarbon molecules may continue to oxidize through time. − To diminish autoxidation diverse nanomaterials such as extracts from rice husk and sawdust, zeolites, ZnO, and carbon nanostructures − have been studied.…”