Experimental Study on Chemical Behaviors of Non-Metal Impurities in Pb, Pb-Bi and Pb-Li by Temperature Programmed Desorption Mass Spectrometer Analysis
The chemical behaviors of non-metal impurities such as O2, H2, N2, H2O, CO2 and CO in lead (Pb) metal, lead-bismuth (Pb-Bi) alloy and lead-lithium (Pb-Li) alloys were experimentally investigated by means of temperature programmed desorption mass spectrometer (TPD-MS) analysis. Desorption of H2O and CO2 from the Pb metal and the Pb-Bi alloy was clearly detected by TPD-MS analysis. However, desorption of H2O and CO2 from the Pb-Li alloys was much less than that from the Pb metal and the Pb-Bi alloy, since these molecules are chemically unstable and react with Li in the Pb-Li alloys. Then, oxygen and hydrogen must be dissolved in Pb-Li alloys as they form the chemical compounds of Li (i.e., Li2O, LiOH and LiH). Large desorption of hydrogen from solid Pb-Li alloys by their heating was detected. The possible mechanism for the large desorption of hydrogen from the Pb-Li alloys is based on the decomposition of LiH and Pb-Li-H at high temperature. The chemical behaviors of the non-metal impurities in the Pb-Li alloys was modeled based on the thermodynamic stability. The methodologies for the fabrication of high-purity Pb-Li alloys and the control of the impurity condition are discussed.
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