This standard is applicable to the determination of refractory metals and compounds with a particle size (expressed as volume surface area average diameter) ranging from 0.5 to 50 μm. GB/T 3249-1982 Determination of Refractory Metal and Compound Powder Particle Size Fisher Method GB/T3249-1982 Standard Download Decompression Password: www.bzxz.net

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Determination method of particle size of powders of refractory metals and compounds-method
-Fisher
UDC 621.782
: 669--492.2
: 620.168
GB 3249—-82
This standard is applicable to the determination of particle size (expressed as volume surface area average diameter) of refractory metals and compound black materials in the range of 0.5 to 50μm
This standard adopts the Fisher method, which is an air permeation method. Since the gas permeability of the powder sample layer is related to the specific surface area of ​​the powder, the specific surface area can be calculated by this method. The volume surface area average diameter converted from this surface is used to express the particle size. According to Fisher's method, the powder density has the following expression.
Wherein, dvs
nCL2pMF
V(ALP-M)\(PF)
-powder particle size, μm.
n- Air viscosity, g·cm-1·s~l
C--- Conductivity of needle valve, cm\·s~1
.cm H,O-1
L'oM'F
(ALP-M)'(PF)
- Instrument constant (c is defined as 60,000/℃), cm*1.14
L- Height of powder sample layer, cm.
p- True density of powder sample, g·cm-sM-— Mass of powder sample, g.
A- Cross-sectional area of ​​powder sample layer, cm2,- Pressure before air enters powder sample, cmH,o. F
- Pressure after air enters powder sample, cmH,O Take the mass of powder sample equal to its true density, that is, M=β, and L=
Where, e is the porosity of powder sample layer.
(1) becomes
Take A=1,267cm2, (2) becomes:
L= 0.7893
(3)
Take P=50cmH, O, c=Cl=3.8cm (that is, the result after calibration of the first gear), from (3) and (4) we have: Guohao Standard Bureau 1982-06-21 Issued
1983-03-01 Implementation
GB 3249-82
0.3598(1-e)+0.04
(5)
Take cc7.6cm2 (that is, the result after calibration of the second gear), the dys calculated from (5) should be multiplied by 2 to get the particle size value. According to (4) and (5), the calculation is graphed. For this purpose, a particle size reading plate is drawn. With porosity as the horizontal coordinate (its range is 0.4 to 0.8, and the graduation interval is 0.005), and sample height as the vertical coordinate, a sample height line is drawn according to formula (4) for the purpose of pressing the sample. In addition, with F/2 as the vertical coordinate, a set of equal particle size curves is drawn according to formula (5). For the sample porosity corresponding to the sample height, read the value on the reading plate according to the water level height F/2 of the forearm of the pressure gauge (when using the first gear, it is a direct reading; when using the second gear, the reading should be multiplied by 2 to obtain the particle size value)
2Use the Fisher powder particle size tester (see the schematic diagram of the Fisher instrument device). 2
Simple diagram of the Fischer-Lehr apparatus
1—air,
6—porous plug
2—pressure regulating valve,
7—filter paper pad,
11—pressure gauge,
2.1 Main components
3—pressure regulating tube,
8—sample,
12 particle size reading plate,
2.1.1 Air pump and pressure regulating valve at the air inlet end. 2.1.2 Pressure regulating tube and desiccant tube.
4—desiccant tube,
9—tooth
13, 14—needle valve,
5 sample tube
10—hand wheel
15—shift valve
2.1.3 Fine-tuning needle valve at the air outlet end. When using the first gear, lock the shift valve and fine-tune it to make the instrument constant C equal to 3.8 cm; when using the second gear, fine-tune it to make the instrument constant ℃ equal to 7.6 cm*/2. 2.1.4 The pressure gauge requires that the inner diameter of the glass is very uniform along the length, and the ratio of the inner diameter of the front arm r. to the inner diameter of the rear arm r. is r./r. = 1 ± 0.005. 2.1.5 Grain size reading plate. The lines on the plate should be clear and the line width should be less than 0.015 cm. The sample height line and the equal grain size line should respectively comply with formulas (4) and (5)
GB 3249---82
2.1.6 Two ruby ​​standard tubes are used to calibrate the instrument. The upper layer of the tube is engraved with the tube number, porosity value, first gear (high value) grain size value, and second gear (low value) grain size value. Its value must be accurately calibrated with a capillary tube. 2.1.7 Two or more sample tubes, inner diameter 1.27 ± 0.005 cm. 2.2 The main accessories are: two or more pairs of perforated brass plugs, a long screw for loading and unloading brass plugs, a powder funnel, a box of 15mm fast filter paper, and a rubber support for sample tubes. 3 Sample preparation
The sample to be tested should be uniform and representative. The sampling plate should be more than twice the true density of the sample. The sample is required to be dry and free of lumps, and properly stored to prevent oxidation. If any of the following three conditions occurs, this method is not applicable: The shape of the powder is poorly equiaxed.
