The drive toward higher efficiencies and performance in energy production and transportation equipment has posed a continual challenge for the materials scientists and engineers involved in design and construction of such equipment. The laws of thermodynamics specify that increased efficiency can best be achieved by the use of the highest possible temperatures. As the desired operating temperature of a system increases, the limitations of the materials being used for construction of the system place an upper limit of the temperatures and thus the efficiencies that can be achieved.