Test method for gas emission characteristics of colloidal graphite in vacuum for use in electron tube
Some standard content:
Electronic Industry Standard of the People's Republic of China
SJ/T10550-94
Test method for gas emission characteristics of colloidal graphite in vacuum for use in electron tube1994-08-08Published
1994-12-01Implemented
Published by the Ministry of Electronics Industry of the People's Republic of ChinaElectronic Industry Standard of the People's Republic of China
Test method for gas emission characteristics of colloidal graphite in vacuum for use in electron tube1Subject content and scope of application
SJ/T10550-94
This standard specifies the test method for vacuum degassing performance of graphite emulsion used in vacuum electronic devices. This standard is applicable to the dynamic test of the degassing rate, degassing volume and degassing composition of the gas desorbed and decomposed by the graphite emulsion used in vacuum electronic devices in a vacuum environment. 2 Method Summary
This test adopts the "dynamic conductance method". When the sample placed in a sample chamber of known volume is heated and degassed, under the condition that the effective pumping speed of the system at the outlet of the orifice with known conductance is much greater than the known conductance value, the dynamic curve of the pressure change in the sample chamber with time (temperature) is measured and plotted, and the degassing rate and degassing volume are calculated. At the same time, the gas is introduced into the mass spectrometry analysis system to analyze the degassing components and their percentage values.
3 Instruments and Equipment
3.1 Test system, as shown in Figure 1.
3.2 Exhaust System
The exhaust system should have no selective exhaust and "memory effect" on the gas, and can obtain a clean ultra-high vacuum. The effective pumping speed Se at the outlet of the limiting orifice should be more than 50 times greater than the known conductance value of the limiting orifice. It is recommended to use a low oil return rate diffusion pump and add an efficient oil trap to the rough pumping system. The ultimate vacuum degree of the exhaust system should be better than 8×10-“Pa. 3.3 Analysis system
The analysis system should have no selective exhaust and “memory effect” on the gas, and can obtain clean ultra-high vacuum. It is recommended to use quadrupole mass spectrometer, turbomolecular pump, sputtering ion pump, high-efficiency oil trap, rotary vane mechanical pump and ultra-high vacuum valve and other components. The ultimate vacuum degree of the analysis system should be better than 1×10-7Pa. 3.4 Quadrupole mass spectrometer
Mass range M: 1~100amu;
Sensitivity Sn, ≥1.5X10-A/Pa
Resolution ()) 10x≥150;
Full scanning speed: ≤1s.
The instrument is controlled by a microcomputer and automatically processes data, and can display and print out mass spectrometry quantitative Analytical results. Approved by the Ministry of Electronics Industry of the People's Republic of China on August 8, 1994 and implemented on December 1, 1994
To exhaust system
To analysis system
SJ/T10550-94
Figure 1 Schematic diagram of the test system
1-A flow-limiting orifice with known conductance, the conductance value of which is C-1~2L/s; 2, 5-Glass grease-free ball valve;
3-Ultra-high vacuum gauge:
4-Oven heating zone:
6-Nickel sample boat:
7-The sample to be tested is placed in the sample placement room;
-A sample room, the vacuum pipeline above the flow-limiting orifice is collectively referred to as the sample room, its volume value V=1~2L, the part where the sample to be tested is placed is called the quartz sample tube , made of a quartz tube with a diameter of 30 to 40 mm, installed at an angle of 45°9-tube high-temperature furnace, at a test temperature of 440°C, the temperature difference in an isothermal zone not shorter than 100 mm should not be greater than ±2°C;
-Test sample:
-Thermocouple, K-graded nickel-chromium-nickel-silicon thermocouple;12--Inlet flange;
Pipeline heating zone A;
-Ultra-high vacuum valve;
-Ultra-high vacuum fine-tuning valve;
16-Pipeline heating zone B.
