The way to identify the microstructure of ceramic materials


G01N1/28 - INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES (separating components of materials in general B01D, B01J, B03, B07; apparatus fully provided for in a single other subclass, see the relevant subclass, e.g. B01L; measuring or testing processes other than immunoassay, involving enzymes or micro-organisms C12M, C12Q; investigation of foundation soil in situE02D0001000000; monitoring or diagnostic devices for exhaust-gas treatment apparatus F01N0011000000; sensing humidity changes for compensating measurements of other variables or for compensating readings of instruments for variations in humidity, seeG01D; or the relevant subclass for the variable measuredtesting or determining the properties of structures G01M; measuring or investigating electric or magnetic properties of materials G01R; systems in general for determining distance, velocity or presence by use of propagation effects, e.g. Doppler effect, propagation time, of reflected or reradiated radio waves, analogous arrangements using other waves G01S; determining sensitivity, graininess, or density of photographic materials G03C0005020000; testing component parts of nuclear reactors G21C0017000000)

 

Usage: to determine the distribution of grain size in the ceramic materials. The inventive method is that on the sample surface of the ceramic material forming the joint, the surface of the thin section and polished to a 10-12 grade purity, irradiated 1-10 pulses of the electron beam with electron energy of 15-30 Kev, pulse duration 30-40 μs and a current density in the beam 40-50 A/cm2spend the visualization of the pattern of the surface microrelief of the cut, which is judged on the grain size. The technical result - the simplification of the analysis, time-saving, more environmentally friendly way. 4 Il.

The invention relates to the field of measuring and control technology and can be used to determine the distribution of grain size in the ceramic materials.

The closest adopted for the prototype, is a way of revealing the microstructure of ceramic materials. (Levin, B. E., Tretyakov, Y. D., Leuk L. M. Physico-chemical bases of obtaining, properties and applications of ferrites. - M.: Metallurgy. 1979, 472 C.). According to the method on the sample surface of the ceramic material forming the thin section, polished surface lifeshirt using an optical microscope picture of the surface microrelief scratch which is judged on the size of the grains in ceramics, i.e., receive information about the microstructure of the ceramic material.

The disadvantage of this method is the complexity of the composition of provide the Etchant for the particular type of ceramic material, the duration of the etching process, and also used as a component of provide the Etchant dangerous for the environment and human health of chemicals, i.e., its ecologicall.

The objective of the invention is to simplify the analysis, reducing time and improving its environmental performance.

The solution to this problem is proposed to implement a way to identify the microstructure of ceramic materials, which consists in the fact that, just as in the prototype, on the sample surface of the ceramic material forming the thin section, polished surface cut to 10-12 grade purity. Unlike the prototype after polishing the surface of the thin section is irradiated 1-10 pulses of the electron beam with electron energy of 15-30 Kev, pulse duration 30-40 μs and a current density in the beam 40-50 A/cm2. This is followed by a visualization of the pattern of the surface microrelief sections.

A significant decrease in time consumption is achieved by reducing the processing time ceramic surface necessary for you what I and the absence of decomposition products of the ceramic material during its processing.

The range of variation of the parameters of a pulse of electrons determined experimentally. They are selected in such a manner that the instantaneous heating of a thin surface layer of a thin section to a temperature exceeding the melting temperature of the processed ceramics. However due to the smallness time of exposure to the electron temperature of the sample volume varies slightly. On the conducted numerical estimates of the temperature on the surface at the moment of impact on ceramics pulse of the electron beam with such characteristics can reach 4000 K. the melting point of most ceramic materials does not exceed 2500 K. this effect on ceramics is an intensive short-term evaporation of the ceramic material from the irradiated surface.

