Positron Studies of Defects in Nitrogen and Carbon Implanted Titanium

Abstract

ABSTRACTModification of materials by ion beams creates defects and defect formation processes. The implantation of nitrogen into titanium influences the hydrogen content in this metal. Hydrogen accumulation enhances hydrogenations in the implanted region. This effect may have important consequences, because excessive hydrogen accumulation generally leads to precipitating hydrids in the matrix lattice and the metal undergoes degradation of its mechanical properties. Many studies have shown that defects in metals trap light gas atoms like H or He which are solved or implanted in the sample. Therefore, the decoration of defects with these atoms is a method to trace defect concentrations and to study the trapping and detrapping mechanism. Mobile defects can be trapped at implanted atoms, at inhomogeneities or at inner surfaces like grain boundaries or interfaces of different phases. Using the slow positron beam technique the traps for hydrogen attributed to vacancy-type defects have been investigated in cp-Ti implanted with nitrogen or carbon.The concentration of hydrogen has been detected by the 15N profiling technique (1H(15N,αγ)12C). The nitrogen and carbon content were measured by 15N(1H,αγ)12C and 13C(p,γ)14N reaction, respectively.