GB/T 15076.12-1994 Chemical analysis method for tantalum and niobium - Determination of carbon content GB/T15076.12-1994 Standard download decompression password: www.bzxz.net

National Standard of the People's Republic of China
Chemical analysis methods of tantalum and niobium-
Determination of carbon content
Methods for chemical analysis of tantalum and niobium-
Determination of carbon content 1 Subject content and scope of application
This standard specifies the method for determining the carbon content in tantalum and niobium. This standard is applicable to the determination of the carbon content in tantalum and niobium. Determination range: 0.001%~~0.5%. 2 Reference standards
GB1.4 Guidelines for standardization work Provisions for the preparation of chemical analysis methods GB1467 General principles and general provisions for chemical analysis methods for metallurgical products 3 Summary of methods
GB/T 15076.12-94
The sample is burned at high temperature in the presence of flux in an oxygen flow, and carbon is oxidized to carbon dioxide. The oxygen is carried into a perchloric acid lock solution with a pH of about 9.5 to reduce the pH value. Then a constant pulse current is passed through the absorption liquid to electrolyze the pH value to restore it to its original value. The carbon content is calculated based on the amount of electricity consumed by the electrolysis. 4 Reagents and materials
Barium carbonate, powder, is placed in a secondary cup, and its height should be 2 to 5 mm above the ceramic semipermeable membrane. 4.1
4.2 Copper oxide: Burn in a 900℃ tube furnace with oxygen for 15 to 20 minutes and cool in a dryer. 4.3 Quartz sand: particle size 200 ~ 315μm, burn in oxygen flow at 1000℃ for 15 ~ 20min, cool in a sub-dryer. 4.4 Anhydrous magnesium perchlorate.
4.5 Alkaline asbestos.
4.6 Silver vanadate.
4.7 Main cup absorption solution: weigh 50g crystalline barium perchlorate [Ba(CIO,)2·3H20] and dissolve it in 1000mL double distilled water, add 30~~~40mL isopropanol to mix well, and store in a ground-mouth bottle. 4.8 Secondary cup solution: weigh 20g crystalline barium perchlorate Ba（CIO,)2·3H,0) and dissolve it in 100ml double distilled water, mix well, and store in a ground-mouth bottle.
4.9 Small cup solution: weigh 5g of crystalline barium perchlorate [Ba(CIO),·3H,O] and 3g of sodium chloride and dissolve them in 100mL of double distilled water, mix well, add a few drops of silver nitrate solution (50g/L), store in a ground-mouth bottle, and take the clear solution when used. 4.10 Perchloric acid solution (1+19).
4.11 Porcelain tube, outer diameter 21mm, inner diameter 17mm, length 600mm. Approved by the State Administration of Technical Supervision on May 9, 1994, implemented on December 1, 1994
GB/T 15076.12--94
4.12 Porcelain boat, length 88mm, burn in an oxygen flow at 1250℃ for 5-10min in a desiccator. 4.13 Oxygen, purity greater than 99%.
