Here is an interesting problem. How do you analyze refractory materials? What if you are making materials that could be used as a crucible raw material? How do you digest refractory materials down to homogeneous solutions that themselves need to be contained in something even more refractory?

Obviously, it is done all of the time. Methods like AA, ICPOES, ICPMS, GDMS, etc., are all useful in quantitating or revealing mass spectra of materials. Of the above list, only GDMS can be applied to solid samples. The AA and ICP methodologies require homogeneous solutions. This can be problematic.

X-ray techniques like XRF and XRD are useful for solids characterization as well. Of these two, only XRF is useful in the absence of distinct crystal phases. XRD detects crystal phases and can be used to good end with the crystallograpic database that is available for the identification of solid substances. In contrast, XRF, X-ray fluorescence, detects elements easily down to sodium, and lighter with a bit more difficulty. Hand held XRF units are available for the price of a low end BMW that will alow the user to point the business end of the unit to a material and identify the elements present.

A useful company to get to know in this arena is Inorganic Ventures. These folks are extremely knowledgeable and supply stock and custom standards for flame and ICP methods. The trick to the analysis and characterization of refractory metal oxides in the category of RO2, R2O3, and RO, is to have reliable standards on hand as well as a choice of fluxes. Fluxing at high temperature is often critical to the digestion of refractory oxides.  Fluxes are molecular inorganic salts that may be acidic or basic and may or may not be oxidizing. 

If you started out as an organikker like me, there will be a period of slight adjustment to the notions of what are regarded as acids and bases at 1000 C. A flux is a substance that melts and dissolves an inorganic solid, usually through the digestion of the material in question. A melt is produced inside a crucible within a muffle furnace.  This melt can be poured into a mold to produce a button or the material may be allowed to solidify in the crucible followed by aqueous acid dissolution.

In addition to acidic and basic fluxes, there is the matter of melting temperature and the need for a eutectic mixture. A variety of compositions can be prepared to provide a melt temperature suitable for a particular need.  Volatility may be a problem, requiring adjustment of conditions.

Advertisements