Note: The inner diameter of the vacuum pipeline above the flow-limiting orifice in the test system should be no less than 25mm to ensure sufficient conductance; the conductance value of the pipeline connecting the vacuum gauge should be no less than 12L/s, so that the pressure difference at both ends can be Negligible. 3.5 Ultra-high vacuum gauge
SJ/T10550—94
The range should be able to cover 1×10-1~5×10-Pa; regulated emission current: 0.1mA and 1mA, the vacuum gauge must be calibrated with nitrogen. 3.6 Temperature program controller
The temperature value is displayed digitally, the program is controlled by a microcomputer, and it has multi-stage program heating and insulation functions. The heating rate and insulation temperature and insulation time can be set in advance. The control deviation of the heating rate should not be greater than ±2℃/min; the control deviation of the insulation temperature should not be greater than ±1℃.
3.7 Double-pen function recorder
Y, pen is a temperature recorder with K graduation; Y, pen is a 0100mV DC voltage recorder (here, it acts as a vacuum recorder). The speed of recording paper should be adjustable between 300 and 3000 mm/h; the full response time of Yl, Y, pen should not exceed 1s. 3.8 The sensitivity of analytical balance should not exceed 0.1 mg.
4 Test steps
4.1 Sample preparation
4.1.1 Carrier preparation and treatment
4.1.1.1 Use a grinding wheel cutter to cut a hard glass tube with a wall thickness of 1mm and an inner diameter of 13~15mm that has never been exposed to oil fingers into a glass ring with a length of 9±0.1mm.
4.1.1.2 The glass ring is treated by the following steps: tap water rinse - organic solvent (acetone or trichloroethane) ultrasonic cleaning - deionized water rinse - alcohol dehydration - blow dry with a hair dryer or place the glass ring in an electric blower to dry. 4.1.1.3 Use an analytical balance to weigh the mass of the carrier (glass ring) one by one, accurate to 0.1 mg. 4.1.2 Sampling
4.1.2.1 Place the bottled graphite emulsion sample to be tested on a ball mill with a speed of 120r/min and roll it for more than 5 hours. 4.1.2.2 Use a clean brush to evenly apply the rolled graphite emulsion sample on the inner surface of the cleaned glass ring. 4.1.2.3 Dry it with a hair dryer or place it in an electric heating blower. 4.1.3 Sample pretreatment
4.1.3.1 Place the glass ring coated with the sample in a black and white picture tube baking furnace, a color picture tube low melting point glass sealing furnace or a horse furnace for baking according to its different use occasions. 4.1.3.2 When the temperature of the glass ring drops to about 50℃ after baking, first place it in a drying cylinder and continue to cool to room temperature. 4.1.3.3 Within 15 minutes, use an analytical balance to weigh the mass of the glass rings coated with the sample (hereinafter referred to as "sample") one by one, with an accuracy of 0.1 mg. The mass difference between the sample with the same number and its carrier is the net mass of the sample. Its value is controlled between 10 and 30 mg according to the amount of degassing.
4.1.3.4 Place the weighed sample into the test system as soon as possible or store it in a constant temperature (20-25°C) and constant humidity (relative humidity 50%-60%) drying cylinder.
4.2 Preparation before testing
4.2.1 Place 1.02×105Pa dry nitrogen into the vacuum system through the vent valve, open the test system sample injection flange, use a magnet to attract the clean nickel boat, place the sample and a glass ring used for blank test in different sample placement tubes in the sample storage area according to the number.
4.2.2 After the sample is placed, the injection tube should be replaced immediately. The oxygen-free copper sealing gasket on the sample flange is installed on the sample flange. The test system is evacuated. When the system vacuum is better than 1×10-3Pa, the vacuum is stopped and the sample is vacuum-soaked in the sample tube for 24 hours. 4.2.3After 24 hours, the test system is evacuated again. When the system vacuum is better than 1×10-\Pa, the test system is baked for 3
degassing.
SJ/T10550-94
4.2. 4 Use electric oven, tubular high temperature furnace, pipeline electric heating belt and gas burner to bake and degas the test system except the sample storage area.
