A New Magnetic-field-driving Method For Fabricating ZrO₂-Co Functionally Graded Materials

Functionally graded materials (FGMs) are a class of novel materials. The composition, microstructure and properties of these materials vary continuously and smoothly. They have been extensively used in many engineering field, where a material is required to perform different functions at different locations. Based on the distinct difference in magnetic susceptibility between components, new magnetic-field-driving method was developed to prepare ZrO2-Co FGMs. The magnetic-field-driving device was designed and built to meet the need of experiments. The influences of mixed slurry composition (including solid content, Co concentration and particle size) and magnetic field strength, magnetic field velocity and the action times on composition distribution, microhardness and normallized saturation magnetization of ZrO2-Co FGMs were studied systematically by means of optical microscope, microhardness tester and vibrating sample magnetometer.The results are summarized as follows:The gradient of microstructure, composition distribution and properties were formed along the field moving direction in samples prepared by moving magnetic-field-driving method. As the solid content in suspension increased, the density of FGMs increased, but the composition gradient decreased. High density of the samples with low solid content can be obtained by vacuum filtration processing. With increasing Ni content from 5 to 20 wt.%, the composition gradient formed as well as microhardness and normallized saturation magnetization, the composition gradient increased with increasing of particle diameter ratio between Co and ZrO2.With increasing of magnetic field strength increased, the composition gradient of Co was formed and increased. As the magnetic field velocity increased from 0.25mm/s to 3mm/s, Ni gradient decreased. However, little gradient was formed as the velocity was up to 3mm/s. The composition gradient increased with adding the action times of magnetic field from 1 to 15. A schematic model was proposed to explain the distribution of particles in gradient magnetic fields.