10B/11B isotopic ratio and atomic composition of boron carbide: Determination by proton induced γ-ray emission and proton elastic backscattering spectrometry

The B-10/B-11 isotopic ratio and the atomic composition of boron carbide, an important non-metallic ceramic, have been determined non-destructively by the particle induced y-ray emission (PIGS) and elastic backscattering spectrometry (EBS) techniques with proton beams. The analysis has been performed on powder as well as sintered ceramics containing boron in natural or B-10 enriched composition. The PIGS technique, performed at a 4.0-4.2 MeV proton energy, utilizes the B-10(p,alpha gamma)Be-7, B-10(p,p'gamma)B-10 and B-11(p, p'gamma)B-11 nuclear reactions for (a) the isotopic analysis of boron and (b) the determination of total boron, and the C-13(p,p'gamma)C-13 nuclear reaction for the determination of carbon. The irradiation conditions were optimized by determining the thick targets yields of prompt gamma-rays, characteristic of these reactions, in the 3.0-4.2 MeV proton energy range. The quantitative analysis was performed by comparison with standards taking into account the attenuation of gamma-rays in the specimens. The uncertainty in the determination of the B-10/B-11 isotopic ratio and the B/C atomic ratio is about 2% and about 5% respectively. The analysis by EBS, on the other hand, involves the B-10(p,p)B-10, B-11(p,p)B-11 and 12C(p,p)12C elastic scatterings at the 2.0 MeV proton energy. This method too yields satisfactory results. Between the two, PIGS is the method of choice for bulk analysis while EBS is useful in discerning compositional variations in surface regions.