GOST 23402-78

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  ГОСТ 23402-78

GOST 23402−78 Powder metal. Microscopic method of determining the size of particles (Change No. 1)

GOST 23402−78*

Group B59

STATE STANDARD OF THE USSR

POWDER METAL

Microscopic method for determining particle sizes

Metal powders. Microscopic method of particle size determination

AXTU 1790

Date of introduction 1980−01−01

The decision of the State Committee USSR on standards on December 22, 1978 N 3410 introduction installed from 01.01.80

Proven in 1984 by the Resolution of Gosstandard dated 30.11.84 4063 N validity extended to 01.01.90**
________________
** Expiration removed by the resolution of Gosstandart of the USSR from 21.06.89 N 1779 (IUS N 10, 1989). — Note the CODE.

* REISSUE (January 1986) Change N 1, approved in July 1985 (IUS 3−85).


This standard specifies a microscopic method for determining particle size of metal powders from 1 to 100 microns, with a spherical or polyhedral form of the particles.

Measurement and counting of particles is performed under an optical microscope to visually or automatically.

For the size of the particles take a visual measurement of the maximum chord of the particles in horizontal or vertical directions; the automatic measure a chord of the particle in the horizontal direction.

1. SAMPLING AND SAMPLE PREPARATION

1.1. The sample for testing weighing 5−7 g are selected according to GOST 23148−78*.
_________________
* Standards 23148−98. — Note the CODE.

1.2. The preparation is produced in two ways:

of dry powder;

using the suspension of powder in a dispersing fluid.

1.3. Prepared drug from dry powder: the sample for testing weight of 5−7 g was mixed thoroughly on a glass tile, pack strip length of 7−8 cm and divided into 7 or 8 approximately equal parts. Odd part is discarded and an odd mix and re-cut the same way. Repeated to produce samples weighing 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 dispersing liquid, evenly distribute the mixture with a stick on the glass, place the glass and push on it gently 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.

1.4. The drug is prepared using slurry: samples for test weighing 5−7 g was placed in a cuvette and added to the dispersing liquid as much to get a microscopic preparation with the number of particles in the field of view according to claim 1.5. Powder and liquid are mixed and transferred with a pipette a drop of the suspension on a glass slide, place the cover glass and press down on it gently to avoid the release of large particles outside of the glass.

1.5. From the test samples are prepared two drugs and compare them under a microscope. If they match, then the measurement is performed on one of them.

Believe that prepared the microscopic agents are the same, if the field of view, limited field of the basic rectangle or circle is:

from 6 to 30 particles in the measurements with the direct visual observation of the microscopic image;

not more than 150 particles in the automatic measurement on the microscopic image on the focusing screen or on the projector’s screen. The distance between the particles should be at least as large as the larger of the adjacent interconnected particles.

Failure to comply with these conditions, the preparation of microscopic drug repeat.

Sec. 1. (Changed edition, Rev. N 1).

2. EQUIPMENT

In the measurement using projection or optical microscopes that allow the observation in transmitted light or by direct observation. For measuring particle size of 1 micron requires an increase in 1400. The design of microscope lenses and eyepieces should provide a good image quality. Measurements can be by the pictures of microscopic images.

The magnification of the 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 must be no less aperture than the lens with which it is applied. To measure particles of 1 µm requires an increase in 1400.

Eyepiece with micrometer scale.

Counter odinnadtsatikilometrovy (for a leukocyte count of blood).

Measuring according to GOST 427−75.

Dropper according to GOST 25336−82 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 6246−82 or filter laboratory according to GOST 12026−76.

Medical absorbent cotton wool GOST 5556−81.

The dispersing liquid should meet the following requirements:

should not dissolve the particles of the test powder;

should not join with him in a chemical reaction;

should not be toxic;

should not degrade the quality of the microscopic image;

should be well wetted powder particles, preventing the formation of agglomerates.

An example of the dispersing liquid may be water containing 1−2% surfactant, and glycerin according to GOST 6259−75, paraffin oil immersion (cedar) oil GOST 13739−78. To consolidate the particles when you work with immersion lenses used film-forming quick-drying 4% solution of collodion in amylacetate.

(Changed edition, Rev. N 1).

3. TESTING

3.1. The particle size measurement is carried out by direct observation of the microscopic image, microscopic images: the image on the projection screen.

The interval of particle sizes break not less than 6 parts (classes)*. Particles the size of which corresponds to the lower limit of a class, belong to the class smaller.
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* The text matches the original. — Note the CODE.

3.2. 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 3.5. The individual fields of view selected on the drug, moving it to a value more than the diagonal of the rectangle or the diameter of the circle limiting the field of view. The area where you are measuring and the score of the particle is equal to: during a continuous movement of the drug — length of the line of the eyepiece multiplied by the length of the path traveled by the product from beginning to end of the measurement procedure; when monitoring individual fields of view — the sum of their squares.

3.3. If the powder contains particles in a large range of sizes and this is 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 consider only large particles at high magnification only small particles.

The results of the measurements at different magnifications respectively recalculated in accordance with paragraph 3.8. All measurements carried out at three magnifications or less.

3.4. 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.

