14 MeV中性子放射化分析法によるアルミニウム末中の酸素の定量

抄録

Oxygen in aluminum dust produced by the gas atomizing method was determined by means of 14 MeV neutron activation followed by nondestructive γ-ray counting. An external standard method was adopted to improve reproducibility and accuracy of the analytical results. The analytical process was simplified by using this method.
The γ-rays of ¹⁶N was measured with the energy range of 4.5∼8.0 MeV. With this energy range, measurements were free from interferences due to simultaneously produced radioactive nuclides from matrix aluminum except ²⁴Na. Satisfactory results were obtained by measuring ¹⁶N counts twice with an appropriate decay interval and subtracting the second counts as a back ground from the first counts to remove interference caused by ²⁴Na. Increase of apparent ¹⁶N counts caused by contribution of ²⁴Na was almost agreed with the calculated result.
Oxygen concentration in aluminum dust larger than 270 mesh size was almost constant at 1700 weight ppm, increasing rapidly with the decrease of particle size, and reached about 3000 weight ppm for the fraction of 325∼400 mesh which occupied about 30% of the whole amount.
Almost all of the oxygen in aluminum dust is thus supposed to be present as oxide because the oxygen content is much higher than that estimated from both solid soluble and surface adsorption.
The time required for the analysis of one sample was 150 s.