Usable reactor materials must be capable of withstanding high temperature corrosive environments and rapid temperature variations.  The objective of my work in this area is to first, develop a testing and modeling system to characterize thermal stresses indicative of concentrated solar energy systems.  The second objective is to use the predicted stress cycles to estimate material lifetimes and optimize material selection. The final purpose of this work is to use ALD to create composites which are optimally suited for high temperature solar thermal applications and to design concentrated solar systems that reduce thermal stresses. From this we hope to be able to create reactor systems that can withstand the harsh conditions indicative of concentrated solar power.