is some of Nikola Tesla's work still classified ?

none of Tesla's work is classified, except in the minds of come conspiracy theorists.  you can find copies of all of his patents using Google patent search, and there have been many biographies (see Amazon or your library).  Many conspracy theorists do not understand the application of Maxwell's equations and for them Tesla had secret knowledge. Tesla was brilliant and was far ahead of many of his contemporaries, but not so far ahead that his "secrets" falling into the hands of our enemies is still feared by our military and still "classified".