In 2005, an investigation conducted on three nanoscale attrition millers in Taiwan revealed that all three had undergone metal nanopowder explosions in the past. This research was aimed at determining the relationships between the particle diameter of an aluminum nanopowder and its maximum explosion pressure (P max ), maximum rate of pressure rise ((dP/dt) max ), minimum explosion concentration (MEC), and minimum ignition energy (MIE) by 20 liter apparatus and 1.2-L Hartmann apparatus. The results revealed that 35-nm aluminum powder has a P max of 7.3 bar and deflagaration index (K St ) of 349 bar·m/s, in 100-nm aluminum powder, P max of 12.5 bar and K St of 296 bar·m/s and 40-μm aluminum powder, P max of 5.9 bar and K St of 77 bar·m/s. The value of (dP/dt) max for the 35-nm aluminum powder is 4.5 times that for the 40-μm aluminum powder. The 35-nm, 100-nm, and 40-μm powders have MEC values of 40, 50, and 35 g/m 3 , respectively. The 35-nm and 100-nm powders both have MIEs less than 1 mJ, while the 40-μm powder has an MIE of 59.7 mJ.

In the experiment, nanoparticles of 35 nm Al and 100 nm Al powders, respectively, formed particles with average sizes of 161 nm and 167 nm in agglomeration. The characteristics of dust cloud explosions with the two powder sizes, 35 nm and 100 nm, revealed considerable differences, as shown here: (dp/dt)max-35 nm= 1254 bar/s, (dp/dt)max-100 nm= 1105 bar/s; Pmax-35 nm= 7.5 bar, Pmax-100 nm= 12.3 bar, and MEC-35 nm= 40 g/m3, MEC-100 nm= 50 g/m3. The reason of Pmax-35 nmvalue is smaller than Pmax-100 nmmay be due to agglomeration. From an analysis of the explosive residue, the study found that nanoparticles of 35 nm Al powder became filamentous strands after an explosion, where most of 100 nm Al nanoparticles maintained a spherical structure, This may be because the initial melting temperature of 35 nm Al is 435.71°C, while that for 100 nm Al is 523.58°C, higher by 87.87°C. This study discovered that explosive property between the 35 nm Al and 100 nm Al powders after agglomeration were different.