Iii r eacting elemental titanium and sulfur directly

Info iconThis preview shows page 1. Sign up to view the full content.

View Full Document Right Arrow Icon
This is the end of the preview. Sign up to access the rest of the document.

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...
View Full Document

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.

Ask a homework question - tutors are online