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    DISSERTATIONS AND ABSTRACTS OF THESES

      ABSTRACT OF DOCTORAL THESIS -
    DOCTOR OF SCIENCES (HABILITATED)
    Shirinyan A. S.
    The change of the physical and chemical properties of nanomaterials
    in size-dependent first order phase transformations. – Manuscript.
    Dissertation (thesis) for scientific degree of doctor of physical and
    mathematical sciences by speciality 01.04.07 – solid state physics.
    // Taras Shevchenko Kyiv National University of the
    Ministry of Education and Science, Youth and Sport of Ukraine,
    Kyiv, 2012, 368p (36p).
    Change of properties of solid nanomaterials in size-dependent
    first order phase transformations is theoretically substantiated.
    Correlations between the properties of the new nanophases
    and size of nanomaterials are defined.
    Phase diagrams of binary nanosystems are calculated.
    The author shows that solidus and liquidus curves
    do not correlate to thermodynamic equilibrium.
    The scientific definitions of solid state physics regarding
    first order phase transformations with concentration redistribution
    are adapted to nanosystems. The processes of multicomponent
    nanopowder thermal cycling under the first order phase transformation are described.
    We offer the proportion for thermal hysteresis of α-Fe→γ-Fe→α-Fe transformations
    of Fe nanopowders within the cycling temperature interval 800 K-1450 K.
    The possibility of concentration ‘self-saturation’ effect in kinetics
    of phase separation of metastable binary alloy under the constant external conditions is shown.
    The size dependence for potential energy of the interaction between neighbour atoms
    in nanomaterials at zero temperatures and for diffusion coefficients of atoms
    in nanophases is substantiated. The result has been applied for thermodynamic calculations
    and designing diagrams of metallic Bi-Sn and Bi-Pb nanosystems phases.
    The problem of new nanosized phase growth kinetics in а binary diffusion couple
    is solved taking into account the size dependence of the diffusion coefficients.
    It is shown that the growth rate index for the new nanophase layer may be nonmonotonous in time.
    Keywords: thermodynamics, kinetics, phase transformation, size effect, phase diagram,
    thermal hysteresis, self-saturation, atomic interaction, reactive diffusion.

    ABSTRACT OF PH D THESIS - CANDIDATE OF SCIENCES
    Shirinyan A. S.
    Influence of the system size and of concentration gradient
    in the diffusion zone on thermodynamics of nucleation and decomposition.
    – Manuscript. / Dissertation (abstract) for a Ph. D. degree in physics
    and mathematics sciences by speciality 01.04.07. – Solid state physics.
    // Kharkov National Karazin University, Kharkov, 2001, 191p (20p).
    A thermodynamics of multiple nucleation and decomposition in alloys,
    in fine-grained systems and in the binary diffusion couple
    during the reactive diffusion in the initial concentration gradient field is considered.
    A thermodynamics of simultaneous nucleation of many nuclei and of separation
    in amorphous alloy is considered. The quantitative analysis of nucleation of one nucleus
    and decomposition in small isolated inorganic particles is presented.
    It is shown that there exist three possibilities: phase separation,
    prohibition of decomposition and metastable state of alloy.
    Problem is solved taking into account a compositional depletion
    of the parent phase. The detailed analysis of the competitive nucleation
    of two intermediate phases and separation
    in small particle has been made. The possibility of formation and total stabilization
    of metastable Al3Li1 phase instead of stable Al1Li1 phase
    in small particles of Al-5-50 ат.% Li alloys is demonstrated.
    Nucleation of intermediate phase during the reactive diffusion
    in the binary diffusion couple due to fluctuation,
    which takes into account the optimized redistribution
    of composition in the diffusion zone, is considered.
    Analysis of all modes (longitudinal, transversal, polymorphous)
    of nucleation in binary diffusion couple has been modified.
    For all modes of nucleation formulas of dependencies
    of the Gibbs free energy changing from volume, 
    form and concentration gradient have been obtained.
    Keywords:
    nucleus, depletion, Gibbs free energy, size effect, competitive separation,
    phase diagram, gradient of concentration, nucleation modes.


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