 Nickel @-@ based superalloys of rhenium are used in the combustion chambers , turbine blades , and exhaust nozzles of jet engines . These alloys contain up to 6 % rhenium , making jet engine construction the largest single use for the element , with the chemical industry 's catalytic uses being next @-@ most important . Because of the low availability relative to demand , rhenium is among the most expensive of metals , with an average price of approximately US $ 2 @,@ 750 per kilogram ( US $ 85 @.@ 53 per troy ounce ) as of April 2015 ; it is also of critical strategic military importance , for its use in high performance military jet and rocket engines . 
