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Issue 20, 2017
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Assessment of PGAA capability for low-level measurements of H in Ti alloys

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Abstract

The accuracy of low-level hydrogen measurements with prompt gamma-ray activation analysis (PGAA) depends on identifying and accounting for all background H signals, including interfering signals. At the cold-neutron (CN)PGAA facility at the NIST Center for Neutron Research, the sources of background H signals were investigated in the context of titanium-based matrices containing low-levels of H (<300 mg H per kg Ti) with the measurements of prepared standards (mixtures of polyvinyl chloride and titanium oxide) and Ti alloy (Ti6Al4V) samples. The sensitivity ratio, defined as the ratio of the H signal to the Ti signal per unit mass ratio of H in Ti, was determined (1) with the measurements of prepared standards and (2) based on partial gamma-ray production cross sections and full-energy detection efficiencies. The resulting calibrations from these two approaches agreed within experimental uncertainty. A series of Ti alloy NIST Standard Reference Materials (SRMs) previously certified for the H content (SRMs 2452, 2453, 2453a, 2454) were used as test cases, with the mass fractions determined based on the sensitivity ratios derived from method 1 and method 2, respectively. The results agreed with the certified values within experimental uncertainties, validating the analysis performed on the new instrument with newly-prepared standards at low H mass fractions (method 1), and with the standard-independent analysis (method 2). Various sample mounting improvements were made to lower the background H signal. Spectral interferences near the H peak were identified as potential sources of bias and as a limiting factor in the detection limit of H in Ti alloy samples.

Graphical abstract: Assessment of PGAA capability for low-level measurements of H in Ti alloys

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Publication details

The article was received on 06 Aug 2017, accepted on 29 Aug 2017 and first published on 07 Sep 2017


Article type: Paper
DOI: 10.1039/C7AN01308F
Citation: Analyst, 2017,142, 3822-3829
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    Assessment of PGAA capability for low-level measurements of H in Ti alloys

    D. Turkoglu, H. Chen-Mayer, R. Paul and R. Zeisler, Analyst, 2017, 142, 3822
    DOI: 10.1039/C7AN01308F

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