Zum System W/O/J. IV. Der Chemische Transport von Wolfram und Wolframdioxid

Abstract

Wolframdioxid wird durch Jod im Temperaturgefälle (1000 → 800 °C) mit der reversiblen, endothermen Reaktion WO2,f + J2,g = WO2J2,g transportiert. Wolfram wird durch Jod nur transportiert (800 → 1000 °C), wenn Wasserspuren zugegen sind. Die thermodynamische Diskussion unter Berücksichtigung der Gasmolekeln WO2J2, WO2(OH)2, H2O, H2, HJ, J1 und J2 ergibt, daß dieser Transport durch die exotherme Reaktion W + 2H2O,g + 6J1,g(3J2) = WO2J2,g + 4HJ,g beherrscht wird.

Ordered Mesoporous Crystalline Mo-Doped WO2 Materials with High Tap Density as Anode Material for Lithium Ion Batteries

“…In the past two decades, numerous reports on various other materials have also demonstrated that fabricating nanostructured materials is an efficient way of overcoming the problems that arise from the slow Li + solid diffusion rate . However, the general synthesis routes for crystalline WO 2 materials, including solid reaction, vapor deposition, chemical vapor transport, and hydrogen reduction, only lead to a dense film structure or to irregular particles with large particle sizes. ,− Almost no nanostructured WO 2 materials have been reported, except for a WO 2 nanorod material prepared by a hot-filament metal vapor deposition method that requires a super high synthesis temperature of 1500 °C . Facile synthesis of WO 2 materials with well-defined nanostructures is still a great challenge.…”

Developments in Measuring and Calculating Chemical Vapor Transport Phenomena Demonstrated on Cr, Mo, W, and Their Compounds

“…The transport of tungsten in iodine-containing systems 317,379 is an example of a W-containing exothermic transport system and should be particularly mentioned. Tungsten can only be transported by means of iodine if water is present besides the halogen.…”

“…By using the halogens (Cl 2 , 392,393 Br 2 , 190 I 2 317,329,332,379,[394][395][396] ) as transport agents tungsten dioxide migrates to the zone of lower temperature of the ampule. The transport of WO 2 proceeds via WO 2 X 2 (X ) Br, I) and can be described by the equilibrium Kleber et al 393 reported an endothermic transport using X 2 ) Cl 2 (T 2 ) 1000-850 °C, T 1 ) 950-750 °C).…”

“…Experimental results of the transport system WO 2 / I 2 are presented in several papers. 317,329,332,379,[394][395][396] Dettingmeijer et al reported transport rates up to 14 mg/h. 379 Experimental results as reported by Scha ¨fer et al were m ˘exp (max) ) 86 mg/h (c(I 2 ) ) 3.05 mg/cm 3 , 1000 f 800 °C).…”

“…317,329,332,379,[394][395][396] Dettingmeijer et al reported transport rates up to 14 mg/h. 379 Experimental results as reported by Scha ¨fer et al were m ˘exp (max) ) 86 mg/h (c(I 2 ) ) 3.05 mg/cm 3 , 1000 f 800 °C). 317 Moreover, a small amount of W 18 O 49 (WO 2.72 ) is also deposited at T 1 .…”