Hi! we usually prepare the sample for XRF with lithium tetraborate in a Pt crucible to form a glass bead. The problem is that when the sample has SiC, the crucible reacts with it. So, I know that there are methods for oxidizing the sample prior to the fusion, to protect the Pt crucible. I would need recommendations of which method to use and where to find it. Any advise?
Thank you!
Never done it myself, but I've come across references for SiC and oxidation with peroxides, Li2CO3 or Na2CO3 is indeed recommended. Claisse also tried with a bed of flux around the sample, to protect the crucible.
I think you may find your answer here : https://www.iso.org/obp/ui#iso:std:iso:16169:ed-1:v1:en
Silicon carbide is often considered as acidic refractory. While the lithium tetraborate flux is able to dissolve most refractories, it is not particularly suitable to dissolve this and other acidic refractories.
You may consider to (slowly) melt the silicon carbide refractory sample (say, approx. 0.5 g) in covered platinum crucible, previously lined with Na2CO3 ― to prevent direct Pt contact with SiC (approx. 4:1, Na2CO3:SiC, wt:wt), using sodium carbonate + potassium nitrate flux (approx. 40:7:1, Na2CO3:KNO3:SiC, wt:wt:wt), beneath a layer of borax ― (Na2O+K2O):B2O3 approx. 1:1 mol:mol ― as vitrifying flux component.
Ref.: O.H. Kriege, "The analysis of refractory borides, carbides, nitrides, and silicides”, Report LA-2306, Los Alamos Scientific Laboratory, 1959, p. 30.
Thank you both for your answers. We'll evaluate them and try them to see what happens. Have a good week!
- Badges
- Science topic
- Similar topics
- Physical Sciences
- Materials Science
- Materials
- Inorganic Materials
- Ceramics
- Glass