GB/T 34520.8-2021
Test methods of continuous silicon carbide fibers—Part 8：Oxygen content (English Version)
- Standard No.
- GB/T 34520.8-2021
- Language
- Chinese, Available in English version
- Release Date
- 2021
- Published By
- General Administration of Quality Supervision, Inspection and Quarantine of the People‘s Republic of China
- Latest
- GB/T 34520.8-2021
- Scope
- This document specifies the sample preparation, sample test, and test result calculation for the determination of oxygen content in continuous silicon carbide fibers by the 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 fiber and matrix. Refer to this document for the oxygen content test of other ceramic fibers.
- Introduction
Standard Technical Background and Evolution
With the widespread application of continuous silicon carbide fiber in the aerospace field, its oxygen content, as a key impurity indicator, directly affects the high-temperature performance of the material. The 7 mechanical properties test standard system released in 2017 was expanded in 2021 to supplement the oxygen and carbon content detection methods, forming a complete 9-part standard system. This part of the standard was jointly drafted by the National University of Defense Technology and other institutions, and the inert gas fusion-infrared absorption method was used to solve the problem of insufficient accuracy of traditional chemical analysis methods.
Analysis of core test principles
Steps Reaction process Technical parameters Melting decomposition The fiber reacts with carbon in a graphite crucible to generate CO/CO? Heating power ≥5.5kW Gas transmission High purity nitrogen carrier flow (GB/T4844) Flow accuracy±0.1L/min Infrared detection 4670nm(CO), 4260nm(CO?) dual-channel analysis Sensitivity 0.01ng/g Actual cases show that when testing silicon carbide fiber with an oxygen content of 0.5%, the system needs to be equipped with a linear copper purifier (GB/T26017) to eliminate trace oxygen interference in the carrier gas and ensure test stability.
Key operating specifications
Sample preparation requirements
- Desizing: Remove surface treatment agent according to GB/T34520.1
- Fiber crushing: 1-3mm short fiber (constant weight error ≤0.0001g)
- Drying conditions: 105-110℃ oven to constant weight
Instrument calibration system
Calibration type Applicable scenarios Quality control Single point calibration Routine detection of oxygen content ≤1% Weekly standard material verification Multi-point calibration Wide range test (0.001-5%) Need to cover the concentration range to be tested
Implementation suggestions
Laboratory configuration plan
- Environmental control: temperature (23±2)℃, humidity (50±10)% (GB/T1446)
- Equipment selection: It is recommended to be equipped with Pulse heating infrared detector, degassing power ≥6.0kW
- Consumables management: The purity of nickel capsules must comply with GB/T26016, and the graphite crucible must be spectrally pure
Precision control
According to Appendix A, the repeatability limit calculation formula is r=0.0165+0.0422w. When testing 0.1% oxygen content, the allowable deviation should be ≤0.0207%. It is recommended to use high-purity silicon carbide standard material for daily quality control.
GB/T 34520.8-2021 Referenced Document
- GB/T 1446 Fiber-reinforced plastics composites-The generals for determination of properties
- GB/T 26016 High purity nickel*， 2021-12-31 Update
- GB/T 26017 High purity copper
- GB/T 34520.1 Test methods for continuous silicon carbide fiber—Part 1：Size content of filament yarn
- GB/T 4844 Pure helium,high pure helium and ultra pure helium
- GB/T 674 Chemical reagent powdered copper oxide*， 2024-09-29 Update
- GB/T 8170 Rules of rounding off for numerical values & expression and judgement of limiting values
GB/T 34520.8-2021 history
- 2021 GB/T 34520.8-2021 Test methods of continuous silicon carbide fibers—Part 8：Oxygen content