Combustion front dynamics in the combustion synthesis of refractory metal carbides and di-borides using time-resolved X-ray diffraction
| Autor: | Joe Wong, E. M. Larson, Ronald Frahm, P. A. Waide |
|---|---|
| Rok vydání: | 2006 |
| Předmět: |
Boron Compounds
Nuclear and High Energy Physics Hot Temperature Time Factors Transducers Analytical chemistry Mineralogy Combustion Specimen Handling Carbide chemistry.chemical_compound X-Ray Diffraction Phase (matter) Tantalum boride Instrumentation Inorganic compound chemistry.chemical_classification Radiation Chemistry Refractory metals Equipment Design Equipment Failure Analysis Kinetics Metals X-ray crystallography Melting point |
| Zdroj: | Journal of Synchrotron Radiation. 13:326-335 |
| ISSN: | 0909-0495 |
| DOI: | 10.1107/s0909049506020796 |
| Popis: | A compact diffraction-reaction chamber, using a 2-inch photodiode array detector, has been employed to investigate the chemical dynamics at the combustion front of a selected series of refractory metal carbides and di-borides from their constituent element reactants as well as binary products from B4C as a reactant. These systems are denoted as (i) M + C {yields} MC; (ii) M + 2B {yields} MB{sub 2}; and (iii) 3M + B{sub 4}C {yields} 2MB{sub 2} + MC, where M = Ti, Zr, Nb, Hf or Ta. Time-resolved X-ray diffraction using intense synchrotron radiation at frame rates up to 10 frames s{sup -1} (or 100 ms frame{sup -1}) was employed. The combustion reactions were found to complete within 200-400 ms. In contrast to the Ta + C {yields} TaC combustion system studied earlier, in which a discernible intermediate sub-carbide phase was first formed, reacted further and disappeared to yield the final TaC product, no intermediate sub-carbide or sub-boride was detected in the current systems. Combustion for the Ti, Zr and Hf systems involved a liquid phase, in which the adiabatic temperatures T{sub ad} are well above the melting points of the respective reactant metals and have a typical combustion front velocity ofmore » 5-6 mm s{sup -1}. The Nb and Ta systems have lower T{sub ad}, involving no liquid phase. These are truly solid combustion systems and have a lower combustion front velocity of 1-2 mm s{sup -1}. The current study opens up a new avenue to chemical dynamics and macrokinetic investigations of high-temperature solid-state reactions.« less |
| Databáze: | OpenAIRE |
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