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Synthesis, characterization and physical properties of Al-Cu-Fe quasicrystalline plasma sprayed coatings

Description: Our lab has been working with plasma spraying of both high pressure gas atomized (HPGA) and cast and crushed quasicrystal powders. A major component of this research includes comparative studies of PAS coatings formed with starting powders prepared by both techniques. In addition, a thorough investigation of the effects of starting powder particle size on coating microstructure is included. During the course of the overall research, an interest developed in forming Al-Cu-Fe materials with finer grain sizes. Therefore, a brief study was performed to characterize the effect of adding boron to Al-Cu-Fe materials prepared by different techniques. In addition to characterizing the microstructural features of the above materials, oxidation and wear behavior was also examined.
Date: November 9, 1995
Creator: Daniel, S.
Partner: UNT Libraries Government Documents Department

Effect of a fluorinated nickel surface on the decomposition of perfluorodiethoxymethane

Description: Perfluoropolyethers (PFPEs) are a commercial class of lubricants widely used in computer and aerospace industries. This is a study of the degradation of a perfluorinated ether in the presence of a metal fluoride. Perfluorodiethoxymethane (PFDEM) is a PFPE analog. Temperature programmed desorption shows no contribution of PFDEM toward nickel fluoride on an NiF{sub 2} surface obtained by CF{sub 3}I adsorption. Higher coverages of nickel fluoride do not show any evidence of NiF{sub 2} contribution from PFDEM. The results do not agree with the idea that a fluorinated surface might induce decomposition of PFPEs, leading to addition fluoride formation on the surface. The metal fluoride bond strength is not a legitimate concern for decomposition of PFE lubricants. Impurity in PFPEs might be the cause of initial surface fluoridation leading to breakdown of PFPEs which could cause additional metal fluoride formation. It is clear that the reaction of PFPEs with metals does not involve a direct formation of a simple M-F bond; results do not show any C-F bond cleavage of the fluorinated ether and do not support a proposed autocatalytic mechanism.
Date: November 9, 1995
Creator: Sreevidya, S.
Partner: UNT Libraries Government Documents Department