Crystallite Size Refinement of ZrB₂by High‐Energy Ball Milling

Abstract

The high‐energy ball milling behavior of a commercially available ZrB2 powder was studied by X‐ray diffractometry and transmission electron microscopy. It is shown that ball milling is very effective in obtaining nanocrystalline ZrB2 powder. Further, the crystallite size refinement occurs through repeated brittle fracture, with the final crystal size being limited by a combination of the fracture strength of particles and the compressive stress induced by collision of balls. With this mechanism, the crystallite size first decreases rapidly, then gradually, and finally approaches to an asymptotic limit as the ball‐milling time increases. Additionally, the higher the ball‐to‐powder weight ratio, the faster the decrease in the crystallite size and the smaller the ultimate crystallite size.

In situ formation of ZrB2–ZrO2 ultra-high-temperature ceramic composites from high-energy ball-milled ZrB2 powders

“…The milling was carried out in a cylindrical hardened-steel container with WC balls (6.7 mm in diameter; Union Process Inc., USA) under a ball-to-powder weight ratio of 4:1. 1 This milling condition has been proved to be effective in refining ZrB2 to nano-crystallites with ∼10 nm average size [32][33][34], as is also shown here in the transmission electron microscopy (TEM) images of Fig. 1.…”

High‐Energy Ball Milling of ZrB2 in the Presence of Graphite

“…Although comminution via ball milling and subsequent addition of carbon have yielded very encouraging results for the pressureless sintering of ZrB 2 powders, further enhancement can be expected if the addition of carbon is uniformly distributed at nanosized powders. Recently, it is shown that high‐energy ball milling of pure ZrB 2 powder using shaker mills can produce submicrometer agglomerates of many cold‐welded nanoparticles 9 . One of the advantages of high‐energy ball milling is its capability to produce finer particles than conventional ball milling.…”

ZrB2–SiC Nano‐Powder Mixture Prepared Using ZrSi2 and Modified Spark Plasma Sintering

“…Figure shows the microstructure of the synthesized powder with changing synthesis temperature and composition. The as‐milled powder was crushed into 100–150 nm in size, but was heavily agglomerated by cold welding during high‐energy milling . The M1 specimen retained the morphology after heating at 750°C for 30 min, at which condition the reaction did not occur [Fig.…”