Cleaning Technology of Niobium for Superconducting Materials

Cleaning process was studied by removing the oil with emulsifier solution under the effect of ultrasound and pickling surface with the mixed acid of nitric acid and hydrofluoric acid.Cleaning surface was analyzed by SEM,XPS and corrosion depth.The results show that using emulsifier solution under the effect of ultrasound has a good effect on the ash and oil cleaning,which can create a uniform interface for pickling.The temperature of emulsifier is 40-50 ℃ and frequency of ultrasonic is 20-25 kHz.Cleaing with the mixed acid of nitric acid of 35% and hydrofluoric acid of 10% can achieve good cleaning effect and surface state requirements.The surface chemical structure changes and Nb2O5 dissolves into Nb.Reasonable control of nitric acid and hydrofluoric acid concentration can ensure the cleaning quality and prevent material from absorbing hydrogen.Good washing and drying processes are necessary to ensure the quality.Niobium has strong stability after cleaning.Cleaning fluid characteristics can be characterized by the free fluoride ion,niobium ion and acidity.