Abstract
The wide size range and high tendency to agglomerate of in-situ TiB(2) particles in reinforced Al matrix composites introduce great difficulties in their size characterization. In order to use a nanoparticle size analyzer (NSA) to obtain the precise size distribution of TiB(2) particles, a controlled size characterization process has been explored. First, the extraction and drying processes for TiB(2) particles were optimized. In the extraction process, alternated applications of magnetic stirring and normal ultrasound treatments were proven to accelerate the dissolution of the Al matrix in HCl solution. Furthermore, freeze-drying was found to minimize the agglomeration tendency among TiB(2) particles, facilitating the acquisition of pure powders. Such powders were quantitatively made into an initial TiB(2) suspension. Second, the chemical and physical dispersion technologies involved in initial TiB(2) suspension were put into focus. Chemically, adding PEI (M.W. 10000) at a ratio of m(PEI)/m(TiB2) = 1/30 into the initial suspension can greatly improve the degree of TiB(2) dispersion. Physically, the optimum duration for high-energy ultrasound application to achieve TiB(2) dispersion was 10 min. Overall, the corresponding underlying dispersion mechanisms were discussed in detail. With the combination of these chemical and physical dispersion specifications for TiB(2) suspension, the bimodal size distribution of TiB(2) was able to be characterized by NSA for the first time, and its number-average diameter was 111 ± 6 nm, which was reduced by 59.8% over the initial suspension. Indeed, the small-sized and large-sized peaks of the TiB(2) particles characterized by NSA mostly match the results obtained from transmission electron microscopy and scanning electron microscopy, respectively.