Preparation And Structure Control Of Ceramic-based Composite Materials By EPD

Ceramic-based composite materials refers to the composite materials made of ceramics and other inorganic,metal or organic materials.This material retains the advantages of high ceramic hardness,corrosion resistance,high temperature resistance and good wear resistance.Meanwhile,it combines with the good qualities of the other materials,and play an important role on overcoming the brittleness of ceramics,increasing its toughness and strength,providing new features and so on.The material can form a more versatile composite materials,which would be greatly applied in the aerospace industry,nuclear energy,electronics,optics,chemistry,electromagnetics,biomedical and other fields.Electrophoretic deposition is a kind of ceramic molding technology,which can control the deposition position of particles accurately through the electrode and process parameters.It can realize the structural regulation of single-phase ceramic materials,so as the control of the composition and structure of the composite material,and even the preparation of gradient materials.Electrophoretic deposition has its great advantages on manufacturing the composite materials,but there still exist urgently technical problems need to be solved.It is the key to solve these technical problems by recognizing the effect of the properties of the suspension on the electrophoretic deposition process.In this paper,we start from solving the key problem of electrophoretic depositing the composite materials in composite phase,which is based on the study of the electrophoretic deposition factors in the single phase system.So that we can control the structure of composite materials.The main research and results are following:1.The mechanism of the single-phase oxide suspension properties on electrophoretic deposition was studied.The effects of the conductivity of the suspension,the zeta potential of the charged particles and the particle size on the deposition quality,the deposition current density,the shrinkage rate and the density of the bulk after sintering were studied.The results show that the higher the conductivity,the higher the ion solubility in the suspension,so that the double layer of the particles is thinned and the zeta potential decreases.An excessive high conductivity will make the particles tend to agglomeration settlement,which is not conducive to deposition.However,the low conductivity of the suspension is likely to result in the protonation of the solvent,resulting in a large number of solvents move to depositing electrode,resulting in greatly increased liquid content of the deposition.Under the action of the deposition voltage,the double layer of the particles in the suspension is thinned and deformed.The larger the voltage,the easier it is to deposit.The degree of compactness of particles during the deposition process is determined by the ease of particle deposition and the size of the particles.The tightness of the particles will affect the ion conducting pathways,thereby determining the change of resistance in deposition and ultimately effecting depositing effective voltage.2.The effects of suspension properties on the electrophoretic deposition of composite phase oxides were studied,which is based on the study of single phase oxides deposition.Alumina and zirconia can form uniformly distributed composite suspension.The conductivity of the composite suspension,the zeta potential,the size of the particle and the deposition are positively correlated with their mass ratio.The higher the proportion of zirconium oxide has,the more it deposits.Zirconia dominates the free conductance of the ion transport pathway,and controls the deposition resistance and the effective deposition voltage,so that the deposition yield of zirconia is significantly decreased with the deposition time.The higher the voltage and the zirconia content are,the higher the initial deposition rate is.But the later deposition rate is almost independent of their mass ratio.At a high voltage,zirconia has the effect of shrinkage on the ion transport pathway formed by alumina again.Based on the results of the mechanism of single/composite deposition,the alumina-zirconia multi-layer gradient composite ceramics and continuous gradient composite ceramics with uniform component distribution were prepared by optimizing the conductivity and particle surface properties of the composite suspension.But in the non-uniformly dispersed suspension,the orientation deposition occurs,and the agglomerated Al2O3 affects the deposition of ZrO2,which leads to a banded deposition of zirconia.