Characterization of ferroboron alloys by simultaneously quantifying Fe and B mass fractions and isotopic compositions of B by external particle induced gamma-ray emission method

Abstract

The mass fractions of Fe and B as well as the isotopic compositions of B were non-destructively and simultaneously quantified in synthetically prepared ferroboron (Fe–B) alloys by external particle induced gamma ray emission (PIGE) method using a proton beam of 3.5 MeV. Powder samples were wrapped in a thin Mylar foil and kept in front of the target flange in the atmosphere for irradiation using an external PIGE set up. Characteristic prompt gamma rays of ⁵⁶Fe(p,p′γ)⁵⁶Fe (847 keV), ¹⁰B(p,αγ)¹⁰B (429 keV), ¹⁰B(p,p′γ)¹⁰B (718 keV) and ¹¹B(p,p′γ)¹¹B (2125 keV) nuclear reactions were measured together with external beam current normalizers of 136 keV of ¹⁸¹Ta(p,p′γ)¹⁸¹Ta (beam extraction/window material) and 2313 keV of ¹⁴N(p,p′γ)¹⁴N (atmospheric nitrogen) using an HPGe detector system. Boron mass fractions determined using 429 keV gives better precision than those determined using 718 and 2125 keV with 136 keV of Ta as a current normalizer after irradiating the samples only for 10–15 minutes owing to a high proton-induced thick target gamma ray yield of 429 keV at 3.5 MeV. Isotopic compositions of B determined with simple peak area ratios of 429 and 718 keV of ¹⁰B and 2125 keV of ¹¹B are 0.248 (4) and 0.246 (2), respectively, which correspond to 19.8 atom% of ¹⁰B, i.e. natural sample. Mass fractions of Fe, which is the major constituent of Fe–B alloy, were also determined simultaneously with B. The advantage of this external PIGE method is the analysis of direct powder samples with minimal sample preparation providing high sample throughput and faster results with adequate accuracy and precision.