LABORATORY
X-RAY DIFFRACTION AND MAGNETIC RESONANCE

HEAD: Assoc.Prof. Malina Baeva, Ph.D.
tel: 7144-275; e-mail: malina@issp.bas.bg

TOTAL STAFF: 6
RESEARCH SCIENTISTS: 4
Assoc. Prof. L. Pramatarova, Ph.D.;
Assist. Prof. K. Kabassanov;
Assist. Prof. A. Boianova;
P. Botev, physicist;
E. Pecheva, Ph.D. student

RESEARCH ACTIVITIES:

(1) INVESTIGATIONS OF POLYCRYSTALLINE LAYERS
    The conditions for obtaining of АІІВVІ solid solutions in presence of gettering agent are optimized. The dependence of layer properties on the original components ratio in heterogeneous system is established. The energy spectrum parameters of the local levels for current carriers in the layers are defined from the results of measured thermo stimulated conductivity (TSC), lux-amper characteristics, photoluminescence spectra and temperature dependences of photocurrent and dark current. A model of the Cr₂O₃ action as a gettering agent in the investigated CdSe_xTe_1-x is created.

(2) X-RAY STRUCTURAL INVESTIGATIONS OF SINGLE CRYSTALS AND POLYCRYSTALS
    X-ray topography of single crystals: the topographic patterns of single crystals of CdTe and BGO single crystals. (Bi₁₂GeO₂₀ ) bismuth germanat single crystals
    Phase composition of polycrystals: variations of phase composition in the chrome-nickel and chrome-manganese Fe alloys are investigated. For the synthesized alloy concentrations supposed phase composition is calculated and the predicted by the Schaeffler diagram positions of the alloys in it are obtained. It is established that in Mn presence the chromium moves the alloys from the purely austenite area to the mixture of two-phases area. On the basis of the experimental results the empirical dependences Phase composition-Concentration are obtained and the coefficients of stability for the face centered cubic lattices are defined.
    X-ray structure photographs are made with the aim to obtain the crystallographic data of different types of materials, as for example: by Debye powder X-ray patterns the powder probes of series of samples submitted by FF-Sofia University are identified as one modification of the magnesium silicates; the X-ray back-scattering of the mixtures clinoptilolyte+liquid crystal are made; identification of the renal stone type of colleagues who appeared as stone formers -5 analysis.

(3) DEVELOPMENT OF AN IN-VITRO SYSTEM FOR STUDYING THE PROCESS OF BIOMINERALIZATION
    The current project for development of controllable in-vitro system for growth of hydroxyapatite (HA) layers on solid state substrates with leader Assoc. Prof. Dr L. Pramatarova is related to national and international important topics, such as Improving Human Potential and Quality of life, Nanostructures and Nanotechnologies of the 6 FP of the EC. The progress in understanding the process of biomineralization, particularly the HA growth, as well as the interactions between an implanted in the living body material and different cells, is attained through in-vitro experiments.
    As a result of the scientific activity an experimental set-up for layer growth in simulated body fluid on modified solid substrates is created. The modification of silicon, stainless steel and silica glass substrates is attained by ion implantation of Ca and P ions through a mask, by nanostructuring of CdSe in thin layers of SiOx, as well as by growth of porous and nanocrystalline Si.
    Hydroxyapatite layers are grown by a novel method: by simultaneous laser-liquid-solid interaction in cooperation with "Pulslight" Ltd. The results from the experiments show that the developed in-vitro system could find application for obtaining HA coatings for medical implants because the structure and the chemistry of the growon HA resemble those of the biological apatite.
    A patent on the theme is awarded with a gold medal on the 11-th exhibition for intellectual property East-West-Euro-Intellect, Sofia, 20-24 June, 2003.

