Combustion Front Dynamics in the Combustion Synthesis of Refractory Metal Carbides and Di-borides using Time-Resolved X-ray Diffraction

Journal Article · Sun Jan 01 04:00:00 EST 2006 · J. Synch. Rad.

DOI:https://doi.org/10.1107/S0909049506020796· OSTI ID:914128

Wong, J; Larson, E; Waide, P; Frahm, R

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 of 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.

• Research Organization: Brookhaven National Laboratory (BNL) National Synchrotron Light Source
• Sponsoring Organization: Doe - Office Of Science
• DOE Contract Number: AC02-98CH10886
• OSTI ID: 914128
• Report Number(s): BNL--78696-2007-JA
• Journal Information: J. Synch. Rad., Journal Name: J. Synch. Rad. Vol. 13; ISSN 0909-0495; ISSN JSYRES
• Country of Publication: United States
• Language: English

Related Subjects

43 PARTICLE ACCELERATORS
CARBIDES
COMBUSTION
MELTING POINTS
NSLS
PHOTODIODES
REFRACTORY METALS
SYNCHROTRON RADIATION
SYNTHESIS
VELOCITY
X-RAY DIFFRACTION
national synchrotron light source