Abstract

In order that carbide coatings could be prepared, graphite cuvettes were (1) placed in liquid TiCl<sub>4</sub>, MoCl<sub>5</sub>, or WCl<sub>6</sub> under reduced pressure to fill the void space in the graphite with metal chloride; (2) allowed to soak for 24 h in water to hydrolyze the metal chloride; (3) heated for 1200 s at 120°C and 10 s at 500°C in an electrothermal atomizer to dry the metal hydroxide and form the oxide; and (4) heated to 1800°C for 30 s to form the carbide. The formation of metal carbide was confirmed by gravimetry and x-ray diffraction. X-ray diffraction also indicated the presence of oxide on Ti- and W-treated cuvettes and of multiple metal carbide species on Mo- and W-treated cuvettes. Scanning electron microscopy of Ti-treated cuvettes showed the presence of small particles of a discrete carbide phase. The carbide-treated cuvettes last longer than conventional graphite and show enhanced sensitivities for carbide-forming elements determined by graphite furnace atomic absorption. Their analytical characteristics do not differ significantly from carbide-treated cuvettes prepared by other procedures. It is hypothesized that the primary effect of the metal carbide is to seal the graphite, causing it to be less porous.

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