Papers by Keyword: Bead Milling

Abstract: The main objective of this study was to prepare bead milled-silica nanoparticles (SiO₂) as reinforcing materials for transparent hard coating films. SiO₂ dispersed in Dowanol PM without any stabilizer was used as a main component in the nanocomposite hard coating films to improve hardness of Poly methyl methacrylate (PMMA) sheets. However, the major challenge in hard coating formulation is the dispersion of nanoscale SiO₂ particles. Bead milling machine (MiniCer, NETZSCH, Germany) equipped with different sizes of zirconia (ZrO₂) beads (0.1, 0.5, and 1.0 mm) was used for dispersing 40wt% SiO₂ in Dowanol PM to achieve target sizes of 200, 500, and 800 nm. The dispersed nanoparticles were characterized by UV-visible spectroscopy for their optical transmission, transmission electron microscopy (TEM) for particle morphologies, and dynamic light scattering technique (DLS) for the particles sizes. The milled-SiO₂ nanoparticles were stable in Dowanol PM as suspensions with their particles sizes closed to the target sizes. The 200-nm suspension showed the longest storage time without any aggregate formation. Whereas, the dispersed nanoparticles suspensions with the particles size >500 nm formed agglomerates during storage. The SiO₂/MTMS nanocomposite coating film was then prepared coated milled-SiO₂ suspension in Dowanol PM on PMMA sheets. The film with 200 nm SiO₂ showed the highest transparency (92% at 550 nm) which was like the uncoated PMMA sheets. At thickness of 3-microns, SiO₂/MTMS nanocomposite films could improve pencil hardness of PMMA sheets from <H to 3H.

Abstract: The high-pure alpha-alumina powders with some agglomerate were treated by bead milling and their sintering behaviors were studied in this paper. During the treatment, the effect of different types and different amounts of dispersants was also investigated. It was shown that optimum dispersant content was 0.5% citric acid and optimum milling time is 6 hours. The sintering property of alumina powder after bead milling was significantly improved. Their relative density after sintering at 1500 degrees can reach 99.3% while the raw powders’ can only reach 90% at same condition.