Composition and Thermal Stability of Al- and Zr-Containing Gels Prepared by a Sol–Gel Synthesis Using N,N-Dimethyloctylamine and Acetylacetone

Resumo

Al- and Zr-containing sols intended for producing Al₂O₃ and ZrO₂ nanocoatings, respectively, were prepared by a sol–gel process using N,N-dimethyloctylamine (DMOA) and acetylacetone (acacH). Aluminum and zirconyl nitrates were used as metal precursors. The DMOA/Al and DMOA/Zr molar ratios were 1 and 2, respectively, and the acacH/DMOA molar ratio was 1.5 in both cases. The sols were synthesized at a temperature of 80–90°C and then were evaporated at 90–95°C to a gel state. The resultant gels were characterized by differential thermal analysis, differential scanning calorimetry, and electron impact mass spectrometry. Measurements in the temperature range 20–500°C in air and Ar showed that the Zr-containing material was more thermally stable (decomposition temperature of 304–308°C) than its Al-containing analog (decomposition temperature of 225–230°C). According to the mass spectrometry analysis data, the gels contained metals as acetylacetonate complexes having strong M–O bonds and coordinated molecular DMOA. The nature of the metal was shown to influence both the thermal stability of the gel in which it is present in a chemically bound state and the mechanisms of the processes involved in its thermolysis.