4.2.4.1 The oven degassing is controlled by "oven temperature program controller". The oven heating rate is 10℃/min, the insulation temperature is 400℃C, and the insulation time is 30min. After the insulation is completed, turn off the oven heating power supply and let it cool down naturally. 4.2.4.2 When carrying out 4.2.4.1, move the "tubular high temperature furnace" to the specified position of the quartz sample tube, and use the "temperature program controller" to bake and degas it. The "temperature program controller" should raise the temperature of the "tubular high temperature furnace" to 600℃ within 20min, keep it warm for 1h and then cool it down. When the insulation is over, immediately remove the quartz sample tube from the "tubular high temperature furnace" and force the furnace to cool with compressed air.
4.2.4.3 While carrying out 4.2.4.1 and 4.2.4.2, turn on the power supply of the pipeline electric heating belt, bake and degas the stainless steel vacuum pipeline and ultra-high vacuum valve, and the degassing temperature is 250℃. When the oven insulation is over, turn off the power supply of the pipeline electric heating belt at the same time and let it cool down naturally.
4.2.4.4 Before the oven starts to keep warm and before the insulation is over, use a gas burner to heat and degas the glass pipeline except the sample storage area twice, and each degassing time is 5min.4.2.5 When the oven temperature drops to 10 At 0℃, the oven can be removed and the ultra-high vacuum gauge can be connected. After the gauge is degassed by electrode bombardment for 5 minutes, the vacuum degree of the system can be tested. At this time, the vacuum degree of the test system should not be lower than 5X10~5Pa. 4.2.6 While carrying out 4.2.3 to 4.2.5, the mass spectrometry analysis system should also start the rotary vane mechanical pump, turbomolecular pump and sputtering ion pump to evacuate the analysis system, and use the pipeline electric heating belt to bake and degas the analysis chamber and the quadrupole mass spectrometer probe (baking temperature is 250℃, baking time is 1h). During this period, the ultra-high vacuum gauge in the analysis system is degassed by electrode bombardment twice (5min/time). When the temperature of the analysis chamber and the quadrupole mass spectrometer probe drops to 50℃, turn on. Power supply of the quadrupole mass spectrometer. After 30 minutes, close the sputtering ion pump valve. At this time, the vacuum degree of the analysis system should not be lower than 5×10-Pa; and use the quadrupole mass spectrometer to measure the residual gas background composition and its partial pressure in the analysis system. 4.2.7 Turn on the power supply of the "dual-pen function recorder", adjust the sampling potentiometer on the ultra-high vacuum gauge, calibrate the zero point and full scale of the Y. recording pen, and set the paper feed speed to 300mm/h. Close the ultra-high vacuum valve (14) and ultra-high vacuum fine-tuning valve (15) in the test system.
4.2.8 When the furnace temperature of the "tubular high-temperature furnace" forced to cool by compressed air is lower than 30°C, according to the heating rate of 10°C/min and the insulation temperature of 4 40℃, 6min holding time test requirements, set the P, I, D values, holding temperature value and holding time value of the "temperature program controller".
4.3 Blank test
4.3.1 Use a magnet to attract the nickel boat, and push the glass ring of the uncoated graphite emulsion sample into the bottom of the quartz sample tube; move the "tube high temperature furnace" to the specified position of the quartz sample tube, and turn on the paper feed switch of the "double pen function recorder". 4.3.2 Use a magnet to attract the valve ball to close the fat-free ball valves (2) and (5) connected in parallel on both sides of the flow limiting orifice; turn the "temperature program controller" to the "run" gear, and then, the quartz sample tube placed in the "tube high temperature furnace" is heated and kept warm according to the set program. At the same time, the two recording pens of the recorder respectively record two curves of the temperature and vacuum in the sample tube changing with time. The test continues until the set program is completed. During this period, attention should be paid to timely switching the range of the vacuum gauge and marking it on the recording paper.
