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GB/T 34520.8-2021 English PDF (GBT34520.8-2021)

GB/T 34520.8-2021 English PDF (GBT34520.8-2021)

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GB/T 34520.8-2021: Test methods of continuous silicon carbide fibers -- Part 8???Oxygen content

This document specifies the sample preparation, sample test, and calculation of test results for the determination of oxygen content in continuous silicon carbide fibers by inert gas fusion-infrared absorption method. This document applies to the determination of the total oxygen content of continuous silicon carbide fibers by the inert gas fusion-infrared absorption method. Refer to this document for the oxygen content test of discontinuous silicon carbide fibers and matrix. Refer to this document for the oxygen content test of other ceramic fibers.
GB/T 34520.8-2021
GB
NATIONAL STANDARD OF THE
PEOPLE REPUBLIC OF CHINA
ICS 49.020
CCS V 13
Test methods of continuous silicon carbide fibers - Part 8:
Oxygen content
ISSUED ON: AUGUST 20, 2021
IMPLEMENTED ON: MARCH 01, 2022
Issued by: State Administration for Market Regulation;
Standardization Administration of the PEOPLE Republic of China.
Table of Contents
Foreword ... 3
Introduction ... 4
1 Scope ... 6
2 Normative references ... 6
3 Terms and definitions ... 6
4 Test principle ... 7
5 Test environment ... 7
6 Instruments and materials ... 7
7 Sample preparation ... 8
8 Instrument blank test ... 8
9 Instrument calibration ... 9
10 Sample test ... 10
11 Calculation of test results ... 10
12 Test report ... 11
Appendix A (informative) Precision calculation ... 12
Bibliography ... 13
Test methods of continuous silicon carbide fibers - Part 8:
Oxygen content
1 Scope
This document specifies the sample preparation, sample test, and calculation of test results for the determination of oxygen content in continuous silicon carbide fibers by inert gas fusion-infrared absorption method.
This document applies to the determination of the total oxygen content of continuous silicon carbide fibers by the inert gas fusion-infrared absorption method. Refer to this document for the oxygen content test of discontinuous silicon carbide fibers and matrix. Refer to this document for the oxygen content test of other ceramic fibers. 2 Normative references
The contents of the following documents constitute essential provisions of this document through normative references in the text. Among them, for dated references, only the version corresponding to the date applies to this document; for undated references, the latest version (including all amendments) is applicable to this document. GB/T 674 Chemical reagent - Copper (II) oxide powder
GB/T 1446 Fiber-reinforced plastics composites - The generals
GB/T 4844 Pure helium, high pure helium and ultra pure helium
GB/T 8170 Rules of rounding off for numerical values & expression and judgement of limiting values
GB/T 26016 High purity nickel
GB/T 26017 High purity copper
GB/T 34520.1 Test method for continuous silicon carbide fiber - Part 1: Size content of filament yarn
3 Terms and definitions
There are no terms and definitions that need to be defined in this document. 4 Test principle
Put the continuous silicon carbide fiber sample (hereinafter referred to as the sample) into a graphite crucible; the sample is melted and decomposed under the protection of an inert carrier gas (helium), and the oxygen in it reacts with the carbon in the graphite crucible to generate carbon monoxide and carbon dioxide, which are then carried by the carrier gas into the infrared absorption detection cell of carbon monoxide and carbon dioxide. The infrared absorption detection cell measures the absorption light intensity of carbon monoxide and carbon dioxide concentration at 4670 nm and 4260 nm respectively and outputs the electrical signal value. The data receiving and processing system calculates the oxygen content of the sample according to the electrical signal value output by the detector and the sample mass, and displays it in mass fraction. 5 Test environment
The standard test environmental conditions are performed according to the standard environment requirements specified in GB/T 1446, the temperature is (23 ?? 2) ???, and the relative humidity is (50 ?? 10) %.
6 Instruments and materials
6.1 Oxygen and nitrogen element analyzer
6.1.1 Instrument composition: an oxygen and nitrogen element analyzer (hereinafter referred to as the instrument) is mainly composed of an analytical balance, a gas circuit system, a heating system, a gas circuit purification system, an infrared absorption detection cell, and a data receiving and processing system.
6.1.2 Analytical balance: accuracy of 0.0001 g.
