Sublimation Kinetics of Zirconium Tetrachloride (ZrCl4) for Producing Zr Sponge

Non-isothermal sublimation kinetics of low-volatile materials is more favorable over isothermal data when time is a crucial factor to be considered, especially in the subject of detecting explosives. In this article, we report on the in-situ measurements of the sublimation activation energy for 2,4,6-trinitrotoluene (TNT) continuous nanofilms in air using rising-temperature UV-Vis absorbance spectroscopy at different heating rates. The TNT films were prepared by the spin coating deposition technique. For the first time, the most widely used procedure to determine sublimation rates using thermogravimetry analysis (TGA) and differential scanning calorimetry (DSC) was followed in this work using UV-Vis absorbance spectroscopy. The sublimation kinetics were analyzed using three well-established calculating techniques. The non-isothermal based activation energy values using the Ozawa, Flynn–Wall, and Kissinger models were 105.9 ± 1.4 kJ mol−1, 102.1 ± 2.7 kJ mol−1, and 105.8 ± 1.6 kJ mol−1, respectively. The calculated activation energy agreed well with our previously reported isothermally-measured value for TNT nanofilms using UV-Vis absorbance spectroscopy. The results show that the well-established non-isothermal analytical techniques can be successfully applied at a nanoscale to determine sublimation kinetics using absorbance spectroscopy.

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Pressure Effect on the Kinetics of Reaction Between Solid NaCl and ZrCl4 or HfCl4 Vapors

Canadian Journal of Chemistry ◽

10.1139/v71-478 ◽

1971 ◽

Vol 49 (17) ◽

pp. 2885-2890 ◽

Cited By ~ 5

Author(s):

P. Pint ◽

S. N. Flengas

Keyword(s):

Sodium Chloride ◽

Single Crystals ◽

Constant Temperature ◽

Pressure Effect ◽

Heterogeneous Reaction ◽

Zirconium Tetrachloride ◽

Hafnium Tetrachloride ◽

Diffusion Controlled ◽

Kinetics Of Reaction ◽

Kinetics Of

The kinetics of reaction between single crystals of sodium chloride and zirconium tetrachloride and hafnium tetrachloride vapors, to form sodium hexachlorozirconate and sodium hexachlorohafnate, respectively, have been investigated as a function of the tetrachloride pressures at a constant temperature of 485 °C. The rate of formation of Na2ZrCl6 is kinetically more favorable. The heterogeneous reaction is diffusion controlled, with the rate of diffusion depending on the availability of Cl− vacancies.

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The Sublimation Kinetics of GeSe Single Crystals

Zeitschrift für anorganische und allgemeine Chemie ◽

10.1002/zaac.19754110213 ◽

1975 ◽

Vol 411 (2) ◽

pp. 182-192 ◽

Cited By ~ 19

Author(s):

E. A. Irene ◽

H. Wiedemeier

Keyword(s):

Single Crystals ◽

Sublimation Kinetics ◽

Kinetics Of

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Sublimation Kinetics of Zirconium Tetrafluoride

Advanced Materials Research ◽

10.4028/www.scientific.net/amr.1019.398 ◽

2014 ◽

Vol 1019 ◽

pp. 398-405

Author(s):

C.J. Pretorius ◽

A.D. Pienaar ◽

P.L. Crouse ◽

H.F. Niemand

Keyword(s):

Chemical Properties ◽

Inert Atmosphere ◽

Nuclear Industry ◽

Nuclear Grade ◽

Accurate Estimation ◽

Chemical Waste ◽

Hazardous Chemical ◽

Zirconium Tetrafluoride ◽

Sublimation Kinetics ◽

Kinetics Of

An important step of a new process being developed for the beneficiation of the mineral zircon (Zr (Hf)SiO4) to produce nuclear grade zirconium (Zr) metal, is the separation of the Zr from the hafnium (Hf). Zr ores typically contain between 1 and 3% Hf , whereas the use of Zr metal in the nuclear industry requires a Hf content <100 ppm, owing to its high neutron-capture cross section. The separation step is therefore key in the preparation of nuclear grade Zr, which is considered to be very difficult due to the various similarities in their chemical properties. The preparation of hafnium free zirconium relies on the traditional wet separation systems, for example solvent extraction systems. In contrast to the traditional aqueous chloride systems, Necsa focusses on dry fluoride-based processes. Dry processes have the advantage of producing much less hazardous chemical waste. In the work reported her, separation is achieved by sublimation/de-sublimation in the tetrafluoride form. The tetrafluoride is prepared by fluorination of plasma dissociated zircon (PDZ or Zr (Hf)O2•SiO2) with ammonium bifluoride (ABF). The separation involves the selective sublimation of the two tetrafluorides in an inert atmosphere under controlled conditions, and subsequent similarly selective desublimation. An accurate estimation of the sublimation rates the zirconium tetrafluoride (ZrF4) and hafnium tetrafluoride (HfF4) as a function of temperature is required since this forms the basis of the development of a sublimation model to determine whether the concept under consideration is theoretically possible. The sublimation kinetics of ZrF4is reported in this paper.

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