Cold-neutron depth profiling as a research tool for the study of surface oxides on metals

A recent experiment at NIST has demonstrated that neutron depth profiling (NDP) based on the (n, a) reaction could be developed into a tool that could be routinely used for the study of passive oxides on metals. Whereas most metals are not (n, a) active, oxides grown with \ub9\u2077O, the only (n, a) active oxygen isotope, can be observed and tracked by this technique. Problems due to contamination of the samples by boron were encountered, but were shown to be surmountable. For our samples, the NDP facility at NIST, as it exists today, has enough flux and energy resolution to separate the a particles emitted by \ub9\u2077O from those emitted by \ub9\ub0B. Substantial improvement in the data collection rate, easily achievable with arrays of additional detectors, will make NDP a useful tool in the study of passive oxides.Une exp\ue9rience r\ue9cente au NIST a d\ue9montr\ue9 que le profilage en profondeur par neutrons (NDP), bas\ue9 sur la r\ue9action (n, a), peut devenir un outil d\u2019utilisation courante pour \ue9tudier les oxydes passifs \ue0 la surface des m\ue9taux. Alors que la plupart des m\ue9taux n\u2019ont pas d\u2019activit\ue9 (n, a), les oxydes avec \ub9\u2077O, le seul isotope d\u2019oxyg\ue8ne actif (n, a), peuvent \ueatre observ\ue9s et \ue9tudi\ue9s \ue0 l\u2019aide de cette technique. Nous avons eu des probl\ue8mes de contamination des \ue9chantillons par du bore, mais ils se sont av\ue9r\ue9s surmontables. Pour nos \ue9chantillons, le montage NDP au NIST, tel qu\u2019il existe pr\ue9sentement, a un flux et une r\ue9solution en \ue9nergie qui sont suffisants pour isoler les a du \ub9\u2077O de ceux du \ub9\ub0B. Une am\ue9lioration substantielle du taux de collecte des donn\ue9es, facilement atteignable avec des r\ue9seaux additionnels de d\ue9tecteurs, fera de NDP un outil utile dans l\u2019\ue9tude des oxydes passifs.Peer reviewed: YesNRC publication: Ye