<P> In the 1950s and 1960s, the Soviet Union pioneered the use of titanium in military and submarine applications (Alfa class and Mike class) as part of programs related to the Cold War . Starting in the early 1950s, titanium came into use extensively in military aviation, particularly in high - performance jets, starting with aircraft such as the F - 100 Super Sabre and Lockheed A-12 and SR - 71 . </P> <P> Recognizing the strategic importance of titanium, the U.S. Department of Defense supported early efforts of commercialization . </P> <P> Throughout the period of the Cold War, titanium was considered a strategic material by the U.S. government, and a large stockpile of titanium sponge was maintained by the Defense National Stockpile Center, which was finally depleted in the 2000s . According to 2006 data, the world's largest producer, Russian - based VSMPO - AVISMA, was estimated to account for about 29% of the world market share . As of 2015, titanium sponge metal was produced in six countries: China, Japan, Russia, Kazakhstan, the US, Ukraine, and India . (in order of output). </P> <P> In 2006, the U.S. Defense Advanced Research Projects Agency (DARPA) awarded $5.7 million to a two - company consortium to develop a new process for making titanium metal powder . Under heat and pressure, the powder can be used to create strong, lightweight items ranging from armour plating to components for the aerospace, transport, and chemical processing industries . </P>

What is the oxidation number of the titanium atom in tio 2 ​