A New Magnetic-field-driving Method For Fabricating Ni/epoxy Resin Functionally Graded Materials

Functionally graded materials (FGMs) are emerging as a new class of special materials between heterostructure materials and composite materials. They have been extensively used in many engineering fields with their continuous spatial distribution of components and resulted properties. Based on the distinct difference in magnetic susceptibility between components, two new magnetic-field-driving approaches were developed to prepare Ni/epoxy resin FGMs. Vertical and parallel magnetic-field-driving devices were designed and built to meet the need of experiments. The influences of Ni concentration, magnetic filed velocity and the action times on composition distribution, electrical resistivity, light transmittance and normallized saturation magnetization of Ni/epoxy resin FGMs were studied systematically by means of optical microscope, spectrophotometer, high resistance meter, vibrating sample magnetometer.The results are summarized as follows:The gradient of composition distribution, light transmittance, electrical resistivity and specific saturation magnetization were formed along the field moving direction in samlpes fabricated by vertical magnetic-field-driving method. With increasing Ni content from 5 to 20 wt.%, the composition gradient increased first and then decreased. As the magnetic field velocity increased from 0.25mm/s to 3mm/s, Ni gradient decreased. The composition gradient increased with adding the action times of magnetic field from 1 to 5. The system structure remained unchanged after 5 times of magnetic field action. In addition, the chain-like clusters of Ni were formed, which lead to the anisotropy of electrical resistivity and normalized saturation magnetization. A schematic model was proposed to explain the distribution of particles in gradient magnetic fields.Ni gradient and chain-like clusters were obtained along the field direction in samples prepared by parallel magntic-field-activated method. The composition gradient increased with the increase of Ni contents, and reached the maximum value at Ni= 15 wt.%. With increasing the velocity of magnetic field from 1 to 20mm/s, Ni gradient decreased. The composition gradient increased with adding the action times of magnetic field from 2 to 10. The system structure remained stable after 10 times of magnetic field action.