Preparation of nano-zirconium phosphate by freeze-drying method and its tribological properties

In order to explore the influence of freeze-drying process parameters on the size of zirconium phosphate (α-ZrP) nanoparticles during freeze-drying, different process parameters were selected and orthogonal experiments were designed to prepare nano α-ZrP with different particle sizes. The structures of nano α-ZrP are characterized by the field emission scanning electron microscope (SEM), and the tribological properties of nano α-ZrP are studied on a tribometer. The orthogonal experimental results indicated that the order of process parameters affecting the size of nano α-ZrP is freezing method > material tray area > reaction temperature. The freezing method has the greatest influence on the size of nano α-ZrP. The particle size is around 20 nm under vacuum freezing, 40 nm under liquid nitrogen freezing, and 60 nm under refrigerator freezing. The reaction temperature of 98 °C, the material disk area of 80 mm 2 , and vacuum freezing were found to be the optimal process parameters for the preparation of small size nano α-ZrP by freeze-drying. Different amounts of granular nano α-ZrP were added to the base oil; when the addition amount was 2%, the friction coefficient was the smallest, which could be reduced by 34.6%. Friction experiments were conducted on three distinct morphologies of nano α-ZrP (granular, lamellar, and rod); the results show that the friction performance of nano α-ZrP with granular morphology is better than that of the other two crystal morphologies. Graphical abstract