碳纳米管在铀的热电离质谱测量中的应用研究

Application of Carbon Nanotubes in the Measurement of Uranium by TIMS

为了研究不同规格碳纳米管对U+发射的影响,以碳纳米管(CNTs)作为铀测量的发射剂,通过考察它对离子流信号强度、稳定性以及235 U/238 U丰度比测量结果的影响,研究了碳纳米管对铀同位素丰度测量的作用,并对比了石墨、蔗糖以及不同规格碳纳米管的离子发射性能。结果表明,碳纳米管作为发射剂可显著提高U+产额、离子流信号稳定性以及测量精度,其中CNTs-3的效果相对最优,可使U+产额提高3倍以上。以CNTs-3作为发射剂,铀涂样量25ng时,235 U/238 U相对标准偏差小于0.2%(n=18);涂样量5ng时,235 U/238 U相对标准偏差为0.5%(n=18)。

Carbon nanotubes （CNTs） were used as the ion emission promoter for increasing the ionization yield of uranium for the measurement of uranium isotopes by thermal ionization mass spectrometry （TIMS）.The emission effect of the carbon nanotubes was studied by researching the change of ion intensity,signal stability and measurement precision.A comparative study of the emission performances of graphite,sucrose and three kinds of carbon nanotubes with different diameters was carried out.The results suggest that carbon nanotubes loaded with the uranium sample can significantly improve U＋ yield,signal stability and measurement precision.The ion emission capacity of CNTs-3 is the best among all the carbon sources investigated in this work.The ion yield of U＋ is increased more than three times when CNTs-3 as ion emission promoter.Samples with 25 ng and 5 ng uranium are measured using CNTs-3 as ion emission promoter.The results show that the relative standard deviations （RSD） of 235U/238U is about 0.2% and 0.5% （n=18）,respectively.