Zypcoat HTO

Zypcoat® HTO is a water-based coating of Hafnium Oxide (HfO2) and Titanium Oxide (TiO2) blended in the molar ratio 2/3 HfO2 to 1/3 TiO2, which allows the formation of a special solid solution of Hf-Ti-O that has the very unique expansion (CTE, coefficient of thermal expansion) property of near zero expansion 1 .  The Zypcoat HTO (66.7HfO2 * 33.3TiO2 leads to a solid solution that is a stable solid to over 2000 C with no polymorphic transormation: the solid solution exhibits electrical resistivity of circa 7×106  Ω-cm 2.   Also, the Zypcoat HTO yields a well-bonded coating when applied to most highly-refractory substrates and is non-reactive with many ceramics and alloys, solid or molten.  After heating to 1300 C – 1600 C on an Alumina substrate, the coating is over 97% HfO2 – TiO2, with the remainder being Al2O3, which is most likely also in solid solution with the Hafnia/Titania.

1. S. R. Skaggs, “Zero and Low Coefficient of Thermal Expansion Polycrystalline Oxides, ” Report LA-6918-MS, Los Alamos Scientific Laboratory of the University of California, Los Alamos, New Mexico (1977).

2. C. E. Holcombe, M. K. Morrow, D. D. Smith, and D. A. Carpenter, “Survey of Low Expanding High Melting Mixed Oxides,” Report Y-1913, Union Carbide Oak Ridge Y-12 Plant, Oak Ridge, Tennessee (1974)


Key Attributes

  • Non-reactivity with many solid or molten metals/alloys
  • Use temperature estimated to be 2000 C in all atmospheres
  • On heatup to 1300 C – 1600 C, forms unique solid solution of HfO2 – TiO2

Ideal Uses

  • Very-high-temperature areas
  • Aerospace, nuclear, and demanding applications
  • Barrier coating to prevent diffusion, reactions, and sticking of parts during heat treating