• The effects ofpH and electrical bias on abrasion of alumina in aqueous solutions

      Uhlmann, Donald R.; Fruitman, Clinton, 1946- (The University of Arizona., 1990)
      Various coolant chemicals are known to have enhancing and suppressing effects on wear and the quality of finish, but little has been understood about the nature of these effects. Studies were performed to examine the effects of pH and surface bias on wear, subsurface damage, and the various theories of chemical interaction with the wear process. Results of this examination of wear suggest that chemical adsorbates can play a significant role in wear fracturing. Previous observations of plastic mechanisms in brittle wear have lead tribologists to suggest that chemically induced changes in plasticity are the cause of these effects. Instead, this thesis contends occurrence of plastic effects to be by-product of localized hydrostatic compression and insufficient stress intensity to cause fracture. Crack rates and stress intensities required for fracture to occur are known to vary with adsorption.
    • Modelling of dynamic wetting phenomena

      Uhlmann, Donald R.; Zelinski, Brian J. J.; Denesuk, Matthew, 1965- (The University of Arizona., 1990)
      A general dynamic wetting model is presented in which surface and gravitational driving energies are balanced against energy lost through bulk viscous dissipation. Behavior is described in terms only of independently measurable quantities, with no adjustable parameters. Additionally, the model can be expressed so as to predict liquid viscosity as a function of dynamic wetting behavior. Application of the model to a lead-silicate liquid on a gold substrate demonstrate excellent agreement of the model with experiment. The general framework of the model is especially amenable to the incorporation of other physico-chemical processes which may impact dynamic wetting phenomena. Examples are given which extend the model to specific cases where substrate roughness and/or substrate dissolution are important. Additionally, the dynamic wetting model is extended to porous substrates, accounting for the effects of composite interface formation and depletion of the liquid via capillary flow.
    • Reverse Engineering of Ancient Ceramic Technologies from Southeast Asia and South China

      Vandiver, Pamela B.; Kivi, Nicholas; Potter, Barrett G.; Killick, David; Uhlmann, Donald R. (The University of Arizona., 2019)
      Ceramic technologies of Myanmar and South China were analyzed in order to determine characteristic traits and technological origins. Given Myanmar’s geographically strategic position between China and Southwest Asia, its ceramic history needs to be reevaluated among the distinct traditions of Southeast Asia. The ceramics of Myanmar show evidence of imitation China and Southwest/Central Asia using locally sourced materials, giving support to Dr. Myo Thant Tyn’s theory of the convergence of the Chinese and Southwest/Central Asian ceramic traditions in Myanmar. Seven ceramic technologies of Myanmar were analyzed: celadons, black-glazed jars (lead-barium and lead-iron-manganese glazes), brown ash glaze ware, green and opaque white-painted glaze ware and turquoise-glazed, coarse-bodied white earthenware. Celadon glazes and brown glazes were made with ash, similar to the Chinese celadon tradition. Green-and-white opaque ware utilized copper-green colorant glaze decoration with tin and lead oxides as opacifying agents on low-fired oxidized bodies. Both these traditions are probably derived from Southwest Asian ceramic and glass traditions. High-soda, copper-turquoise glazes on coarse white earthenware bodies are influenced by Southwest and Central Asian low-fire ceramic and glass traditions. Black-glazed, “Martaban”-style storage jars were variable in body and glaze technology and are still of indeterminable technological origin. A phase-separated glaze was analyzed that had a similar phase-separated appearance to northern Chinese Jun ware. Additionally, two black-glazed ware types from South China with vertical streaking phase separation were analyzed: Xiba kiln of Sichuan and Jianyang kilns of Fujian. The recently discovered and excavated Xiba kiln made experimental and striking stoneware bowls similar to Jianyang “hare’s fur” ware. Reverse engineering the manufacture of Xiba kiln ware determined that Xiba was an innovative site that imitated Jianyang ware aesthetically but not technologically. Xiba and Jianyang do not have any connection to the six Burmese glaze styles, however, future analyses of Southeast Asian ceramics can use the data for comparison and variability research.