Abstract: An insulating mat for an exhaust gas treatment device thermally stable to at least 900° C., wherein the insulating mat contains inorganic fibers uniformly coated with a metal oxide including at least one of aluminum oxide, titanium oxide, zirconium oxide, or mixtures thereof; wherein said fibers are uniformly coated with the metal oxide by precipitating metal hydroxide corresponding to the metal oxide on the fibers, followed by converting the precipitated metal hydroxide to the metal oxide. A method of increasing the thermal stability of inorganic fibers for use in an exhaust gas treatment device insulating mat including the inorganic fibers, including uniformly coating the fibers with a metal oxide of at least one of aluminum oxide, titanium oxide, zirconium oxide or mixtures thereof by a chemical precipitation process.

Abstract: An insulating mat for an exhaust gas treatment device thermally stable to at least 900° C., wherein the insulating mat contains inorganic fibers uniformly coated with a metal oxide including at least one of aluminum oxide, titanium oxide, zirconium oxide, or mixtures thereof; wherein said fibers are uniformly coated with the metal oxide by precipitating metal hydroxide corresponding to the metal oxide on the fibers, followed by converting the precipitated metal hydroxide to the metal oxide. A method of increasing the thermal stability of inorganic fibers for use in an exhaust gas treatment device insulating mat including the inorganic fibers, including uniformly coating the fibers with a metal oxide of at least one of aluminum oxide, titanium oxide, zirconium oxide or mixtures thereof by a chemical precipitation process.