ISO 21068-2:2024

Overview - ISO 21068-2:2024 (Chemical analysis for SiC/Si3N4/SiON/sialon)

ISO 21068-2:2024 specifies standardized analytical methods for the chemical analysis of raw materials and refractory products containing silicon‑carbide (SiC), silicon‑nitride, silicon‑oxynitride and sialon. The standard covers procedures to determine volatile components, total carbon, free carbon, silicon carbide, total and free silicon, and free and surface silica, enabling consistent, comparable laboratory results for quality control and material certification.

Key topics and technical requirements

• Scope and terminology
  • Definitions and applicability to raw materials and refractory products containing SiC, Si₃N₄, Si‑oxynitride and sialon.
• Volatile components
  • Gravimetric determination methods including loss on drying at 250 °C and loss on ignition in argon.
• Carbon analysis
  • Methods for total carbon by combustion (resistance furnace with lead borate or tin; induction furnace with metallic powder).
  • Free carbon determination by direct and indirect methods; includes reference to correction procedures when SiC oxidizes.
• Silicon carbide and silicon
  • Indirect and combustion methods for SiC (including a combustion at 750 °C variant).
  • Total silicon and free silicon determination, including pretreatment with hydrochloric acid and hydrogen evolution techniques.
• Silica analysis
  • Determination of free silica (SiO2) and surface silica, with sample preparation, reagents and calculation methods.
• Detection techniques
  • Use of coulometry, infrared CO2 detection, and thermal conductivity detectors as specified.
• Quality & reporting
  • Expression of results, precision data (Annex A), certified reference materials (Annex B) and test report requirements.

Applications and who uses it

ISO 21068-2:2024 is intended for:

• Refractory manufacturers and raw material suppliers for product specification and process control
• Analytical laboratories performing chemical characterization of SiC‑ and Si‑based refractory materials
• R&D teams developing new refractory compositions and heat‑resistant ceramics
• Certification bodies and quality assurance groups that require traceable, comparable test data

Practical benefits include reliable quality control, repeatable test methods for batch acceptance, and harmonized reporting for international trade and regulatory compliance.

Related standards

• Part of the ISO 21068 series (chemical analysis of raw materials and refractory products).
• Developed from and aligning with earlier standards such as EN 12698‑1/2 and previous ISO 21068‑1 editions, as noted in the document foreword.

Keywords: ISO 21068-2:2024, chemical analysis, silicon‑carbide, silicon‑nitride, silicon‑oxynitride, sialon, refractory products, total carbon, free carbon, silicon carbide, free silica.