SU773493A1 - Method of determining specific surface of mean-fineness finely-ground powders - Google Patents

Description

(54) METHOD FOR DETERMINING A SPECIFIC SURFACE

THIN-MOLTED MEDIUM DISPERSION PROPERTIES The invention relates to the field of physical properties of substances and can be used in the production of polymer concrete / mortar, molding foundries, as well as in the ceramic industry. The known method for determining the surface of a quartz filler by compacting it and registering a change in the oscillation frequency of the vibrator depending on the specific surface area of the powder material l. The disadvantage of this method is the complexity of the instrumentation and the dependence of the measurement results on the moisture content of the material and its electrification. The known method for determining the specific surface area of fine ground fillers by means of preliminary compaction and determination of the volume weight 2 The method does not provide the required accuracy of measurements. The closest in technical essence to the present invention is a method for determining the specific surface of fine ground fillers 3, which consists in compacting the powder under a static load of 390410 kg / cm followed by determining the bulk weight and powder density and determining the specific surface using the formula -0. GB9 0.000014 where S is the specific surface of the material, VQ is the volume weight, g / cm, V is the density, g / cm-. However, when determining the specific surface of fine ground powders of medium dispersion (500-1600 cm / g) according to this formula, there are significant discrepancies with the known methods. The reasons for this are the non-attenuation of the deformations for 3 min, as well as the non-linear character of the dependence of the specific surface of fine powders of medium dispersion on their bulk density. The purpose of the invention is to improve the accuracy of determining the specific surface of finely ground powders of medium dispersion. The goal is achieved by the fact that the static load is carried out until the conditional stabilization of deformations, equal to the compression value of 0.01-0.015 mm for 30-40 minutes, and the specific surface is calculated by the formula U Ai-B - O. BsOG where S is the specific surface of the material , TG - density, 5 - volume mass, g / cm, V - coefficients, characterizing the dependence of voidness A and B - coefficients characterizing the dependence-void xi on the specific surface, moreover, A 439, and B 377618 cm / Fillers are a fine loose mass with a highly developed Yelnia surface. They include a solid and gaseous phase, located in the intergranular space, and therefore take an external load differently than solid bodies. The load distribution in the mass of fillers and their resistance to external forces are due to the frictional forces arising at the contact of particles. fillers. Under the action of an external load, the particles are displaced, as a result of which the filler (powder) reaches a denser state. At the same time, with increasing load and exposure time, the initial volume decreases to varying degrees, mainly due to the intergranular space. Stabilization of strain on the floor. It is a state when, under the action of external load, the creep rate acquires a value, the density of which and the compacted mass of the filler become stable, i.e. a constant volume and a constant mass, which is very important for testing building materials to compare results. The creep rate and stabilization time depend on the number of contacts of the filler particles, i.e. with an increase in the dispersion of the powder, the number of particles and contacts between them increases, and with a decrease decreases. Table 1 shows the dependence of the specific surface on the deformation of the sample; Table 2 shows the dependence of the bulk weight of the filler on the stabilization time. From tab. 1 and 2, it can be seen that the optimal mode is the amount of sample defacement equal to 0.01-0.015 in 30-40 minutes. Dependence of the specific surface of rarely dispersed fillers on their weariness; they are obtained by calculation and experimentation on the basis of the numerous experimental data obtained during the testing of averagely dispersed powders of different mineralogical composition. For testing, batches were selected. The specific surface area of each batch is limited by the GOST 310-60 PSC-2 instrument. The results obtained are statistically processed in order to obtain the true values of the useful surface of the filler, cm / g: V - 495, S, - 770, S, - 1020, S. 460, S - 1610. The bulk density (f) is determined by g / cm compaction under a load of 00 kgf / cm with an exposure to a conditional strain stabilization equal to an amount of compression of 0.01 mm in 30 minutes. The density (if) is determined by OST 810-60 in g / cm. The method of mathematical statistics establishes the true values of the bulk mass and lot size of the fillers for each pariah. The calculation of the voidness of the fillers is produced by the formula n g. Experimental and calculated data are given in Table. 3. In FIG. 1 is a graph showing the dependence of voidness on the specific surface of the filler, built on the basis of the true values of the specific surface J in FIG. 2, a device on which the optimum filling rate is determined. Based on the true values, the dependences are also determined and the values of the coefficients A and B and the constants C are determined: A 439 B 377618 cMVr C 0.3607 The device on which the optimal rate of fillers is determined contains the insert 1, to which the rod 2 is fixed with abutting him head indicator. The slave cylinder 3 is equipped with a holder with a 4 hour type indicator and is one of the parts of a detachable mold 5 mounted on a pallet 6. The method for determining the specific surface is illustrated by an example. To determine the specific surface area of a medium dispersed filler, a batch of 3 kg is taken from slag pumice. A 300 g sample is taken from the prepared for the test filler and transferred in parts to a pre-assembled mold. The mineral powder is evenly distributed.

