Papers by Keyword: SNMS

Abstract: Abstract. It is shown, by the combination of SNMS, (Secondary Neutral Mass Spectrometry), XRD, XPS and APT (Atom Probe Technique) that the growth of the Cu₃Si crystalline layer at 408 K between the amorphous Si and nanocrystalline Cu thin films follows a linear law and the shifts of the Cu₃Si/Cu and Cu₃Si/a-Si interfaces approximately equally contributed to the growth of this phase. It is also illustrated that the Si atoms diffuse fast into the grain boundaries of the nanocrystalline Cu, leading to Si segregation. Both the SNMS and APT results indicate that even during the deposition of Cu on the amorphous Si an intermixed region is formed at the interface. This region easily transforms into a homogeneous Cu₃Si crystalline reaction layer subsequently which further grows following apparently an interface controlled linear kinetics. Similar experiments performed in Co/a-Si system to study the formation and growth kinetics of the intermetallic phase. However, interestingly, homogenous formation of the new phase at the Co/a-Si interface was not always observed.

Abstract: Isothermal oxidation of two g-TiAl-based intermetallic alloys: Ti48Al and Ti46Al8Nb alloys was studied in synthetic air at 1073-1223 K for up to 240 hrs. Mass change per unit area for the oxidized samples followed approximately the parabolic rate law. The k_p values for the studied temperature interval were in the range from 7.2×10^-13 to 1.8×10^-11 g²cm^-4s^-1. The activation energy for oxidation of Ti48Al alloy in air at 1073-1223 K was E_a = 165±12 kJ/mol. Niobium addition to Ti48Al alloy in the amount of 8% increased its oxidation resistance. Structure and chemical composition of the oxidation products, and morphology of the oxidized samples were investigated using XRD, SEM-EDS, and TEM. The oxide scales formed on Ti48Al and Ti46Al8Nb alloys were well adherent to the metallic substrates and exhibited a multilayer structure. Depending on the oxidation temperature and the alloy composition, the scale consisted of variable amounts of TiO₂ and Al₂O₃. Additionally TiN, and niobium rich particles were also identified in the appropriate oxide scale. To understand the growth mechanism of oxide scale formed on Ti46Al8Nb alloy, two stage oxidation experiment was performed using ¹⁶O₂/¹⁸O₂, followed by SNMS and TEM-EDS. Particular attention was paid to the use of TEM in order to precisely characterize the reaction products on the Ti46Al8Nb alloy.