is David Publishing Company legit?
Anyone who contacts you to publish is bad news.  My advice is to stick to journals from ACS, APS, and ACerS.  Maybe MRS or IEEE.  There are a few decent pubs in materials from Elsevier and Wiley, but even then you need to know who they are.  Don't submit something to a journal you don't know.  

A dedicated conference proceedings is a different kettle of fish (like if this compay was retained to do conference proceedings), but even then I would try to give them some portion of or repackaging of work you publish in "real journals".

I can't find anything on the web from them either.  Which is bad also.  (Although if you included any links in your letter that would help us.)