The powder will deform or break under slow pressure, and the powder will agglomerate when pressure is applied.
4 Calibration of the receiver
4.1 Component inspection
4.1.1 The crossbeam of the particle size indicator needle should be parallel to the baseline of the reading plate, and should coincide with the porosity indicator needle when falling. The rack should be perpendicular to the baseline of the reading plate when moving up and down.
4.1.2 The sample tube and porous plug must not be worn. 4.1.3 The ruby ​​standard tube, pressure gauge and fine-tuning needle valve should be kept clean and accurate. 4.1.4 The upper and lower rubber pads for clamping the sample tube should be guaranteed to be leak-proof. 4.1.5 The position of the yellow steel support rod for pressing the sample should be appropriate, that is, the distance between the bottom plane of the rack and the upper plane of the brass support screw of the base should be kept equal to the total thickness of the two porous plugs and two pieces of fast filter paper. At this time, the particle size indicator needle on the rack just points to the baseline of the reading plate!
4.1.6 The desiccant should remain effective (if color-changing silica gel is used, it should remain blue). 4.1.7 The liquid level of the voltage regulator tube should be on the water level scale line, and the bubbling speed should be 2 to 3 bubbles per second to maintain the pressure at the air inlet end P = 50 ± 0.4 cmH.o.
4.2 Calibration steps
4.2.1 Adjust the zero position of the pressure gauge: move the rack downward to align the particle size indicator needle with the baseline of the reading plate, remove the sample tube, and then turn the pressure gauge water level adjustment knob to align the water level meniscus with the upper edge of the particle size indicator beam. 4.2.2 Turn on the power supply, run for 20 minutes, install the empty sample tube, turn the air adjustment valve to make the vertical tube in the voltage regulator tube bubble, and control the bubbling speed to 2 to 3 bubbles per second. The water level of the pressure gauge gradually rises, and the water level height reached within 1 to 2 minutes should be 25 cmH.o.
4.2.3 Calibration of the first gear
4.2.3.1 Check the shift valve and put it in the first gear position. Remove the empty sample tube, install the ruby ​​standard tube between the rubber pads on the right side of the rack, turn the hand wheel to the right, press the purple ruby ​​standard tube to prevent it from leaking. At this time, the water level of the pressure gauge gradually rises. 4.2.3.2 Move the reading plate so that the porosity value indicated by the porosity pointer is consistent with the value shown on the ruby ​​standard tube. Do not touch the reading plate afterwards.
4.2.3.3 Turn the hand wheel to move the rack upward until the upper edge of the beam of the particle size indicator needle is aligned with the meniscus of the pressure gauge water level, and read the particle size value. The value should be consistent with the first gear value shown on the ruby ​​standard tube, and the difference should not exceed 3%. Otherwise, calibrate according to the following steps. 4.2.3.4 Adjust the gear (high value) needle valve (the water level of the pressure gauge is then adjusted) so that the particle size indicated on the reading plate is consistent with the first gear value given by the ruby ​​standard tube, and the difference does not exceed 3%. The calibration of the first gear is completed. Do not touch the first gear needle valve afterwards. 4.2.4 Adjustment of the second gear (low value) needle valve: Loosen the shift valve to the second gear position. At this time, the water level of the pressure gauge will drop slowly. After the water level stabilizes, drop the rack to align the upper edge of the beam of the particle size indicator needle with the meniscus of the pressure gauge water level. The particle size indicated by the particle size indicator needle should be consistent with the red gem 55.
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