Advancement of Triboactivity of Nanolamellar Ni-Mn-Based Bimetallic-Organic Frameworks by Molybdenum-Doped Bismuth Vanadate Nanorods

To pave the way for highly tribologically efficient 2D materials, a Ni-Mn-based bimetallic-organic framework (NMF) was synthesized ultrasonically. Considering further advancement of its activity, hydrothermally synthesized BiVO4 (BV)/Mo-doped bismuth vanadate (MBV) nanorods were introduced to obtain nanohybrids, MBV/NMF. The TEM, HR-SEM, and HR-TEM investigations of the hybrid (MBV/NMF) divulge that Mo-doped BiVO4 nanorods were spread over NMF nanosheets and strengthened them. Using ASTM D4172 and ASTM D5183 standard tests, the tribological performances of well-characterized nanomaterials, BV, MBV, NMF, and MBV/NMF, were assessed in paraffin oil (PO) at the optimal concentration, 0.1% w/v on a four-ball tester. The mean wear scar diameter (MWD) value for base oil PO shows a % reduction: BV (22%), MBV (27%), NMF (33%), and MBV/NMF (42%). The % reduction in average coefficient of friction (COF) value of base lube follows a similar trend to that of MWD: BV (20%), MBV (25%), NMF (33%), and MBV/NMF(60%). The tribological data such as MWD, COF, and seizure load revealed significantly better activity of NMF nanosheets than the nanorods, possibly owing to weak van der Waals forces existing amid the lamellae. Certainly, the molybdenum doping has increased the activity of BiVO4 nanorods. The hybrid MBV/NMF exhibited highly advanced activity because of noncovalent synergistic interactions between nanosheets and nanorods. Investigations of the wear track via EDX and XPS studies indicate that the generated tribofilm comprises lubricious metal oxides: MoO3, Bi2O3, V2O5, MnO2, Mn2O3, NiO, Ni2O3, and metallic alloy (Ni-Fe), which prevented metal-metal contact between sliding surfaces and thus synergetically improved the lubricity. Tribological findings of the wear track were validated by SEM and AFM. A plausible lubrication mechanism has been demonstrated.