DC-DC Voltage Doubler
A couple of points:
1) I guess what you are trying to design here is a boost converter. While it is often called a DC/DC converter, the conversion itself is AC/AC. Basically, you create a square wave out of the DC voltage and then upconvert and rectify it afterwards. Almost no one designs those from scratch. If you need a simple voltage doubler, I would get a chip from Digi-Key:
http://www.digikey.com/product-search/en/integrated-circuits-ics/pmic-voltage-regulators-dc-dc-switching-regulators/2556570

2) you mention a current spec (5A/10A) for the motor, it is not clear from your post how it is related to the higher voltage you are trying to create here.