ABSTRACTTwo multi-component sol-gel compositions were developed and compared to several commercially available high-temperature glasses. All were then used and characterized as protective coatings for intermetallic titanium aluminide.The sol-gels were studied as thin film coatings and the commercial glasses were studied as enameled coatings. Attention was given to (1) the effect of the application temperature on the original microstructure of the metal, and (2) the role of interfacial conditions between the glass and metal in cyclic and isothermal thermal cycles between ambient temperature and 760°C (1400°F).
ABSTRACTSurface properties of BaTiO3 which contain different Ba/Ti ratios were examined by FTIR spectroscopy. Most of the carbonates on the surfaces of these powders were removed by heat treatment at 1200°C. However, it was more difficult to remove the carbonates from the powder with a higher ratio of Ba/Ti. Analysis of the heat treated, aged powders in humid air showed that the barium-excess powder recovered carbonates within several hours. In contrast, titanium-excess powders took a longer time, indicating that barium ion concentration is a reaction-control parameter. It was found that oleic and stearic acids were effective in retarding the degradation of the BaTiO3 powders. They also made the dissolution rate of the powders in water considerably slower.
Thin film coatings of (Ca0.6, Mg0.4)Zr4(PO4)6 (CMZP) on Si3N4, and SiC substrates, including porous SiC used in ceramic filters, were investigated using sol-gel and dip coating techniques. The coating thickness, ranging from 1 to 5 μm, was found to vary with the selected precursors and their concentrations in the solution. When applied to Si3N4 and SiC, CMZP coatings exhibit good thermal shock resistance and greatly improved alkali corrosion resistance. For porous silicon carbide, homogeneous, crack-free coatings were formed on both the outer surface and the interior sections of the pore walls. The CMZP coatings on Si3N4 and SiC exhibit good thermal shock resistance. The CMZP coating greatly improved the alkali corrosion resistance of Si3N4 and SiC.
Surface structural features and optical analysis of nanostructured Cu-oxide thin film coatings coated via the sol-gel dip coating method