GOST 25849-83
GOST 25849−83 (ST SEV 3623−82) Powder metal. Method of determination of particle shape
GOST 25849−83
(ST CMEA 3623−82)
Group B59
STATE STANDARD OF THE USSR
POWDER METAL
Method of determination of particle shape
Metal powders. The method of the determination of particle shape
AXTU 1790
Valid from 01.01.84
to 01.01.89*
________________
* Expiration removed
Protocol N 3−93 Interstate
Council for standardization, Metrology and
certification (I & C N 5−6, 1993).
— Note the CODE.
DEVELOPED by the Academy of Sciences of the Ukrainian SSR
PERFORMERS
V. N. Klimenko, O. S. Nichiporenko. O. A. Balitskaya, N. G. Chaikin, A. E. Kushchevsky, L. D. Bernatsky
INTRODUCED by the Academy of Sciences of the Ukrainian SSR
Academician G. E. Pukhov
APPROVED AND put INTO EFFECT by Decision of the USSR State Committee for standards from 1 July 1983, N 2899
This standard specifies a microscopic method for determination of particle shape of metal powders.
The method is based on determining the amount of projection of the particles under the microscope and subsequent calculation of form factors.
The standard fully complies ST SEV 3623−82.
1. SAMPLING METHOD
1.1. The selection and preparation of samples is carried out according to GOST 23148−78*.
_________________
* On the territory of the Russian Federation GOST 23148−98. — Note the CODE.
2. EQUIPMENT, MATERIALS
Optical or electron microscopes that allow observation in transmitted or reflected radiation.
Magnification of optical microscope should be selected depending on the size of the measured particles, while it should not exceed 1000 times the aperture size of the lens. Used to measure the condenser needs to have the aperture, not smaller, than the lens with which it is applied. For measuring particle size of 1 micron requires an increase in 1400. To measure particles less than 1 µm using an electron microscope.
The automatic analyzer has a module «form-separator».
Counter odinnadtsatikilometrovy (for a leukocyte count of blood).
The technical rectified ethyl alcohol according to GOST 18300−72.
Distilled water GOST 6709−72.
Salt according to GOST 13830−68*.
__________________
On the territory of the Russian Federation GOST R 51574−2000. — Note the CODE.
Coal graphitized according to normative-technical documentation.
Measuring according to GOST 427−75.
Dropper according to GOST 9876−73 or pipette medical.
Subject glasses for micropreparations according to GOST 9284−75.
Cover glasses for micropreparations according to GOST 6672−75.
Paper blotting according to GOST 6246−71 or filter laboratory according to GOST 12026−76.
Medical absorbent cotton wool GOST 5556−81.
The dispersing medium should meet the following requirements:
should not join with the powder particles in the interaction, which can lead to a change in their shape (dissolution, chemical reaction, etc.);
don’t have to have a high volatility;
should be well wetted powder particles;
should not distort the microscopic image.
The composition and properties of the dispersion liquids according to GOST 22662−77.
To consolidate the particles with immersion lenses used film-forming quick-drying 4% solution of collodion in amylacetate.
3. PREPARATION FOR MEASUREMENT
3.1. The sample powder prepare drug — monolayer of particles on a substrate obtained by dispersing powder in the dispersion liquid.
3.2. For viewing under an optical microscope, the preparation is prepared as follows:
the sample for testing weight 2−7 g was mixed thoroughly on a glass tile, pack strip length 7−8cm and divide it into 7 or 8 approximately equal parts. Odd part is discarded and an odd mix and re-cut the same way. The operation is repeated to obtain a sample weight of 0.5−1 g. Then transferred on the tip of a glass rod a small quantity of powder on a glass slide, add 1−2 drops of the dispersion liquid, evenly distribute the mixture with a glass rod on the glass, place the cover glass and gently press on it to avoid the release of large particles outside of the glass. Excess fluid is removed with absorbent paper.
If before cutting the test samples the powder must disaglomirated, desagglomeration indicate in the normative-technical documentation for the particular powder.
3.3. Preparation of replicas of the powders to measure the dimensions of the projections of the particles when using an electronic transmission microscope: a small amount of powder taken from the sample with a thin needle is applied to a fresh chip of salt, and then dropping 1−2 drops of ethyl alcohol on the powder, RUB it evenly with a glass rod over the surface of the chip. After drying, the surface of the salt powder is sprayed in the coal film. For the best quality replica give a shaded chrome. Needle cut the tape into squares of 2to 3 mm and at an angle gently lower the salt in distilled water film up to a film of powder detached from the substrate and floated. Plastic stick carry pieces of tape on the solvent and leave on the surface until the powder is completely dissolved. Thus, the powder particles should be from the bottom of the film. After dissolution of the powder transfer stick pieces of carbon film three times consecutively in a Cup of distilled water for cleaning solvent. Then catch the film and examined under a microscope.
