New:

PLRF 19 code for fitting of positron lifetime - binaries are available for download.

Grants solved nowadays in our group

  • Interface controlled properties of micro/nanocrystalline materials for advanced structural applications, biodegradable implants and hydrogen storage
    The Czech Science Foundation
    project P108/12/G043
    Advanced micro/nanocrystalline (mc/nc) materials promise to become key building blocks in future technologies, where they must feature enhanced performance at extremes of stress, temperature or pressure. In this respect, innovative and multidisciplinary basic research that elucidates the fundamentals of how materials behave in extreme environments is required. The purpose is to advance the state-of-the-art of mc/nc materials by developing new metal-based structures through architectural control at appropriate microstructural scale and their characterization by complementary methods including positron annihilation spectroscopy, 3D electron/ion tomography and energy ltered electron microscopy. These techniques will be shared by all participants and combined with traditional techniques to produce breakthroughs needed for future applications. The objectives are severe plastic deformation of dicult-to-work alloys, powder metallurgy, hydrogen storage, in situ nanomechanical testing of small-scale systems, biodegradable alloys and grain boundary pinning by in situ nanoparticles.
  • Investigation of defects in icosahedral phases in Mg-alloys
    The Czech Science Foundation
    project P108/10/0648
    Quasicrystals poses a unique structure with a lack of translational periodicity. Recently phases with icosahedral structure have been found in some Mg-alloys. It is believed that quasicrystalline phase is associated with a special type of defects not existing in other phases. Detailed characterization these defects in selected Mg alloys will be performed. Two kinds of defects will be examined: (i) defects inside the icosahedral phase, and (ii) misfit defects at precipitate/matrix interfaces. In the second part of project, severe plastic deformation will be applied to achieve a fine dispersion of quasicrystals in Mg matrix. Positron annihilation spectroscopy (PAS) will be used as a principal technique for defect studies. PAS is a well established non-destructive technique with a high sensitivity to defects and atomic scale resolution. In the proposed project PAS will be combined with TEM, metallography, X-ray diffraction, electrical resistometry, and hardness measurements. It is expected that results obtained in the project elucidate nature of defects associated with icosahedral phases and their thermal stability. Knowledge about these defects is important not only for understanding the formation of quasicrystalline structure, but for development of Mg-alloys.
  • Investigation of point defects in ZnO and their interaction with hydrogen and nitrogen
    The Czech Science Foundation
    project P108/11/0958
    Complex investigations of point defects in ZnO are proposed in the present project. Positron annihilation spectroscopy (PAS) including also variable energy PAS using slow positron beam will be used as a principal technique for defect studies. State–of–art ab-initio theoretical calculations will be employed for interpretation of PAS data. Defects in ZnO single crystals will be compared with those in epitaxial and nanocrystalline ZnO thin films. Defects studies will be combined with electrical (temperature-dependent Hall effect, deep level transient spectroscopy) and optical (photoluminescence, optical transmission) measurements in order to find a link between predominant defect configurations and specific electrical and optical properties of ZnO samples. Moreover, in the present project we intend to investigate interaction of hydrogen and nitrogen with point defects in ZnO and influence hydrogen and nitrogen on electrical and optical properties. A new UHV chamber for on-line sputtering of ZnO films will be constructed and connected to slow positron beam. This novel setup enables to perform variable energy PAS investigations of thin ZnO films in-situ during film deposition. It gives us an exclusive possibility to investigate formation of defects and incorporation of impurities into ZnO lattice during film growth.
  • Effect of substitutional elements and grain boundaries on properties of nanocrystalline zirconia-based materials
    The Czech Science Foundation
    project P108/11/1396
    We propose a systematic experimental and theoretical microstructure investigation of a variety of zirconia-based nanomaterials, ranging from the nanopowders towards the nanoceramics produced by sintering nanopowders. The project focus on small-sized defects, grain boundaries and nanopores. Pure zirconia, and a variety of binary as well as ternary zirconia-based systems in m-, t- or c-phases are involved: yttria-stabilized zirconia (YSZ), YSZ doped with Cr, Fe, Mn and some rare earth elements. In addition, a study of t- and c-ZrO2 stabilized with calcia and magnesia is also planned. Positron annihilation spectroscopy is considerd as the base experimental technique which will be combined with TEM, XRD and XPS measurements. The data obtained within the project will contribute to explanation and understanding of the materiál properties on a microscopic level and to tailoring these materials according to the requirements of specific applications.
  • Effects of cores and boundaries of nanograins on structural and physical properties of ball milled and mechanically alloyed iron-based materials
    The Czech Science Foundation
    project P108/11/1350
    The topic of proposed project is to deepen the assessment of interplay between structure and properties of nano-powders prepared by ball milling and mechanical alloying. The original approach will be based on systematic investigations of the structure of nano-grain boundaries and cores. The main attention will be devoted to formation of defects in grain surfaces and to influence of various gases (O2, N2, H2, Ar) and/or milling components on the structure of boundaries and cores of nanograins in a close relation to the properties of final iron-based materials. The combination of microstructure-sensitive Mössbauer spectroscopy and defect-sensitive positron annihilation spectroscopy supported by other experimental methods, e.g. TEM, HREM, (HR)SEM, XRD, DSC, and magnetic measurements guarantees to obtain novel and valuable information. The subsequent annealing and monitoring the changes of structural and physical properties will contribute to extension of the obtained results and to prediction of modifications of the prepared materials aimed at optimization of their magnetic behavior.
  • Effect of hydrogen-defects interaction on multiplication of defects in severely plastically deformed palladium
    The Ministry of Schools, Youths and Sports of the Czech Republic
    project LH12173
    1. Preparation of severely plastically deformed (SPD) palladium-hydrogen (Pd-H) alloys with different H concentrations by means of cold rolling and high pressure torsion (HPT);
    2. Characterization of microstructures of the as-prepared SPD Pd-H alloys by using XRD, SEM, optical microscopy and TEM
    3. Measurements on initial chemical potential of H of the as-prepared SPD Pd-H alloys, where H will be firstly uncharged from the alloys before the measurements, by using electromotive force (EMF) method. In the measurements, H will act as a probe for defects in qualitatively identifying the defects densities.
    4. Quantitative characterization of defects densities, including vacancy concentration and dislocation density, of the as-prepared SPD Pd-H alloys with different H concentrations by means of positron annihilation spectroscopy
    5. Investigations on interactions between defects and H atoms by means of coincidence Doppler broadening spectroscopy (CDBS)
    6. Combining the results of parts 1)-5), effect of H on multiplication of defects in SPD Pd will be illuminated and the corresponding theoretical analyses will be carried out through calculations, modeling, etc.