Investigation of Reaction Mechanism In Ti/C System: Influence of High Energy Ball Milling

Thursday, October 20, 2011: 9:10 AM
M100 D (Minneapolis Convention Center)
Ya-Cheng Lin, Khachatur V. Manukyan and Alexander S. Mukasyan, Chemical and Biomolecular Engineering, University of Notre Dame, Notre Dame, IN

The influence of High Energy Ball Milling (HEBM) on the stoichiometric (1: 1 molar ratio) mixture of titanium and graphite powders milled at room temperature under argon atmosphere with ball to powder ration 40:1 at 650 rpm is discussed. Crystal structures and phases were characterized by X-ray diffractometry (XRD) and energy dispersive X-ray spectroscopy (EDS) analysis. Microstructure of the initial and as-milled samples was investigated by SEM and internal structures characterized by focused ion beam (FIB) techniques. Ignition characteristics and effective activation energy measurements were carried out by, the so-called, Electro Thermal Explosion (ETE) method [1]. Special attention was paid on the microstructure variations with respect to self-ignition temperatures and reaction kinetics for media obtained at different milling durations.

For example, analysis of the specific surface area (BET) showed that after 2 min of such milling the specific surface area of the reactive media significantly increases to ~100 m2/g, being only 3 m2/g for initial mixture. At this stage, XRD and SEM studies revealed complete amorphorization of the graphite powder. It was also shown that Ti/C laminated composite particles start to form as early as after 3 min of HEBM. This transformation leads to corresponding decrease of self-ignition temperatures from 1933 K (melting point of titanium) to 1800 K. The formation of TiC-phase nucleolus (~20 nm) was observed after 5 minutes of treatment. The self-ignition temperatures further decreases to ~1500 K for samples after 7.5 min of milling time. Finally, it was shown that the nano-scale (~500 nm) TiC powder is produced after 9.5 min of process time. Reaction mechanism in Ti and C system after such treatments is also proposed and discussed.

[1] A. S. Shteinberg, Y.-C. Lin, S. F. Son, A. S. Mukasyan. “Kinetics of High Temperature Reaction in Ni-Al System: Influence of Mechanical Activation” J. Phys. Chem. A, 2010, 114 (20), pp 6111–6116.


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