3.4. For measurements using the electronic scanning microscope prepared drug: 2−3 mg of powder taken from the sample, apply a thin layer to the adhesive backing. The substrate is fixed on the object table of the microscope, dried and metallized by coating the gold layer with a thickness of 10 nm. Coated drugs under microscope.
3.5. The sample are prepared two drugs and compare them under a microscope. If the particles are roughly the same size, the measurement is performed on one of them, otherwise, repeat the preparation of microscopic drug.
4. MEASUREMENTS
4.1. The monitoring object is the projection of the particle from the position of greatest stability — the image on the screen of the electron microscope, on the screen or in the eyepiece of the optical microscope in the photos.
4.2. To describe particle shape using the shape factors representing the relationship:
— the maximum linear dimension of the projection of the particle () to its minimum size (
);
— the distance between tangents to the extreme points of the projections parallel to the direction of movement of the drug () to the chord dividing the projected area of the particle into two equal parts and parallel to the direction of movement of a drug (
),
— the perimeter of the projection of the particles () to the area of its projection (
).
4.3. When you manually define dimension ,
,
,
and their relationship is
/
or
/
, klassificeret form factors in the form of frequency distributions. The automatic analysis determines the weighted average of the form factors:
/
,
/and
4.4. Factors /
are used to characterize the degree of neravnomernosti particles.
The factors /
and
/
.
4.5. Dimensions of projections of particles in the field of view of the drug measured in millimeters or micrometers. When this operation of measurement is repeated for incrementally increasing the number of projections as long as the further increase in the number of measured projection of the measured factor will not change by more than 5%.
Measure the projection of non-agglomerated particles. The agglomerates are excluded from the measurement by the operator or by using special devices in automatic analysers.
Form factor is defined as the maximum of the frequency distribution.
4.6. Measurements of the projections of the particles by hand.
4.6.1. The particle sizes measured during continuous movement of the drug or when monitoring individual fields of view. In the first case, the drug is moved in one direction, and I think all the particles in accordance with clause
4.6.2. If the powder contains particles in a large range of sizes and that, due to insufficient depth of field of the lens of the microscope does not allow to obtain sharp image at the same time for all particles, small and large particles are observed and measured at different magnifications.
At low magnification allows for larger particles, large — small particles.
The results of the measurements at different magnifications respectively recalculated in accordance with clause 4.8. All measurements carried out at three magnifications or less.
4.6.3. Allowed to in sight was not more than 150 particles. The distance between the particles should be at least as large as the larger of the adjacent interconnected particles.
4.6.4. Measurement of particles is carried out in the field of view bounded by rectangle or circle with the marked diameter.
A particle is considered to belong to this field if it is on one of the halves of the field boundaries. For example, if the field of view is limited to the rectangle, then consider the particles inside it, on the left vertical and upper horizontal sides, at the intersection of these sides, and on the other end of one of them. The other parts do not.
If the field of view is restricted, then consider all the particles inside it, and all particles located on one semicircle and one end of the carried-out diameter (see drawing ,
).
The scheme of accounting of the particles during the measurements
,
— separate fields of view; and
,
— continuous method considers only the shaded particles
With continuous movement of microscopic preparation of the measuring line is a vertical line micrometer scale of the eyepiece.
Consider the particles which pass through the length of the bar, not missing a single one. Do not take into account those particles whose centers are outside the line, although some of them can pass through the end points of the line (see drawing ,
).
4.6.5. Measurements of particles in individual fields of view, performed with a ruler on the frosted glass on the screen of the projector or microscopic images. The increase must be adjusted so that the measured image of particles had a size not less than 1 mm. Measure the maximum chord of the particles in horizontal or vertical directions.
4.7. Automatic measurement of the particles.
Automatic measurement of particles in individual fields of view is carried out in the same way as when using a ruler (p.4.6.5). Depending on the type of the used counting devices measuring and can be performed on microscopic images or microscopic images.
4.8. The classification of shapes of particles can be characterized by their standard forms given in the reference application.
4.9. Test results confirmed by the Protocol which should contain:
the symbol or brand of powder;
the results of calculations of form factors;
a verbal description of particle shape;
the data about used equipment and the method of determining (manually or automatically);
conditions that could affect the results of the determination (for example, incomplete separation of the agglomerates);
the date of testing.
APPLICATION (reference). Standard forms of particle
APP
Reference
Standard forms of particle
Spherical ( |
Rounded ( |
Angular | ||||
| a) with the presence of curved surfaces |
b) with the presence of sharp corners and flat faces | |||||
from 1.0 to 1.2)
1.2 to 2.0)
from 2.0 to 5.0)Rod ( |
Needle ( |
Lamellar or scaly | |||||
| a) spherical, rounded or angular shape |
b) bryzgogasitel forms | ||||||
from 5.0 to 25.0)
over 25,0)| Dendritic | Particles with internal voids | |||||
| a) spongy (through pores) |
b) porous (closed pore) | in) hollow (with the presence of isolated voids with an area of more than 25% of the area of projection of a particle) | ||||