4.3.3 Open the fat-free ball valves (2) and (5), move the "tube high temperature furnace" out of the quartz sample tube, and after the temperature of the quartz sample tube drops to 100°C, use a magnet to attract the nickel boat to move the sample from the quartz sample tube to the sample tube where the sample was originally placed, turn off the paper feed switch of the "double-pen function recorder", and turn off the heating power of the "temperature program controller". 4.4 Test of degassing rate and degassing volume
4.4.1 Repeat 4.2.8.
SJ/T10550-94
4.4.2 Use a magnet to attract the nickel boat and push the sample to be tested into the bottom of the quartz sample tube; move the "tube high temperature furnace" to the specified position of the quartz sample tube, and turn on the paper feed switch of the "double-pen function recorder". 4.4.3 Repeat 4.3.2 and 4.3.3.
4.4.4 If multiple samples are to be tested, repeat the steps in 4.4.1 to 4.4.3. 4.5 Outgassing component test
4.5.1 Open the ultra-high vacuum valve (14), change the pipeline electric heating belts A and B from parallel to series connection, turn on the heating power supply, and maintain the temperature of the stainless steel vacuum pipeline leading to the mass spectrometry analysis system at about 100°C. 4.5.2 Use the quadrupole mass spectrometer in the analysis system to measure the background composition of the residual gas in the test system and its partial pressure. Preset the types of 12 gases that the quadrupole mass spectrometer needs to automatically track, the partial pressure range, the mass spectrometer working mode and the automatic analysis time. 4.5.3 Repeat 4.2.8 and 4.4.2.
4.5.4 Use a magnet to attract the valve ball to close the fat-free ball valve (2) and (5); turn the "temperature program controller" to the "run" position. After that, the quartz sample tube is heated and kept warm according to the set program. The gas sample is introduced into the mass spectrometry analysis system through the ultra-high vacuum valve (14) and the stainless steel vacuum pipeline. The quadrupole mass spectrometer automatically collects gas samples, processes data and displays it on the screen according to the preset state, and automatically stores the analysis results on the disk or prints them. At the same time, the two recording pens of the recorder record two curves of the temperature and vacuum degree in the sample tube changing with time. The test continues until the set The specified program runs until it is completed. During this period, attention should be paid to timely switching the vacuum meter range and marking it on the recording paper. 4.5.5 Repeat 4.3.3.
4.5.6 If multiple samples need to be tested, it is necessary to repeat the steps of 4.5.3 to 4.5.5. 5 Data processing
5.1 Curve of the change of the degassing pressure of the unit mass sample with time (temperature) Based on the curve of the change of the degassing pressure with time (temperature) measured by the experiment and formula (1), the curve of the change of the degassing pressure of the unit mass sample with time (temperature) is obtained.
p(t) = [pi(t)-po(t)] 10
Wherein: P(t)-the change of pressure in the sample chamber caused by 100mg sample during the test with time (temperature), Pa; P(t)-the change of pressure in the sample chamber caused by the sample during the test with time (temperature), Pa;
P. (t) The change of pressure in the sample chamber caused by the carrier during the test with time (temperature), measured by the blank experiment, Pa
M-the net mass of the sample, mg.
5.2 The curve of the change of the degassing rate of the unit mass sample with time (temperature) is calculated according to formula (2): q(t)=p(t)c+
dp(t)y
Wherein: g(t)-the change of the degassing rate of 100mg sample with time (temperature), Pa·L/S; C-the known conductance value of the limiting orifice, L/sVthe volume value of the sample chamber, LWww.bzxZ.net
t-time, s .
5.3 Calculation of the amount of gas released per unit mass of the sample: ·(2)
SJ/T10550—94
In time t, the amount of gas Q (Pa·L) released by the unit mass (100 mg) of the sample is calculated according to formula (3): Q
dp(t2vat
Ep(t)C+
5.4 The components of the gas released by the sample and their percentage content as a function of time (temperature) (3)| |tt||The quadrupole mass spectrometer controlled by a microcomputer and working in the partial pressure mode automatically outputs the curve of the gas release component changing with time during the test and the partial pressure value at each moment, and then calculates the percentage value of various gas release components according to formula (4): X
Wherein, X is the percentage value of a certain gas; P is the partial pressure value of the gas, Pa
PL-×100%
The sum of the partial pressure values of various gases released by a sample, Pa. 6 Test report
6.1 The first page of the test report shall indicate the following: a.
Graphite emulsion name,
Model (or brand):
Net mass of the sample;
Manufacturer,
Testing unit, personnel and date:
Testing conditions (heating rate, initial test overflow, insulation temperature, insulation time); unit mass value (100mg).