The KNIFE is lightly pressed against the liner and placed under the compaction press. The insert is installed so that the indicator heads rest against the stem. The compaction load is gradually adjusted to 400 kgf / cm and maintained under this load for 30 minutes.

When the load reaches 400 kg / cm, the initial indicator reading is removed. After 30 minutes, the indicator reads again for the second time. If the deformation of the sample, calculated from the difference in the indicator readings is more than 0.01 m, the exposure time is increased by the next 30 minutes, etc. Stabilization occurs after two time intervals (60 min).

Then the load is removed and the form (together with the liner and the tray) is transferred to the baking sheet. The liner and the upper part of the form are removed and cleaned with a soft brush over the tray.

The filler in the bottom (working part of the form) is cut with a knife flush with the top edge. The excess mineral powder is carefully collected and weighed on an analytical or technical balance with an accuracy of 0.01 g.

The bulk weight of the filler (f) is calculated with an accuracy of 0.01 g / cm using the formula

N1 - Mo.

0 v

where the initial weight of filler is 300 g; the remainder of the initial sample - 124 g;

V - Form volume - 100 cm. Substituted numerical value, receive

 300 - -134

, 76 G / S "ni pl

10A

The bulk weight of the filler during compaction with a load is calculated as the arithmetic average of the three determinations. The discrepancy between the results should not exceed 0.02 g / cm.

Received: 1.765, 1.76 and 1.755. Then the average is

- 765: -1, T6 1.755

 - -one,

760 g / SP

° 3 The filler density is calculated as the arithmetic mean value.

5 two definitions. The discrepancy between the results of parallel measurements should not be more than 0.02 g / cm.

. The following results are obtained from the slag pumice for the filler: 2.33 and 2.87 g / cm.

0

Then the average is

g.v.a /

- g., 975 ricn

Substitute the obtained data of the volume mass and density in the formula

5 calculates the specific surface area of the filler from slag pumice.

$ 4 i9 + ZG 76- (nd (- - o, J60) 7-17

OR 7GOSM g.

0

in tab. Figure 4 presents the comparative data of the results for determining the specific surface area in various ways.

The proposed method makes it possible to significantly increase the accuracy of measurements in determining the specific surface of fine ground fillers; it does not require cumbersome equipment and complex calculations.

Table 1

495

770

1020

1460

1610

1.66 1.62 1.59 1.56 1.55

g / cm 2,65 2,65 2,63 2-, 65 2,65 0,373 0,388 0,400 0,413 0,416

dispersion, which consists in determining the bulk weight of the powder with a preliminary compaction under static load of 390–410 kg / cm and determining the density of the powder, which, in order to improve the determination accuracy, the static load is carried out until the conditional stabilization of deformations equal to compression value 0.01-0.015 mm

table 2

Table 4

the specific surface of the material, density, g / cm L is the volume mass, the coefficients characterizing the dependence of voidness f on the specific surface, moreover A 439 cm / g, and В «377618 CMVr.

Sources of information taken into account in the examination

1. USSR author's certificate 191221, cl. G 01 N 15/08, 1965.

25

25

2. Determination of the specific surface of the sand, GOST 8735-65.

3. USSR author's certificate number 614362, cl. G 01 N 13/00, 1976 (prototype). 4 15002000 Specific Surface Area

Claims (1)

Claim A method for determining the specific surface area of finely ground powders of medium dispersion, which consists in determining the bulk density of the powder with preliminary compaction under a static load of 390-410 kg / cm ² and determining the density of the powder, which is 60 in that, in order to increase the accuracy of determination, the static load is carried out until the conditional stabilization of the deformations is equal to a compression value of 0.01-0.015 mm 65 in 30-40 minutes, and the specific surface 'is calculated by the formula S = A ”B (--0.3607 ^, where S is the specific surface of the material, cm ^g / g; f is the density, g / cm ³ 1 jl · is the bulk mass, g / cm ³ ; A and B are coefficients characterizing the dependence of the voidness ^p on the specific surface, with A = 439 cm ^g / g, and B and 377618 cm ² / g.