Browsing by Author "Krasteva M."

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    METHODOLOGY AND EQUIPMENT FOR RESEARCHING CORROSION CRACKING PROCESSES IN CASTING ALLOYS
    (2024-01-01) Krasteva M.
    Corrosion cracking is the destruction of metal under static stresses and an aggressive environment. Corrosion fatigue is destruction of the metals and the alloys under the impact of cyclic mechanical pressure and aggressive environment simultaneously. Stress corrosion is the least studied and systematized in terms of literature data on the impact of various aggressive environment (type, temperature, and concentration), composition and structure of the material, mode of heat treatment, method of obtaining and cleaning the casting, methodology for determination of corrosion under stress, as well as equipment for carrying out similar studies. The purpose of this paper is to present the methodology and equipment developed for corrosion cracking testing of cast alloys.
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    Study of multiblock polyamide-6/Poly-(isoprene) copolymers by positron annihilation spectroscopy
    (2008-11-10) Bryaskova R.; Mateva R.; Djourelov N.; Krasteva M.
    Positron annihilation lifetime spectroscopy (PALS) has been used to determine the free volume in multiblock polyamide-6/poly-(isoprene) copolymers (PA-6/PI), synthesized via activated anionic bulk copolymerization. The diisocyanate functionalized telechelic PI, blocked with caprolactam (CL) has been used as a commoner and an activator at the same time. The elastic PI block incorporated into the main chain of PA-6 affects the amorphous and crystal phase of the copolymer leading to changing in degree of crystallinity. The positron annihilation lifetime spectroscopy (PAL) and Doppler broadening of annihilation line (DBAL) technique in a set of pure PA-6 and PA-6/PI copolymers with two different compositions have been applied and evaluation of the size of free-volume holes (pores), localized mainly in the disordered regions of the PA-6/PI copolymer by measuring the o-Ps lifetime (τ3) and o-Ps intensity (I3) has been performed. © Versita Warsaw and Springer-Verlag Berlin Heidelberg 2008.