MATERIALS / APPLICATION AREA::  Helicon has decades of experience in each of designing, fabricating, and testing surface coatings for numerous extreme environments. We implement multi-layer and graded high-temperature thin film barrier designs typically so as to allow a technically-critical component to withstand high-temperature and corrosive environments that would, normally, only be associated with certain refractory ceramics, thus obtaining a unique combination of useful properties.   Barrier films for high temperature applications are implemented as means for preventing diffusion processes that eventually lead to shorten device lifetime, unstable operation, or both.  Helicon has a long history in high-temperature (500C to >1200C) thin film barrier technologies, utilized successfully in applications ranging from high-temperature-gradient interfaces, locally or rapidly heated crystal-growth interfaces, corrosion barriers in high-temperature catalyzers, electrolyzers, and high-temperature fuel cells.  We have experienced know-how and capabilities in the thin film process, and development metrics, for of an array of complimentary refractory dielectrics, conductors, mixed conductors, semiconductors, and other high-temperature compounds that are utilized in non-equilibrium conditions, steep temperature gradients, high-cycling applications, and corrosive environments.   Our barrier and solid oxide technologies have been successfully implemented for use in a number of NASA martian and lunar mission applications, solar cell production reactors, as well as in providing successful benchmarks in the world's largest high-temperature fuel cell companies. Our capabilities and experience in this area utilize multiple refractory materials that involve learning curves, including dense compounds of Borides, Carbides, vacuum diffusion bonding and post-deposition process regimes. Helicon has a long history of participating in high-temperature diffusion barriers as applied to high-temperature fuel cells and electrolyzers.  We have been participating in developing a series of new solid oxide fuel cell concepts with thin-film designs providing exceedingly high thermo-mechanical shock resistance appropriate for fast-start applications.

Figure 1:  Annular SOFC concept that Helicon has been a primary contributer in developing and modelling, providing improved reliability and temperature cycling lifetime.

Figure 2: Helicon conducts various forms of computer modeling, including finite-element analysis (FEA) for temperature gradients and stress in studies of annular SOFC.

EXAMPLE APPLICATION (Solid-Oxide Fuel Cells and related devices): The specific example given here is representative of our work in high-temperature barrier coatings utilized in numerous NASA space programs for oxygen generation for Mars exploration, as well as for multiple programs in solid oxide fuel cell (SOFC) applications, high-temperature fuel cells providing the highest efficiency available in any known fuel cell design.   Our work in this specific type of high-cycling barrier multilayers goes back twenty years, when we were already accustomed to designing for cycle temperatures in the 800-1250 Celsius region.  Our Helicoat technology was utilized by the founding team of Bloom Energy immediately prior to forming a start-up (we received a patent on this technology, which is fully disclosed in our 2001 patent appication).   .

Figure 3 : Solid-Oxide based oxygen generation device utiizing the "Helicoat" corrosion/diffusion barrier design and developed by Helicon. Underlying metal interconnect fabricated for NASA Mars missions by AME dept, University of Arizona. YSZ-based oxygen genertion device utilizing Helicon's "Helicoat", successfully demonstrated (

Figure 4: reliability data; system impedance measurements in temperature cycling.

The approach we introduced and utilized in the adjacent Figure is our long-time "Helicoat" technology, utilizing a diffuse barrier layer in conjunction with a layer combination providing an inert oxygen barrier function.  Helicon has similarly designed and successfully developed high-temperature diffusion and corrosion barriers for a diverse variety of applications.  We utilize a unique combination of novel approaches, our cross-disciplinary materials expertise, and our experience in the diverse fields in which we have performed high-temperature thin film development work.

Combined tribological/high-heat: As the requirement of thermo-mechanical stability implies, tribological properties, high-temperature capabilities, and application-specific chemical stability are inter-related issues.  Diverse forms of ballistic, cutting-tool, and wear surfaces utilized in extreme environments are a related application-specific area where these concerns also converge.  In many wear surfaces, such as in automotive, certain aerospace applications, and cutting tools, these challenges are more readily met when, essentially, metallic refractory compounds, such as conducting oxide, carbide, nitride, and boride mixtures, can be utilized.  However, additional fundamental challenges are encountered when such coatings are dual-function, such as incorporating specific optical or dielectric functions.

modeling of temperature gradient on radome

Helicon Thin Film Systems, Ltd

                       ADDITIONAL DIFFUSION BARRIER DATA ON:

Zone Melt Recrystalization barriers

Passivation Layers for Austenitic & Ferritic/Martensitic steels  

Mixed conductors and graded catalytic layers