1. M. Baeva, A. Beskrovnyi, E. Jadrowski, S. Danilkin, "Influence of Cr content on the phase composition of the Fe-(11 to 23)Cr-12Mn-0.6N steels", Journal of Materials Science Letters, 22 (2003) 1787-1789.
2. K. Kabassanov, Z. Nenova, E. Konstantinova-Kabassanova, "Photoelectric properties of A₂B₆ photoresistive Arrays", Comptes rendus de l`Academie bulgare des Sciences, 56, No.7 (2003) 23-28.
3. M. Baeva-Neova, A. I. Beskrovnyi and E. L. Jadrowski, "Influence of Chrome and Nickel on the microstructure of high nitrogrn steels", Proceedings of the Fifth General Conference of the Balkan Physical Union BPU-5, Vrnjachka Banja, Serbia and Montanegro, Serbian Physical Society, Belgrade, 2003, Editors: S. Jokic, I. Milosevic, A. Balaz, Z. Nikolic, pp. 607-610.
4. M. Baeva-Neova, A. Boianova, "Determination of Renal Stones Type by X-ray diffraction", Proceedings of the Fifth General Conference of the Balkan Physical Union BPU-5, Vrnjachka Banja, Serbia and Montanegro, Serbian Physical Society, Belgrade, 2003, Editors: S. Jokic, I. Milosevic, A. Balaz, Z. Nikolic, pp. 1667-1670.
5. L. Pramatarova, E. Pecheva, D. Nesheva, Z. Levi, Z. Aneva, R. Pramatarova, U. Bismayer, T. Petrov, Study of modified solid surfaces by nanostructured CdSe in SiOx thin films, physica status solidi c, #3, (2003) pp.1070-1074
6. E. Pecheva, L. Pramatarova, M. F. Maitz, M. T. Pham, Study of the calcium phosphate layer grown on AISI 316 stainless steel from simulated body fluid, Journal of Materials Science: Materials in Electronics 14 (2003) pp.775-776
7. E. Pecheva, L. Pramatarova, M. F. Maitz, M. T. Pham, A. Kondyuirin, Kinetics of hydroxyapatite deposition on solid substrates modified by sequential dual implantation of Ca and P ions. Part I. FTIR and Raman spectroscopy study, submitted at the European Vacuum Congress, 23-26 June 2003, Berlin, Germany
8. E. Pecheva, L. Pramatarova, M. F. Maitz, M. T. Pham, A. Kondyuirin, Kinetics of hydroxyapatite deposition on solid substrates modified by sequential dual implantation of Ca and P ions. Part II. Morphological, composition and structure study, submitted at the European Vacuum Congress, 23-26 June 2003, Berlin, Germany
9. L. Pramatarova, E. Pecheva, M. F. Maitz, M. T. Pham, A. Kondyurin, Growth of hydroxyapatite layers on patterned by ion implantation solid surfaces, submitted at the European Materials Research Society (E-MRS) 2003 Fall Meeting, 15-19 September 2003, Warsaw, Poland
10. E. Pecheva, L. Pramatarova, M. F. Maitz, M. T. Pham, A. Kondyurin, Extracellular matrix used in-vitro model system for hydroxyapatite formation, submitted at the the European Materials Research Society (E-MRS) 2003 Fall Meeting, 15-19 September 2003, Warsaw, Poland
11. L. Pramatarova, E. Pecheva, M. F. Maitz, M. T. Pham, A. Kondyurin, Ion beam patterning of solid surfaces for hydroxyapatite deposition, submitted at the 13^th International School on Vacuum, Electron and Ion Technologies, 15-19 September 2003, Varna, Bulgaria
12. L. Pramatarova, E. Pecheva, T. Petrov, A. Kondyurin, R. Pramatarova, N. Minkovski, Ion beam and laser processing for hydroxyapatite formation, submitted at VEIT, Varna, Bulgaria
13. L. Pramatarova, E. Pecheva, D. Dimova-Malinovska, R. Pramatarova, U. Bismayer, M. Kamenova, T. Petrov, N. Minkovski, Porous silicon as a substrate for hydroxyapatite growth, submitted at VEIT, Varna, Bulgaria
14. L. Pramatarova, E. Pecheva, T. Petrov, N. Minkovski, A. Kondyurin, R. Pramatarova, Enhancement of hydroxyapatite formation by laser-liquid-solid interaction, submitted at ILLA/LTL International Conference and Symposium, 27 September-1 October 2003, Smolyan, Bulgaria
15. L. Pramatarova, E. Pecheva, T. Petrov, N. Minkovski, A. Kondyurin, R. Pramatarova, Ion beam modified surfaces as substrates for hydroxyapatite growth induced by laser-liquid-solid interaction, submitted at ILLA/LTL, Smolyan, Bulgaria
16. L. Pramatarova, E. Pecheva, M. F. Maitz, M. T. Pham, A. Kondyurin, R. Pramatarova, Analysis of hydroxyapatite films grown on whole-surface ion implanted substrates for studying the process of biomineralization, submitted at the 5^th Workshop on nanoscience and nanotechnology, 19-21 November, Sofia, Bulgaria /Instanbul, Turkey

1. Project No Л-1213/2002: Development of an in-vitro system for layer growth from functional solutions on modified solid substrates.
   Financed by the Bulgarian Academy of Sciences:
   1. Physical properties of pure АІІВVI layers and solid solutions obtained in the presence of gettering agent.
   2. X-ray structural investigations of polycrystalline substances.

1. BAS, Bulgaria - Joint Institute of Nuclear Research, Dubna, Russia: Neutron investigations of crystal structure of Fe-based alloys.
2. BAS, Bulgaria - HAS, Hungary, project No 8: Physical and chemical processes on surfaces and thin layers of condensed matter.
3. BAS, Bulgaria - LAS, Latvia: Study of the laser-liquid-solid interation in in-vitro system for crystal growth from functional solutions on a substrate.

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