Outgassing rate versus time (temperature) curve (Figure 2). 6.2
q(Pa· L/s)
The vertical axis (1) is the outgassing rate g(Pa·L/s), the vertical axis (2) is the temperature T(C), and the horizontal axis is the time t(s). 6.3 Curve of cumulative degassing volume changing with time (temperature) (Figure 3) (4)
Q(Pa·L)
SJ/T10550-94
T(℃)
Vertical axis (1) is cumulative degassing volume Q(Pa·L), vertical axis (2) is temperature T(C) horizontal axis is time t(s)). Note: In order to more clearly express the relationship between degassing rate and cumulative degassing volume, Figures 2 and 3 can be combined and drawn on the same coordinate paper. 6.4 Peak value of degassing rate and its corresponding temperature and cumulative degassing volume of the whole process (Table 1). Table 1
Peak value of degassing rate
Sample name
(Pa·L/s)
6.5 Curve of degassing composition changing with time (temperature) (Figure 4). Pn(Pa)
Peak value of degassing rate
Temperature corresponding to
T(℃)
Cumulative degassing volume during the whole process
(Pa·L)
SJ/T10550—94
The ordinate (1) is the partial pressure of various degassing components Pn(Pa), logarithmic coordinates), the ordinate (2) is the temperature T(C), and the abscissa is the time t(s).
6.6The percentage of degassing components corresponding to the peak value of degassing and the beginning and end of heat preservation (Table 2). Table 2
Main sources of error corresponding to the outgassing peak
Gas composition
Corresponding outgassing composition
Corresponding outgassing composition at the beginning of insulation
Corresponding outgassing composition at the end of insulation
7.1 Errors introduced by the sample during sampling, pretreatment and storage (such as weighing errors, the length of time the sample is exposed to the atmosphere after pretreatment and stored in a vacuum environment, etc.). 7.2 Temperature fluctuations of the tubular high-temperature furnace and thermocouple measurement errors. 7.3 Calibration and measurement errors of the ultra-high vacuum gauge, stability of the filament emission current. 7.4 Calibration and measurement errors of the quadrupole mass spectrometer, and errors introduced by the continuous change of outgassing composition within a scanning cycle.
7.5 Errors caused by the background vacuum of the test system. 7.6 When the test system is baked and degassed, the sample will not be completely at room temperature, which will have a certain impact on the test results. 8 Precautions
8.1 Clean tools must be used during sampling, weighing and injection, and fiber-free gloves or finger cots must be worn. 8.2 During the test, the pressure in the sample chamber must be ensured to be lower than 6.7×10-Pa to ensure that the airflow passing through the flow-limiting orifice is always in a molecular flow state.
8.3 The degassing rate and degassing volume measured by this method are equivalent to nitrogen values. 8.4 The ultrahigh vacuum gauge, quadrupole mass spectrometer and thermocouple must be calibrated. 8.5 It is recommended to use a microcomputer to process the results measured by this method; when the requirements are not high, manual approximate calculations are also allowed.
8.6 The accuracy of the degassing rate and degassing volume tested by this method is ±10%; the accuracy of the mass spectrometry quantitative analysis of the degassing components is ±20%.
Additional instructions:
SJ/T10550—94
This standard is under the jurisdiction of the Standardization Institute of the Ministry of Electronics Industry. This standard was jointly drafted by Shanghai Vacuum Electronic Devices Co., Ltd. Electron Tube Factory No. 2 and Danyang Electronic Materials Factory. The main drafters of this standard are Qian Yongsheng and Gong Chunlong9
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