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Unformatted text preview: age - 12- T he T iSZ p owder used in the experiments for this thesis
was prepared thermally in an elongated quartz ampoule using
method iii). Stoichiometric amounts of titanium sponge ( 4 t o 4 0 m esh) and elemental sulfur powder were placed in a well
cleaned quartz tube (sealed at one end) under an atmosphere
of dry argon. Particulate titanium sponge ( 4 t o 4 0 m esh) was used instead of titanium wire or pellets because the
sponge has a h igher surface area to weight ratio which
promotes higher reactivity and thus a f a s t e r , more complete
reaction. Wittingham ( 33) s tates that using particulate titanium sizes smaller than 4 0 m esh resulted in
uncontrollable reaction rates which causes localized heating
resulting in crystal imperfections. The use of particulate
sizes larger than 4 m esh resulted in unacceptably (or very)
slow reaction rates.
A d ry argon atmosphere was used when transferring the particulate titanium to the reaction tube i n o rder to
minimize contamination through the absorption of water vapor
by titanium. The quartz tube containing the titanium and sulfur was then evacuated (to less than
sealed. torr) and The dimensions of the ampoule were 4 .0 c m. in diameter by 4 0 c m. in length. The end of the ampoule containing the mixture of elemental titanium and sulfur was
elevated b y 5 c m. (Fig. 6 ) a nd placed in the two zone
horizontal furnace. T o physically separate the two constituents, the elevated end of the ampoule (containing Page -12aFigure 6 T hermal growth of T i S 2 powders. PREPARATION o f TiS2 POWDER
. ... . TITANIUM SPONGE
4 to 4 0 MESH . ..
S ULFUR VAPOR S ULFUR P age - 13- t he titanium and sulfur mixture) was heated to 1 2 5 C w hile
the opposite end of the ampoule was held at room temperature.
The liquid sulfur ( M . P . = 1 1 9 C ) f iowed t o the cooler end of the ampoule carrying only a small fraction of the particulate
titanium with it. The elemental titanium and sulfur were separated in order to control the vapor pressure of the
sulfur surrounding the particulate titanium and thus control
the reaction rate by varying the temperature o f t he licqui...
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This note was uploaded on 10/08/2009 for the course CME MAT E 630 taught by Professor Dr. during the Fall '09 term at University of Alberta.
- Fall '09