|
The superconducting material is a material having a zero resistance characteristics and Meisner (Meissner) effect . The superconducting material in the normal state is an insulator or a semiconductor, exhibits its zero- resistance characteristic in the low temperature state . The superconducting material is divided into low-temperature superconducting materials and high-temperature superconducting materials , 40K is the cut-off point . The high-temperature superconductor YBCO transition temperature is reached first 90K, provides a broad prospect for the practical use of the high-temperature superconducting . This study were used in the dry and wet sol - gel method , and improved on this basis , to take a different preparation process , the O2 content , sintering , annealing temperature , and other conditions of the superconducting the nature of the impact . First, the use of different oxygen flow to prepare sintered YBCO bulk and characterization XRD other means . The results show that the oxygen flow 35-40ml/min best, the oxygen content is 0, the resulting sample was completely superconducting phase ; the oxygen content is too high , the cleavage peak enough complete . Second, the change of the length of the different nature of the sample of the sintering time , sintering time is too short will cause incomplete sintering , appears only non - superconducting phase . Principle , the longer the sintering time , but due to the limitations of the reaction cycle , we generally use a preferred sintering time of 3 days ; different level and the speed of the annealing temperature , the different nature of the sample obtained . Experiments to explore the optimal annealing temperature of 960 ℃, annealing rate of 10 ° C / min , the XRD diagram 2θ main peak splitting 32.5 . Cause some defects in the crystal structure of the superconductor can be improved when unimpeded current carrying capacity of the nanorods into superconducting structure superconductor current will increase by 10 - fold . The papers of ZnO Nanorods on the reaction temperature , reaction time , ultrasound and other influencing factors studied . In the initial reaction , the use of the low - temperature ice bath compared to room temperature reaction of the diameter and length of the nano-rods are small, and the diameter of the product obtained from the low - temperature ice bath ZnO nanorods diameter 100nm, about 1 μ m length , without using an ice bath 1 μ m, a length of 10 μ m; less amount of surface active agent , after the reaction , the resulting length of the rod is also smaller in the experimental sample , the surfactant content is 5%, the aspect ratio of the top ; the reflux time around 7h good uniform morphology and size of the product obtained in ultrasonic method than ultrasound has not been taken in the reaction process .
|