US Patent 7874347 Heat pipe with hydrophilic layer and/or protective layer

A heat pipe (1) includes a shell (20), a protective layer (10) formed on an outer surface of the shell, a wick (30) and a hydrophilic layer (40) sequentially formed on an inner surface of the shell, and a working fluid contained in the shell. A material of the shell is metal, such as copper, aluminum, or a copper-aluminum alloy. The protective layer is formed of nanomaterials, such as carbon nanotubes, nano-sized copper particles, nano-sized aluminum particles, or nano-sized particles of a copper-aluminum alloy. The wick is made from a mixture of carbon fibers and carbon nanocapsules. The hydrophilic layer is made from nanomaterials, for example, titanium dioxide, zinc oxide, alumina, or any mixture thereof.