Due to significant differences in the properties of the material volume of the grains and grain boundaries, the rate of evaporation of ceramics in these different areas. As a result, in the plane of the cut erosion of ceramics in the grain boundary and in the grain volume is at a different depth within the depth of the thin layer of ceramic heated due to exposure to pulsed electron irradiation. As a consequence, a hundred the microscope. The range of 1-10 number of pulses of electrons sufficient to obtain a qualitative picture of the grain boundaries is chosen experimentally. Increasing the number of pulses exceeding the maximum specified in the interval, leads to a noticeable deterioration of image quality thin section surfaces due to the increased erosion of the surface of the ceramic grains. A decrease in the electron energy below 15 Kev or decrease the pulse duration of less than 30 μs reduces the efficiency of heating the surface layer of ceramics, which leads to the necessity to increase the number of pulses, and this, in turn, leads to an increase in the thickness of the heated layer of ceramics. The result is the alignment of evaporation of the ceramic material in the areas of grain boundaries and the volume of the grains, which does not allow to distinguish between the grain boundaries when conducting a visual image of the surface of the thin section. The increase in energy of the electrons above 30 Kev or increasing the pulse width of more than 40 μs leads to local overheating of the surface layer of ceramics, the equalization of the rate of evaporation of the material of ceramics in various areas and the deterioration of the picture surface when rendering. The decrease in current density electric is nisene or increase the energy of the electrons of the limiting values of the working interval, respectively.

In Fig.1 shows a micrograph of the surface of the thin section of sample lithium-titanium ferrite with the surface 10 of the class.

In Fig.2 shows the micrograph of the surface of the thin section of sample lithium-titanium ferrite after surgery chemical etching.

In Fig.3 shows a micrograph of the surface of the thin section of sample lithium-titanium ferrite after surgery, irradiation with one pulse of the electron beam.

In Fig.4 shows a micrograph of the surface of the thin section of sample lithium-titanium ferrite after surgery radiation 10 pulses of the electron beam.

The proposed method is as follows.

As the study material was used lithium-titanium ferrite. For this type of ceramic materials are particularly difficult to find the chemical composition of provide the Etchant and modes etching, to allow visualization of crystal boundaries. It was made in a single technological cycle three samples (sample No. 1, sample No. 2 and sample No. 3) lithium-titanium ferrite, which was in the form of tablets with a diameter of 12 mm and thickness of 2 mm, One side of each sample was subjected to polishing to 10th grade purity. In Fig.1 presents microflo surgery polishing is not visible. Then the sample No. 1 was, according to the prototype method, subjected to chemical etching. As provide the Etchant used was a water solution of hydrofluoric acid. The concentration of the solution, the temperature during the etching and the etching time were determined by experiment in advance of such test samples were respectively 20%, 360 To 35 minutes. Sample No. 2 and sample No. 3 in turn was placed in a vacuum chamber and subjected to pulsed electron irradiation surface. each of the samples at a residual pressure in the vacuum chamber 2·10-4mm RT. Art. as the source of electrons used plasma cathode. For sample No. 2, the irradiation was carried out by one pulse of the electron beam. The parameters of the electron beam were as follows: duration of 30 μs, the diameter of the electron beam 16 mm, accelerating voltage 15 kV, beam current pulse 80 A. the current Density of electrons in the plane of arrangement of the image when it was 40 A/cm2. For sample No. 3, the irradiation spent 10 pulses of the electron beam. The parameters of the electron beam were as follows: duration of 40 μs, the diameter of the electron beam 16 mm, accelerating voltage of 30 kV, a beam current pulse of 100 A. the current Density of the electrons in the plane respectueuse treatment used an optical microscope MIM-7. Micrograph of the surface of the thin section of sample lithium-titanium ferrite after surgery chemical etching (sample No. 1) and irradiation pulse of electrons (sample No. 2 and sample No. 3) shown in Fig.2, figs.3 and Fig.4, respectively. All photos were taken at the same scale. From the comparison of the micrographs shows that the image obtained by the proposed method allows to determine the grain size of the ceramic material with a precision comparable with the method of the prototype. Thus, the processing of micrographs of several fragments of the surface of thin sections of samples No. 1 and No. 2 gave the same value of average grain size of 12 μm for each of the samples. From a consideration of the micrograph shown in Fig.4, it is seen that for irradiation conditions specified for sample No. 3, there is a noticeable deterioration in the quality of a visual image of the grain boundaries on the surface of the thin section, which suggests that the excess of the specified maximum values for the number of pulses of electrons, the pulse duration, the electron energy and current density in the beam will lead to further deterioration of the picture and is therefore inadvisable.

Claims

The way to identify microstructural cut, Polish the surface of the cut to 10-12 grade purity, spend the visualization of the pattern of the surface microrelief of the cut, which is judged on the grain size, wherein after polishing the surface of the thin section of the sample is irradiated 1-10 pulses of the electron beam with electron energy of 15-30 Kev, pulse duration 30-40 μs and a current density in the beam 40-50 A/cm2.



 

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1 cl, 1 dwg

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