Preparation And Properties Of ZnO-Based Powder Materials Based On Laser Ablation

Metal oxide is a typical kind of compound semiconducting material taht is formed bymetal and oxygen usually with ionic bonds. Due to their wide bandgap, high tranperency andhigh carrier mobility, wide applications are expected. The preparation, physical property andnew appilications are also the research focus of meterials science and technology. Laserablation/irradation in liquid is a new method to prepare granular materials, which can produceextreme nonequilibrium conditions on the surface of materials, e.g. superhigh temperature andultrahigh pressure. The extreme nonequilibrium conditions may induce the generation ofmicron/nanomaterials with unique structures and properties. This article studied the influenceof different experimental parameters on morphology, microstructure and optical properties ofthree kinds of typical oxide semiconductor particles by laser ablation/irradiation in liquid. Westudied the formation mechanism of oxide particles with different morphologies and thetribological properties of oxide microspheres as lubricating oil additives were alsoinvestigated. The main results are as follows.1. We studied the influence of different liquid medium and targets on morphology,microstructure and optical properties of prepared ZnO nanoparticles. ZnO nanoparticlesprepared in SDS solution showed regular spherical shape, while that prepared in distilledwater were rod and flake-like. Thereinto, particles prepared using metal Zn target wereZn/ZnO nanoparticles with core-shell structure. Microstructure and optical properties ofprepared particles indicated that the luminescence properties of nanoparticles prepared byZnO ceramic target were better than that prepared by metal Zn target. The green （⁵20nm）and violet（⁴20nm） luminescence were related to defects of Voand Zniin ZnO nanoparticles,respectively.2. The control of morphology and optical properties of three kinds of typical oxidesubmicrometer particles, e.g. ZnO, TiO2and CuO, were realized by laser-induced reshapingmechanism. Based on the principle of surface energy minimization, the surfaces of particlesbegin to melt and transform to sphers when the particles absorb the energy when powderparticles with irregular shapes were used as targets and irradiated by laser. The particlespherizing minimum the particle surface area with release of their surface energy, which is a thermodynamic favorable state. Phtoluminesce property of the prepared ZnO microspheresindicated that defect luminescence was suppressed and indicated the crystal quality wasimproved by laser irradiation.3. The tribological properties of prepared ZnO, TiO₂and CuO submicrometer spheres aslubricating oil additives were studied. Oxide microspheres prepared by laser-induced reshapingmethod can uniformly and stably dispersed in commercial lubricants, and significantly reducethe friction coefficient. Friction coefficient decreased more than50%unerd the optimalconcentration of spherical particles. Antifriction mechanism of oxide microspheres was due totheir molecules bearing and surface mending effects. Besides, we improved the antiwearproperties of ZnO submicrospheres with composite technology of microparticles andnanoparticles. The ZnO/Al₂O₃composite particles exhibit both antifriction and antiwearproperties.