Browsing by Subject "sulfur"

Now showing 1 - 2 of 2
  • Thumbnail Image
    Item
    The Effects of Surfactants on Colloidal, Nanoparticulate, and Dissolved Sulfur
    (Office of the Vice Chancellor for Research, 2016-04-08) Kurek, Martin; Druschel, Greg; Gilhooly, William P., III
    Elemental sulfur is generally insoluble in water unless in the presence of a surfactant. This phenomenon was investigated by Steudel and Holdt in 1988 by filtering mixtures of sulfur, water, and surfactants through a 0.45 micron filter; however, since then sulfur nanoparticles smaller than 0.45 microns have been detected. The smaller than expected particle size suggests that the distribution of elemental sulfur in water with surfactants may be partitioned into colloidal, nanoparticulate, and truly dissolved components. Experiments have been conducted measuring the sulfur solubility in water with several chemical surfactants and varying filter sizes smaller than 0.45 microns. These experiments were conducted under equilibrium conditions with the solubility being measured using HPLC and square wave voltammetry. Kinetic studies detailing the solubility of sulfur with the surfactants over time have also been investigated. Data regarding the size and occurrence of sulfur nanoparticles present in water and the surfactants has been collected as well to give a complete description of the system under examination. Sulfur isotope fractionation of the dissolved sulfur species is also an interesting component of the system that is currently being investigated using stable isotope ratio mass spectrometry of 34S.
  • Thumbnail Image
    Item
    Role of disordered bipolar complexions on the sulfur embrittlement of nickel general grain boundaries
    (Nature Research, 2018-07-17) Hu, Tao; Yang, Shengfeng; Zhou, Naixie; Zhang, Yuanyao; Luo, Jian; Department of Mechanical and Energy Engineering, School of Engineering and Technology
    Minor impurities can cause catastrophic fracture of normally ductile metals. Here, a classic example is represented by the sulfur embrittlement of nickel, whose atomic-level mechanism has puzzled researchers for nearly a century. In this study, coupled aberration-corrected electron microscopy and semi-grand-canonical-ensemble atomistic simulation reveal, unexpectedly, the universal formation of amorphous-like and bilayer-like facets at the same general grain boundaries. Challenging the traditional view, the orientation of the lower-Miller-index grain surface, instead of the misorientation, dictates the interfacial structure. We also find partial bipolar structural orders in both amorphous-like and bilayer-like complexions (a.k.a. thermodynamically two-dimensional interfacial phases), which cause brittle intergranular fracture. Such bipolar, yet largely disordered, complexions can exist in and affect the properties of various other materials. Beyond the embrittlement mechanism, this study provides deeper insight to better understand abnormal grain growth in sulfur-doped Ni, and generally enriches our fundamental understanding of performance-limiting and more disordered interfaces.