6.1.3 Gas circuit system: the carrier gas is helium, which shall meet the requirements of GB/T 4844.
6.1.4 Heating system: a heating furnace, of which the heating temperature shall meet the requirements for the melting and decomposition of continuous silicon carbide fibers, the crucible degassing power shall not be lower than 6.0 kW, and the sample analysis power shall not be lower than 5.5 kW.
6.1.5 Gas circuit purification system: the air circuit purification agents are linear copper, copper oxide, magnesium perchlorate, quartz wool, and alkali asbestos. The purity of linear copper shall meet the requirements of GB/T 26017; the purity of copper oxide shall meet the requirements of GB/T 674; the specifications of magnesium perchlorate, quartz wool and alkali asbestos are all analytically pure.
9 Instrument calibration
9.1 Calibration method
Calibration methods are divided into single-point calibration and multi-point calibration. Single-point calibration is suitable for tests with a single type of sample and a wide test range of oxygen content (generally not more than 1 %). Multi-point calibration is suitable for tests with a wide test range of oxygen content; it shall select not less than 2 kinds of reference materials that can cover the test value range under normal operating conditions of the measuring system for calibration, or use a series of reference materials with different oxygen contents that are formulated by a same reference material for calibration.
9.2 Single-point calibration
9.2.1 Enter the calibration mode of the instrument.
9.2.2 Test the blank of the instrument according to 8.3 and 8.4 to obtain the blank value in the calibration mode.
9.2.3 Load 0.02 g ~ 0.04 g of reference material into the sample-carrying capsule. During the loading process, the reference material shall not come into contact with the mouth of the sample-carrying capsule and shall be placed directly on the bottom of the sample-carrying capsule, which is flattened and sealed with tweezers.
9.2.4 Test a reference material that is larger than the experimental value range under the normal operating conditions of the measuring system according to the operating instructions of the instrument. The parallel test is not less than 3 times, to obtain the test value of the reference material in the calibration mode.
9.2.5 Select the blank value in the calibration mode and the test value of the reference material to be drawn into a working curve by the data receiving and processing system, to calibrate the instrument.
9.3 Multi-point calibration
9.3.1 According to 9.2.1 and 9.2.2, test the blank of the instrument.
9.3.2 According to 9.2.3 and 9.2.4, test the reference materials with different oxygen contents from low oxygen content to high oxygen content in turn.
9.3.3 According to 9.2.5, calibrate the instrument.
9.4 Quality control and assurance
9.4.1 After the instrument is calibrated, select a reference material with the oxygen content close to the sample to be tested for verification. When the difference between Appendix A
(informative)
Precision calculation
A.1 General
The precision test of this method was performed by 6 laboratories in 2020 to determine the oxygen content of 5 levels, and each laboratory measured each level 3 times in parallel.
Calculate the repeatability limit (r) and reproducibility limit (R) according to the methods specified in GB/T 6379.2 and GB/T 6379.6.
A.2 Calculation of repeatability limit
A.2.1 The absolute difference between the two independent test results obtained under repeatability conditions shall not be greater than the repeatability limit (r). The case where it is greater than the repeatability limit (r) shall not exceed 5 %. The repeatability limit (r) is calculated according to the formula (A.1). The result is consistent with the effective digits of the arithmetic mean of the oxygen content in the sample. A.2.2 For microanalysis, when the average value of the analysis value is less than 2 times the repeatability limit, the repeatability limit is 1/2 of the analysis value. A.3 Calculation of reproducibility limit
A.3.1 The absolute difference between the two independent test results obtained under reproducibility conditions shall not be greater than the reproducibility limit (R). The case where it is greater than the reproducibility limit (R) shall not exceed 5 %. The reproducibility limit (R) is calculated according to the formula (A.2). The result is consistent with the effective number of the arithmetic mean of the oxygen content in the sample.
A.3.2 For microanalysis, when the average value of the analysis value is less than 2 times the reproducibility limit, the reproducibility limit is 1/2 of the analysis value.

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