3.5. 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, in the case of a rectangle 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. Particles on the other sides and corners does not take into account. In the case of the circle into account all the particles inside it, and all particles located on one semicircle and one end diameter carried out (see the devil.a, b).

The scheme of accounting of the particles during the measurements

The scheme of accounting of the particles during the measurements

a, b — separate fields of view; in, g — in continuous movement
the drug takes into account only the shaded particles.

With continuous movement of microscopic preparation of the measuring line is the vertical side of the rectangle, or 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 the devil.in, g).

3.6. Measurements of particles in individual fields of view produced with a ruler on the frosted glass on the screen of the projector or microscopic images. Line before use calibrate using an object micrometer. 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.

3.7. Automatic measurement of particles in individual fields of view is carried out in the same way as when using a ruler (p.3.6). Depending on the type of the used counting devices measuring and can be undertaken either at microscopic images or microscopic images.

3.8. The number of measured particles (when using the same magnification) or the calculated number of measured particles (when using two or three increases) should be not less than 625.

Under the calculated number of particles to understand the number of particles assigned to a selected magnification and is calculated according to the formula

,

(used three enlarge)

or

,

(used two enlarge)

where  — the estimated number of particles;

 — number of particle class measured at higher magnification;

 — the number of particles of grade measured at the middle magnification;

 — number of particle class measured at low magnification;

 — big increase;

 — average increase;

 — a small increase;

, , is the number of classes to be viewed at a given magnification.

The number of fields of view, viewed at different magnifications, should be the same. If the measurement of particles is carried out with continuous movement of the drug, at different magnifications should be viewed the same area pre

Paraty.

3.9. If the test result should be volume (mass) distribution of particle size class of the largest particles constituting at least 5%, taking control.

The number of measured particles of the controlling class shall be such as specified in the table.

If after measuring 625 particle number in the control class less than the required table, then on the advanced selected fields of view or to additional areas of the drug to conduct further measurement of particle size control class in order to receive the necessary amount of particles.

4. PROCESSING OF THE RESULTS

4.1. Quantitative distribution of particle dimensions are obtained by relating the number of measured particles class to the total number of measured particles.

4.1.1. The total number of the measured particles by using the same magnification is equal to the sum of all measured particles.

4.1.2. The total number of the measured particles by using two or three increases is equal to the number of estimated particles (p.3.8). Every product of the number of measured particles class correction factor is taken for the number of particles class.

4.1.3. The average particle size class is equal to the arithmetic mean value upper and lower limits of the class.

4.2. Volume (mass) distribution of particle size is getting erecting in the third degree the average particle size class and multiplying the result by the number of particles in this class, relating the obtained result to the sum of the products for all classes (see table.1 of the application).

The volume fraction of a separate class equal to its mass proportion, if the powder particles have the same density.

4.2.1. When measuring large particles for extra fields of vision in accordance with clause 3.9 the results of the analysis count. To do this, the number of particles of classes multiplied by a correction factor equal to the ratio of the number of visual fields, which were measured a particle of the controlling class, to the number of fields, which were measured by particles of other classes (see table.2−5 applications).

4.3. Measurement error occurs because of the finite number of measured particles. Given further formulas for calculating this error is a fair subject to statistically random orientation of the particles in the drug.

The error of measurement shall not exceed 2% in the case of determining quantitative and volumetric (mass) distribution of particle size.

In the case of the quantitative distribution of particle size the measurement error is calculated by the formula

,

and in the case of a volume distribution the error of measurement is calculated by the formula

,

where the quantitative proportion of particle class;

volume (mass) fraction of particles grade, %;

 — number of measured particles class.

Measurement error in quantitative distribution in the calculation of 625 particles is always less than 2%.

In the case of mass determination of volume (mass) distribution of particle size should be for each class, the quantities of particles to calculate the measurement error according to the formula, regardless of the number of counted particles.

(Changed edition, Rev. N 1).

4.4. Test results issued in the form of a Protocol which must contain the following information:

the name of the powder;

the results of the tests indicating what percent they are expressed;

specify whether the powder particles less than 1 micron.

APPLICATION (recommended). Granulometric composition of the powder, determined by microscopic method at three magnifications and observation of individual fields of view on microphotos (measured by the line of maximum chord of the particles is parallel to one of the parties

APP
Recommended

Granulometric composition of the powder, a certain microscopic
method at three magnifications and observation of individual fields of view
on microphotos (measured by the line of maximum chord of the particle
parallel to one of sides of the image)

Table 1

Table 2

Granulometric composition of the powder, determined by microscopic method
at the same magnification and observation of individual fields by using the eyepiece micrometer

Because the error in determining the content of classes (32−45) µm and (45−63) were more than 2%, there were further elemental analysis of these classes in three fields of view. The final result of the analysis is given in table.3.

Table 3

Granulometric composition of the powder (the same as in table.2) after
counting of large particles for extra visual fields

Table 4

Granulometric composition of the powder, determined by microscopic method
with continuous movement of the drug using the eyepiece micrometer

The last two class of particles was measured additionally by a continuous method on the three strips of equal square areas of the first strip. The final result is shown in table.5.

Table 5

Granulometric composition of the powder (the same as in table.4)
after additional measurement and counting of large particles