NexTech Materials is developing sealing systems for intermediate temperature solid oxide fuel cells. In an ongoing Phase II SBIR, NexTech has developed and synthesized several different sealing composites that demonstrate significant performance advantages over conventional compressive seals. Composite seals offer a number of advantages over single-phase glass seals. The chemical compatibility, thermal expansion, and mechanical properties can be tailored through the selection of appropriate glassy and crystalline phases. Compared to glass-ceramic seals, where the crystalline phase nucleates and grows from the starting glass, the crystalline component of composites can be selected for its properties, morphology or chemical behavior. In addition, the content and orientation of the crystalline phase can be controlled during formulation and fabrication. In Phase I the feasibility of composite seals was demonstrated; in Phase II the focus of the effort has moved toward optimization and electrochemical validation of seal performance.

The composite seals are designed to exhibit thermo-mechanical and chemical compatibility with electrode, electrolyte and interconnect materials for intermediate temperature SOFCs. The goal the program is to develop seals that will have general applicability to the SECA vertical team designs of SOFC systems and are tailored for operating temperatures at 800C. The added benefits of reduced cost and improved reliability to current standards are some of the key features of the textured sealing composites. This presentation documents progress in seal design and evaluation in NexTech's current program.