ISO 21068-1:2024

This document gives definitions and specifies techniques for the preparation of samples for the chemical analysis of silicon-carbide-containing raw materials and refractory products including:
a) SiC raw materials;
b) graphite brick containing silicon carbide;
c) silicon carbide brick (includes the bricks containing silicon nitride, silicon oxynitride, sialon);
d) refractories containing carbon and/or silicon carbide mixed with clay;
e) refractories containing carbon and/or silicon carbide mixed with silica (and fused silica);
f) refractories containing carbon and/or silicon carbide mixed with high alumina material;
g) refractories containing carbon and/or silicon carbide mixed with magnesia (and dolomite);
h) refractories containing carbon and/or silicon carbide mixed with chrome mineral or magnesia-chrome materials;
i) refractories containing carbon and/or silicon carbide except those described in a) to h) above.

The items of analysis described in ISO 21068-2, ISO 21068-3 and ISO 21068-4 are as follows:
— loss on drying (LOD);
— loss on ignition (LOI);
— total carbon, Ctotal;
— free carbon, Cfree;
— silicon carbide, SiC;
— free silicon (Sifree);
— free aluminium (Alfree);
— free magnesium (Mgfree);
— free iron (Fefree);
— silicon(IV) dioxide (SiO2);
— aluminium(III) oxide (Al2O3);
— iron(III) oxide (Fe2O3);
— titanium(IV) oxide (TiO2);
— calcium oxide (CaO);
— magnesium oxide (MgO);
— sodium oxide (Na2O);
— potassium oxide (K2O);
— chromium(III) oxide (Cr2O3);
— zirconium(IV) oxide (ZrO2);
— boron oxide (total boron calculated as B2O3);
— nitrogen;
— oxygen;
— nitrides (undifferentiated: Si3N4, AlN, BN, sialon, oxy-nitrides, etc.);
— mineralogical phases (XRD-methods).