A thermodynamic study of the zirconium-sulfur, titanium-sulfur and hafnium-sulfur systems in the disulfide-trisulfide region

<p>"A static method was used to study the equilibria which exist between the higher sulfides of zirconium and sulfur at temperatures from 700° to 1000 °C. Both disulfide and trisulfide have been identified by chemical analysis and X-ray diffraction. There exists a two-phase region of 'ZrS₂' and 'ZrS₃'. The composition limit of the homogeneous disulfide phase appears to exist between ZrS_1.90 and ZrS_2.00. The lower composition limit of the homogeneous region of the trisulfide phase was established as ZrS_2.75.</p> <p>An experimental method of Blitz and co-workers, i.e., the use of evacuated horizontal tubes unequally heated at both ends with a temperature gradient, was adopted for this study. The mixture of sulfur and sulfide was heated until equilibrium was attained. Temperatures from 119° to 445 °C for liquid sulfur were used for the sulfur end of the tube. The resulting zirconium sulfide was then analyzed. The standard free energy change was calculated from the data.</p> <p>An experimental study has been conducted to determine the equilibrium behavior of the system Sr - S - H₂. 'ZrS₂' - 'ZrS₃' two-phase mixtures were heated in the temperature range from 500° to 700 °C in a circulating type equilibrium apparatus. The system was studied by equilibrating H₂ - H₂S gas mixtures with the condensed sulfide phases. The equilibrium gas mixtures were analyzed with a Fisher Gas Partitioner.</p> <p>The standard linear free energy equation for the reaction ZrS₂ (s) + H₂S (g) = ZrS₃ (s) * H_e (g) was derived from the results and was calculated to be :<br /> ΔF° = - 15.46 T + 11,585</p> <p>This equation determines the stability of the zirconium sulfide phases when they are subjected to hydrogen reduction. In a dynamic method, hydrogen was circulated over the heated sulfide until equilibrium was attained.</p> <p>An attempt was made to extend both experimental methods of investigation - the static method of sulfur equilibration in the furnace with temperature gradient and the dynamic method of hydrogen reduction in the circulating type of apparatus - to the Ti - S and the Hf - S systems. The heat of reaction and standard free energy change for the hafnium sulfides were calculated from the experimental results. Limited data were obtained for the titanium sulfides"--Abstract, pp. ii-iii</p>

Name thesis:degree_name

Ph. D. in Metallurgical Engineering

Grantor

University of Missouri at Rolla

Year dc:date.available

2016

Author dc:creator

• Vermaut, Norbert Achilles

• Metallurgy

Repository record dc:identifier

https://scholarsmine.mst.edu/doctoral_dissertations/466

OAI identifier oai:identifier

oai:scholarsmine.mst.edu:doctoral_dissertations-1468