hmm, ferrites may mean something different across the pond, but I always have refered to Ferrites as the Ferrite beads you see on cables like monitors and data cables in order to supress the noise they produce. They are the little tubular pieces that are on the ends of cables and contain a ferrite bead that the cable goes through the middle of.
Now Ferrites are used cuz they have inductance so maybe what ferrite means to you is that it is an Inductor or a Choke, in which case yah you can make a circuit that uses an Inductor and a switching circuit in order to step 5v up to 10-12V. It can be difficult to master however you could use a 555 timer and a transitor/mosfet in order to achieve the effect you desire. It is called a Step-up Switching power supply, or a Boost power supply, and there are many dedicated chips that do the switching job for you, however as with many of those things they are surface mount and hard to prototype with.
If you want to give me more info on your power requirements I can look into finding you a solution, however be forwarned usually the switching powersupply design is far from simple
EDIT: now that I have thought about it, you may have been thinking about a joule thief which uses a ferrite bead for the core of the inductor you wind at home.
