The crystal structure of α-TiCl3 and the reticular disorder introduced by ball-milling

By X-ray powder diffraction methods the crystal structures of α-TiCl3 and of the products obtained by dry ball-milling activation of this form were studied. TiCl3 microcrystals show initially a structural disorder in the positions of titanium atoms and the successive mechanical activation introduces into the structure some stacking faults, mainly associated to ±60° rotations of the triple layers Cl[BOND]Ti[BOND]Cl. The structural investigation has been carried out by an accurate fit of observed X-ray patterns to those calculated in correspondence of structures containing well-defined disordered sequences and of likewise well-defined crystallite sizes. Like γ-TiCl3 and MgCl2, α-TiCl3 is very sensitive to mechanical activation, which improves the performances of these three compounds when they are employed as catalysts, or supports for catalysts, in Ziegler-Natta polymerization processes.