Papers by Author: Maciej Krystian

Abstract: Recent investigations on palladium hydride (Pd-H) showed, for the first time, evidence of formation of vacancy-hydrogen (Vac-H) clusters during Severe Plastic Deformation (SPD) effected by High Pressure Torsion (HPT). Vacancy concentrations produced in Pd-H by this method are extraordinarily high. DSC-scans show that the thermal stability range of vacancies is extended by about 150K due to trapping of hydrogen leading to the formation of vacancy-hydrogen clusters. Recent experiments give evidence that the mobility of the H atoms and/or the vacancies is conditional for the formation of Vac-H clusters during HPT. Results furthermore indicate defect stabilization by hydrogen trapping not only for vacancy-type defects but also for dislocations and grain boundaries.

Abstract: Pure palladium (99.95%) was hydrogenated, subsequently deformed by High Pressure Torsion (HPT) and analyzed by differential scanning calorimetry (DSC). For comparison some hydrogen-free HPT processed samples were also investigated. In case of the hydrogenated HPT Pd, the concentration of single / double vacancies is noticeably higher. The importance of hydrogen for the formation and stabilization of vacancy type defects and dislocations is discussed.

Abstract: Nanocrystallization is known to yield several improvements for the storage and uptake rate of hydrogen in solids. Usually this process is achieved by ball milling to produce a nanopowders. However, handling of these powders is risky and difficult, and there is also a high risk of introducing impurities into the storage material. In this situation materials processed by Severe Plastic Deformation (SPD) yield several advantages: (i) the materials are produced in bulk shape with 100% density; (ii) the introduction of impurities is minimized, (iii) in addition to additional grain boundaries, many dislocations and particularly vacancies are generated which may further improve the hydrogen storage capacity and kinetics.