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