4.14 Carbon-containing molybdenum saw mark sample.
5 Instruments and equipment
5.1 Tubular combustion furnace, double porcelain tube, carbon silicon rod heating, power 5kW, maximum temperature should reach 1350C, with temperature control device. 5.2 Coulometric analyzer. The gas flow is shown in Figure 1. 4
6 Sample
611924
7(3)8(2)
Figure 1 Schematic diagram of gas flow
(- oxygen cylinder, 2- pressure reducing valve; 3- buffer bottle (greater than 5L): 4 Tubular combustion furnace; 5- magnesium perfluorite 6- alkali asbestos; 7(1), 7(2), 7(3) fine-tuning valve; 8(1), 8(2), 8(3)- rotor flow meter: 9 Dust collector (glass wool); 10 Desulfurization tube (silver vanadate); 11· Solenoid valve; 12- two-way piston; 13- electrolytic absorption cup 6.1 block or filament The sample needs to be made into small particles, cleaned with acetone or carbon tetrachloride, and air-dried. 6.2 The powder sample should be stored in a ground-mouth bottle and placed in a desiccator. 7 Analysis steps
7.1 Determination quantity
Weigh two samples, measure them independently, and take the average value. 7.2 SamplesbzxZ.net
Weigh the samples according to Table 1, accurate to 0.0001g. The saw powder sample is spread in a porcelain boat with 1g of quartz sand in advance and mixed; molybdenum powder and molybdenum, sawn rolled material samples are spread on the bottom of the porcelain boat and covered with 1g of copper oxide. Table 1
Carbon content, %
>0. 0050~0.10
>0.10~～0.50
Test material+
7.3 Blank test
GB/T15076.12—94
Weigh 1g of copper oxide or quartz sand in a porcelain boat, and measure the blank value three times under the same conditions as the test sample. The average value should be less than 10μg.
7.4 Calibration test
7.4.1 Positioning value calibration: perform endpoint positioning value calibration on the main cup absorption liquid. Make the pH value of the absorption liquid about 9.5. 7.4.2 Electricity calibration: A constant current source passes 1 coulomb of electricity through the absorption liquid. After electrolysis, the counter should display 126±2 counts. At this time, each count is equivalent to 0.5×10-6g of carbon.
7.4.3 Standard sample calibration: Measure the molybdenum standard sample containing carbon under the same conditions as the test sample. The absolute value of the difference between its value and the standard value should not be greater than the standard allowable error.
7.5 Determination
7.5.1 Connect the tube 7.5.2 Connect the coulometer power supply and start the agitator. After the instrument runs stably for about 30 minutes, check the system blank value, which should be less than 1μg/min. 7.5.3 Open the oxygen valve, adjust the fine-tuning valves 7(1), 7(2), and 7(3), and control the flow rates of flowmeters 8(1), 8(2), and 8(3) to 600m/min respectively. L/min500mL/min and 150ml/min. 7.5.4 Close piston 12 and quickly push the porcelain boat containing the sample (7.2) into the high temperature zone. 7.5.5 After the sample is pre-burned for about 1 minute, open piston 12, reset the counter and use a stopwatch to count. 7.5.6 The carbon dioxide generated by the combustion of the sample is carried by oxygen through the dust removal pipe and the desulfurization pipe into the electrolytic absorption cup and is absorbed by the barium perfluoride solution. After about 4 minutes, the system returns to the original blank and the electricity count is read. 8 Calculation and expression of analysis results
Calculate the percentage of carbon according to the following formula:
C(%)=(AB)×0. 5X10-6
Where: A—the electricity count obtained when measuring the sample; B—the electricity count obtained when measuring the blank;
m—the mass of the sample·g;
0.5×10-6——the mass of carbon corresponding to each electricity count, g. X100
The result should be expressed to 2 decimal places. If the carbon content is less than 0.1%, it should be expressed to 3 decimal places; if it is less than 0.01%, it should be expressed to 4 decimal places.
9 Allowable difference
The difference between the analysis results of laboratories should not be greater than the allowable difference listed in Table 2. Table 2
0. 001 0~~ 0. 005 0
>0. 005 0~0. 010
>0. 010~0. 050
>0. 050~0. 10
≥0.10～~0.50
Additional instructions:
GB/T 15076.12--94
This standard is proposed by China Nonferrous Metals Industry Corporation. This standard was drafted by Ningyi Nonferrous Metal Refinery. This standard was drafted by Zhuzhou Cemented Carbide Factory. The main drafters of this standard are Deng Longchang and Li Tianzhu. From the date of implementation of this standard, the former Ministry of Metallurgical Industry of the People's Republic of China issued the Ministry of Standard YB942 (5) -78 "Determination of Carbon in Molybdenum by Combustion Method" will be invalid.
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