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We present a new approach, namely ball milling, to synthesize amorphous boron nitride (a-BN), The amorphization kinetics are revealed by X-ray diffractometry (XRD), high-resolution transmission electron microscopy (HRTEM), and electron energy loss spectroscopy (EELS), HRTEM investigations indicate that, in the early stage of milling, the thick sp(2) layers are sliced into many thinner sheets because of cleavage;along the basal planes, In the intermediate stage of milling, deformation is accommodated primarily by simultaneous shearing along the basal planes. As a result of sustained shearing, a number of defects, such as stacking faults, (0002) [11 (2) over bar 0] twinning, simultaneous shearing of lattice planes, and half Frank loops with Burgers vectors of 1/2[0001], are introduced in the hexagonal BN (h-BN) grains. Simultaneous shearing also causes significant change in the lattice symmetry of most grains. In the final stage of milling, the fiberlike tightly bonded sp2 sheets are broken and refined further, until a nanocrystalline and amorphous mixture is formed. XRD of the sample mined for 180 b exhibits an amorphous halo pattern; nevertheless, HRTEM demonstrates that the end product is essentially a nanocrystalline and amorphous mixture. The grain sizes of the nanocrystals are <3 nm, and their stacking is turbostratic. EELS investigations of the a-BN indicate that bonding is :primarily sp2, but a small fraction of sp(3) a-BN is also found, which is assumed to be the nuclei of the cubic phase (c-BN) in the high-pressure and high-temperature experiments and thus facilitates the hexagonal to cubic transition, The present a-BN fabrication method can provide an effective way to facilitate the synthesis of sintered bulk c-BN materials.