Titanium Dust can be smelted to make Titanium Ingot.
This item can be obtained only if you have other mods installed alongside Galacticraft, for example IndustrialCraft2 or Thermal Expansion. It is obtained by grinding, crushing or pulverizing Titanium Shard, Titanium Ingot, or Compressed Titanium in the machines those mods offer.
Titanium Dust is specifically included for compatibility with IndustrialCraft2 where it is a secondary product of processing Aluminum Ore through the full IndustialCraft2 ore processing chain. Aluminum Ore produces Tiny Pile of Titanium Dust as a secondary product. 9 x Tiny Pile of Titanium Dust can be crafted into one Titanium Dust.