Overview
EN ISO 21068-3:2024 - Chemical analysis of raw materials and refractory products containing silicon‑carbide, silicon‑nitride, silicon‑oxynitride and sialon (ISO 21068‑3:2024) specifies validated analytical techniques for determining total nitrogen, nitrogen calculated as silicon nitride, total oxygen, and metallic and oxidic constituents in silicon‑based raw materials and refractory products. Endorsed by CEN in 2024 (supersedes EN ISO 21068‑3:2008), this standard is aimed at laboratories and manufacturers needing reproducible, comparable analytical results for quality control and material specification.
Key topics and technical requirements
- Scope and applicability: Analysis methods targeted at SiC, Si3N4, Si‑oxynitride and SiAlON raw materials and refractory products.
- Nitrogen and oxygen determination:
- Combined determination using analysers with thermal conductivity (TC) and infrared (IR) absorption detection.
- Fusion decomposition methods for total nitrogen.
- Kjeldahl distillation method for total nitrogen.
- Calculation procedures for converting total nitrogen to Si3N4-equivalent content.
- Metallic and oxidic constituents:
- Soluble iron: extraction with hydrochloric acid followed by ICP‑OES measurement.
- Free (metallic) aluminium: hydrogen‑generating method.
- Acid‑soluble aluminium and magnesium procedures and measurement guidance.
- Determination of elemental impurities by alkaline melt fusion or acid pressure decomposition.
- Analytical essentials: required reagents, apparatus, sample preparation, calibration, procedure steps, measurement, calculation, and precision statements for each method.
Practical applications
- Quality control and incoming inspection of silicon‑based refractory raw materials (SiC, Si3N4, SiON, SiAlON).
- Product specification and certification used by manufacturers and suppliers to demonstrate compliance with material requirements.
- Process control and R&D for optimizing refractory formulations where N/O content and metallic/oxidic impurities affect performance.
- Failure analysis and troubleshooting where accurate impurity profiling (Fe, Al, Mg, etc.) informs root‑cause investigations.
Who should use this standard
- Materials and quality laboratories performing chemical analysis on refractories.
- Refractory product manufacturers, raw material suppliers, and formulators.
- Research and development teams in ceramics and high‑temperature materials.
- Accreditation bodies and procurement/specification engineers who require standardized test methods.
Related standards
- EN ISO 21068‑3:2024 is Part 3 of the ISO 21068 series; other parts of the series provide complementary analytical methods for silicon‑based refractories. Users should consult normative references cited in the standard for linked methods and instrumentation guidance.
Keywords: EN ISO 21068‑3:2024, chemical analysis, silicon carbide, silicon nitride, sialon, silicon‑oxynitride, nitrogen determination, oxygen determination, ICP‑OES, Kjeldahl, fusion decomposition, refractory materials.
