The Laboratory for Transmission Electron Microscopy (TEM) in the Institute of Metal Science “Acad. A. Balevski” was founded in 1967. The first transmission electron microscope of the lab, that has been in use for almost 40 years, was JEM 7A of the company JEOL, Japan. In 2006 it was replaced by a new microscope EM-1011 SAP10 of the same company with the following basic technical characteristics:
- accelerating voltage HV= 40-100 кV
- resolution in point – 0,45 nm, in lattice – 0,20nm
- magnification from 50х to 500000х
The specimens preparation is performed using a BUEHLER cutting machine ISOMET 1000 and JEOL vacuum evaporator JEE 4B.
The transmission electron microscope is a unique facility to obtain reliable information about the morphology and structure of solid-state materials, especially about the micro- and nano-sized components of the crystalline structure. These capabilities of the microscope are due to the specifics of the illumination source – a beam of accelerated electrons. It passes through the examined substance and produvces image of high resolution – less than a nanometer (for comparison the resolution of the light metallographic microscope is 1 micrometer). The main reasons for the image contrast that arises during electron beam passing through the target are the interaction of accelerated electrons with the target atoms as well as the diffraction processes caused by the periodicity of crystal target’s lattice.
The TEM method has a wide application in the field of material science. It Is applied to solve basic problems related to the new materials characterization, especially the components of their structure on micro- and nano-level and the structure-propetties relations. One of the main tasks studied by TEM concerns the solid state phase transformations and their products, phase initiation and growth. The TEM is the only instrument that allows the visualization of the crystal lattice imperfections, foe example vacancy complexes, dislocations, stacking faults, dislocation interactions and dislocation configurations, substructure, interfaces and grain boundaries. Many of the TEM applications are connected with the material behavior under external effects and their underlay in the structure components and processes. All these studies help to define more precisely the parameters of their future application of materials in real conditions.
The investigations that have been carried out in TEM laboratory were aimed to solve specific problems connected with the research work in a wide field of material science. The staff of the laboratory gained rich experience in:
- characterization of the micro- and nano-structure of new materials, emphasizing on phase composition, alloying, production and processing conditions
- study of the initiation and growth of new phases, phase transformations and interactions in metals and alloys
- investigation of the influence of external effects (temperature, loading mode, plastic deformation, environment) on the structure characteristics and behavior of materials
- investigation of the crystal structure imperfections and their behavior under the influence of external effects
- analysis of the dislocation structure and its development and stability under thermal and mechanical effects; formation of dislocation substructure
- investigation of the rapid quenching effect on the structure; identification of the amorphous and microcrystalline state in new metal materials
- study of the crystallization processes in amorphous alloys
- investigation of the effect of aggressive environments on the structure components of alloys
- monitoring of the irradiation damages of the reactor pressure vessels metal during NPP Kozloduy operation
- failure analysis in parts and components of real constructions
The TEM Laboratory of IMS works in active collaboration with related educational institutions in the country, like Technical University-Sofia, Technical University -Varna, University for Chemical Technology and Metallurgy-Sofia), many of the research institutes of BAS and with Technical University “St.St. Kiril i Metodi”- Skopje – Macedonia.
The most important results of the investigations performed by the staff of TEM laboratory are published in two monographs, more than 120 research publications, more than 20 reports under contracts with research and industry organizations, including the National Research Fund at the Ministry of Education. A part of the investigations are carried out in the course of preparation of 5 Doctor of Sciences theses, 25 Doctor’s theses and more than 10 graduation theses.
