The synthesis of titanium diboride by carbothermal reduction of TiO2, B2O3 and C powder mixtures milled for 48, 100 and 200 h was investigated. The resultant powders were examined after isothermal annealing by X-ray diffraction (XRD) and X-ray photoelectronic spectroscopy (XPS) to determine the synthesis mechanism. During milling, a high-pressure phase, TiO2(II), transformed from anatase-TiO2 was observed and crystallization of amorphous-B2O3 was found to occur. After milling, a submicron lamelliform particle with a cladding structure was obtained. The synthetic reaction was observed to be finished as low as 1200 degrees C for the 200 h-milled powder. In this research, two reaction paths have been found that TiB2 was formed through intermediates TiBO3 and TiO. The predominance of TiBO3 increased and the reactive temperature of the synthesis of TiB2 decreased with prolonged milling time. (C) 2014 Elsevier B.V. All rights reserved.