WEB-ресурс научно-практических конференций

K.Phys.-Math. Alontseva D.L.*, Kolesnikova T.A. **

* East Kazakhstan State Technical University ; ** Ust-Kamenogorsk , Kazakhstan

USE OF TRANSMISSION ELECTRON MICROSCOPE FOR TEACHING MATERIAL SCIENCE IN ENGINEERING EDUCATION

Introducing the basics of electronic microscopy in the course of Material Science is the priority task in the context of shifting to training modern experts in the sphere of Physics. This article presents some aspects of a general practical course in Material Science for engineering students. The newly developed course is aimed at teaching students to get images with the help of transmission electronic microscopy and analyze them. The scope of presented experimental operations reflects material science aspects of analyses of metal objects. The course involves the new generation microscopes, as well as the previous models; it is aimed at explaining the operating principles of transmission electronic microscopes and the analytical methods applied to them. It is an inalienable step in any study of finer structure of materials.

In order for a material engineer to be able to develop new materials applied in modern technology he needs detailed knowledge of their structure. For instance, when producing composite materials it is necessary to have quantitative data on their structure specifically at nano level, so that to understand their properties.   Nowadays one of the most reliable experimental methods of structure investigation is electronic microscopy. First, it gives highest spatial resolution when observing images (about 0,1 nm). Second, it allows receiving diffraction images of an object necessary for structural analysis. The better the technical characteristics of electronic microscopes are, the more skills an operator needs to operate them. We developed a rather universal set of operations for material engineers in order to get and analyze images received by means of transmission electronic microscopy imaging.

The suggested approach to teaching ensures autonomous work of students on preparing test samples for investigation, and the study of their structure using high technology equipment. It’s advantageous for students to acquire skills of preparing samples and working on an electronic microscope, as well as understanding of alterations in the sample structure which happen in the process of its preparation and directly in the microscope column when interacting with an electron jet. Modern research methods of studying material properties allow to evaluate properties of given materials with greater reliability, and to suggest techniques for developing them and improving material characteristics.

The scope of tasks reflects specific material science aspects of metal object analyses.   The basics of data processing and physical experiment planning should be included in the Material Science syllabus along with informational technologies as an optional course.

The course of studies in the fundamentals of practical electronic microscopy itself includes the following chapters:

Transmission electronic microscope. Its objectives are: familiarizing students with the equipment, mastering the principal stages of submicroscopic analysis: adapting magnification, light background, dark background, operating a goniometer.

Preparing test objects and finding the invariable of the microscope for estimation of electron-diffraction patterns. It is aimed at: mastering techniques of test sample preparation; carrying out measurement and analysis of the test object imagery, circumferential diffraction pattern analysis.

Preparation of replicates and powder objects . It is designed to master the techniques of preparation of replicates and powder objects, determining the character and quality of information about an object given by means of a replica method.  

Preparing metal foil from bulk material and its investigation . The objective of it is to teach the techniques of preparing metal foils from bulk material, determining diffraction proviso of contrast formation and analysis of dot diffraction patterns.

Dislocation structure properties characterization . The purpose of this is to study dislocation characteristics of substructure with grain and subgrain boundary imaging; and master ways of characterizing subgrain properties and dislocation density.

The ability to correctly plan a physical experiment and analyze its results is a critical and one of the most difficult to learn skills. The specific character of this chief subject requires having many skills of conducting a physical experiment, such as electron microscope investigations. Besides the fact that the methods of these investigations are labor-intensive by themselves, they also include preconditioned preparation of test samples: thinning a bulk sample or preparing an ultra-thin section, surfacing and surface etching, sputtering carbon replicates or tiny hole punching in the foil by means of electrojet polishing, etc. It’s also necessary to carry out preliminary mechanical and thermal treatment of samples, which is rather time-consuming. Therefore it is necessary to use computer technologies at various stages of the course.  

There are two main tendencies of using computer technologies in this field: first, at the experiment problem setting stage for the analysis of data that has been collected at plants or research laboratories over a long period of time; second, when running the equipment to shorten the time of processing experimental data.

Implementation of the first tendency is indispensable in any research study carried out by students. The authors’ experience reveals that statistical processing of experiment data, determining distribution and correlation laws of the data received, using multifactor analysis methods present rather a complex task not only students of Material Science, but for Computer Science students as well. On the whole the planning of an experiment preconditions that students have already acquired such skills, which is not true at times.   We have in mind not students’ computer literacy, but their understanding of the mechanisms and meaning of methods of variation and statistics analysis.

Information technologies applied in the course are invaluable for more precise and faster data processing. They allow a detailed insight into research results, and make the planning of a physical experiment easier.

The use of contemporary equipment for the study of material structure allows for applying the most reliable experimental methods of structure investigation in training qualified experts in the field of material engineering. The practical course in Material Science for engineering students, developed on the basis of the principles of transmission electronic microscope use, provides students with background knowledge and practical skills for analyzing metal object properties and equips them with skills necessary for successful application in their professional field.