Francis S. Galasso

Aluminum oxide coating on nickel substrate by metal organic chemical vapor deposition

Aluminum oxide thin films were coated onto nickel substrates via chemical vapor deposition. The aluminum oxide was produced by pyrolysis of a metal acetylacetonate precursor. This reaction was done at relatively low temperatures, from 435 to 550 °C to deposit a thin film of aluminum oxide. The coating provided protection against isothermal oxidation at elevated temperatures. Resistance to oxidation was obtained for all of the coated substrates. Surface morphology, however, changed when heated for prolonged time. Samples coated at 500 and 550 °C are effective up to 900 °C whereas samples coated at 435 °C were good up to 800 °C. The metal oxide compositions and phases were studied by X-ray diffraction and EDAX. The surface properties of the deposited thin films were investigated with scanning electron microscopy.

Chemical vapor deposition TiN coating on silicon carbide coated boron fibers

TiN was deposited as a coating onto SiC coated B fiber from TiCl4 and NH3 by chemical vapor deposition technique at 650 °C. Several analytical techniques such as scanning electron microscopy (SEM), x‐ray photoelectron spectroscopy, and x‐ray diffraction were employed to study the TiN coating and the coating‐fiber interface. The bulk of the coating is TiN with small amounts of titanium oxynitride. Depth profile by Auger electron spectroscopy showed that the diffusion zone of the TiN coating into the fiber is narrow, which indicates weak interfacial bonding. The structural morphology, as revealed by SEM, shows a globular structure transforming into a star‐shaped morphology down the length of the fiber. Finally, the TiN coated fibers showed higher tensile strength than the as‐received fiber.

Double Interface Coatings on Silicon Carbide Fibers

Interface coatings on fibers are important in ceramic matrix composites. In addition to providing toughness, the interface coating must also protect the reinforcing ceramic fibers from corrosive degradation. A double interface coating has been applied onto silicon carbide fibers. The double interface coating is comprised of a combination of nitride and oxide coatings. Among the nitrides, boron nitride and titanium nitride were utilized. These nitrides were deposited by CVD. The metal oxides of choice were aluminum oxide and zirconium oxide which were applied onto the nitride coatings by MOCVD. The phases on the coated fibers were determined by XRD. The surface coating microstructures were observed by SEM. The effect of the coatings on the tensile strengths was determined by Instron tensile strength measurements.

Sol-Gel AL2O3 Coatings on SiC Fiber

Coating of SiC (BP-SIGMA) fibers with alumina by a sol-gel process did not cause degradation even after heating to 1000°C in air for 24 h. X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), Auger electron spectroscopy (AES) and scanning electron microscopy (SEM ) methods were used to study the coating fiber interface.

Interaction of Titanium with SiC Coated Boron Fiber

SICABO fiber, which is one of the silicon carbide coated fibers, has been found to be more stable than BORSIC fiber in titanium matrix composites because SICABO fiber has excess carbon in the SiC layer which was determined by an AES depth profile study. Tensile strength data also show that the SICABO fiber has a higher tensile strength after heating in titanium during hot pressing and chemical vapor deposition processing. Ti 5 Si 3 and TiSi phases were identified from XRD studies on titanium coated BORSIC, but there was no TiSi phase identified in the titanium coated SICABO fiber. AES depth profile results have shown that the BORSIC-Ti has a broad interdiffusion zone.