Preparation And Low Temperature Properties Of AlN/Epoxy Resin Composite For Superconducting Magnet Impregnation

In order to prevent superconducting tapes from deviating from the original position due to the Lorentz force fluctuations,epoxy resin is required to impregnate the superconducting magnets and its performance is directly related to the operation stability of superconducting magnets.Aimed at improving the properties of epoxy resin for superconducting magnets impregnation,epoxy resin was modified by aluminum nitride(AIN)powder with high thermal conductivity and good insulating property in this thesis.AIN surface was modified by silane coupling agent to convert the hydrophilic surface of AIN into organophilic surface.Thus the agglomeration of the particles in the epoxy resin system and the rapid viscosity of the polymer could be avoided,and the wettability of the epoxy resin to the fillers was also improved.In order to explore the influence of the curing process of AlN/epoxy composites on the current carrying capability of superconducting magnets,the influence of constant temperature(?)and acting time(hour)on the critical current of superconducting tapes was studied.The study found that the critical current of the superconducting tapes began to decrease when the acting time was 2h and the constant temperature exceeded 140?.The critical current of the superconducting tapes dropped by 20%after being heated at 220? for 2h.At the same time,the superconducting tape at a certain temperature for a long time also caused decrease of critical current;for instance,the critical current decreases by 7%after being heated at 160? for 6h.It can be seen that high temperature and excessive heating time will cause the degradation of the current carrying capacity of the superconducting tapes.The thermal conductivity of AlN/epoxy composites at low temperature was tested by steady state method.The results showed that the thermal conductivity of epoxy resin increased with AIN content.When AIN content was added up to 7wt%,the thermal conductivity increased by nearly 30%.With AIN content,the increasing rate of the low-temperature thermal conductivity was gradually accelerated.The tensile properties of AlN/epoxy composites were investigated.The results showed that the composites exhibited brittle fracture behavior at low temperature.Tensile strength increases first and then decreases with AIN content at room temperature,while the tensile strength increases with AIN content at low temperature.In general,the tensile strength at low temperature is higher.The electrical insulation properties of AlN/epoxy composites at low temperature were studied.It was found that the influence of AIN content on electrical insulation properties was not significant.The addition of AIN powder only resulted in a slight decrease in breakdown strength,up to a maximum decline of 9.4%.And the effect of impregnation on current carrying capacity of the short superconducting tape sample was negligible.