The Study On Preparation Of YBCO And The Microstructure Properties Of YBCO/Cu Composites

The c/a numerical value of YBCO crystal cell parameters is large. The structureof YBCO is similar to graphite because of the layered structure，so YBCO has goodsolid self-lubricating performance on tribology. YBCO was added to the copper matrixcomposites to improve the friction and wear properties of the material withoutreducing the electrical conductivity. Therefore, it can be widely used in the aerospace,electronic electrician, etc. Due to the high price of YBCO, in this article YBCOpowder was prepared by oxalate coprecipitation process. The YBCO/Cu compositeswas prepared by vacuum hot pressing method. The preparation process of YBCO andthe structure and properties of YBCO/Cu composite materials were studiedsystematically.Differential thermal analyses (DTA) was used to characterize the reaction in theprocess and the phase transformation was analyzed by XRD. The morphology ofpowder was characterized by SEM and TEM. The thermodynamic data was Used tocalculate the PH and ion concentration in the solution. The influence on the size andphase of particle at different calcinations temperature was investigated during thegeneration process of YBCO. The effect of dispersant on the morphology of powderwas analyzed. The influence of solution PH on the precipitation rate was Studied andthe process parameters were optimized. When the calcination temperature is900℃,the crystalline of the powder is good, but the particles of the powder is uneven and theagglomeration is serious. The study found that the agglomeration of YBCO powdercould be solved effectively by adding polyethylene glycol dispersant. The particles ofthe powder prepared are homogeneous and the average size is about40nm.Thermodynamic calculation shows that when the concentration of oxalic acid is0.1mol/L, the optimal PH of the solution is1.71-6.8and it is good match with theexperimental results.YBCO/Cu composite materials were prepared by hot pressing method and cold isostatic pressing method; The density was measured by Archimedes principle and themicrohardness was tested by MH-3Micro-hardness tester; The D60K digital metalconductivity measuring instrument was used to measure the conductivity; The wearresistance was tested by friction wear testing machine; Microstructure and grindingcrack morphology was analyzed by scanning electron microscopy and XRD.Microstructure was analyzed by high-resolution transmission electron microscopy(TEM); The effects of the technological parameters variable and the mass fraction ofYBCO on microstructure and properties was studied systematically. The influence ofload and YBCO doping amount on friction coefficient, wear rate and the wearmechanism was analyzedThe YBCO/Cu composites prepared by vacuum hot pressing is better than thatprepared by isostatic pressing sintering. The microstructure of composites is densifiedand distributed homogeneously. The comprehensive performance of the composites isthe best when the content of YBCO is3%. The friction coefficient and wear rate firstlyincreases and then decreases with the increase of load. The wear mechanisms aremainly adhesive wear and abrasive wear in the early wear process and in the middleprocess the wear mechanism are mainly abrasive wear. At the last the wearmechanisms become adhesive wear and fatigue wear.