Chemical analysis methods for non-rare earth impurities of rare earth metals and their oxides—Part 1: Determination of carbon and sulfur contents—High frequency-infrared absorption method
1Key Takeaways
This document describes methods for the determination of carbon and sulfur content in rare earth metals and their oxides. This document is applicable to the determination of carbon and sulfur content in rare earth metals and their oxides. Measuring range (mass fraction): Carbon 0.0020%~1.00%; Sulfur 0.0020%~0.20%.
2Expert Interpretation
Interpretation of GB/T12690.1-2022 standard: Introduces the application of high-frequency-infrared absorption method in the determination of carbon and sulfur content in rare earth metals and oxides, covering the method principles, equipment requirements, sample processing procedures and precision analysis.
GB/T12690.1-2022 Standard Overview
This standard specifies the method for determining the carbon and sulfur content in rare earth metals and their oxides using the high-frequency-infrared absorption method, which is applicable to the detection of samples with a mass fraction range of carbon 0.0020%~1.00% and sulfur 0.0020%~0.20%.
Method Principle
| Steps | Operation Instructions |
|---|---|
| Sample Preparation | Rare earth metal samples are made into chips or small pieces of less than 0.1g each. If necessary, they are washed with acetone and air-dried and analyzed immediately. Rare earth oxide samples are dried in an oven at 105℃ for 1h and analyzed immediately. |
| Flux addition | Add 0.2g tin flux, sample, 0.4g pure iron flux and 1.3g tungsten flux to the carbon-sulfur special crucible in sequence. |
| High temperature combustion | Introduce an oxygen flow into the high-frequency induction furnace to make the sample burn at high temperature. Carbon generates carbon monoxide and/or carbon dioxide gas, and sulfur generates sulfur dioxide gas. |
| Gas treatment | The mixed gas first enters the sulfur dioxide infrared cell to determine the sulfur content, and then undergoes catalytic oxidation, where sulfur dioxide is converted into sulfur trioxide and absorbed. The remaining gas enters the carbon infrared cell to determine the carbon content. |
Instrument and Maintenance
The main instrument is a high-frequency infrared carbon-sulfur analyzer, and its detector sensitivity requirement is 0.01μg/g. To ensure the normal operation of the instrument, the following maintenance measures need to be taken:
- Use a tube filled with caustic soda asbestos and anhydrous magnesium perchlorate to supply oxygen.
- Maintain a static flow rate when on standby.
- Install a glass wool filter or a stainless steel mesh as a dust collector, and clean and replace it when necessary.
- Regularly clean the combustion chamber, base column and filter well.
Precision Analysis
Repeatability limit (r): The mass fraction of carbon is 0.013%, and the mass fraction of sulfur is 0.0028%.
Reproducibility limit (R): The mass fraction of carbon is 0.045%, and the mass fraction of sulfur is 0.013.
Implementation suggestions
- Enterprises should configure high-frequency-infrared carbon-sulfur analyzers and related auxiliary equipment according to standard requirements.
- Operators need to undergo professional training to ensure that sample preparation and instrument operation meet specifications.
- It is recommended to participate in joint test plans regularly to verify the accuracy and precision of the method.