Pickett, Ammon T. (2008-08). THE INFLUENCE OF WATER ON THE DEGRADATION AND WEAR OF AL2O3 SURFACES. Master's Thesis. Thesis uri icon

abstract

  • As alumina plays ever more important roles in advanced technologies, such as substrates for in vivo biological sensors, catalysts for water purification and components of novel fuel devices, it is exposed to various environments. These environments lead to wear and degradation due to chemical and mechanical forces. Macroscale tribological tests including the scratch test and indentation are unable to analyze nanoscale properties due to their limited sensitivity. Today, nanotribologists incorporate three main tools to analyze nanoscale tribological properties: atomic force microscopy (AFM), the nanoindentor and surface force apparatus. Of these, AFM is the instrument of choice due to the sensitivity to and diversity of surface properties analyzed in a single setting. Through adhesion measurements and scratch testing under known loads the AFM was used to analyze the effect of OH- on the degradation of the alumina surface. Fourier transform infrared spectroscopy (FTIR) and AFM were also used to analyze the stability of self-assembled monolayers (SAMs) on the alumina surface. Through scanning a region of the surface with a defined force in an aqueous environment, the tribochemical surface properties were found. The pressure required to induce degradation of the first O-Al layer (~2 ?) ranged from 3.10 GPa at a pH 3 to 1.58 GPa at pH 10. Further analysis of adhesion across the surface and within a defect region exposed significant changes in the forces of adhesion as the alumina surface experienced wear. At pH 3, 5, 7, and 10 the adhesion was approximately double that of the defect free surface. Two well known molecules were examined for their ability to protect the surface from bond rupture due to the catalytic effect of OH-. SAMs of octadyclephosphonic acid (OPA) and Octadycletrichlorosilane (OTS) were assembled on the alumina surface. FTIR spectra indicated well ordered monolayers formed from each molecule. The exposure of OPA to aqueous environments of pH >7 lead to the degradation of the SAM. OTS, on the other hand, demonstrated significantly more resilience to degradation as indicated through FTIR and AFM analysis.
  • As alumina plays ever more important roles in advanced technologies, such as
    substrates for in vivo biological sensors, catalysts for water purification and components
    of novel fuel devices, it is exposed to various environments. These environments lead to
    wear and degradation due to chemical and mechanical forces. Macroscale tribological
    tests including the scratch test and indentation are unable to analyze nanoscale properties
    due to their limited sensitivity. Today, nanotribologists incorporate three main tools to
    analyze nanoscale tribological properties: atomic force microscopy (AFM), the
    nanoindentor and surface force apparatus. Of these, AFM is the instrument of choice
    due to the sensitivity to and diversity of surface properties analyzed in a single setting.
    Through adhesion measurements and scratch testing under known loads the AFM was
    used to analyze the effect of OH- on the degradation of the alumina surface. Fourier
    transform infrared spectroscopy (FTIR) and AFM were also used to analyze the stability
    of self-assembled monolayers (SAMs) on the alumina surface.
    Through scanning a region of the surface with a defined force in an aqueous
    environment, the tribochemical surface properties were found. The pressure required to induce degradation of the first O-Al layer (~2 ?) ranged from 3.10 GPa at a pH 3 to 1.58
    GPa at pH 10. Further analysis of adhesion across the surface and within a defect region
    exposed significant changes in the forces of adhesion as the alumina surface experienced
    wear. At pH 3, 5, 7, and 10 the adhesion was approximately double that of the defect
    free surface.
    Two well known molecules were examined for their ability to protect the surface
    from bond rupture due to the catalytic effect of OH-. SAMs of octadyclephosphonic acid
    (OPA) and Octadycletrichlorosilane (OTS) were assembled on the alumina surface.
    FTIR spectra indicated well ordered monolayers formed from each molecule. The
    exposure of OPA to aqueous environments of pH >7 lead to the degradation of the SAM.
    OTS, on the other hand, demonstrated significantly more resilience to degradation as
    indicated through FTIR and AFM analysis.

publication date

  • August 2008