scope:

This part of ISO 21068 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 g) above.

The items of chemical analysis described in ISO 21068, Parts 1 to 3 are as follows:

1) loss on drying (LOD);

2) loss on ignition (LOI);

3) total carbon, C_total;

4) free carbon, C_free;

5) silicon carbide, SiC;

6) free silicon (Si_free);

7) free aluminium (Al_free);

8) free magnesium (Mg_free);

9) free iron (Fe_free);

10) silicon(IV) dioxide (SiO₂);

11) aluminium oxide (Al₂O₃);

12) iron(III) oxide (Fe₂O₃);

13) titanium(IV) oxide (TiO₂);

14) calcium oxide (CaO);

15) magnesium oxide (MgO);

16) sodium oxide (Na₂O);

17) potassium oxide (K₂O);

18) chromium(III) oxide (Cr₂O₃);

19) zirconium oxide (ZrO₂);

20) boron oxide (total boron calculated as B₂O₃);

21) nitrogen;

22) oxygen;

23) nitrides (undifferentiated: Si₃N₄, AlN, BN, sialon, oxy-nitrides, etc.).

ISO 21068-4 describes XRD methods for the determination of mineralogical phases typically apparent in nitride and oxy-nitride bonded silicon carbide refractory products.